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Old 26th June 2008, 07:35 PM   #21
Kensai is offline Kensai  United States
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No whizzerectomy. They will require either EQ for the top end (yes this really does work, and it sounds pretty darned good; has very poor off axis response, though, unless you have phase plugs), or tweaters capped in with 2uF or smaller. I'm using mine in my livingroom now, in large sealed bookshelves (so about 21.3 L + a pretty serious amount of soft, open cell foam) crossed to the stock Yamaha tweeters originally in that box with the stock 2.2uF caps. They really came into their own here. They really want a box, and they sound really clean in sealed. In my application where the driver center isn't more than 9-10 inches from the floor and the effective baffle width is about 7' since they're in the outer, lower compartments of a huge oak entertainment center which also has about a 2" airspace below the bottom panel (which is cut from a single sheet of oak plywood) which is open in the back, I'm getting pretty solid to 35Hz and useable down below 30Hz with nothing more than my crappy old Pioneer receiver's "loudness" control set to ON. These need better tweeters, but I've been lazy/busy lately . . . gonna need to cut or find something I can screw down to one of the openings and then mount my Dayton 5/8" domes into, and that just sounds like alot of work right now ;-p

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Old 26th June 2008, 09:49 PM   #22
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Quote:
Originally posted by Cambe
Hello,
What are the alternatives if the 3.5 inch port diameter(inside) isn't available?

Just use a rectangular vent with the same CSA. Make sure the HxW dimensions of the vent don't exceed a ratio of 1:9
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Old 26th June 2008, 10:34 PM   #23
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I've owned/used B20's and wasn't very happy with them. Pretty much all the stuff you guys have said is what I found wrong about them .

Dustcap resonance= nasal/congested mids

Treble that was desperetaly in need of a tweeter

Bass that was fairly decent, but rather soft in it's presentation , no "whack" or "snap"

I had them installed in a 7' line that was not tapered, and was approximately the same cross sectional area as the cone.

I tried them Bipolar in the same cabinet, but the port/terminus was too noisy ( not enough area ? )

Based on my experience with this driver, I would suggest:


1. Remove the dustcap, it sounds like HELL.

2. Solder the Aluminum voice coil former's gap, so it acts as a shorted turn. This will reduce inductance and help the treble response.

3. Install either a copper or aluminum phase plug. This will also help reduce the driver's inductance and help treble response. Be creative, there are plenty of things you can find to use for a phase plug.

4. Line the inside (facing the cone) of the frame's legs/spokes with felt or somesuch , this will help reduce the first reflection and help clean up the mid/treble.

5. Damp the outside of the frame with ropecaulk/ductseal/etc. This will help reduce the baskets ringing.

6. Perhaps some type of cone treatment if these other mods haven't fixed it's ugly sound.


I have little-to-no love for the B20. When you consider what must be done to it for it to work decently, it really loses it's appeal and value.

Why not just start with a better driver , do the same mods, add a whizzer, and have a better speaker for about the same cash ?

Silver Flute 6 1/2" shielded sure looks sweet , the 8" non shielded looks good , too.

Tang Band 6 1/2" looks pretty sweet. Add a whizzer and your set. It's even about 91-92db.

There are plenty of drivers I would choose over the B20.


Sorry if I've offended any B20 fans. My experience with them wasn't very good. I will say they are QUITE durable.


Just my $2.00 worth.


...........................................Blake
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Old 26th June 2008, 10:52 PM   #24
mightym is offline mightym  United States
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My intention was to use the PE push-in tweeter that every one seems to like with this driver.

I was going to purchase several caps to experiment with where they roll in.

No offense to Dave at P10, but I was going to turn my own phase plugs. The basic ideas is DIY, after all isn't it?

You cannot count the cost of your time, when it is spent in a labor of love.

John
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Old 27th June 2008, 12:33 AM   #25
mikje is offline mikje  United States
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Scottmoose,
Did you use any damping in these? If so, what and how much. I'm seriously thinking about a pair of these for a Velleman chip amp, at least until my next chip amp. Thanks for sharing your experience and know-how!
Mike
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Old 27th June 2008, 09:55 AM   #26
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Blast. Knew I'd forget to post something. Yes, 0.45lbs ft^3 of hollow fibre material in the first 1/3 of the line, or (better) line the back, top & one sidewall with ~1in thick damping material. Adjust to taste / suit your room & system from there.
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Old 6th July 2008, 01:00 PM   #27
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Cambe,

If the port is still an issue, you can find 3.5" dia. pvc conduit across your electrical supply counter.
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