Slaughter House Cinema Revisited

[carls64]

Well I am back again, I have some time to devote to making some measurements now that I have all of my acoustical treatments done. But I am not sure something is right. I am now using a Behringer Mic and pre-amp/mixer and I re-calibrated my sound card, etc. Here is my first measurements for each sub by themselves. I seem to be getting some sort of reverberation or at least that what the graphs look like, any ideas?

Left Sub

Right Sub

Both Subs

[brucek]

Let's see the scope of a measurement.

[carls64]

Do I have to re-measure to see that?

[brucek]

Yeah. One measure - one scope.....

[JohnM]

That kind of response occurs if monitoring is active or there is feedback caused by, for example, having Line In selected as one of the playback sources.

[carls64]

I will have a look at that and re-set up everything I have to do that anyhow to get my input levels set on my BFD.

[carls64]

Anything wrong with using a digital (TosLink) out on my computer to the AVR and using the analog input for the mic readings.

[brucek]

Anything wrong with using a digital (TosLink) out on my computer to the AVR and using the analog input for the mic readings.

How would you create the soundcard calibration file?

brucek

[carls64]

Ok I think I figured out the problems, something was not set right on my AVR and I was outputing too love a a level and it may have been clipping the subs as they were set really high. I have the subs level down REAL low and the sub out on the AVR high, and the input level calibrated on the BFD so i think I am good to go. Here are the new graphs:

Left Sub


Right Sub


Both

[carls64]

I adjusted the sub levels so they were more evenly matched at 75db+- .5db then took 3 more measurements, right, left, both then applied the corrections, and then a measurements on boths subs after applying the filters, what do you think?

Right Sub Before Correction/Filters


Left Sub Before Correction/Filters


Both Subs Before Correction/Filters


Corrections applied to both sub measurement


Measurement of both subs after filters were applied to the BFD

[carls64]

I discovered something interesting, although not surprising, my Yamaha RX-V663 AVR will treat the front, center and surround speakers as sub woofers if the speaker size is set to LARGE.

If you auto calibrate the system it will attempt to determine not only the levels and distance but also the size of the speaker (mid bass/woofers) based on the frequency response. So in short if it thinks the speaker is capable of outputting sub bass frequency it will include them when outputting frequencies below the crossover point.

So what I discovered was that when I set all the speakers to SMALL (Front, Center, Surround, Surround Back 7.1) and set the Sub woofer frequency to Sub Woofer only the crossover fed the low frequencies to the subs and the high freq to the rest of the speakers, like it should.

The way it was, all freq were being fed to the front,center,surround, surround rear, and the low freq were being sent to the subs. This with the AVR configuration for the Front, Center, Surround, Surround Back, speakers size set to Large, based on what the initial calibrations figured the speaker size was.

My Crossover is set to 80hz. I understand that there will be a certain amount of level being output to the rest of the speakers at the crossover point, but the way it was the main speakers were being fed the full freq range. I am sure that would effect the image/stage presence quality of the audio. I would have never known unless I had calibrated my BFD levels with the mains off, then with the subs off and the mains on to set the levels after setting the input level of the BFD.

The Yamaha RX-V663 manual is VERY confusing. One graph it says no LFE is sent the the mains if the setting is set to SUBWF. Here is the manual section.

[Wayne A. Pflughaupt]

carls64 wrote:

I adjusted the sub levels so they were more evenly matched at 75db+- .5db then took 3 more measurements, right, left, both then applied the corrections, and then a measurements on boths subs after applying the filters, what do you think?

Looks to me like the filters weren’t matched to the peaks very well...

Regards,
Wayne

[carls64]

Well I am manually setting the filters and based on the settings it only asked for me to set three of them and I double checked them. I am setting the filters in linked mode, I am wondering if I should set filters for each sub as I am sending a left and a right channel to the BFD and to the subs but I have the BFD in linked mode.

[carls64]

Maybe I missed a step in the process? How do I setup a house knee curve, or should I even attempt that at this point

[Wayne A. Pflughaupt]

carls64 wrote:

Well I am manually setting the filters and based on the settings it only asked for me to set three of them and I double checked them.

What do you mean, “the settings it only asked for?” I’ve never had REW ask for anything when I was setting filters manually.

When you manually tweak the filters, the dotted line shows what your predicted response will be once they are applied. Notice the dotted line in your 4th graph pretty much matches the second sweep you took in the 5th graph. So, with your baseline graph, adjust the bandwidth, gain and frequency center to flatten out the two peaks with minimal affect on the dip between them.

Maybe I missed a step in the process? How do I setup a house knee curve, or should I even attempt that at this point

The house curve file should be loaded in before you start equalizing.

Regards,
Wayne

[thewire]

I think I would check to see if the subwoofer has a crossover on while the receiver does also, or if maybe it needs to be set higher on the sub. The crossover area looks like it rolls off kind of quickly. Also, when you compare your results after eq you might let REW detect the target level or set it back to where you started. Depending on previous settings where the graph settings were prior, we sometimes need to go back and change the target to where we want it to be set at over again. For example if you were measuring your mains for a 75 target in one graph but an 80 target for the subwoofer, when you remeasure in your subwoofer after equalization in the second window again if you deleted your mains measurement, it's going to display a 75 target again.

[carls64]

thewire wrote:

I think I would check to see if the subwoofer has a crossover on while the receiver does also, or if maybe it needs to be set higher on the sub. The crossover area looks like it rolls off kind of quickly.

I saw that too however the subs are both set to max (160hz) and on the AVR it is set for 80hz, I am not sure there is anything I can do. See post about the speaker setup on my receiver, that may have something to do with that.

thewire wrote:

Also, when you compare your results after eq you might let REW detect the target level or set it back to where you started. Depending on previous settings where the graph settings were prior, we sometimes need to go back and change the target to where we want it to be set at over again. For example if you were measuring your mains for a 75 target in one graph but an 80 target for the subwoofer, when you remeasure in your subwoofer after equalization in the second window again if you deleted your mains measurement, it's going to display a 75 target again.

Ah, right the subs together are only going to increase the output. Should I measure and set the EQ filters for both together or am I missing what you are saying?

[thewire]

carls64 wrote:

Should I measure and set the EQ filters for both together or am I missing what you are saying?

Yes. I would equalize both subs at once.

[carls64]

I am wondering if the idea of elevating my subs was a good idea. bpape recommenced that I raise then off the floor a little to see what kind of effect it would have, and I just left them there ;-) My floor is concrete and it seems that I got a better responce out of my old 8" polk than I do out of the pair of eD A2-300's LOL

Currently I have them with the ports facing each other firing down. The screen wall is now dead(er) with 2" of 703 and the corners are filled with supper clunk 703 so I think I have a good amount sound treatment, along with the 8-2x4'x2" 703 panels I have on the side walls.

[carls64]

Ok after following the instructions on Wayne's post on setting the filters on the BFD I discoverd I was doing it all wrong. Here are some new readings:

Predicted corrections


First reading after filters applied


Tweaked a bit.


I think I am getting the hang of it, but boy, you mess with one spot ot screws with the others LOL

Thoughts?

[carls64]

After reviewing a number of other posts here in the REW forum, I can't seem to come to grips with my sub's dropping off like they are. I am tempted to connect their output to the speaker B outs and adjust the crossover on the subs to see if for some reason the AVR's crossover is causing it.

In a previous post I talked about how the Yamaha RX-V663 handles LFE based upon the size of the speaker in the setup, so I am wondering if this is what is causing the freq to fall off before it should.

I moved my subs to various different locations even inside the room toward the middle and there was not much effect, they still drop off at 92-94hz and I can't figure out why. I took them off the risers and, and settled on pointing them away from each other about mid way between the LC and CR channels, they seem a little more flat now in freq response.

I suppose I may want to remove the BFD from the mix, and or re-calibrate the setup now with the YPO on the AVR and then begin taking measurements from there. Something is defiantly going on.

[carls64]

Well I did everything I could and could not figre out why the subs are dropping off so drasticly at 94hz, but I did discover that the AUTO EQ was not flat as it should have been so I bypassed it. Here is a new graph with the sub, then the sub and the mains with 3 filters, and a singe boot at #3 (4)

Full range through 200hz with the mains engaged, I maybe can use the AVR's eq to bring down that spike at 95, so the mains are filling in that gape between 94-100 so I am not sure it probably is the AVR thats killing the subs.

[Wayne A. Pflughaupt]

carls64 wrote:

Full range through 200hz with the mains engaged, I maybe can use the AVR's eq to bring down that spike at 95, so the mains are filling in that gape between 94-100 so I am not sure it probably is the AVR thats killing the subs.

Yeah, the mains will take up the slack, so no reason to worry about the drop above 90 Hz. It might be a good thing, actually; I often find too much stuff bleeding over from the sub from poorly equalized program material, like from the low end of male voices.

Your second graph looks good – no reason to worry about the 90 Hz bump. It looks to me like your sub level is really low compared to the mains; you’ll see the 90 Hz think disappear once you take care of that.

Also, you sub response looks really flat. What happened to the house curve you were asking about?

Regards,
Wayne

[carls64]

Wayne A. Pflughaupt wrote:

Yeah, the mains will take up the slack, so no reason to worry about the drop above 90 Hz. It might be a good thing, actually; I often find too much stuff bleeding over from the sub from poorly equalized program material, like from the low end of male voices.

Your second graph looks good – no reason to worry about the 90 Hz bump. It looks to me like your sub level is really low compared to the mains; you’ll see the 90 Hz think disappear once you take care of that.

Also, you sub response looks really flat. What happened to the house curve you were asking about?

Regards,
Wayne

Well I didn't set up a hard knee curve yet, to be honest it seems a bit over my head on how to set it up. It talks about doing a bunch of measurements to figure out where your hosue cure is then you modify that with the hard knee curve. Any suggestions?

[carls64]

Almost looks like I have a hard knee curve going on here LOL
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