Pioneer B20 Coaxial Tweeter Install

[db6546]

I just modded a B20 to install PE 275-025 tweeters and I thought I'd post some pics. It's a cheap and dirty method, but maybe it will give you guys some ideas.


First cover the basket with tape. I used low-tack masking tape.


To keep metal shavings out of the voice coil I made a piece of wood to fasten to the magnet. I bolted it to the speaker basket and a few layers of double stick tape provided a gasket between the magnet and wood.

The drill bit brings out the metal shavings and then breaks through to the wood. I coated the side walls of the hole with 5 minute epoxy to encapsulate any shavings BEFORE removing the wood drilling jig.





After drilling, cover the tape with more tape to capture any shavings. Take all the tape off as one unit.



Cut a 1" long piece of 1.250 dowel rod. Drill a hole from the top edge to the center of the bottom. Then trim away to make room for the tweeter leads.




The dowel is too small, so glue on a couple of layers of file folder. I used wood glue.



To get it to final size and make the socket to hold the tweeter, glue on 3 or 4 more layers. I think they were about 7/16” longer than the wood dowel. Once dry, the file folder layers are very hard and stiff.



Solder on leads, thread through holes, and glue on tweeter. I used a black marker to color the file folder black and then glued it to the speaker. It’s a big improvement.

[gmilitano]

Very nice!

[Variac]

I don't see how it could be done better than that! Congratulations!

Too bad Audio Express increased the price of the B20 to $30 and doubled the price of the tweeter...

Mark

[db6546]

Thanks, guys.

Yes, the price of the tweeter took a big jump. I think I paid less than 5 bucks.

[T11]

You took time!

I did the same to my eminence 12lt just week ago, and also tried to do that to FE206E but as they are in front horn it was all messed up!

I have one question for you- did you time align them? I tried several position on eminence, and milimeters were crucial. I tried at first with pink noise but it was too difficult for me to say/hear which position was best... When I moved (oh, I am using one cheap but bot so bad neodym Monaor tweeter- the only small and effiecent enough for beta 12lt, and yes they are now wheezerless, hehe - I crossed it around 7500Hz) the teeter away from throat the highs opened up, but the vocal was not so integrated-to me it was as ordinary two way but when moving inside the vocals become more coherent but harder (not hard but in comparison to the previous position less soft and lofty, shimmering).

Try it! It will be rewarding...
But maybe you crossed them higher then me and it doesn´t have so much influence on sound?

!!
T

[planet10]

I should do an experiemnt with the B20 and the little apexJr tweeter... it works well with a 2uF cap, just a question if the efficienies match... it would also need a bit of surgery (easily done) to be used on a phase plug.

http://www.apexjr.com/speakerstuff.html



dave

[db6546]

No, I didn't time align the tweeters. I'm going to use these in a classroom and didn't think that a bunch of kids would know or care.

Plus, I'm lazy and impatient.

I'm crossing the tweeter with a 2uF cap as has been recommended here on the forum.

I am debating removing the whizzer. I can hear somewhat of a cupped sound on vocals. But I don't want to lose my highs.


BTW, I have a pair of 12-LTA that I'm going to be experimenting with later. I'll try your suggestion then.

[Variac]

The LTA BBBIB's I made are dociumented here:

http://www.diyaudio.com/forums/showt...52#post1569852

I will be hard to find a tweeter with enough output that will fit on the center pole of the driver I think..

Mark

[norman bates]

I removed about 1/4 of the whizzer, the cupped sound did decrease, so did some of my highs.................... carefull, this is irreversible territory..............

I found a huge box (qtc .577) had better mids than the recommended qtc .707 I never noticed the cupped sound when it was in a bare 6ft3 box.................... Then again that was using a LR 24db crossover at 5khz.............. When b20 run wide open, the cupped sound is right there. Once you know it is there, it is always aggravating...........

You should but some cotton batten between the cone and the whizzer.

When a tweet is infront of a woofer, the only way to time align it is to use a digital delay.............. Or a tricky all pass delay passive circuit.........

Norman

[Variac]

If you remove the whizzer, you will probably then need a "real" crossover, not a first order single cap.

I would try stuffing around the whizzer , in the whizzer,wisps here and there.. Maybe a thin bit of sealant around the edge of it. The beauty of the whole thing is that you are only out $30 if you destroy
it.Of course the drilling is a lot of work to redo. In most cases you NEED the whizzer.

It should be possible to have the tweeter back far enough to align them, From what I understand the tweeter doesn't have to be at he back of the BUFU cone, more like half to 3/4 of the way back. With the file folder tube approach, it should be possible to make a telescoping tweeter mount and try different extensions.Throw some stuffing in the telescoping tube though to diminish resonances.

Mark