Ultimate 12" DIY Subwoofer

[Big Daddy]

DRIVERS

I bought two TC Sounds Epic 12" DVC Subwoofer Drivers to be installed in a sealed passive cabinet in a bipolar fashion.

The Epik Dual Legends use similar driver arrangement and they refer to it as "Parallel Drive Technology™"

http://www.epiksubwoofers.com/legend.html

Our new Parallel Drive Technology™ is the driving force behind its performance. We discovered that designing a pair of drivers to specifically replace a single driver can lead to some very large performance increases without an increase in cost, when done right.

The Legend's two drivers have a surface area equivalent to roughly an 18 inch driver. However, we have TWO motors driving the cones in parallel instead of a single motor. Instead of asking one driver to work very hard, we let a pair of driver’s coast through the most torturous of playback materials. Speed, sound quality, explosive dynamics and effortlessness are the name of the game.

Other examples are subwoofers with dual drivers made by Ken Kreisel Sound. They use a "push-pull" design, with the drivers offset in such a manner that one of them faces outward -- like a "normal" driver would -- while the other is wired out of phase and has just its back half exposed.


Before I discuss the DIY subwoofer, I need to make a few general statements:

• We need to distinguish between a subwoofer's output (SPL) and its sound quality. People with a background in car audio tend to be interested mainly in SPL, while people interested in home audio and home theater applications tend to care more about sound quality.
• Our ears are more sensitive to upper bass frequencies than the lower bass frequencies. We generally feel the ultra low bass frequencies. We do not hear them.
• In most averaged-sized rooms, upper bass (mid-bass) is best reproduced when the subwoofer is near the listener.
• The ultra low bass is most efficiently reproduced when the subwoofer is in the corner of the room and not near the listener. See the following diagram.
  
  
  
  
  
  Source: Hsu Research
  
  
• When a subwoofer is placed near the listener, the high direct to reflected sound ratio of nearfield placement helps to reduce room effects, will have excellent headroom (high output with relatively low power because you are sitting next to it), and low distortion.
• A subwoofer driver that is optimized for low bass reproduction is not necessarily the best for mid-bass to upper bass reproduction.
• A driver with a heavy cone material is best for low bass, but this type of driver will have reduced mid to upper bass efficiency.
• A subwoofer driver with a very light cone material, a low inductance voice coil, and a strong magnet will have superior transient response with high efficiency (relatively low power will be needed).
• Also, let us not to ignore the effect of the cabinet on a subwoofer's performance, but that is another story.

Having said all of that, manufacturers specializing in HT equipment do not make large (15" or 18") subwoofer drivers to optimize their mid-bass to upper bass performance. They tend to do that with smaller drivers. We can therefore conclude that as a general rule, large drivers are better in generating ultra low bass frequencies, but they may not be as good in generating the upper bass frequencies. In that respect, 12" drivers are considered to be better than 15" drivers. Additionally, I already have four subwoofers with 15" drivers in my HT room and two 15" subwoofer in my two-channel room.


Relevant TC Sounds Websites:

http://www.tcsounds.com/
http://www.parts-express.com/pe/show...number=293-650

The EPIC 12" subwoofer is designed to be lighter, smaller and ultimately more affordable without deviating from the TC Sounds world-class displacement and low distortion performance guarantee. Matched with just 300 watts, the EPIC will surprise even the most critical audiophiles with substantial, ultra clean low frequency bass, but pair it twice that power and it will take you to the next level! Used by many high-end home audio companies in their best products!

Video on the new Epic Subwoofer Drivers:

http://www.parts-express.com/pe/show...number=293-650

Highlights:

• High-temperature low eddy current stainless steel voicecoil former
• 2 + 2 ohm dual voicecoil
• Light-weight Aluminum wire
• 8" linear spider suspension with large integral lead-wires
• 140 oz. magnet motor structure
• Large 1" symmetrical XBR rubber surround for beyond 2" peak-to-peak travel
• Large anti-flux-modulation shorting ring reduces distortion
• Weight: 24 lbs

Specifications:

• Power handling: 500 watts RMS/ 2,000 watts peak
• Le: 3.2 mH
• Impedance: 2 ohms per coil x 2
• Re: 3.66 ohms
• Frequency range: 15 - 150 Hz
• Fs: 24.0 Hz
• SPL: 86.6 dB
• Vas: 3.22 cu. ft.
• Qms: 7.80
• Qes: 0.42
• Qts: 0.39
• Xmax: 22.9
• Dimensions: Overall diameter 12.60", Cutout diameter 11.05", Depth 6.20"
• Weight: 23.8 lbs.

CABINET

Initially, I planned to build the cabinet myself. After doing some research, I reached the conclusion that it was much easier to buy a well-made cabinet and modify it. The following cabinet from Parts Express meets all the criteria that I was looking for in a quality cabinet. It is made for two Dayton 8-ohm drivers connected in parallel fashion and a Dayton 500- or 900-watt plate amplifier. I decided to buy the better quality TC Sounds drivers and my plan is to build a passive subwoofer using an external stereo amplifier to power each driver with one channel of the external amp. This means that I will have to cover the 10" by 10" cutout on the cabinet for the plate amplifier and possibily modify the cutouts for the drivers.

Dayton Audio SWDC12 Dual 12" Subwoofer Cabinet Gray Vinyl

Is this the ultimate subwoofer box?

Highlights:

• 2.1 cu. ft. sealed cabinet
• True acoustic suspension design
• Opposed side-firing drivers cancel cabinet vibration
• Heavily braced 1" and 2" MDF cabinet wall construction
• Pre-drilled and #10-32 T-nutted driver mounting holes
• 10" x 10" cutout fits popular Dayton Audio plate amplifiers
• Gray vinyl matches modern A/V furniture and accessories
• Weight: 95.00 lbs

Product Detail:

The Dayton Audio SWDC12's overbuilt non-resonant enclosure features 2" MDF speaker baffles, 1" front, rear, top, bottom and dividers, and a full internal "window" brace. A 1" MDF divider isolates the amplifier from the two 12" drivers. Heavy duty, black grill cloth-covered 1" MDF frame speaker grills with imbedded magnets align with driver mounting bolts. The 1-1/4" diameter x 1" tall rubber feet are replaceable with any Dayton Audio spikes with 6 mm threads.

• Dimensions (including bottom trim): 21" H x 27-3/8" W x 17-1/2" D
• Driver cutout: 12.44" for first inch of depth, then 11.125" for the second
• Amp cutout: Fits all Dayton Audio HPSA and SA Series 500 and 1000 watt plate amps
• Amp cutout dimensions: 10" W x 10" H
• Pre-drilled amp mounting holes.

Additional pictures:

The cutouts on the cabinet were for the 8 ohm Dayton Audio RSS315HFA-8 12" Reference HF Drivers. There is also a cutout for a Dayton Audio SPA1000 1000W Subwoofer Plate Amplifier. I decided to buy the better TC Sounds subwoofer drivers. They are slightly bigger than the Dayton drivers and require a bigger cutout. I decided to use two quality 12" inch spacers from RT Mobile Sound System. They make some of the best subwoofer cabinets for cars. I also covered the cutout on the back of the cabinet for the amplifier.

This is the picture of one the TC Sounds drivers attached to the cabinet using the above spacer ring.

The Dayton drivers were meant to be connected in parallel to result in a net impedance of 4 ohms. The single plate amplifier was expected to drive both drivers. The two TC Sound drivers use dual 2 ohm voice coils. I wired each one for an impedance of 4 ohms according to the following diagram. For explanation, refer to the Connecting Dual & Quad Voice Coil Subwoofer Drivers to a Mono Amplifier thread.

Also, Big Daddy does not believe in wussy plate amplifiers. You can ask the former employees of Elemental Designs why plate amplifiers suck. My intention was to use the Upgraded Carver 1.0t Stereo Amplifier to power the two drivers independently. The drivers are not connected to each other. The upgraded amplifier can generate up to 510 watts RMS (1000 watts dynamic) power into a 4 ohm load. Each channel of the amplifier will be used to power each driver. The amplifier was upgraded in Nebraska and its performance has significantly improved.

CarverM-1_0t.jpg






PERFORMANCE AND REVIEW

Cabinet:
This is without a doubt one of the best built subwoofer cabinets. The front and rear baffles of the cabinets are made of 2" MDF wood and the top and bottom are made of 1" MDF wood. It is heavily braced. The cabinet is extremely solid without any vibration. You can actually stand on top it and jump around and it won’t affect a thing. On a scale of one to five, I give it ten stars.

Drivers:
What can I say about TC Sounds drivers that hasn't already been said. They are extremely well made and their performance is as good as it gets.

Build Quality:
I have already discussed the cabinet and the drivers. I made sure the spacers are painted properly and glued to the cabinet tightly. I also added enough polyfill to the cabinet. In addition to dampening the cabinet, polyfill has the effect of making a subwoofer cabinet to appear slightly larger. Because of the spacers and the thick MDF wood used to construct the cabinet, I was able to use relatively long screws to attach the drivers to the cabinet. For all internal connections and connecting the subwoofer to the amplifier, I used 12 gauge speaker wires.

Performance:
This is the only subwoofer in my possession with two drivers. The two 12" drivers are attached in a bipolar fashion and give each other support in the sealed and well damped cabinet. I tried it for both movies and music and it passed both with flying colors. It sounds highly musical and at the same time can scare the entire neighborhood. I have some quality subwoofers in my possession and this is perhaps the best one. I don't believe I have heard a subwoofer at any price level that can outplay this one. Considering that the cost of this subwoofer, including the external amplifier, was below $1,000, it is an amazing deal. I highly recommend this simple DIY option.