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-   -   Comments on my first measurements? (https://www.hometheatershack.com/forums/rew-forum/34635-comments-my-first-measurements.html)

weverb 06-13-09 09:31 PM

Re: Comments on my first measurements?
 

Looks pretty good, but if you still have the localization problem then you might be better off moving the sub. Did you try the rear corner (blue response in previous graph) again?

Also, I am surprised there was no difference between 60 and 80Hz. Maybe brucek can shed more light on this.

The dip at 167 Hz. can probably be fixed with room treatments.

elee532 06-14-09 11:38 AM

Re: Comments on my first measurements?
 

Thanks weverb. After a brief listen, the localization seems less, but not gone, at 60Hz crossover. I have not tried the rear corner again, but I do plan to.

brucek, any light to shed?

Would I use a 2" or 4" absorption panel or some other type of treatment to address the dip at 167Hz? How would I go about determining the position for the treatment?

FYI, I do currently have many of the room corners treated with superchunk bass traps.

Thanks!

brucek 06-14-09 01:06 PM

Re: Comments on my first measurements?
 

I think the sub + mains looks fairly good.

At 60Hz, I can't imagine localizing a sub.

To determine if the 167Hz mains dip is a result of cancellation between the two speakers or between one speaker and the room, try measuring each one separately. A small movement of one might make a lot of difference.

brucek

weverb 06-14-09 01:46 PM

Re: Comments on my first measurements?
 

Quote:

elee532 wrote: (Post 172082)
Would I use a 2" or 4" absorption panel or some other type of treatment to address the dip at 167Hz? How would I go about determining the position for the treatment?

Check out this other cool feature REW has. It is call Energy Time plots (ETC). brucek has some good info in this post:

http://www.hometheatershack.com/foru...tml#post170156

It should help show if all your reflection points have been addressed.

elee532 06-18-09 08:47 PM

Re: Comments on my first measurements?
 

8 Attachment(s)
I took a few more readings. Any help understanding them would be most appreciated!

As suggested earlier, the first graph shows readings of each speaker. Red is the sub and mains together, green is the left front speaker, and gold is the right front speaker. Does this offer any insight into the dip around 169Hz? :dontknow:

The next graph shows my sub and mains with my pre-pro crossed over at 60Hz. The red line shows the crossover setting on my sub set at about one-o'clock (scale ranges from 40Hz to 160Hz). The gold line shows the crossover setting on the sub at about eleven-o'clock. The red line looks a bit flatter, but I wonder whether dialing up the crossover setting on the sub is contributing to my localization issue. I'm really confused by how the crossover setting on my sub works with the crossover setting of my pre-pro... and how do I go about finding the best setting for each?? :scratch:

The next graph shows my mains without the sub. Green is pre-pro set to large with no sub, black is 60Hz pre-pro crossover, and blue is 80Hz crossover. Not posting this one for any reason in particular, though it does seem an odd looking graph to me? ...actually, I just realized something, this contradicts my earlier posting showing no difference between 60Hz and 80Hz crossover setting. Guess I must have screwed up something the first time. Why do my mains dip like that between 30Hz and 80Hz?

Finally, I posted my first attempt at an ETC reading. To be honest, I have no idea how to read it. :huh:

weverb 06-18-09 09:15 PM

Re: Comments on my first measurements?
 

Quote:

elee532 wrote: (Post 173025)
As suggested earlier, the first graph shows readings of each speaker. Red is the sub and mains together, green is the left front speaker, and gold is the right front speaker. Does this offer any insight into the dip around 169Hz? :dontknow:

Ok, I am going to take a stab at answering this but hopefully Wayne or brucek will give us better information. It looks like both of your mains may be causing the dip. I think you can address this by trying to move them around. If not, I still think it can be handled by a treatment panel. By the way, that is a good looking graph even with the 167Hz dip!

Quote:

elee532 wrote: (Post 173025)
The next graph shows my sub and mains with my pre-pro crossed over at 60Hz. The red line shows the crossover setting on my sub set at about one-o'clock (scale ranges from 40Hz to 160Hz). The gold line shows the crossover setting on the sub at about eleven-o'clock. The red line looks a bit flatter, but I wonder whether dialing up the crossover setting on the sub is contributing to my localization issue. I'm really confused by how the crossover setting on my sub works with the crossover setting of my pre-pro... and how do I go about finding the best setting for each?? :scratch:

I would put the sub xo back to the red line setting. I would think you would want to bypass the sub xo and only use the pre-pro crossover.

Quote:

elee532 wrote: (Post 173025)
The next graph shows my mains without the sub. Green is pre-pro set to large with no sub, black is 60Hz pre-pro crossover, and blue is 80Hz crossover. Not posting this one for any reason in particular, though it does seem an odd looking graph to me? ...actually, I just realized something, this contradicts my earlier posting showing no difference between 60Hz and 80Hz crossover setting. Guess I must have screwed up something the first time. Why do my mains dip like that between 30Hz and 80Hz?

That's what we should see. I think this is correct. :scratchhead:

Quote:

elee532 wrote: (Post 173025)
Finally, I posted my first attempt at an ETC reading. To be honest, I have no idea how to read it. :huh:

You want to zoom in and only look at the first 10-20 milliseconds, not out to 2 seconds. You want to find all the major peaks in that time span and figure out the distances. Combinations of that distance will help you narrow down what surfaces need more absorption put on them. Here is an example of mine:

http://img200.imageshack.us/img200/7931/mainsetc.jpg

That second peak right after the initial one is either my back wall (couch is against my back wall) or the couch its self. The peak that I measured out to be 6 feet tells me something within 6 feet of the mains or mic needs to be addressed. I believe it is the ceiling. Then you can see the much smaller peaks that will then need to be address. This graph also helps when you trial place a panel to be sure you have it located correctly.

How did I do brucek/Wayne? :sweat:

brucek 06-19-09 08:03 AM

Re: Comments on my first measurements?
 

elee532, you have to switch the ETC plot from DBFS to %FS as weverbs plot shows.

The peaks will show the extra distance the signal had to travel to reach the mic. So a back wall at 3 feet from the mic will show up at 6 feet in the ETC.

brucek

weverb 06-19-09 09:18 AM

Re: Comments on my first measurements?
 

So my comments were correct? :rubeyes:

JohnM 06-20-09 06:13 AM

Re: Comments on my first measurements?
 

Quote:

weverb wrote: (Post 173097)
So my comments were correct? :rubeyes:

Seemed reasonable to me :)

The sub's own crossover should be set as high as it goes (or defeated if that is an option) so that the pre-pro is handling the crossover.

One thing the ETC highlights is fairly high distortion - those smaller peaks that happen before the main peak are distortion harmonics. Suggests your sub may be working fairly hard even though the measurement levels don't look especially high.

elee532 06-20-09 03:11 PM

Re: Comments on my first measurements?
 

Quote:

JohnM wrote: (Post 173267)
The sub's own crossover should be set as high as it goes (or defeated if that is an option) so that the pre-pro is handling the crossover.

This is still confusing me. :dizzy: My pre-pro is set for 60Hz crossover. As the two measurements below show (red line shows the crossover setting on my sub set at about one-o'clock (120Hz?) - the dial on my sub ranges from 40Hz to 160Hz - and the gold line shows the crossover setting on the sub at about eleven-o'clock (80Hz?).)

This higher crossover setting on the sub shows a flatter response line. Doesn't this reflect that the sub is now producing output all the way up to 120Hz? Wouldn't this be contributing to my localization issue? If my pre-pro is set to 60hz crossover, shouldn't the sub only be getting signal at 60hz and below? :dizzy:

Quote:

JohnM wrote: (Post 173267)
One thing the ETC highlights is fairly high distortion - those smaller peaks that happen before the main peak are distortion harmonics. Suggests your sub may be working fairly hard even though the measurement levels don't look especially high.

This is really vexing as well. The gain on my sub is at about 50%. Moreover, the bass extension frequency switch on the sub is set to 28Hz and Damping is set to Low. I would think these settings would reflect about the easiest load possible on the sub?

Thanks for any additional info!

http://www.hometheatershack.com/foru...s-submains.jpg


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