First Graphs...

[rolyasm]

Allright,
I have calibrated and measured and I think I have this almost under control. I am going to post my graphs to make sure everything is looking alright. The first picture is my soundcard calibration with my mic cal (I think that is the to line). The second graph is my left channel response, the third is my right channel reponse, and the last is my left channel response with the impulse response controls. Not sure what the last graph is supposed to look like. Everytime I applied the Impulse Response Control and set the pre ref to 125, my graph turned into a bunch of very close vertical lines. I will let you respond to this before I ask any more questions. Curious if the soundcard looks okay and how bad the response graphs are? Also, it doesn't matter if I run the left or right channel measurement, all four subs fire. Is that weird?
Roly

[brucek]

The first picture is my soundcard calibration with my mic cal (I think that is the to line)

I don't really understand this statement, but the soundcard cal in the first graph looks perfect except for the squiggly line I've highlighted. I have no idea what that is. Hopefully you saved the soundcard file.




You show 5 graphs. The first is the soundcard response. I take it the second graph is with the soundcard loopback in place and you're checking for a flat response to verify the soundcard calibration went correct.

You've lost me on the next two graphs that you call left and right channel? It is the sub you're measuring?
I do remember you had a stereo 2500 power amp driving your 4 IB's. You split the signal from the BFD and fed both channels. If that's the case then the sub out of your receiver is a mono signal that you check as one channel. All 4 IB's will play in concert.
Select the SUB tab and do the response - no LEFT and RIGHT.

Remember to reset your GRAPH AXIS LIMITS each time you measure to return to the default settings. The axis is incorrect on your left and right graphs.

Everytime I applied the Impulse Response Control and set the pre ref to 125, my graph turned into a bunch of very close vertical lines.

Yes, but that's the Impulse graph - you now need to return to your response graph. Select View and return to Filtered Adjustment screen where your graph is shown..
You don't need to provide the Impulse response graph. Once you take a measurement simply set the window to 125ms and return to your graph and that's it.

brucek

[JohnM]

There's definitely something wrong with the mic cal curve, maybe attach a copy of the mic cal file and we can see what is going wrong with it.

[brucek]

Yikes, perhaps that squiggly line is Rolys ecm8000 calibration file. Not good, for sure.

If so, you have corrupted the file somehow. If you had your ecm8000 professionally calibrated, then reload the file (and perhaps post it here so we can see it as John says).

You should read THIS thread that Sonnie posted and perhaps download his ecm8000 calibration file that he has provided there...

brucek

[rolyasm]

Hello,
Yes, that squiggly line is my mic cal. I just reinsterted the cal files and came up with the same thing. Here is a paste of the cal file.
As far as the left and right measurements go, just to the right of the SPL on the REW are two tab circles listed as right and left. One of them is checked at all times. Is this not supposed to be this way? It looks built into the program.
10 2 0
15 2 0
20 2 0
25 2 0
30 2 0
35 3.08 0
40 2.5 0
45 2.5 0
50 2.5 0
55 2.5 0
60 2.5 0
65 2.5 0
70 2.5 0
75 2.4 0
80 2.3 0
85 2.3 0
90 2.4 0
95 2.4 0
100 2.4 0
150 2.5 0
200 2.4 0
250 2 0
300 1.7 0
350 1.7 0
400 1.5 0
450 1.3 0
500 1 0
550 1 0
600 1 0
650 0.9 0
700 0.9 0
750 0.8 0
800 0.6 0
850 0.4 0
900 0.4 0
950 0.4 0
1000 0.4 0
1500 0 0
2000 0 0
2500 0.4 0
3000 -0.4 0
3500 -1 0
4000 1.2 0
4500 0.8 0
5000 0 0
5500 1 0
6000 1.6 0
6500 1 0
7000 -0.3 0
7500 0 0
8000 0.3 0
8500 -0.8 0
9000 0 0
9500 0.3 0
10000 0 0
11000 1 0
12000 1 0
13000 0 0
14000 0 0
15000 1 0
16000 0.8 0
17000 0.6 0
18000 0.4 0
19000 0.4 0
20000 0 0
21000 1 0
22000 2 0



Thanks

Roly

[brucek]

Here is a paste of the cal file

Yeah, I see the problem - that file is nuts. The file is providing frequency/level/phase without proper decimal points (where did you get this file) and seems to be quite crazy. A microphone just doesn't have that form of reponse.
You should use Sonnies file here and I feel it will provide a better representation of your mic - see how smooth it is in his thread on the subject.. Save it as your mic.cal file

As far as the left and right measurements go, just to the right of the SPL on the REW are two tab circles listed as right and left. One of them is checked at all times. Is this not supposed to be this way? It looks built into the program.

As I said, simply use the SUB tab and do your measurement for the 4 speakers.

brucek

[rolyasm]

I got that file from two different sources, most recently at AVS forum. I am glad you have discovered a problem. It gives me hope. I will paste a new pic to make sure the new file looks alright. As far as the axis, I set them to L 15, R 200, Top 105, bottom 45. Correct? So I don't do that once, but everytime I measure? Also, does it matter if I apply that before or after the reading? Thanks a ton. I am on my way to measure again.
Roly

[brucek]

So I don't do that once, but everytime I measure?

Yes, the axis limits are only preserved as long as the most recent measurement you have taken are inside the graph axis limits of the setting. No big deal - just look at the graph, and if it's not at the values you have set in the axis limits, then make it so.

got that file from two different sources, most recently at AVS forum.

Oh my gawd. AVS? , are you serious ? !!!!!!........ Use Sonnies file and you'll be fine...

brucek

[rolyasm]

Oh wow,
Just did another measurement. The first graph is listening position, the second is near field. Not much difference. Is this an indication that my sub sucks? I sure don't have much SPL under 30Hz.
Roly

[brucek]

OK again!!!!!, you don't have the Graph Axis Limits correct!!!!!, so change that so I can properly evaluate.

Did you use Sonnies mic.cal file ?

brucek

[rolyasm]

Yes, I did use Sonnie's file and I posted a graph of it a few threads ago. The mic cal response is the flat line that jumps at about 5k Hz as you move right. I guess I am not getting the Graph Axis thing. I just reset it and will try another graph. If it doesn't work, you can shoot me, please.

[brucek]

If it doesn't work, you can shoot me, please.

Hehehehe, good one Roly...

OK, that graph has the correct vertical and horizontal axis. Good job - now we can evaluate.

As you say, it is a bit challenged in the bottom end. It drops off rather quickly below 30Hz, which is not what you would expect from a 4 driver IB.

I was wondering about your hookup in regard to your 2500 power amp? Have you seen this thread from Chrisbee who has the same equipment basically?

brucek

[rolyasm]

I am on my way to that thread right now. Just out of curiousity I meausured a 10" Polk and an Earthquake 12" MKIV. Now I know they are not all calibrated, so what I did was to use my SPL and change the volume on each sub until the SPL read 80. That way the subs volume was at the same level as my 4 subs. Then I ran each test seperately. Not sure if that even works, but the response is interesting. All the graphs are very similar. The Polk and Earthquake are powered, both Xovers at 80. Could it be something in my hookup that isn't allowing me more output? First is Earthquake, then Polk, then mine.
Roly

[brucek]

so what I did was to use my SPL and change the volume on each sub until the SPL read 80. That way the subs volume was at the same level as my 4 subs. Then I ran each test seperately. Not sure if that even works, but the response is interesting.

Now you're getting it........ good job..

Could it be something in my hookup that isn't allowing me more output? First is Earthquake, then Polk, then mine.

I don't think it's your hookup. It seems correct. The room determines a lot of what happens...

The Earthquake looks the best for sure. Look at that Chrisbee thread I referenced on the 2500 hookup and try again...

brucek

[rolyasm]

Perhaps a solution. Reading the 2500 amp manual, I notice some dip switches on the back. Currently I have the low cut filter set to 50Hz. It has a 30 Hz option, which the manual says is better for subwoofers, but I can also just shut off the low cut filter. I think this may be the big problem. Looking at my graph it plummets, right at the 50 Hz range. If I disengage the filter, it states that "frequencies below 5 Hz are cut to prevent damage." So should I try the 30 and see what happens, or just turn the thing off?
Roly

[brucek]

Currently I have the low cut filter set to 50Hz. It has a 30 Hz option, which the manual says is better for subwoofers, but I can also just shut off the low cut filter. I think this may be the big problem.

For sure.......................... shut the low cut off.....

[rolyasm]

Okay, I shut of the low cut filters. Good news is I guess it shows a little higher output at lower frequency, but the overall response doesn't look as good to me. So here is the graph with the low filter off in comparison to on. The first is without filter, the second is with low cut filter. The third is a measure with the mike close to the subs, near field. I guess this is a more accurate reading if comparing to the Polk and Earthquake, since that is how I measured them.

[brucek]

Yeah, that looks better.

I would stop doing the near field and do your measuring at the listening position.

Let's discuss graph 1, which is your IB sub with the filters off - leave them that way.

If you increased the overall level of the measured signal, it would be quite good except you'd have a hump at about 5oHz. Fine, that can be eliminated with a BFD.

Go ahead and do a measurement of your IB at the listening position and set the Measurement level at about 90dB instead of 80dB. That should track your target except you'll have a peak at 50Hz......

BTW, is your BFD ready to rumble?

brucek

[rolyasm]

Here is the graph at a 90 dB range. To make sure I did this correct, I calibrated the REW for an 80dB reading, but my SPL was registering 90dB. So I fudged it 10dB. Is this how to properly test at a higher range? Also, I keep posting the original graph to give you something to compare to. Would you like me to stop doing that, or is it beneficial to have the side-by-side?
Roly
Also, not sure if my BFD is ready to rumble, but it is hooked up and looking pretty.

[brucek]

Is this how to properly test at a higher range?

No that won't do anything, sorry. The point I'm trying to make is that you have a large peak at 50Hz. It would be better for determining filters if your entire response was about 5-10dB higher. Set the entire procedure up using 85-90dB, but put the target at 80dB (you'll have to manually click the target thumbwheel after the setup to get to 80db). This will give more filtering to that large area around 50Hz. Try it and see what happens.

Just post the single graph....

Can you also attach your saved graph.mdat file next post so I have something to work with to provide pictures rather than words - it's so hard to describe some of this stuff in words. Save the measurement under the pull down FILE / Save Measured Data Set

brucek

[Chrisbee]

roly

Can you double check you have all the microswitches on the back of your EP2500 amp pushed over to the left?

Only switches 3 & 8 should be pushed to the right if you are using the Behringer amp in stereo.

Moving 3 & 8 to the right turns the bass filters off so you get the deep bass through to your IB.

Double check you haven't moved any other switches if you do have to move 3 & 8 to the right.

[brucek]

CREATING AND ENTERING FILTERS

roly,

This is probably a good time to discuss using REW to create recommended filters and then entering them into the BFD and then re-measuring to check the results. I'm assuming that the filters will be entered into the BFD manually from its front panel. The BFD manual can be used to describe how to enter filters.

So at this point, you have taken a raw measurement with no BFD filters and saved it as a *.mdat file (using the pull down FILE / Save Measured Data Set). You are able to load that mdat file at any time in the future to work on your filters, but you may as well do some filters now when everything is hooked up and enter them into the BFD so you can test how they work.

Something you have to realize about REW is that it won't automatically create any suggestions for filters for dips that require gain. It simply suggests filters that will reduce the peaks down to the target line. This is smart since it has no idea if a filter with gain will work in a system, due to the fact that some dips in response are a result of a room resonance that won't budge no matter how much gain you throw at it.
In that case all you're accomplishing is to reduce your available headroom. So filters with gain are trial and error. If you have a dip, you can use REW manually to produce the best suggested filter with gain as if it would indeed respond. Then you enter that filter and do another response measurement and see the effect. Some dips simply respond exactly as REW predicts and some dips are very stubborn. Don't waste your time on them.

This part of the procedure requires some creativity on your part. REW will indeed automatically suggest some filters for you to enter (after pushing a few buttons) and shows on the graph the likely result after entering them. The predictions are remarkably accurate. If you just followed the advice of REW for filters you would remove all the worst peaks and your system would sound better. This just doesn't satisfy most people though. The fact is, after you have pushed the buttons to get the filters that REW recommends, you should use REW in the manual mode and play with the filters by adding your own and modifying the suggested ones until you get a smooth response predicted on the REW display. Then enter those filters into the BFD and see if the response is as REW predicts, and then tweak a bit to get it perfect.

Let me go through the procedure and show a few pictures.

Once you've taken the raw measurement and have saved that mdat file, it's time to let REW suggest filters.

I'll use my own system in the pictures. Here's my raw measurement and my target. My target is 80dB, but I have added a house curve to the target and have a crossover at 60Hz, so my display will look somewhat different than yours.



1. FIND PEAKS
Press this button and REW will find the peaks within the limits of the find peaks default entry of 20Hz to 200Hz. I usually set this first to 15Hz to 200Hz. Remember a BFD can only enter filters down to 20Hz, but I get better suggestions from REW with a lower limit of 15Hz.
REW will find the peaks and display them in a persistant chart in the left hand side of the graph. You can see by the little chart that the frequencies are at the peaks. I suggest every time this chart pops up to remove it with a couple Cntrl-Shift-P's.
Here's my own systems raw measurement and the associated FIND PEAKS chart. It shows, for example that there is a 10.2dB peak at 34.5Hz.



2. ASSIGN FILTERS
Now press this button and REW will assign appropriate filters to attempt to remove the peaks it found. The suggested filters are displayed in the bottom right hand corner of the REW page. The green entries are the actual BFD front panel entry for the frequencies.
Below are the suggested filters:




3. OPTIMISE PK GAIN AND Q

Press this button to automatically adjust the gain and Q settings of the suggested filters to obtain the best match to the shape of the peaks and so create the flattest corrected response. The corrected predicted response is now displayed along with the graph of the filters. The display graph gets very busy now.
You can remove all the extra stuff on the graph now to get a better picture of what the predicted corrected response will be. Turn off Sub Measured, Filters and Filters+Target to reveal only the target and the SUB CORRECTED response. At this point, if you simply entered those suggested filters, your response would look fairly close to the predicted response that REW now shows.

Below is the predicted response if I used the filters suggested. See the filter numbers along the top of the graph - kinda handy.



GET CREATIVE

Here's where you play with the filters manually by adding your own and also modifying the suggested ones to arrive at the best and flatest response (without getting too crazy). I ended up with quite a few extra filters as you can see by the diagram below. When you modify and add filters be sure to press the ADJUST PK GAINS after you do so......Play around with the parameters of each filter and see what it effect is on the response - REW dynamically shows you the results.



Below is the actual response (and very close to the predicted) that I achieved by the new and improved filters shown above. The predicted and actual were very close.



Once you like the look of the predicted graph it's time to enter the filters into your BFD and then do another REW response check to see if the actual response is as good as the predicted response. Where it will possibly differ is in the areas where a filter has gain.

Read the next line carefully because it's quite important!

When you do the new response sweep after the filters are entered into the BFD, you must temporarily clear the filters out of REW so they don't affect the new measurement. Just uncheck the boxes as shown below or the filters shown in REW will be applied to the new sweep measurement.
If you don't like the new response you obtained with the filters that you've entered into the BFD, you can reload your raw mdat file and then uncheck the filters and play some more. It can be several iterations (or not) before you're satisfied with the response. (You can see why the midi cable would be handy at this point). I don't have one myself, but I get why it's nice to have...




brucek

[rolyasm]

Very Exciting stuff,
So you are telling me that by leaving the REW SPL at 80, but actually having an output of 90 on my RS SPL, this won't achieve the 10 dB increase I am looking for. My thinking was that since REW is thinking it is seeing 80 dB, but is really being fed 90 dB, that my response would be 10 dB higher. I will try to reset the whole procedure and see what happens. So let me ask yet another stupid question. If I am EQing my subs for lets say a 90 or 100 dB signal, because obviously 80 isn't doing the trick, when I get all finished and I go to set up my system, what will happen. Say I just use my autosetup on my processor, it would set all the speakers to the same level, lets say 80dB, correct. So then my subs would be down into the sissy range again. Does this mean all my setups are going to mean I add a little more output to my subs to get them looking/sounding correct? So if I want good, deep bass I will always be turning the bass up from reference level? Just not sure how that all works.
Chrisbee,
All my filters are to the left, except for 3 and 8, and I think 2 and 9. 3 and 8 turn off the filters, I believe, and the other 2 turn the filters to a 30 Hz cutoff. I suppose it doesn't matter if those 2 switches are set to 30 or 50 since I have turned the filters off, correct? I can easily switch them back to the 50 Hz mode if it makes a difference, but I don't think it does. Thanks for the reply.
Brucek,
Another thing I didn't mention is that I might have some more work to do on my sub box(riser) before all is said and done. ThomasW at HTGuide, told me that when I finished the box and took some measurements he would help me to "tune" the subs by adding insulation, or batting, to the inside of the riser. Right now it is fairly hollow with only the top, bottom, and sides insulated. I think I remember hearing that by adding more "stuffing" it makes the box look bigger to the drivers. Not sure if that will make much of a difference in the way my subs respond, but I guess I should make sure that is taken care of and then do some more measurements. I am just waiting to hear back from Thomas. Thanks for the step by step on they BFD. When I get home from work tomorrow, I hope to do some more work on the subs. Thanks.
Roly

[brucek]

So you are telling me that by leaving the REW SPL at 80, but actually having an output of 90 on my RS SPL, this won't achieve the 10 dB increase I am looking for

That's correct, becuase the level in the room will be 90dB, but you've told REW that it's 80dB, so that's exactly where it will place it on the graph - 80dB......get it

If I am EQing my subs for lets say a 90 or 100 dB signal, because obviously 80 isn't doing the trick, when I get all finished and I go to set up my system, what will happen.

After you have added filters to get the best response possible, you can set your speaker level trims to whatever level suits you. Some people like their subs quite a bit louder than their mains and others prefer a flatter response. The level is up to you - but the BFD will be forcing the sub to provide a smooth overall response with no peaks, no matter what the level. (100db is a bit much, but 85dB to 90dB isn't for setting up REW).

What I was attempting to do for your first filter setting was to try and raise the entire wholesale level a bit of your sub and then knock down that 50Hz signal until it was closer to the level of the rest of the response. You could perhaps accomplish the same thing by leaving the 50Hz alone and raise all the rest using filters with gain, but I don't think that's a good idea.

By raising your overall level a bit to say 85dB to 90dB, while leaving the target at 80dB was to trick REW into supplying you with more reduction of the 50Hz (because more will be peaked above the target line). There's lots of ways of doing this. You could set the whole procedure up to 80dB as before and then just drop the target line to 75dB and then find filters - it will amount to the same result. Then of course you'll be tweaking manually anyway. Once you get playing with the filters you'll see what I'm getting at....

brucek

[rolyasm]

So my souncard has gain levels, as well as my Amp. Currently the gains are both set midway. Should I increase these as well as the volume on my reciever, or just use the receiver? Is there some rule of thumb for this?
Also, just tried to go back into my REW and run some tests and I am gettting this message: "Unable to access the replay device due to line with format PCM_signed 48000.0 Hz, 16 bit, stereo, 4 bytes/frame, little endian not supported."
I haven't changed any settings on my computer or REW since last time. Hopefully this is a common error with an easy fix. I will look at my computer and see if something has changed.
Roly
Edit: Nevermind. Not sure how I fixed it, but I did. I re-did my measurements just a few moments ago. Not sure what has changed. I reset my SPL and made sure everything was calibrated, and seemed to get a better response today. The second picture is with my amp's gain turned up 3/4 (all others have been at 1/2 gain). The third pic is 100% gain. So is this the easiest way to increase the output? I left the target at 80 on all. Let me know what you think. Thanks
Roly