Subwoofer testing methodology - what do you think is important? - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 33 Old 02-06-11, 03:49 PM Thread Starter
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Subwoofer testing methodology - what do you think is important?

Hi all - This is an open thread to discuss subwoofer testing methodology. What is important when testing a subwoofer?

1. Frequency Response?
2. Max output at various frequencies?
3. Distortion at various frequencies and SPL levels?
4. Standard Features?

To get this started ... let's say this was proposed as a method for testing subwoofers, would everyone agree that this is the optimal approach?

Proposed testing method #1.

A. All subwoofers will be tested outdoors at one meter Groundplane.
B. Six different frequencies will be tested on each subwoofer at varied lengths of time, shown below. The purpose of using these test tones will be to find how much SPL, measured in dB, that each subwoofer can deliver at each frequency shown for the duration shown.
C. 20 Hz will have a test tone which lasts 0.325 second.
D. 25 Hz will have a test tone which lasts 0.260 second.
E. 31.5 Hz will have a test tone which lasts 0.206 second.
F. 40 Hz will have a test tone which lasts 0.1625 second.
E. 50 Hz will have a test tone which lasts 0.130 second.
F. 63 Hz will have a test tone which lasts 0.103 second.
G. Each test tone will be delivered at increasing SPL until the subwoofer is exceeding 40% THD at a given frequency.
H. Bass below 20 Hz will not be measured.

This is proposal 1 for a subwoofer test methodology.

Please feel free to chime in with opinions on this.
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post #2 of 33 Old 02-06-11, 04:06 PM
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Re: Subwoofer testing methodology - what do you think is important?

Are the different frequencies measured in a sweep or independent test tones generated one at a time?

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post #3 of 33 Old 02-06-11, 04:11 PM Thread Starter
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Re: Subwoofer testing methodology - what do you think is important?

Dale - This methodology would use independent test tones, not a sweep.

And for those who hate decimels ... .325 second is less than 1/3rd of a second. These tones range from about 1/3rd of a second for 20 Hz to about 1/10th of a second for 63 Hz.
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post #4 of 33 Old 02-06-11, 04:18 PM
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Re: Subwoofer testing methodology - what do you think is important?

That's what I thought, just wanted to make sure.

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post #5 of 33 Old 02-06-11, 04:27 PM Thread Starter
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Re: Subwoofer testing methodology - what do you think is important?

For further clarification - There is a real lack of meaningful subwoofer testing being done now, and the home theater world could use some testing done which combines both measurements which reflect real world performance along with (as unbiased as is reasonably possible) listening tests.

I put up the methodology in the first post in order to give people a starting point for testing subs.

The first post is intended to get the members here to say "I think it's a great test, and here is why" ... or ... "I think it needs a lot of improvements, and here is why ... "

Let's see some opinions ...EVERYONE READING THIS is welcome to reply.
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post #6 of 33 Old 02-06-11, 04:32 PM
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Re: Subwoofer testing methodology - what do you think is important?

I would prefer a down frequency sweep beginning at 200Hz and ending at 5Hz increasing in amplitude until the peak output is compressed 1dB (if 1dB is not adequate for audio testing then 3dB compressed).
I would also like to see distortion at 10Hz or 20Hz intervals along with 2nd and 3rd order harmonics.

I am really not all that concerned about burst mode, if the performance is there in swept mode it will be there in burst mode.
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post #7 of 33 Old 02-06-11, 04:34 PM
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Re: Subwoofer testing methodology - what do you think is important?

I agree that we need to establish a better methodology for subwoofer testing that is not only indicative of real world results, but is also repeatable. I think this is a great starting point.

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post #8 of 33 Old 02-06-11, 04:36 PM Thread Starter
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Re: Subwoofer testing methodology - what do you think is important?

Quote:
chashint wrote: View Post
I would prefer a down frequency sweep beginning at 200Hz and ending at 5Hz increasing in amplitude until the peak output is compressed 1dB (if 1dB is not adequate for audio testing then 3dB compressed).
I would also like to see distortion at 10Hz or 20Hz intervals along with 2nd and 3rd order harmonics.

I am really not all that concerned about burst mode, if the performance is there in swept mode it will be there in burst mode.
This is the type of response that will make for a great thread.
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post #9 of 33 Old 02-06-11, 05:34 PM
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Re: Subwoofer testing methodology - what do you think is important?

Sounds like a great starting point. Have fun. Dennis

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post #10 of 33 Old 02-07-11, 06:55 AM Thread Starter
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Re: Subwoofer testing methodology - what do you think is important?

So far ... 78 views and one suggestion. No one has commented on the first criteria as posted.

I will offer up what I think is important ...

1. Max output using sinewaves (either sweep or individual) before audible distortion is detected by the tester, who should be several meters away from the subwoofer.

2. Frequency response curves along with analysis of the posted response curve against maximum output curves. Why this analysis? Let's say we are looking at two sealed subwoofers. Subwoofer "A" is +/- 3 dB from 15 to 100 Hz while subwoofer "B" is down 9 dB at 15 Hz.

The first impression may well be that "A" is superior to "B".

But then we have the max output sweeps ... and we see that "B" delivers, say, 100 dB at 15 Hz while "A" delivers only 91 dB.

We can conclude that "A" likely has more eq built into the response curve, and that "B" was designed with less eq, but more output.

"B" is actually the more powerful, capable subwoofer.

Without analysis, people may miss this.

More later.
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