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View Full Version : My VTF-3 MK3 Freq Response Graph, check this out!


Matt_Smi
August 21st, 2009, 7:38 PM
A while back I found this cool spreadsheet that someone put together where you basically punch in your SPL levels at each frequency and then it graphs it for you and compensates for the SPL meters in-accuracies. I did this with my VTF-3 MK3 and the results really surprised me, esp. since my system is more or less un-calibrated and I did this test using 160 kbps MP3 test tones! I plan to redo it with my Avia DVD however.

Basically all I did was set the volume on my Onkyo 805 AVR at -22 and the gain on the sub to half way or 12 O clock, played each tone twice and recorded what SPL I got. The sub was set to Max Output mode and yes I realize I am running it fairly hot (I usually have it on 11 O clock for movies) but regardless the sub never sounded stressed or made any port noise and even though this method isn’t the “proper” way of doing it or scientific at all doesn’t it still show that the sub is extremely flat, pretty much 100 Dbs across the board from 25-100 Hz with a few small +/- 1-3 Db peaks and dips. I think that is pretty damn good, I also want to try this in Max Extension mode. I have Ascend CBM-170 fronts and they as well as the sub are crossed at 80 Hz.

kmitchell
August 23rd, 2009, 6:18 AM
Matt,

That's good stuff. You should also look into REW http://www.hometheatershack.com/roomeq/ (http://www.hometheatershack.com/roomeq/%29) . It's got a bit of a learning curve but it sure beats taking SPL measurements by hand. Once you start playing around with REW you'll find yourself tweaking and sweeping for an entire weekend.

Have fun,
Ken

Matt_Smi
August 24th, 2009, 12:41 PM
Matt,

That's good stuff. You should also look into REW http://www.hometheatershack.com/roomeq/ (http://www.hometheatershack.com/roomeq/%29) . It's got a bit of a learning curve but it sure beats taking SPL measurements by hand. Once you start playing around with REW you'll find yourself tweaking and sweeping for an entire weekend.

Have fun,
Ken

The link will not work for me :( But I am going to give this another go using Avia and plotting the graph for 90 Db (someone told me that is what you normally do) rather than 100. I am sure that using Avia alone will give me much better results than using MP3 test tones.

kmitchell
August 25th, 2009, 4:50 AM
Hi Matt,

Yeah, you have to register with hometheatershack before you can access the REW pages but it doesn't cost anything to register and they don't spam you after you register. I think HSU suggests 75dB for room measurements which is what I set when I use REW. I do run the down-sweeps at the end of the HSU test CD at 90dB which is good for getting the rattles out of a room.

Hope this helps,
Ken

Edit: The HSU subwoofer spreadsheet suggests 70dB SPL but I seem to recall that number being bumped up a bit in some forum discussions.