Designing an OB with high WAF

[Zepticon]

Hi=)
I am a hi-fi interested design student with an assignement to make a OB dipolar speaker system with high WAF. IM at my 5th year now, and im gona write my master thesis after christmas. I have been looking around the net for inspiration, and i keep coming back to the Jamo R 907, as one of the reference speakers when it comes to OB design and aesthetics. The only problem with the Jamo is that its expensive. My target area is the $2000-$4000 range.

So far i have been lurking around here on the forum trying to learn what i can about OB's, but unfortunately, some of you guys are operating on a level way over my head, so i cant make much reason of the really interesting discussion I understand about half of it

The designs i am playing with at the moment have a baffle size smaller than the subwoofer, somewhat like the Jamo. I have read that the size of the baffle is important if you want to reach low frequencys, but i guess the ones im making have such a small baffle that its not making any difference. Im thinking of using 3 or 4 drivers. A tweeter, a midrange, and one or two (three?) subs, depending on size and what you can recommend.

Also, i prefer to use SEAS drivers, since its a Norwegian operated company (i am norwegian), and it would give me some "free" marketing and sales arguments. Its not a very big deal tho, just a preference. Quality and sound is what matters.

So i need help with the technical bits:

Subwoofer: So far, for the subwoofer, i have understood that fs and smax should be "low", and that the Qts should be "high". But what kind of numbers are we talking about? i dont know anything about either fs, smax or QTS so i don't know what high and low values are. Anyone got some examples?
Also, is it better to go with one big? 12-15" or multiple small ones (8" or 10")?

Midrange and tweeter: Is there anything special to think about regarding this? will any midrange and tweeter for a normal "box" speaker work or do i need some special stuff for OBs?

Filtering Circut:
I'm not sure if i am required to come up with a filtering circuit and data-sheets for it on my assignment, but i want to learn a bit about it anyway. When i have chosen drivers, is there software available for calculating the filter or does it need to be done "manually"?

[c2cthomas]

Designing an OB with high WAF

I wish you the very best of luck with your project!!! Designing an OB that meets your listening requirements is challenge enough in itself - but for some ideas take a look at this link for some ideas.

Ultimate OB GALLERY

OB's are large and to sound their best need a bit of space away from the walls - aspects that many spouses and partners dislike. YMMV.

If your wife is tolerant of speaker size and placement - and actually enjoys listening to music then you at least have a chance. If your wife likes speakers that are small and pretty - well - then you have some hard decisions to make. Marriage counselors and divorce attorneys are expensive - thus the creation of "man caves".

Here is another link that relates to your concept - True WAF speakers

[Flaesh]

all my girlfriends are\were absolutlely tolerant of all my speakers..
in my flat..

[jrenkin]

I have been watching and reading a lot about the open baffle experiences on this forum. Built some simple ones.

I think that if WAF depends on not having crazy big baffles, which is likely, you need to be ok without deep bass or use OB with some other sub enclosure.

My simple ones, really 2 way with a FR (jxs 92s,no xo) and small bass woofer (some cheapish 8" from PE with a 1st order low pass at about 300hz), have nice integrated and fast bass to maybe 65-70Hz then it drops fast. The baffle is only 20" wide with some support wings at the level of the woofer.

I think if you want to go deeper, you have to get wider, much wider and use bigger woofers. There are a few baffles like mine for the FR that sit on top of a 15" H frame. They say they go low, but they have much less WAF.

So I think if you need both WAF and BASS you need an enclosed sealed or ported sub, like several of the designs on the OB gallery thread show.

[Zepticon]

Bass is not a priority no, WAF and aesthetics is the most important after sound quality. you can get small enough subs to hide under a table or something similar, in a box.

[John Bsuch]

Ah… Where to begin? Like designing - building a house from scratch, there are some up front decisions that need to be made. Your job will be much easier AFTER you better define what you really need to accomplish. You are off to a good start with your two major decisions, your WAF consideration(s) and budget.
Here is a short list that can help you start your design journey:
Do you want to employ all passive or active crossovers? Or active on the bass end and passive on the mid range and tweeter?
What is the largest baffle you think can pass a WAF test?
How much bass extension and how loud to you need the finished system to play?
Is there a particular room you will be using this design in?
What wood working or electronic skills – experience do you have?
What amplification do you intend to use?
Are there any other major goals or limitations that must be factored into the design?
There will be more issues to deal with after you answer the above, as things evolve, more decisions will have to be made. And of course, there will be a lot of differing opinions on each aspect of your design, no matter which direction it takes. It will be interesting to see what advice is offered as you progress.

[Radugazon]

Hi Zepticon...

For sure that's a double problem, but dn't worry you gonna found something.

Already, a simple H-Frame for a 15'' is not that big, 50x50x38 outside (cm)

more good info here http://www.quarter-wave.com/OBs/OB_Design.pdf

and of course here Offene Schallwand (OB) (last one, english version)

be ready to think of equalisation...

[Helmuth]

Two options

1 make it so big you do not see them.
2 make them so small you do not see them.

WAF means wife's do not want to see speakers in the room what they see as their territory. Or you need to have a intelligent woman that also understands. That good sound is of highest importance.

[el`Ol]

The question ist why do you want OBs? From my point of view stylish narrow OBs together with a conventional sub are worst of both worlds: Boxed bass and unnatural imaging caused by reflections in the wrong phase.

[mige0]

As this seems to be your first speaker project - I'd suggest you to go with a "out of box" design first and use that as a reference for a subsequent "from scratch" project.


As a good starting point have a look at John Kreskovsky's NAO designs here :

NaO Note preview


or have a look at John Bsuch's design here:

Fast, fun, Inexpensive OB project


I'm pretty sure to walk *that* road will be much more rewarding at a very quick time scale, less disappointing / frustrating and way cheaper in the long run as well.

Michael