[rajacat]

How about laminating sheets of signboard (aluminium sheets, sandwiching a polyethylene core) together to form a composite baffle? IIRC Vapor Audio experimented with composite sheets,they didn't call it signboard though , on some of their baffles. This material would form a very stiff baffle using the mollifying influence of combining different materials. It could be used as a stiffener sandwiching other materials such as plywood and MDF.

[JCS]

I just used good quality 3/4" plywood & braced it very well.  I think many complaints about Eminence Alpha 15a sounding muddy stem from Wobbly Baffle Syndrome.

Cheers, Jim

[skite30]

Those look great.  Can u tell me dimensions and degree of tilt?   What drivers r they made for?  I am using the modified 15a's by pure audio project.  A much different driver than the standard 15a.

[Poultrygeist]

One thing I've learned with OB's is if you don't listen at loud volumes exotic baffles and elaborate bracing aren't necessary.

I primary listen to acoustic jazz at low volumes so 3/4" MDF or plywood works fine for my needs.

If the volume is not loud enough to excite the baffles you won't hear them.

[mcgsxr]

Agree that spl drives the need for bracing.

I used 3/4 mdf for 10 years after knocking out a set of baffles.  I thought I would later redo them with more mass etc, but at my 85-90dB levels it was never an issue.

[JCS]

Hi Skite30,

The baffle is 38.25” tall by 22” wide at the bottom and 14” wide at the top; and there is a 45 degree bevel on the edges.  Tilt back is 5 degrees.  I used Fostex FF85k and Eminence Alpha 15a drivers.  The FF85k has been superseded by the FF85wk, which is reported to be even better, however, the sensitivity is different and might require tweeking of the XO--or perhaps a different driver altogether.  The concept comes from Martin King’s work; see:
http://www.quarter-wave.com/OBs/OB_Theory.html

For more on my build, see these threads on DIYaudio.com:

starting at post #479 in this thread:  http://www.diyaudio.com/forums/full-range/108751-new-mjk-baffle-article-48.html

For MJK’s review after hearing these OB’s:
http://www.diyaudio.com/forums/full-range/155019-jim-shearers-fostex-ff85k-eminence-alpha-15a-open-baffle-speaker.html

Cheers, Jim

[skite30]

Thanks. Several good ideas for me.  My listening levels r pretty low. Rarely exceed 80 db and often times stay in the 65-75 range.   Really liking the tang band so far about 40 hours.  Some real ups and downs with it though. Perhaps more than any other driver I have ever had.

[Wind Chaser]

Really liking the tang band so far about 40 hours.  Some real ups and downs with it though. Perhaps more than any other driver I have ever had.

Could you expand on that, please?

[skite30]

So far they sound wonderful one day and harsh the next. They r in a far from ideal set up, room, electronis etc but still set up the same every day so should be able to compare from day to day.  There is much work to be done with all those things but just giving my initial impressions.

[Wind Chaser]

I wonder how many hours are required before they stabilize?

[PDR]

The big change will come when the cross over is added and the Neo 15s can play up to the prescribed 450 Hz.

 

[Wind Chaser]

Are you suggesting that crossing them over at 450 Hz will help them stabilize / break in?

[PDR]

Are you suggesting that crossing them over at 450 Hz will help them stabilize / break in?

Dont think thats what I said...


When my TB 1808 was set on a board and I was using the Super Vs servo
subs it was underwhelming. I had them set up like this for a month or so.
Were they breaking in? ......maybe. I played various music thru them.
Some music seemed more pleasant  than others.
The Neo 15" play higher than the servos, but dont have the impact on the low end
like the servos.....I cant think of any OB design that does.

I'll have the servos integrated in my room in a few weeks, I'm renovating them...

I'm putting together the x-over for skite, should get it in a few weeks.
That should give him plenty of time to break them in.

We'll see what he thinks of them then.....I dont think they'll disapoint.

[Wind Chaser]

Interesting. Even without reaching up to 450 Hz, I would think the servos would be superior in every respect to the Neo 15s. Looking at the FR, they seem reasonably flat (+/- 3db) between 100 - 10K.

In any case, wouldn't it be better to run the bass drivers with plate amps?

[PDR]

Even without reaching up to 450 Hz, I would think the servos would be superior in every respect to the Neo 15s....

In any case, wouldn't it be better to run the bass drivers with plate amps?

Exactly what I was thinking.....then I plopped the passive x-over in......and now I think different.

This whole PAP thing was just an experiment for me......never thought they'd be staying.

[Wind Chaser]

Exactly what I was thinking.....then I plopped the passive x-over in......and now I think different.

Oh boy, I'm just trying to figure where I'm going with all this. Color me confused.

I was thinking of building something like this... http://www.audiocircle.com/index.php?topic=96082.msg988575#msg988575

I'm not that savvy when it comes to DIY, but it sure seems a lot more cost effective than buying a finished product from Emerald Physics, Pure Audio, Spatial or Tekton. Outside of those 4, I'm not aware of any other commercial options.

The crossovers you are building for Skite, are they designed to work with one or two Neos? The reason I ask is I was thinking of just going with one to keep the size down to coincide with my smaller room.

[PDR]

Your correct, something I didnt think about, the Neo will only be at half out put......I'll have to let him know.

Thanks.

[Wind Chaser]

Hi Perry,

A few questions if you don't mind... 

I'm guessing the 1808 doesn't operate full range with the crossover, otherwise you'd just use an inductor, right?

Is that a first order crossover?

What are you using to power your PAP?

Finally, how do these compare to your other OBs?

Thx - John.

[PDR]

Hi Perry,

A few questions if you don't mind... 

I'm guessing the 1808 doesn't operate full range with the crossover, otherwise you'd just use an inductor, right?

Is that a first order crossover?

What are you using to power your PAP?

Finally, how do these compare to your other OBs?

Thx - John.

John......I'll PM you