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Old 26th February 2006, 05:29 PM   #11
grrr is offline grrr  Netherlands
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I forgot to say that i think it is a very nice and original idea adding horns or resonators or any means of lets say mechanical bass amplification to a openbaffle. In the near field there is indeed bass to be amplified.
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Old 26th February 2006, 06:20 PM   #12
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Something else I've tried, but haven't gotten it to work yet is to absorb only LF content of the rear wave. The perforated helmholtz absorber didn't absorb much at all, but I still want to try a slot absorber. Using that approach we should be able to offset some of the dipole bass cancellation and effectively increase bass response that way.
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Old 26th February 2006, 07:17 PM   #13
Corloc is offline Corloc  United States
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You might want to try to recogfigure the TL mouth like an open backed bouchhorn MK2. (see attached) I think if you put much of a Comp. chamber in back your going to loose most of what OB's bring out in the music.
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Old 26th February 2006, 07:50 PM   #14
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Corloc,

I couldn't agree more on the chamber vs OB. I've taken the U-baffle to it's limit with the driver I have and the current slot doesn't seem to take away from the OB characteristics. My drawing on the left above obviously would, but at some point a large hole with less depth wouldn't and I'm trying to figure out how to reasonably estimate that point.

My current thought process is to use the driver's natural polar response to capture a significant percentage of only the LF waves and channel that to the throat.

On my current version the mouth is only about 600 sqcm, so I butted it up against the corner of a heavy wood box to effectively expand the mouth and smooth the wave flow out of the corner (ala Ron's horn mouth deflectors) and that works very well.
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Old 28th February 2006, 04:14 AM   #15
Corloc is offline Corloc  United States
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I can't think of anything differant than the direction you are going. All i can suggest is tinker.

Hopefully someone with more physics and math backgroud will help out. I'm begining to think though your pushing to get to low a freq.

I'm trying to get mine to play solidly to 40hz. I figure that 90% of content anyway.

I hope it works out I have been proud own of B200's for a couple of months. I'm useing some of your suggestings for the baffle from the dark star thread. I'm still tinkering but they work quite well.

I'm also intested in if the Joint Chiefs idea would work with the B200.
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Old 28th February 2006, 05:05 AM   #16
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Quote:
Originally posted by Corloc
I can't think of anything differant than the direction you are going. All i can suggest is tinker.

Hopefully someone with more physics and math backgroud will help out. I'm begining to think though your pushing to get to low a freq.

I'm trying to get mine to play solidly to 40hz. I figure that 90% of content anyway.

I hope it works out I have been proud own of B200's for a couple of months. I'm useing some of your suggestings for the baffle from the dark star thread. I'm still tinkering but they work quite well.

I'm also intested in if the Joint Chiefs idea would work with the B200.
I want to think I could get close to 40hz with a Chiefs type U-baffle, however, when you look at their IB response from Visaton, reality sets in. I haven't heard back yet from the one B200 guy to whom I provided the secret to the Chiefs and gave recommended dimensions, so it looks like I have to get some myself. With the B200, which has a much more extended high end in the rear wave than my Iris's, I have a feeling the max depth for a Chiefs type baffle is going to be 10" , maybe (fingers crossed) 12", before they start closing in the sound too much. I'm getting away with a 16" max depth for the Iris's resulting in an Fequal around 72hz and their .91 helps achieve some solid extension to Fs at 41hz.

With B200's and the compact Chiefs cab we're realistically talking about 60hz and fill needed below that for near flat response. Sure there will be output down to Fs, but no way Pink Floyd, etc. will be satisfying. I do believe that a U-baffle about the size of the 2 boxes your B200's came in stacked together, with one of these OB-RLH things as the stand for them, that 35-40hz performance is possible, maybe even 30hz with corner help due to the longer "horn" length available.

Right now I'm using the Iris woofer in a Chiefs-RLH cab, with a Fostex 108sigma on a small OB as a main driver, and I'm actually having to tone down the bass because the 108 is less sensitive. If I can use a B200, retain the open sound, and get extension that makes Pink Floyd satisfying at levels approaching 100db, then I'll be done.
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Old 3rd March 2006, 04:41 AM   #17
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I have to say. I had a brain fart. I forgot that the silver iris was coaxil. I think with very little high and middle freq. coming from behind the Chiefs-RLH cab will work better for the iris than the B200.

Fostex uses a simular idea for the fe126e, http://www.madisound.com/pdf/fostexcabs/fe126e_encl.pdf
The question still in my mind is witch do you solve for first BR or Horn?
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Old 3rd March 2006, 04:47 AM   #18
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O' I would be intrested in the joint chiefs for the B200. I have a sheet of 3/8" ply that has been sitting in the garage for a year or two. I'm shure that my wife would like it out of the way.
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Old 3rd March 2006, 05:08 AM   #19
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Quote:
Originally posted by Corloc
I have to say. I had a brain fart. I forgot that the silver iris was coaxil. I think with very little high and middle freq. coming from behind the Chiefs-RLH cab will work better for the iris than the B200.

Fostex uses a simular idea for the fe126e, http://www.madisound.com/pdf/fostexcabs/fe126e_encl.pdf
The question still in my mind is witch do you solve for first BR or Horn?
Easier...probably, but I'm not sold on better yet. The sound may not be wide open, but it will be more open than any box speaker no matter what. My rear shape handles dispersion, 1/4 wave resonances and travel distance differences around the baffle in one fell swoop. The old time open back speakers had great results even without considering these things.

Re the Fostex 126 box- I don't think the order matters. The port will act like a port put on an aperiodic box and at other frequencies the CC will act a lot like it's sealed.


Quote:
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O' I would be intrested in the joint chiefs for the B200. I have a sheet of 3/8" ply that has been sitting in the garage for a year or two. I'm shure that my wife would like it out of the way.
I finally ran across a pair of used B200's for sale. At least 2 design's will come out of that, so you'll have to wait for about a month, because I'll be my own guinea pig.
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Old 6th March 2006, 02:45 PM   #20
Corloc is offline Corloc  United States
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Quote:
I finally ran across a pair of used B200's for sale. At least 2 design's will come out of that, so you'll have to wait for about a month, because I'll be my own guinea pig.
Fair enough, good luck, and I'll be waiting for your impressions and data.
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