Refurbing old cabinets, FR style

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I've got some big old 3-way bookshelf cabinets that currently have nothing in them. They're sealed, about .9 ft cu, and have openings for 8" drivers, 4" drivers and tweets. I'd love to go full range single driver for these, if I could, so I'd like to solicit opinions and commentary from you guys.

First thought, of course, is to find a good 8"er to drop in, seal up the rest and let her rip. The Pioneer B20 sims fine in that enclosure, but it would still require help up top. It looks like all the Fostex 8"ers' specs show a bit of missing top end, too. I'd probably be okay if I could get flat to close to 16khz as long as the bass was solid (I get alot of room gain the way things will have to be set up, so flat to 60hz would probably be more than adequate as long as the rolloff is fairly gradual), and I get a driver with "midrange magic" as I've heard it called. I suppose another option would be to build a second baffle layer and mount one of the 6.5" Fostex in the 8" opening.

The other option would be to go with a 3"-4" (e.g. HiVi B3S, any of the Fostex drivers up to maybe even the 4.5"ers if I do a little creative woodwork; I don't think I can shoehorn in a 6.5"er in this config) driver with an 8" Dayton passive radiator. That way, I know for sure the high end can be taken care of authoritatively. I just don't know what I can expect on the low end, if it will go deep enough for me or if it will sound any good (I refuse to go bass reflex; I'm allergic to the sound, so I'm not sure if using a radiator will sound any less offensive).

So, any thoughts as to the success of any of these methods? Driver selection? Would I be best off going with a small FR and then dropping in an 8" woofer like a Dayton DVC (cheap and sims pretty nicely in this cab size, especially once you've crossed it low which adds some DRC to it). Or maybe just forgetting about it and building new?

Thanks,
Kensai
 
If it's a nice cabinet, sounds like a good idea to me.

I can personally recommend the Fostex FE207E. I use them in 45 liter vented cabinets,
http://i68.photobucket.com/albums/i6/heatherandsteve/Projects/0567e9db.jpg
with DIY phase plugs, which may have smoothed out the highs a bit.

Another fellow from the Bottlehead scene uses them in smaller cabs,
http://db.audioasylum.com/cgi/m.mpl?forum=bottlehead&n=99712
and has gotten some very positive comments. I think his cabinets are just about the size of yours.

I don't find these drivers lacking for treble. They do have the characteristic full-range on-axis rise, so I toe them in about 45 to 55 degrees, and that works really well.

I would recommend a rear-firing port. When you get to details, all kind of people can recommend what size.
 
That other gent's cabs look very much the same size as mine (a little broader baffle but a little less depth).

I'm glad to hear that they may be serviceable without a tweet, so they may certainly be viable for my needs. As for the FR rise, not a problem as the things will be seated on their sides, in the outer lower compartments of a very large entertainment center, so very near the floor and made to face flush out, so 20-30 degrees off axis vertically and horizontally.

I hear alot of gripe about whizzers on these things, too. I have used two different types of whizzered drivers myself. One I had to EQ the top end back in and the other I had to EQ out several peaks (approx 2, 7 and 9 kHz) but the high end easily extended out past where I can hear, so I can't really say experientially that they're bad, but I have been very interested in possibly finding a whizzerless FR that might work (if I can't find one for this project, I'll try it again with something else later)

Only red flag I'm getting with the FE207E is that they may not like a sealed enclosure. I really, really don't want to port this thing.

Thanks,
Kensai
 
Hi Kensai!

I like to take old boxes that are well made and recycle them too. Usually, I sand them down and stain them darker than they were… three coats of poly and it’s like brand new boxes. I always change the front baffle.

As for your driver choices, Fostex has more ‘midrange magic’ than the Pioneer B20. The B20 has a midrange you will like or dislike. It’s certainly not neutral. Personally, I really like the B20 (but only with a tweeter on top) but it can sound cupped or papery. Otherwise it presents a big image and an effortless sound that I like. Works well with the little SI amp too. I was dialing in the rear firing tweeter on mine just last night since moving them from one room to another. The B20 (with a tweeter) makes smaller drivers like TB’s sound ‘small’… I like my B20’s in sealed cabs… others may feel they can go deeper, but I choose to limit their low frequencies in an effort to keep the midrange as clean as possible. Use a powered sub if necessary… depending on room size you may not feel you need one.

Or you can go with a Fostex driver but you will need to port the box either out the front or back. I would recommend the 207e or the 167e… with a port. Because these drivers are somewhat tilted up you may not feel the need for a super tweeter at all.

If you choose a Fostex I will gladly help you determine the correct port size.

Godzilla
 
Thanks, Zilla.

I've been considering the B20s due to your commentary and that of a few others (heck even Nelson Pass called them "listenable at the lowest price" ;-p) and their low cost (I hate spending real money on experimentation). You like to cross an 8ohm tweet with a 1uF cap to go with the B20s, right? Guess that means if I were to drop in a pair of Neo3PDRs I have (4ohm) I should use .47uF caps, eh? Any thoughts as to whether phase plugging them might help clear up the midrange withough destroying the imaging? I'm a huge fan of imaging myself, moreso than say absolute detail. I also prefer the "larger" as you say sound of bigger cones (and I really have my doubts as to the quality of the sound coming from a passive radiator, especially being driven by the backwave of a low Xmax 4" driver).

Looks like I'm leaning back toward the B20 now since the Fostex 207 1) needs to be ported and 2) costs 3x as much. I shouldn't need a sub, either. The B20s sim to similar levels as the original 8" drivers for these cabs speced at, and they, in room the way I will have to set them up, are solid to the low 40s and still present at 30Hz, so I imagine the B20 would give me similar real life response. I guess maybe I'll go for the 207s or 167s if I can ever get authorization to put a pair of BiBs in the living room ;-p

Kensai
 
After hearing Fostex drivers there is no way I can say the B20 is better. Fostex offers much more easy detail, superior speed and tone of instruments/voice. The B20 is like an out of shape athlete. He gets the job done but without the finess (sp?) of an All Star. But the B20 is cheap and will provide crossoverless mids (tho without all the magic of the Fostex or other more expensive full range drivers)… I strongly suggest the tweeter because the B20 doesn’t sound very good to me at all without one. You will have to try different cap values on your tweeter. If it’s not a piezo you don’t need to include a resistor at all…. Simply a cap. Try different values to hear which blends the two drivers best to your taste.

I would leave the wizzer as is and not worry about treating this cone since it’s cheap and improvements will be minor IMO. If you get the bug and want to go Fostex (or Lowther, Supravox, Hemp, etc…) make sure you have the space for larger cabinets and plan things out for a better sound system in the future.

Enjoy!
 
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