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Tempest AA SPL's Do I need a BFD???


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5 replies to this topic

#1 of 6 Bill**H

Bill**H

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Posted April 20 2004 - 02:45 PM

I posted this over in the DIY forum and did not get the answers I need. If I do need a BFD, where should I start with setting up the filters on it? I don't have a clue as what to do! I know it can hit harder than it does now from what I have read.

I just got my Tempest AA up and running Saturday night. I watched Matrix Revolutions as the first movie, (I've been saving it just for this). I can say it kills my 2 Sony SA-WM40's down low! I set it up 5 dB hot and my room is 2900 cubic feet. Volume was set to -10dB and I sit 13 feet away from the Sub and speakers. The Tempest spit out a little bit of Polyfil from the ports sometime during the movie.

I ran some test tones Sunday and here is what I got. The SPL's are with just the Sub running. Receiver @ -11 dB.

Hz------SPL------corrected (is this right??)
16------73.25------84.75
18------79.5-------87.5
20------82---------89.5
22------86---------92.5
25------88.5-------93.5
28------92.5-------96.5
31.5----93---------96
36------95.5-------98
40------94.3-------97
45------95---------97
50------99.5-------101
56------95.5-------97
63------90.5-------92
71------95.5-------97
80------88---------89.5
89------84.5-------86
100-----82---------84
111-----83.75------84.75
125-----65---------65.5
142.5---64---------64.5


I had my crossover set to 80 and only the Sub running. The room has some vibrations, I don't know how that plays with the meter readings I got. I did fix 2 of them but, didn't take time to find the others. I was afraid I would burn the voice coil up???

The Tempest doesn't seem to have the impact I think it should but, it shakes the floor and rattles the marble in the coffee table like the Sony's never did!

So, Do I need a BFD????

Bill

#2 of 6 Andrew*S

Andrew*S

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Posted April 21 2004 - 02:43 PM

Go for it. Definitely. After MUCH experimentation, I would recommend sub equalization to just about any sub. Think of it this way. If you calibrate your sub with pink noise, you are calibrating the SPL to the frequency with the highest peak. In your case, 50Hz is at 101dB while 63Hz is at 92dB. (You don't really need to measure much above 100Hz for sub equalization). 6dB creates a perceived doubling of loudness so your sub is currently calibrated to the 50Hz peak any any bass around 63Hz will sound close to 1/4 as loud.

So here's what I'd do.

1) get a BFD or if you have a little more expendable cash, get a Behringer Ultracurve Pro DEQ2496. The DEQ2496 runs about $339 from most internet music supply stores - music123, zzounds, musiciansfriend, etc. It is MUCH easier to configure, higher S/N ratio, built in SPL meter that is MUCH better than the RS meter, etc. You can buy a Behringer EC8000 microphone and a mic cable, hook it up to the DEQ2496 and measure your tones with it instead of the radio shack meter and it's way easier. Either way you go, make sure you get the proper cabling since both are "Pro" sound equipment. In essence, you'll have to get cables that are male XLR to male RCA to go from preamp to BFD and from Radio shack get some 1/4" mono phono plug to female RCA converters.

2) Download this spreadsheet. w*w.pvconsultants.com/audio/eq/peq.htm
what this lets you do is measure your tones, input them into the spreadsheet and you can play with the BFD/DEQ2496 parametric equalizer filters to see what they will actually do to your frequency curve. It will make setting the BFD/DEQ2496 easy

3) get a test tone generator for your PC. There's one here w*w.nch.com.au/tonegen/index.html. You can generate tones to match the ones in the spreadsheet in (2)

3) If you decide on the BFD route, go here to learn how to set it up w*w.snapbug.ws/bfd.htm. DEQ2496 is simpler.

4) Measure your tones, plug them into the spreadsheet and play with the equalizer on the spreadsheet to see what you have to do to flatten your curve or create a house curve

5) Once you set the BFD or DEQ, recalibrate your sub using the receiver's test tones.

You can also look at room modes and experiment with moving around your sub, but it's easiest to put it in a corner and equalize it...usually.

#3 of 6 Bill**H

Bill**H

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Posted April 22 2004 - 11:55 AM

Andrew

[quote]If you calibrate your sub with pink noise, you are calibrating the SPL to the frequency with the highest peak. In your case, 50Hz is at 101dB while 63Hz is at 92dB.

I never thought about it this way, thank you. I do not have Excel to run PEQ, but will try to get it to see what I will have to set the bands on the BFD to. I know this Sub should rock... Do you think maybe you could play with it and send me the screen shot using my Subs SPL numbers?

Bill

#4 of 6 Andrew*S

Andrew*S

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Posted April 23 2004 - 03:52 AM

Bill:
I could probably tell you how to set the BFD but to make it easier/better, you'll have to remeasure your tones. The PEQ spreadsheet has 12 divisions per octave - in other words, 12 frequencies from 20-40, 40-80 and 80-160. (The spreadsheet only goes to 100Hz). You gave me 7 divisions per octave. It's too hard to estimate correctly. The easiest way is to use that tone generator I linked to above, create a sine wave at these frequencies....

20.0
21.1
22.4
23.7
25.1
26.6
28.2
29.9
31.6
33.5
35.5
37.6
39.8
42.2
44.7
47.3
50.1
53.1
56.2
59.6
63.1
66.8
70.8
75.0
79.4
84.1
89.1
94.4
100.0

burn them to a CD and retest again. Then I can give you exact BFD settings to tame that curve. What I actually did for my setup is took the SPL readings and set up a few parametric equalizations to flatten my curve. I then ran it a second time with the parametric equalizations in place and saw that I hadn't gotten it perfect so I typed my new numbers in the PEQ and did it again. Took 3 tries but my curve is pretty good - I have somewhat of a "house curve from about 20-50Hz and flat after that....

#5 of 6 Bill**H

Bill**H

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Posted April 23 2004 - 03:58 PM

Andrew,

I just burnt a CD. I will play the test tones tomorrow morning and send them to you. Thank You for your help! I'm guessing I can store a flat response and a house curve in the BFD?

Bill

#6 of 6 Bill**H

Bill**H

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Posted April 25 2004 - 04:51 AM

Andrew,

I sent you an email with all of the SPL's you asked for with the address in your profile. Hope you got it.

Bill