Sound Card Calibration

**koiman** · **04-20-07, 11:30 AM**

Otto,
I have tried plugging and unplugging the the SB several times this AM and I switches back and forth correctly between the SB and the Computer default.
Leon

**Otto** · **04-20-07, 11:40 AM**

So then does it look the same as this picture, or different? Note that in this picture, your input device is still listed as NVIDIA.

**koiman** · **04-20-07, 11:51 AM**

Otto,
This is what the sounds set up looks like.. And does every time I plug in the SB with the usb Plug.
Leon

**Otto** · **04-20-07, 11:52 AM**

OK! I like that one much better!

I'd swap that cable next.

**MakeFlat** · **04-20-07, 12:04 PM**

Quote:

koiman wrote:

Otto,
This is what the sounds set up looks like.. And does every time I plug in the SB with the usb Plug.
Leon

Hmm... very interesting. I am learning something new. I think the PC remembers your last choice when you set recording to SB Live. I initially had to manually change those and I had to repeat those changes after my laptop overheated and shutdown. Since then, my laptop seems to remember my selections.

**OzOnE** · **04-20-07, 01:52 PM**

Crikey. I've never used such a thing as an "attenuating" cable. That would explain a lot!

Apparently, these cables are usually used for connecting an amplified ear / speaker output to a line input etc., but the speaker output on the SB USB is most probably NOT amplified. The cable must have a resistor inside one of the plugs. I would avoid this cable like the plague.

It's a bit bad of Ratshack to sell you that cable, but I think they were guessing you had an amplified speaker output.

Oh well, I hope you get it sorted in the end. Now that your control panel looks correct, I would try recording XM or something using your RCA cable (which shouldn't be attenuated!).

OzOnE.

**koiman** · **04-20-07, 02:06 PM**

OK Guy's
The problem is fixed as far as the sound card calibration.. I returned the cable to Radio Shack and replaced it with a 3.5mm mono plug on each end and 6 foot long. The cable I had had a 90db attunation. Here is a picture of my sound card it only took 2 weeks to figure it out.
Thanks,
Leon

**Otto** · **04-20-07, 02:33 PM**

Great news!!!!!

**OzOnE** · **04-20-07, 02:34 PM**

Hi koiman,

That's great news. Glad you sorted it.

One thing though, if the black line in your last picture is the sound card calibration, it looks like you have bass redirection turned on (the slope goes up to 80Hz) - are you only using the SB for two-channel stereo (no surrounds), and do you have a sub?

If you're connecting the SB to your amp with a single stereo RCA cable and want your AV amp to "control" your speakers and sub, you should turn off the filters on the SB drivers and let the amp handle the bass redirection.

With the filtering enabled on the SB, you will get little or no bass. Also, REW might try to correct this situation and go a bit wrong.

OzOnE.

EDIT: Oh, I just noticed that the black line is the mic calibration line. The sound calibration looks great - I'm not sure why the mic calib rolls off like that though?

**brucek** · **04-20-07, 03:40 PM**

Quote:

I'm not sure why the mic calib rolls off like that though?

Look at the vertical scale........

**MakeFlat** · **04-20-07, 07:26 PM**

It looks like his mic calib file might have been corrupted. Leon, where did you get your mic calib file?

**koiman** · **04-20-07, 08:03 PM**

Nick,
Here is a shot of the current sound card setup.. I am using the cal. files for the CM-140 SPL meter.
Leon

**MakeFlat** · **04-20-07, 09:04 PM**

Leon, it looks good.

**brucek** · **04-20-07, 09:46 PM**

Quote:

It looks like his mic calib file might have been corrupted. Leon, where did you get your mic calib file?

Makeflat, look at the vertical scale of the plot you're questioning. It has a swing of only +/-3dB. It exaggerates even the smallest changes. It only makes the cal file appear to drop radically. It's the scale that causes it.

Now look at the graph in post #87. It has a swing of over 150dB. Do you see why the two plots look different, when they are representing identical data?

brucek

**MakeFlat** · **04-20-07, 09:59 PM**

Quote:

brucek wrote:

Makeflat, look at the vertical scale of the plot you're questioning. It has a swing of only +/-3dB. It exaggerates even the smallest changes. It only makes the cal file appear to drop radically. It's the scale that causes it.

Now look at the graph in post #87. It has a swing of over 150dB. Do you see why the two plots look different, when they are representing identical data?

brucek

Ken, you are right. Anyone can have a flat looking response if the vertical scale is compressed!

I am going to do a series of REW measurements before they come home.

**OzOnE** · **04-21-07, 05:36 AM**

I was just surprised that the mic calib file rolls off that steeply, but in the second screenshot it looks fine, and it makes sense that it slopes quite a bit, as it goes right down to 5Hz!

Leon - it looks good now. Which amp / speakers / (sub?) are you using though?

OzOnE.

**brucek** · **04-21-07, 07:00 AM**

Quote:

I was just surprised that the mic calib file rolls off that steeply, but in the second screenshot it looks fine

Quote:

It looks like his mic calib file might have been corrupted

And this is the reason I keep harping to everyone to post their graphs with a horizontal scale from 15Hz-200Hz and a vertical scale from 45dB-105dB.

Any other scales will create confusion to anyone who isn't used to interpreting scales on a graph. That's why we stress consistency in scaling.

I can post two graphs using the same data and get completely different comments about them.

Here's two graphs using the same data. You can bet I would get a lot of different suggestions about them, even though they're the same measurement.

bad.jpg
good.jpg

brucek

**OzOnE** · **04-21-07, 08:10 AM**

Hi brucek,

Good point about the scaling. I saw the sticky about the graph scaling but the thing that confused me was the fact that the mic calib file starts sloping off at 80Hz a bit like a "crossover" filter would do. I suppose this is mainly due to the measurement points in the calib file being kept low while still maintaining realative accuracy?

Is the CM-140 really that flat from 80Hz to 20KHz? - I still don't have a proper measurement mic or SPL meter yet, and was wondering if it would be worth me just buying a CM-140 for both purposes, or just get an ECM8000 like almost everyone else has plus a cheap SPL meter?

I've been messing around for ages now with a home built mic made from a WM-61A capsule, bodged mic preamp, and Phonic mixer, but it never sounds quite right. I'm actually using it for DRC on my HTPC, and the improvements in the bass performance are already very impressive.

So, to anyone thinking of building your own mic, I wouldn't bother! Electronics is my main hobby, but I still can't get the noise levels low enough from my home built mic, or get a decent DRC measurement. A home built mic might be suitable for REW, but I could have saved myself so much time and frustration and just forked out £40 for an ECM8000 instead!

I will definitely consider getting a BFD in the near future as it looks like it gets the sub response MUCH closer to ideal without the need for the PC. The obvious problems with the HTPC are noise, ease of use, time to boot etc. I've actually been looking everywhere for a cheap DSP solution to DRC, but it doesn't look like that's going to happen any time soon. There are more of my ramblings about this on diyaudio for anyone who's interested.....

http://www.diyaudio.com/forums/showt...49#post1178549

OzOnE.

P.S. does anyone know which DSP chip(s) or main CPU the BFD's use?

**brucek** · **04-21-07, 08:23 AM**

Quote:

I suppose this is mainly due to the measurement points in the calib file being kept low while still maintaining relative accuracy?

Is the CM-140 really that flat from 80Hz to 20KHz?

No, the calibration file goes to 200Hz. REW extends the line from the last known point, which is 200Hz.
It's flat from 80Hz to 200Hz. Above that it is "likely" flat, but no guarantees. The CM-140 is a fairly good meter though. It has very good consistency between meters, which allows you to have better confidence that our generic calibration file will be accurate for your meter. It's a **** shoot with a Radio Shack variety.

brucek

**MakeFlat** · **04-21-07, 09:01 AM**

Quote:

brucek wrote:

...have better confidence that our generic calibration file will be accurate for your meter. It's a **** shoot with a Radio Shack variety.

brucek

How much variations are there from one RS meter to other RS meters? I thought there was a post somewhere but I could not recall it.

**brucek** · **04-21-07, 09:23 AM**

See here...

**MakeFlat** · **04-21-07, 10:55 AM**

Quote:

brucek wrote:

See here...

Thank you. That's exactly what I was looking for.

**koiman** · **04-21-07, 02:53 PM**

OzOnE,
The main reason that I wanted to set up the soundblaster was to calibrate my Salk Veracity HT3 stereo speakers. In my Stereo system I am running Channel Island D-200 Mono Amps, Exempler Denon 3910 DVD player and a Modwright 9.0 SE Pre Amp. I also have my home theater system Which has (4) Axiom M 80 Ti Speakers (1) Axiom VP 150 Center channel (4) Axiom QS 8 and a SVS PB 12 Plus subwoofer. Also I have a Pair of Axiom M22 Ti and a pair of Axiom M3 Ti not to mention a pair of 1970 ESS Heil Speakers the play every day. Denon 3803 AV, a Denon 2910 DVD Player amd multipal other DVD Players And SS and Tube amps. I am crazy when It comes to audio sound.
Leon

**OzOnE** · **04-21-07, 06:50 PM**

Quote:

koiman wrote:

I am crazy when It comes to audio sound.
Leon

Blimey, this stuff is way over my head at this point. I'm only using three M&K LCR-55's for the fronts, four Mordaunt Short MSB-20 dipole rears, and a VX-4 sub. My amp is a Denon AVC-A11SR which I got for the bargain price of £250 (around $500), which is very cheap for this amp on eBay atm (well, in the UK at least.)

(The reason the Denon was cheap was that had a shorted center speaker amp section, so I swapped the working parts from the "Surround Back Right" channel to the center channel for a while until I recently got some new transistors from the US for around $50 to repair it properly.)

Your HT3's and Axioms look very nice indeed, but I'd have to win the lottery or something to come anywhere close atm! Also, SVS subs look very popular on the forums, so I might look into that when I can scrape some money together for some upgrades.

Good luck with REW!

OzOnE.

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