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Kensai 8th May 2006 04:30 PM

Passive Radiators?
I am curious as to the point of passive radiators. I know they replace ports in some fashion, but I was wondering if I could get more of a description of the character of a system using them

I really dislike the sound I've gotten from any ported speaker, and I've never gotten the chance to hear any or the more interesting variants (i.e. transmission lines, backloaded horns, BiB, etc.).

I'm running Kenwood KFC-6469s (6"x9" bicones) in OB right now. They sound really good given the minimal cost so far. The most glaring issue I'm seeing with them so far is that I'm only getting solid bass down to about 60Hz (useable a bit under but not very far). I'm working on modding them, and will be adding rope caulk to the baskets and doing some slight attenuation of the backwave once I've finished with making phase plugs and treating the whizzer (that's the only paper part), but I'm doubting that such mods will really bring that down beyond 55Hz (correct me if I'm wrong).

I've been reading up on the various enclosures I could work with to reinforce the bass from these drivers, and the use of a PR enclosure (probably pairing the Kenwoods with a Dayton PR, 8"-12") is the last one I'm looking for opinions on (sound better or worse than ported, BiB, etc.).

I don't have any TS parameters for this driver, so I'm guessing I would be hard pressed to model an appropriate box of any sort for these. In my office rig, they're in 16"x20" baffles that are hinge mounted to my desk, so I'm getting some resonance from the desk itself. I have another pair that I'm thinking to hinge mount to the sides of a huge entertainment center in the living room (complete with driver mods). I don't know what sort of low end I'd get out of an OB that's effectively 28"x72", about 4" from the back wall on one side, and corner loaded, less than 2' from the side wall, but I'm wondering if there might be a better option from among the various PRs, lines and horns.

I am partial to the sound of OBs, so far, but I'd like a bit more bass and am interested in your opinions?


Cal Weldon 8th May 2006 05:05 PM

IMHO PR systems sound something between a ported and a sealed. I'm not a fan of ported either but I do use PR's a fair bit. If you are thinking of matching to the 6X9, I would suggest a 10" drone.

Kensai 8th May 2006 06:06 PM

Yeah, I was thinking 10" minimum. No real reason to limit it to an 8" that I can see, though the price difference between 12" PR and 15" PR is significant, so if I really need more, I'll just double up on smaller ones.

I like the sound of the low end from sealed enclosures (current living room set up is large bookshelves with 8" woofers; gets solid to 45Hz, useable down to 35 or so). Main issue with them is the way I'm forced to set them up (very close to the floor). If I'm gone to DIY anything else/better for use in there, they'll need to be fairly small and light floorstanders that can be moved in and out at my wife's whim (its HER living room, after all).

Any thoughts on, say, a simple box, maybe 4' tall (minimize wood working ;-p) 8" wide (just wide enough to mount the Kenwoods on the front) and maybe 1' deep with 1 or 2 PRs side mounted? With the edges rounded off and a nice black paint job, they'd be nice looking, cheap cabs, but would they sound any good?

Another option I've been considering would be to put 2 Kenwoods (I've got a few pairs of them) into a sealed, push-push bipole configuration with their magnets touching. Would make the cab's foot print about 8" wide and 8-10" deep. I'm guessing that would sound pretty good, from mids on up, similar to what I'm getting with my OBs, but even with 2 drivers, I'm wondering how much bass such a config would offer since the cabinet volume would be somewhat low.


Cal Weldon 8th May 2006 09:37 PM


I've not heard the Kenwoods but I'm guessing one of them with two 8" drones would work well. I've found that it sounds better if you don't work the passives too hard, so make their combined potential displacement around two to three times that of the active driver.

As far as the push push config goes, you'll have to ask others about that.

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