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Author Topic: Max SPL on a sub  (Read 6224 times)

Helge Dr. Bentsen

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Re: Max SPL on a sub
« Reply #20 on: May 31, 2017, 02:58:04 am »

Hi Helge, when quoting SPL's, I really believe in using a mic calibrator....otherwise I feel like i'm building off "he said, she said"
And they are fairly cheap.
Admittedly, I have no idea how well a calibrator dialed in at 1KHz (which is all i've ever seen) behaves in sub range, but it's gotta be better than comparing one box against another box'es specs, no matter how well regarded the manufacturer is, yes?

My Smaart setup is calibrated with a mic calibrator. I verify this before I start any spl measurement.
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Chris Grimshaw

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Re: Max SPL on a sub
« Reply #21 on: May 31, 2017, 05:17:20 am »

I took a pair of active dual 15" subs from a known manufacturer and feed them with a signal untill an increase in drive level didn't increase the output from them as verified by Smaart.

I recorded the level and was able to match the same output with my sub. I didn't test where it goes into hard limiting, just that I could match the output.
The Dual 15" has a SPL Peak rating of 138dB, and a pair of them sums +6dB on my Smaart screen.

I understand your method, but I promise that the 2x15" did not hit 138dB in the subwoofer band, no matter what the manufacturer says they can do.

I'm part-way through writing an article about this, but here's a glimpse into what manufacturers might do:

- 1x 15" speaker in a ported box, 1KW amplifier.
- At 40Hz, it's 93dB@1w input. The in-band response slopes a little, so it's 97dB @ 100Hz. There's also a cone break-up peak at 1.2kHz, where sensitivity reaches 103dB @1w.
- Even ignoring cone excursion issues and power compression, what's my maximum SPL?
- 40Hz: 123dB; 100Hz: 127dB; 1.2kHz: 133dB. Which number goes on the box?

Yep, you guessed it, this sub can technically make a sound that has an SPL of 133dB. It's at one frequency that the sub will never be used at, but that really won't stop the marketing team.

To produce the 138dB at 50Hz, the pair of 15" cones would need to move 3" one-way, or 6" peak-to-peak. This driver (https://www.parts-express.com/re-audio-xxx15-v2-4-15-cast-frame-dvc-subwoofer-driver-4-4-ohm--268-8153) won't manage that (it's about 1" short on cone travel), and it's the most bonkers 15" I can find.

Chris
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Mark Wilkinson

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Re: Max SPL on a sub
« Reply #22 on: May 31, 2017, 11:05:56 am »

My Smaart setup is calibrated with a mic calibrator. I verify this before I start any spl measurement.

Then I'm curious what smaart said the SPL of your 15's" were, when they were run at max.
And what type SPL...and speed?

FWIW, a real world usage measurement I've come to like, is Smaart's LEQ, using pink band-passed with the actual HP and LP filters I intend to use, in place.  IMO, this gives an average that is a decent proxy for "a one number meaningful spec".

And taken one step further, I measure LEQ with whatever eq I intend to use to smooth response.
I mean, that's where the sub is going to live, with HP, LP, and eq.....what can it do there?

Using a good RMS voltmeter with averaging, vs the LEQ readings, ....then power handling and even a sensitivity specs make sense to me.

Again FWIW.  I know how much experience you have, please advise if you see anything wrong with this methodology.
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Ivan Beaver

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Re: Max SPL on a sub
« Reply #23 on: May 31, 2017, 01:21:01 pm »

Then I'm curious what smaart said the SPL of your 15's" were, when they were run at max.
And what type SPL...and speed?


A simple SPL number on most subs doesn't really tell a whole lot.

Since most subs have a sloping response, they are louder at the higher freq in their range than at the lower freq.

So saying a number-any number MUST be attached to some freq or graph, or it is pretty meaningless.

As simple as most people want SPL to be, it is NOT an easy one number answer.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Mark Wilkinson

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Re: Max SPL on a sub
« Reply #24 on: May 31, 2017, 02:59:00 pm »

A simple SPL number on most subs doesn't really tell a whole lot.

Since most subs have a sloping response, they are louder at the higher freq in their range than at the lower freq.

So saying a number-any number MUST be attached to some freq or graph, or it is pretty meaningless.

As simple as most people want SPL to be, it is NOT an easy one number answer.

Hi Ivan, I kindly disagree.   And I get all the games being played with single number SPL.

IMHO, a LEQ taken with HP and LP filters in place representing intended usage, with their exact parameters provided,
along with average RMS voltage that corresponds to the LEQ period,
is a pretty dang good single number.

Again, what I've been advocating in a number of threads, and what I've seen Tom suggest as well.
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Helge Dr. Bentsen

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Re: Max SPL on a sub
« Reply #25 on: May 31, 2017, 03:20:14 pm »



FWIW, a real world usage measurement I've come to like, is Smaart's LEQ, using pink band-passed with the actual HP and LP filters I intend to use, in place.  IMO, this gives an average that is a decent proxy for "a one number meaningful spec".

And taken one step further, I measure LEQ with whatever eq I intend to use to smooth response.
I mean, that's where the sub is going to live, with HP, LP, and eq.....what can it do there?

Using a good RMS voltmeter with averaging, vs the LEQ readings, ....then power handling and even a sensitivity specs make sense to me.

Again FWIW.  I know how much experience you have, please advise if you see anything wrong with this methodology.

That's actually a rather nice idea.

The reason I started this thread is that I have for years heard people bashing manufacturers with "your SPL numbers are wrong!" but I've not seen too many helpful ideas about how to find a meaningful SPL number for real world usage.

I'm not going to sell this sub to anyone, but I'm genuinely interested in knowing how loud it is within it's operating range.

Hence the reason for using a pair of known subs as a benchmark. Now I have a known comparison.

But yes, generally speaking. Someone should write a paper on how to do this properly with the least amount of gear and know-how needed. Why? Because it can't be rocket science to measure a SPL number.
I mean, I own several things in my life that can tell me how fast I'm moving, the altitude above sea level, distance walked etc. Why can't we do the same with SPL instead of shouting "SPl numbers are wrong"?
« Last Edit: May 31, 2017, 03:26:50 pm by Helge Dr. Bentsen »
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Ivan Beaver

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Re: Max SPL on a sub
« Reply #26 on: May 31, 2017, 03:36:46 pm »

Hi Ivan, I kindly disagree.   And I get all the games being played with single number SPL.

IMHO, a LEQ taken with HP and LP filters in place representing intended usage, with their exact parameters provided,
along with average RMS voltage that corresponds to the LEQ period,
is a pretty dang good single number.

Again, what I've been advocating in a number of threads, and what I've seen Tom suggest as well.
I would agree with you.  But how often do you see spec measurements with HP and LP filters in place?  That would throw the numbers off (and not in a good way.

I do agree that this would give a better idea of the loudness in the intended range.  But would still "favor" the freq that are higher in level.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Ivan Beaver

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Re: Max SPL on a sub
« Reply #27 on: May 31, 2017, 03:42:36 pm »

That's actually a rather nice idea.

The reason I started this thread is that I have for years heard people bashing manufacturers with "your SPL numbers are wrong!" but I've not seen too many helpful ideas about how to find a meaningful SPL number for real world usage.

I'm not going to sell this sub to anyone, but I'm genuinely interested in knowing how loud it is within it's operating range.

Hence the reason for using a pair of known subs as a benchmark. Now I have a known comparison.

But yes, generally speaking. Someone should write a paper on how to do this properly with the least amount of gear and know-how needed. Why? Because it can't be rocket science to measure a SPL number.
I mean, I own several things in my life that can tell me how fast I'm moving, the altitude above sea level, distance walked etc. Why can't we do the same with SPL instead of shouting "SPl numbers are wrong"?
The big problem with "peak SPL" is the very nature of music being dynamic.

The peaks are of very short duration.

Most SPL meters do not have a response time fast enough to measure the peaks. 

Even the fast response is WAY to slow to measure the peaks

The "max" on many SPL meters is STILL not the peak.  But simple rather the maximum fast response.

The reason people with an average meter cannot measure the "max SPL" is because the average level (which is what the meters read) is easily 10-20dB below the peaks.

The loudspeakers ARE reproducing those peaks (assuming no power compression), but the simple meters can't measure them

Once again-something as seemingly simple as SPL is not so simple and has lots of variables attached to it.

In your examples, the object being measured is not changing-at least not fast (like music).

Any steady state signal/object is MUCH easier to measure.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!

Helge Dr. Bentsen

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Re: Max SPL on a sub
« Reply #28 on: May 31, 2017, 04:39:23 pm »

Yes Ivan, I know this. After all, you have been saying this for years to everyone.

Shouldn't you then, instead of telling us how difficult it is, how wrong everybody is when measuring SPL and how everybody is telling the wrong number write the paper about how to do this correctly and repeatably?

Lay down the criteria, the numbers, the signal, the procedure and tell us how to do this correctly. You obviously have the knowledge and it would be something we all cold learn from.
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Ivan Beaver

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Re: Max SPL on a sub
« Reply #29 on: May 31, 2017, 05:18:04 pm »

Yes Ivan, I know this. After all, you have been saying this for years to everyone.

Shouldn't you then, instead of telling us how difficult it is, how wrong everybody is when measuring SPL and how everybody is telling the wrong number write the paper about how to do this correctly and repeatably?

Lay down the criteria, the numbers, the signal, the procedure and tell us how to do this correctly. You obviously have the knowledge and it would be something we all cold learn from.
First of all, if you actually want to measure the peak, you MUST have a meter that can do so.

Most audio (pros even) do not want to spend that much money on a meter.

Without the meter, it does not matter what procedure you have.

I use an NTI XL2 meter.  There are others that are less expensive.

Even some good apps.  But the problem with the apps is that they are limited by the max SPL the mic or program can handle.

And that is well well below the 144dB of the NTI.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
Danley Sound Labs

PHYSICS- NOT FADS!
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