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Author Topic: Understanding speaker specs  (Read 3388 times)

Jonathan Johnson

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Re: Understanding speaker specs
« Reply #10 on: January 22, 2013, 11:06:36 am »

10-3 (sorry, I can't type superscript)

FYI, the standard method for typing "powers" where you can't superscript, is to use a caret.

10^1=10
10^2=100
10^3=1,000
...
10^10=10,000,000,000

At least, that's what I learned in my math & science classes.

But if you're posting to this forum, you can encase the superscript text in [ sup ] tags (the "sup" button in the edit window does this); typing the following:

Code: [Select]
10[sup]4[/sup]=1000
gets you 104=1000
« Last Edit: January 23, 2013, 03:14:57 pm by Jonathan Johnson »
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Tim McCulloch

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Re: Understanding speaker specs
« Reply #11 on: January 22, 2013, 11:07:20 am »

Perhaps, if you're used to looking at smoothed graphs - if it is the unsmoothed plot of speaker I wouldn't consider it particularly bad?

Exactly.  Seeing unsmoothed response that is *mostly* ±5dB across the operating bandwidth is not too bad, especially for a brand/model that most gear snobs would ignore.

Allen, this isn't worth worrying about.  I did this over 25 years ago and EQ'd myself into less signal and no net audible improvement.  Besides, as has been pointed out, much of your perception of the speaker output will change in situ, so you'll be better off waiting until the speakers are in position, the band is playing, etc.
« Last Edit: January 22, 2013, 11:16:47 am by Tim McCulloch »
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AllenDeneau

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Re: Understanding speaker specs
« Reply #12 on: January 22, 2013, 12:30:31 pm »

Exactly.  Seeing unsmoothed response that is *mostly* ±5dB across the operating bandwidth is not too bad, especially for a brand/model that most gear snobs would ignore.

Allen, this isn't worth worrying about.  I did this over 25 years ago and EQ'd myself into less signal and no net audible improvement.  Besides, as has been pointed out, much of your perception of the speaker output will change in situ, so you'll be better off waiting until the speakers are in position, the band is playing, etc.

Thanks Tim, good advice and makes sense, it just got me thinking, "why I don't use this graph's info more" is all really. Sometimes, ok a lot of times, I'll overthink some info I have and this is a result LOL!

So how does a person know if the reponse graph has been smoothed or if a nice and smooth response is a natural characteristic of that speaker? I just compared my OLD SP2G to a brand new VRX 15" monitor and for sure the VRX is smoother BUT is that after correction and smoothing or is that unsmoothed. Not to mention that technology is nearly 15 years newer than my SP2G...

To expand a little on what Paul said (and making wild assed assumptions to make this example work...), lets say you looked at that graph and decided to boost 1k6 on your graphic EQ to try and flatten the response there.

The problem is you don't know what's causing that dip there. If the crossover point of the box happens to be around there, then one possible cause for the dip would be a phase (or polarity) difference between the Mid and High drivers, causing cancellation of the acoustic output of the adjacent devices. If that is the case, then that phase/polarity difference will continue to cause cancellations even if you do stick a stronger signal in to the box at those frequencies, so youll be making your amp and drivers work harder to no avail.
HTH,
David.

Thanks David, I didn't even think about that. As you may recall from my subwoofer driver thread, speaker design and understanding it isn't something I'm, sadly, proficient with so I'd love to learn more so I can better predict the systems capabilities or process the info I'm hearing while setting up the PA. How would a person determine what's causing said valleys and peaks due to phase/polarity?

Because a 1/3 octave EQ is a pretty bad tool to try and correct a speakers response with, ideally you want the fully adjustable notch and shelving filters found in a DSP processor. But even with that and an RTA display to look at you're not going to get a ruler flat response no matter how many filters you apply, and that's because speaker response is a product of the amplitude and phase response of the drivers and crossover components and how all that interacts with the room it's in, so you simply cannot correct that with an amplitude only device like an EQ... and that's ignoring the phase altering side effects of those EQ filters that you have no control over.

Great points Paul, since I have a full Peavey SP system, minus the amps, that's why I bought the VSX26 DSP to have better control over settings and parameters. That's a big reason as to why I'm asking such questions like these. Since reloacting I've had little chance to run my system so I haven't even set the rig up with the VSX yet but, I plan on using the 3 way preset to start as it's gonna be a pretty good starting point, I'm told. Then I can continue to learn more of the finer points of system tuning vs grabbing an eq fader and going to town. At least I hope that's how it'll all play out.

I'll send you the message again, thanks.

FYI, the standard method for typing "powers" where you can't superscript, is to use a carat.

10^1=10
10^2=100
10^3=1,000
...
10^10=10,000,000,000

At least, that's what I learned in my math & science classes.

But if you're posting to this forum, you can encase the superscript text in [ sup ] tags (the "sup" button in the edit window does this); typing the following:

Code: [Select]
10[sup]4[/sup]=1000
gets you 104=1000


Thanks Jonathan, now I just need to find an excuse to use that info more, watch out for new posts, LOL! I knew there was a way, it's just been way too long since I've had a math class, man I'm old.
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Brad Weber

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Re: Understanding speaker specs
« Reply #13 on: January 22, 2013, 12:34:11 pm »

Exactly.  Seeing unsmoothed response that is *mostly* ±5dB across the operating bandwidth is not too bad, especially for a brand/model that most gear snobs would ignore.
It's surprising how many speakers have published +/-XdB frequency response numbers that seem wishful thinking if you look at the associated response graph.  It's also not unheard of for speaker manufacturers to publish 'corrected' numbers or response graphs that include applying their recommended processing, something that is not always clearly identified.  What it comes down to is not just looking at the numbers but also understanding what those numbers represent.
« Last Edit: January 24, 2013, 07:41:47 am by Brad Weber »
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Jonathan Johnson

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Re: Understanding speaker specs
« Reply #14 on: January 23, 2013, 03:16:55 pm »

typing the following:

Code: [Select]
10[sup]4[/sup]=1000
gets you 104=1000

and an "F" on your math paper. There should either be four zeroes there, or the power should be 3. My bad.
« Last Edit: January 23, 2013, 09:26:41 pm by Jonathan Johnson »
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Scott Bolt

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Re: Understanding speaker specs
« Reply #15 on: January 23, 2013, 08:10:33 pm »

Perhaps, if you're used to looking at smoothed graphs - if it is the unsmoothed plot of speaker I wouldn't consider it particularly bad?

From here page 20 for a PRX612M:  http://www.jblpro.com/BackOffice/ProductAttachments/DOC_1672.pdf

Pretty flat.
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Ivan Beaver

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Re: Understanding speaker specs
« Reply #16 on: January 23, 2013, 09:01:38 pm »

Here is an example of different amounts of smoothing applied to the same speaker response.

This is just a single driver I measured the other day.
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Ivan Beaver
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Scott Bolt

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Re: Understanding speaker specs
« Reply #17 on: January 26, 2013, 06:40:55 pm »

Thanks Ivan.

So how is the smoothing performed?  Is it a rolling average or something similar?  It has been my experience that doing any smoothing shifts the curve you are smoothing.

In the specs we see on different speakers, is there anywhere we can tell how much smoothing was used?
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Ivan Beaver

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Re: Understanding speaker specs
« Reply #18 on: January 26, 2013, 09:48:47 pm »

Thanks Ivan.

So how is the smoothing performed?  Is it a rolling average or something similar?  It has been my experience that doing any smoothing shifts the curve you are smoothing.

In the specs we see on different speakers, is there anywhere we can tell how much smoothing was used?
In the case I presented, it is simply a percentage.  The percent is in octave terms-so 100% is 1 octave (the graph with the most smoothing).  33% would be 1/3rd octave.

Another way of performing smoothing is to simply use less points in the measurement.

And then there is the "marketing smoothing" in which they just simply redraw the graph to be what they want it to be-no matter what the actual measurement is.  YES it has been done.

Or you can use a wider trace line or change the scale and so forth.

OF course in the old days of chart recorders-you just simply change the speed of the chart.

I guess the best way to find our for sure would be to look closely at the graph and see if it says-or in some small print or call the manufacturer and see if you could get through to somebody who could give you that information.
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Ivan Beaver
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Scott Bolt

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Re: Understanding speaker specs
« Reply #19 on: January 27, 2013, 11:55:24 am »

In the case I presented, it is simply a percentage.  The percent is in octave terms-so 100% is 1 octave (the graph with the most smoothing).  33% would be 1/3rd octave.

Another way of performing smoothing is to simply use less points in the measurement.

And then there is the "marketing smoothing" in which they just simply redraw the graph to be what they want it to be-no matter what the actual measurement is.  YES it has been done.

Or you can use a wider trace line or change the scale and so forth.

OF course in the old days of chart recorders-you just simply change the speed of the chart.

I guess the best way to find our for sure would be to look closely at the graph and see if it says-or in some small print or call the manufacturer and see if you could get through to somebody who could give you that information.

Ahh....

It would be my conclusion then that the curve should be published without any "smoothing".  It is simply becoming "not accurate" and certainly not representative in any way.
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