Room testing on the cheap w/no computer

[awolski]

I apologize for a lot of questions but if anyone can help a diy'er get a clue I'll be really grateful.

I record on an 8-track digital portastudio and am setting up my basement mixing room. I am doing realtraps and insulation. I want to check my progress as I go along and also get to know my room's dips and peaks.

The only computer I have at home is a Mac (don't know what model...that tower with handles on all 4 corners..G4??), but with no sound card, just the tiny little stock speaker. My wife uses it for all kinds of teaching stuff so I won't be using it for audio any time soon. I'm trying to go around the computer approach so I figure these are my needs:

-some way to analyze the sound. I'm inspired by an old Tape Op review to pick up a Behringer DSP 8024 EQ with RTA. Plus I figure I can run mixes through the RTA and learn stuff.

-tones. I am stumped here. Is there a CD that has tones in 1 or a couple-HZ intervals? The 8024 makes reference noise but not specific reference tones. Is there any other cheap way to get tones? I was already considering a Peterson V-SAM for my tuning needs and noticed it generated tones in .01 cent intervals. Is this going to be enough precision? any way else?

-mic and pre. Behringer makes a $50 "reference mic" for their RTAs but I don't know if it's worth it. Do you think the 8024 takes the frequency response of this mic into account in displaying the RTA info? Or will a plain old MC012 w/omni capsule work?

Also, I doubt the 8024 has phantom power so I need to run the mic through a pre and I only have cheap tabletop pres such as the S.P. VTB-1. I imagine the pre will also affect my results, but how else would I get the signal into the RTA?

[Al_Huero]

In my very limited experience, doing a spectral analysis of a room is tough with budget gear--and I don't know that it's something worth dropping a bunch of dough on. My recommendation would be to get a boom box or stereo and stick it in the room around where you'll be mixing/monitoring. Put in a disc you're familiar with and then start walking around--listen near the walls, in the corners, etc. If you here swells and dips, well--that's what you need to try and treat for. If your room sounds completely flat under this approach--you'll be farther ahead than most. Bottom line is your ears can tell you a whole lot more than some spectrograph of questionable accuracy.

[Scodiddly]

You can download the "Binks test CD" - it's got a couple of sine sweep tracks, where a sine wave sweeps slowly over the whole frequency range. From there you could just plug a good mic (ideally an omni test mic) into a mixer or a mic pre and watch the VU meter while the sweep happens.

The Behringer test mic would work pretty well in this situation.

[awolski]

Well, I already have an Octava mc012 with omni capsule. I would think it would be as "flat" or more so than a $50 Behringer mic. But I noticed test mics have those pencillike tops with really small diaphragms, so maybe that's why the $50 mic might be better? I'm not going to go out an buy an Earthworks for this purpose

And if I just went the "preamp with vu meter" route, I assume to calibrate it I would get hold of a 1 khz tone and adjust the volume of my monitors and preamp gain so the VU meter reads at "0"? Then run the sweep and see which freqs. are above/below "0" to determine my response?

Thanks.

[trianglelines]

I found out some of my rooms modes by accident...

Using a electric piano and a Large Diaphragm Condensor with Omni pickup pattern, I recorded slowly going up the scale to see how it went to disk...

Some notes literally jumped out compared to others! It was very obvious.

Since it was piano, I was able to correlate back to frequency... Some rigid fiberglass helped curb the jumpy notes.

Could be all the more you need to know. If your room is not a big empty cube there aren't too many situations where you'll have a BIG problem-- home project studios have all kinds of 'charming' frequency quirks.

-TimT

[Scodiddly]

Well, I already have an Octava mc012 with omni capsule. I would think it would be as "flat" or more so than a $50 Behringer mic. But I noticed test mics have those pencillike tops with really small diaphragms, so maybe that's why the $50 mic might be better?

Well, the Oktava is more designed to sound good, while the B is designed to be accurate. But hey, the TapeOp DIY omni is a good test mic (it's what I use!) for cheap.

And if I just went the "preamp with vu meter" route, I assume to calibrate it I would get hold of a 1 khz tone and adjust the volume of my monitors and preamp gain so the VU meter reads at "0"? Then run the sweep and see which freqs. are above/below "0" to determine my response?

Yup. The Binks CD has various test tones along with the sweeps. Well worth [badgering a friend with broadband into] downloading.

[knmy]

I've heard good things about the Audix TR-40 and Superlux ECM999. Haven't tested them myself but the Superlux can be had for about $100.

[Ethan Winer]

AW,

> some way to analyze the sound <

You're already getting good answers, so I'll add only this:

Room treatment is useful for flattening the frequency response, especially at the low end, but that's only half the story. Just as important is killing echoes and first reflections, and reducing the reverb time. To measure those requires more than just sine wave frequency response tests. I use the ETF software, but it's for PCs only. I'm pretty sure there's something similar for Macs. You could also hire someone for a few hundred bucks to measure as you install your MiniTraps.

That said, I think the improvement will be very obvious just listening by ear!

--Ethan

[lovecow]

Dear fellow Pole ,

I may have some contacts for you in the Chicago area that could help you with this. PM me if you're interested as I don't like posting people's contact info out w/o them knowing.

[awolski]

Thanks everybody. I will consider these points well.

Ethan - now that you came out and referred to them by name instead of my sneaky "realtraps" mention I'll say that I can already hear a difference with the Minitraps just sitting on chairs, not mounted yet.

Lovecow - I am not quite ready to enlist professional help yet (at least with my sound ) but I will keep that in mind for future use and if I know anyone else that needs help.

I think the "listen to things" responses are helpful too and I think that's where I need to start my explorations.

[Flight Feathers]

You can download the "Binks test CD" - it's got a couple of sine sweep tracks, where a sine wave sweeps slowly over the whole frequency range. From there you could just plug a good mic (ideally an omni test mic) into a mixer or a mic pre and watch the VU meter while the sweep happens.

any idea where i can get this cd? google came up with nothing.

[b3groover]

http://www.binkster.net/extras.shtml


BTW, if anyone is lacking a broadband connection, I's be happy to send you a copy of the CD for say $3 sent via Paypal or something. Just enough money to cover postage and the cost of the blank.