DIY Subwoofer Risers

[StimpsonJCat]

Originally Posted by aramis109

Ugh, that article went right over my head. Lemme just ask is there a free calibration disc out there that will do better than the receiver test tones? I'm running Audyssey first and then going back and checking and tweaking with the SPL. I have been very pleased with the results overall, but don't want to continue to sink money in to tweaking discs, and SPL's and all of that.


*edit* Wait, I have a DVE on dvd. I guess I never looked since it's been tucked away for forever, but does it have test tones and such on it?

You can use the free download from real traps:
http://www.realtraps.com/test-cd.htm

I have the DVE disc and it does have test tones, but I think the one from real traps is setup better to go through all the frequencies you want to use.

Also, there is free software that can be used for this instead of plotting measurements by hand. It is called REW . You need the proper sound card and a computer that can be moved to the HT room (or really long cords). This is probably the best way to see what is going on in your room for the subwoofer.

[jomari]

Originally Posted by aramis109

Ugh, that article went right over my head...

you would get into it after a couple of readings. what it basically says is that white noise isnt as good as pink noise, because pink noise has the entire frequency and not limited like white noise.

Originally Posted by aramis109

Lemme just ask is there a free calibration disc out there that will do better than the receiver test tones? ... and SPL's and all of that.

*edit* Wait, I have a DVE on dvd. I guess I never looked since it's been tucked away for forever, but does it have test tones and such on it?

you can certainly use the DVE, or any movie that has a THX optimizer. you dont have a spl meter yet? id suggest to seriously look into getting it. its probably the second (against my mopads) best investment ive had in the business.

you can also use the free tones off the web, there are dozens of em. but for now, just use those present in your pre-existing dvds you might have.

GTG for now, doctors appointment.

*edit, forgot to mention, you already HAVE a spl meter right?

dont forget you have to point the spl meter UP TOWARDS THE CEILING and NOT TOWARDS THE SPEAKERS. first big mistake people make using it.

oh, and use a tripod. no use in having your head affecting the measurements.

[aramis109]

Originally Posted by jomari

you would get into it after a couple of readings. what it basically says is that white noise isnt as good as pink noise, because pink noise has the entire frequency and not limited like white noise.



you can certainly use the DVE, or any movie that has a THX optimizer. you dont have a spl meter yet? id suggest to seriously look into getting it. its probably the second (against my mopads) best investment ive had in the business.

you can also use the free tones off the web, there are dozens of em. but for now, just use those present in your pre-existing dvds you might have.

GTG for now, doctors appointment.

*edit, forgot to mention, you already HAVE a spl meter right?

dont forget you have to point the spl meter UP TOWARDS THE CEILING and NOT TOWARDS THE SPEAKERS. first big mistake people make using it.

oh, and use a tripod. no use in having your head affecting the measurements.

My post wasn't clear. I DO have an SPL. It's new, so outside of calibrating the speakers I'm not very familiar with its use yet. I typically hold the SPL in front and to the side of me as there's not a super place to set it down, but I angle it about 45 degrees/towards the ceiling.

I do have a mini-tripod. Maybe I can rig something up with it mounted on a broom handle and wedge that in the couch approximately head/listening level. I'll try that and digging out the DVE disc when I get home tonight. In the past I only used it for video.

[Big Daddy]

Originally Posted by jomari

hmm. thats the problem with built in test tones.
1. not having the full bandwidth pink noise to assist in setting up your subwoofer.
2. most receivers use white noise instead of pink noise.

To the best of my knowledge, most receivers use PINK NOISE. Did you mean something else?

Originally Posted by aramis109

In the meantime I did break out my SPL meter. Now, when I run the test tones through the sub, I still have my SPL meter set at 80, slow response and C weighting. When I do that, I see fluctuations at my seating point from 74-77db. I assume this is because I have some standing waves/some other type of issue? Either way it basically read the same with and without the riser. Should I perhaps be setting the SPL to a lower setting? I tried them and it was never a stable number.

That is quite normal. Even if you move a couple of inches, the reading may change. It is the nature of long wavelength bass frequencies. They like your room walls too much.

When you use the pink noise from your receiver to adjust the subwoofer level, you will not get accurate results. The main reason is that your calibration program or the SPL meter (if you are using one) measure the peak frequency generated by the sub at that listening position and all other frequencies are obscured. This is why it is best to use test tones and an SPL meter for a subwoofer calibration.

How to Adjust Your Subwoofer:
Using a test tone disc, adjust the volume so that the SPL meter reads 75dB with a 50Hz tone at the listening position. Take measurements of four different tones 1/3 octave above the crossover point and four different tones 1/3 octave below the crossover point. Average together each set of four measurements and adjust the subwoofer’s volume level to match the other speakers.

Free Test Tones:
http://www.realtraps.com/test-cd.htm
http://www.cleansofts.com/softdownlo...Generator.html
http://www.nch.com.au/tonegen/index_b.html

Rives Audio Test Tones ($21):
http://www.rivesaudio.com/order/orderframe.html

Check these threads:
Calibrating Your Audio With an SPL Meter.
Calibrating Your Subwoofer(s) with the Velodyne SMS-1 Equalizer/Analyser.

Dfinitions:
White noise has the same distribution of power for all frequencies, so there is the same amount of power between 0 and 500Hz, 500Hz and 1,000Hz or 20,000Hz and 20,500Hz.

Pink noise has the same distribution of power for each octave, so the power between 0.5Hz and 1Hz is the same as between 5,000Hz and 10,000Hz.

Octave: assume one note has a frequency of 200Hz, the note an octave above it is at 400Hz, and the note an octave below is at 100Hz. The ratio of frequencies of two octaves is 2:1. Another examlple: 50Hz is one octave below 100Hz, and 400Hz is two octaves above 100Hz.

Depending on the crossover frequency (low pass filter frequency), these are the 1/3 octave apart frequencies that you need to calibrate your subwoofer(s): 20Hz, 25Hz, 31.5Hz, 40Hz, 50Hz, 63Hz, 80Hz, 100Hz, 125Hz, 160Hz, 200Hz, 250Hz, 315Hz.

[jomari]

Originally Posted by Big Daddy

To the best of my knowledge, most receivers use PINK NOISE. Did you mean something else?

I stand corrected. currently under the weather nursing a flu, so im not quite sure why i posted that.

anyhoo, does receivers have full bandwidth pink noise, or limited bandwidth?

down for the count on this one.

apologies for the confusion.

[Big Daddy]

Originally Posted by jomari

I stand corrected. currently under the weather nursing a flu, so im not quite sure why i posted that.

anyhoo, does receivers have full bandwidth pink noise, or limited bandwidth?

down for the count on this one.

apologies for the confusion.

Did you give me the virus? I have a sore throat and fever too. Let's blame it on the Clam Chowder you had a week ago.

[erict]

You guys didn't share a spoon, did you

[Big Daddy]

Originally Posted by erict

You guys didn't share a spoon, did you

He lives in Northern California. I live in Southern California. He must have sent the virus to me with UPS. I am surprised UPS didn't drop the package and damage it.

[crazyBLUE]

Originally Posted by Big Daddy

He lives in Northern California. I live in Southern California. He must have sent the virus to me with UPS. I am surprised UPS didn't drop the package and damage it.

NOW-NOW THIS UPS thing is starting to bother me ! They are delivering my foam The box better be in good shape !!

[naturephoto1]

Originally Posted by crazyBLUE

NOW-NOW THIS UPS thing is starting to bother me ! They are delivering my foam The box better be in good shape !!

At least your foam is light and not easily breakable. That is unlike Ben's and my problems with them.

Rich

[crazyBLUE]

Originally Posted by naturephoto1

At least your foam is light and not easily breakable.

Rich

So true Rich ! & am sorry to hear about you're reicever !

[Slec]

Rich, out of curiosity. What music are you planning on doing the comparison with?

~chris

[Big Daddy]

Originally Posted by crazyBLUE

NOW-NOW THIS UPS thing is starting to bother me ! They are delivering my foam The box better be in good shape !!

Damaging foam requires a pair of scissors. I don't believe even UPS is capable of doing that.

[naturephoto1]

Originally Posted by crazyBLUE

So true Rich ! & am sorry to hear about you're reicever !

Thanks, I won't quibble, but in my case it was the just brought to the latest upgrades of my Onkyo 885 Pre/Pro. It will be fixed and hopefully relatively quickly and easily. In Ben's case which certainly looks a lot worse, it was his McIntosh amp.

Rich

[crazyBLUE]

Originally Posted by Big Daddy

Damaging foam requires a pair of scissors. I don't believe even UPS is capable of doing that.

I don't know about that , They put it all in 1 box (108 sq. ft. & 2 corner traps) it's got to be A big box !! 15 lbs.

[naturephoto1]

Originally Posted by Slec

Rich, out of curiosity. What music are you planning on doing the comparison with?

~chris

Hi Chris,

I have some reference disks that I use of guitar along with some music by Loreena Mckennitt, possibly David Foster, Pink Floyd, amongst other CDs.

I hope that the participants can bring some music that they know well and then we can also listen to that as well. I want everyone to have the ability to get accustomed to the sound of the speakers, amps as well as the other components so that they can make an educated evaluation and assessment.

Rich

[liquidice]

with all this talk about SPL measurement, I'm moving closer to buying a meter. I've read that the analogue meters are better than the digital. Truth to that? I personally would feel better looking at analogue.

[Big Daddy]

Originally Posted by liquidice

with all this talk about SPL measurement, I'm moving closer to buying a meter. I've read that the analogue meters are better than the digital. Truth to that? I personally would feel better looking at analogue.

Neither is really better. The digital model is easier to use. It gives you an actual reading like 75dB, 80dB, etc. The analogue model gives you relative readings like +5dB, -3dB, etc. For most amateur HT use, I would recommend the Radio Shack digital SPL meter. I bought my digital SPL meter about 10-15 years ago.

[aramis109]

Originally Posted by Big Daddy

To the best of my knowledge, most receivers use PINK NOISE. Did you mean something else?


That is quite normal. Even if you move a couple of inches, the reading may change. It is the nature of long wavelength bass frequencies. They like your room walls too much.

When you use the pink noise from your receiver to adjust the subwoofer level, you will not get accurate results. The main reason is that your calibration program or the SPL meter (if you are using one) measure the peak frequency generated by the sub at that listening position and all other frequencies are obscured. This is why it is best to use test tones and an SPL meter for a subwoofer calibration.

How to Adjust Your Subwoofer:
Using a test tone disc, adjust the volume so that the SPL meter reads 75dB with a 50Hz tone at the listening position. Take measurements of four different tones 1/3 octave above the crossover point and four different tones 1/3 octave below the crossover point. Average together each set of four measurements and adjust the subwoofer’s volume level to match the other speakers.

Free Test Tones:
http://www.realtraps.com/test-cd.htm
http://www.cleansofts.com/softdownlo...Generator.html
http://www.nch.com.au/tonegen/index_b.html

Rives Audio Test Tones ($21):
http://www.rivesaudio.com/order/orderframe.html

Check these threads:
Calibrating Your Audio With an SPL Meter.
Calibrating Your Subwoofer(s) with the Velodyne SMS-1 Equalizer/Analyser.

Dfinitions:
White noise has the same distribution of power for all frequencies, so there is the same amount of power between 0 and 500Hz, 500Hz and 1,000Hz or 20,000Hz and 20,500Hz.

Pink noise has the same distribution of power for each octave, so the power between 0.5Hz and 1Hz is the same as between 5,000Hz and 10,000Hz.

Octave: assume one note has a frequency of 200Hz, the note an octave above it is at 400Hz, and the note an octave below is at 100Hz. The ratio of frequencies of two octaves is 2:1. Another examlple: 50Hz is one octave below 100Hz, and 400Hz is two octaves above 100Hz.

Depending on the crossover frequency (low pass filter frequency), these are the 1/3 octave apart frequencies that you need to calibrate your subwoofer(s): 20Hz, 25Hz, 31.5Hz, 40Hz, 50Hz, 63Hz, 80Hz, 100Hz, 125Hz, 160Hz, 200Hz, 250Hz, 315Hz.

Hey, thanks for this. I know you've posted it before, but honestly I didn't get it. Now that I have some more knowledge of the SPL, the receiver, test tones and all of that, this makes sense. You guys are teaching me- it just takes awhile to pound through this 34 year-old thick skull. I'll give this a try this weekend.

I will say that I watched Eagle Eye and the bass was very pronounced. It just didn't "linger" like I'm used to, so it was different for me. The ultimate test is if I like it better. So far, I do but I'd like to tweak it more so I'll try the above.

[Driver_King]

Big Daddy, have you gotten around to building some risers or something of that nature for your fronts? If so, post pictures and give us an idea of how it sounds. If not, get to it!