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In Reply to: RE: Bloody Peaks... posted by Ethan Winer on September 21, 2012 at 12:42:39
Given my room measurements, I have placed my speakers on the Cardas ratio (7 feet from the front wall, 4.4ft from the side walls) on 26 inch stands. The front corner of the room has a 4 inch thick 3ft x 2ft panel, same set of panels on the ceiling reflection points (suspended 5 inches from the ceiling), 9 inch tube traps exactly behind each speaker on the front wall, 9 inch tube traps on the side-wall reflection points (I know this ain't sufficient ), a 13 inch tube trap exactly in line with the listening chair on the back-wall, tri-corner traps (4 inch thick) on all the ceiling tri-corners. All panels & tube traps made using 4 inch thick fiber-glass. Listening position also on Cardas ratio at an equilateral triangle with the speakers.
My question is, HOW can we diagnose if the peaks are caused by the Room & not the system itself???? Every interconnect, power cord, speaker cable, component, isolation-feet change the tonality of the perceived sound. Which means they have their own flavour, thereby changing frequencies at some point or the other. Is it practical to always blame the room & the room-modes for any peak or null?? My amp sounds terrible kept on a wooden Mdf table, but the same amp sounds way balanced on a sand-tray kept on the floor. Every piece of gear is inducing some ringing & character. Then how do we pin down the culprit????
Junaid
Follow Ups:
You pin down the culprit with proper scientific tests. Do you have a computer connected to your system? If so, I recommend the freeware Room EQ Wizard software. That will measure the response of your entire system, and then you can see what happens as you change this or that.
I can tell you that the "flavor" of wires and iso products affects the sound 1/100th or less compared to the speakers, their placement, and the room's acoustics. Further, the location of the tube traps you mentioned is far from ideal. They'll do the most good in corners, at least so far as bass peaks and nulls are concerned.
--Ethan
Yes I have a computer connected to my system as well. I will try that. I had tried earlier as well but the REW seemed a bit difficult to configure. I also have a Radio Shack spl meter for the same. It's not quite possible for me to keep the tube traps in the rear corners because of the doors at those points. The problem with my room has ALWAYS been a forward midrange which stands out from the rest of the frequency spectrum. no matter which speaker or amp I have tried all these years, the issue still remains. So I'm at least very sure this has got to do with the room.
Do u think the Cardas speaker placement is a good idea for bookshelf speakers ? If not, then where does one start? Do I need to fix the listening position first & then place the speakers, or vice versa? I was very impressed by your website a few years ago & started making the panels. Anybody could take Ur word when it comes to Room acoustics. Given the details already, what is the first thing you suggest? Re-do the speaker placement or move the existing panels elsewhere ??
Junaid
The first thing (for me) is to better understand what you have now. Can you post a photo taken from the back of the room toward the front? Your first post complains about bass peaks, and now you say it's the forward midrange. Without seeing what you have or, better, seeing an REW graph, I can't be very specific.
--Ethan
Tried to take measurements using the Room Eq Wizard using an ESI Juli@ soundcard which has dedicated left/right RCA line level inputs & outputs. I'm a bit confused with one thing here. The diagram on the page shows that the output from the spl meter is connected to the Right input of the soundcard & the Right output of the card connected to an amp. But it also shows a loopback connection between the left inputs & outputs of the card which are connected for calibrating the soundcard itself. Is this correct ?
On the same Help section it's written that :-
"The left channels of the soundcard are normally not used and are simply never connected. To compensate for any weakness in the soundcards response, we create a calibration file using the right channel of the soundcard, by use of a loopback cable and a special one-time-only routine that saves that file into REW. That loopback is removed after running that calibration routine and then the right channel is used for all testing. "
So is it better to leave the Left inputs alone without using them & just use the Right channel to take measurements? As written above, do I first connect a loopback between the Right in/outs just ONCE to create the calibration file, & once it's done, I remove the loopback connection, & hookup the Spl & Amp to the same for testing ???
Junaid
I don't bother using a loop-back connection because modern sound cards are flat enough they don't need to be compensated for. As for inputs, either one is fine, but for outputs you should measure with both speakers running, then with each individually.
--Ethan
What mic are you using with REW?
Sorry, I missed this earlier. My main measuring microphone is a DPA 4090, but you don't have to spend nearly that much for a good room measuring microphone. See this:
Comparison of Ten Measuring Microphones
--Ethan
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