Preparing for REW+BFD

**HClarkx** · **02-01-08, 05:17 PM**

..... more on the 50 Hz ........ I'd still try it ... with low enough Q it might sound pretty good. They probably center up at 50 to avoid bottoming out the sub drivers. This is not an issue for you (your neighbors wouldn't allow it).

Harrison

**Trekari** · **02-01-08, 05:22 PM**

Now I'm unhappy.

The above graph includes speakers LCR+both subs at Phase 0, xover on subs 180, xover on mains 60, and xover on center 100

I arrived at those settings for Xovers via the following graphs.

MAIN SPEAKERS+SUBS!

Light Green=Double Bass
Red=50Hz xover
Gold=40
Purple 60
Blue 70
Dark Green 80

**Trekari** · **02-01-08, 05:27 PM**

Ok..bbiab with individually tested mains.

**Trekari** · **02-01-08, 05:40 PM**

CENTER only

Light Green Full
Red 40
Gold 50
Purple 60
Blue 70
Dark Green 80
Light Purple 90
Light Blue 100

Left Speaker only.

From top to bottom we have crossovers (subs turned off though) of:

Light Green Full
Red 40
Gold 50
Purple 60
Blue 70
Dark Green 80

RIGHT main speaker, same colors:
Light Green Full
Red 40
Gold 50
Purple 60
Blue 70
Dark Green 80

Finally, both main (L+R) without subs, same colors:

Light Green Full
Red 40
Gold 50
Purple 60
Blue 70
Dark Green 80

Left+Center+Right Xovers

Light Green Full
Red 40
Gold 50
Purple 60
Blue 70
Dark Green 80
Light Purple 90
Light Blue 100

**Trekari** · **02-01-08, 06:13 PM**

Update:

I'm a complete idiot. I had my distances in the recever set to:

Left 10.5'
Center 10.5'
Right 10.5'
Subs 10.5'

Actual measured distances?:
Left 126"
Center 126"
Right 126"
Subs 114"

No, the Behringer adds 1ms=1ft delay, so I added 12" to my subs ACTUAL distance....

*smacks self* Since it adds delay, I should've SUBTRACTED the 12"...******

Upon setting the distances correctly...

LCR+Subs ...sigh. Now I need to work on the xover of the subs.

**brucek** · **02-01-08, 07:06 PM**

Quote:

the Behringer adds 1ms=1ft delay, so I added 12" to my subs ACTUAL distance

Yes, that's correct.

Since the BFD delays the signal by 12", you want to tell the processor that the sub is 12" further away and it will (in essence) advance the signal 12" sooner...

brucek

**Trekari** · **02-01-08, 07:34 PM**

Then I'm at a loss as to what is wrong.

Do my LCR graphs by themselves look ok? I realize there are a few room problems..but in general?

*frustrated*
Jason

**HClarkx** · **02-01-08, 07:41 PM**

I mis-spoke I think (not unusual) .... I was hoping to see your mains alone with no crossover applied (I forgot to mention the crossover). That's what you want to look at (along with the subs alone and no crossover) to choose a crossover frequency for good blending. You can always correct problems with Audyssey or the BFD but it's nice to minimize problems before turning to them.

At this point I've been assuming the Behringer is bypassed. You don't want it in until you see what you've got to work with and what you can do without it.

Your last plot is encouraging though. What phase was dialed into the subs on that green trace with distances set correctly. And, what was the crossover frequency? You had the center and mains (and subs) running, so it's not all that helpful. You want to see subs alone, mains alone, and center alone. Then you choose crossovers from there.

But, I wanted to see the mains alone (no crossover) and the subs alone (no crossover) to see how they look in the potential crossover region. If both are flat, you can choose any crossover. If one has issues, you might minimize those by moving the crossover so that area is well down the crossover slope. Since your mains and subs are close together, they should look similar.

If the room issues between 60 and 120 are the same for the subs and mains, you can use any crossover you wish.

Incidentally, there are other considerations in choosing crossover frequencies. You take a load off of your mains by crossing over at a higher frequency. This allows you to run higher SPL with lower risk of damaging a main woofer and reduces somewhat the undesirable impacts of having higher frequencies sitting on top of lower frequencies in the main woofer. I forget what this issue is called .. maybe intermodulation distortion (IMD)? You also have lower risk of clipping in your mains amps since they are delivering less power. Clipping can destroy a tweeter.

The 12" error should have minimal effect below about 150 Hz.

Those "humps" above 100 Hz are disturbing, but Audyssey should smooth them out fairly well. At least the dip between 80 and 90 is gone.

I wouldn't turn Behringer or Audyssey on until you have done all you can without them.

**HClarkx** · **02-01-08, 07:46 PM**

Quote:

Trekari wrote:

Then I'm at a loss as to what is wrong.

Do my LCR graphs by themselves look ok? I realize there are a few room problems..but in general?

Jason

Jason, I don't think anything is wrong. You just need to look at each speaker to be sure it's performing as expected and well enough, be sure phasing is correct, pick a crossover, turn Audyssey loose, iron out any remaining issues and set a house curve with the BFD.

I didn't look close at the 12" issue, glad Bruce caught it.

Harrison

**brucek** · **02-01-08, 08:34 PM**

Quote:

Do my LCR graphs by themselves look ok?

Can't see the graphs??

**HClarkx** · **02-01-08, 08:37 PM**

Bruce, I think he's talking about his previous post ...

Harrison

**Trekari** · **02-01-08, 08:53 PM**

And my concern is that whenever I pick a crossover, my charts go to hell in a handbasket. It doesn't even seem like I can adjust the subs xover without something going completely haywire.

**Trekari** · **02-01-08, 09:07 PM**

For instance, if you'd like to understand why I'm so angry right now...

In my LCR graphs I posted what the response is with each speaker set to full range.

I also posted what my sub responses are individually, and combined.

After running Audyssey, here are two examples.

How am I supposed to be anything other than angry right now? Red is phase 0, purple is phase 180.

Keep in mind that without the mains at all, this was my subs response

**HClarkx** · **02-01-08, 09:13 PM**

By "subs crossover" you are talking about the crossover in your receiver/pre-pro, right? The crossover built into your sub should be turned off or set as high as possible and never touched again.

I don't think you've gotten the right measurements yet. Ideally you would do the following.

Left sub alone
(sub enabled, no sub crossover, receiver xover as high as possible ... or better yet, plug the sub into your main output and set that main to large)

Right sub alone
(same as above)

Left main alone
(receiver set to large, no tone control, etc.)

Right main alone
(same as above)

Center alone
(same as above ... set to large, etc.)

Use all above results to assure all is well, no fatal room problems, etc. then choose crossover frequencies. Use 80 Hz unless there is compelling reason to do otherwise. **

Pair up the mains and subs (one main and its adjacent sub) and look for proper crossover performance.

Pair up other main and that same sub.

Check each main with the other sub.

Pair up the center and subs and look for proper crossover performance.

The above is mostly to check sub phasing which has been an issue for you. The simple tests above will define that problem once and for all.

Then you are ready to run Audyssey and play with the BFG.

** Your mains and subs are close together so you could use 100 or 120Hz. Think about that later.

**Trekari** · **02-01-08, 09:24 PM**

I'll get the measurements tomorrow, but here is what I have to work with:

1) My receiver only has "LFE" crossover for the sub. That setting does NOT impact anything that is not delivered via an LFE channel. Currently and throughout all testing, I had that set to 120Hz.

The sub itself has a crossover that has been set to 180Hz for every measurement except where noted.

Pictures coming later, most of the information you've asked for I already posted in other graphs, but I'll post clarified ones in a few hours.

**HClarkx** · **02-01-08, 09:32 PM**

I agree about LFE, but I would put the subs on a main channel set to large to be sure there is no crossover impact whatsoever.

But, doesn't your receiver have crossovers for the mains to sub, center to sub, etc.? That's what we are trying to avoid by using the mains channels with them set to large.

Hang in there, I don't think you have problems that Audyssey won't handle well. Just got to be sure phasing is correct. Can't tell that with LCR all running or similar.

Harrison

**brucek** · **02-01-08, 11:25 PM**

Quote:

Do my LCR graphs by themselves look ok?

I can't see them...... here's what I see.

-------------------------------------

no show.jpg

-------------------------------------

brucek

**Trekari** · **02-01-08, 11:44 PM**

Left set to Full Range:

Right set to Full Range:

Center set to Full Range:

Left Subwoofer by itself, LFE at 120Hz (doesn't matter) and Xover on sub maxed @ 180Hz

Right Subwoofer by itself, same settings as Left (120LFE, 180Xover on Sub)

Both subs together, LFE 120, 180Hz Xovers

**Trekari** · **02-01-08, 11:45 PM**

Quote:

brucek wrote:

I can't see them...... here's what I see.

brucek

Sorry, I was referring to the graphs located in this post, with the multiple crossover points charted.

http://www.hometheatershack.com/foru...28-post79.html

**HClarkx** · **02-02-08, 02:06 AM**

Jason,

Now we're talking!

Your right sub performs better than your left, at least at the center seat where you were measuring. I'm tempted to suggest moving the left one over next to the right one, but I know that would be strange. But, it might be an interesting conversation piece.. "why are both of your subwoofers over there?"

In my opinion, you have relatively good sub performance. The dips at 85 and 120Hz (both subs together) isn't wide enough to get very excited about. The dip up at about 130 Hz is pretty bad, but won't be a problem if you keep the crossover down around 100 Hz or less. Based on the subs, I'd use the tried-and-true 80 Hz crossover (isn't that Dolby's recommendation and also the THX standard?). You are better than +/- 4 db from 20 to 80. That's hard to beat.

As a wild guess, the ~85 Hz dip is your left wall and the 130 Hz dip is your ceiling. You have two reflected waves from your ceiling, twice what you would have with a flat ceiling, and that explains the deep notch at 130 Hz and the second low up at 180 Hz (you get a comb effect from any surface like that). But, this paragraph is just to help understanding, it doesn't change the next above recommendation.

Your combined sub test was a good idea. It shows 6db gain over either sub alone, so confirms that your two subs are in phase with each other. We wondered earlier if one of them was wired wrong.

Unfortunately, your mains suffer from some reflections as well. The deep dip at about 120 Hz in the left channel is probably that ceiling again. It's at a different frequency from the big sub dip because your mains are closer to the ceiling (further off the floor). I'm guessing the left main is closer to being right under the ridge.

It's not practical to crossover high enough to minimize the effect of that dip because you would just bring the similar but lower dip on the subs into play. That dip is very narrow and that's good. It is only really serious in the left main and that's good because at 120-150 Hz, most material is the same in both main channels so the right channel helps support the left with its lesser dip.

The +/- 8db variations in the mains above 120 Hz are unfortunate, but will be largely smoothed by Audyssey. At least one of them (one close to 200 Hz) is the reflection off the wall that is 16" behind your ears in the center and left seats. If your mic was 18" from the back wall, the dip would be exactly at 185 Hz. So, more sound absorbing material behind your head would help, but only with one of the dips that is visible on these charts. I say that because that dip will repeat as you go up in frequency, though at higher frequencies, the wall-hanging you mentioned is probably more effective.

The center is more problematic. It has a very deep notch up at about 150 Hz. That's the only one that gives me pause. It might be a combination of reflections (note the two close proximity dips). You might try putting the center above your TV if that's a credible option. That would worsen the refection off the back wall (direct wave hits the backwall closer to 90 degrees), but might move the one from the ceiling away from it. But, again, a complete dropout of 5 or 10 hz (the width of this notch) isn't much of a penalty. Also, Audyssey will help with it. Also, you will hear mostly voices in the center channel, and this is below the female voice range and at the low end of the male voice range so won't have much impact. Roucous sounds from movies that go to the center don't need to be perfect fidelity. So, you are home free on the center in my humble opinion.

I'd cross the center at 80Hz along with the mains. It's good for that in that it is fairly flat down to 50 Hz. The tiny notch at 60 isn't an issue, but will be comfortably below the crossover frequency (i.e., it will be well down the crossover skirt and so not an issue).

So, I think you've got a good system going. Now you've got to be sure the subs and mains are in phase and the receiver crossover is working well. Do that by setting the mains to small, setting the crossover at 80, enabling one or both subs and one main. Enabling both subs will put the subs 6 db above the main, but that's easy to take into account if you want to do that. I think I'd do that because you get smoother sub peformance with both enabled. I'd test each main individually with one or both subs. Don't drive both mains at the same time.

Then test the center paired with one or both subs and an 80 Hz crossover.

If all looks good, crank in the Audyssey and see what it can do. You will probably see significant improvement, but keep in mind that the Audyssey system is also improving decay and correcting time alignment which don't show up in frequency response plots (time does to some extent if it's really bad to start with). I.e., the Audyssey correction is doing more for you than we are measuring here (though you could go further with the waterfall plots and such).

If you want to fine-tune the sub phase, you can play with that by changing the sub phase setting or the sub distance. That should have minimal effect as long as the subs are close to start with (they should be if the are not out by 180). Do that before you run Audyssey. Otherwise you would have to re-run the full Audyssey setup each time you make a sub phase change.

It's late. At 66, I don't usually function very well this late. If anything above doesn't make good sense, let me know.

Keep up the good work Jason.

Harrison

**Wayne A. Pflughaupt** · **02-02-08, 08:05 AM**

Quote:

brucek wrote:

I can't see them...... here's what I see.

-------------------------------------

-------------------------------------

brucek

I can’t see them either, although a link to a picture in one of my e-mail notifications worked – strange...

Regards,
Wayne

**Trekari** · **02-02-08, 10:13 AM**

I received a PM suggesting that certain key members were not able to view my graphs and a question of whether I'd be willing to post them on a site other than comcast's personal web pages.

Hah! Like I'd refuse help in this problem!

The graphs have been uploaded to HTS and are shown below in the following order:

Center Full Range
Left Main Full Range
Right Main Full Range
Left Sub by itself (Xover 180 on the sub, 120 in the receiver but that only affects LFE)
Right Sub by itself, same settings
Both Subs together, Phase 0

**Trekari** · **02-02-08, 10:28 AM**

Harrison - I thank you for your post and helpful suggestions.

I haven't forgotten about them, it's just a bit early in the morning to start running more sweeps

**brucek** · **02-02-08, 11:49 AM**

Thanks, I can see those fine now. I have a few comments.

The mains and center measurements are taken at far too low a level. The measurements should all be taken with a target level of 75dB. The graphs should then be posted at the standard 45dB-105dB vertical scale. You see in the red plot for example where the signal has some sharp dips at about 30hz and then the signal starts to rise? It actually isn't rising, the signal is in the noise at that point. The rising portion is noise, not signal. So, take all measures at 75dB.

Personally, I see very little problem with your response(s). I am of the camp that I want to see the sub signal(s) alone with no mains, but I want it with the crossover engaged. The same holds for the mains. I wouldn't concern myself with measuring the center channel - it's mostly dedicated to voice any way. The prime concern is the subs and the mains and how they integrate together.

I don't understand your statement about the sub crossovers. The sub should be crossed over using the receivers bass management with the subs own filters bypassed or maxed with the dials...

brucek

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