Measuring with HOLMimpulse and REW

sts9fan · « **on:** 29 Mar 2011, 01:25 pm »

So I now have a M-Audio Moblie Pre and a cross spectrum mic. I have attempted to get up and running with no luck. I was following a thread on AVS Forums on how to work things but mine is not meshing.
I am having a hard time out the gate getting the loop back cal done. The input device does not show my mobile pre but "mic in" or something. The output does have mobile pre. When I press make I always get either "signal -60ish db too low" try again or no signal. I have played around with the volumes with no luck. Any suggestions? Yes I do have the 1/4" mic looped.
Anyone know the easiest free software I can ge my feet wet with?

JohnR · « **Reply #1 on:** 29 Mar 2011, 01:26 pm »

Do you want to try REW first off?

sts9fan · « **Reply #2 on:** 29 Mar 2011, 02:24 pm »

I have no idea. Is it easier? I just need to get rolling with software. I am confident in my ability to learn once I get going because this is not so different analytically to what I do for a living. I will download REW tonight.

poseidonsvoice · « **Reply #3 on:** 29 Mar 2011, 02:27 pm »

Quote from: sts9fan on 29 Mar 2011, 01:25 pm

So I now have a M-Audio Moblie Pre and a cross spectrum mic. I have attempted to get up and running with no luck. I was following a thread on AVS Forums on how to work things but mine is not meshing.
I am having a hard time out the gate getting the loop back cal done. The input device does not show my mobile pre but "mic in" or something. The output does have mobile pre. When I press make I always get either "signal -60ish db too low" try again or no signal. I have played around with the volumes with no luck. Any suggestions? Yes I do have the 1/4" mic looped.
Anyone know the easiest free software I can ge my feet wet with?

Make sure you have downloaded the M-Audio MicPre software for your operating system. You should have an icon in the lower right hand corner of your PC that represents this. Or else I haven't seen REW recognize that M-Audio is your external mic preamp. I haven't played with HOLMimpulse yet but I am planning on it, judging by Jtwrace's results. He may chime in here with his experiences as he uses a similar mic preamp and the Cross Spectrum ECM-8000 like I do.

Best,
Anand.

sts9fan · « **Reply #4 on:** 29 Mar 2011, 03:40 pm »

Also, what do you use for a freqency sweep? I have an audio file from RealTraps. Or are there special files?

Russtafarian · « **Reply #5 on:** 29 Mar 2011, 07:36 pm »

I built a simple loopback cable for my laptop's analog I/O to use with REW.

I took a short stereo minicable (3.5" TRS), cut it in two and spliced ring to ring and sleeve to sleeve for right channel loopback. Tip and sleeve on the send (output) side are spliced to a cable that connects to the system input for test tones. Tip and sleeve on the return (input) side are spliced to a cable that goes to an analog mic preamp & behringer measurement mic. The two plugs are marked "mic" and "phone" to match the laptop labels for easy hookup.

Kind of a pain to build, but it's easy to hook up and use.

JohnR · « **Reply #6 on:** 29 Mar 2011, 11:19 pm »

Quote from: sts9fan on 29 Mar 2011, 03:40 pm

Also, what do you use for a freqency sweep? I have an audio file from RealTraps. Or are there special files?

The measuring program will generate it in real time.

Give REW a try first if you're not having any luck with HOLMImpulse.

sts9fan · « **Reply #7 on:** 30 Mar 2011, 01:58 am »

Ah. I guess I need to hook the computer to the system.

JohnR · « **Reply #8 on:** 30 Mar 2011, 02:39 am »

Yep.

(Adapt to suit situation.)

Tyson · « **Reply #9 on:** 30 Mar 2011, 04:17 am »

For Holm Impulse (which I use a lot), make sure it's actually producing a signal before trying to do the loopback-calibration for your mic preamp.

Just hook up your mic to the M-Audio (I use the Channel 2 input and output on the M-Audio). And hook up your M-Audio to your stereo's preamp. You are now ready to generate some signals and do some measurements.

One tip I've learned - in Windows, right click on your volume control in the lower right of your computer screen. Set the M-Audio Mobile Pre as the default for both "Sound Devices" and "Recording Devices" BEFORE you open up HolmImpulse. This should let Holm default to the M-Audio as the primary sound producer/recorder. That makes things simple.

Once you open Holm, click on the Device & Signal tab and make sure that M-Audio is selected in both the "Input Device" and the "Output Device". Then click on the "Measurements" tab and click on any of the 3 "Measure" buttons on that page. Verify that you are getting sound from your speaker and that HOLM is able to read it.

sts9fan · « **Reply #10 on:** 30 Mar 2011, 12:13 pm »

Thanks Tyson that is a great idea. I was getting hung up on the loop back when I should make sure everything else is working.
Thanks John for the diagram.

Russellc · « **Reply #11 on:** 30 Mar 2011, 01:25 pm »

Quote from: sts9fan on 29 Mar 2011, 01:25 pm

So I now have a M-Audio Moblie Pre and a cross spectrum mic. I have attempted to get up and running with no luck. I was following a thread on AVS Forums on how to work things but mine is not meshing.
I am having a hard time out the gate getting the loop back cal done. The input device does not show my mobile pre but "mic in" or something. The output does have mobile pre. When I press make I always get either "signal -60ish db too low" try again or no signal. I have played around with the volumes with no luck. Any suggestions? Yes I do have the 1/4" mic looped.
Anyone know the easiest free software I can ge my feet wet with?

I've been meaning to do this for some while. I have a few different softwares, and the Holmimpluse is something that interests me a great deal. Most of my answers I was getting about measurement was from Zilch, who unfortunately passed away recently.

I have the microphone also, and was meaning to either get the Mobilpre you speak of, or the cheapo way out outlined by Zilch on the Parts express forum. Watching with much interest

Russellc

sts9fan · « **Reply #12 on:** 5 Apr 2011, 12:45 pm »

I am a bit frustrated because my computer sees the M-audio as a output but not an input. Maybe I should have ponied up for a newer model.

sts9fan · « **Reply #13 on:** 6 Apr 2011, 01:15 am »

Now we are cooking with gas. Finally figured out the gear. I also just got my MiniDSP in the mail. The software could not be easier for this thing.

JohnR · « **Reply #14 on:** 6 Apr 2011, 12:01 pm »

Cool

sts9fan · « **Reply #15 on:** 6 Apr 2011, 08:51 pm »

First measurment with REW! 1/24 and 1/3 smoothing Don't laugh...

So whats fixable with EQ and what will I have to wait for my second and third subs for? I imagine that huge hump below 60hr will have to wait.

bpape · « **Reply #16 on:** 6 Apr 2011, 08:57 pm »

Try another measurement with the mic forward or back a bit pending where you could move seating. You may get lucky and be able to just avoid it.

Bryan

Russtafarian · « **Reply #17 on:** 6 Apr 2011, 11:44 pm »

That's smoother than my room, you lucky dog!

It's pretty jarring to see the truth, isn't it? I'm amazed at how our ears blow right through that and decode it as music.

Mess around with your sub's level and phase as you remeasure.

Tyson · « **Reply #18 on:** 7 Apr 2011, 12:03 am »

Also try measuring 30 degrees off axis, and 60 degrees off axis. That peak/valley in your upper mids might be a crossover artifact and might "fill in" when measured from a different angle.

For bass, remember that if you correct it for one listening spot, you are probably making things worse in a different listening spot. My general rule is to do cuts, but not boosts. Cuts tend to clean up the bass no matter where you sit, but boosts can lead to bad boom in every place except the listening spot.

DougSmith · « **Reply #19 on:** 7 Apr 2011, 12:34 am »

Quote from: sts9fan on 6 Apr 2011, 08:51 pm

First measurment with REW! 1/24 and 1/3 smoothing Don't laugh...
...
So whats fixable with EQ and what will I have to wait for my second and third subs for? I imagine that huge hump below 60hr will have to wait.

Not bad for starters. Check the impulse response for evidence of reflections. Some absorption might help along the left wall (better curtains). You could add some notch filters to knock down the 60 Hz hump until you get a second sub in.