Seaton Sound SubMersive1 - Page 154

Sounds like a plan. Thanks to Kalman, I have the v1.05 firmware needed to advance his 885 to the latest firmware. I am at a trade show all next week, but Dennis and I have 11/22 and 11/23 open for me to do the upgrades and Pro cal. Able to make either of those?

The week after Thanksgiving, I am back in Dalton for a carpet inspector's course. So I'd be looking at the week of 12/6 for a visit to your house.

Jeff

Craig, check your pm and email .
Mike

Mark, check your PM please.

I believe that Craig verified that his one position measurement was essentially unchanged from that of averaging over three positions; not as good as 32 different positions, but enough to know if there were any serious effects from this. And I don't get your issue with XTZ just because it's not more expensive; it seems that some of the most professional audio people in the business find it their favorite.

Missed that part about 3 positions. Link? The XTZ issue is covered in the Audyssey quote (and many others in the Audyssey thread) - basically altogether different measurement system from EQ system.

Post #4526 in this thread.

I do follow the Audyssey thread, but don't remember 'the XTZ issue'. It is of course not an EQ system, but rather a measurement tool, so I don't understand what is matters about it being a 'different measurement system' if it is accurate. Kal Rubenstein, who I perceive to be one of the real audio guru's, has stated in print that XTZ is his favorite measurement tool, so I doubt that it is too bad.

And the graph is "worse". Not a surprise. Different measure system and technique from the EQ system.

Kal is good. I prefer what the inventors of Audyssey say about measuring their EQ.

Since when does anyone "read" Playboy and Penthouse??????????

LMAO!

Just one more comment and I'll end this unproductive discussion with you.

you miss the point: the 1 and 3 positions measurements (with the sub in the less optimal position) were essentially the same, showing much poorer freq response than when he moved the sub to its more optimal location. I.e., your suggestion that his results were meaningless because he used only a single position are clearly unfounded.

Just so there is no confusion... I am *not* craigsub.

Craig (John)

I'm heartbroken!

Carry on.

Reporting back...

I went downstairs to my theater and reset the Distance Setting to 10.4 ft. I put on Donald Fagen, Morph the Cat. This song has incredible bass as recorded by Elliott Schiener. The bass guitar is articulate, strong and punchy. The bass drum has incredible "kick" and punch. Still, when both instruments play together, they are "heard" as separate instruments.

With the 10.4 Distance Setting, the bass was anemic, thin and totally lacking in punch and detail, just as Mark predicted. I reset it again to 13.8 ft and replayed the same song. The bass suddenly came alive with phenomenal dynamics, punch and weight. It was definitely not overbearing or accentuated; it was in perfect balance to the rest of the sound.

So which setting resulted in a sound that was closer to what Elliott Schiener intended, (or IOW, closer to "reference")? There is no doubt in my mind that ES would be embarrassed to hear it with the 10.4 ft. setting. He would be wondering how he could have screwed up the recording so bad. But, if he heard it with the 13.8 ft. setting, he'd have a big ole $hlt-eatin' grin on his face.

The difference was so obvious that I didn't even bother with any further listening. I just left it at 13.8 ft. Thanks again, Mark!

Craig

Just to clarify... I didn't change the location of any of the subs. I changed the Distance Setting in the pre/pro. Audyssey/Integra measured the Distance at 10.4 ft. I reset it to 13.8 ft to eliminate the phase cancellation dip. Neither of these settings correlate to the actual physical distance of any of the 3 subs. In addition, the subs have the DSP in the signal path, which will add a small additional delay.

If I had changed the location of any of the subs, I would have re-run Audyssey.

The first measurement was a single position measurement, with the mic at the primary LP:



The second was another measurement of the 10.4 ft Distance Setting. However, it was a weighted-average, 3 position measurement, with the mic moved from the left LP, to the center LP, to the right LP, and weighted at 30%, 40% and 30% respectively, (this is how xtz calculates a 3-position, weighted average). The "depth" of the cancellation was reduced by about 5 dB, but it still covered the same frequency range:



Craig

Oops! Yes, I did know that the change was in your sub distance, not the subs themselves; just a lapse.

I did not read all of the recent posts so if I missed it I apologize. What method did you and/or Mark use to come up with the new sub distance that gave you the better results.

I spent 10 years installing digital room correction systems well before Audyssey was ever thought of. I think DRC is the greatest addition to audio since I have been in this hobby (40+ years). I also think Audyssey enabled products have probably done more to (a) bring awareness to the necessity of room correction than any other single product and (b) provide a much improved listening experience for more users than any other single product. There is probably no more huge fan. That said, it is not perfect -- including Audyssey Pro. It must have some built in limitations for it to be used by the masses and individuals not well versed in room acoustics. And it does --- many of them. (On the other end of the spectrum of ease of use and flexibility is the $15,000 TacT Audio TCS MK III which I lived with for a month or so). Much better results than Audyssey but WAY WAY WAY more complicated than the average user would ever want to deal with.

I would suggest, Gary, that because Audyssey sets a level or a distance (or crossover) for a particular speaker does NOT mean it is absolutely perfect. It's way better than an individual would do who had no other measuring tools, but it is only a tool. Craig was dealing with sub distance. In my case, I ended up increasing the distance of my rear speakers from what Audyssey set (by a very small amount) because it greatly improved side wall imaging (a trick I learned from Mark as well). Audyssey is a great starting point but if you have other tools available, I sure would want to carefully check every Audyssey setting.

I used "trial and error" with measurements. I increased the Distance Setting in 1 ft increments until I got close to flat response through the crossover region. Then I changed the settings in 0.2 ft increments until I "went past" the flattest setting; then I backed up to the flattest setting. Finally, I checked a 3-position measurement to ensure it was appropriate for all 3 of the primary listening positions.

The beauty of a measurement system like xtz is how quickly and easily you can run through all the possibilities to find the optimum setting.


Can you describe the process you went through to optimize your rear speaker distances? Thanks!

Craig

Would be interesting to have done some listening as the distance was changed. With the dramatic change in measured response, I wonder if it would have been audible?

Jeff

http://www.avsforum.com/avs-vb/showp...postcount=4605

Doh!

I even read that ....

You're thinking that the notch was entirely due to cancellation between main ans subs in the crossover region, right?

Trial and error as well. I used either The 5.1 Audio Toolkit that Mark provides or Avia. One of the options on those disks will play a signal out of a front and same-side rear speaker simultaneously. While sitting in the LP adjust the rear distance until the image from that signal appears to come from the center of that wall. You will need to switch between the setup screen on your prepro to adjust the distance and the playing of the DVD. Adjust by the .2 foot increments until the image is where you want it and repeat for the other side of the room. Works like a champ and will really improve the whole envelopment phenomenon. It is certainly possible that the distance Audyssey comes up with will be correct but it has not been for my room and my speakers. IIRC I changed the distance by .4 feet for both speakers. fWIW I used to try to accomplish the wall centering trick by increasing the volume of the rear speakers but this is a lot better way.

I'd like to say I came up with that idea but I stole it from Mark Seaton. (who else).

As that was the only change made, absolutely. This sort of fine tuning of a crossover is very common practice for those setting up professional sound reinforcement systems. A phase change could have a related, but slightly different effect, but I often find better results by making delay adjustments rather than using something like a variable phase knob/all-pass filter, which would also go against some of the correction Audyssey is working to correct.

Given the realities of the crossover implementation in a modern multi-channel system, this sort of fine tuning should not be a surprise to anyone who has looked into crossover design (and yes, I realize most have not). The distance change we are talking about here is only 3.4' which is roughly a 1/4 wavelength around 80+Hz. If we dig deeper into the resulting group delay and other delays incurred through filters/correction employed, this isn't a huge mismatch for this frequency range. The mismatch could very easily, and I suspect more likely, be the result of deviations in the real response of the main speakers rather than that of the subwoofer.

Here in Craig's earlier post of the subwoofer only response is the proof that the issue lies in the interaction of the main speaker and sub.

An overlay of the above corrected response, that of the main speakers, and the combined response would complete the picture.

Craig: Had you taken a measurement of the Center-Subwoofer combo? This is accomplished by sending the same signal to both the L & R input of your preamp with the surround mode in Dolby PLII: Cinema (not Music).

How is it that using something like a variable phase knob/all-pass filter would go against some of the correction Audyssey is working to correct and making delay adjustments would not?

I am referring to the phase response and decay time correction that Audyssey can do. By definition, a phase shift function by creating a variable delay vs. frequency which increases as frequency lowers (lower frequencies = longer period = greater group delay for the same phase shift).

Adjusting the delay (by way of relative distance settings) creates an equal delay offset per frequency which does not skew the bass range, but shifts it cohesively. Any way cut it up, use of a phase knob to make this adjustment will create an overall more significant deviation vs. the delay adjustment.

So you are saying delay adjustment will cause deviation also, just less so?

Since the correction is applied to the subwoofer in isolation, no. The phase behavior of the subwoofer will remain the same. The only change will be the integration/interaction with the main speakers, which in this case makes for an improvement. Using a conventional phase control to make this final tweak would skew the group delay vs. frequency.

Got it. Thanks. Still don't like the trade-offs over a listening area vs. a single position.

BTW, my HP sounds great!