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How Flat is Flat?

I have been trying to optimize speaker placement in my small, dedicated room for the past couple of weeks. I started out by calculating all the theoretical "best" positions following the advice on the Cardas Webstie, the Rule of Thirds (and fifths, and ninths) AND multiple iterations with the RPG Acoustics software. For each possible speaker/listener location, I measured Frequency Response using the Radio Shack meter and several test CD's, and conducted extended listening tests with a variety of music. Leaving questions of soundstagingf aside, I can't get very flat response regardless of where I place the speakers/seat. Response is flat (+/- 3 dB) above 100 HZ and from ~ 40-45 Hz, but plagued with problems in the 50-80 Hz range. The "dip" is in the range of 6 to 15 dB, with the worst frequency being ~ 60 Hz. I have used the SGHT Excel spreadhseet to calculate the room peaks/nodes, and there shouldn't be any nodes at this frequency at any of the seating positions I have tried. I am pretty certain it's not the speakers (SF Guarneri Homage), since they measure flat in an anechoic environment. The room is 14 ft long, by 12.75 ft wide by 7ft9inches long (dimensions chosen using the SGHT spreadsheet based on the fixed height of my basement ceiling). I have minimal sound treatment at this stage (RPG foam at the reflections points, RPG Diffusers behind the listening position, Corner Tunes at the top and bottom corners behind the speakers). My questions is...is it desirable to do better, or am I just being REALLY anal? If desirable, is it possible to do better? How (short of getting a Sigtech or similar)? Would also appreciate any comments on the best scheme for speaker positioning you've tried. Anyone have experienve with the RPG software? The Cardas-based set-ups sound good..but the bect sounding one is VERY awkward even in a dedicated room! AlexC
128x128alexc
carl_eber
1,425 posts
 
Personally, if I had to use no room treatments, I wouldn't set up asymetrically, but would diagonally (going from a 45 degree angle out from a corner in the room). I've done that many times in different rooms, and it always works pretty well (with the necessary experimenting with placement). Both imaging and bass are terrific this way, especially in a setup that is closer to "nearfield". In the end, the symetrical arrangement with first reflections damped, and bass traps in the corners, is always best, however. And the second best way is in the nearfield, out in the middle of the room, with no walls near the listening seat, or the speakers.
sol322
426 posts
 
Carl What you said is a mind opener. I have a room where diagonally I´m missing two corners (transit to other areas no doors) and would really like to try your suggestion.I thought on this posibility but having found only standard placings referred didn´t look further into it. Could you be provide further details like speaker and listening position
alexc's avatar
alexc OP
265 posts
 
All Thank you very much for your replies. I meant to post a follow up much sooner...but work interfered (again!) with my hobby. I have however had a chance to try a few other positions, including a diagonal set up. I've gone back to one the "cardas" set-ups since it gave me the best (for me( imaging and nothing else I tried really smoothed the response. Nearfield listening was excellent for imaging, but felt a bit claustrophobic. Net, I am going to embark on the ASC journey (I am not as bold/brave as Greysquirrel!). Any suggestions on which Tube Traps to use in my room? Or should I follow the recommendation from ASC based on a MATT Test recording? Is it best to buy directly from ASC? I had a qestion for Bagwell on his Sigtech. Does it do analog? My LP collection is large (and still growing), and I have a lot of $$ sunk into my analog front-end. If the Sigtech won't "do" analog, are there other "equalizers" that will w/out completely degrading the sound? Has anyone tried professional parametic equalizers? Thanks!
carl_eber
1,425 posts
 
Sol, all I can say is experiment. Alex, if your timing is right, it's better to buy direct from ASC, although they might not sell to you if you have a dealer in your area...I don't know. I feel that the 16 inch full round traps would be adequate for the corners, and the 16x8 rectangular ones for side and back walls.
pls1
432 posts
 
The only way to use a Sigtech with vinyl is to to use an analog to digital converter since the Sigtech only works with a digital signal. Until next year the Sigtech unit will not accept a 96khz or 192khz digital signal but it does accept a true 24 bit word. Until there is a higher sample rate you will give up too much from a high end vinyl to live with. I own a Sigtech and wouldn't give it up but have basic room treatment to make vinyl listenable. I did a lengthy post a while back if you are really interested. The RPG software, I felt, was a good start. I also found hiring an audio engineer to do in room measurements quite helpful.
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