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Old 14th July 2006, 06:49 PM   #1
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Default Double Bass Reflex.

I just built a set of DBR's and am thoroughly impressed. I used the old standby W3-871's from Tang Band. I can't believe the amount of clean balanced bass that can be achieved in a 7x11x9 inch box. I keep having to check to make sure that I don't have a set of my larger fostex boxes running. Anyone else had much experience designing these? My first shot at a design is a success and I plan on designing some enclosures for my 127's this weekend.
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Old 17th July 2006, 01:54 PM   #2
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Hello !

Another guy who was able to get bass from these nice cheap drivers ! Good work ! Have you got any photo ?

I used a bit different way to build mines : a big ML-TQWT. See my website if you're interested !
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Old 17th July 2006, 09:40 PM   #3
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I`ve built the Fostex recommended double BR for the FE127`s and had the same reaction. I made the boxes about a foot taller and filled the bottom chamber with sand to act as an integrated stand for floor mount. I made these for my GF and they`re hooked up to a cheap Onkyo receiver and mainly used for video, but I was very happy with the sound. I have a pair of FE207E`s in a large BR box and will eventually build the Fostex recommended double BR because I was so happy with the smaller ones. She has them on the sides of a 32" TV in the corner and the bass that little driver makes is tuneful and extended. When I pull off the grilles to show people what`s inside they can`t believe it. "Testimonial from another satisfied customer."
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Old 18th July 2006, 12:07 AM   #4
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I will post photos soon. The boxes though are only 11 high x 7 wide by 9 deep. All in inches. I noticed in another thread that someone (SM) stated that he couldn't get rid of the variations brought on by the dual chambers where they collide. This confused me as DBR boxes are known for flattening out the frequency response more so than standard bass reflex speakers. Short of a small 8 db null from 100-130 Hz, (Which is room mode dependant), my response is surprisingly flat. Moreso than a BR with this driver. I believe that what some people refer to as the small chamber vs. the big chamber problem is just that. You do not need a drastic difference in chamber size, only the tuning of the chamber. I find that if I simulate it with a larger secondary chamber that the freq. resp. begins to flutter. Comparing these boxes to the Needles that I originally built for the TB drivers, the bass is cleaner and smoother. When they are placed 8" from the wall, the bass response increases quite a bit as well. I can easily listen to them without the need for a sub. Not bad for a sub-bookshelf variety speaker. I have been trying different tunings for each chamber as well and am compiling data on the subjective as well at the scientific findings.
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Old 18th July 2006, 03:05 AM   #5
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DCR designs sound very interesting. Does anybody know of any simulation programs that will graphically show what the excursion and FR response are doing in a DCR box? I've looked online and I've heard that lspCad will do it, and I have the demo version..... but it's way over my head how to design/layout such a box. Does anybody know of a simulation program (or has anybody designed a system in lspCad & is willing to share it?)
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Old 18th July 2006, 01:55 PM   #6
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Hi

Martin J. King's Mathcad worksheets will simulate DBR or DCR systems.
Go to http://www.quarter-wave.com/ and click on 'Upgraded MathCad Computer Models'

best, LC
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Old 19th July 2006, 12:23 PM   #7
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Actually, what I am simming my DBR's with is Martin King's worksheets. They have worked very well thus far. I will keep everyone posted as to my progress.
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Old 19th July 2006, 03:11 PM   #8
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I built a pair of DBR's using Fostex FE83's.
http://web.mac.com/noteldov/iWeb/DIY...C6545F1E9.html
As expected, great mids and highs but the bass was almost non existant. I had to mate them with an active sub. With little bass the soundstage was also pretty shallow.
I could not get over how fast and dynamic the speakers were though. Even with little bass they were great near rnage speakers and if you like jazz I owuld give them a go.
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Old 19th July 2006, 03:40 PM   #9
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Quote:
Originally posted by Harderror
Actually, what I am simming my DBR's with is Martin King's worksheets. They have worked very well thus far. I will keep everyone posted as to my progress.
I've looked at Martin King's worksheets, but it appears as though you have to pay to access them... is this correct? Does anybody know of a free way to simulate DBR/DCR's. (I'd still like help simulating it in the lspCad demo).
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Old 19th July 2006, 06:11 PM   #10
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Quote:
Originally posted by LightwaveDude


I've looked at Martin King's worksheets, but it appears as though you have to pay to access them... is this correct? Does anybody know of a free way to simulate DBR/DCR's. (I'd still like help simulating it in the lspCad demo).
$25 for God's sake! You want ten years of hard work out of the man, and you begrudge him a little return on his efforts? Pay the man his dues and get the REAL answers to your problems.

Bob
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