"Crossover Design for New Project"

[GM]

Greets!

Well, I keep looking at these charts, but never seen such odd in-door ones, especially in a house that's probably built far more sturdily/massive than mine, so not sure what to make of them. For one thing, I'm surprised that a sealed Cornwall would be tuned this low or why the room has so little corner gain in any mic position.

For now then, tuning to Fs seems as good as any place to start unless you've decided to shrink the cabs much, so where are you on basic cab dims?

GM

[Altec Best]

Greets!

Well, I keep looking at these charts, but never seen such odd in-door ones,

Pano said the same thing.I'm going to measure something else to see what's up.Now when I measured the Cornwall inside it was atop my Model 19's and off the floor 39" would this affect the measurement like this.

[Panomaniac]

I think there was a measurement glitch. I had a look at the files and beside the odd FR, distortion is extremely high across the range. So something must have gone wrong.

[Altec Best]

Hey Pano I measured my other 288's with the 299 diaphrams.Set up exactly the same now these look good.

1/6th Octave Smoothing

[GM]

It will affect it some, but can't account for what I'm seeing, so at this point a reasonably detailed set of pics and/or description of the room, it's location in the house and surrounding rooms might be helpful. What software did you use and how did you set it up?

GM

[Altec Best]

What software did you use and how did you set it up?

I used HolmImpulse and Pano and I set it up.I kept settings the same.I know there was something wrong as I was having a hard time getting the test signals(Sweeps) to fire.Like it had a mind of it's own.I think the problem is with Windows Vista and not the testing gear/software actually I know it is.

My OS system is Windows Vista Home Premium SP2 and it likes to use it's own (Microsoft) drivers. I think I have resolved that issue for now, hopefully !

[GM]

IIRC I saw where someone else had this type of problem using ARTA or similar, but can't remember where I read it or what the solution was.

GM

[Earl K]

Hate to say it John , but the green trace looks like it's been contaminated with some form of a superimposed "carrier wave" onto the original impulse capture.
- The regularity of the superimposed wavelet is pretty suspicious looking.

- Check the computers sound control settings to make sure that you don't have a feedback loop or have a second "open mic" adding extra content onto the capture .
- A "second open mic" could be the computers builtin mic .

<> cheers

[Earl K]

IIRC I saw where someone else had this type of problem using ARTA or similar, but can't remember where I read it or what the solution was.

GM

I believe you might be referring to sba2 .

Read this post ! from this thread !

He belatedly admitted that he had a problem with HolmImpulse ( specifically , his soundcard calibration file for it ) .
- Sadly, that would make the following FR of his , need to be classified as "bunk" .

Looks like I have some (a lot of) issues to sort out with the software, my soundcard, and its drivers. When I figure it all out, I’ll add it to “The Book of Hard Knocks"

It turns out that all of my HOLM FR plots were contaminated (at 2 msec) by a very poor soundcard calibration file, which turned out to be not really a calibration at all, but a feedback loop between the “line in” and the “output”.

The problem went unnoticed for a while because I didn’t closely examine the IR plots, and didn’t even know what a proper calibration plot was supposed to look like.

The HOLM software has no documentation to help with such calibrations… hell, it even told me that I had made “valid” cal measurements.

I only discovered the feedback issue by reading about it in the REW manual.
Disabling “record monitoring” usually gets rid of the problem, but, I haven’t yet been able to access this function, either through the card directly, or via its latest ASIO driver, or via ASIO4all, or via Windows (XP).

I bought my card years ago simply to get high quality sound from my laptop, as well as to occasionally transfer something from vinyl (my laptop’s input is only mono mic). Recently I had recalled seeing the card on ARTA’s list, so I didn‘t think twice when I began measuring. At the moment I would give the Echo card a “no go” for acoustic measurements.

By removing the Echo card and using my laptop’s piddly internal SigmaTel card with MME 16bit/41k , I was able to get a proper cal file, but I’m not yet confident of that whole scenario. The latency with the SigmaTel was pretty high, too

I’ll probably have to get a usb card.

One "solution" to these sorts of trials ( & tribulations ) is to use a few programs & then compare the measurements of each against the others .

<> cheers

[GM]

The regularity of the superimposed wavelet is pretty suspicious looking.

Yeah, definitely not right and just wrote it off as part of the other measurement anomalies that have crept in.........

GM