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Discussion Starter #1
Hi everyone, I have been looking around but can't seem to figure it out.

I have a significant null from 100 to about 80hz (cross over point), yet Audyssey killed the left speaker base -25db at around that range. Same for center speaker.

I have a Denon 4311, a Rythmik f15hp and a 22x21x8 room. Carpet, 703 on the left wall, safe and sound on the back wall. ( speakers are set up 2 feet behind wall, 18 inches from left wall, and 11 feet from right wall. I can toe in or out left speaker but can't move it farther into the room, I can move the right one a bit.

The corner behind the left speaker seems hot, +12db in the base region when measuring with spl and playing some test bass music.

I will try running rew within the next couple of days, but I am sure you guys have some ideas and advise.

Thanks in advance.

Max
 

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Discussion Starter #3
If you don't like the result, turn off the room calibration software. That's what I do.
It sounds better with Audyssey on for sure, but I have the big null, which I still have with it off. That's the thing.
 

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Discussion Starter #5
Since the null is near the crossover, it may not really be a "null." It may be a cancellation caused by a mistiming between the speakers and sub around the crossover point. If so, adjusting of the subwoofer distance setting can help. I posted about this, (with measurement graphs), here: http://www.avsforum.com/forum/113-s...s-frequency-peaks-dips-room.html#post32738889

Craig
Thanks Craig. I did some rew testing today, and every speaker shows a significant null at 80 to 100 hz. I then added the sub crossed it over at 110 and got a smoother graph. Not great but a bit better. However, I am really pushing the sub to a frequency it really wasn't meant for.

Is room treatment my next step?

Thanks
 

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Thanks Craig. I did some rew testing today, and every speaker shows a significant null at 80 to 100 hz. I then added the sub crossed it over at 110 and got a smoother graph. Not great but a bit better. However, I am really pushing the sub to a frequency it really wasn't meant for.

Is room treatment my next step?

Thanks
What speakers do you have? How are they placed in relation to the walls? Was the dip there without Audyssey?

Did you try the subwoofer distance adjustment?
 

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Discussion Starter #7
What speakers do you have? How are they placed in relation to the walls? Was the dip there without Audyssey?

Did you try the subwoofer distance adjustment?
The speakers are salk song towers.
The left speaker is 2 feet from the back wall and 18 inches from the side wall. The right speaker is 2 feet from the wall and 10 feet from the right side wall. (Using a 10 x 21 out of the 21x21 of the room).

Dip with and without Audyssey, the back wall has safe n sound absorption material 12 feet on the back wal, and 3-4 feet on the side, but then I have 2 owens corning 703 2x4 feet panels for early reflection. Carpet, and large plush fabric sofa.

Did not try the distance adjustment, should I be able to remove the dip without sub support?

Thanks again
 

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The speakers are salk song towers.
The left speaker is 2 feet from the back wall and 18 inches from the side wall. The right speaker is 2 feet from the wall and 10 feet from the right side wall. (Using a 10 x 21 out of the 21x21 of the room).

Dip with and without Audyssey,
OK, so Audyssey is obviously not the culprit here. If the dip exists before Audyssey is run, Audyssey can't, and won't try to correct it. It won't make it any worse, but it can't make it any better. Audyssey won't attempt to boost a null because boosting just results in more cancellation, but not more SPL at the target frequency. Boosting also entails the use of massive amounts of amplifier power and driver excursion... even though it doesn't result in any additional SPL. Therefore, for these reasons, Audyssey won't make any attempt to correct nulls.

What you're describing is more likely a cancellation caused by Speaker/Boundary Interference Response, (SBIR.) Your mid/woofer drivers are about 2-3 feet above the floor. The speakers are about 2 feet from the back wall. Bass radiates omnidirectionally, so you're going to get a floor bounce and a rear-wall bounce. If the the two boundary induced reflections gang up on each other, you'll get a big dip at the frequency with a quarter-wavelength that is 2-3 feet. 100 Hz has a quarter wavelength of 2.85 ft.

So theoretically, your problem is likely a set of reflections off the floor and back wall combining out of phase with the original wave in a destructive fashion. To test this, try temporarily moving your speakers further out into the room and away from the back wall. See if that impacts the nulls. If it does, you've found the problem. The long term soultion will be to find different in-room speaker positions that still provide good imaging and soundstage, but without the LF nulls.

BTW, your Rythmic sub is spec'd to 90 Hz on the Line In inputs, but it's spec'd to 200 Hz if you use the LFE inputs. If you are raising the crossover above 90 Hz, you should use the LFE inputs.

the back wall has safe n sound absorption material 12 feet on the back wal, and 3-4 feet on the side, but then I have 2 owens corning 703 2x4 feet panels for early reflection. Carpet, and large plush fabric sofa.
None of that will have any impact in the 80-100 Hz range. You need much thicker absorption to impact 80-100 Hz.

Did not try the distance adjustment, should I be able to remove the dip without sub support?
If the problem is SBIR, then the subwoofer distance tweak won't help. If it's not SBIR, and it is instead a mistiming of the speakers and subs at the crossover, then the subwoofer distance tweak will help. At this point, I'm betting on SBIR.

Craig
 

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Discussion Starter #9
OK, so Audyssey is obviously not the culprit here. If the dip exists before Audyssey is run, Audyssey can't, and won't try to correct it. It won't make it any worse, but it can't make it any better. Audyssey won't attempt to boost a null because boosting just results in more cancellation, but not more SPL at the target frequency. Boosting also entails the use of massive amounts of amplifier power and driver excursion... even though it doesn't result in any additional SPL. Therefore, for these reasons, Audyssey won't make any attempt to correct nulls.

What you're describing is more likely a cancellation caused by Speaker/Boundary Interference Response, (SBIR.) Your mid/woofer drivers are about 2-3 feet above the floor. The speakers are about 2 feet from the back wall. Bass radiates omnidirectionally, so you're going to get a floor bounce and a rear-wall bounce. If the the two boundary induced reflections gang up on each other, you'll get a big dip at the frequency with a quarter-wavelength that is 2-3 feet. 100 Hz has a quarter wavelength of 2.85 ft.

So theoretically, your problem is likely a set of reflections off the floor and back wall combining out of phase with the original wave in a destructive fashion. To test this, try temporarily moving your speakers further out into the room and away from the back wall. See if that impacts the nulls. If it does, you've found the problem. The long term soultion will be to find different in-room speaker positions that still provide good imaging and soundstage, but without the LF nulls.

BTW, your Rythmic sub is spec'd to 90 Hz on the Line In inputs, but it's spec'd to 200 Hz if you use the LFE inputs. If you are raising the crossover above 90 Hz, you should use the LFE inputs.


None of that will have any impact in the 80-100 Hz range. You need much thicker absorption to impact 80-100 Hz.


If the problem is SBIR, then the subwoofer distance tweak won't help. If it's not SBIR, and it is instead a mistiming of the speakers and subs at the crossover, then the subwoofer distance tweak will help. At this point, I'm betting on SBIR.

Craig

Thanks Craig. Will bass traps help here? I also have some big dips I. Bass region and dips in the 150s.

I tried increasing the distance on the sub, and it had a positive impact, very clear, however I wouldn't say that it removed the null or significant dips. Will try moving speakers in significantly and seeing what happens.

Thanks again for the help.
 

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Thanks Craig. Will bass traps help here? I also have some big dips I. Bass region and dips in the 150s.

I tried increasing the distance on the sub, and it had a positive impact, very clear, however I wouldn't say that it removed the null or significant dips. Will try moving speakers in significantly and seeing what happens.

Thanks again for the help.
Bass traps won't do much below 100 Hz unless they're really thick, (thick as in "feet" not "inches.") They can help in the 150 Hz range.

Did you try moving the speakers away from the wall to see if the SBIR decreased?

Craig
 

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Discussion Starter #11
Bass traps won't do much below 100 Hz unless they're really thick, (thick as in "feet" not "inches.") They can help in the 150 Hz range.

Did you try moving the speakers away from the wall to see if the SBIR decreased?

Craig
I did, and nothing, null still there. I brought them out more than a foot and it was actually a bit worse. Maybe closer to the wall a bit better, but I gave up for today. What else can be done?
 

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Thanks Craig. I did some rew testing today, and every speaker shows a significant null at 80 to 100 hz. I then added the sub crossed it over at 110 and got a smoother graph. Not great but a bit better. However, I am really pushing the sub to a frequency it really wasn't meant for.

Is room treatment my next step?

Thanks
IMO room treatment is not going to help you at those frequencies.
 

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I did, and nothing, null still there. I brought them out more than a foot and it was actually a bit worse. Maybe closer to the wall a bit better, but I gave up for today. What else can be done?
I was taught the automated eq's in AVR's are more or less an automated toy, while I was at the THX Ranch. Sometimes they play right, sometimes they play wrong. In your case it appears to be doing wrong by you.

You may have to live with a trade off.
 

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I did, and nothing, null still there. I brought them out more than a foot and it was actually a bit worse. Maybe closer to the wall a bit better, but I gave up for today. What else can be done?
Do a nearfield measurement: Move the speaker out to the middle of the room, place the mic 6" from one of the woofers and take a measurement. If the "null" is still here, it's not a null; it's the speaker.

Craig
 

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I was taught the automated eq's in AVR's are more or less an automated toy, while I was at the THX Ranch. Sometimes they play right, sometimes they play wrong. In your case it appears to be doing wrong by you.

You may have to live with a trade off.
The problem exists with and WITHOUT Audyssey. Audyssey is not the problem.
 

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Discussion Starter #17
Do a nearfield measurement: Move the speaker out to the middle of the room, place the mic 6" from one of the woofers and take a measurement. If the "null" is still here, it's not a null; it's the speaker.

Craig
Being so close to the woofer, does it matter if I move the speaker out to the middle of the room?

The problem can be detected with all 3 front speakers to slightly different degrees.

Slightly off subject, What would work to improve response in the 100-200hz area?
 

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Being so close to the woofer, does it matter if I move the speaker out to the middle of the room?
The question is whether something about the room and placement is causing the dip, or if the speaker itself is rolling off higher than the specified roll-off. Moving the speaker as far away from all room boundaries is the best way to determine if the problem is the speaker or the room. Even better would be to take the speaker outside, but that's probably impractical.

The problem can be detected with all 3 front speakers to slightly different degrees.
Possibly points to the speakers being the problem. Doing a mid-room, nearfield measurement will tell the tale.

Slightly off subject, What would work to improve response in the 100-200hz area?
Speaker position, listening position, bass traps, Audyssey, in that order.

Craig
 

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Great advice so far, but all based on words... can you post some data? If so, please continue to add descriptions, test conditions, etc., but let us see with our eyes what you're now only describing.

HAve fun,
Frank
 

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Discussion Starter #20
Great advice so far, but all based on words... can you post some data? If so, please continue to add descriptions, test conditions, etc., but let us see with our eyes what you're now only describing.

HAve fun,
Frank
Hi Frank, what info or chart would be most beneficial for me to share? I know there are correct and incorrect ways to capture and share.
 
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