Speaker placement

Posted: Sat Nov 30, 2002 7:23 pm

I'm really crammed for space, the only way I can get my JBLs spaced evenly on either side of the table is to have them facing each other.

Is that Sacrelige? Will it compromise the quality of my sound?

The only other option I have is to put one a few feet away near the other side of the wall.

Any help would be greatly appreciated.

Posted: Sat Nov 30, 2002 8:25 pm

Yes, yes it is sacrilege. Sorry to be soooo harsh, but it seems your putting the cart before the horse or rather the horse behind the cart! The first thing you want to do is place your speakers. Everything else in the set up should be to accommodate the speaker placement. Speakers should be set up to form an equal triangle, with the same distance between the speakers and you. That is, if the speakers are 4 feet apart each speaker should be four feet from your head so it forms an equal triangle. No ifs, ands or buts! Set in stone, period! I Hate to be the bearer of bad news but it sounds as if you're going to need to completely rearrange the room so that you can get those speakers where they belong. Try to have fun! ........Fats :w:
edited once for spelling

Posted: Sun Dec 01, 2002 10:13 am

Thanks, great tips, I already started moving stuff around again.

According to what you said, if the speakers were three feet apart, they would have to be three feet from my head also? or is it specifically four feet?

Posted: Sun Dec 01, 2002 10:30 am

Four feet would be better but if three is all you've got that will have to work. It's hard to hear stereo separation at less than four feet apart and at three feet sometimes the sound from the tweets and the woofs haven't had enough distance to come together. If you can get four feet, that would be better... but if you have to do three that is certainly better than them being on the sides pointing at each other! ............ Fats

Posted: Sun Dec 01, 2002 11:22 am

Thanks, I'll try my best, I might almost make four feet.

Posted: Thu Dec 05, 2002 2:20 am

Basically, if you can't make a triangle... forget TRUELY hearing. *you, the speakers*

Posted: Fri Dec 27, 2002 6:48 am

Okay, so I finally got them four feet apart and four feet from my head, but I'm not sure if they should be facing directly forward, or if they should be angled slightly inward.

Posted: Fri Dec 27, 2002 9:28 am

Stone B
Angle them in so thet are facing directly at you when your in your listening position. fats

Posted: Sat Dec 28, 2002 8:37 am

Angling them now.

Should I have them sitting on some type of padding? The guy at Guitar center told me if I sat them on some foam, I would get more bass because the vibrations wouldn't go through the table or something. However, I think he was just trying to sell me the extra foam... which I didn't buy.

Posted: Sat Dec 28, 2002 9:15 am

Fats has a good point but also try this:

One of them you will like better.

Fist of all I like all drivers on the horizonal plane. This means laying them on their side. Both woofer and tweeter will now be at ear level.

Second, thie has been some debate on this but MY personal preference with the speakers on their side is to position them with the tweeters on the inside of the image. Reason for that is that the tweeters are slightly closer to you and in the highs is where you get all the imaginig. Putting the tweeters on the outside means the delicate tweeter tones must travel through the woofer wave. Also high frequencies reflect off side walls, tweeters on the inside of the image minimalizes this reflection.

3rd, I like the speakers to fire slightly past me. IF you hold both arms straight out (side to side) , I like them firing at my elbows and if you have some distance.. even slightly more toward your wrist. The reason for this is that the highest freqencies imminate from the very center of the tweeters only in a straight line. Many manufactures tweak their crossovers so at near field at 12K hZ point source (meaning dead ahead of the tweeter beam, right in front, the 12K hZ is about 4dB up. This is industry standard I am afraid so to get truly a flatter freqency response, many loudspeakers tend to balance better at 15 degrees off axis. Cedats Tannoys that are coax compression drivers imbedded onto the pole piece of the woofer does not go by this rule but a 2 way and even some 3 ways do.

It will not hurt to implement these factors. Use familiar music. Give each test about an hour to get use to it. try it at all volume levels.

About the foam.

2 schools of thought:

Isolation
Ridged coupling.

ISO:
The foam will keep the cabinet resonances from exciting the unit the speakers are mounted on. This is ok...to a point. I would experment with towels first to see if the vibration is reduced to the stand they are on. If so, this will keep the stand from making noise that can deteriorate from the overal sound.

Ridged

This technique offers outstanding benifits of coupling the speaker to the stand. The stand must be acoustically dead. A ceramic collum filled with sand is the cheap way out. The the bottom of the stand has 4 spikes on it that literally sticks either into the carped to the cement or wood, or directly to the wood. (Floor) If you have a prized wood floor, get a square of wood cut (your choice) for the stand spikes to press into.

This is called Mass coupling.

The advantage is the entire vibrations are now transmitted to a dead surface and stopped before they can cause havok.

Sorry so long but the art of loudspeaker placement is very advanced. On my monitors, If one loudspeaker is 1/4 of an inch closer to the rear wall, I can hear it in the imaging. Do your distances in a precison way. Make sure the speakers have no ovstructions around the sides or anything to block the pattern. Make sure the left and right side of your room is symentrical.

I hope you can implement some of these things and report back which way it works best for you.

The Cedar method is the quickest way to begin tweaking. It will get you on the right path.

Just experiment with this. You will be amazed what 1 inch of movement can do for the sound.

Posted: Sat Dec 28, 2002 10:01 am

Bill...I always find your posts extremely useful and I even find myself copying some of your comments into Word, printing them, and them gluing them onto index cards! You da man!!!

But come one here...1/4 inch??? <grin> One inch I might be able to buy, but 1/4"??? If this is true, you have better ears than I :c: (which goes without saying anyway, I guess...)

Posted: Sat Dec 28, 2002 10:21 am

...I should have said an 1/8th actually but I left it at 1/4 since I do not want to appear to be messing with peoples heads.

Actually yes.

Look at this:
If the sound arrives at my ears of a 10kZ tone that is mixed for mono.

Lets say that sound travels roughly 1250 feet per second and this is 10000 cycles/sec full 0 to 90 to 180 to 270 to 360/0 degrees. Each one!

The length of the 10000hZ wave is 0.125 Feet or lets round that to an inch for the sake of simplicity.

Now, if 1 cycle of 10000 hZ is an inch long and I move the speaker 1/4inch back from absolutely equal distances..(provided your speakers are deadly accurate which mine are) then 1/2th of the top wave which is 90 degrees is behind the other. When you really dial in a set of speakers and you are sensitive to phase as I am, the quarter inch is so audible I have to move my head back and forth and say..damn it is not in phase anymore..then I measure..surely I can find the sweet spot and lock onto it. I measure the distance again and it is off. So I correct it and the problem I am hearing magically goes away and the now 10K hz tone is coming from a knife blade dead in front of me that seems about 5 feet behind the monitor that is in front of me. Just moving a light fixture is audible and I must turn the overhead fan off. It drives me ape shit with all those reflections beating around.

With the right system, with training on what to listen for, with the right acoustics, super matched speakers, yes, phase is in my face. It does annoy me that I cannot move much when listening critically.

I know this sounds like snake oil but this is why I must leave my system on at all times, have controlled voltage, calibrated speaker cables and calibrate the system every day before a session.

Strange as this is, a 0.2dB difference in right to left channel balance moves the center image what appears to be about 5 inches away from center.

Heresy is what it all is.

It becomes a pain in the ass at times. One day I hope to lose this ability..

Posted: Sun Dec 29, 2002 5:50 am

I think I'll try all of these suggestions.

Posted: Mon Dec 30, 2002 10:04 am

Not to throw paper into the fire .. but after all of this placement issue .. you also need to know what you might expect from these .. so, one simple starting point would be to plot the room. To do this you need math: f =1130/(d)x2 .. so frequency = 1130(speed of sound)/(distance)x2 .. frequency = 1130/(21')x2 ... 1130/42=@27hz. This would be the 1st room mode for say a 21' length, the 2nd for that 21' length = 27+27=54hz, the 3rd = 54+54= 108hz, the 4th = 108+108=216hz. Do this up to say the 12th set of calc's.
Now, do the same for the width of the room, and also the height of the room, take these three and plot a curve to see what frequency(s) are close to or the same .. these would be the standing waves you will have problems with .. the less the better, and the lower the initial starting room mode number for each dimension, the better. If you did this for say an 8x8x8 room, you'd quickly see why a square room is a problem.
All this being said, also keep in mind that the numbers will not be exact due to whatever construction was used in the room and whatever else is in the room .. however, it will afford a fair idea of what would be an easier room to record and/or mix in.

Please correct my math guys if I'm off in the numbers above, but I believe it's correct, and certainly the principle is valid, you agree??

Posted: Mon Dec 30, 2002 7:00 pm

This is a bit OT, but related nonetheless...

Was curious if anyone has any opinions of the Auralex "Mopads", which are those foam pads to put underneath of monitors to decouple them from their base. It seems to me that these will defeat the purpose of having the rigid platforms that attach to the floor with spikes.

What is the opinion of the pros on this? Bill?

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