where to point the horn?

[jrios212]

hi,

i feel like this question has probably been asked before but i can't seem to find it by searching.

i have a pair of RB-75s as mains w/ a velodyne spl-1500r. when i plot the freq response of my system as it relates to SPL i notice that the higher frequencies are a little louder than my mids.

right now i have my speakers angled inwards toward me. would you guys suggest that i maybe point them straight instead in order to lower spl at the higher frequencies. the mids don't seem to be affected by placement very much.

will i lose clarity if i do this?

thanks for the help.

jacob

[Ray Garrison]

I've never owned RB-75s, but I've had a variety of horn loaded Klipshes over the years, from KG-4 to KHorns. Except for the KHorns, I found them all to be quite responsive to (or very sensitive to, depending upon your point of view) small changes in toe in angle. And most definately, what worked best in one room didn't work best in another room. A lot depends on how far away you're sitting, how far apart the speakers are, how far from the walls to the sides and behind them, and just about everything else. The only thing you can do is experiment.

And don't be afraid to go to extremes... you're just rotating speakers, after all. In the last big room I had a pair of La Scalas in, I found they sounded best pulled well out from the corners, and toed in slightly so I could just see the inside rear corner of each speaker from my chair. The axis of the midrange horn would have crossed maybe 10 feet behind the couch. When I put CF-4s in the same place, I had to point them almost towards each other to get the correct balance. They wound up toed in to the point where I couldn't see the inside side (?) of the speaker at all - the axis of the mid/high crossing well in FRONT of the couch.

And with each speaker, minor (really, really small) changes in toe in angle had a big impact on stage width, depth and imaging.

What you'll probably find is you can get a position where 3 out of the 4 most important things (to You) are *GREAT* and the 4th is severely compromised, or you can get a position where all 4 are pretty good... and you'll spend about 10 hours / week driving yourself nuts roting the speakers a half inch this way and that way.

Are you married? "Honey, does it sound better *THIS* way or *THAT* way???" can result in extreme eyeball rolling in the head syndrome quite quickly.

[jrios212]

hey,

thanks for the advice. you are right. i could definitely spend hours on this and already have, which is why i decided to post and see what you guys thought.

to answer your questions. no i am not married but i do have a girlfriend who can't hear the difference. honestly, every position sounds great to me. i'm just trying to go for what is accurate.

i sit about 10 feet away from my speakers. they're about 3 feet in front of the back wall and 2 feet from the side walls. i like the way they sound pointed at me. they seem slightly clearer but the highs sound a little louder then they should be.

who knows ... i'll keep on experimenting, but as i mentioned before, i'm just curious what other people do.

jacob

[wuzzzer]

Stereo imaging will usually be better if the speakers are toed in. Some people recommend having the sound cross at an imaginary line just a few feet behind your head, others say to have the sound cross right at your ears.

Fortunately you're not dealing with 100+ pound speakers to move around. []

[oldtimer]

I point my Forte II's to where I can look right down the throats for the ultimate sweet spot. For most of the time they are toed out from that point a little. Smallish room 14x15? and me sitting about 8to 9 feet away from the wall. You should play around with the positioning from time to time, why not? If it sounds good to you that's what matters.

[DrWho]

could you post some of your measurements?

The only way aiming the speaker away from the listening position is going to be beneficial is if the peaks are happening in a region of narrower directivity, and the redirection of the main lobe doesn't 'quickly' reflect back to the main listening position.

[oldtimer]

Are you asking me Dr. Who? If so I will see what I can do. Usually I just let my wife have the sweet spot when we are both watching a movie.

[jrios212]

in terms of measurements.

my room is about 12 x 22. my speakers play out into longer part of the room. my speakers sit about 2.5 feet from the back wall. i sit about 10.5 feet back from that and there's about 9 feet of empty air behind me before you get to some bay windows w/ blinds. also ... my speakers are about 7 feet apart and about 2 feet away from the side walls.

i know that maybe hard to follow. hopefully it makes sense.

also dr. who,

i'm a little confused by your terminology. (my apologies) i'm assuming when you refer to peaks you mean my peaks in sound waves. i'm not sure if i'm in a region of narrow directivity. i guess that could be the case since my speakers are only 7 feet apart in a 12 foot wide room. finally, since i have about 8-10 feet of dead space behind me before you get to bay windows, is that enough space to assume i'm not getting a quick reflection back?

thanks for the help guys. as everyone mentioned, i'll probably just do a lot of experimentation. i was just wondering what other people do and have been successful with.

jacob

[DrWho]

There is a nominal dispersion rating for the speaker which is the angle most of the sound is going to come out of the. But in reality, this dispersion is going to change drastically with frequency. The higher frequency range for each driver in the system is going to be narrower, while the lower frequency range is going to spread out wider. So just below the crossover in the system you are going to notice some narrowness in the lower mids, followed by a really wide dispersion just above the crossover and then followed by some more narrowness in the upper highs.

All that to say, if you change the angle of the speaker relative to the listening position, then you can change what information arrives at the listening position. Only the wider dispersions will get to the listening position while the narrower dispersions travel to other places in the room. So if you have too much of the higher frequencies, then you can redirect them away from the listening position and hopefully reduce them at the listening position.

The trick however is making sure that redirected sound doesn't bounce around the room and end up back at the listening position (which is guaranteed to happen to some extent). So far starters you'll want to toe the speakers in too far rather than pointing them straight out. A good 50% of the sound we percieve is actually due to the acoustics in the room - which means there is only so much you can do with the direct sound of the speaker (direct sound being the signal before any reflections). An early reflection is just the direct sound reflected once - they tend to be large in magnitude and due to the size of our rooms, they can never delayed long enough to prevent blurring of the image.

Just as an experiment, is it possible to temporarily move the speakers into the corner? Or at least closer to either the rear wall or side wall? The reason I ask is because it sounds like you have a boundary cancellation situation being compounded by similar distance to two boundaries. This will suck out frequencies at 140Hz and slightly less at 280Hz - which could definetly be contributing to your lack of midbass situation.

http://www.peavey.com/support/technotes/soundsystems/boundarycancellation.cfm

Are there any curtains available that can be drawn over the bay windows behind you? And what kind of blinds do you have? It sounds like they're having a focusing effect at the listening position. And are the mains in phase?

Btw, do you percieve an issue with the high-end or is this something you just measured? If things sound fine, then you'll need to ask yourself how accurate your measurement technique is.