# Problems with MacBook Pro and Edirol FA-66



## woody77 (Aug 21, 2008)

I have two different problems, although they may be related.

My setup is as follows:

15" MBP 4GB RAM
Edirol FA-66 (firewire)
ECM-8000
Behringer A500 amp

I'm doing subwoofer testing (home-built), and when I use REW I either get no data at all (scope shows garbage), or I get a really odd measurement that's VERY repeatable, and shows a very strong roll bass roll-off (-30dB/octave with an F3 somewhere around 60Hz). I can reboot, I can restart REW, I always get this rolloff, and it only seems to show up in REW. ???

Now, I'm pretty sure it's not the FA66 + ECM, as they work great in Audacity and other apps. I can use it with AULab to create chains of dsp filters (using it as input and output). But REW just does not like it.

I did a side-by-side of the values returned by REW with a radio shack spl meter (<1m and ~2.8V signal at speaker terminals). That's the last graph. I swept by hand and took the spl values off the FFT display (the built-in spl meter was talking jibberish through most of this.

here's a guide the attached images:

1) wonky results I get whenever I try to do a soundcard calibration
2) sub response as measured by REW
3) comparison of REW and RS spl meter.


----------



## woody77 (Aug 21, 2008)

A bit more info. The sub is a sealed passive unit (usually powered by the Behringer A500 amp). I've taken impedance measurements, and it's Fsc is 34.5, with a Q of .568 (~6 cubic feet, and a 15" driver with an Fs of ~21Hz). The nearfield measurement above from the radio shack spl meter tracks within +/- 2dB of the expected (WinISD Pro) response (after taking into account the RS calibration file's values).

An interesting note. The FA66 ONLY runs in 24-bit mode, apparently. I can reboot it into 44.1 or 48, but it only lists itself as 6-channel 24-bit in the Audio MIDI settings app.

Edit: And I know it's not the FA-66, because I made these measurements about a year ago, with the same setup.


----------



## JohnM (Apr 11, 2006)

There are a couple of potential issues. Is the MBP Intel or PowerPC? On PowerPC there are audio byte swap problems, which might explain the odd appearance of the captured audio in the Scope plot. If that is the case you could try measuring with REW V3.29, that handles the endianess correctly and you can then load the measurements into V4 for further analysis. 

If the processor is Intel the next issue is accessing Firewire-connected soundcards under OS X seems a bit hit and miss, some people have reported successfully using Firewire cards but more seem to have problems.


----------



## woody77 (Aug 21, 2008)

It's an Intel MBP, and since it previously was working fine (same software + hardware), I'm thinking there's something hit or miss with the setup (as you mentioned). I'll reboot and run a bunch of tests and see what I get.

Whatever the issue is, it's only in REW. My guess is that it's really a problem with the java sound libraries vs. the native ones (Cocoa based apps seem perfectly happy).


----------



## woody77 (Aug 21, 2008)

I'm beginning to further suspect this is a library issue. Reboots and such aren't fixing it. Luckily I can use the FA-66 as a pre-amp for the mic, and use the laptop soundcard for REW's input. Good enough for sub work and matching mains to the sub.

Playing around some, it seems that REW is getting values between samples (as 0 values). Perhaps a bug somewhere where an array of size X is passed in, filled to point Y, and then returned, and the rest of the values are 0s (from Y to X).

If any of the devs are on here, I'm also a java dev (mostly embedded J2ME/J2SE with some J2EE work). I'd be willing to poke around with my setup and see if I learn anything with some debug statements.

One thing that caught my attention is the "non-interleaved device" bit in Audio/MIDI setup. Other screenshots for the USB devices say "master stream".


----------



## woody77 (Aug 21, 2008)

I think my previous results may have been made the same way I made the measurement below. FA66 used as a mic pre-amp, and then taking the monitor output and running that into the input of the MBP. Especially as I found the calibration file for the soundcard for that setup. So.. highly possible I never did get this working a year ago, and instead I'm traveling the same ground again :sigh:: I really need to take notes when I do this stuff).

Anyway, the big peaks are all room modes (big room with hardwood floors, angled cieling, and lots of large open doorways to other rooms). The house has lots of crazy resonances when you're walking around with bass-heavy music playing (a node in a hallway, and the bathroom shower is pretty crazy).

I really need to find a new place for the sub to live, and decouple some of these modes. But that will need to wait for the smaller cabinet (20" cube vs. the 18x22x29" cab I have now). The smaller cabinet will get a custom active EQ circuit that performs a linkwitz transform to make it a Fsc=25Hz and Q=0.707. it will be natively a Q=0.8 and Fsc around 35-40 (IIRC).

Smaller cabinet will be easier to place in the room (as it's the living room).

It's definitely a compromised room, but I might throw a BFD or similar at it to to quell some of the modes.


----------



## JohnM (Apr 11, 2006)

You could try setting the FA66 up as stereo only if you haven't tried that already. Also make sure nothing else is running that makes use of the soundcard, in case some other app is asking for big-endian streams.


----------



## woody77 (Aug 21, 2008)

The FA-66 is certainly odd. I have it set as stereo on the front panel, but OSX only will use it as a 6-channel device. CoreAudio works perfectly with this, and most things come out correctly using stereo in/out (inputs 1-2, outputs 1-2 as input L-R, output L-R).


----------



## woody77 (Aug 21, 2008)

John, if you PM me the Java interfaces you're calling, I'll write some stuff on the side to play with receiving input data, and see how it works vs. the other interfaces (built-in).


----------

