Need help for my first Open Baffle project

[anilva]

Hi,

I am in the planning stages for a twin 12" Woofer open baffle speaker with a midrange and a ribbon tweeter.

Being first time to Open Baffle, what should be criteria for selecting a woofer for open baffle. Should it have high Q or what?

Usage is for listening to stereo with vinyl and digital as sources.

I have seen quite a few projects of open baffle, but could not figure out what the basis was for selecting a particular woofer.

Thanks.
Anil

[DougL]

A high Q is a useful feature in an OB woofer.
Low distortion is good.
Large xmax is useful.
High efficiency is always welcome.
Low Fs is welcome (conflicts with efficiency)
Low cost is always welcome.
Depending on xo frequency, cone breakup behavior.

I probably missed a few.

Doug

[anilva]

Originally Posted by DougL

A high Q is a useful feature in an OB woofer.
Low distortion is good.
Large xmax is useful.
High efficiency is always welcome.
Low Fs is welcome (conflicts with efficiency)
Low cost is always welcome.
Depending on xo frequency, cone breakup behavior.

I probably missed a few.

Doug

Thanks. How do I know low distortion from T/S parameters? Also is large xmax good for OB. Somewhere I remember having read that xmax should be low - may be I am confused with a spec for full range speaker.

Regards

[c2cthomas]

Originally Posted by anilva

Thanks. How do I know low distortion from T/S parameters? Also is large xmax good for OB. Somewhere I remember having read that xmax should be low - may be I am confused with a spec for full range speaker.

Regards

Nah- for OB bass ya gotta move lots of air - MORE XMAX is a good thing!!!

[jerome69]

Hi,

Take a look on this website, you have some OB projects and a lot discussions around this.
Make a OB baffle is very difficult for a beginner but it could be very instructive.
It's easier to make an active OB than a passive one.
You do not have a lot of choice of woofer for OB. With a ribbon forget active crossover.

Have fun

[picowallspeaker]

Originally Posted by jerome69

With a ribbon forget active crossover.

Why ? Just add a safety cap 50-100 uF !?!? No good ?!

[bearberry]

To learn more:
http://www.quarter-wave.com/OBs/OB_Design.pdf
Music and Design
Issues in speaker design - 2 (and other sections on the same site)

If you are just starting out getting through some of this may be painful and require looking up additional references to understand terminology and concepts. It will gradually start to make sense.
If you just want to build an open baffle (OB) speaker NOW then the quarter-wave.com project by Martin King, and offshoots (especially Jim Shearer's Fostex ff85k and Eminence Alpha design) are probably a good starting point.

[DougL]

Originally Posted by anilva

Thanks. How do I know low distortion from T/S parameters? Also is large xmax good for OB. Somewhere I remember having read that xmax should be low - may be I am confused with a spec for full range speaker.

Regards

The only way to know about distortion is to test it.
As someone else mentioned, the more air that you can move, the better.
However, OB is all about compromise. More xmax usually means more distortion or a more expensive motor. Less xmax means lower max SPL and may require more drivers.
I also agree that active is much easier than passive.

If you let us know what you are planning, we could be more specific.

Doug

[anilva]

Thanks for the replies.

My plan is to:

- Have a twin 12" woofers in a open baffle.
- Optionally have a midrange to bridge the gap between the tweeter and the woofer.
- Use a hornloaded tweeter or a ribbon tweeter probably with "L' pads to adjust senstivity.
- Use a simple passive network.

I have made a number of closed and ported speaker systems before, but this is the first open baffle attempt. The reason I am doing this because, I believe open baffle systems have more efficiency and also probably easier to construct.

Cheers.