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Old 3rd February 2013, 09:30 PM   #41
wicked1 is offline wicked1  United States
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Here's what I've got so far.
It started as a pair of "acoustic response" 'white van' speakers. Someone gave them to me, I think in was back in the 90's.
I replaced the tweeter w/ the fostex ff85k, left the mid in place, but disconnected. Replaced the 30ohm pots w/ an l pad. Replaced the woofer w/ an MCM 12" die cast. (it is definitely not the advertised 96db/w, but it was cheap).
Xover is 500hz 18db for the 85k, and 12db for the woofer (it's what I had on hand).
The cabinet walls have acoustic damping foam glued to them, and poly stuffing.
Today I increased the port length, which was recommended by speaker calculators. The port's about an inch longer, but I really think I can hear a noticeable difference in the bass! It's good. I also stuffed a thin black aquarium foam pad in the port, to cover the white extensions, which must do something to the sound. The ff85k is turned down maybe 2db, if my guess of a linear range of 6db is accurate.
They sound great right now. Maybe because I've gotten used to them .
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Old 3rd February 2013, 09:33 PM   #42
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Is the FF85 in its own enclosure?

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Old 3rd February 2013, 09:46 PM   #43
wicked1 is offline wicked1  United States
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No.... The stuffing is dense in an area around the back of the driver, but no..... it's just screwed onto the box.
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Old 3rd February 2013, 10:43 PM   #44
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A chink of 4" PVC -- at least 7", but i'd run it all the way to the back and then open out the back to make it a TL.

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Old 4th February 2013, 12:57 AM   #45
wicked1 is offline wicked1  United States
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Could I run a curved tube out to the front mid driver hole? would that be a problem for phase?
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Old 4th February 2013, 01:12 AM   #46
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Sure that would work. The idea is to damp out all, or almost all of the back wave.

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Old 4th February 2013, 07:17 AM   #47
hajj is offline hajj  Lebanon
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Is that contraption on the floor next to the speakers the latest generation high-tech retro mouse trap?

Quote:
Originally Posted by wicked1 View Post
Here's what I've got so far.
It started as a pair of "acoustic response" 'white van' speakers. Someone gave them to me, I think in was back in the 90's.
I replaced the tweeter w/ the fostex ff85k, left the mid in place, but disconnected. Replaced the 30ohm pots w/ an l pad. Replaced the woofer w/ an MCM 12" die cast. (it is definitely not the advertised 96db/w, but it was cheap).
Xover is 500hz 18db for the 85k, and 12db for the woofer (it's what I had on hand).
The cabinet walls have acoustic damping foam glued to them, and poly stuffing.
Today I increased the port length, which was recommended by speaker calculators. The port's about an inch longer, but I really think I can hear a noticeable difference in the bass! It's good. I also stuffed a thin black aquarium foam pad in the port, to cover the white extensions, which must do something to the sound. The ff85k is turned down maybe 2db, if my guess of a linear range of 6db is accurate.
They sound great right now. Maybe because I've gotten used to them .
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Old 4th February 2013, 10:46 AM   #48
xrk971 is online now xrk971  United States
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Yes, it looks like it even has built in HV electrocution feature to finish the mouse off quickly and humanely. I used to have one of these white van specials, also from 90's. Mod'ing existing cabs is definitely a fast and easy diy.
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Old 4th February 2013, 01:27 PM   #49
wicked1 is offline wicked1  United States
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Quote:
Originally Posted by hajj View Post
Is that contraption on the floor next to the speakers the latest generation high-tech retro mouse trap?
Close, it's a bird toy! my birds love my amps for some reason.. I think because birds are crazy thrill seekers, and they know their lives are in danger if they are near the amps.

It's a parallel push pull 829b amp. Those shiny heatsinks on the tubes have about 620v on them. Haven't figured out how I am going to design the chassis yet.. I'd like the tubes on display, but don't want anyone/anything to touch them! (my wife thinks I should just stick HV stickers on the chassis, and be over it.. hah.. (no we dont't have kids yet)) Maybe glass chimneys around each one.... The red PCB is Pete Millett's universal driver board. I regulated the screens and the bias supply for the 829's. I don't have proper test equipment, but I should be getting at least 80 watts out of it. That's a mono channel in the pic. (big amps!)

I'll do some more experimenting w/ the speakers later this week. It's been a fun project. I swear though, extending the port an inch really seems to have changed the bass... more than I would have ever expected. Maybe it was interfering w/ itself w/ the higher frequency port.. sounds good now, though.
Speakers are an even deeper rabbit hole than the amps! yikes...
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Old 4th February 2013, 06:59 PM   #50
wicked1 is offline wicked1  United States
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Ok, 'later this week' turned out to be 'later this afternoon', so I've modified them w/ what I had... some 4" flexible tubing, like for drier vents, or this was specifically for venting the bathroom out the roof.

anyway... Sound difference is subtle, but I think some mid frequencies that were a bit soft(low volume), are good now. And, it sounds more open and 'full range'. (by the way, I know this turned in to a multi-way-ish project, so thanks for discussing it here)

-Just in case it isn't clear, that tube is sealed around the back of the ff85k hole and curves around to the hole where the mid driver used to be located.
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Last edited by wicked1; 4th February 2013 at 07:15 PM.
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