Pros and cons of corner placement - diyAudio
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Old 3rd May 2006, 12:34 AM   #1
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Default Pros and cons of corner placement

I currently live in a studio apartment while attending college and im contemplating putting the tv in the corner with the mains on either side. The system is a sat/sub arrangement where the mains are Bose single cubes with the bass module completely removed from the equation. The crossover is internal to the receiver(kenwood VR-7070) and the sats are run full range and crossed to two technics 12's in a clamshell design.
Now the question I have, before I rearrange the whole place which im not looking forward to is:

1. how will low frequencies in the 100-200hz range be affected by having the speakers a) against each wall, and b) a couple of feet off the wall? Well all frequencies I guess. I ask about the 100-200 range specifically because w/o the bass mod. the system is lacking there. Interestingly the overall sound is far superior w/o the crossover/woofers which are in the bass mod.

2. How significant are each of the walls going to be, the left speaker will be in front of smooth concrete and a window covered by a moderately heavy curtain, the right will be in front of a very rough and randomly shaped concrete block wall (yes my apartment is all concrete)

3. Having the speakers near the wall firing from the corner would bring the first reflection and the direct sound into very close time alignment right? In addition it would increase the distance to the next reflection which should be the wall adjacent to me and the sound would reflect away from me right?
4. Finally any thoughts on the overall affect on image depth and width?
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Old 3rd May 2006, 01:06 AM   #2
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I just realized something, I used a nasty four letter word in my original post. My apologies for offending your sense of fidelity, I bought these before I knew the truth about B***. I am in the process of planning some new speakers so bear with me, but until then I still need to optimize this system, I already ditched the xover and the resonant boom box. Its a start
Thanks in advance.
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Old 3rd May 2006, 01:30 AM   #3
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Quick Setup would be to place your sub in the corner for maximum bass. My guess is your setup sounds better w/o the bass x/over because it crosses too low. Your satellites probably don't play much below 200 Hz. The placement of your satellites isn't going to drastically change the bass response of your setup.

The curtain on the left is probably a good absorber and the rough wall on the right is probably a good diffractor (though not over a wide frequency range). I would try just move your satellites and try out different listening positions until they sound right to you. If reflections are a problem toe in might help. Since your room is all concrete a thick area rug, and some strategically placed bookshelves might not be a bad idea.

Good luck, Roger
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Old 3rd May 2006, 01:33 AM   #4
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Put the sub in the corner and move the li'l guys away from the wall; speaker stands are your friend. If they aren't designed for it, wall placement will thicken up the upper bass/lower midrange, not to mention have some interesting imaging anomalies. Asymmetric reflecting surfaces will be a near-guarantee of poor imaging. Getting the sub and satellites to transition smoothly is enough of a challenge without placing them suboptimally!

Since you're at a diy forum, I'd suggest getting rid of the built-in crossover from your receiver (which is unlikely to be optimal for the speakers) and build one yourself more tailored to the speakers you actually have.
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Old 3rd May 2006, 03:52 AM   #5
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Thanks for the input guys, but I think you missed the point of what im trying to accomplish, partially. I have plenty of subwoofer bass, and the sub sounds bad in the corner in this room. SY the 100-200hz sat. problem is what im trying to address, I was hoping for "corner loading" of the sats. Actually, room space is what im after here, im trying to find out what the acoustic problem/benefits will be.
The sat is a single 2.25 inch driver operating full range, until I build new full range 3-way speakers, custom crossovers are out of the question.

SY the sats actually are designed to be against the wall as they lack baffle width, B*** designed them for hanging on the wall. I have them on stands now(old 3-way technics towers actually) and with the crossover they rolloff the high end early, w/o the xover they extend up nicely, I havent measured the FR yet though.
-Asymmetric reflecting, surfaces thats a good point, that kind of ends the debate of corner loading in my room unless I treat the walls which im considering anyway.Do you agree that wall treatments might help?

Quote:
The placement of your satellites isn't going to drastically change the bass response of your setup
Are you referring to the subbass <100hz or the 100-200hz, range.

Quote:
My guess is your setup sounds better w/o the bass x/over because it crosses too low.
Actually the xover components are really cheap and are degrading the sound tremendously, dumping that improved every facet of sound except without the bass mod. there is nothing producing the 100-200hz range smoothly. With the xover and mod. the 100-200hz range was flat, but the rest of it was crap, the imaging, top octave extension, clarity of midrange etc. Sensitivity is increased significantly w/o the xover as well, I have had to crank the sub up 4dB on the receiver to match the sats now
As an example this one track with a drummer 10ft back from the guitarist sounds 1ft back w/ xover IF you listen very carefully, running sats full range and the drummer sounds about 6-7ft back.

Good point roger, on just moving the sats now and leaving the everything else where its at, I cant watch movies but I can run some imaging test tracks.

BTW, I know im pushing the limits of the sats here but until I build the new stuff....

Thanks for the replies,
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Old 3rd May 2006, 04:58 PM   #6
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Default placement

Well if you want to do the corner augmentation of the sats thing, I suggest you go with the absorbers idea, thick as possible right next to them... will hardly affect the 100 - 500Hz bit, but would open up everything else... i.t.o clarity - It may however start sounding a little lacklustre, because of the lesser "energy" from the high mid and up... Just a thought - the thickness of the absorber (depending on type) needs to half the wavelength... to have any effect in otherwords 1kHz you need 17cm thick / 6.5 Inches... 500Hz 34cm/14inches... Mine are rolled up Polyester fill (diam 40cm) but are only used for first reflection damping...
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Old 4th May 2006, 03:11 AM   #7
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Quote:
It may however start sounding a little lacklustre, because of the lesser "energy" from the high mid and up
That's good actually, that would balance out the sound nicely.

Quote:
the thickness of the absorber (depending on type) needs to half the wavelength...
This is interesting, where can I read more on this?
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Old 4th May 2006, 08:35 AM   #8
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Coolness

Here's a few... can't attach html, so the nice ones I kept can't get pasted...

google: acoustics

www.acoustics.org/

www.faqs.org/faqs/physics-faq/acoustics/

www.phys.unsw.edu.au/music/

google: diy acoustics

www.geocities.com/jonrisch/a1.htm

www.gearslutz.com/board/showthread.php3?t=12625

www.johnlsayers.com/phpBB2/viewtopic.php?t=5930

www.diynetwork.com/diy/hi_family_room/ article/0,2037,DIY_13912_3471072,00.html

google: How to build a better Basstrap

www.ethanwiner.com/basstrap.html
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Old 5th May 2006, 07:21 AM   #9
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agrobler thanks for all of the links, ill check those out.

Just a follow up for all of those who took the time to respond, I put the speakers firing diagonally ~90inches away from each other and ~15.5ft from listening position and listened to many test tracks.
The most noticeable difference was the lack of reflected sound reaching my position as I suspected might happen. In fact I had to crank the volume up significantly to restore "normal" levels Normally I listen at ~-30 on the receiver, but last night it was up to -20 to -17 and sounded good at -10 which is louder than I have hever had it.
they sounded more crisp and clean, but of course the 100-300hz region was actually worse! They sounded a little more anemic than before.
Sound stage was impressive although skewed about 2ft to the right due to the bare wall there. Putting a an exotic thermoelastic sound absorbant foam pad (memory foam pillow)behind the right speaker fixed that though. Depth could have been better but the left to right imaging was great, I was actually able to resolve the placement of individual drum and symbol components.
So this experiment taught me the importance of symmetry and how reflections affect acoustic energy, clarity and imaging.

These walls need covering!!!!
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Old 5th May 2006, 09:08 AM   #10
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Default some more thoughts

Don't cover the whole place... unbalances the place, will just sound dead... Rather use wideband - i.e. thick absorbers at the first reflections... also first reflections on floor - this often causes dip in midbass... if you can absorb that low, couch maybe?

The lower down the spectrum you absorb, the better your vocal and other lower instrument imaging will get... right now you only absorbing above 3-4kHz - if I'm picturing right.

The lack of 100 - 300 Hz, will make it sound small / soft. Are they corner placed? Corner placement and floor absorbtion only help there... or taking values in tossed X-O and replace with nice comps... maybe not worth it... Also maybe move closer to sats - thats a huge distance to cover for 3" drivers in the midbass.

Edit: at this distance you may only be hearing the reverberant field, for better or for worse...
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