Designing an OB with high WAF

Zepticon

Member
2010-11-27 11:36 am
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 :D I understand about half of it :D

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"?
 
Designing an OB with high WAF :rofl::rofl::rofl::rofl::rofl::rofl:

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.

http://www.diyaudio.com/forums/multi-way/123512-ultimate-ob-gallery.html

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". :rolleyes:

Here is another link that relates to your concept - http://www.diyaudio.com/forums/multi-way/176084-true-waf-speakers.html
 
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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.
 
OB design decisions

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.
 
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.
 
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 :

http://www.diyaudio.com/forums/multi-way/163072-nao-note-preview.html


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

http://www.diyaudio.com/forums/multi-way/110583-fast-fun-inexpensive-ob-project.html


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
 
el'Ol, ure technically absolutely right, but looks like our young friend has to to create some "high WAF OB" for the needs of his end of studies thesis, so no choice about the design and this theme.

If not so, of course, better to go for huge speakers and change the girl friend for a slimmer one, than the opposite: big wife and tiny speakers.
 

Zepticon

Member
2010-11-27 11:36 am
Do you want to employ all passive or active crossovers? Or active on the bass end and passive on the mid range and tweeter?
My plan was to run with all passive crossovers. I not sure what the english terminology is, but i guess it means that i have the amp - filter - speaker

What is the largest baffle you think can pass a WAF test?
Im not sure, but looking at Linkwitz Orion, they are pushing it in terms of size.

How much bass extension and how loud to you need the finished system to play?
Not very loud. Its a music system first off all, and i think most people enjoy music when its at a pleasant volume. Its not gone be used for Home Cinema or such where volume is important.

Is there a particular room you will be using this design in?
A regular livingroom. The goal is to make em so that they fit in with a normal flat panel TV and the rest off the usual AV equipment.

What wood working or electronic skills – experience do you have?
Im experienced with woodwork, and my practical electronic skills are average (i know how to solder and such) but my theoretical electronics skills are not to good. I ahve friends who can help with this if needed tho.

What amplification do you intend to use?
Something like this: XTZ | Sound in balance

Are there any other major goals or limitations that must be factored into the design?
First and foremost for me, its a form and aesthetic study. I want to make a speaker that sounds good, but that stands out from conventional speakers.
That is the main reason why my choice fell on the OB solution. I was also considering Magnepans, but they have alot of other limitations that i could not work around.

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.
I was told that the OB solution have better sound quality. I have never heard one of them in action, and in general not listened to may high-end systems.
Also as said above, the conventional speaker with a row of elements in a enclosure is the "stereotype" speaker and i want to differentiate from that.
 
As suggested in that thread this is kinda the feeling or aesthetic i want to aim for.

Ahh, ok - If you prefer to learn "the hard way" - its quite simple:

Buy this white material + some color to paint it to your taste, bore holes (roughly the size seen) and attach speakers that fit in there. You are done !

Then I suggest to come back - you possibly will need a looooot advice on how to do the XO, but at least your main goal - aesthetics - you've already reached.
Of course you will be asked about your measurements skills - or improve on those if necessary.

But it can be done - certainly...

For an "unconventional" way to find XO alignment you also might read form LAMPIZATOR as much as you can:

P24_monster_speakers_raal_altec_lansing

Remember: with OB its even more so than with speakers in general

EVERYTING GOES


Michael
 
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It's possible

I would have to say the a high WAF is possible with OB. Actually, I think it's possible with almost any design. The key is the finished product. Does it look like something you built on your back patio, or does it look both eloquent and practical- like a piece of art that serves a function?

If you build something that is pretty to look at, as well as pretty to listen to, then I would give you better than half on the odds. But that's just been my experience.
 

Flaesh

Member
2009-12-21 4:57 pm
Eburg
Zepticon, what is the design in your understanding?
Form follows function? (good sedan should have a long hood)

Or marketing ideals - to sell garbage to the consumer, such as a mixture of hydrogenated fats, modified starch, emulsifiers and colouring agent as good food or needle-style speakers as hi-end? :)
 

Zepticon

Member
2010-11-27 11:36 am
Zepticon, what is the design in your understanding?
Form follows function? (good sedan should have a long hood)

Or marketing ideals - to sell garbage to the consumer, such as a mixture of hydrogenated fats, modified starch, emulsifiers and colouring agent as good food or needle-style speakers as hi-end? :)
Form should follow function, and the aesthetic is a result of a functional product. Im kinda the hybrid between the engineer and the artist. And get the best from both world, atleast thats what the teachers tells us:D

The white one i linked is very much what i woudl value in a product. Its simple. Its a result of its function, and its not styled more than what is to be expected. I also like the sublte but yet very powerfull style that Apple use (think its from very early Braun philosphy).

Also, happy customers is returning customers:D I personaly prefer dealers that offer good service at a more expensive price over cheap products but no service.