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My new PSA subs and my graphs

post #1 of 600
Thread Starter 
There seemed to be a lot of interest in my REW graphs over in the Official PSA thread (Thanks guys!). So much so that it started detracting from point of that thread. So I've moved it here.

Attached are graphs of all locations I've tried with my subs. There is no smoothing and db/hz is spaced as suggested by basshead (thanks!)

These are subs only- no mains. They are level matched via the REW SPL meter.

I have dual XV30fs- yes I will post some pictures ASAP. .

I've pretty much got to keep subs against the front wall, so these tests consisted of sliding them in and out from center. The farther out (towards the side walls) the worse the response got. The closer in, meaning both cabinets are just a few inches from each other, yielded the best results. The closer in, the better things got.

I also tried the same 'exercise' with ports facing each other. I got the same result. The closer the two cabinets were to each other in the center of the room the better the graph got.

For kicks I put each sub on it's feet, standing up in each corner of the room. Not nearly as good as centered almost touching against the front wall.

I have one possible option left and that is to move the subs to the side walls, in the front portion of the room. I'm going to try it and see what happens. It would have to be damn good for me to compromise the room with sub placement where it will stick out and be in my way.

There is a graph of all the tests I did. Then a graph of port facing port and port facing wall. The last graph is of the port facing port best locations and the port facing wall best locations. Not much difference.





post #2 of 600
I guess if I respond to your graphs in this thread I can't be accused of dragging a thread off topic. That's why I got upset as I'm tired of replying to another's post and for my thoughtfulness, be accused of off topic conversation.

Have you tried what I suggested?
post #3 of 600
Thread Starter 
Quote:
Originally Posted by BeeMan458 View Post

I guess if I respond to your graphs in this thread I can't be accused of dragging a thread off topic. That's why I got upset as I'm tired of replying to another's post and for my thoughtfulness, be accused of off topic conversation.

Have you tried what I suggested?

Now I understand what had you worked up..... I didn't get it until you just said. I didn't see it as anyone targeting you, maybe I missed it.

I want to make sure you know that the very first graph I posted in that other thread, and the other graphs were different. The first graph in the other thread had the mains, and the subs, and the subs were running hot.

In all other graphs, including the ones in this thread, the measurements are only the subs (no mains) which are level matched. I can turn the gain down on the subs, on the amp, or both...... but it's not going to change the freq. response. Just the db.

If that doesn't match what you suggested link to it or post here and I'll give it a shot. I'm headed down to measure shortly. wink.gif
post #4 of 600
Can you graph the two subs by individually to see what they are each doing. I found this helpful in my setup to take care of a dip in the same region.
post #5 of 600
Thread Starter 
Yes. I can and will.
post #6 of 600
Quote:
Originally Posted by pdxrealtor View Post

Yes. I can and will.

Could you make me a pastrami on rye while you're at it? redface.gif
post #7 of 600
Thread Starter 
Quote:
Originally Posted by steve nn View Post

Could you make me a pastrami on rye while you're at it? redface.gif

No, but my awesome wife will be happy to. wink.gif
post #8 of 600
A 40 Hz crossover might provide a better overall response if your mains can dig that deep.
post #9 of 600
Quote:
Originally Posted by pdxrealtor View Post

In all other graphs, including the ones in this thread, the measurements are only the subs (no mains) which are level matched. I can turn the gain down on the subs, on the amp, or both...... but it's not going to change the freq. response. Just the db.

You'll be surprised how much of a frequency response change you'll get. You can change the gain on a single subwoofer and have less energy going into a particular octave. Also, if lowering all subs equally, the left section left of 80Hz expectedly will sympathetically fall. I also find I can do some steering of the graph by reducing/raising the output of our center channel. I'll lower the center channel level by a dB and then take a measurement. I've found if steering the graph with the center channel and independently using each of the sub's gain setting, I can do some wonderful steering of our measured output.

(sorry for coming across so pissy.)

-
Edited by BeeMan458 - 7/3/13 at 9:44pm
post #10 of 600
Quote:
Originally Posted by pdxrealtor View Post


I've pretty much got to keep subs against the front wall,
That's probably the source of your problems. I'm sure you've got your reasons for wanting to do so, but when you fight the law(s of physics) the law(s of physics) always wins. You can put subs where they look the best, or where it's most convenient, but it's only pure luck if that happens to coincide with where they work the best.
post #11 of 600
^Agreed! Bill knows his stuff!!
post #12 of 600
Quote:
Originally Posted by steve nn View Post

Could you make me a pastrami on rye while you're at it? redface.gif

Pastrami on rye? rolleyes.gif Steve don't you mean a rye and coke on ice? biggrin.gifwink.gif
post #13 of 600
Quote:
Originally Posted by jbrown15 View Post

Pastrami on rye? rolleyes.gif Steve don't you mean a rye and coke on ice? biggrin.gifwink.gif

biggrin.gif I try, but I just can't help it! smile.gif
Quote:
That's probably the source of your problems. I'm sure you've got your reasons for wanting to do so, but when you fight the law(s of physics) the law(s of physics) always wins. You can put subs where they look the best, or where it's most convenient, but it's only pure luck if that happens to coincide with where they work the best.

Subs are kind of like cats! They go where they want to go instead of where you tell them... well if you want the best response. Now if they/subs were like your average dog, they would always want to please. That’s my animal analogy anyway. rolleyes.gif
post #14 of 600
Thread Starter 
What a night. I just did so many graphs, so many I couldn't label them all to save them in an organized fashion. I tried in the ,beginning but there were just too many.

I ended up going in the direction of the graph. Every time I end up with the subs against the front wall within inches of each other centered in the room.

I tried moving both to the side walls in front of the chairs, then one back to the front. Then all along the font wall with one leaving the other stationary then moving the other one bit by bit.

Moving the mic +/- 2 feet from 1/3rd into the room. Unplugging one speaker, then the other. Adjusting phase per Tom. It all made it worse. Nothing is even close to both subs centered in the front of the room.

It's debatable if there's enough difference between port in or port out with both centered in the front of the room.

I even lugged one to the back of my seating and ran a few graphs, moved the mic, adjusted the crossover.... .... notta..... not even a hint of hope to make me continue in any direction but back to the front.

I really moved the one sub to the back just to see what would happen. I figured sooner or later some configuration of placement would get better than the front of the room graphs. I'm the type if I see some hope I'll go for it just to get the flat graph, then move them back to my desired spot and deal with it in other ways. It just didn't happen.

Here's some pics. Sorry if I do not reply to each post tonight. I'm wiped out. These things are freaking heavy. And once again..... my wife ate alone. Steve..... you get that rye bread and if you do...eat some for me. because it was mine at one point tonight.












post #15 of 600
If you can, try placing both subs right behind your seats. Near-field placement may go a long ways toward smoothing out that response.
post #16 of 600
All that work and all those measurements but no mention of effort to gain match the subwoofer output, nor what sort of EQ'g effort was put forth or how you tweaked the settings after placement and EQ'g the output.

My personal experience, it's about best placement efforts, best EQ'g effort coupled with best tweaking efforts.

Forgive my drumbeat, did you match the subwoofer output and run the AVR's EQ program each time you moved the subwoofers?

"What is Jerusalem Worth?"

-
post #17 of 600
Quote:
Originally Posted by henrich3 View Post

A 40 Hz crossover might provide a better overall response if your mains can dig that deep.

Why?
post #18 of 600
Quote:
Originally Posted by pdxrealtor View Post

I even lugged one to the back of my seating and ran a few graphs, moved the mic, adjusted the crossover.... .... notta..... not even a hint of hope to make me continue in any direction but back to the front.

I really moved the one sub to the back just to see what would happen. I figured sooner or later some configuration of placement would get better than the front of the room graphs. I'm the type if I see some hope I'll go for it just to get the flat graph, then move them back to my desired spot and deal with it in other ways. It just didn't happen.

Hi pdxrealtor, when moving the subs around (front, side, rear) were all the graphs showing big changes for the worse or just slight difference? If the latter, its possible you may have a bad mic.
post #19 of 600
Just for fun, sub crawl one then the other?
post #20 of 600
Quote:
Originally Posted by shadyJ View Post

If you can, try placing both subs right behind your seats. Near-field placement may go a long ways toward smoothing out that response.

+1
post #21 of 600
Quote:
Originally Posted by JChin View Post

Hi pdxrealtor, when moving the subs around (front, side, rear) were all the graphs showing big changes for the worse or just slight difference? If the latter, its possible you may have a bad mic.

Good point. Could you check that by using a spl and playing test tones to see if the db shift matches what the graph shows?
post #22 of 600
Quote:
Originally Posted by basshead81 View Post

Good point. Could you check that by using a spl and playing test tones to see if the db shift matches what the graph shows?

Hi basshead81, or temporarily use the receiver setup mic.
post #23 of 600
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.
post #24 of 600
Quote:
Another is the distance from the listening position to the rear wall.

That is a thought I had from past experience but couldn't explain/understand it as you do.
post #25 of 600
Quote:
Originally Posted by steve nn View Post

That is a thought I had from past experience but couldn't explain/understand it as you do.
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.
post #26 of 600
Quote:
Originally Posted by arnyk View Post

Quote:
Originally Posted by henrich3 View Post

A 40 Hz crossover might provide a better overall response if your mains can dig that deep.

Why?

The OP's FR charts get ugly from 40 Hz on up. If he's unwilling to relocate his subs somewhere that'll provide a better response, then having the mains cover those frequencies might work out better.
post #27 of 600
Quote:
Originally Posted by pdxrealtor View Post

What a night. I just did so many graphs, so many I couldn't label them all to save them in an organized fashion. I tried in the ,beginning but there were just too many.

LOL, been there, done that. Did you happen to save the file with all the chaos? If so, please post it.
post #28 of 600
FWIW, I don't bother saving all the charts.

I save the first chart of the day. Of course the first chart of the day is after the subs have had at minimum, a half hour to warm up as I've found the graph changes as the subwoofer amplifier warms up. Once warmed up and settled in, I take a primary base reading so I can see the effectiveness of any changes.

After that I dive in with changes and readings. After a while, I can't keep each graph in my head, I erase any graphs I can't locate in my thinking and sometimes will remove all but the first graph, make a new base graph that represents the time and place I'm at in the process, and start moving forward from there.

I purposely don't take notes as I want to keep the process as simple as possible. In my opinion, this is a hobby, not a professional lab. If I haven't learned what the effort is teaching me, then I shouldn't be moving forward and once I've figured out what the measurements are showing me, then they're locked into my thinking and I don't need notes because they're locked into my thinking. Again, in my opinion, this is a hobby, not a professional lab project where complete documentation is paramount to the approval process.

At the end of the day, I save two, maybe three graphs which consists of the first or base morning graph, the last measurement graph before shutting down and any pertinent graphs in the middle that are of consequence. For forum display purposes, I will save a screen snapshot or three so as to be able to conversationally share regarding any progress. Other than that, for my needs, in my opinion, anything else is just taking up file space.

-
post #29 of 600
Quote:
Originally Posted by henrich3 View Post

The OP's FR charts get ugly from 40 Hz on up. If he's unwilling to relocate his subs somewhere that'll provide a better response, then having the mains cover those frequencies might work out better.

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!
post #30 of 600
Thread Starter 
Quote:
Originally Posted by BeeMan458 View Post

All that work and all those measurements but no mention of effort to gain match the subwoofer output, nor what sort of EQ'g effort was put forth or how you tweaked the settings after placement and EQ'g the output.

My personal experience, it's about best placement efforts, best EQ'g effort coupled with best tweaking efforts.

Forgive my drumbeat, did you match the subwoofer output and run the AVR's EQ program each time you moved the subwoofers?

"What is Jerusalem Worth?"

-

Beeman i did level match the subs, a few times but not every time, they didnt seem to need matching after the first. I also would occasionally unplug one sub and then the other. No EQ at all was used. Pioneer Mcacc was off. Mains were unplugged. I dint get into playing with mains and subs because i wanted to get an idea of what just moving the subs would do. I figure if I was to get a good reading, find the best location, then i can eq and play with mains as you suggested. I ran out of time.

I did not save all the graphs, ill have to check and see if i saved any of them. There were just so many. And none were really even close to the best ones posted here already.

And yes, the graphs moved a lot. The peeks and dips seemed to always always be in the same spot, ~40 and 50 hz, but they would be larger. And there was added instability either before the 40 hz point and/or after the 50 hz point.

Basically as seen in my graph above that shows all test locations but some got a bit wilder.

Moving both subs behind the seats wont be able to be a permanent spot but after i recover from last night i may try it just to see.

The other thing i did not try was sliding out away from the wall towards center of room. I did try mic back 1ft then 2ft , it got worse. But as suggested above, and i completely spaced it, pulling the subs off the wall is worth a shot.

If i would have thought a ton of graphs would have helped you all help me i would have saved them. But again, the best of the best is in post one.
Edited by pdxrealtor - 7/4/13 at 11:25am
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