# First equalization and having trouble.. anyone help please



## thewire (Jun 28, 2007)

I setup my MP3+ USB external sound card and saved the file, setup my RS digital SPL meter with the subwoofer at 75, then I turned up the volume on the Crystal Acoustics subwoofer a few dB to 85 and took a measurement. I did not check the C weighting because I had the RS meter file loaded. I added some filters to what REW suggested and optimized the peak and gain. This is location in my room that gives the most overall smooth response. I was not able to measure with a crossover since my receiver is being repaired. I moved the crossover up on the graph. I measured after applying the filters without adjusting subwoofer volume on my HD-DVD copy of DVE with limited bandwidth pink noise to be 64dB. The limited bandwidth pink noise is -3dB less than my other speakers which measure at 67dB after I have calibrated them using the full bandwidth to set them to 75dB. I have read that the subwoofer is -3 less on the disc. The speakers are set to small. Am I done or is there something that would require being done differently? :help:


----------



## thewire (Jun 28, 2007)

I measured tons of various settings out of the player using the spectrograph. I have measured so many things since I started using REW I can't remember what all I meausured anymore. Anyway.. The settings are correct but I had to switch my auto HDMI out to PCM. I raised the subwoofer volume a few dB to match and lowered the rest, but I used REW to do this (looking at RS SPL meter) with filters after, and it sounds amazing. It works for DVD now also. Thanks again.


----------



## JohnM (Apr 11, 2006)

Probably easier to use RTA mode when measuring pink noise, that way the ideal response is flat rather than rolling off at 3dB per octave. Did you have averaging on for your measurements? Exponential averaging works well with noise measurements.


----------



## thewire (Jun 28, 2007)

I think I forgot that averaging needed to be turned on before the measurements. I did try that but for the above measurements it was off since I did not have it on before taking any. I will try again with the RTA mode. What is a good average to apply?

edit: Does it matter the SPL cal file was loaded? This is with the line-in directly from my XA2.


----------



## thewire (Jun 28, 2007)

I read in the help file that the cal is applied. It looks very similar to what I measured with the meter and I thought I was on the right track to measuring bass management directly from the player to confirm it. This was one I measured with the mic and the subwoofer and mains playing together. It is the full bandwidth pink noise on DVE and levels are set the same. I have since moved the subwoofer location.


----------



## thewire (Jun 28, 2007)

This is Pink PN at a -16 sweep with my mains (light color) using a Y-cable and then the next measurement is the subwoofer included in a second Y-cable. If I measure this with my mic from the XA2 what is it I am looking for to be sure they are good. A flat looking meaurement at -20dBFS? 









This is a RT60 I did of a sweep meaurement of my mains with 1/3 octave bands and EDT at -16 if anyone was interested.


----------



## thewire (Jun 28, 2007)

With REW SPL meter cal file loaded...

Band limited pink noise for the subwoofer in DVE = 75dB (RS digital meter at 80 C weighting) in REW or 67dB C weighting on a RS digital meter set to 70.

Pink noise at -30Db FS in REW = 75dB on a (RS digital meter at 80 C weighting) in REW and 67dB on the RS digital meter set to 70.

Band limited pink noise for other channels in DVE = 67dB (RS digital meter at 80 C weighting) in REW or 60dB on a RS digital Meter set to 60. 

Pink Noise in REW at -20dB FS = 85 in REW or 77dB on RS digital SPL meter at the same setting

Therefore in DVE my subwoofer should measure at 67dB on my RS SPL meter at 70 and should measure 75dB in REW at 80. My mains should measure at 67dB on my RS SPL meter (set to 70 C weighting) and 75dB in REW set to 80. No 3dB difference that I see going on.

I setup my mains and subwoofer using the limited bandwidth pink noise similar in REW and my full bandwidth pink noise pan around the room is at like 77dB. My mains ended up at -8 when set to small for the DVD side. It wants me to raise the volume on an AVR. 

I wonder why is there no Full bandwidth Pink Noise in REW and what is it on DVE for. I also am curious hy is it louder. Could be something to do with a dial norm on an AVR maybe.


----------



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

thewire said:


> Am I done or is there something that would require being done differently? :help:


I’d move the Target up to about 80 dB or a bit more. As it is now, assuming you have a PEQ, you’ve cut you sub’s level nearly 20 dB. That’s way too much.

Also your sub seems to be strong on the top end and weak on the bottom end, which is not good. At least that’s what it shows in its present location. Speaking of...



> This is location in my room that gives the most overall smooth response.


If you’re going to equalize the sub, then you need a different approach. You don’t have to worry about finding the location with the smoothest response, because the EQ is going to take care of that. So, you want the location that gets you the best output and extension, and response that is “equalizable” (i.e. no more than about a 15 dB spread between the worst peaks and depressions). If you haven’t, I’d try a corner, if you have one available. Hopefully that will get you extension closer to 20 Hz, and get your overall response strong on the bottom end and weaker on the top, which is typically what you want. 

Hopefully someone else will chime in about your other questions.

Regards,
Wayne


----------



## thewire (Jun 28, 2007)

Here are different variations with the subwoofer in the right corner without filters or eq.

Subwoofer set to THX (no volume control), then set to an 85 target and a 75 target at a -12dB FS sweep.









Subwoofer set to THX at a 85dB target at -20dB FS. This is exactly the level I would listen to similar with DVE and a 75dB target at -30dB FS.  

Did it work? What could I do now? 










edit: Can't I improve lower extention also by stacking them on eachother?


----------



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

> edit: Can't I improve lower extention also by stacking them on eachother?


There are two subs? Did I miss that somewhere?

What’s wrong with your crossover? The sub isn’t supposed to be flat out to 250 Hz...

Regards,
Wayne


----------



## Blaser (Aug 28, 2006)

thewire said:


> I setup my MP3+ USB external sound card and saved the file, setup my RS digital SPL meter with the subwoofer at 75, then I turned up the volume on the Crystal Acoustics subwoofer a few dB to 85 and took a measurement.


Why?


> I did not check the C weighting because I had the RS meter file loaded. I added some filters to what REW suggested and optimized the peak and gain. This is location in my room that gives the most overall smooth response. I was not able to measure with a crossover since my receiver is being repaired.


So you don't have an AVR in the loop? Are you using computer to BFD to sub?


> I moved the crossover up on the graph.


Why?


> I measured after applying the filters without adjusting subwoofer volume on my HD-DVD copy of DVE with limited bandwidth pink noise to be 64dB.


I understood you are using REW, Why are you mixing with DVE now? Limited bandwidth can yield different results from full bandwidth... But again why aren't you using REW sin sweep from say 10 to 200 Hz to test subwoofer FR?
I think either you or me are missing something. Sorry for my questions, but if you reply to them we can try to figure out what the required is.


----------



## thewire (Jun 28, 2007)

I use the bass management in my player. For testing with REW, I hook the output of the BFD directly to my subwoofer input. My receiver blew up when I fed a signal from my XA2 (pink noise) after turning up the speaker levels in it to match the subwoofer without eq. Levels were at 0 and I played pink noise in the XA2 and the reciever blew up and without any speakers hooked to the amplifiers. I use analog out to seperates. It is on repair and I will get it back soon. Since my subwoofer was playing -2dB bellow reference for me, I turned up the volume. My AVR quit working a day or so before my BFD arrived. 

I thought getting an additional subwoofer might help since even if they do fix my receiver (or I get a new one instead that does 15+ for subwoofer) that I will not be able to boost the LFE input with bass management enabled because my receiver defaults back to 10+ for analog because the speakers are set to large. An additonal subwoofer would allow +5dB boost I need for having my speakers set to small in the XA2 and possibly extened the lower extention in a vertical stack array. That is why I asked about a second subwoofer. I added two additonal filters to the topmost graph on this thread other than what REW had recommended. The large cut was -17.5dB.

edit: yes I use the computer-BFD-subwoofer for setup.


----------



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

Okay then, getting back to your question:


> Did it work? What could I do now?


That null is a big problem. Are there any openings in either of the walls close to the corner were the sub is?

Regards,
Wayne


----------



## thewire (Jun 28, 2007)

The other locations anywhere in the front of the room have the null also. I had bags of playsand stacked up ready for use and my builder took them and used them for paving steps bcause nobody wanted to purchase more sand or would help carry it down the hill. They took my leftover and tossed it. The 3/4 plywood stage is filled with some pink insulation. If sand will help the null, I could give it a try but it would be some trouble to accomplish. I have seen that being done before so I might have the motivation to do it. I'm not sure if that is what causes it.









The two lower corners in the rear I have not tested since adding more room treatments. The other side similar to the one shown has the entrance door next to it. This is where I origanally placed the subwoofer (pictured) using a crawl test, before there was any framing, located in this corner. I had compllaints in the back row that it was boomy there and the room treatment phase then began. I have not tested the location.









This is where the subwoofer was tested at the top of the thread with it located on the side of the room. I don't see a null at this location... so I thought it might have been a good location? Having a peak a few dB higher to eq is better than having a null right?


----------



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

Good information, but I didn’t see an answer to my question in all that. :huh:

Try moving the sub away from the corner down the wall between 4 to 8 feet (i.e., it stays against the wall), taking measurements at 1-ft. increments. Sometimes you can find a spot that will eliminate a null like that, yet the sub will still be close enough to the corner to get the benefits of coupling. If that doesn’t help, do the same thing down the other wall.

Regards,
Wayne


----------



## thewire (Jun 28, 2007)

Sorry I did not answer the question that well. I have tried this before on the wall by moving the mic in this thread and it looked like I was getting some valleys as a result. Second picture from the top.

right wall front and between right and center

I will try with the subwoofer located there instead to see what that is like.


----------



## thewire (Jun 28, 2007)

Wow. I was doing this all wrong. I set REW to do pink noise as DVE does and even applied the boost to my subwoofer as I do for setup. The results look like when I had my AVR. The light green in the graph is my subwoofer facing away from the side wall moving in 1-ft each time the measurement becomes darker. The purple color is on the right platform when I run out of room on the floor. I did not change settings in REW as I moved it.









I tried again with the driver facing forward away from the front wall in the corner. I also stacked a trash can full of boat batteries as heavy of the subwoofer to see what difference that might make. It looks like the null is because of my floor which is acoustically inert. How about that second third or fourth subwoofer then? :spend:


----------



## thewire (Jun 28, 2007)

Here is the corner with lots and lots of boost like my receiver used to do to the mains.

























additional info: THX switch setting is now 72dB at -33dB FS in DVE on my SPL meter.


----------



## thewire (Jun 28, 2007)

Was I supposed to recalibrate the SPL each time I moved the subwoofer? I don't see the lower extention in the corner..


----------



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

I’m confused. I thought here you had already measured all over the room and found the best location. Why are you doing it all over again? :scratch: Some of the graphs on the other thread, like this one are identical to what you’ve posted on this thread.

I’d say review your old thread, put the sub in the location that got the best response, and equalize.

Regards,
Wayne


----------



## thewire (Jun 28, 2007)

I guess I was waiting to see if anyone was going to recommend raising the level on the subwoofer again like at the other forum. :huh:



> Boomy subs == bad sound, corner loading your sub can cause this.. I think you should stay with 1 sub (maybe you need a bigger sub) multi subs will really complicate your situation right now.
> 
> What you reall should do is EQ your subwoofer. I have a BFD (feedback destroyer) that I run between my reciver and sub setup. It takes a bit to setup but is worth the time. Search around (here and goolge) there are some really good resources for EQing your sub. The EQ and test equipment will cost less that a 2nd sub an it will really imporve your sound.
> 
> ...


----------



## thewire (Jun 28, 2007)

This sounds good after three tries and while listening to sweeps and buzz rattle test in DVE. I demoed some material also. The subwoofer is in the center of the room again to reduce the null and some other issues I was having. It is with a standard house curve.


----------



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

Excellent! :T

Regards,
Wayne


----------



## thewire (Jun 28, 2007)

This thread already has some good info about my room. If nobody recommends otherwise I will just continue here for my second matching sub-woofer shipping soon.


----------



## thewire (Jun 28, 2007)

*Second equalization*

I'm having some trouble. I get errors that say there is to much noise and the only noise is from my computer at the subwoofer. I thought it was bad with one sub but with two it is telling me it effects the measurement. :sad:

First I calibrated each sub to 72dB in REW then it gave me 85dB with both subs. I adjust the settings to standard settings -12dB sweep and turn my volume to half. The SPL meter was previously calibrated for 85dB.









 Then I messed with some things to get close to 75dB. 









I skip the error messages such as 29dB to low and get this. 









How do I get past step 1? Are the measurements accurate if I am just turning down the sweep level and the output volume? When I measure with different settings instead and with an 85 target it says this (pictured bellow) when I measure but I can hear computer noise during the check levels. Is this going to be an accurate measurement if I have to turn down the volume on the computer so far? Measurements look like my old ones. :scratch: Would having my AVR help solve anything besides just having the filter? That is still not yet fixed. I can't seem to get ET5 to work also it just gives me a very flat looking response every time and I have to turn down the output to about 4%. I have been using the THX optimizer to make each level 75dB and my surrounds only go to 75dB at the lowest setting so I really need to get this 75dB target working I think. Anyone have any suggestions?


----------



## JohnM (Apr 11, 2006)

You are going about that the wrong way. The error message is warning you the measurements will be very poor which such low input levels, put the wave volume back to 1.000.

The most likely problem is that you have the SPL calibration wrong in REW. To check that, set your receiver to output a cal signal (e.g. using THX Optimizer) and compare the reading on your handheld SPL meter with the reading on REW. If they differ by more than 1dB or so you need to go through the REW SPL calibration to get the REW reading in line with the reading on the handheld meter. You can do this using the THX Optimizer signal, just click the Calibrate button on REW's SPL meter display, select "Use an external signal" on the REW "Choose Signal source" dialog and adjust the SPL figure in the REW SPL Reading Calibration dialog to match what your handheld SPL meter shows.


----------



## thewire (Jun 28, 2007)

That did work but there is bad news. While I was listening to the subwoofers alone I noticed that there is a high pitched buzzing/crackling distortion in the new sub. I tried switching out cables etc and even lowering the volume but it is definitely damaged. I wrote the manufacture expressing my concern. The finish is also different, it also seems to plays almost 10dB louder and I need to turn down the level considerably more than the other. The level problem occurred the fisrt time I tried to use it. It came with stick on rubber feet. :rubeyes: Do you think this would be something to do with break in time or does this seem like a damaged woofer? Seems pretty damaged to me.

Here is the new response without filters after doing as you instructed. :hissyfit:


----------



## thewire (Jun 28, 2007)

This is one from ETF5 with the 1/3 smoothing I was mentioning earlier. Not sure if it was ran to quiet or not but it seemed about the same as REW with the usual door flexing going on. :scratchhead: I played with the various settings and could only reproduce a very slight dip at 60Hz. I checked the results by adding a 20dB cut at 80Hz and it showed up much larger and very steep compared to the dip at 60Hz although it was not as much as the dip I see in REW at 60Hz. It also extends allot further down low. I think this is because the dip begins to come back in very quickly. The dip goes away when I sit down so I think it is the leather couch. Does the other software seem to be working correctly? I am not sure if I need a hand-held RTA or something else for pro installs. I don't know anywhere better to ask questions about this right now so I thought I would just through it out there. :hide:


----------



## JohnM (Apr 11, 2006)

Those do not look like valid ETF measurements, I'd say something is wrong with that setup. Not sure why you want to add to the confusion by using an additional measurement tool.


----------



## thewire (Jun 28, 2007)

JohnM said:


> Those do not look like valid ETF measurements, I'd say something is wrong with that setup. Not sure why you want to add to the confusion by using an additional measurement tool.


Thank you I thought that it did not seem right. I will wait until the next version of REW so I can use waterfalls (I have tried both views) again or keep trying with the current version. It sometimes works.

I am forwarding a copy of a UPS claim to the seller of my subwoofer and they are sending a replacement. It did not arrive palletized and there are dents in the box. :dontknow:


----------



## thewire (Jun 28, 2007)

The waterfalls are working again today but that is not what I have question about. Do you think I should place the bad subwoofer in the back center of the room and set it to reverse to the tame the null? It does not go away after I sit down now and moving them down the side walls does not help as far as I could tell from when I was not sitting.

The blue is both front corners and green is the right front corner and back center. I did not adjust the volume on the subwoofer after I moved it because I want to keep that setting sorry.









edit: It is about 3 feet off the back wall because I did not move the equipment rack where it is sitting.

My bad. Sorry for so many graphs. Here are the different mic positions up and forward a couple inches with the 25Hz extension. It was saying 22Hz for awhile the other day for some reason. That peak still seems to be there.


----------



## thewire (Jun 28, 2007)

Here is a photo of the damaged C audiovideo 12" driver. I could sit the extra sub inside of the riser also. onder:










edit: Correction. The driver is fine. The amplifier however is not fine.


----------



## thewire (Jun 28, 2007)

I have not gotten many complaints from the back row since I added bass traps but I thought I would give some eq a try for them back there. I have not yet installed rear traps on the back center wall that I think I will need and I will ask about this over at the acoustics area when it is time that I am able to get some. 

This is the measurements for the front row.










This is the measurements for the back row. :rolleyesno:










This is the averaged response and waterfall at all of the six seating locations. The filters are under 10dB.



















This is the result at the seat where my father sits at with the filters on.


----------



## thewire (Jun 28, 2007)

I have _tried_ to get the the most low output and less high output by the corner placement and even boosting the dip at 60Hz. While the corners were not seemingly all that bad the dip bothers me. I moved the subs along the side walls as far as I could and then moved them back towards the corners until I got a good result. Wayne said it was alright before so it must be good. Then I added a curve at 30Hz to 50Hz. My subwoofer is supposed to have flat anechoic response around 30Hz (in-room 19Hz). I would not have difficulties to setup the house curve later on.

Waterfall
I raised the SPL on the graph because I was still getting some error messages that the computer noise was around 60dB - 63dB each time I measured. Filters are added.










Filters










Left and right subwoofers 
My room is not symmetrical. The left subwoofer sits next to wall with rooms on the other side and inches from a doorway.










Result










Should I get more cables and eq the left and right separately? I think if there were a reason to that I qualify. Does it look bad? Is the eq to much? :sad2:


----------



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

What's your crossover frequency?

Regards,
Wayne


----------



## thewire (Jun 28, 2007)

My crossover frequency is 80Hz. After I apply the eq it still says the level in my THX optimizer is 75dB. I wish I knew how to predict the crossover. I added my right speaker to the test with the same volume level and did a sweep and they matched levels. Is the slope to steep? I can move the dip area from 40Hz up to 60Hz by placement. This was where the dip (or null) seemed to get the most improvement. This is what the placement looks like except the rear surrounds face inwards not towards the seating.










I could move them more towards the corners some to improve the upper range above 50Hz but the dip or dips began to get lower. I had to turn up the level on the subwoofers from around 2:00 to about 3:00 after moving them from the corners.

I found the amplfier on the damaged subwoofer to be bad and not the driver itself.

Crystal Audio is sending me a 2nd subwoofer for the price of one while I wait for my refund from UPS Freight. If I can figure out what amplifier to replace in the damaged one I will have four subwoofers. I was thinking of getting a 300W bash amplifier for it but I am worried they will not match. The subwoofer driver is rated for 400W and the original amp is 200W RMS. 

BestBuy just called me to inform me they are crediting the cost of my receiver back to me because it will cost more to repair it and I need to go the store.


----------



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

thewire said:


> My crossover frequency is 80Hz.


Okay - I guess you have your reasons for doing the house curve from 30-50 Hz...

After filters it looks pretty good, except that you might want to turn up the subs a bit.

Regards,
Wayne


----------



## thewire (Jun 28, 2007)

I found another 200W RMS subwoofer amplifier. I will have to see what happens. When I stacked two together on their sides in the center of the room I got 22Hz flat and +3dB gain before I changed settings in REW and applied eq. 22Hz is what I always hear when I run sweeps in DVE although the subwoofer starts moving sooner. If I stack them next to each other it might be better but stacking them vertical had no significance on the extension in places I tested.

If I line two in a horizontal array on each side of the room or stack them.....horizontally vertical, I might have something like +9dB and be able to use the 25Hz house curve. It should require about +1dB gain adjustment on each sub to make up for the loss of the corners and the signal being an extra -5dB low. That is my prediction. :daydream: The additional air displacement will certainly help that curve or the next. :flex:

Here are the settings I used for the above measurements. :innocent:


----------



## thewire (Jun 28, 2007)

These graphs will look very different now that one amplifier has no limiter. There is still about 9dB headroom after six filters. This is two subwoofers on the left side of the room.


----------



## thewire (Jun 28, 2007)

:surrender:

I tested the new setup this morning and it was really awful. It had to be one of the worst sub setups ever. That is saying allot also because my last HT had no room treatments or any eq. Problems were:

- Able to localize air movement
- No spacial envelopment
- Running amps hot
- Sounded very boomy
- No distinguishable improvement to achieving a flat response
- I would not listen to music like this.

I moved both subwoofers to each side of my left speaker and was able to turn down the volume again this time to an area that the subwoofers performs better at for reference level. I did a new calibration of the SPL meter using DVE and turned down the level of the one closest to the seating position to be 75dB. I left the one in the corner alone for right now but I think it is near 2dB higher. I remeasured and applied the new six filters that REW suggested. I checked with the 80Hz crossover on the new sub amp and there are no peaks above my crossover that REW wants to deal with. There are none for my mains also for that matter. It sounds much better now. :yay: Now I just need to treat that 60Hz area. This would most undoubtedly be the left walls for the equipment closet for which no insulation was put it by the builder. I just checked them. :explode: I will have to get some blown insulation or install some other kind when the walls get redone soon. :jump: This was a quick calibration because there are more subdudes on the way for the one in the corner and the next two will be here soon also.


----------



## thewire (Jun 28, 2007)

Can anyone make since of this video? It is a measurement on the SPL meter with C-weighting fast set to 70. The filters being used. The sweep is seen in the background of DVE and the Bass management sweep of the subwoofers. Does it look like there is a peak or it normal. :help:


----------



## thewire (Jun 28, 2007)

Looking again the meter was not shown in the video because it is flashing out of range. It flashes 80 from the 44Hz area all the way to 58Hz or higher then levels out.


----------



## thewire (Jun 28, 2007)

The video does not help so maybe this will. Here is a measurement of my soundcard with the C-Weighting unchecked and no calc file next to a -20dB FS pink noise with the settings that I used to measure the subwoofers. It is a loop back of my right channel









Here is the -20dB FS measurement sweep with the same settings. Please tell me this doesn't look right.


----------



## JohnM (Apr 11, 2006)

You can't really use a measurement sweep with an RTA plot, especially not when using averaging. Better off using the Pink Periodic Noise signal in the REW signal generator. You can set averages to None when using the Pink PN signal.


----------



## thewire (Jun 28, 2007)

So the dip is a coincidence? Let me ask this then because I want to be sure things are normal and it is not my computer. Maybe you could tell me what sounds wrong and what may be the cause please? When I use the RTA mode my mouse is really slow and stuttering. It crashes my computer occasionally if I run other programs at the same time. Loud ticking noises are coming from the subwoofer when it is plugged into the computer as loud as 64dB or more. When I run sweeps is the progress bar supposed to look smooth? It does not. I have some money to get a new computer now (thanks to loosing my receiver) and if my computer really is giving me problems, it is more a reason to look into a new one.


----------



## thewire (Jun 28, 2007)

Here are some computer pics. If I install my motherboard it will access out of date resources and cause my computer to have conflicts with Windows SP2.


----------



## thewire (Jun 28, 2007)

Here is the pink pn you requested to clear up my previous post and some sine waves for your inspection.









Edit: Sorry forgot to turn off averaging for the pink pn. New graph with no settings for the pink pn.


----------



## JohnM (Apr 11, 2006)

Those plots look fine, but you should change the mode from Spectrum to RTA 1/24th octave, the Pink PN line should then come out horizontal on a loopback.

The RTA mode is quite demanding for the processor as it is constantly analysing the data from the soundcard. You can reduce the load by using a smaller FFT length, but that will reduce the frequency resolution correspondingly. 

When using any audio measurement software it is best not to run any other programs, for the software to work correctly there must be no gaps in the generated or captured audio, programs running on your PC can sometimes place heavy demands on the PC resources and leave it without enough time to process the audio data to and from the soundcard, which will cause invalid measurements. 

Audio analysis also tends to use a lot of memory as it must generate and process large signals, If you were thinking about changing anything about your PC the first change I would recommend is more RAM. If you end up getting a new PC and it runs Windows Vista make sure it has 2GB of RAM.


----------



## thewire (Jun 28, 2007)

Use 1/24, alright. That should help. You are correct that it is to much on my computer. Just running my media player listening to the RT Info Podcast, browsing the web and leaving Photoshop open sets my computer at around 25% usage. I don't run many when I measure but I almost always have had my browser running during testing. I will try without that being open in the future for more accuracy. Thank you for the tip also on the computer.


----------



## thewire (Jun 28, 2007)

After I placed the next two subwoofers in the other corner things went wrong again. :scratch: The low sounds were not that audible but the room was rumbling and the door was flexing out of control. The mid bass sounding like murrroooo-ka-thump. I decided to try like the instructions said in the manual and place one at the center wall midpoint, one each of the left and right midpoint, and I shut off one. That gave me response from 25Hz up with a few dips. One was about 4dB bellow from 40Hz to 50Hz but it was very smooth looking one. I turned back on the corner sub again and the 25Hz area went up and so did the dip. The subwoofers are not positioned perfect for the test and I did not touch the volume on any except the corner sub with the non THX amp for which is pointing at 2:00. 

I used a -30dB sweep and the wave volume was so low I got error messages. It said something like 25dB low. I had setup the SPL meter using DVE again. :dizzy: It will take a long time to setup so I thought I would ask if this looks good to continue? There is currently a little bit of ringing around 50Hz but the subs are sort of hanging off some stands and the center is about 4 feet close.

Other ideas - I could also try the sub in the back corner also. Placing one on the back wall center midpoint will fix that 40Hz-50Hz dip also probably and might not require the 2.5dB boost and the 1dB one also. I would require a longer cable to place it there permanently and at the very least a new one to measure.


----------



## thewire (Jun 28, 2007)

My internet settings were vanished so I restarted my computer and now all my settings in REW are lost. My computer hates me. :heehee: I realized I can bring the BFD into this room and use a shorter measurement cable so I will try the back wall location.


----------



## thewire (Jun 28, 2007)

The subwoofers were humming from the non dedicated circuits just like my computer does. I needed to run an extension cord for each to eliminate the hum but I did this after the setup. There was no boosting required this time and the waterfall looks really nice. I will redo it again of course. I will need to change the outlets on the side of the room so they are on the same surge protector (inlet type) later on. Need to run one behind the screen in that conduit then also. I think it turned out well other than that problem and that it was rather difficult moving the heavy subs. I will post some new graphs later on but here are some photos and result for now. Sounds good.


----------



## thewire (Jun 28, 2007)

I moved the back sub and the front one to each side of my center channel and aimed the side ones to the back of the room. I needed to set my surrounds and the center channel to large. The front wall and back wall did not have the same effect and timing was off on the channels I set to large. Each subwoofer had the level to 75dB and then I equalized back to the 75 target with the house curve. The bass is much more detailed and quick. The LFE now shakes the door pretty bad still but isn't a problem right now unless you sit next to it. Might need to fill the inside since it is a hollow core steel door.

Here is the before and after. REW did not suggest reducing the peak at 70Hz but I decided to anyway.



















What do you think?


----------



## thewire (Jun 28, 2007)

Here is the right seat (green) with no front right sub on then left seat (blue) with not front left sub on. 









The RS meter at 90. Then I measure them each with all subs. :sweat:









green = right
aqua = center
blue = left

Then I ran find peaks in REW with the meter at 80.








I made manual adjustements and sent filters to the BFD.:blink:









Then I measure each location again with the meter at 80.onder:









From my 75 target I get 4dB gain from adding the new subwoofers (non co-located) after the larger eq cuts. I can adjust the output from the player as needed. :dontknow:


----------



## thewire (Jun 28, 2007)

I give up.


----------



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

I'm afraid I don't understand. You told us in Post #2, Post #22, Post #40, Post #52 that the sound you were getting was "good," "better" or "amazing." That's usually the point when people put away the mic and start enjoying their systems. :scratch:

Regards,
Wayne


----------



## kamui5785 (Jun 11, 2008)

He probably got too caught up in looking for that elusive straight line in REW

____
15Hz\_______________ 200Hz :daydream:


But seriously, I myself just tried out REW about a week or so ago, and I spent an UNBELIEVABLE amount of time with it trying desperately to get that silly line to be straighter and prettier :dumbcrazy:

The one thing I forgot to do though was to sit down and actually listen to the results :duh:

Thewire; my suggestion is to put your subs and speakers in the most optimal places you've found so far and just actually give them a listen! I'm willing to bet that when you listen to some of your favorite music and movies again, they will be a LOT more pleasing! :yes:

-Brian


----------



## thewire (Jun 28, 2007)

Thank you that is excellent advise. :T One thing I noticed when I took my BFD out of the loop for a true bypass was that the distortion in my subwoofers went away. I did a measurement with each subwoofer in a corner. I hooked up my original amplifier again and there are no issues except that I feel very guilty that I got two subwoofers for the price of one and partial compensation of shipping damages. I'm no longer using the BFD for now but this may be useful with an alternative crossover or subwoofer signal later down the road. The BFD and amplifier may come in use for another room as well. Calibration with AVIA revealed to me that DVE was not at fault for the damaged receiver, but rather it was the XA2 (DVD player) internal test tones that were 10dB (from the norm I am aware of) too high that caused the beginning of my problems.

I will continue later (not giving up entirely) on but for now I have to purchase a newer computer. I'm also need to rest and enjoy what I have as so wisely noted. My last HT had an echo in it when you talked for about 2 seconds and had a fireplace that rang like a bell so things could have been much much worse I know without any doubts. I am very satisfied watching my favorite films and enjoying music. Tweeking it now and then as needed will be a must especially to keep levels at an appropriate volume but nothing to extensive for a awhile. I also have some more studying to do anyway. I got the waterfalls working tonight so here is the example of what I found to be causing the troubles I was having, with the small speaker setting especially. All my speakers are set to small now.

Please keep in mind when looking at the example it is more typical to boost the level of a subwoofer signal, :innocent: this is a small room etc. It is not that I don't want to boost it I just can't right now. I was just messing around when I took this measurement and it is not even the original amp. I moved one subwoofer so it fired away from the door and only took a few inches in front of it. I think it was something like an 85dB target although right now I use an 82dB target, give or take an adjustment on my XA2 subwoofer level. I will have my new computer soon and look forward to using REW in the future.









Without BFD









BFD Bypass mode


----------



## thewire (Jun 28, 2007)

I did end up moving the subwoofers in the back of the room to behind each left and right seat and onto the steps, (nobody uses the steps back there, will be useless when the equipment is moved) and moved the front GIK bass traps to sit above the left and right surrounds. I had to do this for the Dolby surround demo on the AVIA disk a couple days ago when I was finishing that up. I read mentioned before that it was a good test for resonance etc so I took it seriously. The back row has really improved. 

Here is a result of the front and back row, then example of how the awesomeness of the cancellation occurs from the rear and front subs back there by looking at the front wall subwoofers and back wall subwoofers separately. :hail:


----------



## thewire (Jun 28, 2007)

*ok then*

When I examined the difference between loopback measurements several days I ago I discovered that for taking measurements that are lowered -10dB FS would cause the waterfall plots to look worse in comparing the plot on the identical looking measurement. Since not boosting the signal seems to add X amount of ringing if I measure in REW using higher signal than before when I was able to measure normal, I will assume it is correct to measure lower. :duck: If I am not mistaken the true result we are looking at would actually be -10dB FS since I do not boost the signal. That is what I listen at anyway. Much higher and I will need to start finishing the room. So here are new measurements on the new computer. I changed zero settings in REW. Didn't even calibrate the meter. All I did was take a loopback measurement that said 75dB and lowered that (offset) 10dB for my target. Correct me please if there is a setting I should be changing and how to change it.


----------



## thewire (Jun 28, 2007)

Subwoofers set 10dB low or is this REW? It expects the 10dB boost? This would mean that they would measure 10dB higher on DVE when using that method.


----------



## thewire (Jun 28, 2007)

Alternatively this could mean that my XA2 does the proper +10dB or +5dB boost and that the THX setting on the subwoofer reduces the level -10dB which would follow with the review given. That would mean that my other DVD player expects a -10dB reduction of the analog output. Because I have the subwoofer setup -10dB for the boost the XA2 would do, REW would measure 10dB lower. Gets confusing... Try reading about how to setup a XA2 analog. You will get an explanation from 3 or more variables without any explanation of these variables. Thanks I think I will stick with this theory since it goes with the review.

edit: summary

Dolby:

XA2 on DVE = 72dB limited bandwidth pink noise subwoofer +10dB +3dB gain = 75dB 
(85dB on subwoofer)

XA2 on AVIA = 82dB limited bandwidth pink noise subwoofer +10dB +3dB gain = 85db with subwoofer set 10 higher

REW = 65dB 

XA2 levels = 92dB noise on all channels +3dB distance gain = 95dB (Always will boost 10dB)

THX optimizer = 82dB-85dB limited bandwidth pink noise on all channels or subwoofer @ 85dB - 89dB if you prefer THX specs.

DTS and other Dolby: -4dB up to -10dB since Reference level may be -20dB FS to -27dB FS

- Safe area: -10dB

This explains why previews will be +10dB loud because they often are mixed at near -20dB FS. Those awesome previews people get all excited for would be because they are playing near reference level...

Thats how I make since out all of this unless of course there is more I am unaware of.


----------



## thewire (Jun 28, 2007)

Sorry corrected the DVE subwoofer calibration by adding "(85dB on subwoofer)". -10dB lower than 85dB in AVIA was -6 on my XA2 by the way. Now DVE = 85dB at the same setting of 0. Don't want to confuse anyone.


----------



## thewire (Jun 28, 2007)

My thread made the hot list? Hardly hot IMO but thank you.

I had my amplifier laying around and my old DIY subwoofer so I took it out and within 15 minutes I was up in running again. I upgraded all the available updates for Windows Vista 64 bit. It took a full day to accomplish. I went through all steps this time and anything I could recall reading on this forum that seemed to apply.

1. Took measurement of soundcard with -12dB FS sweep to my reference level @ 85dB where the scope looked best as I could possibly get it. Saved the image of the scope. It looked flat to only around 20Hz (fell off around 20K) and looked similar to some seen here . 

2. Saved the soundcard as the soundcard file.

3. Left C-weighting unchecked

4. Plugged in my subwoofers that were set reference level using AVIA, DVE, and THX Optimizer to the same level at 85dB.

5. Adjusted the output wave volume until it matched on the bars.

6. Calibrated the RS mic to the same as the REW mic which came back to 85dB.

7. Measured my back row.

8. Measured my front row. Clipping was detected so I lowered the input volume until it matched the bars again. Then I re-calibrated the mic to this time 89dB which is what my RS meter showed as. Re-measured and saved the scope image.

Did I do anything wrong? The output level on the wave was pretty low around .112 for both mesurements and the input level was .211 on the last one. I used a 32K buffer this time but the sample rate was still at 48kHz. Graphs are non-smoothed. Let me know if you need more info it's all saved with pictures and a measurement file as usual.









*Measurement results*









Soundcard Scope









Scope of last measurement after adjustments. Clipping was detected prior to adjusting the input level.

Sounds decent. Lots of LFE it seems like. Valid?


----------



## JohnM (Apr 11, 2006)

Look like good measurements to me.


----------



## thewire (Jun 28, 2007)

JohnM said:


> Look like good measurements to me.


:woohoo:


----------



## thewire (Jun 28, 2007)

Since I have my computer working and I have finished reading my chapters I wanted to read, I gave it another try. I am also taking Bryan's advise and using some info from the acoustics forum area. I did several things.

1: Moved all seats back - This is nice because the rear speakers are the same distance as the LCR. I have to reach over my rear row to turn on/off things. Not that big of a deal really since all that I need to use, and all I have quick access to is the DVD player. Nothing sitting on top of the equipment rack right now..

2: Moved all subwoofers. Moved the front ones into the front center of the room far from the corners. Moved the rear ones slightly closer to the corners right in front of the helmholtz resonators.

3: Checked the BFD again with the new computer. Looks good now on the waterfalls so I used it.

4: Moved my left and right surrounds back to compensate for distance changes. I had to build onto the stands to do this because someone wanted to put a wall heater right were my stands went! I built around it.

5: Moved my GIK 244 bass traps back to the right and left corners. My father didn't like the way they looked on the ceiling.

Here are the results now. The images total about 580K. Right I was connecting up my DVD player afterwards my laptop went off. I got the power cord and it said restoring last session when I turned it on and then my graphs in REW were back. The USB soundcard (Creative MP3) and the UNO MIDI connection (both recognized when plugged in. No install disk.) work very well on the new laptop with Windows Vista Premium 64-bit.










*Back left subwoofer*









*Back right subwoofer*









*Left subwoofer*









*Right subwoofer*


















*All subwoofers. No equalization*









*All subwoofers equalized*









*Equalized no smoothing*









*Equalized 1/6 smoothing*


----------



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

Looks good. For waterfalls, I recommend lowering the graph limit to 30-35 dB, because most rooms have a much lower ambient noise floor than 45 dB. This will let you see what's happening with the signal decay all the way down to "dead silence" (or as least as close to that as your room will allow). If your HT room is heavily soundproofed, you might even want to take it down to 25 dB.

Regards,
Wayne


----------



## thewire (Jun 28, 2007)

It is pretty soundproofed. The room is enclosed in concrete and with a thick steel ceiling above the tiles. The entire space is a square room but I built in a lobby and an equipment closet area on the right (correction left) side to tame modes. It is 2/3 underground. Sometimes I will walk out after a movie into a violent thunderstorm up to 93dB or more going off every couple seconds. It is quite the surprise after a relaxing movie. The projectors hush box fan I could disable but would require opening up the access, reaching in, the unplugging it from the outlet. It runs pretty regularly in the summertime as I have the thermostat to kick on pretty fast. I will try disabling that sometime and take measurements as you suggested.


----------



## thewire (Jun 28, 2007)

I am trying a few things differently now but here are some waterfalls with a 20dB floor. This is a measurement of a surround, the left center and right, and with the subs flat to 20Hz. The subwoofers are up front now and each set to the same level. The room isn't done and besides more treatments, there are many things that may rattle I really could do nothing about at this time. Until I can install the wires (soon I think) in my ceiling, I woln't be securing the tile anymore. The fan was off at the time of the measurements I think. Please tell me what you think anyway as it does seem to sound alright.

purple = center
gold = left
green = right
green2 = a surround
gold2 = subwoofers


----------



## thewire (Jun 28, 2007)

My room does not seem large enough to do quite so much and the subwoofers are not meant to be positioned in such a way. I moved the subwoofers to each corner and stacked my left and right on the front ones. I tested some demo material and setup for -10dB reference. After securing one tile I'm getting no distortion from the room. I'm ready to equalize now and much closer to being done. I will try and do a 25Hz roll off this time because 20Hz was throwing my seat back too far and it was distracting.


----------



## thewire (Jun 28, 2007)

*Square concrete room + zero budget*

Here is the new response then for now. I can't wait to see what 4ft deep diffussion on my back wall and more helmholtz resonators well do. raying: This is a -10dB FS target this time. You can see here the extra +5dB boost I have to do at my target to get to the 75dB one though in case you wanted to see what thats like. :dontknow: 










The fan was running this time.


----------



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

In the first thee graphs in Post #70 it looks like your noise floor is about 35 dB. Don't know what happened after that, it looks like something with some low freq energy got turned on...

Regards,
Wayne


----------



## thewire (Jun 28, 2007)

35 really? Thats not bad actually. Not sure what could be causing the 35dB. I don't even hear noise from the speakers in there when they don't have sound sent to them and I wasn't in the room. I was told however the average mic is not correct in the measurement of a NRC rating. This would I think be applicable to the Digital RS meter or I would test that using the appropriate scale and octive measurements. My projector running measures 50dB from zero feet away outside the hushbox but I had done that using a C-weighting. The fan is a FV-15VQ4 Panasonic whisperceiling model that runs .6 sones. It is above the hushbox but some sound leaks out the front. The extra sound pressure your seeing in the first measurement of post #70 is my center channel and the last was the subwoofers. The subwoofers also have a boost applied to get to the 25Hz rolloff. The subwoofers themselves are designed to roll off at 35Hz for room gain boundry compinsation. They are quite capable of 20Hz or even 15Hz but this is a feature built into the amplifier meant to deal with bass heavy smaller sized rooms. I simply corrected that as my room is slightly larger than spec. I checked distortion levels and they are still within an acceptable range. 80Hz is less than 1% distortion. Distortion is detected at around 20Hz-30Hz with no eq applied and this range adds about 1% - 2% more to that with the boost. It is considerably less than a typical subwoofer which may have as much as 10% since I start with 2%. It does not seem to hurt anything as far as I can tell. Keeping in mind this is what measures 75dB -20dB FS on my XA2 this time. The distortion meaurements I took with an 85dB target in REW. I have to measure 15dB louder in REW than my subwoofer plays in reality. I can choose to tell REW what I measure and avoid clipping best as I can, or tell REW its a 75dB or 80dB target. This last time however I am telling REW it is a 80dB target but in reality this is a 64dB target according to my copy of DVE. Here are the settings used in the one above except without my card in currently.


----------



## thewire (Jun 28, 2007)

You might have also seen the difference between having my laptop on battery and using the adapter. The second one was using the battery. Here is a loopback measurement of my soundcard using the identical settings I use to measure my subwoofers. The first is with the adapter and the second is without.


----------



## brucek (Apr 11, 2006)

> The second one was using the battery


A bit curious that you still show 60 cycle hum and its associated harmonics (120Hz, 180Hz) typical of a power supply, when only using a battery.

Either way, don't use waterfall plots to examine noise floors, use the Spectrum Analyser.

brucek


----------



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

brucek said:


> A bit curious that you still show 60 cycle hum and its associated harmonics (120Hz, 180Hz) typical of a power supply, when only using a battery.


Yeah, that caught my eye too...

Either way, thewire...


thewire said:


> You might have also seen the difference between having my laptop on battery and using the adapter.


...the residual noise from the computer is far, far below anything your previous graphs were showing, so it can't the culprit.

Regards,
Wayne


----------



## JohnM (Apr 11, 2006)

thewire said:


> I have to measure 15dB louder in REW than my subwoofer plays in reality. I can choose to tell REW what I measure and avoid clipping best as I can, or tell REW its a 75dB or 80dB target. This last time however I am telling REW it is a 80dB target but in reality this is a 64dB target according to my copy of DVE.


Can you explain what you mean by that passage?

REW has only one way of relating the signal level on the sound card input to an SPL figure: the SPL meter calibration, where you play a test signal and tell REW what SPL reading that signal level produces on your own SPL meter. REW then "knows" how the signal level on the sound card input relates to actual SPL and uses that knowledge to draw the lines on the frequency responses at the correct levels. That will remain valid as long as the soundcard input volume control is not altered and, if using an SPL meter connected to the soundcard, the SPL meter range setting is not changed.

When making a measurement REW does not care what SPL the measurement is at. All the software checks for is that the electrical level at the soundcard input is within a sensible range, not too low as that would give measurements with poor signal-to-noise ratio and not so high that the input is clipped, as that gives invalid measurements. The VU meters show what part of the input range is being used.


----------



## thewire (Jun 28, 2007)

brucek said:


> A bit curious that you still show 60 cycle hum and its associated harmonics (120Hz, 180Hz) typical of a power supply, when only using a battery.
> 
> Either way, don't use waterfall plots to examine noise floors, use the Spectrum Analyser.
> 
> brucek


Yes alright. 



Wayne A. Pflughaupt said:


> Yeah, that caught my eye too...
> 
> Either way, thewire......the residual noise from the computer is far, far below anything your previous graphs were showing, so it can't the culprit.
> 
> ...


In my line of work ("THX certified technition" or "THX proffessional") they suggest using a handheld RTA with 1/12 octive measurements or better. I also need to measure volts, and the NRC. The RTA should have a built NRC measurement. I was looking at one several weeks ago and it had it's own PC interface so the soundcard would not neccessarily be used. If not that I will need a very flat mic, mic preamp, new cabling, and probobly a new soundcard.



JohnM said:


> Can you explain what you mean by that passage?
> 
> REW has only one way of relating the signal level on the sound card input to an SPL figure: the SPL meter calibration, where you play a test signal and tell REW what SPL reading that signal level produces on your own SPL meter. REW then "knows" how the signal level on the sound card input relates to actual SPL and uses that knowledge to draw the lines on the frequency responses at the correct levels. That will remain valid as long as the soundcard input volume control is not altered and, if using an SPL meter connected to the soundcard, the SPL meter range setting is not changed.
> 
> When making a measurement REW does not care what SPL the measurement is at. All the software checks for is that the electrical level at the soundcard input is within a sensible range, not too low as that would give measurements with poor signal-to-noise ratio and not so high that the input is clipped, as that gives invalid measurements. The VU meters show what part of the input range is being used.


I thought you mentioned that measuring bellow a 85 target was good and to use an external source telling REW the correct SPL was advisable. I did not understand that to change the output wave SPL would be best. I simply told REW the target was 79dB when in fact it was an 89dB target. This then came to 79dB. When I measured the subwoofers individually I used a 75dB target that read 85dB on my meter. Mentioned in another thread they confirm the output from my player does not boost the signal and it is 15dB low. I was using REW to measure the natural output in SPL as determined by measuing a loopback of my soundcard, and noting that level in accordince with the subwoofers. If I am going to measure a 75dB target in REW with a 75dB target, I will later need to raise the level on all subwoofers and this will not give me accuracy going from one measurement to the next. 

Now I am using a 79dB target in REW and it is 75dB from my source using my THX optimizer 2.0 which is -20dB FS. I did this to look at the graph to see what telling REW it was louder than in reality might do, and because this would be the measurement I would have without a crossover, which I am unable to measure, and because it looks similar to my other graphs. :hide:


----------



## thewire (Jun 28, 2007)

With the newer settings I am still getting 105dB peaks and in excess there of. I had to disable the boost to the 25Hz because it was also to heavy. I'm going to see if I can more evenly distribute modes with absorption on the back wall.


----------



## thewire (Jun 28, 2007)

I found the problem with the noise from the current in my PC. The ETF5 software (or myself) had enabled the line in setting in the recording devices menu and this was causing feedback in the signal. When I would adjust this setting ETF5 would automatically adjust it back to a setting of 10... The waterfall now seen in the loopback measurements of my soundcard shows ringing from 10Hz and then quickly falls off but it is not nearly as high as before.

Here is the most in depth explanation of how I am trying to setup the measurement. I may need to use a different soundcard or replace my mic. My mic keeps freezing up now and then and I have to turn it off then on again.

Here are easy to see thumbnails enjoy all the clicking if you decide to see them. 


First I set the soundcard up. This was difficult and no matter how I tried, I could not get it to measure 75dB the same as my subwoofers. It also kept moving from a safe area to the unsafe area. If I went one click lower than the range was not as close.



This measures at 72dB on a sweep I did after disabling my meter calc file. The measurement looked like before. I saved the new soundcard measurement.


I get an error message when I begin to meausre. I ignore that. :coocoo:


I had arranged the subwoofers and set them all to the THX setting. This gives 75dB at -20dB FS in the optimizer on my disk. 


This here is what it looks like if I lower my input volume _after_ I have setup my soundcard so that the input matches the input level of my mic from the subwoofers.



I don't know what to think about that one so I put it back to where it was and continue on.. Here is a mesurement of absolute silence in my room. No equipment on or anything.


This is with the hush box fan and my audio on.


This is with my projector and the audio on.


This is without the fan on but with audio on.


This is the hum from the subwoofers when I disconnect the RCA cable. Thats got to be important somehow right? onder:


Air Conditioning running.


Vent fully open with air conditioning running. There is a speaker right in front of the vent but it does not block the air flow.


I did not have my mic carefully positioned to get the 75dB from each channel and the left and right may need slight positioning again, but here are the THX Optimizer 2.0 pink noise signals with 1/12 octive and no averaging. The mic is in the same location were the subwoofer was measured before. 


Here is the crossover sweep. Not to be accurate but just looking anyway.


Does anything look very wrong? I did these with the BFD power off but I used it to run the signal to the subs.


----------



## brucek (Apr 11, 2006)

> Does anything look very wrong?


Use the Spectrum Analyser, rather than the RTA to observe a noise floor. 

The RTA is better suited to dynamically measure periodic pink noise (with a rectangular window) while observing changes you make to positioning of speakers or addition of treatments.

The Spectrum Analyser has several uses, one of which is to simply listen to and evaluate background noise. 

Use no stimulus (but do have your levels in REW set as if you were about to take a standard measurement).

Set the mode to Spectrum Analyser, FFT length to 65526, set the Window to Hann, Set scale to dBFS, use a bit of averaging (maybe 2-4), and turn on the analyser.

Here's an example of my office system with some labels identifying a few items... 










brucek


----------



## JohnM (Apr 11, 2006)

thewire said:


> First I set the soundcard up. This was difficult and no matter how I tried, I could not get it to measure 75dB the same as my subwoofers. It also kept moving from a safe area to the unsafe area. If I went one click lower than the range was not as close.


A little explanation is in order here. The soundcard is dealing only with electrical signals. The levels of those electrical signals are shown on the VU meters in "dB FS", which means dB relative to full scale. Full scale is the largest electrical signal the soundcard can capture, on a consumer soundcard that would typically be about 1V. If the soundcard input has a maximum range of 1V and the highest peak on the input was actually 0.5V, that would appear on the meter as a peak level of -6dB FS, the dB figures can be converted back to volts using (full scale voltage)*10^(dB/20). If the electrical signal goes higher than the full scale level it gets clipped at the soundcard's input, you can see that clipping is happening if the VU meter for the input shows 0.0 dB FS, which is the highest level it is able to register.

The response of the soundcard is measured using the "Measure..." button in the Calibration part of the soundcard settings. When measuring the soundcard the volume controls are adjusted to make sure the electrical signal at the soundcard input is not too low, so that the signal-to-noise ratio of the soundcard measurement is good, and not so high that any clipping occurs. Ideally the input level when the 1kHz cal tone is playing would be around -6dB FS to -12 dB FS. Achieving this range would typically require the wave volume to be 1.0, the output volume to be 0.5 or higher and the input volume close to 1.0. These settings will typically _not_ be the same as the settings you will need when making measurements in the room, because then the input level depends on the SPL meter or microphone and how loud the measurement signal is.

Once the soundcard has been measured and the results saved as a cal file using the "Make Cal..." button we move on to setting the volume controls to allow good acoustic measurements. This uses the "Check Levels..." button. It is important to read and follow the instructions in the Help panel when carrying out this process. The first stage is to get the output levels set up so that the test signal produces an SPL reading on your (not REW's) SPL meter that is appropriate for measurement. 75dB SPL is a typical level to use, if there is a lot of background noise it would be better to use a higher level, if the background noise levels are low or you have sensitive neighbours a lower level can be used. Once the output volume and the volume control on your processor or preamp has been adjusted to get the test signal at the right SPL on your meter the input volume should be adjusted so that the input level on the soundcard is around -18dB FS. This is lower than used for soundcard measurement because we need to leave some input headroom to allow for the effects of resonances, which boost the signal and can cause clipping if the headroom is not sufficient. 

Three things look wrong in your screenshot of the Check Levels process. The output volume is set quite low at 0.126. It might be better for the output volume to be a bit higher and the volume control on your processor/preamp set a bit lower, but that is not a big deal. The input is clipping (the peak value, shown at the top of the VU meter reads 0.0dB FS) and the rms level (-9.0) is too high. Lower those levels by reducing the input volume. Finally, there are significant levels showing on the left input, which should not have anything connected to it. That suggests something is wrong, either an internal loopback has been generated by incorrect soundcard mixer settings or the left channel does have something connected to it which should be disconnected.

Once you have got the levels right, you should not change them. Calibrate the REW SPL meter by playing a test signal and telling REW what level that produces on your SPL meter. There is no reason to give REW a different figure than your meter is showing, that simply makes no sense. The meter calibration only needs to be done once, provided you do not change the input volume setting.



thewire said:


> I get an error message when I begin to meausre. I ignore that. :coocoo:


That is a warning that you do not have much headroom in your measurement. As long as there is some headroom (i.e. no clipping) the measurement will be good and you can carry on.


----------



## thewire (Jun 28, 2007)

:scratch: I looked at every mixer I could find. The signal coming from the subwoofer when I take measurements and play test noise sounds pretty bad. The more I lower it, the worse it sounds. It reminds me of measuring my mains. Now if you want me to turn up that output volume for a 90dB or more target, no problem. :bigsmile: I did a few quick sound checks with ETF5 and my soundcard at 20% and it sounded like King Kong just demolished my HT.:hsd: More serious however, the dynamic range of my subwoofer, and the calibrated dynamic range of my soundcard simply do not get along, and there is no preamp to adjust. The instructions say to set the soundcard up for the highest possible measurement and that is level of my subwoofers at -10dB reference, but the input is higher on my SPL meter. Is there any way to do this without more output volume? Lowering the sweep level is like lowering the volume but all measurements look less flat and the distortion begins. It is like the equivilant of playing of your walkman on a subwoofer, then turning off the bass enhancement feature.


Bruce the way I am familar with at looking at a NRC scale is 1/3 octive measurements. What difference does using a spectrograh make and why is it better, besides that it just looks more detailed?

Here are some more settings pictures.. Any ideas or is what I'm describing normal? Why doesn't anyone just measure from a subwoofer directly, one that has no crossover or fancy dials, and describe how it is done? This would make my life alot easier. :sad:


----------



## thewire (Jun 28, 2007)

I do not understand what .5 means. I see only settings with four digits in them besides the sweep. How might the left input be without a reading in it? Nothing is connected.


----------



## JohnM (Apr 11, 2006)

.5 is the same as 0.500. With nothing connected (i.e. nothing at all plugged into the Line In connector on the Creative box) both inputs should show peaks of about -90dB and rms of about -129dB. With a cable plugged into the Line In but nothing connected to the cable the levels would typically be about -73dB peak, -86dB RMS. With a -12dB 1kHz sine wave playing and the right input connected to the right output, the left will increase a few dB depending on how much crosstalk there is in the cable. Typical could be peak of about -66dB, but this will depend on how long the cable is and how well screened the channels are. To have crosstalk so high as to get -31dB on the unconnected channel would require an extremely poor cable, or some incorrect cable configuration such as using a twisted pair to carry 2 separate channels.

Investigate what happens to the level on the left input when the connection from the right output to the right input is removed.


----------



## thewire (Jun 28, 2007)

.501 goes to .500 while I'm not looking... :sneeky: I think I need measurement gear by your description unless there are settings elsewhere that elude me.


----------



## JohnM (Apr 11, 2006)

Worth checking what the balance is set to on the line in controls, but that might only explain the imbalance between left and right and not the overall level. It may be that the input is switching to a high gain (mic) mode when nothing is connected. To test that, connect a cable to the line in and just short across the other end of the cable and see what effect that has on the input levels. If that is the cause of the high level on the unconnected left channel you can just ignore it.


----------



## thewire (Jun 28, 2007)

That seems right. I don't hear anything that lead to me to think otherwise. I will check that later. 

I am now replacing all these amps in my subwoofers with better ones from my wonderfull rack of goodies. Also using a larger guage wire. They don't have a trim control and they play louder than the THX setting on my current amps. I get a 64dB reading from one from the back location and from the other one I have not yet modified in the front location is a 62dB reading at the THX setting. When taking measurements before the back subwoofers was much lower. The last time I did this I ran two 15" drivers off of one of these amps and it was enough to push them. They are MA-500 THX Ultra mono blocks.


My surrounds will all run off a stereo Denon POA5200 amp and the front left and right will not be bridged. Measurements from here on out have nothing to do with a control on my subwoofers. All I need to do is be very careful that they are not lower than my previous measurements.. Any lower and the subwoofer level will be lower than my other channels already set very very low. I could go maybe a couple dB lower. 

There might be a little more lower extention output to deal with but oh well.


----------



## thewire (Jun 28, 2007)

I setup all the subwoofers and my amplifiers and did some demos. The target read 73dB on my meter but there is furniture all over and tools in the room. I ran some larger guage wire to the smaller one since I thought this would not matter much.. The back subwoofers were clipping my amps like crazy. I took the wire and also tried a smaller guage wire, running the signal through an amp with volume control and also tried a pass through from the RCA. Those did not help. I took the driver out and connected the larger guage wire directly to the speaker, and now the amp does not clip. I hope this works for my other rear subwoofer. Some changes that I notice to the sound are:

1. The ports do not flutter with air. The room does not flutter in this frequency range.

2. The subwoofers seem to go lower.

3. My room is not rattling now.

4. No high pitched distortion. It had sounded like an electronic kind of buzzing.

Stay tuned. :bigsmile:


----------



## thewire (Jun 28, 2007)

This is the best I have heard ever. It also sounds like it is...expensive. :spend: It is 76dB target in DVE after filters. I took you advise and raised the output volume some. I had to turn down the input level. I can adjust the level of the output on the XA2 for the subwoofer. I think I will also create another set of filters.

Measured & filters





Results..


----------



## JohnM (Apr 11, 2006)

That is looking very good. From the plots looks like you are putting in a boost of 9dB or so around 25Hz. You could alternatively try moving the REW target line down so it is closer to 73dB and lines up with the flat portion of the response there, use some more cut in filters 4, 5 and 6, ditch filter 2 and maybe filter 3 and if you keep filter 1 use a lot less boost. Then just raise the volume of the sub a little bit to get back to where you are now.


----------



## thewire (Jun 28, 2007)

Yes I would have to agree. 90% of the time that setting isn't going to work. Not because it doesn't sound good but rather some movies will be rather heavy. That is what I do to get reference level. Not sure about what the SPL output is but bass feels very tight. I thought this might be easier than doing alot of cuts. I will try and setup another set of filters using your instruction. My next set of filters will have no boost at 25Hz because 30Hz is plenty probobly but I will see what it's like. Hopefully as I look for a lower target, the frequency in the upper range will still sound as good.


----------



## thewire (Jun 28, 2007)

It doesn't look as bad as I thought it would. 



I think these may work alright. I'm going with Wayne's minimal eq filters this time.


----------



## thewire (Jun 28, 2007)

This is all analog. The only thing digital I am doing is the BFD. There is no turning up the subwoofer higher than I had it before. This = 65dB or 64dB for the mains. They = 75dB in the THX optimizer. With this setting I had 76dB in DVE and so the subwoofer was playing higher than the other speakers. I had not adjusted them higher when I was doing that listening test earlier. I can raise the level of the mains less. My last reference setting was actually a 72dB target and it was quite enough actually. It is pretty loud when I use a 75dB taget and the bass measurements will acutally read 78dB if I raise these settings to around -1. Although I would like to do that boost around 50Hz it is still somewhat in a purist form by what some may consider an unaltered signal. :dunno: Not sure about these extra surrounds I am using. Off topic, but I will probobly be replacing these towers I have lining the walls with some mountable dipole speakers. If I don't buy them, someone else has already offered to do so.


----------



## thewire (Jun 28, 2007)

This is with the subwoofer turned up and other speakers up less. No boost on the sub from the BFD. All channels measure 75dB in the Optimizer 2.0. I welcome any opinions on this or suggestions. The subwoofer measures 71dB otherwise at the highest setting in the XA2. Turning down the subwoofer doesn't seem to do much in the large setting as far as LFE goes but that is just my observation. Might be to much to handle War of The Worlds in DTS or similar.


----------



## thewire (Jun 28, 2007)

thewire said:


> This measures at 72dB on a sweep I did after disabling my meter calc file. The measurement looked like before. I saved the new soundcard measurement.


Each time I had started REW with my new soundcard on this computer and my other one I would have to select my USB driver in the settings window each time before I began. I checked my debug file and it keeps saying everywhere there in no control or any drivers found. I went and updated the soundcard driver to the Vista version. I disabled all of the bass boost etc features in the Creative enhancements and setup the speakers and checked the levels. I setup REW to use the new driver and each time I load REW it will remember to use the card but I now have lost control of the output volume and the input reads low. I have set the default input in Windows to be line-in as the default device. All others are greyed out except for in output. They all say 100. I then took a new soundcard calibration and REW was able to make the calc file and measure the card. I took a sweep and it was flat but I was not able to select any higher of a frequency then shown. I did not get any error messages except what about this? I looked at various settings and the driver appears to be working on my computer.

Channel: Right
Input volume: 1.000
Input RMS target: -12.0dB
Actual RMS at 1kHz: -21.7dB


----------



## JohnM (Apr 11, 2006)

When REW is running right click the volume icon in the windows system tray and select "Open Volume Mixer", make sure the volume slider for Room EQ Wizard is set to 100. Use the nornal windows volume control to adjust the output level.


----------



## thewire (Jun 28, 2007)

Yes the mixer says 100. I also tried at 50 and the measurements look the same and are at the same level of 79 when I do a loopback sweep in REW with the calc file unloaded. When I set the level to 50 (after using the 100 to setup the card) I get an error message that it is to low and the dB goes to 73.5.


----------



## thewire (Jun 28, 2007)

As a heads up for members using this card with the Vista driver you might want to try speaking into the mic to check if the monitoring is on prior to measurements or the waterfall will look slightly a mess.

Here are the latest to document my progress. The four subwoofers are up along the front wall with room for the ports in back. I have moved some room treatments in my ceiling. I will be doing more soon and these are without equalization. I am aware it is not the best method to base room treatments on eqalization. The equipment closet door will be replaced with a wall and a new leavered door will go in the lobby. Four seats are in the front row now and two in the rear. 

http://www.flickr.com/photos/tns29/sets/72157606558023741/detail//


----------



## thewire (Jun 28, 2007)

The RS digital meter calc file was not loaded in previous measurements. I corrected these and uploaded the images. It took me awhile on this slow connection.


----------



## thewire (Jun 28, 2007)

The closet door is gone and there is a new wall. There is alot more insulation and the GIK 244 traps are now on the back wall. Those Helmholtz Resonators finally got some insulation. The front part of the room is outdoor carpeted for about 6 feet to the corner traps and the panels are moved as well. There is four seats in the front row and two in the back. I will test in the equipment closet instead of while in the room soon but here is an update. No eq or smoothing.

Spectral decay of a seat in the back row to give an idea of how good the other seats are now. :bigsmile:










All seats measured.










I may do some final tuning of the room once I get into the equipment closet to measure.


----------



## thewire (Jun 28, 2007)

I think I have it about covered on the bass side of things now just tidying up. I added some absorption to the ceiling and next on my agenda after replacing one ceiling link runner (was to short) with a newer one of some extra I have, will be to start measuring the mains and each other location in the room to get an idea of what kind of equalization may help, or if I may need to move the subwoofers. Here is my last measurement I did. I'm pretty satisfied with the results. I have since added some spacing to my reflection panels. I was watching a movie trying to figure out what to do and I forgot I was supposed to be listening to the subwoofer, and I could not figure out where it was. :scratch: :huh: 

This is not a standard graph as I used an 85dB target. According to DVE it was an 80dB target when I was holding the mic and I still get 105dB peaks. It is also 105dB peaks in the back of the room where I had expected it to be louder. :huh: More updates soon.


----------



## thewire (Jun 28, 2007)

I fixed some loose ends in the HT that were not nailed down and did the eq. I am very pleased with the results and I have achieved my personal goal of 20Hz extention, under 600ms, with a good flat response. :yay: For those that prefer a house curve there is one in the back row still. Moving the subwoofers there does not seem an option as we want it to look best. I went though some effort to get the surge protector, and wires black and it was approved upon. Is this considered an REW success story?? If so, is this the first to be done in what started as a square room?


----------



## thewire (Jun 28, 2007)

This was taken with my power adapter on my laptop. There was a high pitched noise but it wasn't too much. The hush box fan was running also. Is this why there are no opinions?


----------



## thewire (Jun 28, 2007)

As soon as I went to remeasure there was a large amount of feedback connecting the equipment. The soundcard device name in REW settings read 2-soundblaster and the line in for the soundblaster selection became master line-in. I checked the different settings in the mixing console and the active input device read mic-in. I disabled this and selected the line-in as my default input device. This did nothing to disable the monitoring so I went to the windows restore and tried to do a system restore. Each time I tried it said volume C corrupt and the check disk would not work on reboot. I re-installed the drivers I downloaded and it gave me a message a console other than creative was present and it would override it, I said ok and installed, then rebooted. This is the second time installing the drivers. Then I get the card working again and in REW. I go to the mic and blow into it and I hear the noise come from my subwoofers. I went into the recording window of the Windows console and unchecked the box to give exclusive control to other programs. This disabled my ability to use REW so I enabled this again, and restarted REW. Then I tested the mic by blowing on it again and there was no noise from the subwoofers. I went to my electrical box and turned the breaker off for the projector and lighting system in my HT. The only thing that had power was my laptop and the equipment on the dedicated circuit. The noise coming from the computer caused by the power adapter of my laptop had stopped making noise again prior to killing all the power. I also turned off the upstairs AC, checked the other AC, and turned down the hot tub so it stopped pumping water. Here are the new results. There is no more 20Hz maybe. onder: That was probobly some bass boost. I did not recalibrate the mic, and instead of reading 80dB as before the eq, it read near 78dB in the red numbers. I was getting quite stressed and did not feel like walking back in the fourth from rooms to read a pink noise using complex or self starting menus on my player with the DVD's at 3AM in the morning. The mesurement still looks very similar so I checked the noise level of the room also. I hope the experts here will make note of my complications for others that may have similar issues.:innocent: Otherwise it may look more like my previous post. :yes: Not sure if following that procedure will actually fix it though. :huh:


----------



## JohnM (Apr 11, 2006)

Looks good, ringing is well controlled apart from the bit around 20-30Hz, which is probably not a problem. The low end overall from about 60Hz down looks a bit low compared to the 100 - 200Hz region, but which is right depends on how things look above 200Hz. Could well be a good compromise for the various seating positions.


----------



## thewire (Jun 28, 2007)

I'm not sure exactly how to calculate a difference that adding a distance setting will make. I plan to have some panels on the front wall which might help. I already have these sized for Bryan at GIK or I may make some myself, but the funds were not allocated in the recent changes. This is what my mains look like after some positioning I did. I'm not sure if I made matters better or worse, as I am unable to look at anything more than just a direct connection to my amps with a Y-cable. The ear position is actually a few inches higher than measured for myself, and I pointed the mic at the top of the screen this time. 400Hz and up doesn't look too bad. This added photo might help to give an idea of what I'm dealing with. This is the only way I am sure to measure 200Hz and up. I had not noticed much if anything needing to be adjusted, but went ahead anyway for these measurements. If I did something incorrectly please let me know. I have not adjusted them by ear or measured the back row yet.


----------



## thewire (Jun 28, 2007)

I don't think I like the ringing between the 20Hz - 30Hz region. My couch keeps shaking for more than a second and I don't even hear anything. :sad: The output also seems a little low even for being set -10dB reference level. What I could do is place them in each corner and raise my front row to the same height as the back row. This fixes the dip at around 60Hz, raises the output, and eleminates the peaks above 80Hz that I measure. I did not notice anything out of the ordinary above 80Hz. Also in the front row when we recline our feet are like 1 foot away from the subwoofers, and it makes my shoes vibrate alot which is kind of distracting. We are doing a redesign of the riser anyway, so this isn't much of a problem, however for the front of each seat in the front row will be at eye level of the screen, and the center channel out of eye sight, unless the front row is reclined, which is 90 percent of the time. I'm not sure the rear row could be raised any more although it has been proposed before. It might be something I look into but this would put the distance when standing to less than 6 feet clearance at least and it is already at 6' 6". What do you think?


*Measured and eq predicted at worst seating location:*









*Waterfall before eq at worst seating location:*


----------



## thewire (Jun 28, 2007)

I told REW that my previous measurement of 79dB was 75dB. After I moved the subwoofers to the corners it read 80dB. I did a demo like this and it sounded the best I have heard so I think that changing the seating postion vertical will be what I will go with. Bass across the front of the room is now very smooth on each side now that the ceiling has the insulation in and the partition wall went in. The right corner does not sound boomy anymore. I'm not sure about building that stage they want.. The rear subwoofers can be installed into the Helmholtz resonators partially as they are now filled with insulation, and plenty large enough for the ports. I observed about 25% more impact of LF when sitting slightly higher.


----------



## thewire (Jun 28, 2007)

Testing to see if upgrading to some new subs to be placed in the rear corners, I have enclosed the two rear subs in the decorative & functional platforms/ Helmhotz Resonators. The are sealed with very little insulation inside and I am trying to find on these graphs where the resonance is but having no luck. The areas are not entirely sealed at the entries, and keeping in mind there are holes in the platforms & the subs are louder, it is still at reference level. The subs are aimed towards the center of the room sitting in the corners inside, and the front aimed into the length of the room in the corners. Most of the insulation went to the ceiling. I'm not sure what to think. The back wall is basically sounding like a really low tuned sub, and it shaking the rear row like jello.
It is the only way I could get one out of the way of the door, and in the corners at the same time. These are without eq. This time I'm looking mostly at the good seats cause I'm curious how they look now that I feel walls shaking. I'm not sure if they go there at all, with a hole cutout and passive amps would be better or what. Filling them with insulation makes the SPL drop quickly. Removing most of my insulation from the Helmholtz Resonators and placing subs in them really hurts the back row response.




























I started a thread on this subject in the DIY sealed or ported subwoofer forum.


----------



## thewire (Jun 28, 2007)

I corrected the graphs as those previously had some +3dB boost in them from a missing sub. I keep getting distracted by my meter freezing up. When it freezes it measures at around 1/3 dB for some reason and reads "low" for everything until I reclick the dial off and on again. Then I also had left it on after attempting to kill the power to a hush box fan for testing, which was a failure.


----------



## thewire (Jun 28, 2007)

Next I will try placing two subs collacated in the front left corner, and two in the back right corner. This will work I think as long as my father does not sit in the back row. I'm hoping it will reduce the ringing at 20Hz - 30Hz such as placing them in each corner as shown bellow. Wires would be hidden without any additonal effort as I have cables ran in the wall near the rear location, and they are at the other corner already. Outlets are also at each location. I have never tested these locations because this means, I'm out of ideas.


----------



## thewire (Jun 28, 2007)

Looks much better. Can't wait to add the new insulation to the Helmholtz Resonators tommorow..rather later today. No changes to the setup done. No new SPL calibration done. 

*Waterfall no eq*










*Measured and predicted*










*Waterfall after eq*










Not as impressive as some of the other locations measured but works aesthetically.

edit: Forgot to mention this is my mono amps powering the subs only. No level controls in use again.


----------



## thewire (Jun 28, 2007)

It looks like I'm about done. The HT sounds and feels very natural like being at the movies. A list of things to be done that I will complete next month (planned) is to repeat the proccess of adding back panels to my tiles, and duct taping them while filling them with insulation. After we watched "Sunshine" last night on DVD again, it obvious that the method works 100%. There were no rattles in the front of the room where treated, and a huge amount of rattles in the back where not. Might also clean up that 40Hz area by treating the front wall but not sure..

Here are the results of filling the back Helmholtz Resonators with insulation. Notice how it looks much more flat now. I used a 80dB target and it tracks the 80dB target near perfectly from 30Hz up. With my small setting on my player, it is a 75dB target before eq and 80dB with large before eq. I need to do some touch up sealing on the subs since I had to fight with them awhile to get the amps working again last night. I think it was a loose connection on one of the drivers. I think I may very well have outgrown this thread title. :yes:



















You can see an animated gif of a measurement for each bat of insulation going in here if you want..

http://www.flickr.com/photos/tns29/2854199735/sizes/o/


----------



## thewire (Jun 28, 2007)

Still making some progress each day. I found the front left corner and rear right corner good for low frequency effects, but the subwoofer transients and an even response across the front row was no good. I am instead going to try plan B as recommended by a member of the family. I placed peices of carpet over the front subs, which helps tame the reflection off the screen. I also aimed the subwoofers from the directly next to the side walls up front to the center of the room evenly spaced in a very subtle U shape. I am trying with a 100Hz crossover, and so far have had excellent results. I checked my target in DVE and was still at 78dB. I then filled my stage with more insulation and added some more pink also to the upper left corner I stole from the rear of the room. I have had very slight results with pink (insulation) in the upper right corner, with all foundations surfaces concrete or steel, but not enough worth my time to add more there as I have noticed in the past. I think to make any kind of a dent on the right side it will require some heavy Roxul 60. The ringing is not noticable at all on the left side of the room where I have been listening to, and when playing a 30Hz sine wave, the ringing seems noticable if I get up out of the seats and stand in the front of the room next to the walls. Otherwise it isn't to bad, I can now hear sounds that move the seats. Still a ways to go but having the 20Hz in the front row also is very nice. I will try and get these equalization filters to match more uniform across the front row next. Here is an example of one in about 15 minutes. I really like how the spectral decay looks in one of the seats. 

Before filters











A spectral decay I like. This one was under 600ms on the waterfall.











After filters. Most are around -2dB or -4dB but there was one around 80Hz pretty high at -10dB. That is the drawback to improving it in the back row, which I will have to check again sometime.


----------



## thewire (Jun 28, 2007)

Been spending the past few days adding tape to the edges of my ceiling tiles and the back panels on them. Also removing the extra ones and moving those to the rest of the room. I will be filling the ceiling later with acoustical cotton. There is tons of bass up there now just waiting to be treated. I'm going to start with some Quiet Batt and least two 5 1/2" thick 24" wide and 24' long total of the 8' bats, but it is rather expensive. Decided to check on things before I finished the last dozen or so in the room since pressure in the ceiling seems to have doubled if not tripled or more.

Here are also some power compression measurements I tried doing also. I started measuring the difference of adding 5 in my mixer after the 50 setting at 95dB, then measured some lower ones, one of which read 75dB on the meter but didn't show on the input in setup. All I changed was the mixer level and the input level was at around 3 with the meter dial at 90.:hide: I have no idea if that is how to test power compression. :huh:


----------

