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My new PSA subs and my graphs - Page 2

post #31 of 600
Thread Starter 
Quote:
Originally Posted by Bill Fitzmaurice View Post

The distance from the speakers to all boundaries, and that from the listening position to all boundaries, all contribute to the final result, but it's the front wall with respect to the speakers and the rear wall with respect to the LP that usually have the greatest effect, as they tend to be at a right angle to the speakers and LP. Side walls get more of a 'glancing blow', so their effect is spread over a wider bandwidth with less depth.

And the next move will be pulling them out from the front wall 6" at a time. Ill save the graphs.
Quote:
Originally Posted by Bill Fitzmaurice View Post

Going back to the original plots, all have a serious dip at 50Hz. There are two causes for a serious dip. One is the speaker placement, the other is the mic placement. If the speakers are 1/4 wavelength from the wall behind them the reflected wave will meet the original wave at 1/2 wavelength, 180 degrees out of phase, resulting in Allison Effect dip. As 1/4 wavelength at 50Hz is 5.6 feet that's one possible explanation. Another is the distance from the listening position to the rear wall. If that's 1/4 wavelength the reflection off the rear wall will meet the original wave at 1/2 wavelength, causing a cancellation dip. If moving the mic closer or further from the rear wall has no effect then the source of the dip isn't the rear wall, it's the front wall.

I will move the mic from 1/3rd (5ft) back toward wall and run graphs. Then speakers in from back wall 6" at a time and run graphs.

I will save all graphs and provide a rew file via drop box. To keep it simple ill number each location with blue tape and record the same number in rew, so at least ill have a reference if someone asks about a specific measure.
post #32 of 600
Thread Starter 
Here's a couple graphs I did save. One is mic movement, one shows one sub in front against wall and one behind seats and one is the all measurements graph from pg. 1 with a couple added measures to it.

I also have a file with measures that experiment with phase adjust, but for some reason when I saved the file it saved as a .REC file. It shows up with a REW EQ icon. Any idea how to get it to the .Mdat file format? I have no idea why that happened, but the phase control was an interesting graph.

Ok- I"m going to run about three graphs then I gotta get going.




post #33 of 600
Quote:
Originally Posted by jlpowell84 View Post

The problem with that is the reason you have subs is to play the bass frequencies. Why send 40 and up to the mains when you have very capable subwoofers? Instead this is the fun and adventure of measuring, adding room treatments and finding the right sweet spot for the subs. smile.gif I would certainly want the kick drum in my music to play through my subs!

I agree with you. If the OP can't find a better location for his subs that he's willing to live with however, my suggestion was a "Plan B" that might provide a better overall FR than he's currently getting. His mains have 15" mid/woofs so they should be capable of reaching down to 40 Hz. Since it just takes a minute to change a crossover in an AVR (no heavy lifting involved), it's an easy thing to try. If it's a bad idea, that too will be quickly revealed.
post #34 of 600
Thread Starter 
2 graphs- One is a slide in 1ft increments along the front wall, moving from far out to the center

The second has each cabinet 6 ft from side wall (about 1ft space between cabinets) and moves them off the front wall towards the LP in 1ft increments.




post #35 of 600
Thread Starter 
Happy 4th everyone!
post #36 of 600
5' off the back wall is the best you've shown for 40 Hz on down. If you hook up the mains, set the crossover to 40 Hz and remeasure, I'd guess the overall response would look pretty good. (Try measuring with the sub levels balanced with the mains (not hot), just for fun...)
post #37 of 600
Quote:
Originally Posted by pdxrealtor View Post

Beeman i did level match the subs, a few times but not every time, they didnt seem to need matching after the first.

First things first....based on you above, everything you're doing is designed to assure you of fail.

You need to gain match the sub's output so each sub is putting out equal energy. And the purpose of EQ'g your output is to help you deal with a room's acoustics. And the purpose of tweaking is to balance the sub's output with the EQ'g effort. Each one builds on the other.

If not willing to do this, you're shooting your effort in the foot and right now it reads as if you're throwing a bunch of half cooked spaghetti on the wall, hoping it's cooked.
post #38 of 600
Thread Starter 
Quote:
Originally Posted by henrich3 View Post

5' off the back wall is the best you've shown for 40 Hz on down. If you hook up the mains, set the crossover to 40 Hz and remeasure, I'd guess the overall response would look pretty good. (Try measuring with the sub levels balanced with the mains (not hot), just for fun...)

I hate to cut at 40hz. I have a Rane PEQ on the way and I'll toy with that before I cut at 40 hz, or for that matter leave the subs 5 ft out from the front wall. It simply puts them within inches of my chairs when reclined.
post #39 of 600
Thread Starter 
Quote:
Originally Posted by BeeMan458 View Post

First things first....based on you above, everything you're doing is designed to assure you of fail.

You need to gain match the sub's output so each sub is putting out equal energy. And the purpose of EQ'g your output is to help you deal with a room's acoustics. And the purpose of tweaking is to balance the sub's output with the EQ'g effort. Each one builds on the other.

If not willing to do this, you're shooting your effort in the foot and right now it reads as if you're throwing a bunch of half cooked spaghetti on the wall, hoping it's cooked.

I'm sorry, when say level matched I mean gain matched. I didn't know there was a difference.?.... Both my gain knobs are about 1:30-2:00 and, yes, I did use the REW SPL meter to match them one at a time. wink.gif

My EQ (MCACC) does absolutely nothing to subs below 63hz, so there is no need to use it at this point.

Now, I do have a Rane PE17 5 band PEQ on the way as was suggested by Tom. So then, yes, I will EQ the subs.
post #40 of 600
Quote:
Originally Posted by pdxrealtor View Post

I'm sorry, when say level matched I mean gain matched. I didn't know there was a difference.?.... Both my gain knobs are about 1:30-2:00 and, yes, I did use the REW SPL meter to match them one at a time. wink.gif

My EQ (MCACC) does absolutely nothing to subs below 63hz, so there is no need to use it at this point.

Have you verified the output or are you hoping they're still outputting the same amount? When you set the gain volume, what distance is the sound meter at? Is it a generalized, this is good enough distance or is the measurement taken at a consistent, measured distance.

Dumb question on my part, when you set the gain, did you do so with the other subwoofer turned off? Have you tried what I suggested regarding individually changing the gain setting to steer the graph?
post #41 of 600
pdx, Try adjusting the phase on one of the subs and see how that affects your response. It should have a significant impact...for better or worse, but it will change it. You can tweak with the other subs phase as well.
post #42 of 600
...+1

Gain, phase and LPF, will all steer a subwoofer's graph.
post #43 of 600
Thread Starter 
Quote:
Originally Posted by dominguez1 View Post

pdx, Try adjusting the phase on one of the subs and see how that affects your response. It should have a significant impact...for better or worse, but it will change it. You can tweak with the other subs phase as well.

I said above that i adjusted phase on one set of tests, long post is probably why you missed it.

I did adjust phase on one, 1/4 turn at a time. I have the graph but for some reason REW saved it as a .REC file and not a .mdat file. If someone can tell me how to get the file converted over to .mdat i can post the graph.



Quote:
Originally Posted by BeeMan458 View Post

Have you verified the output or are you hoping they're still outputting the same amount? When you set the gain volume, what distance is the sound meter at? Is it a generalized, this is good enough distance or is the measurement taken at a consistent, measured distance.

Dumb question on my part, when you set the gain, did you do so with the other subwoofer turned off? Have you tried what I suggested regarding individually changing the gain setting to steer the graph?

The meter is my mic combined with REW SPL meter. Its precisely located at 5ft from the back wall, exactly 1/3rd into the room.

All level or gain (whatever you call it) was taken with the mic in the same spot, the main LP, as noted above. And yes, again, each sub was matched separately. Meaning i unplugged one sub, set a level on the other sub via the sub amp gain knob, then unplug that sub do the exact same with the other. Then plug them both in.

I did not change the gain setting to steer the graph.
post #44 of 600

Sorry, I did miss it.

 

I know you said you had problems saving the file, but how did it look? Any better?

post #45 of 600
Thread Starter 
No, it looked worse. It sent the speakers opposite. So there would be a peak and a dip at, lets say, 50hz.

Theres gotta be a way to fix that file. I guess i could just remeasure. Its only a turn of the knob. The subs were at the front of the room close to center where ive so far gotten the best measurements.
post #46 of 600
Quote:
Originally Posted by pdxrealtor View Post

The meter is my mic combined with REW SPL meter.

REW is expecting the owner to calibrate REW with a separate sound meter.

With a separate sound meter, set the AVR's main menu control for the subwoofer to +/-0dB and with pink noise running through one of the subs, the other turned off, using the gain knob control and a sound meter positioned one meter from the face of the subwoofer driver (others recommend one inch), set the subwoofer gain so the sound meter reads 70-72dB. Turn the one subwoofer off, turn the other subwoofer on and do the same for the other subwoofer. The combined output at the main listening position should now be about 75dB.

Quote:
did not change the gain setting to steer the graph.

Go ahead, give it a try. After taking a base (control) measurement, walk over to one of the subwoofer and turn the gain up past the base setting, take a measurement. Then turn the single subwoofer's gain down below the base setting and take a measurement. Then set the gain to the original base position, take a fourth measurement. Compare these four measurements.

With the subwoofer's gain knob at the control setting, do the same with your center channel setting using the AVR's main menu level settings.
post #47 of 600
Thread Starter 
Edit- i did not do the routine above. It does not need to be done like that to find optimal placement. Simply matching them with a mic and rew spl meter is just fine.

For measuring freq. response it does not matter what the actual db is. You are only after the response graph.


I will play with gain.
Edited by pdxrealtor - 7/4/13 at 4:17pm
post #48 of 600
Quote:
Originally Posted by pdxrealtor View Post

I said above that i adjusted phase on one set of tests, long post is probably why you missed it.

I did adjust phase on one, 1/4 turn at a time. I have the graph but for some reason REW saved it as a .REC file and not a .mdat file. If someone can tell me how to get the file converted over to .mdat i can post the graph.
The meter is my mic combined with REW SPL meter. Its precisely located at 5ft from the back wall, exactly 1/3rd into the room.
When placed close together, dual subs "couple" and act like a single sub... with more output. Therefore, adjusting the phase on one of two co-located subs will only result in cancellation, not augmentation. If the subs are right next to each other, you want them perfectly in-phase and gain-matched, (both subs set to the same phase/polarity settings and both amps set to the same gain setting.)
Quote:
Originally Posted by pdxrealtor View Post

All level or gain (whatever you call it) was taken with the mic in the same spot, the main LP, as noted above. And yes, again, each sub was matched separately. Meaning i unplugged one sub, set a level on the other sub via the sub amp gain knob, then unplug that sub do the exact same with the other. Then plug them both in.
That is "level-matching." You are adjusting the subwoofer gains to match the levels at the listening/measuring position. Gain-matching would entail setting the gains to "match" irrespective of what they measure at the LP. Nonetheless, for you, this is likely pedantic nomenclature if your subs are next to each other in the front of the room. Level-matching and gain-matching will likely yield very similar results.

OTOH, if you decide to separate the subs and move one to the back of the room, then gain-matching vs. level-matching becomes a more important discussion, as does setting phase/polarity.
Quote:
Originally Posted by pdxrealtor View Post

I did not change the gain setting to steer the graph.
I would not do this with identical subs either. You end up with one sub set higher than the other and you limit system headroom. You bought 2 identical subs so you could use the full potential of both subs. You can't do that if one is set higher than the other. More importantly, if both subs exhibit very similar response at the listening/measuring position, changing the gain of one of the subs is not likely to be beneficial to the overall frequency response.

Craig
post #49 of 600
Quote:
Originally Posted by BeeMan458 View Post

REW is expecting the owner to calibrate REW with a separate sound meter.

With a separate sound meter, set the AVR's main menu control for the subwoofer to +/-0dB and with pink noise running through one of the subs, the other turned off, using the gain knob control and a sound meter positioned one meter from the face of the subwoofer driver (others recommend one inch), set the subwoofer gain so the sound meter reads 70-72dB. Turn the one subwoofer off, turn the other subwoofer on and do the same for the other subwoofer. The combined output at the main listening position should now be about 75dB.
Nope. The only thing that will be "about 75 dB" will be the theoretically combined levels of the 1 meter measurements. The combined level at the LP could be *anything!* That would be totally dependent on the relative distances to the LP, and the room augmentation/cancellation.
Quote:
Originally Posted by BeeMan458 View Post

Go ahead, give it a try. After taking a base (control) measurement, walk over to one of the subwoofer and turn the gain up past the base setting, take a measurement. Then turn the single subwoofer's gain down below the base setting and take a measurement. Then set the gain to the original base position, take a fourth measurement. Compare these four measurements.
And then what???? You end up with a system where 2 identical subs are set with dissimilar gain settings? They are no longer "identical" subs.
Quote:
Originally Posted by BeeMan458 View Post

With the subwoofer's gain knob at the control setting, do the same with your center channel setting using the AVR's main menu level settings.
He is trying to optimize the subwoofer locations. He's trying to do this without any influence from the speakers. This is the *correct* way to proceed. Once the subs are optimized for position and FR at the LP, then you add the speakers... and you use the subwoofer Distance setting in the receiver to optimize the blend of the speakers and subs.

Craig
post #50 of 600
Thread Starter 
Quote:
Originally Posted by craig john View Post

When placed close together, dual subs "couple" and act like a single sub... with more output. Therefore, adjusting the phase on one of two co-located subs will only result in cancellation, not augmentation. If the subs are right next to each other, you want them perfectly in-phase and gain-matched, (both subs set to the same phase/polarity settings and both amps set to the same gain setting.)

That explains exactly what my graph showed when i added phase on the one cabinet.

That is "level-matching." You are adjusting the subwoofer gains to match the levels at the listening/measuring position. Gain-matching would entail setting the gains to "match" irrespective of what they measure at the LP. Nonetheless, for you, this is likely pedantic nomenclature if your subs are next to each other in the front of the room. Level-matching and gain-matching will likely yield very similar results.

OTOH, if you decide to separate the subs and move one to the back of the room, then gain-matching vs. level-matching becomes a more important discussion, as does setting phase/polarity.

When gain matching is the process simply aligning the gain knob on each sub amp exactly the same?


I would not do this with identical subs either. You end up with one sub set higher than the other and you limit system headroom. You bought 2 identical subs so you could use the full potential of both subs. You can't do that if one is set higher than the other. More importantly, if both subs exhibit very similar response at the listening/measuring position, changing the gain of one of the subs is not likely to be beneficial to the overall frequency response.

I figured it would be a quick easy way to experiment, but i had the same kind of thought. It would be setting the base of a system up with out of whack subs. And you'd lose head room or db, one or the other.

Craig

This is all fun to experiment if only to learn where the sweet spot is, but in the end theres a 95% chance my subs will be against, or close to, the front wall and i will hopefully be able to balance the two or three issues with the Rane PE-
17.

I might get ambitious and move both to behind the LP but it would be only for experimentation as its not really practical for them to be placed there. The other option might be behind e LP against the back wall, not sure if both would fit there or not.

Those damn things are heeaavvvvy!
post #51 of 600
Two XV30f's? Headroom is not part of that equation as more than likely, looking at posted images of your system, your ears will blow before you run out of headroom as you're looking at a much more that a +120dB subwoofer system and if you're driving at that level, then subwoofers is not your concern.

Just saying as many like to float hypotheticals as if they're real world concerns.

(yup. some nutjob told me to set the gain so one subwoofer would hit only 115dB and the other so it would hit 120dB and with room gain and co-location, a combined total of +125dB - 128dB. Man, 5dB worth of headroom lost. What was he thinking? Anybody who thinks like that is certifiable.)

.....rolleyes.gif

And what's with not having a separate sound meter? You have thousands in your system and you're trying to get by without a sound meter? Please buy a sound meter. That would be kind of you. And please make the changes I suggested as it costs you nothing, can't hurt your system and with the twist of a knob the bass heavy measurements you're working so hard to get rid of can easily be restored. If one continues asking for advice and then chooses to ignore same said advice, one is having a one-way conversation. And if you want to ignore my suggestions, because you don't think they apply to your situation, that's fine but please stop acting as if you're seriously entertaining what I have to share.

Another suggestion, based on what I've read that you've posted, sell your current AVR and buy an AVR with an EQ program like Audyssey installed as yes, doing this will make a huge difference in the outcome of your measurements. And no, I'm not knocking your choice in AVR's as the Pioneer SC 1522k is a fine, very capable AVR but part of the problem seems to be it's anemic EQ'g ability and not having a separate sound meter.

-
Edited by BeeMan458 - 7/5/13 at 6:17am
post #52 of 600
Thread Starter 
Lol... Oh my.
post #53 of 600
Just curious if you tried facing the drivers towards the wall instesd of facing out?
post #54 of 600
Thread Starter 
No, i have not. Since theyre currently five ft out in my room I'll flip them over once, to face the wall, and run a few tests.

I thought about facing the drivers towards the wall in the corner too.
post #55 of 600
Quote:
Originally Posted by pdxrealtor View Post


This is all fun to experiment if only to learn where the sweet spot is, but in the end theres a 95% chance my subs will be against, or close to, the front wall and i will hopefully be able to balance the two or three issues with the Rane PE-
17.

I might get ambitious and move both to behind the LP but it would be only for experimentation as its not really practical for them to be placed there. The other option might be behind e LP against the back wall, not sure if both would fit there or not.

Those damn things are heeaavvvvy!

 

Given you have limited placement options, phase and EQ will be your best tools. Try playing with the phase again, but by adjusting the phase on both subs to see if that helps. There should be a combination in there that will get you a flatter response, or at least minimize the nulls/dips in your FR. If you can accomplish that, your EQ can tame the peaks.
post #56 of 600
Quote:
Originally Posted by pdxrealtor View Post

Lol... Oh my.

Or, you can schlep a pair of uber heavy subwoofers all over the room.

...

One can also entertain an Anti-Mode, 8033S II or a miniDSP as a solution.

Please, am I wasting my time here? wink.gif

I don't mind sharing, I do mind being played.

-
Edited by BeeMan458 - 7/5/13 at 8:03am
post #57 of 600
Quote:
The meter is my mic combined with REW SPL meter. Its precisely located at 5ft from the back wall, exactly 1/3rd into the room.
Quote:
theyre currently five ft out in my room
With the subs five feet from the front wall and the mic five feet from the back wall the only surprise is that the 50Hz dip isn't deeper.
post #58 of 600
Quote:
Originally Posted by pdxrealtor View Post

No, it looked worse. It sent the speakers opposite. So there would be a peak and a dip at, lets say, 50hz. .

If you are measuring the speakers individually I think this is what you are looking for. The spike on one takes care of the dip on the other.
post #59 of 600
Quote:
Originally Posted by basshead81 View Post

Just curious if you tried facing the drivers towards the wall instesd of facing out?

+1 Yes give it a try.
post #60 of 600
Thread Starter 
Quote:
Originally Posted by Bill Fitzmaurice View Post


With the subs five feet from the front wall and the mic five feet from the back wall the only surprise is that the 50Hz dip isn't deeper.

Oddly enough thats the flattest < 50 hz response I've gotten
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