Speaker Measurement - Where to Begin

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rowuk
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#16 Re: Speaker Measurement - Where to Begin

Post by rowuk »

I second the recommendation of REW and Holm Impulse.
More important than the measurements is understanding the results. Basically we get a document of frequency vs “sound pressure level”, but what that level is caused by, is very much subject to interpretation. For instance floor bounce for drivers at “ear level”, dramatically changes level around 700 - 1100 Hz. This does motivate fixing the wrong things. Holm impulse is not quite as critical as REW for interpretation.
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Ray P
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#17 Re: Speaker Measurement - Where to Begin

Post by Ray P »

So, one step at a time, if I were to buy one of these;



and one of these;



along with sundries like an XLR cable and mic stand, I'll have the basic hardware required?
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#18 Re: Speaker Measurement - Where to Begin

Post by Ant »

Ive just realised ive got 2 possible 'proper' ways to measure speakers.
i bought a creative sb1240 external soundcard a couple of months back to try to compare the digital output of the delta 170.3 and the squeezebox (still havent got round to that...) which has a mic input, and a behringer um2 usb interface that has phantom power that i can connect a mic to aswell.
This was bought for my daughter to record her guitar via the instrument input.
I have a mic somewhere that requires a new 1/4" jack putting on it that could be prodded into use with the sb1240, the behringer doesnt seem to take that sort of mic unless im missing something.
Hmmmmmm....
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Nick
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#19 Re: Speaker Measurement - Where to Begin

Post by Nick »

The um2 has a 1/4" jack socket in the center of the XLR do should be ok Ant.
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#20 Re: Speaker Measurement - Where to Begin

Post by Ant »

Ta nick, didnt know that
Ill have to see if i can find that mic
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chris661
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#21 Re: Speaker Measurement - Where to Begin

Post by chris661 »

Yep, but I'd be very dubious of using any mic with a fixed cable and/or 1/4" jack as a measurement mic.
The Behringer ECM8000 is about as cheap as I'd go. Gear4Music also has their own brand mic available, for similar cash.


Ray, the UM2 you've linked will allow you to do some measurements, but if you've got the budget I'd recommend the UMC202HD. The latter has 2x proper inputs (not sure if the UM2's 2nd input is high-Z, which would mess up impedance measurements) and options for higher sample rates.

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#22 Re: Speaker Measurement - Where to Begin

Post by Ray P »

Ant wrote: Fri Jan 01, 2021 2:07 pm Hmmmmmm....
you'll be fine Ant, 1/4inch or XLR connector for Mic;

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#23 Re: Speaker Measurement - Where to Begin

Post by Ant »

Btw ray, i got the um2 from thomann and it took absolutely forever to arrive, because of a supply issue, that was back in august.
I notice on your link that it says out of stock so it may still have supply issues.

If i can find that mic ill have a faff with the behringer and see what i can get out of it.
If not, i dont mind sending it down to you if you want to borrow it
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Ray P
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#24 Re: Speaker Measurement - Where to Begin

Post by Ray P »

chris661 wrote: Fri Jan 01, 2021 2:34 pm Ray, the UM2 you've linked will allow you to do some measurements, but if you've got the budget I'd recommend the UMC202HD. The latter has 2x proper inputs (not sure if the UM2's 2nd input is high-Z, which would mess up impedance measurements) and options for higher sample rates.
Cheers Chris, but why would I need a second input and/or higher sampling rate for measuring speakers/room - I don't plan to get into any sort of recording or the like? Just trying to understand.
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#25 Re: Speaker Measurement - Where to Begin

Post by Ray P »

Ant wrote: Fri Jan 01, 2021 2:39 pm If i can find that mic ill have a faff with the behringer and see what i can get out of it.
If not, i dont mind sending it down to you if you want to borrow it
That's very kind of you Ant, I might take you up on that if supply is a problem.
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#26 Re: Speaker Measurement - Where to Begin

Post by chris661 »

Ray P wrote: Fri Jan 01, 2021 2:44 pm
chris661 wrote: Fri Jan 01, 2021 2:34 pm Ray, the UM2 you've linked will allow you to do some measurements, but if you've got the budget I'd recommend the UMC202HD. The latter has 2x proper inputs (not sure if the UM2's 2nd input is high-Z, which would mess up impedance measurements) and options for higher sample rates.
Cheers Chris, but why would I need a second input and/or higher sampling rate for measuring speakers/room - I don't plan to get into any sort of recording or the like? Just trying to understand.
Ray,
Good questions.

The 2nd input is required for impedance sweeps (mandatory for passive crossover design), and should have same input impedance & gain as the first input. The input gains are user-settable (just turn the knobs), but if the UM2's "instrument" input is high-Z, you're a bit stuck.

Sampling rate allows higher-resolution sweeps in REW (ie, more datapoints per sweep), which is fairly useful: you can also just set for a longer sweep and get the same effect. However, a single (long) sweep can take over 20 seconds at 48kHz, while switching to 192kHz gathers the same data in around 5s.
When you consider that it's good to repeat sweeps (I'd recommend minimum 2x sweeps, but have needed to use 8x before), the measurement times can start to stack up, which is why I'd opt for the highest sampling rate easily available.

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#27 Re: Speaker Measurement - Where to Begin

Post by Ray P »

Cheers Chris. Some follow-up questions if i may.
chris661 wrote: Fri Jan 01, 2021 3:09 pm The 2nd input is required for impedance sweeps (mandatory for passive crossover design), and should have same input impedance & gain as the first input. The input gains are user-settable (just turn the knobs), but if the UM2's "instrument" input is high-Z, you're a bit stuck.
So what would you plug into the second input?

I don't plan to get into passive crossover per se, I want to use this to get a reasonable response integrating a bass unit and full-range unit in an open baffle project, plus, I guess, subsequently measuring the in-room response.

I anticipate using a bandwidth limited amplifier for the full-range to avoid any additional crossover components - plan to roll-off the LF at around 180Hz by changing the amp's input filter - and then utilise something like a MiniDSP 2 way crossover to explore sorting out the bass unit integration and to then try to transfer that to an active line-level crossover (or maybe keep a MiniDSP if it doesn't compromise the SQ too much?). First requirement will be to measure the frequency response of the amplifier with just the full-range unit.

I'm not sure a second input is a requirement for my purposes?
chris661 wrote: Fri Jan 01, 2021 3:09 pm Sampling rate allows higher-resolution sweeps in REW (ie, more datapoints per sweep), which is fairly useful: you can also just set for a longer sweep and get the same effect. However, a single (long) sweep can take over 20 seconds at 48kHz, while switching to 192kHz gathers the same data in around 5s.
When you consider that it's good to repeat sweeps (I'd recommend minimum 2x sweeps, but have needed to use 8x before), the measurement times can start to stack up, which is why I'd opt for the highest sampling rate easily available.
As I don't plan to make a habit or career out of this I'm not unduly concerned about a few minutes of measurement latency here or there so I guess I'll just accept the sampling rate that comes with the device I go with.

Ta muchly
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#28 Re: Speaker Measurement - Where to Begin

Post by Nick »

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#29 Re: Speaker Measurement - Where to Begin

Post by Ray P »

Thanks Nick.
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chris661
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#30 Re: Speaker Measurement - Where to Begin

Post by chris661 »

Yep, that's what the 2nd input is for.

I made up the adapter by buying a pair of cheap guitar cables (1/4" jack to jack), cutting them in half and putting a resistor in there.

I do think impedance measurements are worthwhile if you might ever use a passive crossover.

Chris
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