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Old 26th October 2008, 08:19 PM   #1
Pete_P is offline Pete_P  United States
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Default any DIY dipole surround plans?

Searching the forums there are some threads and some discussion/pictures, but I didn't see any complete plans for them (yet).


I'm looking to use a pair of dipole's (big company definition) as surrounds for my really budget theater, something similar to Paradigm ADP's or Kef iQ8ds. I like the kef's and can get them for a great price, but I'd rather go cheaper. Plus if I get the kef's then I will want to change the Infinity front end to kef's to match and that really blows the budget out of the water.

Anyway I want to build a set, preferably an already designed model since my speaker building knowledge isn't up to the task. I'm not looking for perfection, just good enough for surrounds in a theater.
Theater room is 15x12 and will be pretty much 100% movies and games, maybe a little music here and there but nothing important.

I was thinking of keeping it simple and using something similar to the hi-vi B3N/S for the dipole design, which means this thread would be better suited in the fullrange forum. But I did see a picture of a dipole using the Tangband's with a 3rd woofer for lower frequencies that looked suitable also.



Does anyone have any plans for this?

Will 3" fullrange drivers be loud enough/up to the task of surrounds when matched with an Infinity front end (6.5" towers and an 5.25mtm center)? I'm guessing my application/expectation yes, but if I ever upgrade in the future when budget allows then no.
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Old 1st November 2008, 03:58 PM   #2
Pete_P is offline Pete_P  United States
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Okay, this thread should officially be in the fullrange forum now, so if a mod could move it over ...



Since my speaker building knowledge is not up to par yet, I'd prefer to stick to a fullrange with no crossover to get my first project out of the way and hold me over until I actually learn more proper theory. Did some more searching and I am looking at the current drivers below:

HiVi B3N or B3S
Dayton RS100-4 4"
Or one of to many to list TangBand 3" fullrange

I'm leaning towards the HiVi only because they are cheaper then the others and I won't feel bad if I screw this up. Or if I'm not happy with it I could pull the drivers, build zaph's design with them and use them somewhere else.

My goals with this project is small budget, on-wall commercial style dipole for a home theater, decent sound to hold me over until I can design/build a better pair or find a great deal on a commercial set and get my first diy project over with.


So with my goals:

1. Is this a reasonable speaker choice for my application, or should I consider a 2-way system more?
2. Are these speakers/design going to have enough output for a home theater application?
3. Any other questions I should ask but can't think of?
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Old 3rd November 2008, 02:15 AM   #3
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I think you're looking for a BIpole design, not DIpole?

I wouldn't hesitate going with some Hi-Vis, as you mentioned. I would use two per speaker, wired in parallel to keep the impedance around 4 ohms. They will probably be up to the task, especially if you can set the surrounds to 'small' on the processor. (I like my single 3 inch TB as a center running full range in a sealed box, but I chose it for the cast frame.)

You need plans for a simple sealed box? This is your chance to be creative!

If I needed new surrounds, I wouldn't make boxes, but would make a triangular baffle for each driver and stick them in each rear corner/ceiling and experiment with the spacing to the walls (but these would be sort of dipoles with the rear wave coming out the gap).
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Old 3rd November 2008, 03:57 AM   #4
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Default Re: any DIY dipole surround plans?

Quote:
Originally posted by Pete_P

I was thinking of keeping it simple and using something similar to the hi-vi B3N/S for the dipole design, which means this thread would be better suited in the fullrange forum. But I did see a picture of a dipole using the Tangband's with a 3rd woofer for lower frequencies that looked suitable also.
You want to read Vance Dickason's Loudspeaker Design Cookbook. One of the sixth edition sample designs is a home theater system with dipole tweeters on the surrounds.

You don't want to run the speakers as full-range dipoles, the problem being that the acoustic short circuit between front and rear drivers causes a 6dB/octave roll-off with decreasing frequencies once the path length reachs .17 c/D with D the path length difference and c the speed of sound. This creates a lack of bass.

The usual approaches are at least a two way where the bass driver is run conventionally while the high frequencies are dipolar (as in Vance's design) or two separate sealed speakers with a high-pass filter on one.
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Old 3rd November 2008, 12:34 PM   #5
Pete_P is offline Pete_P  United States
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Default Re: Re: any DIY dipole surround plans?

Quote:
Originally posted by Tosh
I think you're looking for a BIpole design, not DIpole?
No, I meant dipole, just the big box company definition which is usually a 2-way wall mount firing front and back, 45 degree off the wall and either a rear woofer or tweeter fired out of phase.


Quote:
Originally posted by Drew Eckhardt


You want to read Vance Dickason's Loudspeaker Design Cookbook. One of the sixth edition sample designs is a home theater system with dipole tweeters on the surrounds.
(im)Patiently waiting it's arrival.


Quote:
Originally posted by Drew Eckhardt

You don't want to run the speakers as full-range dipoles, the problem being that the acoustic short circuit between front and rear drivers causes a 6dB/octave roll-off with decreasing frequencies once the path length reachs .17 c/D with D the path length difference and c the speed of sound. This creates a lack of bass.

The usual approaches are at least a two way where the bass driver is run conventionally while the high frequencies are dipolar (as in Vance's design) or two separate sealed speakers with a high-pass filter on one.
Thanks for that info.

The separate sealed speakers with a high-pass sounds interesting.
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Old 3rd November 2008, 10:32 PM   #6
pjpoes is offline pjpoes  United States
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You probably found my post on a Tripole clone surround. I thought I gave enough information to construct a complete and similar surround.

Anyway, since this is being discussed left and right in numerous posts, I just posted a series of links to some discussion on surrounds I have had with Dr. Geddes which often also includes my own conclusions given my various "experiments" into good surrounds. He recomends using a pair of 8" drivers. This is in the Setting up the Nathans page.

If I was to try and build something which matched both Dr. Geddes basic ideas, Vance Dickensons concerns, and was all made to fit into a small (say .25 cubic feet) enclosure, I would probably place an 8" pro midbass (for high efficiency and low compression) mixed with two smaller full range like drivers run on the sides, wired out of phase, and given a small highpass filter at say 3-500hz. This should allow for in room bass down to 100hz or so, dipole or bipole omni-direcational midrange operation, with rolled off highs.

My favorite 3" full rangers are the peerless units, but Tangband also makes some great ones. The high frequency ability of those drivers is, however, not needed, which is one reason why I would use the peerless instead.

I know you said no crossover, but really, we are talking a simple capacitor inline with those full range drivers, so it won't require much work. These are surrounds, they don't need to be perfect.
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Old 1st November 2009, 11:54 AM   #7
JvS is offline JvS
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I'm currently designing something similar. I also want a dipole, but I found a fullrange driver not to be powerful enough. Especially using it in dipole setting, there just won't be any low frequencies.

That is the reason i'm tending towards a really small FAST speaker. I want my surrounds to be flat and sleek. The design I have in mind now is a Peerless 830945 (5 1/4" subwoofer) in a 2L BR@80Hz enclosure with 2 2" wideband speakers in dipole configuration, crossed over @ around 400Hz. An alternative could be de Dayton RS125 in a 2L sealed enclosure.

I already designed an enclosure It's 20x30 and 11CM flat. In this design it has two 1,9L enclosures. In my new design I want to use it as one 3,9L enclosure with the fullranges enclosed in a ,8L 'cap'.

Now my quest is: which fullrange driver should I choose for the 400-15K Hz dipole configuration.
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