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Silent Screamer 21st February 2012 04:44 AM

Test Equipment Recommendations Please
 
I need to start collecting some calibration equipment to test some new speakers I am building. Currently I am looking at the Earthworks Audio Measurement Series M30 microphone. I also need a 48v phantom power, does it matter what brand I use?

I need some test software so I am open to suggestions on what works well and reasonably priced. I also figure I need to use my laptop or one of my desktops sound cards. Are there any minimum requirements to work with this microphone / recommended software?

Really new to this side of speaker building and would like to buy the right gear first time. I would really appreciate any assistance you can offer.

gootee 21st February 2012 06:21 AM

You could try the free ARTA software suite.

I picked up a new Superlux ECM999 measurement mic on ebay, for a very reasonable price, after reading some reviews and looking at the frequency response and other specs.

Just to be able to play around with the measurement mic and ARTA, I bought a "TubeMP Studio" mic preamp on ebay, which also provides the 48V phantom power. I don't know how good it is but I got it new for about $40, last year. They seem to have several different TubeMP models on ebay, now.

I also got the necessary cables from another ebay seller. The TubeMP Studio has both three-pin XLR female and 1/4-inch mono female input jacks, and both 3-pin XLR male and 1/4-inch mono female output jacks. I used the 3-pin XLR input for the measurement mic's cable, with 48-Volt phantom power provided by the TubeMP, and used the 1/4-inch mono output so I could easily use an adapter on the other end of the cable for my soundcard input.

If you do some searches, you'll find that there are LOTS of good threads here at diyaudio about equipment and software for speaker measurements.

Regards,

Tom

Silent Screamer 21st February 2012 08:16 AM

Thanks for the advice Tom. I want a measurement microphone that comes with a calibration chart to dial out any imbalance in the microphone, so I need to look at something a little more upmarket.

I did look at the EarthWorks Audio ZDT 1021 but itís like $1300, between it and the M30 it is over $2000 with GST and freight, and while looking at the TubeMP you mentioned, I noticed the affordable phantom power supply only seem to go to 20kHz-25kHz, so perhaps I should be looking at the marginally cheaper M23 microphone ($459 + shipping) if I am not going to spend the dollars on the megabuck preamp?

I downloaded the user manual for the ARTA software (which by the way is 79 euro if you want to use all the features) and it was filled with math equations. Is there any software where I donít need a degree in math to use?

epicyclic 21st February 2012 08:30 AM

Hi
have you had a look at SPECTRAPLUS.com

pby 21st February 2012 01:14 PM

Quote:

Originally Posted by Silent Screamer (Post 2915842)
Thanks for the advice Tom. I want a measurement microphone that comes with a calibration chart to dial out any imbalance in the microphone, so I need to look at something a little more upmarket.

I did look at the EarthWorks Audio ZDT 1021 but itís like $1300, between it and the M30 it is over $2000 with GST and freight, and while looking at the TubeMP you mentioned, I noticed the affordable phantom power supply only seem to go to 20kHz-25kHz, so perhaps I should be looking at the marginally cheaper M23 microphone ($459 + shipping) if I am not going to spend the dollars on the megabuck preamp?

I downloaded the user manual for the ARTA software (which by the way is 79 euro if you want to use all the features) and it was filled with math equations. Is there any software where I donít need a degree in math to use?

Not sure what you mean by dialing out the imbalance in the microphone but if you were planning to EQ it out then doing so will most likely make measurements worse.

Also unless you have access to anechoic chamber there isn't much point dropping 2 grand on an earthworks as the measurements would be fairly meaningless without a treated room.

Preamp and ADC is just as important as the room and microphone. You may want to look at a solid state preamp over a tube preamp for measurement purposes. fmr has a great pre that has superb transparency that isn't too expensive.

The truth is theres no easy way to make meaningful measurements at home, and spending money on equipment without knowing the limitations is just wasting money. What exactly are you trying to calibrate?

Silent Screamer 21st February 2012 10:30 PM

Thanks pby I downloaded the pdf for the FMR Audio RNP8380 and will take a more detailed look at it tonight. I like his honest approach and at ~$500 is a little more palatable than $1300.
No I donít have a anechoic chamber, but I am looking to acquire test equipment that is not going to be dissatisfactory 5 minutes after I buy it. Experience has taught me not to skimp and have to spend twice.
So I am looking for something that is marginally better than middle of the road first time up. Not looking for over the top but donít want garbage either.

If I spend $1500 all up on test gear and I spend $10k on speaker parts, to me that seems like a reasonable balance to achieve the end goal of quality sound.
But I donít want to spend mega bucks on the speaker parts only to be let down by my test gear when it really matters.

Sorry if I havenít used the right terminology as I am fairly new to all this but I wanted a quality microphone that provides a calibration chart so any slight imperfections that are inherent in the microphone can be dialled out by including the discrepancy in the software to cancel the imperfections out, giving a neutral microphone (as far as the software is concerned). Earthwork provide a graph of the imperfections for $50 extra, so the detail can be provided to the software to counteract the microphone imperfection effect.

pby 22nd February 2012 11:38 PM

Quote:

Originally Posted by Silent Screamer (Post 2916956)
Thanks pby I downloaded the pdf for the FMR Audio RNP8380 and will take a more detailed look at it tonight. I like his honest approach and at ~$500 is a little more palatable than $1300.
No I donít have a anechoic chamber, but I am looking to acquire test equipment that is not going to be dissatisfactory 5 minutes after I buy it. Experience has taught me not to skimp and have to spend twice.
So I am looking for something that is marginally better than middle of the road first time up. Not looking for over the top but donít want garbage either.

If I spend $1500 all up on test gear and I spend $10k on speaker parts, to me that seems like a reasonable balance to achieve the end goal of quality sound.
But I donít want to spend mega bucks on the speaker parts only to be let down by my test gear when it really matters.

Sorry if I havenít used the right terminology as I am fairly new to all this but I wanted a quality microphone that provides a calibration chart so any slight imperfections that are inherent in the microphone can be dialled out by including the discrepancy in the software to cancel the imperfections out, giving a neutral microphone (as far as the software is concerned). Earthwork provide a graph of the imperfections for $50 extra, so the detail can be provided to the software to counteract the microphone imperfection effect.

I'm not entirely convinced this is the right approach. There are room acoustics/preamp/adc which isn't be accounted for. You cannot simply dial them out.

Unless you're prepared to go hire a chamber, budget equipment here will probably suffice for your needs. Behringer has a really inexpensive measurement microphone called the ecm8000 and you can just pair it up with a behringer mixer or preamp. While high end gear will give you more precise results, you would still be limited by the room acoustics. It would be a waste of money to spend it on mics and pres for you, as they can't correct acoustics.

Silent Screamer 23rd February 2012 12:01 AM

I guess what I am looking for the most precise measurement I can afford, it would be great to have an anechoic chamber, but all factors considered at the end of the day I will using the speakers in a real room where there are objects that will affect the sound output.

I am currently looking at an up market digital crossovers that can do room equalisation, so I figure as long as I can measure the room and speaker accurately, I am in a good place to dial out the environment to a certain degree.

The digital crossover have such infinite adjustability I can adjust the digital crossovers to suit the room conditions should I need to move them to another room.

If we were talking strictly passive crossovers I might think quite differently about things.

gootee 23rd February 2012 04:54 AM

I thought that the reason they called them "measurement mics" was that they have a flat frequency response, already. The plots I have seen for the model I bought were so flat that any imperfections will be totally-swamped-out by other measurement variations.

Silent Screamer 23rd February 2012 05:14 AM

Generally the better the quality the flatter they are, but just like a speaker none are perfectly flat so they provide a map of the imperfections so you can add it to your software, and the software artificially corrects the imperfections in the microphone by applying adjustment to the reading form the microphone.
The way I figure it the more perfect you can make the reading, the better informed you are to make a call on thing like applying adjustments to any dips in the response curve. If the reading says you high and you’re really low because of inaccurate equipment, you could potential tune an even greater problem into the speaker response.
Its the theory I’m working on I could be wrong but it makes sense to me...


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