[davejcb]

Just started playing around with ETF, and either my room or speaker placement sucks ASS. I've got the speakers 47" from the back, and 41" from the sides, in my 17.5' * 16' room. These are PSD optimized shots, where environmental noise is taken into consideration, and was recorded using a Radio Shack SPL meter.

Here's a few shots:

Energy Time Curve
Low Frequency Response
Low 3D Frequency Response
1K-10K

Those room modes look pretty don't they?

Only have one corner bass trap set up so far, I guess I better get crackin'! The reflections don't look too bad from the Energy Time Curve, am I right?

[warnerwh]

Nothing unusual about those measurements. You don't want your speakers at the same distance from the side wall and rear wall. Yours are too close.  Go to the rivesaudio.com room simulator and put in your numbers. This is a lite version of CARA but will give you a good place to start with your speaker position.  I'm sure most people, myself included, were shocked when they saw a frequency response of their room.  Also you should know a perfectly flat reponse is usually not desireable. Most people find it thin and bright sounding, therefore your ears are the only one that matters.  If you use a Radio Shack meter you must be sure to add or subtract for correction. These are available all over the net. Another option is the Rives cd which has signals that are corrected for the RS meter.  Be sure the meter is mounted exactly where you want it on a tripod.  A few inches on way of the other can be huge. Hope this helps. You'll be amazed how much different your system can sound with differing fequency responses of just a db or two here and there.

[davejcb]

Thanks for the advice, I'll try the CARA.

ETF has a mic calibration file for the Radio Shack meter, so that's all taken care of.

I now have traps in both front corners, 4" 6lbs/ft3 FSK. Not a huge difference yet far as I can tell, but I'm sure my speaker positioning is far from ideal. I'll do some more tests and post results.

Anyone else using ETF? Kickass piece of software.

[warnerwh]

Definitely move your speakers and seating position around and listen. It takes time. I took measurements too and just gave up on that as being useful for setup at this point.  I'm still not dialed in. Had my room done for about 3 weeks now.  Have diy traps and five feet out both walls and ceiling are covered with wedge foam as is the back wall. If you get some foam be sure it's at least 3" thick. My room is only 12x17x7 and my speakers have honest bass flat to the 25hz area.  This is the main issue.  The bass can make the treble and midrange sound wrong so it seems to me this is the first area to resolve best you can in the beginning. I'm learning myself still but am no less than stunned how much room acoustics change the sound of your system.  I say screw the cables etc etc til you get your acoustics and speaker/listening position dialed in.  Me suspects most people don't have any idea what they're missing.

[davejcb]

I took measurements too and just gave up on that as being useful for setup at this point.

Why? Have you found that the best mesured curve doesn't match what you hear to sound best?

[Val]

The problem of too much bass in a small room is usually due to room gain reinforcing the deep and flat bass of big floorstanding speakers. Standing waves and placing the speakers too close to walls compound the problem, of course. For a small room it is better to have a speaker whose anechoic bass trails off at about 30 to 35Hz so that room gain flattens and deepens it.

I got this from Adire Audio:

“The room has a tremendous effect on the low-frequency performance of any loudspeaker system. The effect is generally referred to as room gain, although it is actually composed of two parts: boundary gain and pressure-vessel gain. Boundary gain arises from the driver operating not in free space but in a constrained space. That is, the driver is typically referred to not as operating in 4π space free air, but in ½π space in-room. Each boundary cuts the total ‘space’ in half. Thus the floor boundary cuts the space to 2π, the sidewalls cut the space to π, and the rear wall finishes reducing the space to ½π, also referred to as eight-space. Pressure-vessel gain comes from the fact that, below a certain frequency, the room no longer supports standing waves; that is, the room is too small to contain a full wavelength. Contrary to legend, this does not mean the room cannot ‘reproduce’ such waves! Rather, it means that the room is completely and uniformly pressurized by the input signal (we can’t call it a wave any longer, since it is not a full wave). The result is an increase in acoustic pressures in the room that grows as the frequency decreases (more gain at lower frequencies). Note that this effect is the primary reason one can get tremendous bass levels within a car; the gain starts at a relatively high frequency, thanks to the small size of the pressure vessel (the car interior).”

Val

[davejcb]

Here's some measurements playing with positioning, using ETF:

Graphs

I currently have them set to 54" from the side, 48" from the back, which is the green graph.

And in case you didn't see it, two front bass traps vs. no bass traps:

Bass trap vs. no bass trap

[Val]

Even with the speakers well into the room and bass traps, those peaks and the general bass rise surely sound as you say. The room is terrible probably because of the very square dimensions and also because it seems to retain bass energy well (solid, concrete-and-brick type?).

One expensive partial solution for both the bass rise and the peaks could be a subwoofer with equalization like the new Velodyne DD series, or a subwoofer that you could use with a Behringer DEQ2496, while high-passing the 3As with a capacitor.

Val

[warnerwh]

"Why? Have you found that the best mesured curve doesn't match what you hear to sound best?"

You'll find that a flat response sounds quite bright and the lows are thin.  It doesn't sound like real music.  The testing though is very valuable knowledge.  I ended up trying an equalizer in my system.  I believe the equalizer theory of them screwing up the sound is waaayyy overdone.  It helps immensely.  My VMPS speakers are very tunable.  Also I have a dedicated and well treated room but the equalizer can literally transform your system.  A db or two here and there makes alot of difference in the presentation. I ended up buying a used Audio Control C101 III.  If it is doing anything bad to the sound it sure is masked by the huge improvements.  It's almost hilarious how people spend hundreds on wire that is a teency weency less bright or whatever when they should concentrate on their rooms. It takes time but as you go and learn you'll be very pleased.

Don't worry about your room having all the peaks and dips, it's normal.  More treatment and bass traps will help if you can get away with it.  You can try an equalizer if you dare.  After much research I found for analog equalizers Audio Control is a good product.  I bought one just to see what if any help it would be for 40 bucks off of Ebay, the Octave,  and there's no doubt alot of people are missing out on something good.

[Val]

I agree with warnerwh that the case against equalizers has been overstated, just as it was time ago with tone controls.