First graphs, advice? - Home Theater Forum and Systems -

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post #1 of 7 Old 03-16-11, 05:17 PM Thread Starter
Join Date: Mar 2011
Posts: 48
First graphs, advice?

Hi guys.

So I finally got some (non-messed-up) graphs together.

I have a 7.2 setup. Most of the measurements I did were in stereo mode, but I did some with "all channel stereo" as well, just for kicks.

I have tile floors over concrete, 2 very small rugs, one of which is near the listening area.
2.5 walls are drywall with studs over concrete (12" from concrete), 1.5 walls are drywall/studs with fiberglass insulation behind them, and smallish bare concrete rooms (also behind )

The room is about 3300 cubic feet, and I'm using one half of it as the HT area.

Anyway, I played with a bunch of xovers for my FL/FR speakers, and 60hz was by far the best in terms of response (both with & without audyssey). For comparison, I posted the full band, 40, and 60 xover graphs. Anything above 60 was much worse, can post if it would be helpful)

I am guessing the general advice for bass applies? Carpets on the floor, bass traps if able?
(One issue I'm a little concerned about in terms of carpets is that I plan to hang my surrounds & rears from the ceiling, upside down. The surrounds are Mirage OMD-5s, which are omnipolar, and the manual says that while accoustic treatments are great, don't apply them at the first point of reflection for these speakers... which would be the floor. Right now they are mounted on the wall, about 5' high (the ceiling is 7'8"), right-side up)

(The mains are OMD-15s, and I have an OMD-C1 center. And 2 rythmik F15HP subs, one in a corner near the right main, and the other behing the listening area, right under the rear left speaker). I had the subs speakers facing the wall at one point, but REW showed big nulls when I did that, so I spun them to face the listening area, and the response was much better.

For the all channel stereo tests, the center was crossed at 100 hz, the surrounds & rears at 90 hz (so I don't know what is causing that huge difference in the bass test)

Would moving the mains around a little, or playing with the subs phase, help? (Though audyssey supposedly sets both subs phases for me... I'm using the Onkyo 3008, which has that Multi-eq 32 xt)

Any help would be greatly appreciated!

(First graph the mains are always crossed at 60hz)
(The last graph is stereo only)
Attached Thumbnails
First graphs, advice?-bass-compare.jpg  

First graphs, advice?-full-range-compare.jpg  

First graphs, advice?-bass-compare-2.jpg  

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post #2 of 7 Old 03-17-11, 09:43 AM
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Re: First graphs, advice?

The all channel stereo is just causing comb filtering, so not worth bothering with. The other graphs look pretty good though, would be interesting to see a waterfall plot.
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post #3 of 7 Old 03-17-11, 10:42 AM Thread Starter
Join Date: Mar 2011
Posts: 48
Re: First graphs, advice?

JohnM wrote: View Post
The all channel stereo is just causing comb filtering, so not worth bothering with. The other graphs look pretty good though, would be interesting to see a waterfall plot.
I'll get a waterfall plot when I get home tonight.

When you say pretty good for the other graphs, does that mean that I likely wouldn't notice a substantial difference with some rugs & bass traps put in, and the stairway behind the HT area blocked off with a door or something? (Which I probably need to do anyway... the stairway has a door at the top, but even moderate volumes can be very clearly heard on the floor above... which is a problem for my wife)

What about that large null at 157hz? When I was looking at the phase, it appeared (to my noobish, untrained eye) that my mains were interfering with each other there... I'll post a phase + spl plot if it would be helpful. I assume a little repositioning would be helpful if that was the case? (I could be wrong... maybe its just the listening position?

I guess another thing I can do is test (with audyssey off) with the different possible listening positions to see where the response is the best, and then do another audyssey run there.

I need to learn how to use the RTA I think
(I tried it, but it doesn't come with sound... am I supposed to use some external calibration signal? Would be nice to move the mic to a few different positions and see the difference without having to full remeasure each time, or to scoot the mains around a bit and see the difference)

EDIT: I did some reading around. Waterfall plots look really cool, and give more info. Nice. I'll definitely post some. I haven't been reading up on the RTA stuff though... maybe some other time.

I'll also have to play around with my subs' amps' settings. (Rumble filter affects <20hz, extension filter @14 vs 20 vs 28, damping low vs med vs high would affect the waterfalls I'm betting...)
The graphs above were with rumble filter off, extension @ 14 hz (I'm told this bumps the output at 14hz, and rolls off below that), high damping.

Each sub has a single band PEQ on it as well... I'm guessing if I want to use that, I should measure each sub individually (not through the AV? Just plug right into the subs RCA input?) and use PEQ to tame the biggest resonance for each sub? Or is it much more complicated by having 2 subs, and I can't just correct their resonances individually, but need to measure both together? (Although I'm guessing that the PEQ settings would need to be different on each still... not sure how to calculate those though)

Also, those graphs above are linear, not logarithmic, because I hadn't found the "how to prepare a graph to post", just the "how to post a graph" thread.

EDIT 2: I'm also kind of curious about the full band vs others in my 3rd graph. I get that big, wide dip from 28-50, with that very sharp dip between 40 and 43/44, but then I have pretty smooth response from 50 to 75. Whereas with the 40 or 60 hz crossover, I'm getting pretty smooth response from 22-50 (I wonder whether upping my extension filter from 14 to 20 or 28 would help tame that peak I'm seeing between 17 & 22? I'll have to test that too).

Here is what I find confusing: With full band, why is the response so different from 40+ compared to the 40hz crossover? (I had double bass on with full band, so the sub was going too... my understanding is that above 40hz, full band with double bass vs 40hz xover should be identical output from the receiver, but this is obviously not the case!?). I am also a little confused by how similar the 40hz & 60 hz crossovers look...

Last edited by morik; 03-17-11 at 05:39 PM.
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post #4 of 7 Old 03-17-11, 09:50 PM Thread Starter
Join Date: Mar 2011
Posts: 48
Re: First graphs, advice?

Ok here are some different graphs where I played around with the damping & extension. The settings I currently have EQed with audyssey are the 14hz extension, high damping, but from testing all 9 combinations (14/20/28 extension, low/med/high damping), the 28/low damping setting had the flattest uneqed response. It drops off of course much faster than the 14hz/high, which is still hitting 70db @ 5 hz, which is very good low end extension. However, given that I can barely hear a 35hz tone at -3dbfs, and certainly not a 20, I don't know how much to value such low extension over the flatter response of the 28/low setting.

I'm going to play around with sub positions a bit and retest with different extensions/damping factors, and maybe play with my one band PEQ on each sub (though they are separated and not placed symmetrically at all) then rerun audyssey to see what it can do for me.

(I wonder whether I should try different settings on each sub, instead of mirroring them? Guess I'll play with that too)

EDIT: There are some graphs on the manufacturer's website indicating how the different filters affect the frequency response...
I don't understand why 14 (& 20) at all damping levels get that null around 66hz (which audyssey moved to 56), while I don't see it at all with the 28hz extension filter...
Attached Thumbnails
First graphs, advice?-14vs28.jpg  

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First graphs, advice?-audyssey-off-14-high-waterfall.jpg  

First graphs, advice?-audyssey-off-28-low-waterfall.jpg  

First graphs, advice?-audyssey-14-high-waterfall.jpg  

Last edited by morik; 03-18-11 at 01:40 AM.
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post #5 of 7 Old 03-18-11, 12:20 AM Thread Starter
Join Date: Mar 2011
Posts: 48
Re: First graphs, advice?

Ok, so I played around some more with positioning, and with the single-band PEQ on the plate amp.

In terms of positioning, it turns out my sub crawl was correct--the places I had them worked the best. I didn't try all over the room, but did try the majority of available spots. (There is one more spot I could try, but it has my AV on a rack there right now. Once my furniture situation is resolved I can test putting one of them there)

I think I get the flattest FR with the "medium PEQ" set (the knobs are all analog, thats just what I'm calling it... around -5 db, around 29hz, with a moderate bandwidth)

But, the heavy PEQ set (-12db, largest bandwidth, a little lower on the frequency, maybe 27 hz) might have better decay? I'm not really sure...

Anyway, here are a bunch of graphs. Sorry if this is too many graphs
(Should I not disable the x axis tilt on the waterfall graphs? I found it a bit easier to read for some of them, and forgot to turn in on when saving... if its easier to read with the tilt, let me know for future reference)

Is it worth it to run each set of settings through audyssey to see what I get out of it?

Is that hugely long decay at 17-20 going to be noticable anyway? (Or is it even ok to have?)
If so, maybe the medium PEQ set is good?
Or should I just roll along with PEQ off, see what Audyssey results in?

Thanks for the help!

EDIT: Added a graph of all the FRs together, along with the base one (the 28hz extension, low damping from prior post)

EDIT 2: In all of these, I'm running both my FL & FR speakers (OMD-15s, crossed at 60hz) and 2 Rythmik Audio F15HPs (with the 550 amp). One main is near a corner (4' from back wall, maybe 2 feet from side wall), with the sub behind it in the corner, but speaker facing towards listening area (towards wall introduces large nulls in the midbass)
Second main is maybe 1/3rd of the way down the width of the room, also 4' or so from back wall. Second sub is behind the listening area (on the other side of the room from the mains & first sub). The listening area is in one half of my basement, the other half has a bunch of other stuff, no speakers/subs over there (from this set of equipment at least).

One thing I'm starting to wonder about is how much the different positions are affected by phase differences... I have both subs at 0 phase/delay since that is what the audyssey guide says to do when setting them up. So I wonder whether I'd actually get better response (post-audyssey) in a position which looks worse, but just due to phase as opposed to room nulls? I think I read that the waterfall plots can help me figure this out somehow?

EDIT 3: Reading a few other posts, it looks like the 600ms graphs may be the most helpful? (If so I can remove the others to make everything more readable.)
Also, it looks like I may have set my window too large compared to other graphs... what are the proper settings? 45 to 105db, 15-200 hz, 600ms time range, ?? window (I used 600ms)?
Attached Thumbnails
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First graphs, advice?-medium-peq-fr.jpg  

First graphs, advice?-heavy-peq-fr.jpg  

First graphs, advice?-20hz-peq-8-so-moderate-bandwidth-300.jpg  

First graphs, advice?-20hz-peq-8-so-moderate-bandwidth-600.jpg  

First graphs, advice?-20hz-peq-8-so-moderate-bandwidth-900.jpg  

First graphs, advice?-medium-peq-300.jpg  

First graphs, advice?-medium-peq-600.jpg  

First graphs, advice?-medium-peq-900.jpg  

First graphs, advice?-heavy-peq-300.jpg  

First graphs, advice?-heavy-peq-600.jpg  

First graphs, advice?-heavy-peq-900.jpg  

First graphs, advice?-all-together.jpg  

Last edited by morik; 03-18-11 at 01:50 AM. Reason: add all together, mention baseline from previous post
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post #6 of 7 Old 03-18-11, 06:32 PM Thread Starter
Join Date: Mar 2011
Posts: 48
Re: First graphs, advice?

In case its relevant, here is my floorplan and speaker positioning as well. When my wife is watching something with me, she can't stand to have the couch "so close" (9 ft or so) from the TV, and has me slide it back about as far as it can go without hitting the subwoofer... :-/
But I don't want to EQ for that, unless that area would be better or almost as good anyway.

S1 & S2 are the sub positions.
Attached Thumbnails
First graphs, advice?-basementfloorplan.jpg  

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post #7 of 7 Old 03-19-11, 07:51 AM Thread Starter
Join Date: Mar 2011
Posts: 48
Re: First graphs, advice?

So I did some more testing... I set up the 28 hz/low, with PEQ, and ran Audyssey... the results were similar to 14/high no PEQ--dips at around 55 (and then those same dips in the 100s)

So, I went back to testing with 14hz extension, high damping. Looking at different crossovers, it actually looked like 80 was good, aside from that null at 77. (The other crossovers had more scattered nulls, with the biggest the same size as the 80 crossover, so...)

I know people say (from what I've read) not to apply EQ after audyssey... but look at these graphs. When I'm by myself, I can always sit in the optimal spot. When I'm not, I can flip the EQ switch off... (I tested at several different locations, and except for behind me, the PEQed response was actually better or as good in most of them)

I tried playing with the sub distances, but when I started to fix the dip at 78hz, I'd get a deeper one at 55 or so. And have slight other effects.

So, since I was having phase alignment issues, I decided to use the PEQs on the subs separately from each other, to help them get out of each others way or overpower the other's wave a bit more:

I have sub 2 PEQed at 78hz or so, narrowest band possible, -12db. For some reason this caused more of a dip at 55 or so, but I put the other sub at a +3 gain around 51hz, moderate bandwidth. (Not sure why, but putting the frequency knob at 55 resulted in the 60s being bumped instead)

These PEQs can be turned off with a simple flip of the switch... given that, I can't really see a downside to using them... am I missing something?
Attached Thumbnails
First graphs, advice?-default-fr.jpg  

First graphs, advice?-peqed-fr.jpg  

First graphs, advice?-default-waterfall.jpg  

First graphs, advice?-peqed-waterfall.jpg  

First graphs, advice?-default-spectogram.jpg  

First graphs, advice?-peq-spectogram.jpg  

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