Pioneer 8" build, the Chang variant - Page 11 - diyAudio
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Old 5th September 2007, 01:37 AM   #101
OzMikeH is offline OzMikeH  Australia
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I havent done it but I'm fairly confident of success:
Blu-tac a small tube to the front of the pole piece. a 25mm PVC pipe coupler for example. place the driver face down, drill from the back, dead centre so you don;t get any magnetic funnies.
approx 1/8 inch is big enough for 2 strands of cat5 (suggest stranded as it's less likely to break than solid) slightly countersink each side by hand with approx 1/4 drill.

turn driver over, fish the filings out with a flat steel screwdriver, the filings will tend to stick to the screwdriver in preference to the pole piece. once all filings are cleared from the tube remove it. Dripping candle wax into it would be a good way to secure any tiny bits of metal prior to removing the tube.

You'll need something more than usual to hold the phase plug in place, I suggest three countersunk screws through a big steel washer.

The steel screwdriver trick I use all of the time to remove filings from portable radio speakers. Cheap jewellers screwdrivers seem to work best. A bit of double sided tape on the back of the magnet will collect the drill filings from that side.

(Since I can't do any woodwork for a couple of months I'm starting on my amplifiers here: Active XO Bi-amping with Trends TA10.1 )
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Old 5th September 2007, 03:56 AM   #102
Kensai is offline Kensai  United States
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Yeah, Mike, just what I was thinking. Wasn't worried about the filings, just wondering if there was any other reason why it wouldn't work since no one seemed to have put it forth before.

The B20s already have a divot in the back of the magnet, dead center, and a ton of space inside the voice coil's perimeter once the dust cap is removed (but they sound really off without the cap if you don't have something inside to act as a phase plug or pseudo cap). I'm not planning to try this with my current set (they've got Planet10 phase plugs and my primary and eventual secondary uses for them like them phase plugged, not coaxed), but I may get a second set to experiment with. Got a project for someone else I need to do eventually.

So, anyone know, theoretically, what removing the B20's dust cap does to its T/S parameters? I notice it made them more authoritative at their very bottom end, not any further extended, but just some bit of level increase there in the bottom half octave before the response falls off a cliff (I'm running them OB with a good bit of EQ), but I'm not sure what changes in the parameters would happen to account for this. Just like to have some guides for siming this behavior.

Kensai
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Old 5th September 2007, 12:33 PM   #103
gychang is offline gychang  United States
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Quote:
Originally posted by Kensai

The B20s already have a divot in the back of the magnet, dead center, and a ton of space inside the voice coil's perimeter once the dust cap is removed (but they sound really off without the cap if you don't have something inside to act as a phase plug or pseudo cap). I'm not planning to try this with my current set (they've got Planet10 phase plugs and my primary and eventual secondary uses for them like them phase plugged, not coaxed), but I may get a second set to experiment with. Got a project for someone else I need to do eventually.

Kensai

Kensai: if u r going to do this, please document with photos since I may try it also,if the results are favorable.

gychang
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Old 5th September 2007, 02:59 PM   #104
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If you add in a chunk of dowel with the little tweeter on it to make it like a coax, will that dowel and tweeter still act like a phase plug to the B20?
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Old 5th September 2007, 03:14 PM   #105
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Quote:
Originally posted by davidallancole
If you add in a chunk of dowel with the little tweeter on it to make it like a coax, will that dowel and tweeter still act like a phase plug to the B20?
yes, althou with the dispersive qualities if a cylinder

dave
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Old 5th September 2007, 05:31 PM   #106
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Thanks Dave.
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Old 5th September 2007, 05:56 PM   #107
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Default Re: Veil has been lifted, shocking!!

Quote:
Originally posted by gychang
If you have been following the thread, I have been disappoinged with B20 in the Chang cabinet.

I installed the $5 tweeter pictured above, and with help from everyone I installed with 2uF cap, shockingly different sound. Clear and with airiness, can't believe the change in sound. First song was Lee Ritenour, Color Rit. I am sure those are steel wires on his guitar, twinge of high notes are shockingly natural. Truely spine tingling. I now know the other speakers I have been building is not in the same league. Compared to my reference "zigmahornet" with Dave Merrills drivers, it does not place the instruments in the space as well, but overall sounds more full, in particular orchesteral music is much better in the Chang. Without the tweeter, James Taylor had a touch of sinus condition, now he is cured. Do I seem excited??, yes shockingly so. Amazing what science and cheap tweeter can do.

gychang
How do they stand compared to a BIB? I realize your BIB's have smaller drivers, but is there any differences, likenesses, ect... Got wood in the garage, trying to decide what to build next!
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Old 5th September 2007, 11:05 PM   #108
gychang is offline gychang  United States
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Default Re: Re: Veil has been lifted, shocking!!

Quote:
Originally posted by zayne742


How do they stand compared to a BIB? I realize your BIB's have smaller drivers.

Yes, these cabinets are optimized for extension of bass mainly, I have never built the BIB with BOFU (8" Pioneer). I think the cabinet choice is somewhat depends on personal taste and perhaps home decor and what the real boss wants...

Personally, I like the Chang (especially with its name...), the cabinet and design is perfect for my taste. Blends very well with the house we will be moving to in few weeks (actually all I know is house will be a large house). I can tell u BIB does indeed work well in extending the bass and can look great in certain decor with proper finish.

I have no reservation in recommending the Chang with the combo of the 2 drivers as outlined above. I listen to them every night ( I shut the door in my room since I like them on louder side). I plan to build another set of the Chang or the Curvy Chang, but this time I will put the tweeter directly above the BOFU.

Both BIB and the Chang are winners in my book.

gychang
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Old 15th October 2007, 09:34 AM   #109
Variac is offline Variac  United States
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Default The Chang combo!

OK, I built a BIB with the Pioneer BOFU 8" driver :

http://www.partsexpress.com/pe/showd...number=290-045


and it sounded quite good. I was using an Aiwa Car audio mylar tweeter.

I then ordered this tweeter as recommended by Mr. Chang:

http://www.partsexpress.com/pe/pshow...r=275-025&CFID


Man!! that tweeter is great with the Pioneer!! I tried other values for the crossover cap (1.75uF, 2.25 uF , etc.) and 2.0uF is spot on for my room!

Mr. Chang deserve a Nobel prize or some such because this combo is spectacular!! (Godzilla suggested the 2.0 cap)

The speakers are very very good and I can't imagine anyone being disappointed. I built mine out of flakeboard (OSB) and total cost- with drivers was $100 for TWO speakers!!!

Have I mentioned how good they sound? with full, deep bass, clear highs, great mid tone- just amazing. A great introduction to DIY if you are starting out..

Variac..
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Old 15th October 2007, 09:44 AM   #110
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