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Old 29th August 2011, 02:08 AM   #1
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Default Bipole FR with helper tweeters

This weekend I have been playing with some FR drivers in OB configuration. The basic testing has been with some 12 University Sound Diffaxials with the Sphericon Tweeter. I like what I hear but the baffles are kind of large. I like the MJK idea of using 15 inch woofers crossed low. I also have a pair of AN Super 12 cast in the BR 2.8 cabinet that I do like a lot for Jazz and vocals. The AN's imaging is laser like. But when I listen to the OB, there is also decent imaging but the sound is coming from everywhere, it is quite nice.

So I have 8 RS 40-1354 laying around and decided to do a quick try of a bipole configuration. A used a small enclosure I had for another project (11hx9wx8d) and placed the drivers back to back, connected in phase. I then put a RS Linaeum dipole tweeter on top. To my surprise, it sounds really good too.

The question. Is there any advantage in using back to back drivers (in sealed box) to using a single driver in dipole? Both with a helper 15 inch woofer coupled to the floor? Is it a waste of one FR driver?

Thanks

Alfredo
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Old 29th August 2011, 02:51 AM   #2
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Bipole is quite different than dipole,

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Old 29th August 2011, 04:03 AM   #3
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Quote:
Originally Posted by planet10 View Post
Bipole is quite different than dipole,

dave
I understand the phases are reversed between the two and that there are different cancellations going on . I have not experimented enough to appreciate the sonic differences. So i should stick to the normal OB configuration?

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Alfredo
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Old 29th August 2011, 05:25 AM   #4
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Depends on room, taste etc. I've not taken to OBs, but have been a champion of bi-poles for some time.

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Old 29th August 2011, 06:20 AM   #5
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Thanks Dave,

Looked at your site, I do see you are a bipole champion. Nice stuff there!

When building a bipole, is it necessary to match the drivers? Could a better one be used for the front and a lesser one for the back just to create the ambiance. Maybe even with a lower spl?

Alfredo
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Old 29th August 2011, 07:03 AM   #6
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Not using the same drivers can cause some issues, i have used similar drivers (ie CSS FR125 + WR125) and would consider the latest Mark Audio CHP70 with CHBW70.

The cabinets are usually shared, so it is imprtant that bass loading is the same. Also one of the potential advantages of a bipole is to load the drivers push-push for active vibration cancelation, which also requires at least similar drivers.

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Old 31st August 2011, 02:33 PM   #7
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thanks Dave,

My test with the RS 40-1354 was in push push. Do you think any of your Bipole enclosures will work with these drivers?

Alfredo
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Old 31st August 2011, 04:35 PM   #8
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Except for Frugel-Horn, we are much of the "a box uses a specific driver" camp.

This becomes critical with optimum vented boxes, but there seems (to me) to be a bit more "squish" room with larger boxes like ML-TLs & horns. Id you can find a specified driver close in spec (Fs, Qts, Vas) to the 1354 then there is a good chance. Mind you, given that T/S parameters are a curve, and one can rarely be sure where on the curve someone elses measures came from, it can be a moving target.

Sometimes you just need to cut & try. I usually try to morph an existing box. These concept bipoles for 1354 were based on Brine's ML-V

Click the image to open in full size.

dave
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