Easy way to measure in-room response?

[echrisconnor]

Is there an easy and cheap way to measure in-room response? It seems to me that it could be done with Speaker Workshop or other such software, and a mic, but I don't know if this is the best/easiest way. Nor do I know how to actually *do* a FR test.

Let's assume that the person trying to do this (me) has:

* A PC
* The ability to download and install free software
* A fairly standard (non-duplex) audio card -- at least I don't think it's duplex, it's just my on-board audio.
* Speakers & amplifier which can be connected to the PC
* A cheap mic
* about $50 bucks for the project for software, a mic, cables, beer, or whatever.

Is is possible to do this with some accuracy or should I just trust my ears?

/chris

[Dirk]

I would use Room EQ Wizard. It's free (as in beer). It's available here. You have to register with Home Theater Shack to download it, but that should be no impediment.

BTW, you'll need to add an SPL meter to that mix of equipment to do it right.

[echrisconnor]

Hey, that looks like a nice piece of software. Is is specifically for Bass though? I'll read some more but here are a couple follow-up questions:

1. Is the SPL meter required just to estabilsh a baseline of effeciency/output level? If i'm more interested in what is "flat" is it required?
2. Will a crappy mic work for this, or should one really invest in something .5 way decent?

Thanks,

chris

[jdclark]

Hey, that looks like a nice piece of software. Is is specifically for Bass though? I'll read some more but here are a couple follow-up questions:

1. Is the SPL meter required just to estabilsh a baseline of effeciency/output level? If i'm more interested in what is "flat" is it required?
2. Will a crappy mic work for this, or should one really invest in something .5 way decent?

Thanks,

chris

Im in the same boat on the mic. I have gotten one program or another to actually do something, but it doesnt pick anything up untill like 200 hertz or so. Im not going to tell what mic I used....lets just say it came with a computer. (no its not built in).

[dubbreak]

Unless your computer is ancient I'm willing to bet the onboard sound is full duplex. What is questionable is whether it adds eq to the line in.

I'm pretty sure there are some free versions of MLS or RTA software (trial or whatever). Do you have a little mixer? If so you'd just need a mic (ecm8000)and that would pretty much fit the budget ($49 before delivery).

[echrisconnor]

Well the computer is pretty new, so you may be right that it's full duplex. I don't have a mixer and was going to ask whether the mic you recommended would be the best option since all the really crappy mics only have FR of about 70 - 13k

http://www.parts-express.com/pe/show...number=248-625

However, this mic requires phantom power and looks like it's XLR out... I suppose I can get an adaptor to 1/8" and go straight in to the card??

Any other software suggestions?

Thanks,

Chris

[Dirk]

Get the $30 Radio Shack digital SPL meter. Not only does it work as an SPL meter, but it's got a line-out that is suitable for use with measurements. Needs no additional preamp or anything. It's far from perfect in its linearity. I wouldn't use it for hardcore speaker design work, but there's a calibration file available for it that will at least get you ballpark (within a dB or two) for your needs.

RoomEQ does more than bass. MUCH more. It's just that bass is what most people use it for.

[jims]

Well the computer is pretty new, so you may be right that it's full duplex. I don't have a mixer and was going to ask whether the mic you recommended would be the best option since all the really crappy mics only have FR of about 70 - 13k

Speaker Workshop has a utility to determine whether your sound chip is full duplex. It probably is. Also, you could try looking for the name of the chip in the computer documentation you may have, and look online for the specifications (maybe on the chip manufacturer's page).

There is a discussion of using a Panasonic electret element (less than $5 at Digikey ) as an audio mic here on Eric Wallin's site: http://mysite.verizon.net/tammie_eri...2/preamp2.html

These mics are said to be pretty accurate, although for best results it should be calibrated. There are also generic calibration curbs for this type of mic posted on-line, which should get you close. I'll look later if you're interested....

You don't necessarily need to build the pre-amp described in the link. A simple mixer might do it. You can power the mic using a 9-volt battery and a couple of resistors. Eric has a diagram of that on one of his other project pages, or you can google it.

Jim S.

[echrisconnor]

This might be a good tool... the SPL meter from Rat Shack. It looks like it does have a signal out too, so you may be on to something. No money left over for beer, thanks for this recommendation:

http://www.radioshack.com/product/in...es&tab=support

So pair this with the Room EQ Wizard as a Mic and SPL reference and we may have a solution?

[brianpowers27]

If you are a laptop user, you may want to consider finding a used external sound interface. (usb/firewire) These often have phantom power as well as relatively clean preamps. I have the advantage of measuring speakers in outdoor environments etc....

I use a m-audio firewire solo. THere may be cheaper options.

[MerlinWerks]

The quality and feature set of REW is amazing for a free program, excellent support community as well.

[dubbreak]

Well the computer is pretty new, so you may be right that it's full duplex. I don't have a mixer and was going to ask whether the mic you recommended would be the best option since all the really crappy mics only have FR of about 70 - 13k

While the mic is cheap it used a lot in DIY for RTA. I think it has a rising topend but is pretty flat other than that. There are generic calibration files available that would get you into a good ball park. Yeah it needs phatom power, but even the $50 behringer mixers have that and there are other options to get around that (battery pack). I bet with something to provide phatom power no preamp is needed. Most mics I've used that need phatom power send a pretty hot signal. Your sound card should be able to get a clean enough signal off the mic alone.

[echrisconnor]

Thanks for all the responses. Here's what I think I'm going to try in the interest of simplicity and frugality. I think I'm going to buy the $50 R-Shack SPL meter. I'll use that as my mic and try the Room EQ wizard. If it all works out, I'll let you know. If I end up needing a better mic, then I'll still have the SPL meter as a toy and may get the Behringer one and rig simple power for it and see if I can get away without preamp.

Thx all!
c