Ron: if not to late in the design process, note that there are several methods to fit vents that are longer than the box is deep
-if using standard size ABS pipe for venting, use elbows (the easiest method with which to experiment with overall length)
- corner mounted rectangular or even triangular vents - take advantage of the side/back and bottom panels
- full width slot vents (high aspect ratios offer the advantages of resistive loading and bracing ) - take a look at some of DaveD's designs such as:
http://frugal-phile.com/boxlib/P10free/ClassicGR-MarKen10g2-map-260612.pdf
-if using standard size ABS pipe for venting, use elbows (the easiest method with which to experiment with overall length)
- corner mounted rectangular or even triangular vents - take advantage of the side/back and bottom panels
- full width slot vents (high aspect ratios offer the advantages of resistive loading and bracing ) - take a look at some of DaveD's designs such as:
http://frugal-phile.com/boxlib/P10free/ClassicGR-MarKen10g2-map-260612.pdf
I was going to use ABS pipe. I could use the original tweeter hole for putting in a pipe (very convenient).
The only question is, how do I figure the actual length of a pipe with an elbow? Is the path length through the tube (bending at a right angle) the port length?
The only question is, how do I figure the actual length of a pipe with an elbow? Is the path length through the tube (bending at a right angle) the port length?
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Finally got around to finishing this. The Alpair 10.2's are in the B&W DM100 cabs. Each cab has two 1" diameter ports, 6" long. Tuning according to WinISD is 41Hz. I tried 6.5" long ports, just in case, but they sounded too lean in the mid-bass. I think WinISD did a pretty accurate sim.
I haven't experimented with internal stuffing or any other "tweaks" yet.
These sound pretty darned good. Bass doesn't go uber-low, but is nice and full sounding, even in my 12' x 24' living room with only 6 watts per channel driving it. Mids are really stunning. Piano music sounds really, really fine. The single-driver cohesiveness is really nice. Highs might not be the smoothest I've ever heard, and these do beam pretty badly, but that was expected. The highs extend up high enough for my battered, middle-aged ears.
Thanks for the help, everybody. This was a good learning experience for me, and the least painful speaker-building experience I've had. Success!
-=|=-
PS - I first tried them with the cabs sealed. That was pretty good too, but of course, they would need (sub)woofers to be pleasing. Calculated F3 for the sealed cabs was about 75Hz. F3 for the vented cabs should be around 55Hz. That 20Hz difference is pretty huge, apparently.
PPS - Watched (and listened to) a PBS broadcast of Boulez and the Cleveland SO playing some Mahler, including vocal music (Des Knaben Wunderhorn). No crossover in the mids makes this type of thing really sound "live" and involving. I had a great time watching and listening. Really not bad!
I haven't experimented with internal stuffing or any other "tweaks" yet.
These sound pretty darned good. Bass doesn't go uber-low, but is nice and full sounding, even in my 12' x 24' living room with only 6 watts per channel driving it. Mids are really stunning. Piano music sounds really, really fine. The single-driver cohesiveness is really nice. Highs might not be the smoothest I've ever heard, and these do beam pretty badly, but that was expected. The highs extend up high enough for my battered, middle-aged ears.
Thanks for the help, everybody. This was a good learning experience for me, and the least painful speaker-building experience I've had. Success!
-=|=-
PS - I first tried them with the cabs sealed. That was pretty good too, but of course, they would need (sub)woofers to be pleasing. Calculated F3 for the sealed cabs was about 75Hz. F3 for the vented cabs should be around 55Hz. That 20Hz difference is pretty huge, apparently.
PPS - Watched (and listened to) a PBS broadcast of Boulez and the Cleveland SO playing some Mahler, including vocal music (Des Knaben Wunderhorn). No crossover in the mids makes this type of thing really sound "live" and involving. I had a great time watching and listening. Really not bad!
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