TL or sealed...

[Chris8sirhC]

Recently my first DIY full range project took a drastic turn when i discovered that I had inadvertently destroyed half of the drivers i bought. (I decided to grind off the 1/4'' tabs sticking out of the front of some cheap parts express 2'' drives so i could rear mount them. Well, when you grind metal down on a grinding wheel, lots of metal filings are created.....and they like to go into the insides of the drivers.... ) ANYWAY
Now instead of having two line arrays that are each 7ft tall, with corresponding arrays of 10'' subs, i am down to 16 2'' drives per side. None of the 10'' drivers where damaged bc they didnt need to have pieces ground down.
My current design is to have the 16 2'' drives positioned in the center (vertical line array) with two 10'' drives on the top and 2 10'' drives on the bottom (listening position will be about half way in between the top two and bottom two 10'' drivers so i dont think this will be too much of a problem. Since these speakers will end up being about 7ft tall, I was thinking it mighnt be a good idea to make the 10'' drives into a dual transmission line type of design. Would this even be possible, and is it a good idea. The other option is just to make them all into sealed enclosures. I'm really a novice, so im not quite sure. Any thoughts, comments, suggestions? Negative ones are welcome too.

the woofers I'm refering to are thesehttp://www.partsexpress.com/pe/pshow...number=299-721 and since the enclosure for the 2'' array is only about 2.5'' deep, I was planning on making a large narrow C shape for the subs with the 2'' array being in the gap a squared, narrow C would make (side view)

btw i am planning on bi-amping with an active XO

[planet10]

The Qt on these drivers is fairly high... i'd say you want to look at a TL or an aperiodic enclosure if the TL is too big...

You should also consider mounting the 10s push-push.

dave

[Chris8sirhC]

here is something I drew up. Its not to scale, and i havent figured out how im going to have it tapered (should I) yet. But here is the basic premise im thinking about constructing.
full range tl preliminary design Do you think something like this would work well?

[planet10]

That will work... you will want to model it ... and i'd put one pr of 10s on the front, and 1 pr on the back....

dave

[Chris8sirhC]

did you mean like this TL or keep them split with two on the top of the speaker and two on the bottom (bottom = one facing front, one firing backwards out the back) and the same would go for the top. ?

[planet10]

like this....

[Chris8sirhC]

I recently came across this

A variation I almost didn't try was mounting one of the woofers backwards (with the magnet facing out) and then wire the drivers out of phase. The theory is that woofer cone movement is not perfectly linear. In response to a symetrical sine wave the outward motion of the cone does not match the inward movement. By mounting the drivers face to back and wiring out of phase the non-linearities cancel out. I figured that with a high quality driver and limited excursion that the cancelation effects would not be audible. Boy was I ever wrong! The bass was notably cleaner and controlled with lots of slam. Subjectively there seemed to be a little less bass which is a clear indication of less distortion. After hearing the difference I would never consider any other topology than out-of-phase push-pull. It is more than a little odd looking but it fits with my non-conventional theme.

on this site I was wondering if anybody else had an opinion about this topology as opposed to the two drivers facing oposite directions. Another thing ive read is this

I have seen this done and measured one speaker system that used a device like that, it did not work very well. At high volumes the driver moved enough to loose contact with the bar and a rattle resulted. It could be seen in the measurements and clearly heard. It is very hard to get enough pre-compression of the bar to keep everything in contact during operation.

from a very knowledgable person. I was also wondering if anybody else had any different opinions on this matter. I'm still tossing around ideas and nothing is set in stone yet.

[planet10]

A push-pull situation -- particularily if some attempt is made to couple the drivers -- gives much of the benefit of push-push, tends to average out any non-linearities vis-s-vis the driver moving in vrs out, but also tends to be noisier.

The 2nd comment i'm guessing is about the coupling structure between the drivers... if this is just a dowel wedged inbetween the drivers then i could see that it might come loose on a high excursion sub since it is truly only effective during compression (in an extreme case the connector would just fall out). There are a number of ways of minimizing this, the most thorough scheme is shown in the attached picture.

dave



A larger picture can be seen from this page.

dave

[Svante]

Mounting one woofer backwards should be smart. At least as long as the wavelength is much larger than the magnet. The web page is right in that some of the distortion will cancel, however odd harmonics (3rd, 5th, 7th etc) will not cancel, but remain the same. Still an improvement, since the second partial is often strong.
Audio Pro's early subwoofers more or less *required* such a mounting, the active design was very sensitive to a non-linear voice coil inductance. This was taken care of by having two drivers in push-pull.
The only downside of the arrangement is some effects towards higher frequencies (1kHz+) and the looks of it.
The isobarik mounting has the same distortion canceling benefits.

[planet10]

Originally posted by Svante
The isobarik mounting has the same distortion canceling benefits.

Which leads to the idea of the push-pull-push-push isobaric design

dave