The Audyssey Pro Installer Kit Thread (FAQ in post #1) - Page 109

C h e a p e r, maybe? Plus, how many people use a serial port to transfer large amounts of data?

 

I can only hope.  Here is what I submitted to Denon:

 

"I have recently upgraded from the AVR-4311 to the AVR-4502.  I use the Audyssey Pro Kit to calibrate both AVR's.  The Pro Kit connects to the AVR using a serial-to-USB cable.  Since the upgrade, I am experiencing data transfer rates to the AVR-4520 that are 50% slower than what I was seeing with the AVR-4311.  This makes the Audyssey calibration take significantly longer.  Kindly forward this case to your engineers and ask the following question:  is the slower speed of the serial interface caused by a different serial chip on the AVR-4520, or is there an issue that might be corrected by a firmware upgrade at some time in the future?"

 

Yes, that question has been asked, but never answered.

I re-read. The distance bug was asked about in the same question as the splice "issue" and this allowed the "answerer's" answer to be less than fulfilling. (that's my fourth re-wording of that)

Unless the question is asked in a question by itself, I don't think any light will shine on it. (second re-wording)

Jeff

I went into Pro last evening and grabbed some screen caps of the curve editing process. I still need to get some additional caps of using a spreadsheet to edit, but I have made some progress in pulling the guide/answer together.

Jeff

 

I'm sure you are correct, but I fear that Chris is getting tired of me trying to prove that something is wrong. 

If there are bugs in the correction by Audyssey, then it is Audyssey's testing that is at fault. Audyssey, I believe, must approve the implementation of their algorythms. The issue is as much Audyssey's as it is Denon's, if there is a bug in that area. If Audyssey claims that they have no responsibility then they have incredibly poor management and legal staff as a company or they are trying to avoid involvement.

No seriously managed company would ever let their brand name be associated with a product without testing to assure that the part of the product representing their name/brand is operating correctly. Yes, bugs happen, but ther must be part of the contract with Audyssey where Denon agrees to fix any bugs in some time frame.

BTW...I think Audyssey is very well run....they just may be trying to hide from an issue.....

From the top: Sub distance and level settings are not stored in AMD files. This is due to AVR/processor architecture issues. So, it is not a bug and will not (ever) be "fixed."

I don't think we should expect any more information than this.

We should put this into the guide. When doing a "fresh" calibration, i.e. with mic and the sub level matching screen, sub distance and level settings should be written and saved for possible future use.

Jeff

We have bumped into situations before where Audyssey's relationship with their licensees "complicated" Chris' freedom to explain certain things. And, of course, he couldn't explain further why he ... couldn't explain further. I think this sub distance/level settings not being saved in AMD files might be one of those situations.

Thanks for your efforts, Jerry. I hope Denon responds properly and fixes the problem but I sense that it's not going to happen, which will mean bye-bye to my upgrade from a 4311 to a 4520.

Mark

@Keith:

 

Due to Craig John's recent feedback to Mastermaybe on the Audyssey thread (which I agree with completely), I believe the following wording in the Subwoofer Gain Matching section of the Pro FAQ,

 

"Note: Gain-matching works best on identical subs, but is still useful for unmatched subs" should be changed to read

 

"Note: The gain-matching procedure is designed for identical subs, and will not produce the desired results for unmatched subs".

 

Comments?

Wouldn't this depend on how mismatched the subs are?

Jeff

 

Maybe, but I don't want to be accused of over-thinking it.  Perhaps we should simply add a "YMMV".....    :)

Overthinking? Not possible. Nearly Every answer we give to any of these questions involves educating. But it's like Russian nesting dolls as each answer begets another question .. and another deeper answer. The challenge is not to pull the information together, though that is time-consuming enough, but rather to be concise and know when to stop.

Jeff

Hi guys,

Jerry, I totally agree with your suggestion for the FAQ. Gain-matching dissimilar subs will not provide the system headroom optimization, or the "lesser" sub protection, that it provides for identical subs. When one gain-matches dissimilar subs, they'll remain gain-matched all the way up to the point that the "lesser" sub starts to compress/distort. Then one of two things will happen: 1. The "stronger" sub will be held back to this point, or; 2. The lesser sub will be driven beyond the point of compression/distortion, and it could be damaged. This is exactly the scenario Mastermaybe was concerned about with his Captivator and his DIY sub. The only way to utilize the full output of the Cap, while protecting the DIY sub, is to set the DIY sub lower than the Cap.

To Jeff's question about the extent of the mismatch, one needs to consider 3 things: 1. The F3 of each sub; 2. The maximum output of each sub at the F3, and; 3. The roll-off of each sub below F3. If all 3 of these parameters are similar, then the subs are similar enough that gain-matching could be useful. If any one of these parameters is significantly dissimilar, then some other strategy for setting the gains should be used.

I'll add one other editorial comment: If the subs are significantly dissimilar, I can think of no scenario in which level-matching would be appropriate, especially if system headroom, LF extension or "lesser" sub protection are concerns.

Craig
Edited by craig john - 10/17/12 at 8:43pm

The real question is whether AJ's experience of a glacial Pro run can be replicated for single as well as multiple sub configurations, and various speaker configurations (5.1/2 in particular). If the price of a more 'correct' Pro calibration for a multiple sub setup, in terms of a smoother bass in the mains/sub splice region without the the distance tweak, is owning an AVR that processes Pro Cals two to three times slower, that's one tradeoff.

But if any Pro run, regardless of number of subs and speaker configuration, took that much longer, period, I'd personally hesitate to upgrade to the 4520 any time soon until the speed issue is resolved.

Good point. In my Mac world, there are no serial ports and never have been, so I have never encountered one AFAICR. Seems like a good call :) 

 

Well the way that is worded Jerry is totally clear and cannot be misunderstood AFAICS, so at least you stand a chance of a reply. I hope it's the FW option of course. Fingers crossed.

Way to go Jeff!  If you glance at the Pro FAQ you will see that it is now very easy to insert images and to flow text around them (to a limited degree) and so on, to make for a nice looking job, so yes, those screen caps will be real useful!

 

He has the patience of, er, whoever it was who had legendary patience... was it Job? But Ask Audyssey is a pretty self-explanatory title for a website, so I can't see a problem in asking a question and expecting, well, an answer. It's not that you are trying to prove something is wrong, more that you are trying to bring to their attention something several of us have observed. Keep at it Jerry - you have the might of right on your side ;)

I think it is mentioned somewhere in the FAQ but it probably deserves more prominence. I'll add it as a separate question to the 'Post Calibration' section - write down the info NOW....

Jerry you have far more experience and expertise with this issue than I do, so if you say it needs to be changed, then it needs to be changed AFAIAC. I will change it forthwith.... thanks for pointing it out.

 

 

 

I will use a meld of all of the above info to rewrite the relevant part of the answer as a 'caveat' to the procedure described. In the Pro FAQ I think it is fine to go into this sort of detail - it would be inappropriate in the MultEQ FAQ due to the far lower level of user experience in there - but here, the more explanation of the 'Why' the better - the other FAQ is more about the 'How' than the 'Why' I think.

FAQ UPDATED!

 

Substantial edit to this answer:

 

b)3.   Gain-Matching Subwoofers — Why and How?

 

New question added:

 

d)2.   Why do I need to write down the sub level and distance settings?

 

Comments and suggestions, as always, welcomed.

Gain-matching? Why? Low frequency sound quality depends on flat frequency response and low modal ringing. None of this can be achieved by gain-matching or level-matching of subs.

I'm interested in this two - I also have two identical subs.

If the subs are significantly dissimilar, then I question whether using both will produce better results than using only the more capable sub. Yes, there are schemes where "dissimilar" subs are used to smooth room modes, but those schemes usually involve many subs, plus I don't think badly mismatched subs are contemplated.

Jeff

Gain matching results in both/all subs working the same, i.e. producing the same output. The level matching done in Audyssey results in each sub producing the same SPL at the MLP. Concerns about the former could be that is might reduce the effectiveness of Audyssey's filters (gain changes are made after calibrating), while concerns about the latter are a "farther/farthest" sub in a multi-sub system running out of gas and limiting the performance of the subwoofer "subsystem" as a whole.

Jeff
Edited by pepar - 10/18/12 at 10:52am

The following assumes identical subwoofers:

If level-matching achieves a result that is very similar to gain-matching, (which it appears to have done in your system), there is little to be "gained" with gain-matching. They are almost the same. It is when one of the subs is reinforced by the room differently, (either due to different modal reinforcement or due to to different proximity to the listening/measuring position, or both), that gain-matching is beneficial. If one sub has a big peak in it's response, and the other sub has a big null, their "levels" will be set differently because their "average" levels will measure differently. Or, if one sub is placed closer to the LP, it will measure louder than the further away sub, and it's level will be set lower to compensate. If these disparities are large enough, you can have a situation were the higher set sub is driven harder and will get into compression/distortion before the lower set sub. This limits system headroom, and can potentially endanger the higher set sub.

None of this appears to be the case in your system, so you would have little to gain with gain-matching. However, in a system with 3 to 6 dB, (or greater), of disparity in the level settings of the subs, there can be a significant benefit to gain-matching. Remember that 3 dB equals a doubling of power requirement AND driver excursion. 6 dB equals 4X the power and excursion. Why make one sub work 4 times harder than the other? They are identical subs; they should both drive the same power into the room.

You mention that you're never aware of the subs approaching their limits. Your DD subs have Servo Controls that limit distortion, so you would not hear any bad sounds, (distortion), when the subs approach their limits. However, you could experience compression. This is where the subs don't respond linearly to increased input. IOW, if you add 3 dB of input, you may only get 2 dB of additional output; if you add another 3 dB of input, you may only get 1 more dB of output. Josh Ricci measured the DD18+ and showed the effects of compression: http://www.data-bass.com/data?page=system&id=64&mset=68 (Scroll down to the 5th graph labeled "Long Term Power Compression.") In other graphs on that same site, you can also see the effects of the Servo on the distortion.

C'mon Markus... sure it can be done. I've done it in multiple systems. Here's my own system:


That ^ is 3 subwoofers, randomly placed around my room, gain-matched, EQ'd with XT32 and with an 80 Hz crossover applied. Gain-matching CAN be used in a system that achieves flat frequency response. The Geddes technique is not the only technique that can result in flat response.

(Yeah, yeah, yeah, I know... it's too much smoothing for you. Let's not have that conversation again.)

If you want to discuss modal ringing, here is a 2D waterfall of the modal ringing in my system, (which uses gain-matching):



The modal ringing is virtually gone by about 25 milliseconds. (Cyan is -40 dB from the initial signal.) Also, you can see that I have plenty of output down to 8 Hz. It rings longer in the room at the very lowest frequencies, but that is due to pressure vessel gain. Nonetheless, a system that uses gain-matching can still achieve low modal ringing.

Obviously, gain matching is different than the Geddes technique, but the Geddes technique is not the only way to achieve the goals of flat frequency response and low modal ringing. The issue I have with the Geddes technique is that it *only* addresses the frequency response. There are other design goals for a subwoofer system, and the Geddes technique doesn't address them at all. It doesn't address the goal of high output, (full scale Reference Level with headroom), nor does it address the goal of deep LF extension. The way it is described in your write up, (http://mehlau.net/audio/multisub_geddes/), the user places the one primary sub in the corner and then calibrates that sub to the speakers. The other small subs are placed randomly around the room and the levels are increased until they just impact the FR. IOW, they don't add any output, (headroom), to the system, and they are too small to add LF extension. The Geddes technique is limited to the output and extension capabilities of the primary sub.

Some of us want a subwoofer system that can do RL with 3 to 6 dB of headroom and provide useful output to single digits. If those are the design goals for the system, a multi-subwoofer system with identical sealed subs that are gain matched will get much closer to the goal than one "primary" sub and a bunch of 10" subs scattered around the room and turned down below the level of the primary.

Craig