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Author Topic: Max SPL on a sub  (Read 4045 times)

Chris Grimshaw

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Re: Max SPL on a sub
« Reply #10 on: May 11, 2017, 07:10:41 am »

Its a spec war there, and it is ugly.

Very true.

I spent a little while yesterday arguing with a member of a sales team that a single 10" direct-radiating box cannot possibly output 136dB and still sound good, pointing out that a 10" driver on the ground would need to move a little over 3" one-way to produce that SPL at 80Hz. They were adamant that the speaker would hit it's ratings. I don't care if the box does have a well-regarded name on the front. Physics is physics.

I was encouraged to talk to the R&D department, so I might post up a thread if anything comes of that.

Chris
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Ivan Beaver

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Re: Max SPL on a sub
« Reply #11 on: May 11, 2017, 07:42:33 am »

Very true.

I spent a little while yesterday arguing with a member of a sales team that a single 10" direct-radiating box cannot possibly output 136dB and still sound good, pointing out that a 10" driver on the ground would need to move a little over 3" one-way to produce that SPL at 80Hz. They were adamant that the speaker would hit it's ratings. I don't care if the box does have a well-regarded name on the front. Physics is physics.

I was encouraged to talk to the R&D department, so I might post up a thread if anything comes of that.

Chris
OF course it always begs the questions-at what distance?-At what freq?-for how long?-using what meter?

A small firecracker can produce lot of SPL-but not for very long.

I just realized that the well respected NTI XL2 meter has a "flaw" (in my opinion) regarding the peak SPL scale.

It actually measures the peak of the sound envelope-while the other scales measure the "RMS" of the envelope.

So the Peak readings are 3dB higher that what I would consider the "peak", which would be the maximum level.

I know others will disagree, and argue about the meaning of "peak".

I will agree with them to some respect-but disagree about the "intended meaning of the reading".

So simply by using a meter that reads like this-you get a "free 3dB" of extra output to put on a spec sheet.

HOW you measure will GREATLY affect the actual readings.

A typical "hardish" show can easily produce differences of 30dB (or greater) between different scales/weighting etc when measuring the same signal.

So how loud is it?  All of them-it depends on how it is being measured
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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!

Jeff Bankston

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Re: Max SPL on a sub
« Reply #12 on: May 11, 2017, 11:56:07 pm »

you can always crank it up until you hear the vc bottom and then back off a tad. I dont know how many times you could do that before its broke and I aint gonna try, especially not with a $600.00 driver.
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Chris Grimshaw

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Re: Max SPL on a sub
« Reply #13 on: May 12, 2017, 04:08:04 am »

you can always crank it up until you hear the vc bottom and then back off a tad. I dont know how many times you could do that before its broke and I aint gonna try, especially not with a $600.00 driver.

I did this by mistake and folded the cone on a Beyma 15P1200Nd. No highpass filter, lots of power, and the software started the sweep an octave down on the start value I entered. The 2" peak-to-peak travel was impressive, though, and my SPL meter read >133dB.

Chris
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Ivan Beaver

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Re: Max SPL on a sub
« Reply #14 on: May 12, 2017, 06:55:32 am »

you can always crank it up until you hear the vc bottom and then back off a tad. I dont know how many times you could do that before its broke and I aint gonna try, especially not with a $600.00 driver.
That only works on the excursion limit, but in many cases the driver could burn out long before it hits the excursion limit.

It depends on the particular freq of interest.

Sometimes excursion and power are related-at other freq they are not.
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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 #15 on: May 26, 2017, 01:20:10 pm »

After inital tests, it seems like my little sub will do at least 144dB peak.

Not bad for a homebrew dual 18".

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Chris Grimshaw

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Re: Max SPL on a sub
« Reply #16 on: May 30, 2017, 01:19:05 pm »

After inital tests, it seems like my little sub will do at least 144dB peak.

Not bad for a homebrew dual 18".

Interesting, you've beaten the simulations for a single high-power 18" with 120v RMS input in a 11cu.ft (internal) tapped horn by around 10dB.

What were the conditions where you measured that SPL?

Chris
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Helge Dr. Bentsen

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Re: Max SPL on a sub
« Reply #17 on: May 30, 2017, 04:38:39 pm »

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.


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Mark Wilkinson

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Re: Max SPL on a sub
« Reply #18 on: May 30, 2017, 07:03:55 pm »

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.

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?
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Pete Erskine

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Re: Max SPL on a sub
« Reply #19 on: May 30, 2017, 08:26:16 pm »

Is there a reliable and practical method of determining the real-world SPL from a subwoofer "in the field"?

I'm building a prototype for a sub and wish to have some idea about how much SPL it put's out within it's intended bandwidth.

While not answering your question, assuming you have no limit on power and the sub does not fall apart, the loudest sound would be 194 dBm.  Above that it is no longer sound, it is a shock wave.
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Pete Erskine
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