Author Topic: Acoustic session  (Read 2659 times)

Offline richidoo

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Acoustic session
« on: April 25, 2008, 08:21:01 PM »
I had some fun at a local audiophile's house today, he invited me to come over and see what could be done to improve his listening room acoustics. He has Spendor S8e, Music Reference RM-9, Wadia CD player, and CJ PV-15 preamp, Nordost ICs and DHLabs SC. The gear sounds great. The SPendors have great bass, and a very pure sweet silk dome tweeter. The amp was the star for me. I learned that EL34s don't have to sound like electric guitars.

The room is an apartment's 2nd bedroom, about 12 feet long, 10 feet wide, 8 feet tall, guestimate. He is sitting 2 feet from the rear wall, with speakers baffles about 5 feet from front wall. Maybe 80 degree angle between speakers.  He has tried every possible setup in that room, nearfield, sideways, everything, and likes it how it is so we just added some treatments and fine tuned. I told him when he buys his own treatments the room will change and he might be able to get further away from the rear wall.

I sat down to listen before changing anything and he was playing a Jobim compilation with Sarah Vaughan singing a tune. She is my favorite singer in the world, and I didn't even recognize her. The most famous and wonderful female singing voice of all time, next to Mirella Freni maybe. The sound was confused, blurred, lots of midrange reverb, bass was muddled, rumbly and very indistinct. There was no attack on anything. Forget about tone.

First brought in the GIK tritraps. Placed them upright in the front corners. Bass improved, midrange got clearer but more aggressive, not pleasant to listen. So we laid them down on the floor with one end even with speaker baffle, extending toward front wall. Better.  A little is good, a lot must be better, so we moved them up so one edge is even with the baffles but extending into the room toward the rear wall. Bingo. They were about in the middle of the wall, and the bass tightened up, smoothness in the lower mids, no harshness, no deadness. Keeper. Some sidewall reflections were getting mopped up too

Then I brought in the pair of GIK 244s (we hid everything outside the room while getting acclimated to the original sound.) Placed them on the first reflection points behind the speakers on the front wall. I heard an improvement in the mids which I liked, but the dreaded striped wall effect made it hard for him to hear the improvement, same thing happened at my house. The front wall wants to be fully treated not just stripes with specular running wild between. We moved them close together in the center, better, but still not right compared to nothing there. In the corners on front wall, better still but could still hear the stuffiness. I had the same experience at my house. I couldn't find a pace on the front wall where they did not screw up the soundstage. These 244s are extremely powerful, so finding the right place is not always easy. Across the front corners to improve bass trapping was WILD. The bass became very loud and ultra clear. But the rest of the freqs sounded too soft in comparison, so I knew there is a lots of bass trapping potential still to do, but not with this one pair. We tried a couple more places including traditional side reflection points lying horizontal on top of the Tritraps and vertical, that made better clarity, but still not right compared to what he is used to. He was listening intently not verbally describing what he was hearing to me. So I was just making changes according to my understanding, hoping for a positive reaction to something.

Finally we tried them on the sidewall, upright, same distance from the front wall as speakers. So as to absorb as much sound reflecting off the nearby side wall into the room as possible. I thought this would "quiet' down the general room reverb as much as possible by getting the absorbtion closest to the speakers at the closest wall. It worked! The room came alive. Midrange clarity, treble delicacy, lateral imaging, everything improved suddenly. My friend loved it. He was about to give up on those 244s they were so powerful and so many tries were just not getting it for him. The tritraps were placed "easily" only because we got lucky earlier and they have fewer places they can go. He was mighty impressed with the improvement that the 244s gave. I told him the price of the GIK treatments he was hearing and he was flabbered. Room sensitivity was not too affected, but the reflection spraying was cut off at the most efficient point where the speakers are closest to a wall, killing some of the reverb and letting the direct sound be louder in relation to the room, at least that's what I assume is happening. First thing we had to do was turn down the volume! A good sign of moving in the right direction.

Then I placed Carl's pair of RPG 2x2' 1" thick FG BAD panels behind his seat on a box, leaning up against the window. I was listening at the time,  and it felt SOOOO good to have that window/wall reflection gone, without feeling too dull. It was a warm luscious feeling typical of the BAD panel diffusion. I didn't say anything about it. Previous attempts to place these little BAD panels at the front of the room he didn't even hear a change at all so his impression of them was close to worthless. Then he sat in the chair and was digging the changes we made with the 244s. Then when he got used to it, I plucked the BAD panels out from behind his head. AHHH!!! Put them back! That was the quickest reaction he had to any change I made all day. It was also the least subtle. Funny because it is not a blatantly obvious change, it is just a feeling of goodness behind you, not a distinct sound. But killing off that rear wall reflection brought out details and tone that weren't there before. A nice touch. I think that the BADs effect was not noticable earlier before the GIKs cleaned up some of the major mess. Once they were in place a lot of subtle details in the music were audible, and so too the BAD diffusion. But it was also only a foot away from his head so a lot easier heard. The nice thing for a close rear wall is it doesn't sound absrptive at all, so it is not noticed even when it eliminates the rearwall midrange reflections.

I left everything with him to play for a week or two. I told him to fart around with them and learn. He said I think they are fine where they are! It felt good to accomplish such a great improvement with a few hundred bucks of parts. His system value doubled because now it sounds like a truly high end system that it is. He's getting his money's worth.

The biggest problem that still remains to be fixed is the soundstage depth. That's a function of front wall acoustics and also the amplifier. MR has reputation of being one of the best soundstages of any amp ever made, so I think that's not a problem. Roger just overhauled this amp a few months ago. But the front wall remains totally untreated, and that is definitely screwing it up. So we're gonna work on that too. I told him about my experience that led me to believe that whatever you do, you have to do it to the whole front wall. Or at least treat the whole wall even if using different things. But large areas of specular (untreated) mixed with absorbtion are not a great combo IME. I used to think absorbtion on the front wall was lousy in general, until I built the hut out of pure absorbtion and it was the most incredible soundstaging I have ever heard! Totally surrounded by absorbtion. Then I realized it was the stripes that were annoying, not the absorbtion. At least the whole area between the speakers needs to be the same, treated or untreated. Above and out to the outside of the speakers is less important IME.

I played my Dvoral Quintet CD and heard good tone, but little sense of space. On the ride home in the car the space and tone were incredible, so there is work to do there still. I think the GIKs are curing a lot of very bad things as they were designed, but the small room is sensitive to powerful absorbtion and I could feel it in the space perception. More placement fiddling is needed. I think the rear corners would be a great place to add more bass trapping, but there is furniture there, which he might move now...

So we had a fun time, and learned a lot. Just wanted to share my day.

Offline stereofool

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Re: Acoustic session
« Reply #1 on: April 26, 2008, 02:50:02 AM »
Aahaa...Acoustics Man strikes again  8)!!

Rich...I might just have to breakdown and have you over...but I don't know if my pocketbook can afford the experience  :rofl:!
Have you ever noticed.... Anyone going slower than you is an idiot...and anyone going faster than you is a maniac?

Offline bpape

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Re: Acoustic session
« Reply #2 on: April 26, 2008, 06:15:42 AM »
Hey Rich.

Did you retry the Tri Traps upright in the corners after you did the rear wall and side walls?  You might be surprised with a very different impression.  I'm quite sure up front down low is helping too - just different things.  I suspect the upright might help a bit more with imaging. 

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Offline richidoo

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Re: Acoustic session
« Reply #3 on: April 26, 2008, 10:08:09 AM »
Thanks Bryan, yeah we tried the tritraps upright behind the speakers in the front wall corners very first thing, with nothing else in the room, and then again after the 244s found their best place next to the speakers on the sidewall. Bass improved over the horizontal sidewall position in both cases just as you said, which is why I tried it there first. I have your advice tapelooping in my head :D  But they were doing more for the higher frequencies too when placed in the middle of the room. Reverb was most noticable problem, so absorbtion in the middle seemed to be the best use of the small amount of medicine we had available, while trying to keep the EQ balance sounding natural. He knows he needs more. I'm hoping he will move them around and learn what does what.

I'd love to come out Steve!! You have my dream system so even if we aren't productive with acoustics it would be fun to hear your tube and ribbon exotica!! Don't worry, I'm even stingier than you.