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Discussion Starter #1 (Edited)
Hello all. I'm new to this forum and somewhat new to home theater. I have had a good entry level setup for a couple of years now, but here in the past few weeks i've gotten the upgrade bug and i've also decided to start improving response by room calibration, etc. I'll post as I acquire new 'toys' which will be coming over the next couple of weeks (with the exception of full range new speakers). So for now, here is what I'm working with.

Environment: 21'x23.5'x8'-14' vaulted ceiling, which is also open to a 10'x20'x8' kitchen (12' wide opening)

Full Range: F/L: BIC Acoustech HT-88
..................C: BIC Acoustech HT-85
.................RR: BIC Acoustech HT-65

Subwoofer: Current: BIC H100 (poor little fella)
..............On-Order: Two Epik Sentinels

Test Equipment: SPL Meter: RadioShack 33-4050
.......................Laptop w/Internal Soundcard: MacBook MB466LL/A
.......................REW Software Downloaded from here. (THANKS!)


So on to my very first in room Response. I didnt get into moving things around too much since I'll be getting the new receiver today and the new subs probably next week. I mainly wanted a baseline. I would also like Opinions from those that have done this before on the kind of in room listening position response I'm getting.

So first, Here is the response that my sound card provides:

http://farm3.static.flickr.com/2615/4058422618_1b208755f3_o.jpg

I was SHOCKED at how well it performs... so much so, that I restarted the computer, cleared any calibration files and ran it again... got the same plot. Time to take measurements.

SUB Only. I moved the sub to a couple of locations, but the best response I got was in the same corner that I had it originally in, only rotated 90Deg to fire down the front wall instead of the side wall. I also used the soundcard calibration file and I loaded in the calibration file for the RS Meter that was also downloaded from here. Hopefully I was correct in using both of these Cal files. Here is the response:

http://farm3.static.flickr.com/2640/4057683031_b99febd0ae_o.jpg

I'm no expert, but this didnt really seem all that bad especially considering the caliber of subwoofer (~$250 range) and the large room it had to fill. I'm up about 10dB at around 55-65Hz and a few other smaller peaks and nulls. On another little side test, I played several bass heavy tracks to try and get a max SPL reading and on average I would get around 106dB max at around 12ft away from the sub. I didnt measure this distance, just a guess but I can measure it. I will also load up some pics of the room later.

After the sub measurement, I reconnected the towers. I took a few measurements, adjusting the Bass and Treble tones in between to try and level out the response as much as possible. Here is the end result:

No Smoothing (YIKES!):

http://farm3.static.flickr.com/2587/4058422554_ddc15a76f8_o.jpg

1/24 Smoothing:

http://farm3.static.flickr.com/2439/4058422478_5de2030bae_o.jpg

Again, I'm no expert, but this one was pretty disappointing to me. I've got what appears to be +/- 15dB from 50Hz up to like 15kHz, then it just drops off. This is where I think the new receiver might help tremendously with bult-in MultEQ, time delay/phase correction, etc.

EDIT: I'm not sure why the pics arn't showing up. I copied the links to them so you can at least click to see. I used the IMG tags, maybe they'll start showing up later. Or if a moderator could fix it and let me know what I did wrong?
 

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Welcome to the Forum Michael!

It's hard to evaluate your graphs because the scaling is wrong. Please review this thread and re-post them for us!

In the mean time - the Radio Shack SPL meter is only accurate up to about 3 kHz. If you're interested in seeing accurate response above that point, it'll require a calibrated mic and an outboard sound card with a mic pre amp and phantom power.

By the way the ragged-looking response you see in the full-range graph is the result of comb filtering, which is caused by the reflections in a room. Typically its best to use 1/3-octave smoothing for full range, and no smoothing for subwoofer graphs.

Regards,
Wayne

 

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Discussion Starter #4
Wayne- Thank you for the very informative and helpful post. I'll have to retake the measurements and adjust the scale later, all I had saved were the jpgs.

As far as the RS meter, I was under the impression that If I used the .cal file for the meter, it would adjust the plot to account for the inaccuracy of the meter.
 

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Discussion Starter #6 (Edited)
Ok I got my new receiver and subs in and have been able to give them almost a week of breaking in.

To recap, the main room is about 21'x23.5'x8'-14' vaulted ceiling, which is also open to a 10'x20'x8' kitchen (12' wide opening). HUGE volume to fill. The couch is pretty close to being in the center of the room... I thought this would cause big problems... we shall see in the results.

When I first received the subs, I spent about an hour and a half experimenting with some locations and have not moved them since. Now that they've broken in, I may experiment a little more later but I am quite happy with where they are.

For measurements, I used the Analog Radio Shack SPL Meter with REW and a calibrated Sound Card file and Calibration file for the RS Meter. No smoothing was added to the plots. I performed a quick test with the Duals as pictured here, level matched by eye-balling the gain dial on the amps:



To get an idea of the room size and layout:


Once I performed my quick test I turned the left one off and left the right one on. I adjusted the AVR volume until the subwoofer test tone was targeted to 75dB. Here is the response of the right Sentinel alone with Audyssey MultEQ on:


I was very surprised at how good of a response I was getting considering my room and listening position. Very good low end extension in room also.

Then, I turned the right sub off and turned the left one on. Rather than adjusting the AVR volume until the SPL Meter read 75dB, I adjusted the gain on the Sub. Afterwards, I ran REW and got the following response out of my left Sentinel also with Audyssey on:


So the next step was to measure with both on. For this measurement, I did not adjust the AVR volume down to 75dB so you will get a true representation of how much gain duals is giving me versus a single.


What?!? At 14.9Hz I'm getting the original 75dB target! And I've only got one or two very narrow nulls or dips. On average, the difference in the best performing single and the duals was about 6-7dB.

Just for fun, I decided to see how much work Audyssey was actually doing. So I made a measurement with Duals with Audyssey OFF. Here is the result:


I saw the post on how to scale the plots, but I extended the low end just a bit because at 15Hz limit at the left, you wouldnt see where the response rolls off.
 

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...
Once I performed my quick test I turned the left one off and left the right one on. I adjusted the AVR volume until the subwoofer test tone was targeted to 75dB. ...
Interesting questions arise when using Audyssey in the presence of two subs. I am curious what approach you took. Did you equalize the sub levels with the SPL meter, before running the Audyssey setup? You seem to say that you just set the gain dials identically, without using the meter. And I assume the two subs are receiving the same signal, with a Y splitter. Did you have both subs on when you ran the Audyssey setup?

...
Then, I turned the right sub off and turned the left one on. Rather than adjusting the AVR volume until the SPL Meter read 75dB, I adjusted the gain on the Sub. ...
Does this indicate that you adjusted the level of the left sub here, with REW as the signal generator and the SPL meter for measurement, after having run the Audyssey setup?

...
So the next step was to measure with both on. For this measurement, I did not adjust the AVR volume down to 75dB so you will get a true representation of how much gain duals is giving me versus a single.
...
So when you put them both together, you have adjusted the level on the left sub different from how it was set when you ran the Audyssey setup? Or did you put the left sub back to its earlier level?

If, as I believe, you have now effectively used REW to set the levels on the two subs to match, you should rerun the Audyssey setup to measure them together with their current settings. It may not make much difference, but whenever you touch the gain on one or the other sub, you have changed the balance, and you should see an even better equalization if Audyssey takes into account the actual balance between the two.

Bill
 
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