The Subjective and Objective Evaluation of Room Correction Products

Interesting.

Can you put names to 1 - 6? Didn't see it anywhere.





Full presentation is here:
Presentation

Hi Sean,


Looking at Slide 26, if you ignore RC4 (naked speakers) and RC6, the other 4 RCs all look very similar from 300Hz-20kHz. In other words, they did a good job fixing the speaker's 2 kHz hole. Darned uniform, in fact.

So the preference for RC1/2 comes down to their extended bass performance and spectral rise into the bass. It makes me wonder how these RCs would compare if that element were removed from the equation. How well do these RCs compare wrt small response errors, or phase--if that's an issue, or multi-seat coverage, or room modes? Maybe they all do pretty much the same there (ignoring RC6), and thus would all sound pretty much the same once the consumer could dial in his preferred house curve.

The test certainly shows the value in getting the house curve right. Did it mask the other more subtle performance aspects where room correctors might more importantly distinguish themselves, areas that can only be addressed by the RC algorithm, and not a tone control or EQ?

Awesome,

Another bookmarked link!

Thanks Sean!!

Hi Sean,

Thanks much for your reply. That sheds very new light on the matter. Here I was thinking, wow, isn't it amazing that all their respective mics and procedures gave such high uniformity >300 Hz, since your slides merely mentioned that each was set up per their instructions. That this was not the case is important information.


Lofty goals, and I totally agree with them in principle.

Having never heard a perfectly tuned room, I'm not sure what that actually sounds like, nor if it would it satisfy me over the long haul at my usual playback volume, with my usual content as afflicted by "circle of confusion" EQ design.

If I listen 20 dB below ref, as is common, I need some extra bass lift, for example. Maybe one of the newangled Dolby, THX, or Audyssey auto-loudness gizmos would handle that, but maybe not--or introduce other unwanted side effects. So I like having some manual EQ not only for the loudness offset, but also to compensate for certain recordings where bass is all over the shop relative to others. No one setting seems right thus far.

To me, a final consumer AV processor, with comprehensive facilities, needs a hands-off RC as you advocate, but also some manual means to select or alter the house curve to the tastes of the master of the house. Purists may leave it off, of course. But there's no accounting for taste in the game of making consumers happy. The Reference vs Preference debate is not over, nor is the need to play at other than reference level (whatever that is for music recordings).

I also like the idea that the user has a button that can switch between sweet spot and several seat optimizations. No other RC has that--and it's a major oversight IMHO. Marry this up with BassQ (which has done miracles in my room) and the world is yours!

This is good work at the right time to be doing it. The sample is relatively small, but it's a very good start. You may have already thought of this, but I'll just throw it out there: How about a test with heights and widths processors? DSX, Yamaha & Dolby compared to none.

To some of the people who want a quick set and forget setup, I kind of agree. But to those of us who want to really dial in their HT and music setups, the last thing I would want is an "auto" room EQ system. At least as it stands now, they are just too primitive and past doing a decent "ballpark" job, they still leave alot to be desired.

I have a couple of HT setups including one with an Onkyo NR 906 for the bedroom. The Audessy EQ setup it comes with left ALOT to be desired. Using an Audio Control RTA 3505 and a 20hz-20khz pink noise test cd it showed a +/- db level of almost 11db over the audio spectrum from the listening position. Using the RTA I was able to smooth the audio curve to within +/- 3db with a naturally sloping curve with the bass region being roughly 2-3db higher than the treble range(human ears naturally are more sensitive to higher frequencies, and less sensitive to bass frequencies, thus a more "natural" sound audio curve is to have a slight emphasis in the bass regions). As it stands right now, auto room EQs just cant do this in proficient manner.

Sean,
Thanks so much for your research and for participating on this forum. I highly recommend that everyone bookmark his blog. I have lots of questions about your findings in relation to room eq systems. Thanks for your time.

If you are using well behaved speakers with a flat power response, is there any reason to eq above around 500Hz? Disregarding dynamic eqs, have you found that you can actually "improve" the sound in room?

If you are going to eq a "well-behaved" speaker with room eq, how would you measure this in order to not degrade the sound well above the transition frequency? Should the eq systems allow a way to do a close-mic'ed measurement of each speaker with a short time-window (pseudo anechoic)? And in general, if you are going to eq a room with any speakers above around 500Hz, over what time interval do you integrate the measurement? Have we identified this yet? Isn't this a main part of the problem with room eq systems?

I am highly interested in the new Harman eq. Do you have an expected release date and/or price? Do any of the Harman eq solutions give more weight to the primary listening position's measurement (better yet, can the user adjust the weighting?) or is this accomplished the same way as everyone else by measuring multiple locations close to the primary listeners head? Also, can we expect the new Harman eq to have the equivalent of the Bassq built-in? Also, will the Harman eq solution provide a way to adjust the loudness curve on the fly for poorly mastered sound (TV mostly)?

Thanks!

I am thankful for this info, as I'm just getting ready to buy an auto EQ, but was disappointed the neptune unit wasn't evaluated. My friend swears by it, but I wanted to know if it's better or worse than audyssey.

InPhase, the test indicates that beyond 500hz rooms can still get in the way, though not with the consistency of the sub 500hz region. Another important observation suggests that the testers perceived the RC induced high frequency roll-off as a flat response. I'd suggest that the they would find the 1.5k-6k hole in Harman's uncorrected room a bother even with a sweetened bass EQ.

A different way of attacking the >500hz problem is through directivity. If treble were sent in a beam as opposed to a cone, you might be able to take care of that hole in measurements. Sean, get us some 800 project array measurements in your test room stat! We have to compare them to your B&Ws between 1 and 8khz.

"I am highly interested in the new Harman eq."

First I've heard of this; can you point me to any more info? Googling just turned up old products.

Actually, without knowing which unit is which, this information is only useful for entertainment purposes. It's interesting, but only serves to cast more doubt on the subject.

I wonder if it's the "SFM" that Sean refers to in this blog post:

http://seanolive.blogspot.com/2009/0...81552717575967

Sanjay

Nice read. I myself would seem to 'be in agreement' with these results. Of all of the room corrections I have tried which were limited to Audessey Flat, Front as well as Yamaha YPAO Flat, Front and Natural - I much prefer the Natural setting which provides a slight rolloff of high frequencies.I also cant stand subwoofers that dont go down to 20hz which does make the sound thin in my opinion.

Having said all of this though I believe that the recordings used for evaluation should be disclosed and the study needs to show it was independent of these.

Sound Field Management is the technology used in the Bassq. I don't know if this is usable above the transition frequency. Toole only refers to SFM in his book in reference to bass. It seems that Sean is referring to a new Harman eq that no information has been released on yet.

I don't see this as a conclusion of the test. Can you elaborate more?


Do you mean the dip in the power response of the speakers?


Yep, that is why I use Danley synergy horns.

So RC4 is No Equalization. Which ones are the others?

Thanks

You can kinda guess which is which by looking at the slides.

When averaged over 6 seats, one room correction results in a straight line (slide 23). When measured from the primary listening seat, another room correction becomes a fairly straight line (slide 24). Which 2 RCs does that remind you of in Sean's alphabetical listing? Since all the tests subjects were in the primary listening seat, you can guess which of the two was most preferred.

Of the three remaining RCs, only one incorporates room gain, and it looks like that was the third most preferred (slide 24). Number four is no RC (dotted line). The remaining two RCs not only look like they don't incorporate room gain, but actually seem to start rolling off the low frequencies, which could possibly lead to complaints of anemic bass (sound familiar?).

The identities/order really isn't important, since the most popular may not end up being your personal favourite, any more than the most popular song on radio these days will be your current favourite too. Sure it's likely you'll prefer it, but not guaranteed. Better to listen for yourself (with your system, in your room) than rely on mass preference.

Besides, the study seems more interested in correlating subjective preference to objective measurements (like Harman/Sean had done previously with loudspeakers) rather than creating some sort of ranking for consumer room correction products.

As such, it was more than mere "entertainment" for me. I picked up a couple of things: hadn't realized how similar the various RCs were above 3-500Hz), didn't know how important room gain would turn out to be, etc. It also confirmed something I think we all knew: correction in the lower frequencies is what really separates the various RCs.

One thing I wish Sean had mentioned in his paper is how much manual work they had to go through to get these 'automated' systems to give decent results. Now there's a differentiator that a consumer like me would be interested in. Or course, that might mean naming names, which may not be worth the trouble. Still, I'd like to find out which RC set the crossover to 800Hz.

Okay, about five months ago, Chris Neumann used the DACS 4 on my then new Synthesis® One Array set up with the SDEC4000. Am I correct in inferring that it's now last year's news? or

I won't run out right now and get it done ($$$$ you know), but should I be thinking about a re-cal?

Sean,

"The same room correction technology will find its way into other Harman products in the near future."

Can you be more specific about what type(s) of products (receivers, standalone EQ, etc) and when they will actually be available?

"SFM takes advantage of multiple subwoofers to lower the seat-to-seat spatial variance by taking advantage of acoustical interference to tame room modes. So it only works over the upper operating range of the subwoofers which is typically 80-120 Hz."

Why doesn't it work below 80 Hz?

Per the Harman paper on multiple sub placement, I was planning on two subs on opposite mid walls to cancel/not excite the odd-order modes.