FR/WR125 bipole question - diyAudio
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Old 4th February 2006, 05:17 PM   #1
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Default FR/WR125 bipole question

I plan to parallel the fr125 and wr125s to keep the impedance up. . If i place an 8ohm fr125s on front of cabinet and a 16ohm wr125st on rear will the output from the 16 ohm be lower and by how many db?
Sorry this is probably a simple question that has been asked before. I want the rear driver output to be lower so that a smaller percentage of sound is reflected. My rear wall is hard and I can't move speakers away from wall too far. Not sure what level of attenuation will be correct so I may also put an L pad on the rear driver.


I/ve also considered placing the second driver on the sides of the cabinet, firing at the sidwalls which are about 6' away. Has anyone tried this?

What I am trying to accomplish is to widen the sound field, particularly for 5.1 movie effects.
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Old 5th February 2006, 11:27 PM   #2
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Did you get this idea from the David @ Plantet-10 (check out the box plan library - sealed boxes )? If not, you're thinking right down his path. They have built these, with a FR125 on one side and a WR125 + ApexJr SuperTweet on the other. They were after a bipole design for these and wanted to compare the FR to the WR with augmented high frequency. The WR + ApexJr is very well liked and has better bass than the FR.

I'm building a pair of these right now but with a slightly modified cabinet (mass chamber built in). I'll be using two WR125ST (the 16-ohm speakers) in parallel to bring them down to 8-ohm with one of the Supertweets on the front.

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Old 6th February 2006, 02:09 AM   #3
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Default I was wondering about side mounting

I have seen the bipole designs that you mention. But I don't recall seing anything about using the 16ohm driver as the rear driver to reduce output from the reflected driver.

Also really wonder what effect there would be in mounting the rear driver on the side of the cabinet.
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Old 6th February 2006, 10:54 AM   #4
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Default Re: FR/WR125 bipole question

Quote:
Originally posted by johnmark
Not sure what level of attenuation will be correct so I may also put an L pad on the rear driver.
Somehow I believe L-pads are not suitable for woofers. If you try it you should probably use very high power handling resistors.
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Old 8th February 2006, 07:18 PM   #5
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Default what about mounting rear driver magnet out?

If rear driver were mounted magnet out (facing the wall), this might eliminate some of the early reflections off the wall.
I assume it would also limit some of the higher frequencies from the back speaker output. I wonder what the effect would be on the baffle step compensation from the rear driver in this configuration?

Has anyone built a bipole with the rear driver magnet out?
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Old 9th February 2006, 06:18 AM   #6
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I like the idea and I think the bsc from the rear driver would work perfectly well. I dont recall seeing many spl measurements of reverse mounted drivers, but it would be nice to see how much it limits the higher frequencies.
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Old 9th February 2006, 06:28 PM   #7
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I'll report back after I build my "test" unit.
I wonder if removing that big steel can on the back of the WR125ST would be possible. Having that steel can on back worries me alittle, it will probably radiate some un-wanted noise. Maybe I can wrap it with some hi density foam.
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Old 9th February 2006, 08:39 PM   #8
AJinFLA is offline AJinFLA  United States
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Quote:
I like the idea and I think the bsc from the rear driver would work perfectly well. I dont recall seeing many spl measurements of reverse mounted drivers, but it would be nice to see how much it limits the higher frequencies.
I have done this in the past with bipoles (woofers mainly, not fullrange). The reverse mounting forms a nice acoustic low pass (but not perfect) that can be adjusted using just the right amount of damping fill to get the desired BSC. If I were to do a box bipole with 2 identical drivers, this is how I would do it. A low pass filter without the components. Sorry Landroval, no SPL traces saved for the drivers that I used. It of course depends on the driver itself.
I measured the rear response of my dipoles (OB) also, but thats a whole other story

Cheers,

AJ
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Old 9th February 2006, 08:44 PM   #9
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Any idea where the low pass is approximately starting to take effect with drivers like the FR125S with big magnet assembly and shielding?
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Old 9th February 2006, 09:31 PM   #10
AJinFLA is offline AJinFLA  United States
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No. But my 5" Tannoy ICT's rolled off nicely above 1-2k, fairly steep slope. Might be similar. There is simply no way to tell without measuring the particular driver and sorry, don't have a FR or WR125.
It may not be perfect, but its definately worth a shot IMHO. Again, if I were doing a bipole, this is how I would do it.

Cheers,

AJ
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