DIY Subwoofer Building, Repairing, & Upgrading - Blu-ray Forum

Big Daddy · 12-06-2008, 09:46 PM

The benefits of adding polyfill are also explained in Post #2.
For all the materials needed and important links, go to the end of Post #2.

Also, see the following DIY subwoofers:

Animo's Elemental Designs' Dual 13Av.2 Sealed subwoofer in Post #602.
Big Daddy's 15" Dayton Titanic MKIII driver and a massive subwoofer enclosure built by Elemental Designs in Post #614.
Big Daddy's 12" DIY kit in Post #621.
Big Daddy's upgrade of the Hsu cylinder sub with an Exodus Shiva driver, go to Post # 587.
CoMaToast's folded horn subwoofer in Post #779.
Big Daddy's DIY subwoofer with Dual TC Sounds Epic Drivers

==========================================

HOW I REPAIRED & UPGRADED MY SUBWOOFERS, BUILT A NEW ONE,
AND UPGRADED MY VINTAGE POLK SPEAKERS

Please discuss your DIY subwoofers/speakers and any other enhacements in this thread. If you are planning to build, repair, or upgrade a speaker/subwoofer, you may want to read A Guide to Crossover Networks.

REPAIRING MY SUBWOOFER

Several years ago (1998), my wife and I went to the headquarters of Hsu Research in Anaheim, CA to buy a subwoofer. I had heard nice things about Hsu subwoofers in high-end publications such as Stereophile. I had just purchased two Definitive Technology Super Towers with 15" subwoofers and built-in amplifiers. My main problem was how to best connect and adjust the new subwoofer. Even back then, I knew about the advantages of using multiple subwoofers in a small home theater room.

We were greeted by Dr. Hsu and spent several hours conversing with him and listening to music and movies with some of his latest designed subwoofers. At that time, the top-of-the-line subwoofer made by Hsu Research was HRSW12Va. It was a 12" cylinder-shaped sub that looked absolutely stunning. To make a long story short, we ended up buying two HRSW12Va subwoofers with Walnut top at a total cost of $1,543.50 (in 1998 dollars).

Technical Specifications
Frequency Response: 20Hz - 500Hz
Power Handling: 500watts RMS
Nominal Impedance: 4 Ohms
Sensitivity: 93db @ 1m. 2.83V
Finish: Seamless black knit cloth over cylinder, choice of three top finishes
Size : 23 inches in diameter, 22 inches in height
Weight: 65 lbs.
Feet: Three black anodized aluminum spiked feet.

The subwoofers did not have a built-in amplifier. The external 500 watt amplifiers were $650 each. I decided not to buy the amplifiers as I had already purchased a massive Cinepro amplifier from the manufacturer at a high-end audio/video show in Orange County, CA. The 6 channel Cinepro was capable of providing 750 watts per channel into 4 Ohms, all channels running.

The subwoofers served us well for the past ten years. They worked well together and played bass beautifully for both music and movies. They were not boomy at all. I was so impressed with their performance that I decided to name them Aimie and Suzie. Most of you probably own male subwoofers that are too macho. Ours did not really play bass, they sang it.

Here is a picture of Aimie.

Anyway, a few weeks ago, the unthinkable happened. Aimie decided not to sing anymore. Initially, I thought there was a loose cable or something may have gone wrong with the amplifier. After further testing, I realized that Aimie had departed us. I then realized that I must have killed her a few nights earlier when I played the Dark Side of the Moon SACD so loud that I scared the living daylights out of her.

I became very upset and didn’t know what to do.

The next morning I called Hsu Research. The person on the phone was new and had no information about my subwoofers. I asked him to have Dr. Hsu call me. A few hours later, he called and I explained the situation. He said that he still carries the driver for my sub and it will be around $100. Since I only live about 50 minutes away from their warehouse, I told him that I will come and pick it up the next day.

After I hung up, I decided to go online and get some information about subwoofer drivers. Of course, my favorite site for this kind of information is Parts Express. They are one of the best places in the world for accessories needed for speaker building. After wasting several hours online, I realized that there are many other options available for a 12" driver. It was then that I decided to be courageous and replace the dead driver on my subwoofer with an upgraded model. I figured that you only live once and it is only money. I ordered the Dayton Titanic Mk III for $150 + Shipping. I was told that it will take approximately 5 days for the driver to get to my home. Here is a picture:

After I placed the order, I returned to my home theater room, I disconnected Aimie and decided to play some music and movies without her. It didn’t take me long to realize that Suzie was upset and her bass performance was not what I expected of her. Those of you who are familiar with my threads on subwoofers and standing waves know that the placement of one subwoofer in a home theater room is tricky. I decided to ignore Suzie and wait until the other subwoofer gets repaired. I closed the room and told Suzie that she better learn to behave or I will replace her with a new and improved woman.

The wait was finally over and the new 12" driver arrived. It was pretty heavy. I took it out of the box and set it aside and replaced the subwoofer in about an hour. I connected the wires and played some music and got excited that it was working. For the next several days I played lots of movies and music that contained heavy bass to break in the new driver. I calibrated my speakers again and to my surprise I realized that Suzie actually likes Aimie and cooperates with her. Initially, I had worries about mixing two different types of drivers, but the driver is only a small part of the picture. The enclosure (box) is far more important.

UPGRADING A SUBWOOFER

Several weeks passed and I began to enjoy the new and improved Aimie. Suzie was becoming jealous and was beginning to fight with Aimie.

To make the matters worse, I had caught the upgraditis bug. It was coming to my dreams every night and asking me to upgrade Suzie. I am sure most of you have already caught this bug as it is very contagious. Finally, I succumbed to the bug and decided to go ahead and do what is not good for my bank account.

However, I decided to document everything this time with pictures and guidelines for your benefit.

After spending several days on the Internet searching for subwoofer drivers, I decided to experiment with long throw aluminum woofers. A company I had heard about with good reviews was Peerless (Tymphany). Their subwoofers are designed in Denmark and made in China. Is there anything on this planet that is not made in China? Unfortunately, Parts Express was out of stock. I decided to order the Peerless 830952 (XXLS-308ALU, Long Stroke, 12" Aluminum Cone Woofer, 4 ohm for $222.35+Shipping from Madisound in Wisonsin. Incidentally, Martin Logan's Abyss subwoofer uses a low distortion aluminum-cone driver.

PeerLess1.jpg

Peerless2.JPG

PeerlessXXLS_2.jpg

After waiting a week, the woofer arrived and I got busy. Here is a picture of Suzie in normal position.

This is Suzie upside down. Guys, please no lusting. She belongs to me.

This a picture of Suzie with her organ removed.

This is a picture of Suzie’s inside with poly-fill material. Poly-fill is generally added to dampen the subwoofer’s enclosure. See the benefits of poly-fill in Post #2.

I purchased additional Poly-Fill material from Parts Express. They are $10.80 a pound and rather expensive, but they are the best.

The final step was to use Gasketing Tape around the interior edge of the driver for an airtight attachment to the enclosure.

Finally, the driver was attached to the cabinet. You can use either Phillips Pan Head Screws or Wood Inserts and screws. For large and heavy drivers, Wood Inserts are preferred.

This is the finished subwoofer.

After replacing their drivers and adding more poly-fill to them, the two subwoofers felt as if they had gone through a sex change operation.

They scare me.

I need to change their names to masculine names. A few nights ago, I watched Journey to the Center of the Earth on Blu-ray. Even though the audio was only in Dolby Digital, the bass sound, when the dinosaur arrived, was shaking the foundation of our house. Two thumbs up to Aimie and Suzie.

You think the story ends here. Think twice. Now, Big Daddy is full of confidence and has a spare working 12" driver that he removed from Suzie. What is he going to do with it? Maybe he should build a new 12" subwoofer.

BUILDING A NEW SUBWOOFER

In the next few weeks, I spent a great deal of time researching subwoofer building on the Internet. I realized that the most difficult part of making a subwoofer is the cabinet. You need to have the tools and good carpentry skills.

Speaker Enclosure Material
Speaker enclosures can be made of anything rigid enough to not vibrate and cause distortion. The most common materials are Plywood, Particle board, and MDF (Medium Density Fiberboard). Plywood is more resistant to water, probably the strongest, and lightest. Particle board and MDF are much denser and may have better sonic properties. MDF makes the nicest looking boxes and is easy to work with.

My carpentry skills are good, but I don’t have all the tools, particularly for cutting a nice round circular opening on MDF wood and a square cut for the amplifier. In addition, the cost of making a cabinet and buying the necessary tools would be a lot higher than buying ready-made cabinets. Therefore, I decided to order a ready-made enclosure. After doing an exhaustive search, I limited my choice to three sites.

Subwoofer Enclosures:

Most sites offer subwoofer boxes with two choices of carpets: grey or black. HiFi Sound Connection offers high quality boxes that are painted in black and the prices are very reasonable.
Klaus Audio offers custom made boxes with carpet finishes or plain wood finish that you can paint or stain and varnish. You can order custom made enclosures in different sizes, with choices of Slot or Flared Ports. This is by far the best site for subwoofer enclosures.
The last option is Elemental Designs. They make great subwoofers, but they are not necessarily the most attractive ones. You can order custom subwoofer enclosures from them, but their prices are high.
Ready-made subwoofer kits are also available from Parts Express. They come in different sizes and prices.

I finally decided to order a ready-made vented subwoofer enclosure from HiFi Sound Connection. Since I did not possess the necessary cutting tools, I made the decision that the subwoofer will be a passive one with an external crossover/amplifier. The cabinet I ordered was $64.95 + Shipping. It arrived in less than a week. Immediately, I marked where the driver was going to be installed and drilled very small holes for the installation screws. This is a picture of the empty box.

The first step after drilling the holes was to attach a 15" pair of wires with small Disconnects from the inside to the speaker terminal binding posts. Who came up with this name? You need disconnects to connect something. It does not make much sense.

They are available at the auto department of Wal-Mart or the electrical department of Home Depot/Lowes.

Before doing any additional work, I had to install spikes or legs. I knew from experience that subwoofers need to be moved around for optimum bass sound. I therefore decided to install casters instead of spikes. I was in no mood to carry a heavy subwoofer around.

Next, I covered the inside of the box with Dampening Sheets and filled it loosely with Poly-fill material. You can use 1/2" Acoustic Foam or 1" Acoustic Foam instead.

As I stated before, Poly-fill from Parts Express is excellent, but very expensive. You need two bags and it will cost you over $20. Standard poly-fill material is available at Wal-Mart and most craft and fabric stores. They are a lot cheaper.

The final step was to connect the woofer to the wires with female disconnects and attach it with black screws to the box. To make sure the subwoofer is attached to the enclosure without any air leakage, it is a good idea to put a layer of gasketing tape around the edge of the interior of the subwoofer driver.

This is the finished subwoofer.

I then moved the subwoofer to my two channel room and connected it to the my vintage Polk RTA-15TL speakers. Fortunately, I had an old DBX 300 watt subwoofer amplifier and a HSU Research crossover network that I had purchased with my two HSU subwoofers in 1998.

With the help of an SPL meter and test tones, I calibrated the sound with a crossover frequency around 50Hz. Since the driver was over 10 years old, it did not need a break-in period. With a lot of anxiety I started playing music. It was so much better than before that tears of joy came to my eyes.

A few minutes later my wife walked in from work and asked me if I had bought new speakers. I showed her the finished subwoofer. She was very impressed with the new sound and commented that I should start a subwoofer manufacturing business. Move over Elemental Designs. Big Daddy is in town.

REFURBISHING AND UPGRADING AN OLD AND WORN-OUT SUBWOOFER

In 1989, I bought a DBX 15" down-firing sealed subwoofer. It was a passive sub, but had an internal crossover network set at 120Hz. I also bought an external DBX subwoofer amplifier to drive it. Currently, I am using that amplifier to drive the subwoofer that I built for my two-channel system (see pictures above). The sepcifications of the old subwoofer are listed below.

Specifications
Dimensions: 24" H, 18" W, 18" D
Recommended Power: 20 - 250 Watts
Nominal Impedance: 6.3 Ohms
Sensitivity: 90.5 db
Crossover: Fixed at 120 Hz, 12 db/Octave
Woofer: 15" Polyvinyl Acetate-Coated

I used the subwoofer with two small Infinity satellite speakers in a 2.1 system. After a few years, I bought better speakers and stopped using that system. The subwoofer was mostly in the storage room picking up dust and going to waste. Recently, after I upgraded my Hsu subwoofers and built a new sub, I got the urge to upgrade the old and forgotten monster. The cabinet had minor scratches and a couple of the legs had minor cracks and were a bit loose.

I decided that before I do anything, I should order and buy the material needed to repair the sub. I went to my favorite speaker-building Web site, Parts Express, and ordered a 15" Dayton Titanic MK III woofer, one Subwoofer Terminal Plate, and dampening sheets. I also went to Home Depot and bought 4 casters, several corner brackets, wood repair epoxy putty, and some screws. These are the pictures and the specifications for the Titanic MK III 15" driver:

Specifications of the 15" Titanic MK III:
Frequency range: 19-500 Hz
Power handling: 800 watts RMS/1,100 watts max
Impedance: 4 ohms
Frequency at Resonance (Fs): 24 Hz
Sensitivity: 91.7 dB

I had to wait about 5 days to receive the material I had ordered. This is a pictorial demonstration of how I refurbished and upgraded the subwoofer:

Step 1. I removed the woofer, the speaker terminal, and the crossover that was attached to the terminal.

Step 2. I used the corner brackets to reinforce the old subwoofer’s legs, repaired the cracks with wood epoxy putty, and attached the casters.

Step 3. I widened the speaker terminal opening because the one I had ordered from Parts Express was slightly bigger. Then, I attached the new terminal plate with small screws.

Step 4. I attached the dampening sheets to the inside walls of the cabinet.

Step 5. After attaching two small wires with disconnects to the speaker terminals, I filled the cabinet with poly-fill material.

Step 6. I tested the new woofer to make sure it was not defective, connected the wires from the terminal, and attached it to the cabinet enclosure.

Step 7. I attached my new company’s logo to the subwoofer and placed it in the rear of my home theater room and ran a long RG6 subwoofer cable from my Denon receiver to the location of the new subwoofer. Keep in mind that I already have two modified 12" Hsu subwoofers in that room. In addition, the two Definitive Technology Super Tower front speakers have 15" powered subs inside them. That makes five subwoofers all together. However, only three of them are connected to LFE out. The two built-in Def Tech subwoofers are connected to the front pre-outs.

The crossover and volume control from Pyle Pro controls the subwoofer.

Step 8. To power the subwoofer, I decided to use an external powerful amplifier, not one of those amplifier plates.

Several years ago (1993), I got an exceptional deal on two Carver M-1.0t Amplifiers from a retailer that was going out of business. Currently, I use one of them to drive the two Polk RTA-15TL speakers in my two-channel system. The other one was connected to an old Yamaha receiver to drive two speakers in the family room. I wasn’t using that system very often. I decided to disconnect the amplifier and have the receiver drive the speakers. I figured that the amplifier will get much better use with the new rebuilt subwoofer. According to the Owner’s Manual, the amplifier is rated 1,000 watts RMS into 8 ohms, single channel. My subwoofer is 4 ohms. I am assuming that the amplifier can power the subwoofer up to 2,000 watts RMS, more than enough to create an earthquake in Southern California.

The Moment of Truth
I calibrated my system after I broke in the new subwoofer for several days. This new subwoofer is unbelievable. It is powerful, accurate, musical, thunderous, tight, loud, and damn beautiful (sonic wise). This is by far the best subwoofer that I have ever owned and I have owned many over the years. It rocks.

I know what some of you are thinking. Big Daddy is a bass freak and has gone completely mad.

Let me tell you something. The idea of multiple subwoofers is not about louder SPL. It is all about getting a smooth and even bass across the entire room. My sound system is calibrated perfectly with the help of Audyssey MultEQ and my old reliable Radio Shack digital SPL meter. Every speaker in the room is calibrated perfectly to 75 db. This includes the subwoofers. When I walk around the room with the SPL meter, the bass sound varies between 73 and 78 db. In the main seating area, it is perfectly 75 db for all three seats on the sofa. This is outstanding performance for a dedicated home theater room. Those of you who have one subwoofer should try this. You will notice that the variation across the room is much larger. In fact, there may be locations in your room with terrible bass response.

ANOTHER 15" SUBWOOFER

I built another 15" monster subwoofer for my HT room. I had upgraded an old DBX sealed subwoofer a couple of months ago. Although its performance was good, it did not mix well with the other three ported subs in the HT room. I decided to take the driver out of the that sub and put it in a new ported cabinet.

The driver was the same 15" Dayton Titanic MK III that I had originally purchased a few months ago from Parts Express. See pictures and specifications in Post #1.

I also purchased 5 sheets of 1/2" Acoustic Foam at a cost of $8.97 + shipping per sheet of 18" x 24" and one pound of Poly-Fill material for $10.80 + shipping and standard generic poly-fill from Wal-Mart for $3. I mixed the two.

The cabinet was from HiFi Sound Connection at a cost of $74.95 + shipping.

Cabinet Specifications:
Precision Constructed with 3/4" MDF
Black coating: Seven Sprayed on layers for a long lasting, durable, water resistant enclosure (same technology as spray-on bed liner)
Includes Built-In Terminal Cup(s)
Slot Ported Enclosure
Width: 21", Height: 16", Depth: 18"

First, I marked and drilled small holes for the driver, and covered the inside of the box with dampening foam and filled it loosely with Poly-fill material. I also connected a set of speaker wires to the inside of the speaker terminal binding posts.

Next, I used Gasketing Tape around the interior edge of the driver for an airtight attachment to the enclosure.

The final step was to connect the wires to the driver and use Wood Insert Nuts from Professional Hardware & Supply Co. to attach the driver to the cabinet. Wood inserts work better than regular screws for large and heavy drivers.

This is the finished subwoofer.

I placed it on the new sub riser that I had recently built.

I used the same Pyle Pro external crossover and Carver amplifier as described earlier.

I now have enough subwoofers for every room in the house, including the bathrooms. My wife says that our house is fully SUBWOOFERIZED. I don't agree. I think I should build an 18" or 21" before I fully retire from subwoofer building.

MATERIALS NEEDED AND LINKS

Continued in the next post.

Big Daddy · 12-06-2008, 09:47 PM

BENEFITS OF POLYFILL

Polyfill can deepen bass, tone down any unwanted reverberation, improve the dynamic extension, and will give you tighter and more accurate bass. It also helps to give a flatter frequency response to the overall sound. Besides this, it also helps reduce the vibration of the box, which results in less distortion and tricks a subwoofer into thinking it is in a bigger box. Damping also increases subwoofer efficiency.

It is a good idea to use sheet dampening material to cover the entire inner surface of the cabinet. A small amount of glue may help. The loose polyfill is good for filling the cabinet. The type of subwoofer (down-firing or front-firing) does not play a role.

Polyfill can have several positive effects:

It will dampen the cabinet.
You will hear less noise, particularly the noise associated with the flow of air through the port.
It will slow down the sound waves and makes the enclosure appear larger. When polyfill is added to an enclosure, it changes the behavior of the airflow in the enclosure from "adiabatic" to "isothermal". The term "adiabatic" means that there is no heat transfer occurring. An isothermal process means that as the air passes through the polyfill, the fibers wiggle and cause some of the energy created by the air to be dissipated as heat. This heats the surrounding air molecules warmer, causing the air to become less dense. Sound waves travel easier through a denser medium. As a result, the driver interacts with the enclosure as if it is larger than it actually is.
Larger cabinets are more efficient and as a result low frequency extension of the sub will be lowered. It will also lower the resonant frequency of the port.

Adding polyfill to an enclosure is a good idea. However, too much polyfill can be a bad thing. At a certain point, the stuffing becomes too dense and the fibers no longer wiggle. At this point, not only have you taken away the size benefit of adding polyfill, you have actually decreased the effective volume as the polyfill is now taking up room inside your enclosure. You should add anywhere between 1/2 pound to one pound of polyfill to one cubic feet of enclosure.

The following diagram from Basic Car Audio demonstrates the effect of polyfill on the frequency response of a subwoofer.

Quote:

Poly-fill can be used to make an enclosure seem slightly larger. It does this by slowing the movement of the air in the enclosure. This, in effect, smoothes the frequency response of the subwoofer's output and slightly improves its low frequency extension. This image shows, to what degree, it does both. The red line (no fill) has a slightly higher peak than the yellow line before it starts to roll off. The yellow line has a slightly improved low frequency extension when compared to the red line. The effect is not very dramatic but using poly-fill in this manner can sometimes make a subwoofer sound better. The red curve is has no poly-fill. The yellow line is 100% filled with poly-fill. 100% fill is equal to 1 pound of poly-fill per cubic foot of air space.

As was stated before, polyfill can make a subwoofer appear larger. As a result, it will extend the ultra low frequencies of the subwoofer and will flatten the frequency response curve. However, the mid to upper frequency output may drop. Take a look at the following diagram. The 3 frequency response curves are the predicted response from a single woofer in 3 different size enclosures. As you can see, the red curve (largest enclosure) has the best low frequency extension and slightly less output in the mid to upper bass frequencies, the violet curve (medium size enclosure) has the flattest frequency response for the widest range of frequencies, and the green curve (smallest enclosure) shows a slight boost to some frequencies but rolls off earlier than the other curves.

It is important to remember that human ears are more sensitive to the middle and upper bass frequencies. Moreover, most SPL meters are less accurate in reading the lower bass frequencies.

Red Curve: Enclosure volume = 4.68 cubic ft
Violet Curve: Enclosure volume = 2.68 cubic ft
Green Curve: Enclosure volume = 1.77 cubic ft
Source: http://www.bcae1.com/

Port Tuning
A woofer needs to be controlled after it has finished playing certain frequencies. It generally relies partly on its own suspension and partly on the damping provided by the enclosure. If there is insufficient damping, the woofer’s cone will move significantly more than it should. The ported box will provide virtually no damping below the port frequency (all of the control will be provided by the woofer’s suspension). Below the port tuning frequency, it is possible to cause damage to the woofer well before power levels approach the maximum power ratings of the woofer.

Port tuning is not very complicated. The builder decides what the tuning should be, based on the type of applications (HT, music, or car) that the subwoofer is made for. A subwoofer for car audio is tuned high (30Hz-50Hz) because most car audio enthusiasts love loud SPL and also additional gain is provided the small space inside the car. Music subwoofers are tuned in the 25Hz to 35Hz range, and HT subwoofers are tuned below 25Hz. The tuned frequency of the port, usually a length of PVC pipe, depends on the two port parameters of area and length for a given enclosure/woofer combination.

By adding a port, the rear wave of the cone motion is used to reinforce the front wave. This typically results in a system with a higher efficiency (it plays louder with less power). The disadvantages of this design are lower power handling and poor response below the port tuning frequency.

At frequencies above the port tuning frequency, cone excursion will be very well controlled, and will actually be lower than that of a sealed enclosure, but at frequencies below the port tuning, as there is no internal box pressure to control excursion, the driver can easily reach its excursion limit with very little power. This is not a big issue with tuning frequencies down in the 20-25Hz range, because most content do not go that low. However, if the tuning is in the 35-40Hz or higher range, you will have the potential for significant content to be below your tuning. Cone excursion below the tuning frequency in a ported enclosure is very high, and can easily cause damage to the driver if it is not controlled. At frequencies below the tuning frequency of the port, a woofer starts to de-couple. This means that the controlling function of the enclosure begins to disappear. The collapse is gradual rather than immediate, but at some point below the tuning of the port, the speaker behaves as if it were operating without an enclosure and suffers from potentially damaging over-excursion. This is why it is a good practice to use a subsonic filter when running a ported enclosure. Some subwoofer amplifiers come with a subsonic filter, which block these lowest frequencies.

More information on port tuning can be found in Post #3 of A Guide to Subwoofers (Part II).

What happens if the box is too small?
If the box is too small, the bass will be slightly boomy with strong mid-bass and less low bass. Typically, power-handling is improved if the box is not too small. You can compensate somewhat for a small box volume by adding polyfill to the box. The stuffing can make the box appear up to 40% larger to the driver and will lower the tuned frequency.

A slightly lower tuning frequency will add a little more safety due to the driver not unloading below tuning frequency as soon. Polyfill provides this additional safety.

What happens if the box is too large?
Typically the low frequency extension of the system improves a little, at the expense of power handling. If the ported subwoofer is too large, there will be a response peak around the resonance frequency of the system that can easily be corrected with an equalizer.

As was stated earlier, polyfill has these three main effects on a subwoofer box:

It dampen the box and reduces the effect of back waves.
It makes the enclosure appear to be larger than it actually is.
It slightly lowers the tuning frequency of the ported subwoofer.

Pollyfill is a sound absorption dampening fiber that may deepen the sound and tone down any unwanted reverberation of any subwoofer. Contrary to all the nonsense that is repeated in most Internet forums, we do not have standing waves in a subwoofer box, particularly in HT applications. Assuming that the vast majority of subwoofers for home audio are crossed at 80Hz to 100Hz, you can imagine the stupidity of this claim. These are the approximate wavelengths of bass frequencies:

20Hz: 56.5ft
50Hz: 22.6ft
80Hz: 14.1ft
100Hz: 11.3ft

For standing waves to occur, we need a subwoofer that is the size of a room. How many of you have a subwoofer that big?

Polyfill affects both sealed and ported subwoofer boxes. As a general rule, polyfill has more benefit for small boxes and since most sealed boxes are smaller than ported boxes, it appears that sealed boxes are affected more.

In car audio, most people play bass-heavy music at loud volumes and the subwoofers are tuned at a higher frequency for maximum SPL. They are more concerned about loudness.

In home audio, most people care about the quality of audio for HT and music applications. Most HT subwoofers are tuned lower for better low frequency extension.

This is from Ultimate Polyfill Subwoofer Enclosure Resource

Quote:

To evaluate the effectiveness of box stuffing, I used an MLSSA analyzer to measure the impedance of three enclosures 5.l-cubic-foot sealed, 1.4-cubic-foot sealed, and 1.4-cubic-foot ported (the port measured 3 inches in diameter and 6 inches in length) with various densities of stuffing. For the sealed boxes, I was able to determine the effective box size as enhanced by the stuffing using the system's resonant-frequency and Qes values. For the ported box, I compared the tuned frequency of the empty enclosure to the tuned frequency of the stuffed enclosure, using the Speak for Windows computer program; this enabled me to find the effective box size that fit the actual resonant frequency I'd measured.

Sealed Box (1.4 cubic ft ):

Sealed Box (5.1 cubic ft):

Ported Box (1.4 cubic ft):

Usually about 1/2 pound to a maximum of one pound of polyfill per one cubic ft is enough. Over-stuffing a subwoofer box may have a negative effect. Some people suggest that you experiment with the amount of polyfill until you get the desired effect.

It is a good idea to staple or glue a thin layer of polyfill to all the interior panels of the subwoofer box and add sufficient amount of loose polyfill to the box. Remember that if you put too much loose polyfill inside a ported subwoofer, it may lower the sound quality and the polyfill may blow out of the port.

Although fiberglass can also be used, I do not recommend it as it can become a health hazard.

Polyfill can also have a positive effect on regular speakers. Speakers are more subject to back standing waves as the drivers generate much higher frequencies (lower wavelengths).

Passive Radiators:
Passive radiators are used instead of ports. I suppose that makes them a separate category or a sub category of ported subs. A brief description of passive radiators is given in the following.

Passive radiators (PR) are used as an alternative to ported designs to extend the low frequency of the subwoofer. The frequency response of a subwoofer with a PR is similar to the frequency response of a ported subwoofer, but the -3dB low frequency is slightly higher and the cutoff slope is steeper.

A passive radiator is essentially a weight consisting of the cone material and the extra mass that may be used. The spring is a combination of the stiffness of the suspension materials and mostly the air trapped inside the cabinet. Think of a PR as basically a subwoofer driver without the magnet or coil assembly. It will have a means whereby additional mass can be added, usually by adding weigths to a threaded rod in the middle of the cone.

Like all other drivers, a PR has a resonant frequency, which can decrease or increase by adding or subtracting mass. At resonant frequency, there is usually a dip in output. Below resonance, the output drops even more and the driver becomes unloaded faster than a ported subwoofer.

To avoid over-excursion of the passive radiator, it is normally recommended that the displacement of the PR to be twice that of the driver. That is why, for a 12" driver two 12" PR's with the same displacement or one larger PR with more displacement is recommended.

Advantages:

No port noise
To achieve low frequency tuning in a ported design, you need a long port tube that makes the subwoofer too big or the design too difficult. With a PR, low tuning can be achieved in a small box by adding weight to the PR.

Disadvantages:

PR subwoofers are more costly.
A PR system has a faster rolloff and may unload faster below the resonance point.
Transient response is worse than a ported cabinet particularly below the tuning frequency.

MATERIALS NEEDED AND IMPORTANT LINKS

ADDITIONAL LINKS FOR SPEAKER KITS, PARTS, REPAIRS, AND UPGRADES

Additional Parts
http://www.speakerrepair.com/mm5/merchant.mvc
http://www.reliablehardware.com/
http://www.newfoam.com/wood.asp

Subwoofer Terminology
http://en.wikipedia.org/wiki/Thiele/Small
http://www.the12volt.com/caraudio/thiele.asp
http://www.iroczone.com/2009/10/how-to-buy-a-subwoofer/
http://sound.westhost.com/tsp.htm
http://www.members.shaw.ca/LoudSpeak...ele-small.html
http://forums.audioholics.com/forums...ad.php?t=37001
http://www.bcae1.com/speaker.htm
http://www.diyaudioandvideo.com/Basic/Terms/

Subwoofer Making
Subwoofer Design Theories:
http://www.danmarx.org/audioinnovation/theories.html
Subwoofer Cabinet Dimensions Calculator:
http://www.carstereo.com/help2/Articles.cfm?id=5
Enclosure Volume Calculator:
http://www.hometheatershack.com/foru...me-calculator/
Driver Wiring Diagram:
http://www.hometheatershack.com/foru...ring-diagrams/
Vent Dimensions Calculator:
http://www.psp-inc.com/tools.html
http://www.the12volt.com/caraudio/boxcalcs.asp
http://www.carstereo.com/help2/Articles.cfm?id=31
http://www.icixsound.com/vb/showthread.php?t=39744
Additional Information:
http://www.ajdesigner.com/phpsubwoof...y_equation.php
http://www.the12volt.com/caraudio/boxcalcs.asp#por
http://www.iroczone.com/technical/Subwoofer/
http://spkrbox1.spaces.live.com/
http://www.diysubwoofers.org/faq.htm
http://www.ajdesigner.com/phpsubwoof...y_equation.php
http://www.carstereo.com/help/Articles.cfm
DIY Projects:
http://diyaudioprojects.com/Speakers/MAW-10/MAW-10.htm
http://diyaudioprojects.com/Speakers...DIY-Subwoofer/
http://www.geocities.com/adrian_mack/
http://projectcube2007.blogspot.com/
http://www.truckinweb.com/tech/elect.../photo_01.html
http://www.hometheaterhifi.com/volum...tember-99.html
http://www.hometheaterhifi.com/volum...ferjune98.html
http://www.diysubwoofers.org/
http://forum.edesignaudio.com/showth...res-58486.html
http://www.speakerplans.com/index.php?id=home

Infinite Baffle Subwoofers:
http://www.audiogearreviews.com/tech...ite_baffle.asp
http://ibsubwoofer.blogspot.com/index.html

THT Cabinets:
http://billfitzmaurice.net/THT.html

Subwoofer Wiring Diagrams:
http://www.crutchfield.com/S-lHlo2lW...rs_wiring.html
http://www.hometheatershack.com/foru...ring-diagrams/
http://www.the12volt.com/caraudio/wo...s.asp?Q=1&I=22

Parts, Repairs, and Upgrades
http://meniscusaudio.com/index.php
http://www.parts-express.com
http://www.speakerrepair.com/mm5/merchant.mvc
http://www.reliablehardware.com/
http://www.newfoam.com/wood.asp
Resetting Loose Driver Magnets: http://www.audiokarma.org/forums/sho...d.php?t=202963
Dave Schulte, Upgrade Company: http://upgradecompany.com/
Vintage Audio Repair: http://www.oldsoundequipment.com/index.html
http://www.solen.ca/pub/index.php?q=...50cmVyPSZpPTQ=
http://www.speakerex.com/
http://www.simplyspeakers.com/
http://www.speakercity.com/Merchant2/merchant.mvc?
http://www.madisound.com/
http://www.oaktreeent.com/Polk-Audio_Speaker_Parts.htm
http://www.speakerdoctor.com/diaphragms.html
http://www.lab-acoustics.com/shop/?cart=171309&cat=1&
http://www.mcmelectronics.com/
http://www.e-speakers.com/
http://www.onlyfactorydirect.net/
Active & Passive Crossovers: http://www.marchandelec.com/index.html

GotToyota? · 12-07-2008, 05:19 AM

Can you add polyfill to a subwoofer that's already ok? I remember doing this to my small subwoofer that I had in my car, which improved sound drastically. I would also probably add them in with my bookshelf speakers as well.

-Matt

JasonR · 12-07-2008, 05:27 AM

BigDaddy,

So, if I considered building a sub using a car audio JL 12w6, that would be okay right?

Oh, and great work BTW!!!

Big Daddy · 12-07-2008, 05:48 AM

Quote:

Originally Posted by GotToyota?

Can you add polyfill to a subwoofer that's already ok? I remember doing this to my small subwoofer that I had in my car, which improved sound drastically. I would also probably add them in with my bookshelf speakers as well.

-Matt

Yes, but don't over fill the sub. Adding dampening material to a sub improves the sound. To the best of my knowledge, there are no down side, except a few dollars.

Quote:

Originally Posted by JasonR

BigDaddy,

So, if I considered to build a sub using a car audio JL 12w6 that would be okay right?

Oh, and great work BTW!!!

Thanks for the compliment. I have been busy the past few months exhausting our bank account. The answer to your question is yes. Make sure you dampen it properly and use the gasketing tape so that there are no leakages.

Incidentally, do you like the looks of my Hsu subs? I don't like the cubic subs as much. Unfortunately, Hsu Research does not make them anymore.

JasonR · 12-07-2008, 05:56 AM

Love the HSU subs, VERY aesthetically pleasing! A lot more than I can say for my eD!

I think I might have some JL subs laying around is why I ask. They were pretty expenive new, so if I could put them to use that would be nice! Can you recommend a good amp to drive one of them?

Big Daddy · 12-07-2008, 06:01 AM

Quote:

Originally Posted by JasonR

Love the HSU subs, VERY aesthetically pleasing! A lot more than I can say for my eD!

I think I might have some JL subs laying around is why I ask. They were pretty expenive new, so if I could put them to use that would be nice! Can you recommend a good amp to drive one of them?

ED subs are powerful, but they do not appeal to women.

I assume your JL sub is a passive sub. The choices from Parts Express are the best. You really don't need anything more powerful than 150 watts. They have one at a special price of $130. Look at the links in the original post.

Blu_Ray_Fan · 12-07-2008, 06:03 AM

Very nice post! You got me thinking of adding a couple homemade subs to my HT. Hell, at those prices I can sell them if I don't like the results. Great post!

JasonR · 12-07-2008, 06:07 AM

Quote:

Originally Posted by Big Daddy

ED subs are powerful, but they do not appeal to women.

I assume your JL sub is a passive sub. The choices from Parts Express are the best. You really don't need anything more powerful than 150 watts. Look at the links in the original post.

Thank you, I will look at Parts Express! Yeah, the wife is always trying to set pretties on the sub to dress it up. Guess she thinks it is a coffee table.

prerich · 12-07-2008, 06:21 AM

Big Daddy - that's a project after my own heart

I love vintage gear - I think its some of the best out there given the chance. Great Job!!!! I've actually used car subs in very large inclosure to make passive subs (made me give up my Powerfield 15 back in 1996 and I haven't turned back). I'm using a Sony TA-N80ES for an amp and a paradigm x-30 for an active crossover.

Big Daddy · 12-07-2008, 06:21 AM

Quote:

Originally Posted by JasonR

Thank you, I will look at Parts Express! Yeah, the wife is always trying to set pretties on the sub to dress it up. Guess she thinks it is a coffee table.

Many of our guests think that our subwoofers are coffee tables.

Quote:

Originally Posted by Blu_Ray_Fan

Very nice post! You got me thinking of adding a couple homemade subs to my HT. Hell, at those prices I can sell them if I don't like the results. Great post!

Thanks. The price is not as important. The satisfaction is far greater. It is your creation. It feels like your baby.

Big Daddy · 12-07-2008, 06:25 AM

Quote:

Originally Posted by prerich

Big Daddy - that's a project after my own heart

I love vintage gear - I think its some of the best out there given the chance. Great Job!!!! I've actually used car subs in very large inclosure to make passive subs (made me give up my Powerfield 15 back in 1996 and I haven't turned back). I'm using a Sony TA-N80ES for an amp and a paradigm x-30 for an active crossover.

I have an old 15" passive DBX subwoofer that I purchased in 1988-1989. It is massive. It is sitting unused in the corner of my storage room picking up dust. It smiles at me everytime I enter that room. It knows something is in the air.

JasonR · 12-07-2008, 06:27 AM

Quote:

Originally Posted by Big Daddy

Many of our guests think that our subwoofers are coffee tables.

Make sure coasters are handy!

Blu_Ray_Fan · 12-07-2008, 06:38 AM

Quote:

Originally Posted by Big Daddy

Thanks. The price is not as important. The satisfaction is far greater. It is your creation. It feels like your baby.

Yea, your right.

Question. If I was going to add 2 12" subs and use them in stereo in a 5.1 setup for extra oomph for my front L/R, which amp would you rec? Should I just get the Dayton APA150 which would provide 75 watts to each? Keep in mind they will only be up there temporarly as I am saving for a set of Def Tech 7002's to replace my BP6's. At that point I would move them to the rear to complete my rear sounstage and compliment my BPx2's.

Check sig/HT gallery for set-up.

Big Daddy · 12-07-2008, 06:43 AM

Quote:

Originally Posted by JasonR

Make sure coasters are handy!

We don't need coasters. I'll shoot them before they put their coffee cups on the subs.

Quote:

Originally Posted by Blu_Ray_Fan

Yea, your right.

Question. If I was going to add 2 12" subs and use them in stereo in a 5.1 setup for extra oomph for my front L/R, which amp would you rec? Should I just get the Dayton APA150 which would provide 75 watts to each? Keep in mind they will only be up there temporarly as I am saving for a set of Def Tech 7002's to replace my BP6's. At that point I would move them to the rear to complete my rear sounstage and compliment my BPx2's.

Check sig/HT gallery for set-up.

Generally, I do not recommend 2 subs in a box. I realize that people do this in their cars, but cars have space limitations. It is always better to have bass sound coming from two different locations. This is because of the existence of standing waves in a small home theater room. Using two smaller subs instead of a dual sub will always work better. If you haven't already read the thread, read A Guide to Subwoofers (Part II): Standing Waves and Room Modes..

Edit: 75 watt amplifiers should work, but subwoofers love power. Most subwoofer drivers are rated 4 ohm. If an amplifier's power is rated 75 watts for 8 ohm speakers, it should be able to provide up to 150 watts to 4 ohm drivers.

Blu_Ray_Fan · 12-07-2008, 06:58 AM

Sorry, I didn't make myself clear. I would install these 2 subs in seperate boxes, just wondering if that amp would be ok for what I'm tryin to do. Remember, I have a Super Cube 1 to handle the LFE.

So would this be ok, or would something else work better for me IYHO?

http://www.parts-express.com/pe/show...number=300-812
http://www.parts-express.com/pe/show...number=295-404

Or would something like this work better?
http://www.amazon.com/Pyle-PTA1000-1000W-Professional-Amplifier/dp/B0010K6TXQ/ref=sr_1_22?ie=UTF8&s=electronics&qid=1228635894&s r=1-22

Thanks.

Blu_Ray_Fan · 12-07-2008, 07:14 AM

After looking around, I think this would be a better choice??

I wanted to ask you, Are those super tweeters worth it for HT, or just 2 channel audio only apps?

Big Daddy · 12-07-2008, 07:22 AM

Quote:

Originally Posted by Blu_Ray_Fan

Sorry, I didn't make myself clear. I would install these 2 subs in seperate boxes, just wondering if that amp would be ok for what I'm tryin to do. Remember, I have a Super Cube 1 to handle the LFE.

So would this be ok, or would something else work better for me IYHO?

http://www.parts-express.com/pe/show...number=300-812
http://www.parts-express.com/pe/show...number=295-404

Or would something like this work better?
http://www.amazon.com/Pyle-PTA1000-1000W-Professional-Amplifier/dp/B0010K6TXQ/ref=sr_1_22?ie=UTF8&s=electronics&qid=1228635894&s r=1-22

Thanks.

The Pyle amplifier is a pro amplifier for clubs and DJs. They are not as refined as home theater amps. Some of them have a cooling fan that are very noisy. That 1,000 watt is an exaggerated number. It probably cannot output more than a total of a couple of hundred watts.

The first amp is a dedicated subwoofer amp with a built-in crossover. It is band limited and only operates at low frequencies. 75 Watts for 2 subs or 150 watts for one isn't bad. If I were in your position, I would go for the dedicated subwoofer amp.

Blu_Ray_Fan · 12-07-2008, 07:24 AM

I agree. Thanks for the advise.

Big Daddy · 12-07-2008, 07:31 AM

Quote:

Originally Posted by Blu_Ray_Fan

After looking around, I think this would be a better choice??

I wanted to ask you, Are those super tweeters worth it for HT, or just 2 channel audio only apps?

That choice for a sub amp is for powered subwoofers. You need to cut a square opening to fit the amplifier. Make sure you have the tools. Most ready-made subwoofer boxes only have a round opening for the driver. It is up to you to cut the box.

Super tweeters can work with any pair of 2 channel or HT speakers (usually front speakers). Obviously, you hear their benefit a lot more when you are listening to two channel music.

12-07-2008, 05:27 AM	#4
JasonR Super Moderator Top contributor Member since:Nov 2007 Trading Score:12	BigDaddy, So, if I considered building a sub using a car audio JL 12w6, that would be okay right? Oh, and great work BTW!!! Last edited by JasonR; 12-07-2008 at 05:45 AM.

12-07-2008, 07:14 AM	#17
Blu_Ray_Fan Senior Member Member since:Mar 2008 Home Theater Gallery:20 Blu-ray collection:104 Blu-ray reviews:1	After looking around, I think this would be a better choice?? I wanted to ask you, Are those super tweeters worth it for HT, or just 2 channel audio only apps? Last edited by Big Daddy; 12-07-2008 at 08:15 AM.

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12-07-2008, 05:19 AM	#3
GotToyota? Senior Member Member since:Jan 2008 Blu-ray collection:19 Trading Score:29	Can you add polyfill to a subwoofer that's already ok? I remember doing this to my small subwoofer that I had in my car, which improved sound drastically. I would also probably add them in with my bookshelf speakers as well. -Matt

12-07-2008, 05:56 AM	#6
JasonR Super Moderator Top contributor Member since:Nov 2007 Trading Score:12	Love the HSU subs, VERY aesthetically pleasing! A lot more than I can say for my eD! I think I might have some JL subs laying around is why I ask. They were pretty expenive new, so if I could put them to use that would be nice! Can you recommend a good amp to drive one of them?

12-07-2008, 06:03 AM	#8
Blu_Ray_Fan Senior Member Member since:Mar 2008 Home Theater Gallery:20 Blu-ray collection:104 Blu-ray reviews:1	Very nice post! You got me thinking of adding a couple homemade subs to my HT. Hell, at those prices I can sell them if I don't like the results. Great post!

12-07-2008, 06:21 AM	#10
prerich Moderator Top ranked HT gallery Top contributor Member since:Dec 2007 Home Theater Gallery:46 Blu-ray reviews:1 Trading Score:2	Big Daddy - that's a project after my own heart I love vintage gear - I think its some of the best out there given the chance. Great Job!!!! I've actually used car subs in very large inclosure to make passive subs (made me give up my Powerfield 15 back in 1996 and I haven't turned back). I'm using a Sony TA-N80ES for an amp and a paradigm x-30 for an active crossover.

12-07-2008, 06:58 AM	#16
Blu_Ray_Fan Senior Member Member since:Mar 2008 Home Theater Gallery:20 Blu-ray collection:104 Blu-ray reviews:1	Sorry, I didn't make myself clear. I would install these 2 subs in seperate boxes, just wondering if that amp would be ok for what I'm tryin to do. Remember, I have a Super Cube 1 to handle the LFE. So would this be ok, or would something else work better for me IYHO? http://www.parts-express.com/pe/show...number=300-812 http://www.parts-express.com/pe/show...number=295-404 Or would something like this work better? http://www.amazon.com/Pyle-PTA1000-1000W-Professional-Amplifier/dp/B0010K6TXQ/ref=sr_1_22?ie=UTF8&s=electronics&qid=1228635894&s r=1-22 Thanks.

12-07-2008, 07:24 AM	#19
Blu_Ray_Fan Senior Member Member since:Mar 2008 Home Theater Gallery:20 Blu-ray collection:104 Blu-ray reviews:1	I agree. Thanks for the advise.

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