Something I never considered when it comes to acoustics [Archive] - Audio & Video Forums


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Sir Terrence the Terrible
04-22-2013, 03:31 PM
I have always been a HT enthusiast that has taken room acoustics as a number one issue for getting good sound. All of my rooms whether professional or personal get high resolution analysis via the SIM3 analyzing system(the best room and speaker analyzer in the business), and we make acoustical decisions and adjustments from there.

Since I have been spending a lot more time at my Northern California house, I have gotten around to doing some real work on my multi channel music system, and dedicated HT there - something I have neglected for over a year. Since the HT room and system is not quite finished(subs are being built, and projector has yet to be installed), I just wanted to get the best sound I could from the 7.0 system currently in the room.

The music room is basically a done deal, but I will probably be painting it in the near future, it needs a interior decorator treatment for sure. Since this room is finished, I wanted to focus my findings on this room in particular, because this lesson will apply to the HT room as well.

My multichannel music room consists of 7 custom made mini-monitors(They are patterned after the BBC LS3/5A, but sound as good or better than the Harbeth P3esr speakers), a 15" HPS sub, a 58" Panasonic 3Dpro plasma panel, a very powerful Sony pre-amp amp combo(no video processing but extremely transparent pass through path, no sound decoding except direct DSD stream, others are done at the Bluray player, and an exceptionally powerful high quality amp section at 140watts per channel 20-20khz, 8 ohms, all channels driven). The sources are XA-2 HD DVD player and a Sony BDP-S790 3D Bluray player. I also use my stand alone Audyssey bass and main speaker auto EQ moved from my reference system when I got the new more powerful pro module cards installed in my reference processor. The room is 13x17x10, so when you get the panel, equipment, and loudspeakers in the room, it quite small and intimate.

In this room I brought in my SIM3 system and connected it to the Audyssey stand alones so it can transmit the data needed for correction directly to them. I did 16 measurements in the room to get a good idea where to place the listening seat which consists of a leather(here is the key) loveseat that seats two. Since my speakers are placed in a circle around the listening seat (30 degrees for the L/R mains, 90 degrees L/R sides, and 150 degrees for the L/R rear speakers) measurements showed it was the perfect place in the room based on getting the flattest uncorrected measurement. I placed the sub in the right corner, and that didn't turn out so well in this room. The perfect place ended up being in the center of the front wall where the television was. We have a problem. I ended up bringing in a television stand and placing the sub on it, and the television on top of that. Thanks to the height of the television stand(and its ability to stand a lot of weight) and the sub, the bottom of the screen ended up at the perfect height. Problem solved. Now we get to the real issue.

Once I got the final analysis and and the system tranferred that information to Audyssey for correction, I sat down to listen to the results. At first I didn't like it, so I went back to look at the original pre-corrected measurements. It showed multiple early dense reflections in the mid to high frequencies not from the walls, but from around the listening area. It never occurred to me that my leather loveseat was creating reflections that not only affected the measurements and its correction, but what I heard afterwards. If you have a cloth covered listening seat you probably don't have this problem. My answer to this was to get my favorite wool blanket and cover the seat. MAN, what an improvement! I re-ran Audyssey and the sound improvement was pretty darn dramatic. I now have that acoustic bubble I so love about multichannel. No sonic holes, big soundfield, and specific effects placed very clearly in specific places in the soundfield. Dialog sounds very natural and clean, and boy does this system play loud in this room!

I posted this long winded diatribe to note that you will run into a lot of problems when trying to correctly set up your HT, entertainment room, or living room for that matter. While I expect some issues to crop up, I never expected a leather loveseat to be any problem.

If you have any reflective surfaces(which includes the listening seat itself) around your listening position, it is best to move them or you will be hearing spurious reflections along with your great audio.