My DIY 210 Questions

[DaleyKD]

Hey guys,

[Extra info: GK 700RB-II and a MIM Fender P-Bass with Seymour Duncan Quarter Pounder Pups]

I built a 210 cab for the BP102-4 with a Selenium DT150 tweeter (I keep the L-Pad off). I personally love the sound, and think it turned out great. The ID is approx. 23"W x 14"H x 13"D. I believe it's tuned to approx. 54 Hz.

If you don't mind, I do have a few questions.
1) Is 54 Hz ok?
2) Should I have put foam on the front baffle?
3) The 4" dia. PVC is 8" long (plus 1/2" flare of the rear wall). The PVC gets AWFULLY close to the woofer. I thought I read somewhere that it should be half the diameter of the PVC away from the speaker. Is that distance from the cone, or from the magnet?
3a) If it IS too close and I shorten the PVC, won't the tuning go up? If so, do I add an elbow and extend the PVC?
4) Finally, I notice an 'odd' sound that occurs when I 'pop' the 2nd fret D string or 2nd fret A string (it might happen on other notes, but those are the ones I noticed). I only hear the sound if the speaker is aimed at my head (not my knees). I don't know if this is farting or just expected due to 'poor playing style.' Is there a way I can get you more information for a better diagnosis?

Thanks in advance. This was a fun project and I'm 95% pleased with it.

Kyle

 

[bgavin]

I assume you have the two 4-ohm wired in series for an 8-ohm load?
If not, you are subjecting your amp to a 2 ohm load... think carefully here.

Each BP102-4 displaces 0.041 cuft of space.
Combined with your stated measurements, this gives a net volume of 2.34 cubic feet.
Subtract further from this, for the volume occupied by the vent.

For the traditional vented alignments, each BP102-4 requires 2.37 to 3.01 cubic feet, each.
Your box is tight for a pair of these.
The result is a strong hump centered near 85 Hz, and quite usable down to 50 Hz or so.
This will make it sound very strong in the mid bass, and pleasing to your ear.

[ edit ]

Yes, an elbow is quite acceptable.
You want the end of the PVC to be a full diameter (4") away from any obstruction.
The odd sound appears to be something other than a speaker problem.