bipole speaker selection advice

[Salsero]

Thanks for those who helped in my previous thread. I am thinking of building a bipole full range speaker using the Tang-Band W4-1320SB drivers for the front. I assume using them for the back would be alright. However, I wonder the following: The bipole will address BSC nicely - BSC is a low frequency effect and the bipole will augment the low frequency response. Is it best to use the same driver for the front and rear or would it be better to use a driver with a better low frequency extension for the rear speaker?
I am hoping the lower frequency rear driver will provide a nice bass extension. Based on a limited understanding, I also wonder if the addition of a full range rear driver will provide too much mid-range and highs. The sound (mid and highs) must radiate somewhere.
I don't want to introduce a cross-over or any other passive components so driver matching may be tricky. I hope this idea is clear, if not and you decide to help out, feel free to email me.
Thanks
Salsero

[Jim Griffin]

You may find my design write-up on a set of CSS FR125S/WR125S drivers configured in a bipolar arrangement worth reading. A kit for these speakers (less cabinets) is available through Creative Sound. See the plans at:

http://homepage.mac.com/tlinespeaker...LDesignPak.pdf

I would use the same drivers front and back (in my case the FR and WR version of the drivers are virtually identical except the FR version extends full range vs. about 15 kHz for the WR). The sound fields of the two drivers overlap in the bass to mid-bass region (no BSC required) but as you go upward in frequency their two sound fields don't overlap (4 pi to 2 pi radiation). You do have to watch the reflection from the wall behind the speaker as you can get too much ambience effect for your taste.

[djn]

Hi, I have not experience with Bipole speakers. What are the advantages? Cheers.

[edjosh23]

If you place the rear driver on a baffle with the same angle and at the same hight your will not only have active BSC but also active vibration cancellation. I recently built a pair of Bipolar floorstanders in an Onken Stylee enclosure with the TB W4-1052SA. You can find a picture and model in the Full Rangle Photo Gallery.

Josh

[hm]

Hello,

if you take the back driver invers,
you get only frequencies up to ~ 2 kHz.

[edjosh23]

hm,

If i understand you correctly, that would work, but the rear driver would have reverese polarity, othersize you would have a dipole instead of a bipole.

Josh

[chrisb]

Originally posted by Jim Griffin
You may find my design write-up on a set of CSS FR125S/WR125S drivers configured in a bipolar arrangement worth reading. A kit for these speakers (less cabinets) is available through Creative Sound. See the plans at:

http://homepage.mac.com/tlinespeaker...LDesignPak.pdf

I would use the same drivers front and back (in my case the FR and WR version of the drivers are virtually identical except the FR version extends full range vs. about 15 kHz for the WR). The sound fields of the two drivers overlap in the bass to mid-bass region (no BSC required) but as you go upward in frequency their two sound fields don't overlap (4 pi to 2 pi radiation). You do have to watch the reflection from the wall behind the speaker as you can get too much ambience effect for your taste.

In an attempt to demonstrate the difference in cabinet materials (i.e. BB ply vs MDF) , I built a couple of pairs of a very similar design to Jim's a couple of years ago.


http://homepage.mac.com/tlinespeaker...es-collage.jpg

The gorgeous Douglas fir cabinets with WR125s and tweeter were by Scott Dunn

With appropriate room placement to allow for the breathing room he describes, they create a huge soundstage, and more bass weight than you'd think possible with just 4" cones. Used in conjunction with a surround processor with full bass management and a powered sub, and you've got the start of a substantial HT system.

[hm]

Hello,
thats right change the polarity,

one point is possible,

by invers montage it might be to reduce K2?

any opinions?