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#169080 - 06/15/07 08:04 PM Re: Graph testing again, I'm confused, so is mojo [Re: Wid]
a401classic Offline
connoisseur

Registered: 11/29/06
Posts: 1168
Loc: Alpharetta, GA
OK, Got my graph. Looks more like an EKG, and I don't mean dead. Having trouble with excel and getting a log scale to only display 10-300. It's stuck on 10-1000. Anyway, I'll try to get it uploaded to my home page and link it back. It was interresting running the test tones and where pockets of sound seemd to "hang out". There were several 2-3 Hz groups of angry hornets in various parts of the room. Also found it interresting to watch the sound level drop on the meter and hear it louder in my ear 3 feet away. I did find a nice way graph, though. I put the sound meter on the back of the couch in the sweet spot and rested my laptop a couple feet away so I could see the display and just entered the spl directly into excel. No copy and regurgitate.

Scott
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Scott

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#169081 - 06/16/07 07:17 AM Re: Graph testing again, I'm confused, so is mojo [Re: a401classic]
a401classic Offline
connoisseur

Registered: 11/29/06
Posts: 1168
Loc: Alpharetta, GA
Here we go...



This is with pink noise at 70 dB. What do you all think?? Like an on/off switch, nothing at 16 Hz then the driver was flying at 17 Hz. I have not tried Mojo's 12 o'clock setting to see if there is something at 10 Hz, and even at 17 Hz I did not see the drivers of the M80's moving - may have to go back and take a closer look.

Scott
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Scott

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#169082 - 06/16/07 08:33 AM Re: Graph testing again, I'm confused, so is mojo [Re: a401classic]
jakeman Offline
aficionado

Registered: 10/03/05
Posts: 851
Loc: Toronto
Is this with the M80s large or small crossed at 80hz? Where is your sub in the room and relative to your mains. Don't worry about the low end sub response, the 500 has a brickwall filter at 19hz which is why there is sudden output.

Overall there is room for improvement. You are running the 500 very hot compared to the M80s. One quick suggestion: raise your sub trim adjustment to full, which would increase output by 6db over 33hz then lower overall sub volume by 10db. That should blend the sub/sats better and give you smoother response below the crossover point. Also try reversing phase to see if that helps smooth response.
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#169083 - 06/16/07 08:09 PM Re: Graph testing again, I'm confused, so is mojo [Re: jakeman]
a401classic Offline
connoisseur

Registered: 11/29/06
Posts: 1168
Loc: Alpharetta, GA
John,

Thanks! Apparently I was completely out of whack. I've played around with x-over and sub settings I so much I forgot to check calibration before starting the test cd.

So now with everybody at 75 dB - sub bouncing between 68 and 77 dB, mains set at small with 80Hz x-over, set to stereo, and pink noise at 75 dB +/- 3 due to sub fluctuations we have a new chart. But John also asked about sub location ...



Sub is about a foot away from back and right wall.

Now for the much improved chart... Blue, previous trace. Pink, calibrated trace.



What a difference! It looks like the sub is still a bit hot. I've only got the gain at 7:30 and calibration is maxed out at -10 dB to achieve ~75 dB. Had to raise the other channels significantly (+4 to +8 dB) to match the 75 dB.

Now it's time to experiment with some "treatments".

Scott
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#169084 - 06/16/07 09:38 PM Re: Graph testing again, I'm confused, so is mojo [Re: a401classic]
jakeman Offline
aficionado

Registered: 10/03/05
Posts: 851
Loc: Toronto
That does look better Scott. You are getting significant boundary reinforcement in the corner which is why the deep octaves are so loud. The corner placement is also causing more volatile nulls and peaks.

If its practical it may be worth experimenting with placing the sub on the left side of that neat looking entertainment unit between it and the M80. Also check the other side of the entertainment unit. Both spots have less boundary reinforcment. Once there check the phase . You should have more room to calibrate as well.
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#169085 - 06/17/07 12:06 AM Re: Graph testing again, I'm confused, so is mojo [Re: a401classic]
bridgman Offline
axiomite

Registered: 08/25/04
Posts: 5279
Loc: Bowmanville, Ontario, Canada
Looks much better. Flipping the phase switch might help with that dip at 75-80 hz, as John suggested further up the thread. If you have already flipped the switch, flip it back

Do you have room dimensions around 11 and 19 feet ? That's what the first two peaks seem to indicate.

The 135 hz dip seems to relate to having the fronts of your speakers a bit over two feet from the wall. Make sure you don't have similar distances from front of M80 to both back and side wall -- if you do, make 'em different if possible. The changes John suggested for sub placement would probably also help that 135 Hz dip.

Note that putting the sub in the middle of a wall can significantly reduce the bass spike that you get from the room mode corresponding to that dimension, ie "nasty peak at a frequency 565/room dimension" => "try sub in middle of that wall".


Edited by bridgman (06/17/07 12:15 AM)

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#169086 - 06/17/07 12:33 AM Re: Graph testing again, I'm confused, so is mojo [Re: bridgman]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10359
John, my thorough scientific analysis of Scott's graph would indicate to me that it results from room dimensions of 8'x 20'x 24(just kidding; in the past that's what he said the dimensions were).
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#169087 - 06/17/07 04:44 AM Re: Graph testing again, I'm confused, so is mojo [Re: jakeman]
a401classic Offline
connoisseur

Registered: 11/29/06
Posts: 1168
Loc: Alpharetta, GA
Thanks everybody. Will try to move sub to left side of unit - really glad I got the 15' XLR cable! Maybe that will flatten out some of the bumps and thumps I've been getting.

Scott
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Scott

My HT

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#169088 - 06/17/07 04:53 AM Re: Graph testing again, I'm confused, so is mojo [Re: a401classic]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10359
Naw, Scott, that XLR cable(unless you just mean that it's long enough to move things around a bit)helps reject electromagnetic interference, but you likely don't have any problem with that anyway. Those bumps and valleys come from half-wavelength distances to other drivers or quarter-wavelength to room surfaces.
_________________________
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Enjoy the music, not the equipment.



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#169089 - 06/17/07 07:31 AM Re: Graph testing again, I'm confused, so is mojo [Re: JohnK]
bridgman Offline
axiomite

Registered: 08/25/04
Posts: 5279
Loc: Bowmanville, Ontario, Canada
>>John, my thorough scientific analysis of Scott's graph would indicate to me that it results from room dimensions of 8'x 20'x 24(just kidding; in the past that's what he said the dimensions were).

Once again I bow to your wisdom. That makes sense then -- a 28 Hz peak (plus 56, 84 etc..) from the 20 foot dimension and 23, 46, 69 hz peaks from the 24 foot dimension. The 8 foot dimension would make its first appearance around 70 Hz.

Dips would be 14, 42, 70 from the 20 foot dimension, 12, 35, 58 hz from the 24 foot dimension, and 35, 100, 175 from the 8 foot dimension.

The good news is that the 80 hz dip really does look to be related to crossover not room acoustics, so give that 'ol phase switch a flip.

Nuts, I need to submit this before I can look at the graph and see if it fits

EDIT - Whew, it fits. That's actually a pretty good set of room dimensions, have to remember them.

One last question -- where is the primary seating position in the room relative to the walls, ie how far away are you from the 20 foot and 24 foot walls ? My recollection was that you were pretty squarely in the middle of the room -- which argues for moving the sub out of the corner.


Edited by bridgman (06/17/07 07:44 AM)

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