Originally posted by Paden
Phil thanks for the review & the links you provided.
I'm a little unclear on a couple of matters though
When setting the input level to your BFD do I understand correctly that you play a film with the loudest bass you have as loud as you're ever likely to play it? (me thinks the Haunting )
In your review you say
"Once you set this you can only adjust the sub's output with the volume control on the sub"
After you've adjusted the input level to your BFD to just below clipping, you have to
"adjust the output level (volume control) on your sub to equal your mains" (Sonnie Parker's guide).
Do you do this at 75dB?
If so how do you get your main speakers to this level if you can't adjust the amp volume during the calibration?
Cheers, Paul
I'll try and answer everyone's questions but I'll start with yours Paul. When you set the input level of the BFD in the bypass mode you can see LEDs on the main display, there are about 10 green, 1 orange and 1 red. I used U571 chapter 15 during the depth charges to set this level, the object is to get the peak of the bass to reach the Orange LED but if the RED LED only blinks that's fine too because that's the clipping point, you do not want the Red LED to remain lit though. You use the amp/processor's LFE level adjuster to set this level and not the sub's volume control. After setting that level you then engage the BFD (turn bypass mode off) and you now have to set integrate your sub with the mains as you would normally but now you can only use the sub's volume control.
Originally posted by GaryG
Nice review Phil, how you have the patience to photograph each step is beyond me.
An optimisation I use now after doing so many sweeps is to just sit in the listening position and watch the spl meter as I sweep the frequency. I do one overall sweep to see where the problems lie and then another sweep dealing with each peak in turn as I encounter it, it's much quicker than using the spreadsheet. Obviously if you got the sub in the best location there's no need to keep doing it, but I took the view that I wouldn't know if I had the best location for the sub unless I moved it around the room and measured it's response.
A couple of suggestions if I may be so bold.
1. Use four blobs of Blu-Tac to seperate your BFD from the surface on which it sits (much better de-coupling than a mat).
2. Avoid placing it on the sub if possible. The BFD has capacitors in it which are 'microphonic', their capacitance varies due to the mechanical vibration from the sub which in turn affects the sound. This is only a small point but if you can mount it elsewhere you might as well.
I'll certainly try and reposition the BFD now after that tip, thanks for that.
Regarding the graph, if you have a copy of AVIA you can also try the sub sweep from 100-20Hz as it's counted down onscreen, just measure the output and curb any peaks, I could of easily done that and got the same results because when I turned the BFD off I got the same peaks as the graph showed and I knew exactly what frequencies were causing them
Does the blu-tac suggestion mean you too don't like my beautiful bathroom mat idea
Originally posted by NicholasB
Apoc, I have to assume that you're using some sort of microphone to generate those graphs, but you don't mention it in your hardware list....
I used the Radio Shack Digital SPL, if you download that Excell program you will see some tables to the left of the graph, as you fill in the figures that the SPL shows the innacuracy of the SPL is taken into account and the figures to the right are the recalculated figures which go on the graph.
Originally posted by James45
Great review Phil... even I understood that! Certainly sounds like a fantastic investment for £100, although it looks as though your BFD is plumbed into the water supply! You're not doing a Comer water-cooling jobbie are you?!
As a former owner of a watercooled PC I know exactly what you mean, god only knows why the 6.3mm adaptors came in an L shape
............love these new smilies
Originally posted by Steve Bate
Excellent post Phil, you've obviously got far too much time on your hands
I did yesterday, it was a training day at work and we were allowed to go home at 12:30pm, here's to more training days I say
Phew, Spanish Inquisition over with
Phil