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Old 24th January 2006, 04:35 AM   #1
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Default Need some guidance on measuring speakers

Iím looking for a little help with measuring my speakers. My measurement knowledge is very little so bear with me

I currently have a Behringer DCX2496 and DEQ2496 hooked up to my line arrays. I purchased the Behringer ECM8000 microphone and used it in conjunction with the DEQ2496 to do the AutoEQ function. The results were good, but Iím looking for much more accurate measurements. The line arrays are sealed with ten Vifa 4.5Ē buyouts and a single Fountek JP-2.0 tweeter. Iím also in the process of building a pair of Orion clones, using Dayton RS series instead. The DCX2496 and DEQ2496 will eventually be hooked up to these speakers, and who knows what Iíll do with the line arrays. Hopefully I can build a passive crossover for them and give them to my brother, with the aid of some new measurement capabilities.

With that, Iíve been doing a little bit of research and was thinking of purchasing TrueRTA with 1/24 octave capabilities. While at the Parts Express show this year I got a chance to watch Darren Kuzma use his CLIO setup, and we were able to use my DCX2496 on his line arrays and measure them in-time, changing the crossover points, slopes, EQ etc. For most of the measuring Darren would play a quick burst of sound and it would display the frequency curve on the computer screen. Only once or twice did we use the RTA function of CLIO. Iím not sure which is better?

Anywho, I really liked how easy it was to use the CLIO with the Behringer equipment and was looking for something like that as well. I will be going fully active with the dipoles Iím building so I donít think I need measuring capabilities for a passive speaker, even though Iíd like to be able to build passives down the road.

Do you guys have any suggestions on what I should look into? Iím fresh out of school and just got a decent job so Iíd like to keep it under a few hundred dollars. I know Iíll be needing a new soundcard (probably an Audigy2, or maybe even an external for my laptop) and a phantom source for the ECM8000, so donít worry about that price affecting the budget.

Thanks for any input you guys can give me. I really appreciate it!
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Old 25th January 2006, 02:09 AM   #2
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Anyone?
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Old 25th January 2006, 04:46 PM   #3
opp is offline opp  Denmark
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Audigy is not the ideal soundcard for measurement Ė speaking from experience.

Go for the professional types like the Sound Blaster owned E-MU.

Speaker Workshop is of course a possibility, free, working very well, but also a challenge.
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Old 25th January 2006, 04:56 PM   #4
MBK is offline MBK  Singapore
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My 2 cents:

You could get Audiotester, shareware at http://audiotester.de/ for something like 30 Euros. It will do real time and MLS, plus all sorts of other things. Few quirks and not much of a learning curve, though not as refined as the pricier programs. Of those, Liberty Praxis seems to have quite some following now. But Audiotester can do what you describe, and get you started with your existing hardware.

For soundcards I would not recommend Creative cards, many ppl report problems (drivers, unreliable specs etc) and I myself also have crashes with my Soundblaster live. But I have an external USB M-audio Pre as well, which does the job and does it well, and cooperates with Audiotester.

The real issue you will face is not the software, or the mic accuracy - those are AFAIK mostly pretty OK. And you will get scientific looking curves, and they will sometimes look quite ok too. But not always: The problem lies in the various measurement techniques and trade-offs, how to read the data, and how to reconcile seemingly inconsistent results that you get when using different methods (say, at 1 m distance and 1 m height on axis vs. 2 m distance, listening height, and 30 degrees off axis etc).

Accurate estimates from measurements usually take a combination of approaches and mental integration of the results. I suggest looking at the various methods Siegfried Linkwitz uses to measure his speakers for instance (http://www.linkwitzlab.com ), to give you an idea.

The most serious problem is the lack of reflection-free and quiet measurement envrionment. Windowing creates artefacts and will only get you down to the lower 100's of Hz. Measuring mid-bass and bass accurately, including floor effects, and finding a place with no low frequency hum is a real challenge, for me at least. And in the high frequencies, regardless of windowing, you will have strong diffraction effects from the baffle that change significantly with angle , height, and distance of measurement. In fact research suggests one should measure at distances significantly greater than the speaker's dimensions. This may mean 3, 4 m away, and then S/N ratio becomes an issue.

Bottom line, while I sometimes wish I had more goodies than Audiotester provides, it is really a clean measurement environment that I need most, especially for the bass, and not more software ;-) .
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Old 25th January 2006, 05:19 PM   #5
opp is offline opp  Denmark
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Quote:
it is really a clean measurement environment that I need most, especially for the bass, and not more software ;-) .
Thatís also my experience Ė but on the other hand the important xo areas can be measured quite satisfactory. But donít forget; the ear is the final judge, measuring maintains a steady course during development.
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