Subwoofer Eq Suggestions

[OttoMatic]

Hey there,

How many bass traps did you add? I'm surprised to see that much of a difference -- there appear to be some deltas in the 10 dB range. I think something's weird.

Can you do, say, three "before" sweeps and then three "after" sweeps? And try limiting your X axis from 15 to 200 Hz or so; it will help us get a better idea of what the bass traps are doing in the bass region (it'll give us better resolution).

Also, "before" and "after" waterfall plots can be useful, and REW can do that.

 

[avaserfi]

Hey there,

How many bass traps did you add? I'm surprised to see that much of a difference -- there appear to be some deltas in the 10 dB range. I think something's weird.

Can you do, say, three "before" sweeps and then three "after" sweeps? And try limiting your X axis from 15 to 200 Hz or so; it will help us get a better idea of what the bass traps are doing in the bass region (it'll give us better resolution).

Also, "before" and "after" waterfall plots can be useful, and REW can do that.

I'll be able to do that just not tonight. I added two 5.5inch thick traps (4 inches of OC705) in the two back corners of my room along with some 3.5 inch thick (2 inches OC705) panels behind my speakers and tv (1 behind each speaker and 2 smaller ones behind the tv) as well as above (same set up above and below the tv) the TV and 2 smaller ones on the back wall.

The thicker bass traps are 4 ft x 1ft
The medium ones are 2 ft x 1 ft
Small ones are 1 ft x 1 ft

edit: Here is the scaled down version of the previous graph 15-200hz. I looked through my older results and found that there is no point in me posting multiple scans as I did them and they all turned out the basically same. It seems as if I have changed my room modes significantly by adding these bass traps. I probably need to play with placement more. Probably when I have more time.

 

[OttoMatic]

edit: Here is the scaled down version of the previous graph 15-200hz. I looked through my older results and found that there is no point in me posting multiple scans as I did them and they all turned out the basically same. It seems as if I have changed my room modes significantly by adding these bass traps. I probably need to play with placement more. Probably when I have more time.

Yeah, those are amazing changes. I'm not an expert with bass traps, but the results I've seen in the past haven't been so drastic (a 10 dB change is very significant). Like you said, you may have changed your room's modes, so I guess it's possible. Keep playing with it! I'd love to seem more of your results -- perhaps taking one out at a time? I know how it is though with taking the time to do them all, fitting everything else in, etc.

Have fun!

 

[avaserfi]

Yeah, those are amazing changes. I'm not an expert with bass traps, but the results I've seen in the past haven't been so drastic (a 10 dB change is very significant). Like you said, you may have changed your room's modes, so I guess it's possible. Keep playing with it! I'd love to seem more of your results -- perhaps taking one out at a time? I know how it is though with taking the time to do them all, fitting everything else in, etc.

Have fun!

I am planning on writing an indepth article on what I did and the results but I still have some to learn before I do this. I did realize in this post I accidentally posted the wrong graph. I am nearly 100 percent sure that graph is without any of the bass traps and just the small and medium absorbers up. That graph actually looks much better to me as it was only the sub and my towers should pick up the slack at that deep dip at 87 or so Hz. I will play with the set up more. Am I right to think the graph with no basstraps is the better one or am I missing something completely?

Thanks for all the help guys. I will try to post more indepth graphs as soon as I can. I will probably have more time on Sunday.

 

[OttoMatic]

Thanks for all the help guys. I will try to post more indepth graphs as soon as I can. I will probably have more time on Sunday.

In your previous post, you said black is "before" and purple "after." If that's the case, then I like the "after" one better -- you're getting way more output (too good to be true!) at the low end, and your peaks-to-valley deltas are smaller.

Do you have a BFD or SMS-1? (sorry, being lazy, I should go back and read the whole thread...).

 

[avaserfi]

In your previous post, you said black is "before" and purple "after." If that's the case, then I like the "after" one better -- you're getting way more output (too good to be true!) at the low end, and your peaks-to-valley deltas are smaller.

Do you have a BFD or SMS-1? (sorry, being lazy, I should go back and read the whole thread...).

Okay re-editing this post because I need sleep but am volunteering right now so it will be a few hours before rest:

The Black is before the treatments and the purple is after, yes. The purple looks better to you? How so I thought atleast on low end the black looked better as there was more output, higher end there is the opposite though. Also what about this post here, would you say that is better? It is with the treatments minus the acoustics.

I do not have a parametric eq yet, but a SMS-1 is on the way.

 

[avaserfi]

So I have figured it out the original graph has Black as before and purple as after. To add to the confusion the close up is the opposite, that caused the confusion. So it looks like the traps are hurting my response. I currently have them straddling the corners behind the listener as I was told to do. Anyone have any ideas why this could be happening? It seems as if the bass traps are doing quiet a bit of damage to my frequency response especially compaired to the graph without them but including the other treatments.

 

[OttoMatic]

So I have figured it out the original graph has Black as before and purple as after. To add to the confusion the close up is the opposite, that caused the confusion.

OK. Yeah, in the closeup post, the purple one is better. In the plot that extends to 20kHz, the black one is better; like you said, they're reversed. So, yeah, I think we're in agreement about which one is better -- the "before".

this post here, would you say that is better? It is with the treatments minus the acoustics.

That plot is generally flatter, but has that big suckout around 88 Hz, as I'm sure you've noticed. And the dip around 65 Hz. What's your crossover frequency? Mains are on in these plots, right (the 20kHz one for sure). It's hard to compare low-end extension with the others, since it's on not in the same picture. I think the overall shape would be easier to fix via parametric EQ than either of the others.

I still think something's up with the major changes in frequency response. I see that Bryan Pape has posted in this thread, so I'll be interested to see what he thinks. Maybe I'm way off!

I think you should start over with your measurements. Is it possible that the microphone was moved even a little bit? Were the plots taken on the same day? Just wondering... Yeah, when you have some time, take a baseline measurement, add one trap, take another measurement, add another trap, etc. Put 'em all on the same set of axes and let's see what comes out.

Oh, another thing, measure only the sub; turn the mains off, one way or another. Assuming you've crossed over your mains and your sub. Get the sub response right first, and then worry about integrating the mains. Do you have a phase control on your sub or sub amp? Have you played with placement? What sub are you using? (again, I should go back and read the whole thread, but I'm being lazy)

I do not have a parametric eq yet, but a SMS-1 is on the way.

That will definitely help. I've no experience with the SMS-1 personally, but I understand that it is effective. I think you'll have a good opportunity to get that sub frequency response flatter.

 

[avaserfi]

My mains are crossed over at 50Hz right now and you are right. I am going to pull everything down again and start over tomorrow. Ill play with the basstraps the most and see what happens.

I am using a Jamo sub 650 currently which allows for phase and boundry gain adjustment. I have played with both placement and these two settings.

With REW you can set it to just do a sub measurement and that is what I will do.

Lastly, I know the mic wasn't moved at all and the measurements were taken within 10 minutes of eachother so it shouldn't be any external variable there although it still is possible.

 

[OttoMatic]

Sounds like a good plan. I'll be interested to see the results. Good luck!

 

[avaserfi]

So, I am having some REW problems and I am just not sure what to do. I never noticed this before, but I also don't think it was there to notice. Whenever I try to run a sweep my woofer plays but so do my fronts. I made sure my speakers weren't set on large so that wasn't the problem. I changed their crossover to 250 and that still didn't help. I am really at a loss here. Is this normal? I have it set to do an anaylsis on the subwoofer...

Anyone have any ideas?

edit: I might just be paranoid as I don't want to make any mistakes now. Is the fronts and sub playing during the sweep normal?

 

[OttoMatic]

So, I am having some REW problems and I am just not sure what to do. I never noticed this before, but I also don't think it was there to notice. Whenever I try to run a sweep my woofer plays but so do my fronts. I made sure my speakers weren't set on large so that wasn't the problem. I changed their crossover to 250 and that still didn't help. I am really at a loss here. Is this normal? I have it set to do an anaylsis on the subwoofer...

Anyone have any ideas?

edit: I might just be paranoid as I don't want to make any mistakes now. Is the fronts and sub playing during the sweep normal?

Depending on the sweep range, the mains might play (if, for example, you sweep > 250 Hz). Do you know the limits of the sweep?

Also, most receivers/pre-pros employ a second-order filter on the mains, so there will still be plenty of signal getting through below the mains crossover point.

Usually, I'd recommend turning off your mains entirely -- either by turning off their amp (if you're using an external amp) or simply by disconnecting them from the receiver during the test. That way, you can measure one thing at a time, get the sub response straight, and worry about sub/main integration later.

 

[Buckle-meister]

Here are the current results...

Avaserfi, given that the specification for your sub states that it goes cleanly down to 24Hz, how are you maintaining SPL as low as 14.8Hz as shown on the graph above? Are you able to see your results in a so-called 'waterfall' form?

 

[avaserfi]

Avaserfi, given that the specification for your sub states that it goes cleanly down to 24Hz, how are you maintaining SPL as low as 14.8Hz as shown on the graph above? Are you able to see your results in a so-called 'waterfall' form?

I have no idea...I just took another graph with all my treatments up and after recalibrating my soundcard just in case I did it wrong for REW. I followed all the steps from the manual. I am just lost, I think I must be doing something wrong with the program to be honest... Here is the waterfall and graph I just took with all the treatments and pics of my treatments.

Graph:

Waterfall:

Treatments:

Note there are two traps straddling the corners, one in the picture and the other is in the opposing corner against the back wall.

 

[bpape]

There are multiple things at play here including non-symmetry and less than optimal seating, speaker, and sub position. It is very very likely that one or more of these is causing the null in which case you're not going to get rid of it until you can address the cause of the issue. I can put a bandaid on my toe but if the car is still sitting on it - it's still going to hurt

Now, it is possible that putting up the treatments have rid you of one mode that unfortunately may have been offsetting another and now the other is showing it's head.

My strong suggestion to you is pull it all down. Play with speaker, seat, sub position (use 80hz for the xover please please please). Does it strike you odd that you're crossing over at 50Hz and that's where your null is? Think maybe we have a phase issue? Not being smart - just trying to get you thinking... There are tons of variables. Would you be surprised if changing the xover point rid you of the null? I wouldn't. But, it may not which at least eliminates one variable.

Anyway, I digress. Once you get the seating position, speaker positions, and sub positions the best you can in terms of frequency response, THEN start SLOWLY putting treatments back up. Start with the corner ones, then remeasure. Make sure to look at waterfalls along the way. When you're playing with positioning, look at all the variables and measure, measure, measure. Move the speakers 6" farther from the wall and see what that does. Shift the sub away from the front wall. Try moving the sub UP on something (yes - we have to think in 3 dimensions when we can.) etc.

Yes - I'm a sicko - this is the fun part...

Bryan

 

[avaserfi]

Thanks for the tips Bryan. Today, before the measurements that are posted were taken I changed all my crossovers to 80 except my center which is at 100 (where its rated down to). So the null is unrelated to cross-over setting. This Sunday I will pull down all the panels and start to remeasure all my settings and fiddle with location of all my speakers. What frequency range do you recommend looking at?

Also, could my room be the reason my woofer is extending so low? I really can't think of any other reasons.

 

[mike c]

just to confirm, you have put in the calibration file for the SPL meter right?

 

[avaserfi]

just to confirm, you have put in the calibration file for the SPL meter right?

Yeah, and I made sure it was the proper file.

 

[mike c]

how far is the sub to the mic when measuring? (now that the <20hz response doesn't look like it's 10db down like before ... I'm curious)

 

[avaserfi]

The woofer is about 6 feet from the mic/spl. I really have no idea whats going on. This Sunday I am going to start over and figure out whats going on after taking Bryan's suggestions.