[Diogenio]

Group: I read the Martin J King OB white papers with great interest. Unfortunately, I have the curse of a relatively small area to place my speakers...positioning his H-baffle properly out from the wall with 15" or 18" woofer is out of the question. In addition, I love my low-power 2A3 SE amplifier, and as such - want to use a fairly efficient fullrange driver (93db +) to satisfy these power requirements. What to do, what to do...?

I currently run Fostex FE-126s in Frugal Horns, my subs are self-powered Yamaha servo units that mate very well - providing tight, boomless bass, even though they are tucked pretty close to the back wall. F-xover is approx. 90 Hz, and I let the horns roll off naturally...no external high pass filter is used. The Yamaha subs pose an interesting problem with my proposed OB, as they top out at 150 Hz with their internal xover.  With the baffle size I anticipate (15" wide max), I think I'll need to crossover at 200 Hz, or maybe even higher.

My system considerations bring up a number of questions for which I seek advice;

1) FR Driver Recommendations. I need to keep efficiency at 93+, higher is even better but I probably can't spring for Lowthers...too much expense. Are there any moderately-priced FR drivers to recommend for an OB?

2) Subwoofer selection. Hmmm, if the Yamaha won't output above 150 Hz,  I might have an issue matching to the OBs. There are LOTS of woofer drivers, cabinets, semi- and full kits out there, plus ready-made, powered subs. It's a jungle, so perhaps you can steer me to something that will deliver solid 30Hz, yet output up to 300 Hz if I need it to.

3) King's 15" Eminence Alpha H-frames WILL fit in the space of my current subs, and could be driven by a separate amplifier to offset their lower efficiency. However, I wouldn't be able to set them more than 10" from the back wall (the side walls are far away). Knowing how critical OBs are with respect to placement, I imagine that this would NOT be a workable arrangement. There would be plenty of backwave, with relatively little phase delay due to close proximity to the wall. That spells low bass cancellation, I would imagine. But...I welcome comments, especially from the man himself.

This is a great forum. I intend to relate my own personal experiences as soon as I get an OB system up and running.

Thanks in advance to anybody whom responds.

-Dennis
San Diego, CA 

 

[Luck768]

I do love also this forum I posting here for many months but in different user.,



_________________
Aprilaire
 

[rjbond3rd]

  Are there any moderately-priced FR drivers to recommend for an OB?

Are you familiar with the new Wild Burro OB-friendly drivers? http://www.wildburroaudio.com/

I'm using Visaton B200's but would have bought the Wild Burro Betsy's had I known about them at the time (bang for the buck).  The proprietor is very friendly and knowledgeable and the prices are unbelievably affordable.

In terms of efficiency, as you know, the essence of MJK's OB theory is that the woofer needs to be vastly more efficient than whatever FR you choose (to counter the effects of rolloff), so if you go high-efficiency on the fullrange, you're going to be fighting that efficiency and might end up needing two woofers to keep up (whereas if you choose a lower-efficiency fullrange, you can get by with one woofer but the tradeoff is that it's no longer a great match for your amp).

If I was in your situation (and basically, I am!) I would do the Betsy's on the site's recommended folded OB which will reach down to the 70's, a pretty decent match for your subs.  But I speak strictly as a newb enthusiast.  (MJK hangs out more at that "other" forum.)

[Taterworks]

It sounds like you're operating in limited space. Have you considered mating open-baffle mains with "low-Q" sealed or transmission-line LF speakers in a multi-amped setup? I don't think such a thing should be considered a 'sin' in the open-baffle loudspeaker realm for situations where open-baffle bass would be impractical.

(In this case, low-Q sealed and transmission-line LF systems are proposed because of a reported 'boxless' quality. Another possibility is the MAPD sealed alignment - a sealed enclosure with two chambers connected by an aperiodic vent, with the first chamber air volume equal to 1/3 Vas. Big woofers are not a requirement unless you want 'lots' of bass.)

Parts Express sells a decent 150W amplifier that can power your bass solution. It's the one that powers the ZillaAudio "Boomer" in a Betsy and Boomer system.

[rjbond3rd]

Taterworks, can you recommend a low-Q sealed driver / design?  Thanks in advance!

[Diogenio]

Thanks for your comments, gentlemen. RJBond...I just bought some B200s for this syetem. I'm wondering what you are using for an OB (dimensions, etc)? Are you feeding it through a highpass XOVER, or just letting the B200 roll off the low end "naturally?" If using a XOVER, what F -3dB is it? If no XOVER is being used, what do you estimate your F -3dB to be?

If I can employ a baffle large enough to give me solid 125 Hz from the B200, then I can simply use my Yamaha powered subs for starters.

-Dennis

[rjbond3rd]

Hi Dennis, I'm in the experimental / break-in phase.  I have a Rane A22B for crossing over (not connected yet) and I'm looking for a bass solution.  My baffles at the moment are 2 feet wide, 4 feet high, no wings yet.  But this is temporary.  I'm not sure of the F3 but I'm just getting started.

I'm going to get piano hinges and probably follow the Gravity Well of a Dark Star dims (a variation of which is here: http://www.wildburroaudio.com/projects.php  These get down into the 70's with the Wild Burro Betsy driver (which is in the same ballpark as the B200's).

For bass, I have been looking at Martin J. King's Goldwood H-Frame: http://www.quarter-wave.com/Project08/Project08.html

But since my room is small, I'm curious about the possibilities of two sealed subs.  The flat-out best, most incredible bass I have heard to date came from serenechaos' tapped horns (beautiful, smooth, no boom, deep!) but since I'm a terrible, lazy and impatient builder, I will probably go for two sealed subs.

Sorry I can't be of more help but I'll post my results (when I get some worthy of posting!)