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Old 6th August 2010, 01:42 AM   #1
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Default My 8-inch open baffle speaker

I have finally commited to a design for my first open baffle speaker and started a new thread as a continuation of this one here.

Its a tri-amped 3 way open baffle with BG neo3 , 8 inch mid (possibly an old visaton B200) and dual 8 inch woofers in a U-frame. Initial concept pics are attached.

Rudolf previously recommended the Visaton WS 25 E which has very good specs for open baffle use. I have been looking at the WS 20 E as possible 8 inch option. It has the same efficiency, x-max and higher Q of 1.14 but uses a polycone rather than paper. At A$40 each I believe it is good value. Will also consider automotive subs as suggested by Matevana. I will be using a DCX2496 and will EQ as much as possible to boost the bass response.

Baffle will be 23-25cm wide and approx 1m high. Not sure where to start in terms of sizing the U baffle so please fire any suggestions at me. I would like to have the option of sealing the u-baffle if i need better low end response in the future as in John K's NAO.

Due to the narrow baffle, I think the mid will need eq to get down to the desired 120-150hz before the woofers take over. I have modelled this in edge which shows atleast 10db boost is necessary to avoid a large dip at the crossover point.

Thoughts?
Attached Images
File Type: jpg OB1.jpg (24.5 KB, 1129 views)
File Type: jpg OB1 REAR.jpg (43.0 KB, 1065 views)
File Type: jpg edge sim 8inch 25mm.JPG (116.8 KB, 1057 views)
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Old 6th August 2010, 02:08 AM   #2
sreten is offline sreten  United Kingdom
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Hi,

Erm ... make your baffle wider e.g. say 12"/30cm to 15"/38cm and use a 0.6 ratio
driver horizontal offset to smooth the response. I cannot see your arrangement
working down to ~ 135Hz c/o point without some serious max SPL issues.

/Sreten.
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Old 6th August 2010, 02:45 AM   #3
tinitus is offline tinitus  Europe
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you could mount small hinged "wings" on each side of woofers

mid rolls off with more than caused by baffle, theres also dipole related rolloff

I dont know, how much power does it take, this mid
small voice coil, may not take much Eq

maybe place a good 10" just below mid, and raise xo point

and make bottom woofers low crossed subs, and in H-frame instead
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Old 6th August 2010, 03:42 AM   #4
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Before I cave in to increasing the baffle width over 250mm, lets say I can accept a 3db dip at the crossover point of 150hz. Edge says I need 4db of EQ to achieve this (see attachement). Does this effectively mean I am reducing my driver efficiency by 4db? If so i dont see this as a problem depending on the mid used.

I have also considered using the eminence beta 8a which has 95db sensitivity. Will I have a chance here or should I abandon this crazy anorexic open baffle crusade and start obeying the laws of physics?
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Old 6th August 2010, 04:31 AM   #5
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by dabbler View Post

I have also considered using the eminence beta 8a which has 95db sensitivity.
I would use a much smaller mid
but not so easy to find with good sensitivity
Alpha-6A might work too

and if Emminence, combined with Alpha-8A or 10A

using very simple filters

and active subs
if loud SPL, maybe with active low cut high pass on lower Alpha
I would consider something like Hypex dsp plate amp
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Old 6th August 2010, 01:03 PM   #6
sreten is offline sreten  United Kingdom
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Hi,

Its not just the frequency response, its also max cone excursion related.

/Sreten.
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Old 6th August 2010, 02:07 PM   #7
adason is offline adason  United States
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Hi dabbler,

I have recently finished my ...hmm...like fifth open baffle speakers and I used B&G Neo3 as tweeter (as dipole no back), I selected FF125K as mid (it matches sensitivity ~93dB with tweeter), so the advice from tinitus if great one, use smaller mid, and I placed it on top of 15" closed box woofer...I know, compromise in bass, not an open baffle, but its a good compromise, I am affraid in your arrangemnt you will not reach low enough.

I have not posted the pictures on the web yet, but I will. This is the best speaker I made so far over 20 years (it made me sell the Lowthers), the hight and mids are the best I have heard...and you can load it with power too. I biamp the system, thats another plus, I equalize the system, so its flat 30-20k. Very happy with the result.
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Old 6th August 2010, 06:27 PM   #8
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Hi Dabbler,

8" on 30cm baffle will work fine both SPL and off-axis polar response.

I have used the standard bunnings 29cm planks with great result. Then you are able to use 2x 10" woofers instead of 8".

http://gainphile.blogspot.com/2009/1...implicity.html

For the U-Frame I have used again, a standard 24cm planks from Bunnings. It's great SPL-wise but I prefer no u-frame.

I tried wings before but they create more issues than what being solved.

Knowing that you go active with the system I can see you'd get a successful result either way.

1m will be too short. Perhaps 115cm so that the tweeter axis is slightly above the ear. But maybe you have low couch

Edit:

btw. If you use 8" drivers, then in fact you can stack more of them ! I had such thought sometimes ago

Click the image to open in full size.
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Last edited by gainphile; 6th August 2010 at 06:36 PM.
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Old 8th August 2010, 12:10 PM   #9
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I am not sure why a smaller mid will be necessary. Maybe to get a higher xover point with the neo3?

Gainphile, I didnt realise bunnings sold those 29cm planks. That sounds like an easy option! Are these in pine?
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Old 8th August 2010, 12:28 PM   #10
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On second thought, 8 inch mid is beaming above 1.5khz and neo3 xover point is around 2.5khz. So I have a problem here.
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