[Audiovista]

Ok guys, what are the implications of building an OB speakers to be used outside? Please educate me! 

My wish list (in no particular order) is as follows - please feel free to cross any stupid, impossible requirements... I know nothing practical about the boxless speakers:

1. Simple - single driver with maybe a supertweeter (but if the single driver goes to 15kHz, I'm happy)

2. Suitable for low listening levels (I live in a highly urban, densely populated area, my neighbors may not share my taste in music). I would still like to hear some bass (see #6)... Listening distance is, say, 5-10ft.

3. High efficiency is a plus, but not necessary (not critical for low volume listening).

4. Amplifier requirements (required damping) not critical, I have decent tube (SE and PP) and SS (Class A, AB and D) amps available.

5. Weatherproofing is not a concern - they would be moved in and out of listening position, as required. If there are simple ways to protect them from rain, I will not complain.

6. Because of #5, small size (relatively speaking) is advantage - does baffle get to be smaller outside where there are no reflections off the walls? Bass that goes down to 40Hz would be perfect, but 50Hz is also ok (even 55-60Hz if that helps a lot).

7. Low cost - not even sure what that means in the OB world 

I probably missed something important here, please add as needed....

Many thanks!

Boris

[Rudolf]

What OBs do best is to overcome the shortcomings of boxed drivers in rooms. As are:
-excitation of more room modes
-room gain leading to boominess
-wide dispersion pattern resulting in prominent early side wall reflections

IMHO the advantages of OBs (compared to "boxes") are reduced in the open field. Demanding 55-60Hz in OB from a FR driver would make that OB quite big and certainly much less transport-friendly than a closed or vented box.

Rudolf

[gainphile2]

Walking around an OB speakers outdoor is really amusing. You can really hear the bass dissapear from the sides.

[Audiovista]

Looks like I'm in trouble.... started with Rudolf's website and run out of my German pretty quick. Moved onto Gainphile2's and followed links to forums, couple of hours went by just like that.... great sites guys! 

Ok, so my ambitions need to be reduced.... 50-60Hz doesn't seem reasonable... I have a small old sub that should cover me down to 40-50Hz. So the OOB (Outdoor OB  ) can start at higher frequency, say 150, maybe even 200Hz.

Considering what Rudolf said:

"...What OBs do best is to overcome the shortcomings of boxed drivers in rooms. As are:
-excitation of more room modes
-room gain leading to boominess
-wide dispersion pattern resulting in prominent early side wall reflections..."

Does it even make sense to go with OB? But please consider that I would really, really, really, REALLY like to try it...

And if not total nonsense, are design methods different for outdoor application.

Oh, did I mention that I would really like to try OB speakers?  aa

[gainphile2]

Well in that case have a read at this guy:

http://www.mfk-projects.com/dipole_pa_system.htm

Especially the woofer part. 

[Rudolf]

Boris,

I did not want to discourage you from trying OB outdoors at all - just cut your expections to the reasonable and feasable. Looks like I did succeed.
Design methods would be the same outdoor as they are indoor IMHO. May be you could let the dipole null to the sides (as mentioned by gainphile) work to the advantage of your neighbours. This aspect makes dipoles attractive even for professional outdoor PA systems.

[scorpion]

Boris,

JohninCR, once famous in this Circle, advocated that we should bring our OBs outdoor, They would sound even better there he said.
I have never tried and it is still very early spring over here.

Can we assume you will play the speakers on a balcony or perhaps roof in NY with one of your beautiful tube apmlifiers.
Then you will have some floor support for bass. But 50 Hz is tricky if you don't want to employ some EQ. I would recommend going with the popular Eminence Alpha15 for bass unit. They should deliver also on a 40-50 cm wide baffle. Have a look at Martin J King's groundbreaking paper: http://www.quarter-wave.com/OBs/OB_Design.pdf .

You could try some of the Fostex units or some other high efficiency unit of your choice for the upper part. To get a pretty ready solution why not try Hawthorne Silver Iris on 60 x 50 cm baffles. By angling the baffle you should be able to cut size a bit and still get the sound where you would like it. I am certain you can work it all out and please let us know of the result. 

/Erling

[Audiovista]

Now we're talking!!! 

Gents, many thanks once again for pointing me in the right direction. 

Gainphile - this is one mean looking woofer! I wonder if my deck is strong enough to carry it 

Yes gainphile said, but I did not process it the right way, thanks Rudolf for emphasizing it - speaker orientation that does not bother neighbors would work perfect for me, considering they are to the left and right of my would be listening position.

Erling, I would love to try Fostex speakers in that role... that would also provide a backup plan in case something goes wrong - they can always end up in a horn. I would use them on a deck behind the house and my preference would be one of my tube amps, but there are other options should they prove to be more suitable (   )

Obviously there is a lot more reading to be done, but I would not hesitate building something simple and proven, should you guys know of such design... I am hopeful that you guys tried or wanted to try something simple before moving to more complex designs (everyone was a beginner at some point...).

Thanks again,
Boris