Axiom Home Page Forums General Discussion Home Theater Fun? With Audyssey

So... the arrival of the EP800 has brought out the nasty tweaker in me again. After taking all of the measurements I posted the other night, I've again found myself playing with my BFD equalizer more than is probably healthy, but I have pulled out some interesting curves that I thought I'd share.

The first curve shows the natural in-room response of the EP800 with no equalization applied versus the corrected curve using the BFD equalizer. This is all pre-Audyssey.

I was quite happy with the corrected curve, 13-80 hz at +/- 3dB.



Note that in systems using equalization, Audyssey recommends that you first equalize the system and then run Audyssey, so I was doing it in that order here as well.

Now that I had a relatively flat curve to work with, I re-ran the Audyssey room calibration with multiple readings and checked the results using REW. They were fairly disappointing.



It introduced a significant dip in response at 20 Hz and then also implemented a steep roll off around 80 Hz. I have a question specifically about the crossover rolloff. When I ran these frequency sweeps, I do them in stereo mode with the subwoofer running as I want to measure a flat response with all running (since that is how I will listen to anything in my HT). Given that it's a Mains + L&R test, I would want as flat a response as possible, correct? I would not want a rolloff at the XO point, as the sound should blend seamlessly from sub to mains around the XO point. Right?

At first I was trying to give Audyssey the benefit of the doubt that this was a crossover-related rolloff, but I don't think that makes sense given the explanation above.

In any case, what I ended up doing was retuning the curve with Audyssey ON, which I know you're not supposed to do (it messes with Audyssey not knowing what you've changed after you've run the initial measurements), but I would much rather do that than deal with a curve like the one above.

So, after much more screwing around, I came to the plot below showing Audyssey's "corrected" results and my "corrected-Audyssey" results.




The goal was to get it back to as flat as possible without a rolloff at the sub's XO point... I've definitely accomplished that goal, and in fact now have the sub playing 12 (TWELVE) to 85 Hz at slightly better than +/- 3 dB, so no complaints there, but after doing it this way, I'm fairly certain I've screwed up any benefit Audyssey could possibly offer me by changing the subwoofer's tuning so much after it ran its measurements. That seems to make the best option turning Audyssey off completely (negating the $100 I spent on the feature pack upgrade which until this point I did find useful)... I guess I'm ok with that if I have to, but it seems sub-optimal. Other ideas? Or should I just scrap Audyssey for now and enjoy things without it?

Jason

Is Audyssey just EQing sub frequencies or the whole spectrum?

Can't you just turn off the EQ of Audyssey and still take advantage of the dynamic volume control which I think would be worth the $100. I haven't done the upgrade yet so I am not sure of the related working of the new fetures.

Audyssey has to be engaged for the other features to work. My understanding is that Audyssey uses the measurements it takes in room calibration to make the rest of the features work right.

Fred - it EQ's the whole spectrum, but if it screws up the sub this badly, is it worth it to EQ the rest?

Since this question might have gotten lost in my long post, can someone please confirm my understanding here?

Thanks,

Jason

I thought that Audyssey is supposed to be good with everything but the sub region (as we can see from your plots). But, it sounds like you found a work-around for the < 80 Hz region so that you can still leave the Audyssey on. I remember reading that he flagship stand-alone Audyssey pro unit was supposed to do much better than the ones built into receivers in the sub region. For that unit you need to have someone come in and set it up with test equipment and a long procedure. I think the unit is around $2500 and only works between a preamp and an amp though. That BFD equalizer gives some nice results though. I might have to pick one of those up.

- Nick

myrison,

How do you know that the measurements you have are accurate? I thought that the Radio Shack SLP meter is supposed to be pretty inaccurate below 80 Hz. There is a Rives Audio Test CD 2 that that has test tones to compensate for this. However, the test tones are not on as fine as a scale as your graph though. The corrected test tones are at 20, 25, 31.5, 40, 50, 63 and 80 Hz. There are corrected test tones above 80Hz as well on the CD but that's not what we are talking about here.

- Nick

Nick - thanks for the responses. The REW software used with the BFD has calibration files that you can load for your specific SPL meter that are supposed to compensate for any differences b/w the SPL meter and actual recorded values.

It also allows you to first calibrate your particular sound card's results to the values recorded by the SPL meter using a test sweep sent from the computer, recorded by the SPL meter, and then fed back to the computer through a loop back connection. I theory, by doing this first you adjust for any inaccuracies in the meter you are using.

That's what they say at least, you could be right though that the Audyssey measurements are more accurate than the RS-meter I'm using and that's why there is such a difference. From everything I've read though, even the RS meters aren't supposed to be _that_ far off as what I've shown above, but who knows... If that's the case, think of all the time I'm wasting trying to equalize the sub with this meter.

What I probably need to do is just run through the entire sequence again and see if I get different results, but it's such a tedious project, I'm going to wait to see if any other pearls of wisdom show up here first to keep me from making the same mistakes again (if I am making any).

Jason

Um, how does it SOUND?

Oh Tom, always cutting to the chase and skipping all the fun.

But since you insist, it sounds great.