EQ Question - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 30 Old 01-03-2011, 06:04 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
This may be a dumb question, but I have dual subs and am trying to EQ them. REW is recommending a 10 db cut at 40hz. Here's the question, do I apply a 10db cut to both subs at 40hz, or a 5db cut to each sub at 40hz??

Pretty sure it's a 10db to each sub?

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
Sponsored Links
Advertisement
 
post #2 of 30 Old 01-03-2011, 06:10 AM
AVS Special Member
 
gperkins1973's Avatar
 
Join Date: May 2009
Posts: 1,519
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 13
Pbc,

I have duals and all you do is take a combined REW measurement and apply your cuts from that. If I remember right yours are co located aren't they and if so they are the same as mine ish!

Do that and you will be fine.

cheers

Graham
gperkins1973 is offline  
post #3 of 30 Old 01-03-2011, 06:13 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
So if REW is saying use a -10 db cut, I apply a 10db cut to each channel on my EQ (my subs are not colocated, but are both equidistant to the LP).

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
post #4 of 30 Old 01-03-2011, 06:25 AM
AVS Special Member
 
gperkins1973's Avatar
 
Join Date: May 2009
Posts: 1,519
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 13
When I used REW I made a cut to the combined response and not to each channel because the responses from each sub will be different.

For example 40hz one sub may be higher or lower in spl than the other one. That is the beauty off dual subs is that when you take a combined response it will be hopefully much smoother and not need to much EQing.

Have you taken a measurement off each sub and then a combined one.

Also what EQ are you using.
cheers

Graham
gperkins1973 is offline  
post #5 of 30 Old 01-03-2011, 07:08 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
I think we're saying the same thing, yes, when I measure I'm measuring the combined response of both subs (not each sub individually). REW is telling me the combined response requires a 10db cut at 40hz, so I'm applying a 10 db cut to EACH channel on my subwoofer's pro amp. I.e., I have my EQ (trying out the MiniDSP) with 2 channels out going into channels 1 and 2 of my RMX5050. Applying the cut to each of those channels.

Must be correct given it's smoothing out my response nicely. Just wanted to confirm as my head kept thinking "maybe if the combined response needs a 10db cut, then I need to apply a 5 db cut to each subwoofer since 5+5=10". The finance/accountant guy in me I guess.

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
post #6 of 30 Old 01-03-2011, 07:21 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
Next question, I applied a low shelf of 5db at 27hz, a cut of 10db at 40hz (Q of 5). Then ran Audyssey. The pre Audyssey response is in red, the post Audyssey response is in gold. I had to cut the volume by 10db or so for the post Audyssey response because for some reason my subwoofer level was boosted 10db after applying Audyssey. Any ideas why? I'm using a Marantz AV7005, Dayton ECC-6 (or whatever) mic, and MobilePre USB sound card?


LL

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
post #7 of 30 Old 01-03-2011, 07:28 AM
AVS Special Member
 
gperkins1973's Avatar
 
Join Date: May 2009
Posts: 1,519
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 13
I don't look at it as making an equal cut from each sub as I look at it as just one sub so I am just making a 10db cut from 40hz from what is essentially one sub because it is just a single measurement that you are taking. That would only apply if you were EQing them seperately. This is my understanding off it.

On my subs at 40hz one would need a cut and the other would need a boost so that theory off equal cutting wouldn't make sense.

cheers

Graham
gperkins1973 is offline  
post #8 of 30 Old 01-03-2011, 07:40 AM
AVS Special Member
 
Join Date: Mar 2003
Posts: 4,509
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Liked: 606
That's what Audessey does. I shut it off after it boosted my sub by 6-8dB.

As the graph shows, instead of cutting the peak, it boosted everything around it to the peak level, which I discovered by immediately hearing the SW level bump and then comparing the close mic to the LP mic responses.



As to why it does it that way, I haven't a clue, but that method certainly isn't conducive to optimal performance on the average.

Bosso
bossobass is offline  
post #9 of 30 Old 01-03-2011, 07:47 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
Well, ended up figuring out that when I run the Auto Audyssey routine it apparently engages Dynamic EQ which was causing that strange boost. I eliminated that, then also had to reduce the subwoofer channel level by 3 or 4 db (can't recall exactly). I also played with the distance control on the AV7005, and came up with this response:



Pretty good!?

Really enjoying this MiniDSP EQ device...may just sell my DCX2496 if they make a few changes to the software in the MiniDSP!

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
post #10 of 30 Old 01-03-2011, 07:51 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
Not sure if these graphs add anything to the discussion as I haven't spent time trying to understand what they are saying ...
LL
LL
LL
LL

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
post #11 of 30 Old 01-03-2011, 07:53 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
Finally, the pre and post EQ ...



Edit: mains were off in the pre (just the response of the dual subs is displayed)
LL

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
post #12 of 30 Old 01-03-2011, 08:08 AM
AVS Addicted Member
 
LTD02's Avatar
 
Join Date: Oct 2003
Posts: 15,897
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 109 Post(s)
Liked: 831
nice work pbc.

for those who may know, i'm curious why the waterfall looks so different from the single line frequency response. is the resonance from 70-100hz building up to show a flat line in the frequency response? something doesn't seem quite right here. spl with no resonance should appear very different from spl that is coming from resonances, no?

Listen. It's All Good.
LTD02 is online now  
post #13 of 30 Old 01-03-2011, 08:39 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
Decided to try inserting my PB13 in sealed mode (which is nearfield to the LP) into the equation, here is what the response looks like with it ... not pretty ... wondering if I should bother trying to implement it now as a lot more EQ is needed...


LL

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
post #14 of 30 Old 01-03-2011, 08:40 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
Hmmmm ... also wonder if the MiniDSP has an internal high pass at 10hz or something along those lines given the sharp roll off right there, though it could just be my subs I guess. Will have to try using the DCX2496 with the same settings next ...

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
post #15 of 30 Old 01-03-2011, 09:00 AM
AVS Addicted Member
 
LTD02's Avatar
 
Join Date: Oct 2003
Posts: 15,897
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 109 Post(s)
Liked: 831
that would fix your 40hz null. :-)

have you tried frequency sweeps while rotating the phase on the sealed pb13?

seems a little moot though. don't your two dual subs provide sufficient spl?

Listen. It's All Good.
LTD02 is online now  
post #16 of 30 Old 01-03-2011, 10:09 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
Yeah, prob have way more than enough headroom in my 1700cube family room.

BTW, inserted the DCX back into the mix and tried to match the same settings (not possible since the MiniDSP allows a Q setting for the low shelf, and I couldn't get the exact same frequencies or Q's in some cases, i.e., off 1hz or 0.1Q and couldn't adjust manually on the DCX but close enough). Here are the two responses and waterfalls ... (darker purple is DCX - note the gain structures are different on the DCX vs MiniDSP and I had to increase the gain on the 5050 to compensate as best I could)...






LL
LL
LL

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
post #17 of 30 Old 01-03-2011, 10:17 AM
AVS Addicted Member
 
penngray's Avatar
 
Join Date: Feb 2006
Location: Florida
Posts: 26,779
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 29
Quote:
Originally Posted by pbc View Post
Hmmmm ... also wonder if the MiniDSP has an internal high pass at 10hz or something along those lines given the sharp roll off right there, though it could just be my subs I guess. Will have to try using the DCX2496 with the same settings next ...
The measurements on DIYAudio did not show a rolloff at 10Hz with the MiniDSP.

Very nice job on the measurements.

Im in Mississauga Wed to Fri. Any chance of having a beer or two?

It is not "open-minded" to reject knowledge - Bob Lee
penngray is offline  
post #18 of 30 Old 01-03-2011, 10:27 AM
AVS Addicted Member
 
LTD02's Avatar
 
Join Date: Oct 2003
Posts: 15,897
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 109 Post(s)
Liked: 831
i don't understand why your waterfalls are so different from your single line frequency responses, are you averaging/smoothing?

Listen. It's All Good.
LTD02 is online now  
post #19 of 30 Old 01-03-2011, 10:34 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
Penn, will respond to your PM in a bit ...

LTD, smoothing the response at 1/3 octave. Without smoothing it's obviously a tad uglier ... . See attached if that helps better understand the waterfall graphs?
LL

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
post #20 of 30 Old 01-03-2011, 10:37 AM
AVS Addicted Member
 
penngray's Avatar
 
Join Date: Feb 2006
Location: Florida
Posts: 26,779
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 29
I think LTD is asking why the MiniDSP waterfall has more stored energy around and below 40Hz area then the DCX does.

I think its hard to compare them that way unless the SPL levels are almost identical between the products.

It is not "open-minded" to reject knowledge - Bob Lee
penngray is offline  
post #21 of 30 Old 01-03-2011, 10:56 AM
AVS Addicted Member
 
LTD02's Avatar
 
Join Date: Oct 2003
Posts: 15,897
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 109 Post(s)
Liked: 831
my concern was more in the 70-100hz region (the dcx plot looks pretty good, the minidsp plot not so much so).

Listen. It's All Good.
LTD02 is online now  
post #22 of 30 Old 01-03-2011, 10:58 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
Quote:
Originally Posted by penngray View Post

I think its hard to compare them that way unless the SPL levels are almost identical between the products.
Agreed, was mainly trying to see if the same roll off existed right at around 10hz, and was too much of a pain to get them matched.

The DCX may be put up for sale shortly...

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
post #23 of 30 Old 01-03-2011, 10:59 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
Quote:
Originally Posted by LTD02 View Post
my concern was more in the 70-100hz region (the dcx plot looks pretty good, the minidsp plot not so much so).
I don't fully understand how to read waterfall graphs, what are they showing in the 70 to 100hz area?

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
post #24 of 30 Old 01-03-2011, 11:02 AM
AVS Addicted Member
 
penngray's Avatar
 
Join Date: Feb 2006
Location: Florida
Posts: 26,779
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 29
Post #16 shows a great response to almost 10Hz.

Its a valid question about the 10Hz rolloff. I wonder if its the AV7005? It definitely looks like an electrical HP filter.

It is not "open-minded" to reject knowledge - Bob Lee
penngray is offline  
post #25 of 30 Old 01-03-2011, 11:08 AM
AVS Addicted Member
 
penngray's Avatar
 
Join Date: Feb 2006
Location: Florida
Posts: 26,779
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 29
Quote:
Originally Posted by LTD02 View Post
my concern was more in the 70-100hz region (the dcx plot looks pretty good, the minidsp plot not so much so).
I can not see much difference both have ripples and we never know what else is vibrating in the room at the time of the measurement. The only area is maybe that 90Hz hump.

It is not "open-minded" to reject knowledge - Bob Lee
penngray is offline  
post #26 of 30 Old 01-03-2011, 11:30 AM
AVS Addicted Member
 
LTD02's Avatar
 
Join Date: Oct 2003
Posts: 15,897
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 109 Post(s)
Liked: 831
stored energy shows up in the waterfall.

you want the waterfall to collapse to zero as fast as possible.

this one looks pretty good:



resonances will show up as spl peaks over time.

i was just asking what might be creating this resonance.


LL

Listen. It's All Good.
LTD02 is online now  
post #27 of 30 Old 01-03-2011, 11:34 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
Oh man, there is a ton of stuff in this room. My son's toys are in a bunch of Ikea containers, he has a thomas the train set in the middle of the room (acting as our coffee table which is in our unfinished basement), pictures on the mantle, you name it. I'm sure there are lots of things causing small vibrations.

Yeah, quite happy with the response down to almost 10hz. Was just curious if I could get a bit lower into the high single digits (think WinISD implied cone excursion would hit around 8hz but that was just for a single dual opposed AV15H with 1800 watts), and as you say it looks like some sort of limiter or filter given how steeply it suddenly rolls off. Maybe it is the 7005?

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
post #28 of 30 Old 01-03-2011, 11:35 AM - Thread Starter
pbc
AVS Special Member
 
pbc's Avatar
 
Join Date: Jul 2002
Location: Toronto, Canada
Posts: 5,332
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 30
Quote:
Originally Posted by LTD02 View Post
stored energy shows up in the waterfall.

you want the waterfall to collapse to zero as fast as possible.

this one looks pretty good:



resonances will show up as spl peaks over time.

i was just asking what might be creating this resonance.

Not sure, though that phenomena seems to disappear in the second one I posted in post 16. ... I think?

 

My DIY Subs ... http://www.avsforum.com/avs-vb/showthread.php?t=1233892

Quote:

J Dunlavy:.. if you stop to think about it, no loudspeaker can sound more accurate than it measures.

 

pbc is online now  
post #29 of 30 Old 01-03-2011, 11:36 AM
AVS Addicted Member
 
penngray's Avatar
 
Join Date: Feb 2006
Location: Florida
Posts: 26,779
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 29
Quote:
Originally Posted by LTD02 View Post
stored energy shows up in the waterfall.

you want the waterfall to collapse to zero as fast as possible.
Yes, what plot are you using? Im looking at post #16 to compare the waterfall plots. Look at the DCX vs MiniDSP in Post #16.

It is not "open-minded" to reject knowledge - Bob Lee
penngray is offline  
post #30 of 30 Old 01-03-2011, 11:39 AM
AVS Addicted Member
 
penngray's Avatar
 
Join Date: Feb 2006
Location: Florida
Posts: 26,779
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 29
Quote:
Originally Posted by pbc View Post
Not sure, though that phenomena seems to disappear in the second one I posted in post 16. ... I think?
Yep, that happens all the time with REW.

It depends on what you set your measurement parameters too.

I actually like using HOLM, ARTA for CSD measurements vs REW.

It is not "open-minded" to reject knowledge - Bob Lee
penngray is offline  
Reply DIY Speakers and Subs

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off