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.

What SPL meter did you use?

I can tell you (from my opinion) that the difference between the EP500 and the EP800 is mostly FEEL (some sound though!)... Review to follow on my thread shortly.

So, Nick, your post prompted me to review all of my BFD settings to make sure they were correct and tuned to my Radio Shack Analog Meter (one of the newer analog models, to answer thefwam's question above). It turns out that I did not have the correct calibration file loaded for the SPL Meter, it must have dropped out when I updated the REW version awhile back.

However, even once I implemented the new correction file, the results were not far different (< ~1.5 dB difference at most in any one spot), so my readings weren't too far off to begin with.

The main thing I was worried about was my post-Audyssey BFD tuning screwing up the Dynamic EQ feature, but after testing today I'm happy to report that it does not affect it at all. Seeing that, I'm going to happily leave things as they are, because as Tom forced me to say before, it does sound good like this.

Thanks, Jason. I was reading up on the BFD guide on Hometheatershack trying to decide if I should be worried that my radioshack SPL meter wouldn't work, since they cautioned against it. I'm glad to know it works well for you

No problem Steve. Admittedly, it's not as accurate as the $150 mics they recommend, but from the reading I've done, it's accurate enough for most home users. The oldest versions of the SPL meters apparently are off quite a bit, but the version I have appears to be close enough for general use if you follow the instructions they provide for it (or so I think at least!).

Yeah That's what I understood from my reading as well. Especially for subwoofer frequencies the radioshack meter seem to be up to the task. I downloaded the Radioshack .cal file and it seems to be doing just fine for my purposes thus far.

I actually have a second question. What kind of interface is used to connect REW to the BFD? I was reading fredk's post about uploading your own filters into the BFD. Do I need to have a fancy external soundcard (given that I have a macbook that has only 1/8" in and outputs)?

I doubt very much that the Audessey mic is any more accurate than the Ratshack meter. For sub callibration the Ratshack meter is just fine. If you want to measure higher than say 2KHz, you need to go to the $150 Behringer mic/amp combo as the RS meter is useless that high.

FWIW: The Behringer ECM800 mic has been verified to be extremely accurate from 15Hz to 20KHz.

I entered everything manually into the BFD. Its dead simple. REW generates the numbers and gives them in table form so they are easy to read and enter. It takes about 2 minutes per filter and you should not have more than say 4 or 5 filters to EQ your sub.

Same with me - all manual entry, and that's plenty easy. There apparently is some MIDI interface you can buy to have them talk to each other directly, but it's easy enough to do by hand that it doesn't seem to make a lot of sense to spend more money on an interface just for that purpose. (I only loosely remember the direct connection works - so check my facts if you're really interested)

There is a midi interface, but I agree. I am impressed with how intuative the BFD is.

C'mon tweakers not interested in getting one more piece of the puzzle to try a quick reconfig over and over again with out having to do any manual entries, think about how much faster this would have been.

Oh I've definitely thought about it! Fortunately reason won out in this case.

Reason already went out the window when you ordered the EP800.

I thought that many times (particularly when the date kept slipping) until it arrived and I got to experience what I'd been hoping for.

Jason