# My second attempt at measurements



## thewire (Jun 28, 2007)

I used my new external USB sound card and I want to be sure this was done correctly. I used the right CD input on my AVR from my right line output of the card. First I calibrated my subwoofer volume on the back of it to 80dB in REW. Then I raised the volume of my AVR until it said 75dB while playing the SPL calculation for testing with my mains. The output level in Windows XP was at the max setting for input and output using the Creative Surround Mixer window. It was set to stereo and there were no equalizers or effects on by default. I used a Radioshack digital SPL meter for measurements set to 80. During the subwoofer check level test prior to measurements, the output looked very good with -15 output and -15 input. During the check of the mains I got "Level OK -21.9" Before when I was using my subwoofer as the calibration I could not test my mains. I used the mic calculation file also this time. This is the result I got. 









stereo - gold center red left orange right subwoofer - purple center black left blue right

The subs output looks like a little more than I'm used to seeing. During testing I did not have to change the volume on the AVR or subwoofer this way to test them both. Was I supposed to check them while calibrating the sub to test the sub and mains to test the mains as separate test? That might involve changing the output level on my AVR which I thought would change the calibration then. 

Did I do this test correctly?


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## brucek (Apr 11, 2006)

> Was I supposed to check them while calibrating the sub to test the sub and mains to test the mains as separate test?


The method you use to arrive at the end result isn't that important. You generally want to start with the sub first and get it equalized. Then you can recalibrate the level in the room with the equalized sub to 75dB. Then when you check the mains with the sub you try and get them to meet nicely at the crossover at about the same level. Looks like you have a fairly large peak in your subs response that may need to be addressed...

brucek


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

thewire said:


> Did I do this test correctly?


From your description and graph, everything sounds and looks right. Pretty impressive that your three subs positions all measure almost the same...

Regards,
Wayne


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## thewire (Jun 28, 2007)

Wayne A. Pflughaupt said:


> From your description and graph, everything sounds and looks right. Pretty impressive that your three subs positions all measure almost the same...
> 
> Regards,
> Wayne


Thank you. The subwoofer currently sits centered between my stage made of plywood, filled with insulation, and also sits on top of a "sub dude". There was a 2" absorption panel behind the sub also. I calculated the absorption of my stage prior to it being built and did a demo with a very cheap DIY subwoofer that I made out of parts I had laying around. 

Now for the difficult question... The last time I inquired about one these was in a proaudio/video store about six years ago. The salesman said that he wanted around 2k for one and he said it could not be setup without a pro for which they charged a price to calibrate. They offered additional calibrations at a lesser price if I remember correctly.:hide:

Will a Behringer FBQ2496 Feedback Destroyer Pro be able to lower that peak very well you think? I notice that the pre/pro I want only goes to 25Hz for the internal equalizer.

If so, where is a good place to get it? Should I get a long XLR to RCA cable or get an adapter, and use my current ones for now that I have but would like to replace anyway because I have to use a coupler? Any benefit for getting one of those now since I may want to later on?


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## thewire (Jun 28, 2007)

This is a very nice help section. BQ2496 Feedback Destroyer Pro

I have looked some at the BFD forum area also but what are the limitations (if are) to how much a peak can be removed?


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## thewire (Jun 28, 2007)

I lowered the measurement in REW -5 dB so I think this may give an idea of how far I need to lower it for the 75 dB target.


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## brucek (Apr 11, 2006)

Yep, you've got about a 15dB peak to remove........


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## thewire (Jun 28, 2007)

Does this look alright for an 80dB target? I think I will have to try a 78dB target and a 75dB one later when I can remeasure the HT. If I am turning the subwoofer volume up I should be telling the BFD to target the same level, and measure that in REW. Correct?


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## brucek (Apr 11, 2006)

For your graph, please use a vertical scale of 45dB-105dB and a horizontal scale of 15Hz-200Hz.........

Use a 75dB target and set REW up for 75dB...........


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## JohnM (Apr 11, 2006)

85dB would probably be a closer target level for that trace. Also when adjusting your filters check the box to "invert filter responses" and adjust the Q and gain to try and get the filter response to overlay the measurement, that will give the flattest corrected response. From the corrected trace in that plot it looks like the filter Q/BW settings have not been adjusted.


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## thewire (Jun 28, 2007)

brucek said:


> For your graph, please use a vertical scale of 45dB-105dB and a horizontal scale of 15Hz-200Hz.........
> 
> Use a 75dB target and set REW up for 75dB...........


Bellow 45dB and after 250Hz is where my subwoofer begins to cause reverberations problems in my room according to the RT60. I thought it may have had relevance to the filters that I am applying there at those peaks. I will not post images in the scale of 45dB-105dB and a horizontal scale of 15Hz-200Hz but I thought it may have been an issue to discuss later on.



JohnM said:


> 5dB would probably be a closer target level for that trace. Also when adjusting your filters check the box to "invert filter responses" and adjust the Q and gain to try and get the filter response to overlay the measurement, that will give the flattest corrected response. From the corrected trace in that plot it looks like the filter Q/BW settings have not been adjusted.


I forgot to adjust the Q and gain. I did the BW adjustments. Not sure about a 85 target. Sound and Vision has this to say about the subwoofer.



> Bass limits for the THX-12SUB subwoofer were measured with it set to maximum bandwidth and placed in the optimal corner of a 7,500-cubic-foot room. In a smaller room users can expect 2 to 3 Hz deeper extension and up to 3 dB higher sound-pressure level (SPL). The only response difference between the VAR and THX settings is that the latter reduces levels by 9.5 dB. In either position the subwoofer has useable response up to 250 Hz, where it measured -6 dB. Dynamically, the THX-12SUB will deliver 106 dB SPL at 32 Hz or above, which is better than average.


I usually have peaks around 115dB around 60Hz currently without any equalization applied. This may be something I would try after applying filters, but certainly not something I would attempt otherwise. I will see what I can do about the target later. I have tried a 85dB before but it was overloading the subwoofer.

If I am doing a 85dB target then by the time I am turning my Polk mains up to match, they began to making pop noises. I don't want to overpower my speakers or clip my mono amps, whichever that may be.


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## thewire (Jun 28, 2007)

This is only practice but does this look like what I should try with filters? Would this cause audible distortion most likely this way? I set five filters for this one.


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## thewire (Jun 28, 2007)

Without 1/3 smoothing it says it is going to be worse when I boost the 60Hz area. :scratch:










Placing traps on my back wall fixes that...


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

Steven,

When you post graphs, please give us only the (dated) response plot, corrected and target traces. The others only make things confusing.

What kind of subwoofers are you using – make and model if manufactured, or details on driver, aligment and amp if it’s a DIY?

Also, since you mentioned a stage, I assume this is a smallish dedicated room?

Regards,
Wayne


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## thewire (Jun 28, 2007)

I see your point that could get confusing. I use a single Crystal Acoustics 12" subwoofer placed in the front of the room. It is a 200W 4ohm driver. For the new testing, I have a 20' bettercables coaxial cable coupled using the adapter to a 25' run of stereo subwoofer cable (using one side) that I used to use for my car subwoofers before I lost those. The receiver is a Pioneer VSX-1012 model.

The room is a dedicated room with an equipment closet and an entryway on the left side of the room. The closet in the front left of the room will be where equipment will be located later on. The room needs insulation in some areas and in some places in the rear of the room where not entirely finished due to budget limitations. As I am currently remodeling our other home for sale (painting, laying tile etc) we will be upgrading the HT soon. Two subs is an option but I have been advised to avoid this if possible.

Photos of the room. 

http://www.flickr.com/photos/tns29/sets/

My build thread here that is very outdated at this time but will update. My father got a new 2007 Sierra, I repainted my crown molding, finished sealing my entrance door, got some 244 bass traps on the front wall, moved my speakers off the stage, and moved the sub to the front of my room onto a sub dude, and bought a new tweeter for my center channel since my last post.

build thread]


I think that the problem is not my rear wall but instead axial mode problems from my left right wall mostly relating to my ceiling. It needs better insulation and I hear problems near the steel beams up there. The pink insulation in it will maybe last another year but I hope to fix that sooner. Maybe inexpensive insulation left in the bag will help there. That may help improve the tangential and axial modes I seem to have very close around 60Hz. I'm not sure.

I will also use the new 4.11 version and correct my graphs. I have many on my website but that are not in sets that I will need to delete later. I thought while I was away, I would practice with my older measurements while reading.

I wasn't purposefully meaning to make things confusing but rather trying to clear up my own. I apologize to anyone to that I may have done so. 

Thank you.

edit: I also got another mono amplifier.


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

You might want to try different locations for the sub, like maybe a corner. That usually gets better readings, both smoother and better-extended, than center-of-wall placement. It also may reduce the span between the highest and lowest peaks, which will make for easier equalizing. Once you find the best location, you can add your second sub there, if it’s a match for the first.

Regards,
Wayne


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## JohnM (Apr 11, 2006)

thewire said:


> This is only practice but does this look like what I should try with filters? Would this cause audible distortion most likely this way? I set five filters for this one.


Those filter settings will be doing a lot more harm than good. They are very wide, conflict strongly with each other and some have very high gain which is in all cases a very bad thing. 

The figure on the far right of each filter setting shows its bandwidth in Hz. The 48Hz filter, for example, has bandwidth of 55Hz so is affecting the range from around 20Hz to 75Hz. The 32.8 Hz filter is affecting from about 15Hz to about 50Hz. The 20Hz filter has high gain, 9dB, and affects from about 15 to 27Hz - much of it countered by the 32.8Hz filter. The 64.7Hz filter has 15dB of gain and affects from about 55 to 75Hz. It looks like you may be trying to use that to counter the notch in the response. That doesn't work, notches like that are caused by the direct signal being cancelled by a reflection, making the direct signal bigger also makes the reflection bigger so the situation is not improved and the gain of the filter is likely to cause clipping and distortion at several points in the chain. Is the 221.8Hz filter being used as some sort of pseudo crossover? It is well beyond the working range of most subs when there is a crossover in the path.

Avoid any filter with more than a small amount of gain (3 or 4dB). Make sure the filter bandwidths correspond to the problem you are trying to correct. Start with 1 filter on whatever is the biggest peak you are trying to address and listen to the effect of that before moving on to another, if you still hear problems in the response.


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## thewire (Jun 28, 2007)

Wayne A. Pflughaupt said:


> You might want to try different locations for the sub, like maybe a corner. That usually gets better readings, both smoother and better-extended, than center-of-wall placement. It also may reduce the span between the highest and lowest peaks, which will make for easier equalizing. Once you find the best location, you can add your second sub there, if it’s a match for the first.
> 
> Regards,
> Wayne


The HT, equipment closet, and entrance area is partially underground with concrete on all sides including the ceiling but the ceiling has an additional support of very thick steel that is supported by the large steel beams. It was a reverberation chamber before any framing was done with the exception of an opening where one of the future doors went.

I tested with my DIY subwoofer before the room was completed at the center front wall and ended up placing it there since the bass seemed to be most even throughout the room with it being there. I also added a hookup wall plate in the right corner of the room for future use because while I was listening it was not very loud there and I thought it may be a good place for a subwoofer someday.


















I bought the new subwoofer and a new driver for my DIY speaker box that I tried but it did not work having a subwoofer in my back right corner and the new one in the center. They were canceling each-other out and my new replacement driver (4 ohm) was becoming very badly distorted by my Marantz 180W @ 4ohm mono amplifier so I returned the speaker to the store.










I have moved the sub and tried different locations by ear so far. The first place I had it was the back right corner. My father complained that he could localize it from the back right seat that he usually sits in. I tried a 50Hz and 80Hz crossover and neither was working to eliminate that problem. I had placed it there by placing the sub at the center front row seat and finding where it sounded the best. I could also localize it on the right side also in the front of the room after using the receivers automatic setup during certain scenes because I had to turn up my subwoofer very loud to blend with the mains. That was before bass traps however. 

I ended up moving the subwoofer to the center of the back wall where according to my folks, they were unable to localize the sound anymore and it did not sound "boomy" to them there. I left it there sitting on of my equipment rack because I was unable to place it behind or bellow it. That is where I tested my first time with REW and began placing room treatments. The measurement looks very similar to what I see now with it placed in the front of the room but I will have to try placing it there on the riser (which I am not sure will work) after I move the equipment to retest that location more accurately.

I tried the right side of the room and also the left side like shown bellow after installing bass traps - the new 244 traps and prior to doing any new testing with REW more recently. It sounded excellent on the right side of the room but I was still able to localize it. I could not place it on the floor which I think had to do with the problem. I tried facing it different directions but it seemed to make things worse. The left side sounded very quiet in comparison to the right.










The closer I put it to a wall, the more I am able to localize bass there with the exception of placing it between my left tower and center channel as seen bellow. It sounded good there but I was able to localize higher frequency sounds there around the crossover. It would probably be the 80Hz peak that I am seeing during my testing.










I would mostly like a second subwoofer to extend the low frequency which I understand is possible. I think that I would place it in the back of the room if I could and set the phase on the subwoofers accordingly. I have the phase set to normal in the front of the room now and in the back of the room, reverse was working best. I found that in the back it liked to be slightly closer to the left wall, which has rooms on the other side and is not drywall/insulation/bedrock such as the right side of the room. It might look something like bellow except that I would try tweaking them left and right slightly which I am able to do with good results. The speakers in the SketchUp model are not to scale but the rest of the room is. I have planned to first try placing the dipoles on the right and left sides of the front row and move the rear channels away from the center of the back wall and more in a Dolby type configuration. I'm not sure about the bookshelves yet. I have since moved my panels on the front wall together, and placed standard sized GIK 244 bass traps on the front stage area covering the front wall and in front of the screen, which I need to complete placing more under the screen area.








There is conduit behind my screen for running wiring but I have not yet decided if I will use that or hide it behind baseboard on the stage.

It looks like this currently.


















Moving it forward and back did not make any difference but if moving it to the left or right between the stage a few inches helps, I'm not sure yet. It seemed to help in the back of the room but it could have easily have been my imagination. I will test that with REW and see what happens.

JohnM,

Thank you that explanation helps allot and I think it is beginning to making better since to me now. The higher filter I tried applying was trying to lower the peak around 250 because according to the RT60 on my measurements with the sub, it went off the chart for one of my seats, and the other seat was slightly above .08 seconds at that frequency to about 300Hz. It did a similar thing for my sub higher above that also in the testing. I had the subwoofer speaker target in my settings with the crossover at 80Hz and I had thought the sound would not be going so high with these settings enabled unless there was some kind of adjustment I was supposed to be tweaking. It is my mistake, and I think this is only a result of sound after the speaker has began loosing signal. If that is not what I am seeing, please let me know. :sad2:


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## thewire (Jun 28, 2007)

The RT60 measurement of the subwoofer looks fine with a one octave filter. It goes until 200Hz and then falls. I think this must have been where I made an error in looking at the measurement. It does much less with mains+subwoofer for one third octive bands.


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## clubfoot (Apr 12, 2007)

The easy way to find the proper location for a sub is to place the sub in your usual seating position and move your mic around the room. Disregard what you hear,...use REW to take multiple measurements and try to find a response that tracks the "ideal" 75db target curve. The closer you get it to track the curve the lower the number of filters you will need to employ,...the better it should sound. If you place the sub behind you, it will probable need a phase adjustment to blend with the mains. Small changes in location can make a big difference in measurement!

Hope this helps.

If you take a look at my two plots in my sig those are without smoothing and no filters, BFD in bypass, only phase for smoothing with mains.


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## thewire (Jun 28, 2007)

I unchecked the smoothing and tried the "find peaks" with an older measurement I did with version 4.10 using a 75dB target the other night. This had been before I realized however not to be using the left channel for sound card calibration. The response was slightly shifted to the right where 25Hz was at 75dB instead of 20Hz and bellow 15Hz it was climbing. REW recommended one filter at near 33Hz where the subwoofer is at right now and it was not more than -15. I think I may be alright, but I will at least experiment with other locations, and I definitely want to try moving it left and right slightly. The measurements for the back of the room have the same peak at 33Hz, with some ringing around 80 etc where I need to finish room treatments. I also might like my subwoofer there because according to the manufacture of my subwoofer, THX says I should put it there.:daydream: They themselves recommend placing it at the side of the seating. There are two large ports on the back that fire so heavy from the long through driver that it moves quite a bit of air, and placing it next to a bare wall one can hear the air moving off of it. I placed a 2" ATS Acoustics panel behind it for the time being.

Thank you for the recommendation. I will certainly have to see what results look like at different locations in REW. I will try using DVE again after I setup a new location if one works and see what happens.

I'm ordering the BFD sometime later this week and maybe some room treatments.


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## JohnM (Apr 11, 2006)

RT60 results are not meaningful in domestic sized rooms below about 200Hz, and even then are only meaningful when running a main speaker with the sub. For low frequencies use the waterfall and decay plots to see what the room is doing.


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## DrWho (Sep 27, 2006)

Looks to me like you've got your sub set about 15dB too hot...

I think that correlates to about 23x too loud.


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## thewire (Jun 28, 2007)

JohnM said:


> RT60 results are not meaningful in domestic sized rooms below about 200Hz, and even then are only meaningful when running a main speaker with the sub. For low frequencies use the waterfall and decay plots to see what the room is doing.


Okay



> Looks to me like you've got your sub set about 15dB too hot...
> 
> I think that correlates to about 23x too loud.


My receiver keeps telling me to turn up the volume during the setup with my RS meter, so I have been turning up the volume on the back of the subwoofer trying to match it's suggestion. 

When I setup the subwoofer using DVE on my XA2 and the analog out, I set the back of the subwoofer to THX, and turn the volume down in the menu for the 5.1 setup. That gives me an option of calibrating the subwoofer to 70, 75, 80, etc. Right now I have it sitting at -8dB and the mains are around -2dB. Then I can calibrate the mains to 60, 65, or 67. I run a pair of 14 gauge wires twisted together at the ends to each of the speakers. This is because I did not buy the speaker wire and it was all I could find in-wall locally. If I turn up the volume on my receiver (+4 I think) I would be able to do a 70dB calibration although I thought this was against some kind of general rule of setup to boost the signal. I use the mode on the AVR called "multi-channel in". I could try setting the subwoofer calibration to 65 and the mains to 65 also, then turn up the volume, but I think this would be causing me to run gear kind of hot for the subwoofer. I think part of my problem is I cannot set the distance for the subwoofer on the player and the only thing that the input on my AVR seems to do is adjust trim. 

Then I go into REW and interpret results for what problems I have been hearing using the receiver but not "multi channel in". :mooooh: This is why I thought it would be beneficial to me using the new feature for looping the left channel somehow. 

At the image at the top of the thread, I ran my subwoofer +5dB hot, and then turned up the volume of my mains and it +5 to see exactly what may be going on. It was probably closer to +10 hot. I just set the subwoofer and mains as close possible to pink noise 75dB as possible without turning up my AVR. :dontknow:


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## thewire (Jun 28, 2007)

I have not tried turning down the subwoofer on the back yet bellow the THX setting output level I get with readings. Should I try that?


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## thewire (Jun 28, 2007)

I was reading some information about setting up the subwoofer and I came across this statement.



> In a THX® system, Front Left, Centre, Front Right and Rear Total should each give an SPL of 85dB with a 0dB input using pink noise.


I think that I will look into Johns observation. :whistling:


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## thewire (Jun 28, 2007)

The reason it may have looked +5 hot was since after calibrating the subwoofer to 85dB and then setting the mains to 75dB, I raised the volume on my receiver +5 and then checked the SPL on the meter in REW that it said 80dB with the pink noise generator, knowing this is where the speakers and my sub crossover close at. 

In DVE I would like to set both my mains and my subwoofer to 75dB. Will I be able to do this after setting up REW with a 75dB target for both?


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## brucek (Apr 11, 2006)

> In DVE I would like to set both my mains and my subwoofer to 75dB. Will I be able to do this after setting up REW with a 75dB target for both?


I feel you're somewhat confused about the role of REW. It's intent is to provide filter recommendations for equalizers to smooth the subwoofers response. It also allows you to obtain a smoother transition between the mains and sub by revealing a better sub phase adjustment.

Any levels that are used during the course of REW testing have little if nothing to do with the setting of system levels once you're finished using REW. They're completetly arbitrary and only adjusted as a means to an end - which is setting EQ filters.

Once you're finished with REW and equalization of a BFD, then use the receivers test tones or DVE or whatever you like to set the actual system levels.

brucek


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## thewire (Jun 28, 2007)

brucek said:


> Once you're finished with REW and equalization of a BFD, then use the receivers test tones or DVE or whatever you like to set the actual system levels.


I am using the XA2 player directly to my amplifiers with the levels set to 75dB using DVE. My speaker settings are set to small, PCM, and the "Digital Out HDMI" is set to "AUTO". 

Can I use REW directly to my amplifiers to determine speaker distance settings?


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## thewire (Jun 28, 2007)

I tried a search here and appears that it may be an acceptable practice, even although my amplifiers as a single solid state amplifier (not sure about bridged) are not appropriate for running a full range sweep. I could at least get an idea by using a cutoff frequency at the XO, and do the subwoofer separate for setting filters. 

I had one comment about the volume last night. While the previews are playing my father says "loud enough for you?". :hsd::dontknow: We watched b movie. I will do another test later today to be sure my AVR was not causing a problem with the measurements.:cunning:


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## thewire (Jun 28, 2007)

My left and right walls are already offset by one foot. I have tried moving the subwoofer, testing different locations. I even tried playing reference through the other speakers. Every indication says that I have 85 target and that I am -5 dB away from reference which is very easily corrected by adding a second subwoofer and simply turning down the volume. The left and right surrounds + better left and right towers are what is missing. I don't know that a BFD can help my situation at this point in time. :huh: I was recommended at another forum to try here last week. Could anyone explain what a BFD is going to help me with right now?


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## JohnM (Apr 11, 2006)

I have to admit I'm losing track of what you are trying to do. The main problem with your sub, based on your original plot showing sub and mains, is that it is too loud relative to the mains. To fix that just turn it down so that when you play DVE or similar test tones through each speaker in turn and then the sub your SPL meter shows the same reading for all. If you then feel the low frequencies are a bit lacking increase the sub volume until the sound is how you like it.


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## thewire (Jun 28, 2007)

My goal is getting the HT best sounding as I can in the present for movie watching and as close to reference as possible for later with the newer speakers to match the current sub or subs. I'm not so much concerned about the other speakers being softer or the subwoofer being louder at his point as long as I can get them sounding decent to watch the occasional movie on the weekend. The other speakers are being moved to a new media room or we would have to buy new speakers for there. I think it makes more since to buy new speakers for the HT to match the sub, and move these to the new media room. The problem I have is that boosting the subwoofer now causes problems because it becomes louder than my other speakers. I do however want to have the 15Hz to 20Hz be a flat response also which would require a second subwoofer. I explained to the lady of the house that adding the BFD was less expensive than treating my front wall with custom absorption panels from GIK and she would rather me spend my $$ on the BFD because it is going to lower the peak that I have after I get to the reference 75dB. I need the BFD eather way. I need the front wall treatment eather way. I don't know what to do.

Basically I am trying to explain everything to someone that is not familiar with the setup of a HT, trying to treat things in an orderly fashion and such while enjoying movies. I don't have complaints about it being to quiet. :no:


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## thewire (Jun 28, 2007)

I know how to build the GIK traps, but it is something that goes under my screen, I want it to be perfect, and I am worried I will have less than perfect results with my first attempt at making them. She suggested I make them myself, or buy the BFD. :gah:


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## JohnM (Apr 11, 2006)

From your descriptions so far you have been evaluating alternative sub positions by ear, but if you do not adjust the sub level relative to the mains for each new position you are wasting your time. The graphs you have posted of your sub relative to the mains show it much too high in level compared to the main speakers. It will draw attention to itself because of that, leading you to reject positions because the levels are wrong rather than the performance is not right. The measurement in your first post shows a small resonance, adding about 4dB at around 48Hz, and several others above the crossover where they are not having much effect on the overall response. The bulk of the sub response in that plot is simply the natural performance of the sub in the position you have placed it when measured where you put your mic, it is NOT a room peak and it is high because the volume of the sub is turned up too much.

To properly evaluate an alternative position take REW measurements first, to see if the position is helping to increase the output below 25Hz where it currently rolls off. The only way to raise that will be to get the sub closer to a wall or into a corner. If the output at low frequencies looks better in a position go through the normal sub/mains level balancing first then listen to how it sounds. Getting closer to walls or into corners will probably result in some peaks in the response as room modes are driven into resonance. A BFD could help reduce those, if they are below 80Hz or so you would need enormous bass traps (several feet deep) to achieve a similar effect.


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

> I ended up moving the subwoofer to the center of the back wall where according to my folks, they were unable to localize the sound anymore and it did not sound "boomy" to them there.
> 
> I tried the right side of the room and also the left side like shown bellow after installing bass traps - the new 244 traps and prior to doing any new testing with REW more recently. It sounded excellent on the right side of the room but I was still able to localize it.
> 
> The closer I put it to a wall, the more I am able to localize bass there with the exception of placing it between my left tower and center channel as seen bellow. It sounded good there but I was able to localize higher frequency sounds there around the crossover.


Hopefully you’ve realized by now that you don’t have to rely on your ear to find the best location for your sub? REW can do that for you much more accurately. You don’t even really have to move the sub all around the room. You can plant it at the listening position and take the mic to prospective subwoofer locations. The REW reading will be the same as if you had the sub there and measured from the listening position.

Don’t worry about getting a REW reading that tracks the Target as close as possible. You’re looking for a location that will give the best extension with the fewest peaks and valleys, or one with peaks and valleys that can be easily equalized. As John noted, this will usually be at or near a corner. The Target in REW can easily be re-adjusted, as can your sub level, when it comes time to equalize with the BFD.



> I would mostly like a second subwoofer to extend the low frequency which I understand is possible.
> 
> I do however want to have the 15Hz to 20Hz be a flat response also which would require a second subwoofer.


Adding a second subwoofer is no guarantee that you’ll get improved extension. Adding a second identical sub gets you the same extension as the first, only at a higher SPL level. Adding a second sub that’s either better or worse than the first will get you no improvement over what you had with the one (you’d want to go with the better new sub and ditch the older one). If you’re looking for sub-20 Hz extension and you aren’t getting it now, a change in subs is in order.



> I think it makes more since to buy new speakers for the HT to match the sub, and move these to the new media room.


Any sub can be “matched” to any set of speakers. That is not an issue as it is say, with center-channel speakers vs. main L/R.



> The problem I have is that boosting the subwoofer now causes problems because it becomes louder than my other speakers.


Well, yeah... 

Regards,
Wayne


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## thewire (Jun 28, 2007)

A place with smoothest response is on the center of the left or right wall. This causes the response to suffer greatly bellow 50Hz, and to increase above that, but there are no large dips or peaks. Between the left and center channel there are two large dips. Placing the subwoofer into a corner is what got me into trouble in the first place, but I see no problem with putting one on each corner of the _front_ wall. I will try testing that. I am less concerned about lower extension, more concerned about feeling where the LFE is originating from. I don't think we need a subwoofer in my bedroom or the new media room, so I hope that results look better there.:boxer:


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## thewire (Jun 28, 2007)

Here are the measurements of the subwoofer in the front corners. I moved the 244 traps to cover the entire corners this time also. What do you think? Could I eq two like this with the BFD for a nice response? I could have not as bad of a null at near 60Hz?


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

What’s your crossover frequency? The graph looks peculiar; I’m not used to seeing a big hole like that in a smallish enclosed shoebox room. Plus, there is no rollout at the upper end, as we should be seeing with the crossover engaged…

SVS’ Ed Mullen has noted in other threads that moving the sub a few feet down the wall from the corner can eliminate a null and retain the benefits of corner loading.

If you want the extension down to 20 Hz or below that you’ve been talking about, you’re going to need a different sub.

Regards,
Wayne


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## thewire (Jun 28, 2007)

I have the soundcard directly hooked into the subwoofer. Crossover is at 80Hz. I set it to the SPL meter at 75dB and used the 75dB target. I have the subwoofer turned down allot. It has never been this low. The dial in the back is sitting at about 3 oclock. I have extention to 19Hz at the 85 target, but I don't think I'm supposed to post those results.


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## JohnM (Apr 11, 2006)

It would be better to connect the soundcard to your av processor so that you see the effects of the processor's crossover, the sub's own crossover would then be disabled or set to its maximum. You should set your sub's volume control by using a 75dB test signal from your processor or test disc, setting the processor level trim to zero then adjusting the sub's volume control to get 75dB at your listening position.


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## thewire (Jun 28, 2007)

I don't have a receiver anymore. It is gone. The subwoofer has no adjustable crossover on the back. It is 80Hz crossover.


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## JohnM (Apr 11, 2006)

Looking at the manual of your sub it does not have a crossover filter, it relies on the processor/receiver to take care of that which is why your measurement does not show the roll-off of a crossover. That deep null is probably related to the mic position, was it on the centre-line of the room? If you move the mic off-centre does the null become shallower?


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## thewire (Jun 28, 2007)

When I set the volume of the subwoofer using the test disk, playback from my subwoofer is extremely loud from the soundcard. I would not recommend anyone use the XA2 test tones. Something went horribly wrong there, and I refuse to touch it again.


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## thewire (Jun 28, 2007)

The mic was located on the head rest of the center seat front row, inside a slinky pointing upwards. It is the center of the room. I will try moving the couch.


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## thewire (Jun 28, 2007)

Moving the seating forward seems to make little difference. Placing the mic at the left or right seat does. This is with the subwoofer in the right corner again where the 50Hz peak is lower for the center seat. The couch was moved forward about one foot.


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

JohnM said:


> It would be better to connect the soundcard to your av processor so that you see the effects of the processor's crossover, the sub's own crossover would then be disabled or set to its maximum.





thewire said:


> I don't have a receiver anymore. It is gone. The subwoofer has no adjustable crossover on the back. It is 80Hz crossover.





JohnM said:


> Looking at the manual of your sub it does not have a crossover filter, it relies on the processor/receiver to take care of that which is why your measurement does not show the roll-off of a crossover.


That would sure explain why everyone’s been able to localize the sub so easily. I suggest getting an outboard crossover...



thewire said:


> Moving the seating forward seems to make little difference. Placing the mic at the left or right seat does. This is with the subwoofer in the right corner again where the 50Hz peak is lower for the center seat. The couch was moved forward about one foot.


Once again, try moving the sub down the wall away from the corner a few feet. Try it in 1-ft. increments in each direction and see if that null disappears.

Regards,
Wayne


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## cassb (Mar 19, 2008)

I don't mean to hijack your thread, but holy cow, nice setup! Can you pass me the popcorn? :T

Geez, I'm glad just to hear my DIY speakers play ... maybe someday I'll graduate to a dedicated room like you have.


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## thewire (Jun 28, 2007)

That is where my subwoofer ended up at in HT version 1.0 before this one and exactly how I did it. I will try moving away from the corner slowly and see what happens. I have to correct myself from before. I was looking at the dial upside-down. The volume was up about 25%-30% for the measurements. I plan to use a pre/pro later so I think I will be alright for now. The XA2 has it's own bass management. The pink noise on the XA2 after setting everything to zero sent my AVR into safety shutdown mode. It caused my mono amps to temporarily click off directly hooked into them, so I am not going there again. I will only use DVE from now on. I already discussed a new AVR and they are in agreement that a universal remote is not worth the cost of simply buying a new receiver, and one that is better compatible with a new plasma, has more features etc, so all is alright there. I plan to use my televisions variable output for the setup in my room anyway which is hooked up to a two channel amp.


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## thewire (Jun 28, 2007)

This is the subwoofer on the back wall again where I started last time I was taking measurements in the previous thread. I still have that valley around 25Hz there.








When I move the subwoofer along side the wall up front. which way do I point the driver? That part has always confused me. If I used the back wall, I would want to use the front wall also...


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## thewire (Jun 28, 2007)

Here are a couple more using the method of placing the subwoofer on the center seat and moving the mic.

Mic sitting behind my equipment rack (blue) in the back center of the room and the mic sitting on the floor of the front center of the room (purple).









Mic sitting on the right wall after adjustments (green) and mic sitting between the right tower and center channel (black).


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

Looks like either of the front locations will be the ticket. Get the crossover happening and a little EQ and you’ll be in business. :T

Regards,
Wayne


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## thewire (Jun 28, 2007)

Thank you again Wayne. This has been a great learning experience. THX Tech Level 1 training is only a couple months away now but I feel like it has already began.:nerd: 

I will order the BFD then now. :sweat: What happens to a waterfall like this when a larger subwoofer is introduced? Do you you know where I could find a nice example?


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

thewire said:


> What happens to a waterfall like this when a larger subwoofer is introduced?


It will show an increase in signal level, and ringing, below 30 Hz. The signal level will be due to the bigger sub’s better extension; the ringing will be due to the fact that it’s next to impossible to treat ringing that low.

Regards,
Wayne


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## thewire (Jun 28, 2007)

When I use the set target level button, REW sets it to a 83.3 target and then suggest a 0.250 BW versus with the 75 target at 0.143 BW. It sets both filters at the same peak at 49.66 and suggest the same level of -8.8 gain for each. I did this without adjusting the input volume of the mic this time which seemed to have been incorrectly having to think I was getting further extension with the higher target. This was the difference between setting the level on the back of the subwoofer, versus the THX switch setting. 

When I assign the filters later after measuring through the BFD, do I use the 75 target or the suggested 83.3. Should I raise the volume to 85 if it still suggest the 83.3? The help area says that the target is important for setting the correct gains and width, and I keep getting all kinds of error messages with the 75. 

Also..I am supposed to set the input level of the mic using the 75 target and let REW determine the appropriate target by that setting? My input volume is rather low with the 83.3 target but I presume this is to prevent my mic from clipping?


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## JohnM (Apr 11, 2006)

The target level figure that REW determines is its best estimate of the level that the response would show if the peaks and dips of the room were not present. It has no bearing on the mic level, you only need to set the mic level once when you do the input level calibration and not adjust it afterwards. The input level setting allows some headroom during measurements to provide for the effects of room resonances and avoid clipping, as you presumed. 

After you have allowed REW to set the target level leave it there when finding peaks, assigning filters and optimising peak gain and Q.


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## thewire (Jun 28, 2007)

Thanks John. That makes perfect since to me now. The BFD just arrived and so did the accessories also. :yay:


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## thewire (Jun 28, 2007)

I gave it a try with the filters with the measurements then did some listening. It didn't sound right to me the way I was doing it. I went and took meaurements using a macro while I was holding the mic in front of me. I then took filters and applied those to that result. I did all this after setting up the inputs, and then changing it to the 85 target. I uploaded my filters boosting slightly around the 55Hz area, and making a few adjustments here or there with the peaks. This is a look at measured and predicted response. 









Measured


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## JohnM (Apr 11, 2006)

As you are measuring without a crossover your target should be flat rather than a sub crossover curve (change the shape in the Target Settings). That would reduce some of the cuts.


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## thewire (Jun 28, 2007)

I will give it another try. Should I try and add the boost again? It looks close to where REW wants to remove a peak.









Should I be doing this in the 83.3 target? Is my crossover wrong? My room is causing problems? 

This is the mains again with a 75dB target, subwoofer with the 85dB target.


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## thewire (Jun 28, 2007)

I will do more searching of how to setup my subwoofer after equalizing with the BFD.


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## JohnM (Apr 11, 2006)

Sub still looks high compared to the mains


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## thewire (Jun 28, 2007)

Maybe I could fix that problem with the 4ohm mains from Crystal Audio. :scratch:

























For entertainment value... these were my calculations for the room modes and my..:heehee:.. Hellmholtz Resonator (or whatever it may be) done without any Exel or person with Exel to do the calculations. :doh: It is that large peak that can be seen on the waterfall above. I think that REW is quite cabable of seeing a resonance in a room. It isn't completely filled with insualtion yet... Thought it might be interesting to note that here since I saw a thread about finding a room resonance. I would not know the difference however if I had not done the calculations etc, but REW does see it.

Edit: Not sure about the damping factor. My amp specs say 200 at 8ohm. EIA dynamic power is 270W at 4ohm.


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## JohnM (Apr 11, 2006)

thewire said:


> Maybe I could fix that problem with the 4ohm mains from Crystal Audio.


Why wouldn't you just fix it by turning the volume down on the sub a little?


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## thewire (Jun 28, 2007)

I tried setting everything in DVE on the limited bandwidth pink noise to 65dB in effect turning down the sub from 71dB reference to the 65dB area, close to where the THX setting is at 64dB, whatever that might be indicating. The problem I have is that turning up the subwoofer makes all kinds of new sounds that would otherwise not be obvious, and makes those with the mains that are obvious less obtrusive, more clean. I choose not to turn up the volume last night becauase with the movie I was watching "the island" it was just to loud! Turning up the volume on the subwoofer isn't going to hurt anything that I am aware of. In fact, before my AVR quite working, it wanted me to turn up the volume on the back to around 85% before the auto-setup would even give me the time of day. Isn't that some kind of indication that maybe the room needs the subwoofer turned up? The max SPL I got playing around the other night with the subwoofer turned up was 99dB. I didn't watch the movie like that but I did some quick testing with a movie.

Are you suggesting that I should not get new speakers for the theater, another kind perhaps, or just turn down the subwoofer volume?


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## thewire (Jun 28, 2007)

I'm sorry I'm kind of getting confussed about the setting of the target. Yes I turn down the subwoofer.


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## thewire (Jun 28, 2007)

I did also look at the Polk line of surrounds and other center channels. I even asked about adding some to my current speakers for a set of 3 HT systems in a thread. :bigsmile: I asked about crossovers, matching the speakers I have with new ones etc. Nobody has ever offered me any advise for speakers before, with the exception of subwoofers. I might call Polk and see what the would recommend. It has been on my list of things to do actually.


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## thewire (Jun 28, 2007)

I bridged my front left and right speakers with my other mono amps. That is 360W on a 250W speaker but I have done this before without problems. I used the same matching cables and wire to do so as I use for the other channels with the exception that I am running a longer one for the center channel. The speakers are still set to small. I aimed my left and right forward as Polk recommends and I tilted the center channel upwards more. I moved my rear speakers to the corners so that the bass traps are behind them. 

Regarding the power on the left and right speakers, is it safe to take measurements in REW with them like this? Is there any risk?


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## thewire (Jun 28, 2007)

The new pre/pro I think I will be getting has a left and right subwoofer output. The manufactor of the subwoofer recommends I place it beside the couch. I mentioned before that I had the smoothest response there. Here are some meaurements I have with the subwoofer on the right side of the room and the left. The driver is facing the rear wall. I would be interested in doing this because I could place my other two tower speakers on the subwoofers and they would be near the same height as the ones in the rear. I don't have much use for the other two tower speakers because my television doesn't sound very good with the other amplifier and music does not sound that great in the other room. Tell me what you think about adding a second subwoofer like this. 

Right side filter









Left side same filter









right side waterfall









left side waterfall









measured and predicted right side









P.S. I have a better paying job now than last summer. :jiggy:


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