Try to EQ Sub plus L/R powered mains?

4110 Views 29 Replies 5 Participants Last post by weverb, Mar 4, 2009

NCDave

Discussion Starter · Feb 12, 2009

Funny, I've read a bunch over here but I guess this is my first post.

I've played with REW and BFD for a while, and am not having much success getting my room EQ to settle down. I think I know why, but don't know how to attack the problem. I did a few searches here and found that it's not a good idea to try to EQ differing subs. Also multiple subs in general are hard in weird-shaped room. I have all three.

I have the "powered bass stands" (PBS, discontinued from AV123), with their ELT-1 bookshelf speakers (also discontinued.) The PBS are essentially 8" sealed, powered subs, in tall boxes that double as stands for the L/R speakers. I knew I had a poor room response (very heavy around 40 Hz) from previous sweeps I'd done with REW. Never tried to EQ it, because the subs would need separate EQ, and right now they get a speaker-level signal. [The PBS get a full-range signal from the receiver--set as "large"--and I use the PBS' crossovers to send the upper range to the ELT-1's. There is an option to send the PBS a separate line-level signal, and there is a line-level out for daisy-chaining.]

I can supply a link to AV123's Retired Products archive with the PBS, if you need...not sure I can do that with 0 posts.

Anyway, this week, I added a sub from the Outlaw sale (LFM-1 Compact). This sub gets me the low end (mid-20's) which was missing with the PBS. I like hearing these, especially when playing low-volume jazz--I can hear the bass line now

BUT I hear definite resonances in the room at a number of frequencies. REW has confirmed this.

I've been trying various phase and level settings on all three "subs" (counting the PBS as subs), trying to tame the response, but this is just a confusing mess. I worked out some filters on the BFD and got nowhere near the predicted response, even with the PBS turned off.

So...I need to attack this problem in pieces, I think, and maybe just give up on the PBS(?) I would appreciate your comments on these ideas & questions. I need to step back and develop a plan...

1) Don't try to EQ everything at once (sub plus main/PBS). For now, maybe disconnect the PBS and use just the Outlaw by itself or with the L/R ELT-1 bookshelves. Set the receiver crossover to 80Hz.

-- Should I turn off the L/R speakers for this test, too?
-- Should I use the sub cal signal or the speaker cal signal?

2) If I keep the PBS in the test with the mains, maybe set the fronts to "small" to prevent the PBS from contributing much? This might be like not using the PBS at all.

3) Give up on the PBS/ELT-1 combo and go buy non-powered, near-full-range speakers for L/R. I feel like I need a near-full-range because this is used for 2-ch music as well as HT, and the bookshelves plus sub are a bit lacking in the midrange for 2ch.

I don't know. I'm a bit at a loss here. Not even sure I've outlined the problem clearly. :help:

Thanks,
Dave

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NCDave

Discussion Starter · #21 · Feb 28, 2009

Here are the individual speaker responses, again, superimposed, with annotations. It's pretty clear that the ELT's response in this room causes the 122Hz bump. But it's not clear to me why the range from 200-300Hz is so low in the final response, unless it's just because of the weird room.

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NCDave

Discussion Starter · #22 · Feb 28, 2009

And if the XR55 is setting the fronts to SMALL, and crossing them over at 80Hz, how in the world are the PBS' still playing at the level they are, so far down in the response? Is that another room anomaly?

Here are the connections:

XR55----(speaker level)---->PBS w/crossover----(speaker level)---->ELT
|
|----(line level)---->LFM1c Subwoofer

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Wayne A. Pflughaupt

· #23 · Feb 28, 2009

NCDave said:
And if the XR55 is setting the fronts to SMALL, and crossing them over at 80Hz, how in the world are the PBS' still playing at the level they are, so far down in the response? Is that another room anomaly?

You might want to consult your manual or do some further testing. We’ve had people here who had this problem and eventually discovered that their receiver’s bass management only worked for digital sources and signals.

That said, you might also want to take some readings of your L/R separately. I expect that the left speaker has much more pronounced bass than the right one.

Still, the ELT's are supposed to be +/-3dB down to mid-60's or so. That's why I'm thinking something about this room is just sucking down that part of the response...

That’s fairly optimistic extension for a speaker with such small woofers, unless they’re unusually inefficient. And yes, the room makes a difference. Small rooms reinforce bass; large rooms “soak” it up. Keep in mind that the speakers “see” all those areas open to your family room.

Regards,
Wayne

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NCDave

Discussion Starter · #24 · Feb 28, 2009

Wayne A. Pflughaupt said:
You might want to consult your manual or do some further testing. We’ve had people here who had this problem and eventually discovered that their receiver’s bass management only worked for digital sources and signals.

Well, I sure hope not. The Panny's manual is pretty bad, and not very specific about the crossover, but I can test that theory with sweeps using different crossovers.

you might also want to take some readings of your L/R separately. I expect that the left speaker has much more pronounced bass than the right one.

Good idea, and you are probably right about that, since the left speaker has two-wall reinforcement. And while I'm at it, I guess I should look at each PBS separately. This could get complicated.

onder:

Thanks Wayne.

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NCDave

Discussion Starter · #25 · Mar 1, 2009

I did about 20 more measurements. I'll post a few here. Bottom line is that I have a lot of room gain on the left side, plus I have a nice room mode in the region the PBS are operating.

First question was: does the XR55 apply the crossover to analog inputs? The answer is yes. It's 12dB/octave. I verified this using the ELTs only.

Second question was: are the left and right ELTs (and PBS) significantly different because of room gain? The answer again, is yes.

The first plot is the left and right ELTs, swept individually, and then plotted together, with the 80Hz crossover in the XR55. The blue line is the left ELT. Sure enough, there is the 122Hz mongo peak:

The next plot is the left and right PBS, set at equal volume, swept individually, and plotted together. The purple line is the left PBS. Needs to be turned down, but there is a ton of room gain around 40-50Hz. Remember, they are supposed to be dropping 12dB/oct at 80Hz.

The next plot is the same as the previous one, except I have turned down the volume one notch on the left PBS:

That's better, but the overall response (all speakers plus sub) still has the problems with the left ELT's room mode. I tried most combinations of PBS phase and ELT phase (flipped leads). Most of these obliterated the overall response. The plot below gives two configurations: with and without leads to both ELTs flipped. Blue one is with leads flipped:

I still have the issue in the 200-300Hz range. It's apparently being caused by the left ELT, and I just might not be able to do anything about that. The room's options are limited.

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weverb

· #26 · Mar 2, 2009

Wayne A. Pflughaupt said:
You might want to consult your manual or do some further testing. We’ve had people here who had this problem and eventually discovered that their receiver’s bass management only worked for digital sources and signals.

That would be me! :hissyfit:

Dave - have you tried your sub in the opposite corner up by the right speaker? Also, do you have enough slake in the wire to the right main to try moving it closer to the listening position? Maybe you can measure and find the better location, and when not in use, move it back against the wall like in your layout.

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fredk

· #27 · Mar 2, 2009

NCDave. Looking at the response from your mains, it looks to me like you would greatly benefit from some broadband traps. It dosn't look like there are many places to put such beasts (not to mention WAF).

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NCDave

Discussion Starter · #28 · Mar 4, 2009

weverb said:
Dave - have you tried your sub in the opposite corner up by the right speaker? Also, do you have enough slake in the wire to the right main to try moving it closer to the listening position? Maybe you can measure and find the better location, and when not in use, move it back against the wall like in your layout.

I've not tried the sub in the right front corner. When I originally selected the left rear corner, I had placed the sub on the couch, and then used my meter to check levels at several possible sub locations. The right front corner was very low level--pretty much like no corner at all.

The room is hard to work with. The right front speaker really can't come closer into the room. Yes, there's slack in the wire, but pulling it forward puts it into the main walking path from the kitchen area to the stairs going up. The kids are bound to hit it.

the system doesn't sound bad. It's really just the engineer in me, looking at the plots. And I made the mistake of going to listen to the Rocket 450's. But I guess I'm not going to spend more money on nicer speakers if the room is just going to suck the life out of them.

What's ironic about all this is that there is really only one way to set up the room for music. But I still wired everything in the walls for multiple layouts. The equipment can go left or right side, and drive speakers to the opposite side and to the rears. Both sides also have wired Ethernet. The sub is a bit different. The left front is the main source point for the sub because there are point-to-point shielded twisted pairs going to the right front, left rear, and right rear, all from the left front. I originally had a daisy-chain for the sub (four locations), but it was too noisy, so I changed to pt-to-pt. So I have some other options, but they are mostly worse than I have now, I think.

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NCDave

Discussion Starter · #29 · Mar 4, 2009

fredk said:
Looking at the response from your mains, it looks to me like you would greatly benefit from some broadband traps. It doesn't look like there are many places to put such beasts (not to mention WAF).

LOL. Yeah, traps would probably help. My wife is a sweetheart, she really is. And she had no problems with the speakers and the sub. But I showed here some pictures of bass traps and such, and well, she kinda drew the line in front of that proposal.

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weverb

· #30 · Mar 4, 2009

NCDave said:
I've not tried the sub in the right front corner. When I originally selected the left rear corner, I had placed the sub on the couch, and then used my meter to check levels at several possible sub locations. The right front corner was very low level--pretty much like no corner at all.

You should try getting a REW graph in that location just for a comparison.

NCDave said:
The room is hard to work with. The right front speaker really can't come closer into the room. Yes, there's slack in the wire, but pulling it forward puts it into the main walking path from the kitchen area to the stairs going up. The kids are bound to hit it.

I meant to just place the speaker there during listening times and move it back against the wall when not in use.

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