My 8-inch open baffle speaker

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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?
 

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Ex-Moderator R.I.P.
Joined 2005
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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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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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
 
music soothes the savage beast
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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.
 
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/2009/11/s12-ob-open-baffle-simplicity.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

smallroomDipole.gif
 
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Looks good. In stead of using the EQ that EDGE shows, you could run a board just on one side back from the baffle board to how ever far back your wood cab goes. That has the same effect as making a wider baffle board and your drivers, in effect, would be off center. That is what I am doing and it makes the drivers appear to be on center on the face board but off center sonically. That way you negate the canclation and don't need the EQ.
 
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?

Yes the cheaper pines are 29mm wide. They are sold in 90cm, 120cm, and 240cm. They are cheap and looks great but you have to select carefully.

The more expensive option are better looking (can't remember the brand) but they are wrapped in plastic. These are 30cm.

Also, MDF is widely available but I found the quality are better at Mitre10. So normally I just ask them to cut those 60cm into two. I don't like the dust of these board though and always opt for the pine.
 
I like 8" drivers - the only reason to avoid them though is they have irregular polar patterns above say 800Hz. Only worry about that if you want a very smooth polar response.

I used to use the visaton B200 - and I wouldn't recommend it, unfortunately. It is an excellent speaker, but it has too little power handling. 40/70W according to them. I killed one listening to raw drum tracks - an expensive mistake. Also, you will never get a crossover around 120-150Hz with the B200 - it doesn't have the cone excursion or thermal power handling. Remember OB mid require a lot of EQ - easily 16dB at 200Hz for what you're looking at. Of course, you can do it if you limit yourself to quieter listening.

If you want a system that can play decently loud, you need to change course a little. You could use almost any mid driver if you move your XO up to 250-300Hz. You can keep it a three way if you used a sealed woofer below that, or accept relatively limited bass response from your OB woofers. To be honest, OB bass can be hard to do, as you need a LOT of displacement, just to get down to 40Hz. Two 8" drivers can't to it - two 12" drivers can.

What inevitably happens with serious OB designs is they become a 4 way: tweeter, upper mid, lower mid, and subwoofer. Although you need more equipment, the design requirements becomes a lot simpler. Some even become 5 ways.
 
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I think i will go down the path of a 3 way with sealed sub on 29cm bunnings pine board :D. The plan will be to get down to atleast 80 hz with the 2 x 10" woofers using minimal eq and up to 300hz to cross with the mid (no u-frame then). I think this should gove me all the flexibility I need as it strikes a good balance between SPL and decent dipole coverage - The worst room interactions in my small rooms are between 100 and 300 hz so id like to stay dipole in this range.
 
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The alpha 6A is on my list as a good value buy. Does anyone know how it compares to the pricier B&C pro drivers?

I have also had a tip off that the Audax PR17 have the sort of dynamics I am looking for, however its no longer available. Any modern equivalents?
 
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