# Could use a Bit of Help with REW...



## Kevin A (May 14, 2009)

Hi everyone! I've just finished the building of my first DIY sub & now wanted to use (for the first time) the REW software. I've spent some time reading on the forum here and seen some of the issues (and successes!) folks have had using the REW. I've collected the necessary cable connectors, my audio soundcard, RS Spl meter, etc and begin the setup this morning. I've already run into some issues and am hoping the voices of experience here can help me resolve some of the early problems i've encountered.

My set up: I'm using a Mac (!) and a aware off some of the problems REW can have with the mac OS.
I'm using the M-Audio Mobile PRE USB and the Radio Shack SLM 33-2050. In the chain I've also inserted the BFM 1124— (currently in bypass) after my receiver & before the sub amp. 

The issue: not being able to have any control over the input levels when trying to calibrate either the SPL meter of the soundcard.

For example, I do get the tone coming the sub and it registers on thew VU meter in REW:









but I'm unable to alter either right or left levels. Here are my options to control input levels in my OS:
Via the Sound preferences pane:









Under the audio input section, sliders 1 & 2 have no impact. Slider one on the 'output' side does control volume/ouptut from the sub.

Or via the M-Audio control panel:









Moving the sliders has no effect in REW except for the 'Device Output' left channel which does control output from the sub. i've also switched back n' forth from 44 to 48000(Hz) in the 'format' box but it had no effect either.

I *strongly *suspect the problem lies in how i've made the connections & I'm using a stereo signal where i shouldnt...but I'm not sure. Here's where I could use some help. Here are two image of how I've made the current hook-up:

Front of the MobilePre:









Top view:









Any advice or comments would be greatly appreciated! Thanks in advance!

Kevin


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## Wayne A. Pflughaupt (Apr 13, 2006)

Kevin A said:


> I *strongly *suspect the problem lies in how i've made the connections & I'm using a stereo signal where i shouldnt...but I'm not sure. Here's where I could use some help. Here are two image of how I've made the current hook-up:


 Yeah, unfortunately your hook ups are all wrong. That soundcard is totally different from what you probably saw in the REW Connections thread. The only stereo signal it has is from the headphone jack, not the inputs and outputs. Lose all the adapters and use a couple of cables with RCA jacks on one end and 1/4” TS (mono) on the other. There might be other issues getting REW up and running, but let’s get the connections right first. :T

BTW, thanks for the pictures, made this much easier!

Regards,
Wayne


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## Kevin A (May 14, 2009)

Wayne A. Pflughaupt said:


> Yeah, unfortunately your hook ups are all wrong. That soundcard is totally different from what you probably saw in the REW Connections thread.


Thanks, Wayne. I thought there might be something squirrelly about my hook-up. :R



Wayne A. Pflughaupt said:


> The only stereo signal it has is from the headphone jack, not the inputs and outputs. Lose all the adapters and use a couple of cables with RCA jacks on one end and 1/4” TS (mono) on the other.


No RCA connections on this unit. There are two line inputs (channel 1 & 2), each 1/4" jacks with gain control knobs. There are also 1/4" outputs for each. There is also a Stereo mic input & an output (1/8" jacks). Also two female XLR jacks, one for each channel. So for my hookup, are you suggesting running my source (from the SPL meter) into channel 1 (1/4") & one leading out from the 1/4" channel 1 output?













Wayne A. Pflughaupt said:


> There might be other issues getting REW up and running, but let’s get the connections right first. :T
> 
> BTW, thanks for the pictures, made this much easier!
> 
> ...


I'm a visual guy—best for me to explain with pictures...


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## Wayne A. Pflughaupt (Apr 13, 2006)

Kevin A said:


> Kevin A said:
> 
> 
> > Wayne A. Pflughaupt said:
> ...


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## Kevin A (May 14, 2009)

Wayne A. Pflughaupt said:


> The RCA end of the cables are for the Radio Shack meter and your receiver’s input.
> 
> Regards,
> Wayne


Okay—so now I have the cable with the SPL meter out (a 1/8" jack) cable running to a a 1/4" input (Channel 1) and a 1/4" jack (channel 1 output) going to RCA end to my receiver.


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## Wayne A. Pflughaupt (Apr 13, 2006)

Your Radio Shack meter has a 1/8" output jack? :scratch:

Regards,
Wayne


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## Kevin A (May 14, 2009)

Wayne A. Pflughaupt said:


> Your Radio Shack meter has a 1/8" output jack? :scratch:
> 
> Regards,
> Wayne


My bad....RCA-connection for SPL meter! :dontknow:
Anyways, I've made the new connections but still getting no response from the 'audio input' controls.'
The unit gets the test signal fine from the usb connection, but the adjustment controls shown below have no effect. The gain control knobs on the unit do nothing either. Only the device output (test signal) can be varied. Very frustrating....:rant:


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## Kevin A (May 14, 2009)

Well after numerous attempts of trying to get my mobile pre to connect successfully with my mac/REW, I finally had breakthrough clap and got a reading which allowed me to control & adjust the left channel level. I wish I could say HOW I managed this as I've been through a series of procedures and many were hit & miss (changing record buffer levels, changing them back, rebooting REW, changing sample rates, etc). When I was successful, I was able to get a reasonable level as shown here:










However, in the end while trying to get the soundcard calibrated, I wound up getting results that always looked like this every time:










Feedback loop.
This has me stumped as my options are to mute the direct monitor in the USB setup, but that doesnt seem to effect my results....:hissyfit: 

Suggestions?


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## JohnM (Apr 11, 2006)

What kind of Mac do you have, Intel or PowerPC?


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## Kevin A (May 14, 2009)

JohnM said:


> What kind of Mac do you have, Intel or PowerPC?


G5...PowerPC.


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## JohnM (Apr 11, 2006)

REW V4 has a problem on PowerPC, the generated signal suffers from byte-swapped data which means you cannot use V4 to make measurements. The old V3.29 (available on the main REW page) works OK to measure on PowerPC, and the files saved in V3.29 can be opened in V4 for further analysis.


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## Kevin A (May 14, 2009)

JohnM said:


> REW V4 has a problem on PowerPC, the generated signal suffers from byte-swapped data which means you cannot use V4 to make measurements. The old V3.29 (available on the main REW page) works OK to measure on PowerPC, and the files saved in V3.29 can be opened in V4 for further analysis.


Okay, John, thank you for the information.

Here's what's available on the main page:

• Jar files for previous V3.29 version for Linux or Mac OS X platforms

Are these the files I should use? The only other mac version is the 4.11 & 4.0.

if so, I'll download the older version (V3.29) & give it a go.


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## JohnM (Apr 11, 2006)

Yes, use the jar files. There is a readme in the zip explaining what to do.


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## Kevin A (May 14, 2009)

:help:

Well I gave up trying REW on my mac and got my hands on a PC laptop running Vista.
I downloaded to the PC the appropriate driver for the MobilePre. Made the same connections as I did before:

• Input from RS SPL meter > *Channel 1 Inst/Line* of the MobilePre
• Output from MobliePre (*Channel 1 output*)> Receiver Aux
• USB connection from PC > *USB input* of MobilePre

Vista defaulted to the Microsoft sound driver so I had to manually link up the M-Audio (mobilePre) driver.
The audio control panel for the MobilePre is the same on vista as for Mac OS— which is 3 sets of sliders like this:









When I keep the Direct Monitor muted, I get no audio output from the sub. When it is not muted, the gain control on the mobilepre (channel 1) clips the sub output very easily! Very frustrating....I know I'm probably making errors _somewhere_ in my set-up chain, but I'm having difficulty in resolving it.

I'm having a of a time getting the levels indicated on the VU meters not to spike (clip) or get the left channel adjusted close to the output (far left) on the VU meter. On the output VU meter, there is about a 3dB difference between the yellow level & the red (clip?) limit. On MY left channel VU meter reading, that difference is more like 5-10dB. I can adjust the volume per the sliders shown above in conjunction with the GAIN control knob (shown below) from the channel 1 input on the MobilePre.I have to sometimes dial the Sweep Level down to about -20.0 dB (from the default 12dB) to keep the measurement from clipping.

When I do get a measurement that doesn't clip, I hit 'finish' & get the SAME type of looping results as before that look like this:










The corresponding results:
Sample Rate: 44100Hz (48 not an option on my MobilePre)
-3dB points: 999.6Hz, 1.005kHz
Input device: Line 1/2 (3-MobilePre)
Input: No input selected
Channel: Left
Input volume: no control
Input RMS target: -12.0dB
Actual RMS at 1kHz: -16.6dB
Output device: No output selected
Sweep Level: -12.0dB
20Hz..20kHz flatness: +50.9, -42.9dB

Any sage advice would be greatly appreciated! Thanks

Kevin


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## glaufman (Nov 25, 2007)

One thing I don't understand is that looking at the specs, M-Audio says this unit is capable of 48, so I would find the setting to change this, and try it both ways (making sure ot set REW so it agrees).

The manual indicates that this "Direct Monitor" is an analog feedback from input to output. This is very bad for the configuratoin we want to use. Leaving this on will create system feedback, and explains your clipping. I'm pretty sure you must mute this before you can get any meaningful measurements. From what you've written above, it sounds like your next task will be to figure out how to get the output you desire without this feature on, but I believe that is the first step towards a solution. 
Then, you say you have "no output selected"... what are your other options?


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## Kevin A (May 14, 2009)

Okay, good news...some breakthrough here... :R
I think I finally figured out the connections for soundcard calibration. Simply used this procedure I got from another thread dealing with MobilePre issues:

- Plugged in MobilePre into laptop, turned on the phantom power, turned the channel 1, 2 and headphones control knobs all the way down.
- started REW on laptop
- go into settings/soundcard
- sample rate set at 44.1kHz
- change output device and output to line 1/2 (MobilePre) with default output
- change input device and input to Line 1/2 (mobilePre) with default output (greyed box so it cant be changed)
- input channel set to left
- click on measure
- using guitar cable, plug one end into ch1 inst/line jack on front of mobilepre the other end into 1/L output jack on back
- click next
- change sweep level to -10 dB FS (other settings are wave vol is at 1, output vol is .01, replay buffer 32K, input vol .25, record buffer 32K) I also should note that the wave vol, output vol, and input vol are greyed out.
- click next
- Adjusted the input (center graph) to match the output (far left).

Here's the result I got:










Sample Rate: 48000Hz
-3dB points: 11.7Hz, 22.030kHz
Input device: Line 1/2 (3-MobilePre)
Input: No input selected
Channel: Left
Input volume: no control
Input RMS target: -10.0dB
Actual RMS at 1kHz: -10.2dB
Output device: No output selected
Sweep Level: -12.0dB
20Hz..20kHz flatness: +0.1, -1.2dB

After looking at countless graphs of feedback loops (!!), at least I feel like I can NOW actually do something with the REW. clap:


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## Kevin A (May 14, 2009)

Some initial measurements with the RS SPL in the prime listening position:

First one:









Recalibrated graph to be 45-105(V) & 15-200 (H) & multiple measurments:










Not exactly sure what to make of the results; roll off at about 21.4. 

Comments?


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## Wayne A. Pflughaupt (Apr 13, 2006)

Kevin A said:


> Some initial measurements with the RS SPL in the prime listening position:
> 
> Comments?


Yeah - let's see the graphs with a 45-105 dB vertical axis. :T

Regards,
Wayne


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## glaufman (Nov 25, 2007)

+1 on what Wayne said.
In addition, you said 44.1 in one place, and then 48 in another.
So, just to make sure, connect the loopback cable like you did to calibrate the soundcard, but run a measurement sweep to make sure it comes back flat.
Lastly, when you run a real measurement sweep, don't forget to load the RS cal file, and check "C weighted mic" under Settings->mic/meter.


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## Kevin A (May 14, 2009)

Wayne A. Pflughaupt said:


> Yeah - let's see the graphs with a 45-105 dB vertical axis. :T
> 
> Regards,
> Wayne


Okay, wayne...you asked for it! :R

Only difference was a slight increase in the output volume with each successive graph.




























glaufman said:


> +1 on what Wayne said. In addition, you said 44.1 in one place, and then 48 in another. So, just to make sure, connect the loopback cable like you did to calibrate the soundcard, but run a measurement sweep to make sure it comes back flat. Lastly, when you run a real measurement sweep, don't forget to load the RS cal file, and check "C weighted mic" under Settings->mic/meter.


Greg, i started with 44.1 initially as it wouldnt allow me to select 48. after rebooting it became enabled & thus I switched it over to 48. I'm starting to get the hang of the calibration process (loopback cable,etc). I do make sure that the RS cal file is loaded and C weighted. I did save the soundcard cal file & loaded that again before these measurements were taken. Thanks for all the helpful advice. I need it!


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## glaufman (Nov 25, 2007)

Yup. I see that now in these graphs. It wasn't showing in the previous ones. I just wanted to make sure you weren't mixing/matching between soundcard and REW settings.

Now, you have an 80hz xover in your AVR? And 80HZ target line with REW?


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## Kevin A (May 14, 2009)

glaufman said:


> Now, you have an 80hz xover in your AVR? And 80HZ target line with REW?


AVR is set at an 80 xover. I didnt change any of the default settings in REW. 
The Target settings were * Cutoff* 80Hz, *Target Level: * 75Hz (!) So I guess I need to bring that up to 80 as well?


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## Wayne A. Pflughaupt (Apr 13, 2006)

If those are unequalized and unsmoothed graphs, your response is amazingly good! :T

Regards,
Wayne


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## glaufman (Nov 25, 2007)

Looks to me like you may be rolling off a bit steep. I'd say it's time to look at the mains and how well they integrate.


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## Kevin A (May 14, 2009)

Wayne A. Pflughaupt said:


> If those are unequalized and unsmoothed graphs, your response is amazingly good! :T
> 
> Regards,
> Wayne


Unless there's equalization or smoothing that is set by default, I didnt apply do anything beyond follow the basic REW steps for taking the initial measurements. I have a BFD1124 in the chain (in bypass mode) that i was going to put to use if needed. Gotta figure that one out next. :sweat:



glaufman said:


> Looks to me like you may be rolling off a bit steep. I'd say it's time to look at the mains and how well they integrate.


Okay, that the next step. My plan was to do the sub first, then the mains & see the results. After completing those measurements, I was going to try some with a different mic. I have an ECM8000 that i was also gong to use to do some measurements. Good idea? Advantages of using it versus the RS spl? I know it has a broader range which should come in handy in doing the mains.


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## glaufman (Nov 25, 2007)

Well, on the video side of things we often say "I man with a meter knows he's achieved a perfect calibration, a man with 2 meters is never quite sure..."
Theoretically, the RS should be fine even for the mains in this frequency range. It's above 3kHz where the RS becomes really squirrelly, and up there you won't be applying EQ for narrow peaks and dips like you would in the bass region, only very, very broad filters, if any.
If by chance you had a custom created cal file for that ECM, then there would be an advantage. In the absence of custom created cal files for both mics, I can almost guarantee they will show slightly different results. Then we'll have to talk you in off the ledge :foottap:
Sure, go ahead, let's see what you get...:whistling:


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## Kevin A (May 14, 2009)

glaufman said:


> In the absence of custom created cal files for both mics, I can almost guarantee they will show slightly different results. Then we'll have to talk you in off the ledge :foottap:
> Sure, go ahead, let's see what you get...:whistling:


Okay, good to know. I'll do the complete measurements of both sub & mains & get 'em to where I want them to be with some EQ (hopefully). Then I'll try the ECM just for kicks....:nerd:


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## glaufman (Nov 25, 2007)

Yeah, I'm not sure I'd be able to resist either... but I do everything with an ECM...


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## Kevin A (May 14, 2009)

--


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## Kevin A (May 14, 2009)

Some new graphs from some measurements taken this morning:

*Sub only*—no smoothing nor filters applied:









Sub: "Find Peaks" & "Assign Filters":









Sub: "Optimise PK Gain & Q":









For this graph, under EQ Filters, it gave me a list of six filters (all auto):

1. PA 25.98 (freq) -10 (gain) 4 (BW/60) 2.5Hz
2. PA 21.50 (freq) -15 (gain) 7 (BW/60) 3.5Hz
3. PA 32.78 (freq) -12 (gain) 12 (BW/60) 9.3Hz
4. PA 39.58 (freq) -6 (gain) 14 (BW/60) 13.2Hz
5. PA 50.00 (freq) -4 (gain) 5 (BW/60) 5.9Hz
6. PA 59.10 (freq) -6 (gain) 11 (BW/60) 15Hz

I entered these figures manually into the BFD1124.

Tests with the *MAINS*:










Mains: "Assign Filter"









Mains: "Optimise PK Gain & Q":









For this graph, under EQ Filters, it gave me a list of four filters (all auto):
1. PA 25.98 (freq) *-12* (gain) 14 (BW/60) 2.5Hz
2. PA *22.00* (freq) *-10* (gain) *12* (BW/60) 3.5Hz
3. PA 32.78 (freq) -12 (gain) *9* (BW/60) 9.3Hz
4. PA *59.75* (freq) *-7* (gain) *5* (BW/60) 13.2Hz


Mains/sub (no filter)









Mains/Sub with filters entered into BFD1124:









Sub Alone (no filtering):









Sub (with BFD filters applied)









Any information/feedback regarding these graphs would be appreciated. I think they're looking okay— but I'm no expert.....


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## glaufman (Nov 25, 2007)

I'm confused, you entered all those filter into the BFD? I'm no expert here, but I think that's a lot of filtering. I'd rather see you have REW reset the target curve based on your measurement and start over.


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## Kevin A (May 14, 2009)

glaufman said:


> I'm confused, you entered all those filter into the BFD? I'm no expert here, but I think that's a lot of filtering. I'd rather see you have REW reset the target curve based on your measurement and start over.


I can do that.. if I'm understanding what you're saying.
Rather than apply any filtering, you're saying I should go ahead & reset (the target curve— target settings?) & let REW doe its measurements again?


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## Kevin A (May 14, 2009)

glaufman said:


> I'm confused, you entered all those filter into the BFD?


Just the first set of six filters.


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## JohnM (Apr 11, 2006)

The target level you are giving REW is much too low, it is applying filters to try and pull the response down to the 75dB target you have set it. The response is even enough that it likely doesn't need any filters, but the LF looks much too high compared to the rest of the range from the traces with mains included. A response that goes out further (to 1k or more) would give a better picture of the relative levels of sub and mains, but from what has been shown so far the sub can come down quite a bit.


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## glaufman (Nov 25, 2007)

Kevin A said:


> I can do that.. if I'm understanding what you're saying.
> Rather than apply any filtering, you're saying I should go ahead & reset (the target curve— target settings?) & let REW doe its measurements again?


Like John said, the measurements REW made are fine, what's off, based on those measurements, is the target line REW is suggesting EQs for... so re-set the target line to a more appropriate level, then let REW suggest filters based on that...


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## glaufman (Nov 25, 2007)

OK, maybe that's not quite what John said, but you probably get the idea...


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## Wayne A. Pflughaupt (Apr 13, 2006)

What John and Greg said. With the response curve riding so high above the Target, equalizing merely ends up being a gain-reduction exercise. This is poor use for an equalizer. Other methods are better suited for adjusting gain – the receiver’s volume control, the sub’s own gain controls, for instance. 

Alternately, using the options under the “Target Settings” button (left side of the screen) you can manually raise the Target before running the “Find Peaks” routine (based on your graph, 90-91 dB looks about right). Or, the “Set Target Level” function will do it for you...

Regards,
Wayne


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## Kevin A (May 14, 2009)

Excellent feedback & information, gentlemen! Thank you! :clap:

This really helps me in understanding what exactly I'm trying to accomplish with REW — 'cuz right now i'm just going through the paces per the instructions without really having a real handle on what i'm actually doing! :R

I'll be doing some more measurements later this week based upon your suggestions & will post them...

....with probably some more questions.


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## glaufman (Nov 25, 2007)

That's what we're here for! :T


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## Kevin A (May 14, 2009)

Some more tests....

One note: when I attempt to "Set Target Level" I get a window stating, "The SPL Meter is reading 64dB. This is higher than it should be with no signal present." I then get a target level of 84.1dB.
Im' not sure what to do about the higher spl reading "when no signal is present" as the room is quite quiet (no music, fans, etc).


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## Kevin A (May 14, 2009)

Same graph, after finding peaks, assigning filters:









Optimize PK Gain & Q:









I'm beginning to think I'm going around in circles here & I've missed something critical in the set-up...

Are my volume levels still too loud? I'm calibrating the sub test tone @ 75dB with the spl...but my target level comes out higher. normal?
Any help or clarification would be appreciated.


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## laser188139 (Sep 19, 2009)

If you want to use the equalization to smooth variation in the primary output region of the sub, then, yes, it looks as if the volume level is too high. Right now, the filters are trying to act as a volume control to reduce the whole range below 50Hz, and they don't do this well. 

The real problem is the overly steep rolloff at the high end. You've already responded to the question about the crossover setting at the AVR, that it is set at 80Hz. As the rolloff is clearly sharper than 24dB/octave, this makes me think there is still a crossover/low-pass-filter enabled at the sub. The combined slopes appear to be about 48dB/octave. Can you turn this off, or raise it so high it does not interfere with the equalization? Or does your sub, itself, just have a very sharp rolloff in its performance above 60Hz?

Otherwise, you are stuck with your first choice. Lower the overall volume. Equalize to there. Then level set the sub to the mains using REW, such that the sub curve is relatively even with each main curve measured separately. (Some SPL meters are not as accurate in the low range as higher up, so REW should give you a better answer. But if you use the REW sub calibration signals to set the sub level, be aware that its spectrum runs up to 80Hz. With your steep rolloff, it's SPL meter will read lower than 75dB when the response is level, because the upper part of its spectrum is being reduced.)

Bill


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## Kevin A (May 14, 2009)

laser188139 said:


> As the rolloff is clearly sharper than 24dB/octave, this makes me think there is still a crossover/low-pass-filter enabled at the sub. The combined slopes appear to be about 48dB/octave. Can you turn this off, or raise it so high it does not interfere with the equalization? Or does your sub, itself, just have a very sharp rolloff in its performance above 60Hz?
> 
> Bill


Hi Bill. 
I need to check a few things: The way the sub is hooked up is as follows:

AVR > BFD (in by-pass) >Bash SubAmp >THT Sub

There arent any filter controls on the sub amp (just the phase, volume, freq dials), so I'll going to see if I possibly have some filtering in the AVR output.

Regarding the performance above the 60Hz rolloff, one of the things I liked about the THT sub was it's broad range down to 20hz, but I havent done testing myself.


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## laser188139 (Sep 19, 2009)

It really looks as if there is a built-in low-pass-filter in your BASH amp. At least, I find that the simplest explanation. 

One thing I have done to try to measure the sub system alone is to raise the crossover in the receiver to its highest value, 250Hz in my Denon, and then measure the response curve of the sub alone up to 200Hz. If you see a rolloff similar to the target curve, you know there is a filter after the AVR, especially given the claimed response curve of the THT itself. 

Good luck,
Bill


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## Kevin A (May 14, 2009)

laser188139 said:


> It really looks as if there is a built-in low-pass-filter in your BASH amp. At least, I find that the simplest explanation.


not according to the amp's specs. I can control the low-pass crossover frequency (from 50 to 150Hz) on the amp. its currently set at 50 (the default setting). 




laser188139 said:


> One thing I have done to try to measure the sub system alone is to raise the crossover in the receiver to its highest value, 250Hz in my Denon, and then measure the response curve of the sub alone up to 200Hz. If you see a rolloff similar to the target curve, you know there is a filter after the AVR, especially given the claimed response curve of the THT itself.
> 
> Good luck,
> Bill


I just set it to 180Hz (max) on my AVR & will give it a test. thanks!


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## Kevin A (May 14, 2009)

Did a minor volume adjustment; changed the avr crossover to the max:


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## laser188139 (Sep 19, 2009)

Kevin A said:


> not according to the amp's specs. I can control the low-pass crossover frequency (from 50 to 150Hz) on the amp. its currently set at 50 (the default setting). ...


The curve you just posted looks much like one would expect from a low-pass-filter at 50Hz. You write that you can raise this to 150Hz on the amp. This is the sub's amp, right? What happens if you raise it to its max? You can try raising this to its max, while leaving the AVR crossover at its highest value and see what the response is. My guess is that, for your endpoint, you want to set it at its max, then lower the AVR's crossover and let it be responsible for both the low-pass-filter on content to the sub and the high-pass-filter on the content to the mains.


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## Kevin A (May 14, 2009)

laser188139 said:


> The curve you just posted looks much like one would expect from a low-pass-filter at 50Hz. You write that you can raise this to 150Hz on the amp. This is the sub's amp, right?


 Yes, the sub amp.



laser188139 said:


> What happens if you raise it to its max? You can try raising this to its max, while leaving the AVR crossover at its highest value and see what the response is. My guess is that, for your endpoint, you want to set it at its max, then lower the AVR's crossover and let it be responsible for both the low-pass-filter on content to the sub and the high-pass-filter on the content to the mains.


That's what Ill try next (raise the sub amp to 150 & return the AVR back to 80hz & post the results in a bit. Thanks!

Kevin


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## Kevin A (May 14, 2009)

Here's a new measurement taken after I changed the lo-pass filter on the sub amp to 150hz & set the avr back to it's original 80hz:










compared to the previous graph with the subamp at its original lo-pass filter of 50:


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## Kevin A (May 14, 2009)

One of the more frustrating aspects I've experienced with REW is getting the SPL meter calibrated for taking measurements. I've followed this sequence:

* Under Settings: Mic/Meter> Calibration > Calibrate SPL> Adjusted the figure in the box to match the reading on the SPL meter...I adjust the AVR volume so it reads about 75dB. Hit 'Finished.' Note: on the VU meter, both the left & middle columns are near identical, with the Out maxing at -0.8 and the Left at -3.5.

*Under Levels (Soundcard) > Check Levels > adjust the gain on the soundcard (mobilepre) so the input volume is between -12 & -24db. Done!

*Under 'Measurements' > Check Levels > adjust the input levels so they are not too high or low

* Take a Measurement

* Set Target Levels >Establishing target level > I get a window saying my SPL reading HIGHER than it should be (approx 63-73db) with NO signal. When I decrease the input signal (the SPL reading drops when I decrease this), the levels are now too low to take measurements....
So I'm kind of stuck.....unless i'm doing things out of sequence.


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## laser188139 (Sep 19, 2009)

Cool. Obviously, above 150Hz, it drops off a cliff. But now you should be able to drop the volume to where the target line is in the middle of the curve from, say, 100Hz on down. (Or you can use the curve you have, just adjust the target upwards to center it on the actual curves.) Then use REW to calculate the filters to smooth the response there. This should be straightforward, now. 

Good luck,
Bill


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## laser188139 (Sep 19, 2009)

Kevin A said:


> One of the more frustrating aspects I've experienced with REW is getting the SPL meter calibrated for taking measurements. I've followed this sequence:
> 
> * Under Settings: Mic/Meter> Calibration > Calibrate SPL> Adjusted the figure in the box to match the reading on the SPL meter...I adjust the AVR volume so it reads about 75dB. Hit 'Finished.' Note: on the VU meter, both the left & middle columns are near identical, with the Out maxing at -0.8 and the Left at -3.5.
> 
> ...


You don't have to use the Set Target Level feature. I've always followed the sequence in the Helpfile. 
Use Settings -> Check Levels to make sure that the output and input gains are reasonable. 
Do the SPL Calibration step to set the absolute levels. Adjust the AVR so the volume reads 75.0dB on the SPL meter, then calibrate that as the measured level. Hopefully the levels are still reasonable and don't clip. 
Then I can take all the measurements I like for the rest of the session. 

If you calibrate the main level to 75dB using REW's main speaker calibration level, you can certainly use the REW SPL meter to verify the SPL level of the sub using REW's sub calibration level, and adjust the sub gain or AVR sub trim to level match with a single main. 

Bill


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## JohnM (Apr 11, 2006)

Kevin A said:


> One of the more frustrating aspects I've experienced with REW is getting the SPL meter calibrated for taking measurements. I've followed this sequence:
> 
> * Under Settings: Mic/Meter> Calibration > Calibrate SPL> Adjusted the figure in the box to match the reading on the SPL meter...I adjust the AVR volume so it reads about 75dB. Hit 'Finished.' Note: on the VU meter, both the left & middle columns are near identical, with the Out maxing at -0.8 and the Left at -3.5.
> 
> ...


You have to do the SPL Meter calibration _after_ completing all level adjustments, as changing the input level will invalidate the meter calibration. Generally speaking setting the levels is something you only need to redo if you are measuring at a very different position from wher the initial levels check was done, much closer to or further from the speaker/sub which leaves the input too high or too low.


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## Kevin A (May 14, 2009)

John & Bill

thanks for the helpful info!
I'm going to play around with it some more & see if I can get more 'tweaking' done to smooth out some of the rough spots.


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## Kevin A (May 14, 2009)

I'm getting comfortable with using REW—especially now that i've overcome the soundcard/mic issues and the results I've been getting are pretty consistent. One thing I did discover in the process was a system-wide 60hz hum that I did not detect until I cranked up the low-pass sub amp filter from 50 to 150hz. Source: the Comcast cable. Probably why I had a floor noise level of around 72dB (!!) before I resolved the hum issue.

*Some Quick Questions*: So I've been doing measurements primarily on my *subwoofer* while trying to get a good understanding of what REW is telling me about my room. I want to also incorporate REW measurements of how my *stereo/HT mains* interact with the sub, and/or how they interact in the room.


*Is there a standard operating procedure I should follow for doing this?*

• measure sub alone (using sub test tones)— I_'ve been doing that_
• *measure mains together (using speaker "full range?" tone) alone or with sub?*
• *measure mains independently with or without sub?*

If I do take measurements with all 3 (sub & mains), *do I apply filters for all or is it best to do the sub separately?*

Any tips or suggestions would be appreciated.


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## glaufman (Nov 25, 2007)

Generally, the more detail you get the better you can figure out what's going on and how to fix it.
Definitely scan the sub alone, with whatever xover you'll be using in practice engaged.
Definitely scan the mains without the sub, sometimes it's ok to do these together, sometimes it's necessary to separate them to troubleshoot phase and SBIR interactions. Again make sure the xover is engaged.
Scan the sub with the mains to see how they interact.
How to EQ will depend on how you're EQing If you use a BFD, generally you EQ the sub alone. If you're using Audessey and the like, or more sophisticated EQ, you can EQ the mains as well, but...
Generally speaking, and especially above the bass/modal regions, EQ should be broader generally speaking, you're not out to smooth out every ripple and certainly not comb filtering.


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## porksoda (Feb 25, 2010)

Kevin A said:


> I'm getting comfortable with using REW—especially now that i've overcome the soundcard/mic issues and the results I've been getting are pretty consistent. One thing I did discover in the process was a system-wide 60hz hum that I did not detect until I cranked up the low-pass sub amp filter from 50 to 150hz. Source: the Comcast cable. Probably why I had a floor noise level of around 72dB (!!) before I resolved the hum issue.
> 
> *Some Quick Questions*: So I've been doing measurements primarily on my *subwoofer* while trying to get a good understanding of what REW is telling me about my room. I want to also incorporate REW measurements of how my *stereo/HT mains* interact with the sub, and/or how they interact in the room.
> 
> ...


kevin,

As i have recently set up rew and did some eq'ing i will just tell you how i went ahead and did these ... i mean i have over 100 charts as i experimented with rew, location, phase, xover and all... so this is what i did for my final setup.

- On my avr i set whatever xover i wanted to and set my speakers as small as i will leave them as small after the calibration.
- I ran sub alone 0-200hz sweep
- I ran main only 0-200hz sweep

- you can go to avg and see how they fit in to give you an idea when you run the together sweep on how it shows up.

- At this point i set up my eq for bfd and set it ran the sweep to confirm to what level it did eq.

- Connected the fronts and sub and ran the eq and compared to my corrected sub + main together.

- See if i need any other tweaking with the bfd as when mains and sub were measured directly on the roll off a lot of eq'in gets overlapp by the rolloff of the mains.


If i were to redo my eq at this point i know what my room "looks like" in rew for various curves so i open up a curve do a baseline sweep and apply eq (again sub only) then confirm it by resweeping with main + sub.

I have also gone ahead and done a lot of sweeps with both l and r also with the sweep alongside sub.

I would say just play with it until you get comfortable with the software when i started off just couple of weeks ago it was like learning to walk... but i can comfortably operate rew and the built in features like the various curves, eq applet and other options.

Great software.


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## Kevin A (May 14, 2009)

Great input, guys, thanks.
I'll take your suggestions (& examples) and see what I can come up with in terms of separate sweep measurements, see the interaction & go from there.:T


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## Wayne A. Pflughaupt (Apr 13, 2006)

Adding a bit to what the others have said, if you have the means to EQ your mains, run separate readings of them, and EQ as needed (we can give you help with that endeavor, if you need). To see how the mains blend with the sub(s), run separate sub-only and mains-only scans (both mains, this time). Then run a combined scan with both the mains and the sub(s). Reviewing the results you can see if combined response shows new anomalies (due to phase) in the crossover region (which spans an octave above and below the crossover frequency), compared to the separate readings. If that’s the case, you may well be able to use the EQ to address the new response anomalies.

Regards,
Wayne


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## Kevin A (May 14, 2009)

Wayne A. Pflughaupt said:


> ...if you have the means to EQ your mains, run separate readings of them, and EQ as needed (we can give you help with that endeavor, if you need).


Well, I have a couple of possible EQ options—but i'm not sure either offers optimum EQing.
The first is through my AVR: a 9-band graphic equalizer for each of the seven channels. I can select the target frequency on this graph and channel (i.e., Left front & right front) & adjust to any level between -20 and +9 dB in 0.5dB increments.

Marantz SR8001 EQ screen:









The second is to introduce my old Audiosource EQ-One, a 20-Band Graphic Equalizer (10 Bands each side) into the chain...










Receiver > *EQ-One* > Amp > Mains

Not sure either is ideal. Opinions?



Wayne A. Pflughaupt said:


> To see how the mains blend with the sub(s), run separate sub-only and mains-only scans (both mains, this time). Then run a combined scan with both the mains and the sub(s). Reviewing the results you can see if combined response shows new anomalies (due to phase) in the crossover region (which spans an octave above and below the crossover frequency), compared to the separate readings. If that’s the case, you may well be able to use the EQ to address the new response anomalies.
> 
> Regards,
> Wayne


Okay. sounds like a good plan of attack, Wayne. Thanks.


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## glaufman (Nov 25, 2007)

porksoda said:


> - you can go to avg and see how they fit in to give you an idea when you run the together sweep on how it shows up.


As a side note, averaging the mains and sub scans won't give you an accurate insight into how they blend. 
When they combine in the real world, as in a scan containing both, the SPL reading at any given frequency will, barring phase issues, track the SPL of the louder device, as opposed to averaging mathematically where the lower SPL device will detract from the SPL of the louder device.

When overlapping 2 subs, as a for instance, when after combining them you may turn down the overall level to achieve the same SPL calibration (if you adjust each sub to 75dB, then combine them and re-adjust the overall level for 75dB, i.e. normalizing it) will averaging give a somewhat real perspective into the result.


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## porksoda (Feb 25, 2010)

glaufman said:


> As a side note, averaging the mains and sub scans won't give you an accurate insight into how they blend.
> When they combine in the real world, as in a scan containing both, the SPL reading at any given frequency will, barring phase issues, track the SPL of the louder device, as opposed to averaging mathematically where the lower SPL device will detract from the SPL of the louder device.
> 
> When overlapping 2 subs, as a for instance, when after combining them you may turn down the overall level to achieve the same SPL calibration (if you adjust each sub to 75dB, then combine them and re-adjust the overall level for 75dB, i.e. normalizing it) will averaging give a somewhat real perspective into the result.


nods.

My wording is a bit misleading... what i meant was go to the avg'ing window to see how the sub + mains should be as a way of seeing predicted response and when you get the full reading you know if any adjustments are to be made. In my case when i first started to do sweeps i had some phase related dips... which were non existent in my separate sub/main sweeps.


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## Wayne A. Pflughaupt (Apr 13, 2006)

> Not sure either is ideal. Opinions?


I'd go with the one in the receiver. They're both essentially the same - One-octave equalizers. They're better suited as a sophisticated tone controls (think bass / midrange / treble, but with more options) than correcting speaker response. They're so broad that often you'll end up "adjusting" areas beyond the problem area, that don't need adjusting. Still, you could try it using REW's RTA feature, maybe it could do some good.

Regards,
Wayne


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## Kevin A (May 14, 2009)

Here's another attempt at taking some measurements per the suggestions made in earlier posts (sub alone, mains alone, sub & mains together. I'm still not overly confident I did everything properly, but here goes:
* All measurements taken with ECM 8000, pointed vertically. All taken form the same listening position (approx 7' from sub, 12' from mains).

First, the sub alone:









Then the Mains, alone:









Mains & Sub together:









All three measurements shown together:









So as I read these graphs, I'm seeing that my mains & subs arent intersecting until around 100Hz. My crossover is set at 80 so am I correct in assuming that I should raise the Xover? I've a big sub null at 80 as the sub starts rolling off at around 60...
Any advice? thanks...


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## laser188139 (Sep 19, 2009)

I think you are seeing artifacts of the sub level being set so much higher than the level of the mains. With the crossover at 80Hz, you would expect to see the sub intersect each main measured separately near 80Hz. In your case, the sub trim or gain appears to be set about 10dB higher than the mains. Naturally, as you translate the sub curve upwards, the intersection point will move to the right. 

If you raise the crossover in your receiver, your observed crossover in REW will rise as well. Try it if you like; you learn a lot by experimenting. As a what-if scenario, you can also within REW adjust the trace offset downwards in the Trace Adjustments for the sub curve, viewing it and your main alone together, and see how the crossover frequency changes. 

What is really fascinating is how much interference you have between the sub and the mains around 110Hz and 150Hz. It is natural that there will be some frequencies where the two add together and some where the sub subtracts. But another artifact of the sub level being so much higher than the main is that, where its interference is destructive, it subtracts so much more from the main level. 

Your curves may be misleading me, though. Did you recalibrate the level between taking the measurements? You would expect the main alone and the main+sub curves to overlay each other above, say, 200Hz. Here, your main+sub curve is significantly lower. As if you adjusted the levels to make the curves match in the sub range, and this would exaggerate the apparent dips in the combined curve. 

Personally, I would drop the sub level to be more even with the main. The best way to do this is to measure the sub and just one main, left or right, so you are not seeing destructive interference between the mains in the curve. You can also play with the polarity/phase setting on the sub to see if the overall curve with the main is better at a different setting.

Bill


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## Kevin A (May 14, 2009)

laser188139 said:


> ... I would drop the sub level to be more even with the main. The best way to do this is to measure the sub and just one main, left or right, so you are not seeing destructive interference between the mains in the curve. You can also play with the polarity/phase setting on the sub to see if the overall curve with the main is better at a different setting.
> 
> Bill


Thanks, Bill.

Here's some updated graphs with the levels a bit closer. The xover is still set at 80.

Sub Alone:










Mains:








sub & Mains Together:










All measurements (sub-purple; mains-green, together-gold): 










One question regarding Setting/checking levels— for subs, I understand using the sub signal/tone, for mains, the Main speaker signal/tone—but when I'm testing all 3 together, should I be using the 'main speaker' pink noise tone or the sub tone? If I choose sub tone, the output signal is much louder than if I choose the main speaker signal.

Under *Target Settings*, for speaker type, sub=sub, but for my mains I can select either 'Bass Limited' or 'Full range'—which is preferred? My mains are magnepans (45-22kHz ±3dB). When I test all 3 together, which 'speaker type' should i select? or does it really matter?


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## laser188139 (Sep 19, 2009)

On your graphs, your gold graph, that should be mains+sub, looks almost identical to the sub graph alone. Any idea what is happening there? Were the mains really playing? I am having a hard time guessing what would explain that curve. The question is whether this a measurement issue, or a real issue with the connection. 

I suppose it could be a measurement issue. Something to do with the Magnapans? Do the measurements come out the same with the mic oriented horizontally, using the horizontal calibration file? 

But you write that there is a big difference between the two calibration signals. A small difference, e.g., 6dB, could be attributable to the two mains interfering with each other, where this does not happen when the two signals are combined in a single sub. And, obviously as I raised above, difference in the sub/main trim levels would cause the sub level to be elevated. But neither explains the big difference you see in your graphs. 

In another thread, someone had a huge slope downward from the bass range to the mains and treble just in the soundcard calibration. This seems to be an incompatibility between his soundcard (M-Audio Mobile Pre) and his OS (Windows XP Media Center Edition). But in your filter graphs, I don't see any evidence of weird features in your soundcard or mic calibration files. Are you using the generic ECM8000 calibration file available here on the HTS site? Or are you using an individually calibrate file you obtained with the mic? 

Do you have some unusual surround mode selected on your receiver? Something that might split the two channel test signal over five surround speakers, and then you unplugged the cables from the surround speakers so they would not contribute? Do you think you have configured some unusual bass/treble trim or sub level in the receiver's stereo only settings, that might be affecting the 2 channel signal from REW but not your normal multichannel listening? That gold curve is hard to explain. 

On your general questions, for mains alone you can specify a target curve that is bass limited, with the crossover setting you configured in the receiver. For calibrating levels, an SPL meter has some problems getting a stable number on the sub pink noise, so I find it slightly more accurate to calibrate using the main speaker band limited pink noise to 75dB, then trust REW to calculate the SPL correctly in the sub range. But this does not explain the large differences you are measuring and seem to be hearing. 

It's a puzzle,
Bill


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## Kevin A (May 14, 2009)

laser188139 said:


> On your graphs, your gold graph, that should be mains+sub, looks almost identical to the sub graph alone. Any idea what is happening there?


Not sure, but when I play all 3 together (two mains & sub), the sub/LF seems to be SO dominant in the results.



laser188139 said:


> Were the mains really playing? I am having a hard time guessing what would explain that curve. The question is whether this a measurement issue, or a real issue with the connection.


 Yes.



laser188139 said:


> I suppose it could be a measurement issue. Something to do with the Magnapans? Do the measurements come out the same with the mic oriented horizontally, using the horizontal calibration file?


 I've not made any measurements with the horiz. mic placement.



laser188139 said:


> Are you using the generic ECM8000 calibration file available here on the HTS site? Or are you using an individually calibrate file you obtained with the mic?


 the cal file from the site for the ECM8000. 



laser188139 said:


> Do you have some unusual surround mode selected on your receiver?


Set for 'Stereo'

To try and resolve this issue, should I narrow it down a bit: maybe test the mains independently to see how each interacts in the room first? If so, what is the ideal mic placement for this procedure? horizontal aimed at each speaker? distance?




laser188139 said:


> It's a puzzle,
> Bill


Indeed.......:hissyfit:


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## laser188139 (Sep 19, 2009)

Kevin A said:


> ... the cal file from the site for the ECM8000. ...


If you are using the cal file from the HTS site, then vertical, or 10 degrees off vertical is fine. Your individual mic may be slightly different from the calibration file, but not so much as to be material, and certainly not enough to explain your symptoms. 



Kevin A said:


> Not sure, but when I play all 3 together (two mains & sub), the sub/LF seems to be SO dominant in the results. ...


Is it possible that your sub is really set 20dB louder than the mains? Does your receiver have an automated system for setting distances and levels? What did it calculate for the trim settings on the main and the sub? 

I expect the receiver has test tones for verify the sub and main levels. When you measure these manually with your SPL meter, without REW in the system, do they measure level? Or does the sub still come out much louder? 

Bill


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## Kevin A (May 14, 2009)

laser188139 said:


> Is it possible that your sub is really set 20dB louder than the mains? Does your receiver have an automated system for setting distances and levels? What did it calculate for the trim settings on the main and the sub?
> 
> I expect the receiver has test tones for verify the sub and main levels. When you measure these manually with your SPL meter, without REW in the system, do they measure level? Or does the sub still come out much louder?
> 
> Bill


Well, now we're onto something!
My AVR does have an automated system for setting distance and levels.
I went back & checked them.
Distances:
LF: 12.7' • RF:12.9' • sub: 7.5'

Levels:
(@ 75dB) Left Front: *+6.5*
(@ 75dB) Right Front: *+8.5* (for some reason, my RF speaker isnt as loud)

*HOWEVER* my sub was set at : +0 and reading *92db*! 
Yikes! I dropped the gain significantly on the sub amp and adjusted the AVR level so it reads:
(@76-78db) sub: *-8.0*

I'm such a doofus....
:dumbcrazy:
Time for some new tests....


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## Kevin A (May 14, 2009)

Okay, now that I've the levels taken care of with the AVR blink, some new measurements:

Sub, alone:









Mains, alone:










Sub & Mains, together:










Three sweeps, together:


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## laser188139 (Sep 19, 2009)

Doesn't that look much more reasonable!


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## Kevin A (May 14, 2009)

Absolutely!
So where to from here? 
I'm looking at some filters to help smooth out the sub. Find Peaks (20-80Hz) & the suggested filters are these: (Freq: 34.05 (-3 gain, 4BW); 74.05 (-2 gain, 3BW) that I can input manually into the BFD.

Here's the graph with the above filters:


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## glaufman (Nov 25, 2007)

Kevin A said:


> So where to from here?


Relax and enjoy some content for a while... you've had a long day...  Then you can get into making this better some other time....

Nice work Bill!


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## Kevin A (May 14, 2009)

glaufman said:


> Relax and enjoy some content for a while... you've had a long day...  Then you can get into making this better some ther time....
> 
> Nice work Bill!


Ha!
Greg, I think I will take a break & appreciate listening to the system for a while. After banging my head against the wall for the past few weeks trying to balance out a system that was totally out of whack—it does feel good to just to NOTHING...

It DOES sound better without the lower end being so dominant! :R

Thanks, Bill!
:clap:


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## laser188139 (Sep 19, 2009)

Kevin, now that the levels are even, the sub curve itself looks so flat to start with that I'm not sure applying the filters will help a lot. If you have the BFD, you can try them. But I would take Greg's suggestion and spend some time listening first. 

I'm glad to have been able to help,
Bill


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## Kevin A (May 14, 2009)

laser188139 said:


> Kevin, now that the levels are even, the sub curve itself looks so flat to start with that I'm not sure applying the filters will help a lot. *If you have the BFD, you can try them.*


What good is having a toy (*BFD*) and not being able to play with it? :bigsmile:
I'll apply the two minor filters & give it a good listen.
Thanks!:T


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