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Author Topic: Speaker measurement  (Read 11344 times)

Ben Dean

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Speaker measurement
« on: January 25, 2016, 11:39:50 am »

Hi,
Can you help me? I want to measure speaker parameters. I know I need: measurement microphone, audio interface, amp, pc, software and measurement room. But I do not know how to measure. Maybe you can advise about:

*microphone (linear frequency response between 20 Hz and 20kHz) - which model to use?
*USB audio interface - which model to use?
*amp for speaker - what amplifier to use? If I use cheap amp whose frequency response between 20 Hz and 20kHz is not linear, I'll get bad results. Yes?
*What software to use?
*Measuring the room acoustics - how to measure it? If room acoustics distorts frequency between 20 Hz and 20kHz I'll get bad results. Yes?
*Do I need frequency generator?

How to measure:
*Sensitivity (1w @ 1m)?
*Continuous SPL?
*Max SPL?
*Frequency responce (-10db)?
*Frequency responce (-3db)?

maybe you can share your experience?

Best regards,
Ben


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David Allred

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Re: Speaker measurement
« Reply #1 on: January 25, 2016, 12:16:07 pm »

I assume that you are really wanting to measure the speakers response in a cabinet, not the parameters.  The manufacture can provide the parameters.

Unless you build an anechoic chamber, outdoor measurements are the best solution.  Speaker at least 6-8 ft off the ground (grass is best).  No flat surfaces to the sides that can direct sound to the mic in any way.  No flat surfaces to the rear of the speaker that can bounce low energy back forward.  No flat surfaces in front of the speaker for at least 100 ft.  No overhead surfaces at all.  The mic should be elevated to mid speaker height.  I would take 2 readings.  One at the distance equal to speaker's height and one at a distance equal to the typical middle of the crowd.  Average the 2 readings.
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Ben Dean

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Re: Speaker measurement
« Reply #2 on: January 25, 2016, 01:09:14 pm »

I assume that you are really wanting to measure the speakers response in a cabinet, not the parameters.  The manufacture can provide the parameters.

Unless you build an anechoic chamber, outdoor measurements are the best solution.  Speaker at least 6-8 ft off the ground (grass is best).  No flat surfaces to the sides that can direct sound to the mic in any way.  No flat surfaces to the rear of the speaker that can bounce low energy back forward.  No flat surfaces in front of the speaker for at least 100 ft.  No overhead surfaces at all.  The mic should be elevated to mid speaker height.  I would take 2 readings.  One at the distance equal to speaker's height and one at a distance equal to the typical middle of the crowd.  Average the 2 readings.

Thanks for the reply :)

I have built full range speaker and subwoofer, I want to measure (Sensitivity (1w @ 1m); Continuous SPL; Max SPL; Frequency responce (-10db); Frequency responce (-3db)).

Ok, we have one answer to question (*Measuring the room acoustics - how to measure it? If room acoustics distorts frequency between 20 Hz and 20kHz I'll get bad results. Yes?) Answer: "outdoor measurements are the best solution".

What about other questions?
*microphone (linear frequency response between 20 Hz and 20kHz) - which model to use?
*USB audio interface - which model to use?
*amp for speaker - what amplifier to use? If I use cheap amp whose frequency response between 20 Hz and 20kHz is not linear, I'll get bad results. Yes?
*What software to use?
*Do I need frequency generator?

How to measure:
*Sensitivity (1w @ 1m)?
*Continuous SPL?
*Max SPL?
*Frequency responce (-10db)?
*Frequency responce (-3db)?

it would be great if forum members: for example to the question (*USB audio interface - which model to use?) reply (I use Brand name XXXX Model XXXX interface) or (How to measure:*Sensitivity (1w @ 1m)?) answer: (You need XXXXXX equipment and measure in this way: XXXX )

:)


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Ivan Beaver

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Re: Speaker measurement
« Reply #3 on: January 26, 2016, 09:46:46 pm »

It is not a simple step by step process.

There are a lot of variables.

What to suggest depends on lot on what sort of results you are looking for-especially in terms of accuracy.

An OK mic could cost you $50.  A good flat mic will cost you well over $1000.

There are all kinds of programs out there from free to several thousand dollars.

But the program is the EASY part.

LEARNING how to measure- is a bit/a lot more difficult.

You need an amp with at least 4 times the expected power capacity of the speaker-if you want to pass high level test signals.

There are ways to calculate the max SPL-based on accurate low level measurements and good loudspeaker driver data.

You will also need a calibrator.  Those can be kinda cheap to pretty expensive.

The FIRST-most important question is-what sort of budget do you have for this?

If all you want is 1 speaker to be measured-then you might be better off paying somebody else to do it-who already knows how and has the gear/setup.

You can get "some" data pretty easy.  But the "trick" is making sure it is accurate.

Just because it shows up on a computer screen DOES NOT mean that it is real or reliable.
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Ivan Beaver
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Ivan Beaver

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Re: Speaker measurement
« Reply #4 on: January 26, 2016, 10:23:09 pm »

Thanks for the reply :)

I have built full range speaker and subwoofer,
This is not intended to sound rude, but is just something to consider.

You said you built a full range speaker.  Yet it seems as if you have no measurement tools or knowledge on how to use them.

How did you determine what parts to use?

How is the crossover done?

If you have not measured the parts before assembling and designing the crossover-then there is a very good possibility that the response is going to be FAR from flat.

If you do not have a relatively flat response, then the "sensitivity rating" could be all over the place.

Are you looking for an average sensitivity? or a peak in the response?  You have to choose something from the measurement.  It DOES NOT give you an answer-only a graph that you have to look at and determine what sort of answer you want.

Until you establish a sensitivity-any sort of -3 or -10dB number is going to be pretty meaningless.  Because they will be referenced to anything.  3dB down from what?

The way speakers are "usually" designed, is that the drivers are measured first, then matched up-then the cabinet is built.  Or in some cases-specifically horns, the drivers need to be on the horn to be measured.

After that the individual drivers are measured for amplitude-phase and impedance.

Then the crossover is designed based on those measurements.

Then the prototype crossover is assembled and tested for amplitude-phase and impedance.  You need to make sure the crossover does not dip to low in impedance and that the phase of the crossover does not get to extreme so that it puts a strain on the amp by either driving a load that is to reactive.

Then a know level noise signal is put into the system (I use 5V full spectrum flat pink-except highpassed where expected., and the voltage across each of the crossover parts is measured and the voltage going to each of the drivers.

Then a multiplier is used to calculate how much additional signal can be sent so that driver that reaches its limit first is the limiting factor.

Then you multiply that by all the voltage in all of the parts of the crossover to figure out the wattage and voltage ratings of the components-then add a "headroom factor" that would be appropriate.  This is usually 4 times the wattage and twice the voltage.

Now that you have the crossover designed- you can measure the final product.

OR, you can just pile some components into a box and hope it somehow works ok.

The whole process is not simple nor fast.  At least to do it with any sort of accuracy.
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Ivan Beaver
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PHYSICS- NOT FADS!

Merlijn van Veen

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Re: Speaker measurement
« Reply #5 on: January 27, 2016, 07:29:13 am »

Do some reading up like maybe the Smaart user guide to get an impression


Verzonden vanaf mijn iPad met Tapatalk

Ben Dean

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Re: Speaker measurement
« Reply #6 on: January 27, 2016, 07:38:52 am »

It is not a simple step by step process.



Why are you saying that there is not a simple step by step? To carry the subwoofer to outside is simple, elevate mic using stand to the speaker height is simple, connect mic with sound card is simple, connect amp with sound card is simple, connect amp wit subwoofer is simple, connect sound card with PC is simple, install and use software is not so hard. So whole process is quite simple. But probably there are certain conditions that would be more accurate measurements? For example David Allred wrote: "Speaker at least 6-8 ft off the ground (grass is best).  No flat surfaces to the sides that can direct sound to the mic in any way.  No flat surfaces to the rear of the speaker that can bounce low energy back forward.  No flat surfaces in front of the speaker for at least 100 ft."


What to suggest depends on lot on what sort of results you are looking for-especially in terms of accuracy.



I need:
*Sensitivity (1w @ 1m)?
*Continuous SPL?
*Max SPL?
*Frequency responce (-10db)?
*Frequency responce (-3db)?


An OK mic could cost you $50.  A good flat mic will cost you well over $1000.
There are all kinds of programs out there from free to several thousand dollars.


It should be a budget version to 150$.
If there are some good programs for free, so why do not use them?


LEARNING how to measure- is a bit/a lot more difficult.



You say it's hard, but you do not even have said how to measure. maybe it just seems hard to you? solder others seem hard, but for me it is a piece of cake. Others may seem difficult to build 3D printer, but I had build 2  3D printers. Therefore, do not say that something is difficult, because maybe difficult is just for you.
Write the whole process and then you can say it is difficult or not, what do you think?



There are ways to calculate the max SPL-based on accurate low level measurements and good loudspeaker driver data.


For exmple Eighteensound 18LW2400 in different boxes will have different Sensitivity (1w @ 1m); Continuous SPL and Max SPL. it all depends on the box, so what is the way to measure. Do I need individual SPL meter?


The FIRST-most important question is-what sort of budget do you have for this?


I have the amp, so I need Mic and Sound card for them about 500$ and free software.


If all you want is 1 speaker to be measured-then you might be better off paying somebody else to do it-who already knows how and has the gear/setup.


Because building subwoofer box I can not calculate the exact size it needs to be done for best performance I measure speaker, then i will build another a little different box and then again measure and so on.
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Cailen Waddell

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Re: Speaker measurement
« Reply #7 on: January 27, 2016, 07:49:28 am »

First - I smell a troll.

Presumably you took the parameters of your known driver and modeled the box for your subwoofer. So really you are measuring to confirm or disprove performance matching the model.

Third - you are aware that Ivan builds and designs speakers with some other guys-you-should-of-heard-of, so when he talks about the process, he knows what he is talking about.

Fourth - Ivan told you how to get sensitivity and -3db and -10db numbers in his post. And covered the issues involved and why it's not simple.

So lastly, it would seem that while English is clearly not your first language, despite your anglicized name, you just want a simple cheap solution where none exists.  And you don't want to hear the correct answer being given to you, so i am left with no choice, based on how you have portrayed yourself here, but to think you are a fucking moron.  Hopefully that translates for you.


Sent from my iPhone using Tapatalk
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Ben Dean

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Re: Speaker measurement
« Reply #8 on: January 27, 2016, 07:49:56 am »


You said you built a full range speaker.  Yet it seems as if you have no measurement tools or knowledge on how to use them.
How did you determine what parts to use?

How is the crossover done?

If you have not measured the parts before assembling and designing the crossover-then there is a very good possibility that the response is going to be FAR from flat.

I use X over 3 PRO, there are only theoretical calculations, I did not do any live measurements, therefore, I write to this forum.


Are you looking for an average sensitivity? or a peak in the response?


After all, I already wrote that I need Sensitivity (1w @ 1m); Continuous SPL and Max SPL.



Until you establish a sensitivity-any sort of -3 or -10dB number is going to be pretty meaningless.  Because they will be referenced to anything.  3dB down from what?

All manufacturers specify the  -10dB and +/- 3dB. Example: https://www.jblpro.com/ProductAttachments/JBL.SRX718S[1].pdf

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David Allred

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Re: Speaker measurement
« Reply #9 on: January 27, 2016, 08:03:06 am »

Perhaps also, if we knew what your intent was, better advice could be given.
For example:

I want to save money by building my own Class A speakers, to use in my sound production for hire company.
I am a DJ just trying to build some loud speakers that sound not bad.
I am putting together a home system.
I am a hobbyist, just playing around.
I am the next Tom Danley, just trying to get started.
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ProSoundWeb Community

Re: Speaker measurement
« Reply #9 on: January 27, 2016, 08:03:06 am »


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