Help me turn my Laptop in to an RTA

[vlad335]

I was looking into this myself last year and all the research just made my head spin. Bought the Behringer DEQ 2496 and was done with it.

[Bill Fitzmaurice]

You need software, microphone and pre-amp w/phantom power for the mic. When you consider that a DEQ2496 or the equivalent does RTA and EQs the system too it's hard not to justify one.

[Tim A]

I was looking into this myself last year and all the research just made my head spin. Bought the Behringer DEQ 2496 and was done with it.

+1. By the time you get through with buyng all the separates, the Behringer makes a lot of sense.

If you're of the "I hate Behringer" camp, The Driverack PA will also do the trick, and I think the new PV will as well. There are other offerings but they can get into some real $.

[Bill Fitzmaurice]

So the DEQ would appropriately display and test response curves for the THTs and ensuing OTops?

Yes, though it's almost impossible to do anything below 100 Hz indoors with any RTA, as room modes define response. Testing and calibration of subs has to be done outdoors. On site you can use the RTA to indentify room resonance peaks and suckouts below 100Hz, though, greatly aiding in placement and fine tuning.

[gdougherty]

So the DEQ would appropriately display and test response curves for the THTs and ensuing OTops?

Yes, though it's almost impossible to do anything below 100 Hz indoors with any RTA, as room modes define response. Testing and calibration of subs has to be done outdoors. On site you can use the RTA to indentify room resonance peaks and suckouts below 100Hz, though, greatly aiding in placement and fine tuning.

+1 I can't imagine life without my DEQ. For some reason I have a hard time quantifying 3-6db louder when setting the polarity of the subs on my DCX, being able to see the dip go away as I change it helps imensely.

[Les Webb]

The DRPA doesn't come close to comparing to the DEQ IMO. The DEQ compares to the DR260.

I really don't like the DRPA.

Just my $.02

[Mark Coward]

IF you already have a decent mixer of some type, with phantom power, you can plug a measurement mic into this and out from the mixer to your laptop's input. All you'd need to buy is a measurement mic, and you would need to buy this separately anyway if you get a DEQ2496. The Behringer mic works quite well and is inexpensive. You could download the free or trial versions of TrueRTA, SMAARTLIVE etc.

[jbell]

I use spectralab 4.3.2, google for it and you'll find it. A behringer reference mic, art preamp with +48 phantom power, sb mp3+ usb sound card. I also have ETF, but prefer the spectralab.

The usb sound card is almost a must, most laptops have crappy sound cards..

get a spl meter, spend the $20 bucks, RTA's are great, but where your goal is to pound... A spl meter and test tones would get you about 80% of where you want to go...

[Sydney]

spectralab 4.3.2,

It's now v5 and starts @$295 and goes to $995 with all options
The ETF full enhancement package license owners (add $150.00 to basic $150.00 price).
Both are out of my "hobby fund" range, but I am curious why you favor the Spectralab 4.3.2
Considering that the full TrueRTa is $100: What do these other packages offer?

The usb sound card is almost a must, most laptops have crappy sound cards..

Indeed, most OEM soundcards in desktops PC are inferior to even a Soundblaster.
RE: External Sound Cards: I have been keeping eye open for a "deal" on an external:
Some of the recommendations I have seen are:
Emu 0202 USB 2.0 Audio Interface
Sound Blaster Audigy 2 Zs Notebook - CREATIVE LABS - 70SB053002006
M-Audio Transit USB Mobile Audio Interface
Anyone got feedback on these or other interfaces for testing?

[jbell]

4.3.2 spectralab didn't cost me a thing at the time... That's the reason. The big reason for spectralab is time domain.. AKA, I don't have to pay for tef, smaart or mlssa.

The creatitve usb mp3+ usb is the preferred sound card for ETF, as it has stereo line in and out that are both active, and you 'loop' "out to in" on one channel, and ETF balances out anything that isn't perfectly flat in the sound card. You can find them on a regular basis on ebay or other discount electronics places for about 25-30 bucks.

I picked up the art micromix for about 35 bucks at the time, and it's dead quiet, and you can battery power it, to make sure you are absolute noise free.

The combination of the 2 give you way more than 100db of noise floor, best bang for the buck I could find at the time.

On RTA, Not sure if we're talking the same company. Anyway, here's the free link to download just the RTA portion of spectralab.

http://www.soundtechnology.com/download-center.htm

[Sydney]

Thanks jbell
I'm guessing this is what you are referring to:
http://www.soundtechnology.com/RTA132v15.EXE
I was looking at this:
http://www.etfacoustic.com/RPlusDSite/index.html
* BTW I noticed this on that page:
"now includes emulation of the Behringer DCX 2496 loudspeaker management system."

Someday I'd like to see a full range of test measurements on the BF line, on the level of John Atkinson ( using MLSSA or equivalent ) ; BTTBOMK There is no competent, independent test lab for sound equipment.
I also haven't seen a cross-evaluation of the various test software, or compromises ( if any ) for using a lower cost device like the creatitve usb you mentioned vs a more expensive 24bit/192khz card. If, for instance, there was an accuracy difference.

On a related note, from a Bill Waslo reply ( AudioXpress 4/08 p 40: )
he recommends soundcards with Analog Devices "SoundMAX" chipset

This might be helpful and it's free:
http://www.libinst.com/Audio_DiffMaker_ ... nstall.exe
from http://www.libinst.com/Audio%20DiffMaker.htm

[WB]

I'm taking mental and physical notes on all this info. Some day, not now though, ... to many things on the go.

I found this line an interesting switch for once:

"now includes emulation of the Behringer DCX 2496 loudspeaker management system."

Somebody copying, oops, emulating Behringer.

[vlad335]

I found this line an interesting switch for once:

"now includes emulation of the Behringer DCX 2496 loudspeaker management system."

Somebody copying, oops, emulating Behringer.

LOL. That is pretty ironic.

As far as the DCX and DEQ units are concerned. Are these particular units copies of any particular gear? For instance, the Europower amps are very simular to the QSC RMX series amplifiers and Behringer has a bass head thats pretty much a dead ringer for an Ashdown unit. The DCX and DEQ seem to be actual Behringer designs.

[Sydney]

In addition to "emulating", there are efforts to modify the DCX and the DEQ
Including replacing the original operational amplifiers (NJM4580) used for the single analog stage with an LM4562.
( When I suggested tweeking these Behringer units - the idea was quickly dismissed... I'm hoping to come across one of these units ( with one of the reported "bugs" ) that someone sells cheap - then I'd have a go at a POOGE ).
* FWIW I don't know if this is a valid generalization for ALL soundcards for All testing software or just PRAXIS.
On Waslo's FAQ page about Praxis software:
He stated that a soundcard should be:
"True full duplex at 16 bits (24 bits also supported), stereo mode
and that 192kHz sampling is supported only by Windows XP SP1"
"With 24bit cards (such as Waveterminal 192X, CardDeluxe, M-Audio 410, 1010 or Audiophile 2496, or Lynx L22) you could measure to lower distortion residual level for electronics. But for loudspeaker work there is no real advantage to 24bit operation (you'd never find an environment or microphone with enough dynamic range or low enough distortion to make use of the additional bit resolution)."
"If you want to measure above the normal audio band, a 96kHz sampling card will allow you to get to about 40kHz. A 192kHz card (such as the Lynx L22 or Waveterminal 192X) will allow measurement to 80kHz, though the higher frequencies will be subject to increased crosstalk."

So maybe a cheap 48khz is all that needed?

[lilmike]

Back to Wi's original question:

Yes - a basic laptop can do most of what you need with free software

Windows Based software:
ARTA (demo is free)
Praxis (demo is free)
SynRTA (free - like free beer RTA software)
http://www.libinst.com/SynRTA.htm
freqresplot (free - like free beer swept-sine tool)
http://www.pensa.fr/freqresplot/indexe.htm

Here's my setup:
Dell Latitude D600 Laptop (already had it)
Sound Card - Emu 0202USB ($80) - Recommended by Liberty Instruments site
Microphone = Panasonic WM61 capsule ($2) - Digikey
Meter/Preamp = RS Analog #55-2050 SPL Meter ($15 on Ebay) with response modifications as detailed on the net. (another $10) - Digikey
Cables and other stuff - another $10 or so

@wi - you could probably just plug a Behrenger ECM8000 mic and your laptop into your mixer and skip the meter/sound card/mic parts - IIRC PE sells the mic for about $50, though they are often cheaper elsewhere. Once it is all set up, plug in your mixer and PC, set the levels, record the response, adjust things, repeat as needed....

So - for about $120, a little bit of time, and my laptop, my setup works well enough for me. The Panasonic mic capsule I use is reportedly +/- 1 dB from 20-20K Hz, which is plenty accurate for me, correction files are available if needed as this mic is widely used. The rest of the electronics are flatter.

Now I can make real measurements and get my speakers placed and crossovers adjusted so that there are no glaring steps or holes in the response. I can not measure absolute SPLs with this setup (which do not really matter to me) as my mic is not calibrated. The swept-sine software works great for the bass frequencies, a measurement takes a minute or so unless I set the resolution really high.

Feel free to shoot me a PM if you need details about the software or setup.

edits - dropped one "i" from wi - sorry, added link to synrta