Will this work?

[adamt]

Okay, I've been reading up on how to do measurements and the equipment typically used to do so. This may be a bit premature since I really don't have the room setup nor do I have all my equipment yet, but I thought I'd get this cleared up in case I need to purchase some additional equipment. I have a pretty decent collection of recording gear that I use to make music and was wondering if this setup would work for taking room measurements.

Sure sm81>mic preamp>usb audio interface>computer

It would be nice not to have to buy anymore equipment as it pretty much consumes my entire estate but I'm always down for buying new stuff.

Here are links to all the equipment in my proposed line.
http://www.shure.com/ProAudio/Produc...M81-LC_content
http://http://www.artproaudio.com/products.asp?type=79&cat=1&id=58
http://line6.com/toneport/index.html

It seems like a lot of stuff to catch interference but if it will work I can go home and start practicing. My BFD2496 should be here any day but the rest of the gear will be awhile. I would like to start fooling around with this so I will have a leg up when it comes time to really get at it.
Thanks for any advice
Adam

[Wayne A. Pflughaupt]

Hmm... The Shure link is the only one I can get to open.

Any measuring will only be as good as your equipment. Since only the most expensive equipment is truly flat, calibrations are needed to compensate for the inadequacies inherent to the relatively inexpensive equipment we use for REW.

The REW software can calibrate itself for any suitable sound card. However, your mic of choice is a problem. Did you look at its frequency response?

Shure specs it at rolling out at 6 dB-octave below 100 Hz, with the rumble filter set flat. IOW, your readings are going to be down more than –12 dB at 20 Hz.

Obviously, no mic is perfect. We have available a calibration file for the common Radio Shack SPL meter most of us use. I understand it’s possible to create a mic calibration file for REW, if you know the response characteristics of the mic. It would be a bit “iffy” to do that given the rather coarse resolution the Shure graph uses, but it’s possible you could create a calibration file for the SM-81. Other members here more familiar with what that entails can tell you how.

As noted, I couldn’t open the link for the USB interface. The soundcard you use has to be full duplex; if your interface has that capability, you can use it. The REW Help Files can show you how to calibrate it.

Regards,
Wayne

[adamt]

Well, it seems to me that my equipment is probably not the best suited for this application.
What is the best alternative to get this nipped in the butt. Perhaps I will have to get one of the SPL meters suggested in the BFD thread.
It just seems to me that I will only use this piece of equipment a few times and it will then become some kind of new age paper weight. I am using onboard sound on all my computers. My receiver has burr brown dacs so I let it do all the processing, I use the toneport for an external soundcard on my DAW so I haven't found a whole lot of justification for an aftermarket soundcard.
140 bucks seems kind of steep for something like this but I guess if that's what it takes.,.

[brucek]

What is the best alternative to get this nipped in the butt

You require a meter or microphone that has a calibration file associated with it. Nothing else will do really. It would be meaningless to use REW without a calibrated meter that can measure down to 15Hz...

The cheapest (and least accurate) method would be to use a Radio Shack meter.

brucek

[adamt]

So I went ahead and took a shot at doing some measuring with my little setup that I mentioned before. It was horrible. In order to get everything calibrated with REW I had to turn the volume up so loud it was unbearable. The pink noise wasn't so bad but the 1khz test tone drove me bonkers at that volume. And the wooman flipped out so I'm actually feeling a bit propelled to purchase a decent spl meter in hopes that I won't have to crank it up so loud just to do a couple of measurements.

I'm sure the calibration files are somewhere on the net but to save myself the trouble I think I will look for a piece of equipment that is listed on the REW page.
Any suggestions to which I should get?

[brucek]

Any suggestions to which I should get?

Galaxy CM-140 is your best bet for subwoofer equalizing.... we have the calibration file on our download page.

If you wanted full range, you would need to step to an ECM8000 and preamp setup...

brucek

[adamt]

Thanks for the prompt reply. I have found quite a few of the galaxy cm140's for 100 bucks. It appears that my BFD finally arrived in the mail today. I still haven't been able to talk the Mrs into letting me have the 800 bucks I need for Bonehead's sub so it will have to wait until september. I hate waiting. I'm really into instant gratification. In the mean time I will get both measurement tools and play around with them for the next month.

One more question. How do I find out whether my soundcard is full duplex? That is a term I'm unfamilar with

[Otto]

adamt wrote:

One more question. How do I find out whether my soundcard is full duplex? That is a term I'm unfamilar with

Full duplex means that you can "communicate" in both directions at the same time -- like a telephone. A walkie talkie is one direction at a time, and is "half duplex."

Applied to a sound card, it just means that you can play a tone via the "line out" path while recording on the "line in" path. I'm not sure of a way to determine that status without testing it. It may say in the manual somewhere. You can test it by playing audio and recording at the same time. Even with the mic you have, you could set it up to do the sweep and see if you can record the result. If so, you're good to go.

[adamt]

Once again thanks for the prompt reply.
Here is what the mobo manufacturer has to say about the on board audio, just curious if any of these terms apply to another description of full duplex? I won't be able to test it for awhile because I am in the process of changing the processor cooler and I have to take the mobo completely out and switch the back plate Not looking forward to it at all but perhaps this will put some fire under my ***

ADI 1988B 8-channel High Definition Audio CODEC
Support Jack-Sensing, Enumeration, Multi-streaming and Jack-Retasking
Coaxial, Optical S/PDIF out on back I/O port
Support DTS® Connect function

[brucek]

Most all sound cards are full duplex. I'm sure it's fine.........

[adamt]

I'm going to go fix my computer right now and see if I can't do something with it. I got my bfd today so I'm going to go play with it too even if I can't hook it up to anything yet.