Acoustic Measurments (Mic/PreAmp/Ect)

If you don't want to buy a measurement mic you can use your omni mic for now to get an idea of what's going on with you room but if you're really serious about measurements, you'll want a measurement mic. IIRC, Ethan has pointed out measurements are not absolutely necessary to get a good sounding room if you follow his general principles. That said, you can verify your setup, troubleshoot problems and fine tune your room with the help of measurements.

I have seen measurement mics that are USB. I just got a flyer from parts-express.com they have a usb mic for $70 #390-808 and an XLR for $50 #390-801 I'm not endorsing these products (I have not used them but they are probably fine), I'm just pointing out these things are out there.

As far a signal chain, I don't think it will make any significant difference either way. Your measurement levels should be well above the noise floor of your system...if it's working correctly:)


You wrote: "I also have some XLR-USB cables, but I think those only work with dynamics." 

Regarding the above: dynamic mics are analog and USB is digital so you will need an A/D converter between the mic and your computer...and a preamp in there somewhere too. 

Sorry, I didn't know an XLR to USB had an A/D, makes sense that it does... but I don't need/have one and I'm not the expert here, I'm just a member like you except I hang out here more than you do. BTW, if you want to know more, read ALL the posts here, not just your own, you will learn a lot more than concerning yourself to your own issues. If everyone did, there would be MANY LESS questions asked! But that's OK, we like to talk about acoustics and that's why we try to answer your questions.

I also don't know about your EQ circuit but you should be able to bypass it, no? If you can't, why do you have a preamp that is not linear? Maybe you want/like the coloration? Nothing wrong with that. But yes, in that case, probably not the best for measurements...but if the coloration is subtle...and all your measurements are through the same path, it probably won't make much difference. If you have read Ethan's material, you'll know if you get your room to within +/- 10db you'll be doing as good as most rooms will ever get.

No problem.

The EQ circuit is a standard part of the pre-amp circuit. The only way to "bypass" it would entail opening it up and taking a soldier gun to it.
And most pre-amps have EQ circuits, ones without are the exception by far. The only one I can think of myself is a Neve 1272.

An EQ you can't bypass? What are you talking about? What is your converter make and model? If you have the manual please send it otherwise I'll search and download it myself just because I can't imagine a preamp that won't. BTW, if there is no actual "BYPASS" button on the EQ, do you do know that setting the controls to zero, AKA "flat", will effectively eliminate the effect of the EQ?

Ok so you're concerened about the EQ in the preamp messing up your readings?

Forget it. SPL isn't everything so 1-2dB off is fine especially if you don't touch the EQ to change it. Remember you're using a mattress as treatment so let's put everything in perspective. This isn't going to have much if any effect on the decay reading. Yes, EQ introduces ringing but this is going too far down the rabbit hole.

I understand your concern but you're looking for relative improvent. Nulls can be 30dB or so and very narrow. You have what's probably a low and high shelf. I'd say just get a cheap omni and move on.

Thanks for the download. Just leave the Bass and Treble controls at 12 o'clock and forgetabuotit. Yes, you are over thinking it. Hexspa's advice is right on too. 

All I can say is that others have tried to take measurements with mics other than omni linears and then wonder whey their graphs don't make sense.