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PostPosted: April 24th, 2017, 3:33 pm 
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I am thinking about building new bass cabinets for my Basszillas (to lower them a few inches for better seated listening position). Anyway, I am giving serious thought to using a slot loaded open baffle instead of putting a driver in a smaller coffin. I am looking for ideas for drivers and any experience anyone else might have. I want to keep them high efficiency so I can avoid biamping if possible.


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PostPosted: April 24th, 2017, 3:37 pm 
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Other than Pass's article (which I assume you've already seen), I don't really know much. I've got 4x Dayton Audio PA460-8 18" Pro Woofers which I was planning to try on a 2/side basis, but I haven't gotten past the planning stages. So many projects, so little time... :angry-banghead:

Roscoe


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PostPosted: April 24th, 2017, 3:46 pm 
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Another consideration, and one that ought to work well & minimize cost, is that there's nothing magical about the basszilla bass cabinet... Come up with a height that works to get the midrange at the height you want, and work from there to recalculate dimensions that give you the same internal volume. Assuming, of course, that you're not somehow displeased with the current bass performance. Getting the correct levels with another solution is going to be a challenge...

Roscoe


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PostPosted: April 24th, 2017, 5:40 pm 
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There is a lot of interesting information in this thread that might be useful.

http://www.diyaudio.com/forums/subwoofers/258433-light-air-slot-loaded-band-pass-sub.html

Obviously, his 5" speakers are low efficiency, but there are some posts about using larger speakers.

The foam would certainly be a quick way to build.

ray


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PostPosted: April 24th, 2017, 6:18 pm 
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Roscoe Primrose wrote:
Another consideration, and one that ought to work well & minimize cost, is that there's nothing magical about the basszilla bass cabinet... Come up with a height that works to get the midrange at the height you want, and work from there to recalculate dimensions that give you the same internal volume. Assuming, of course, that you're not somehow displeased with the current bass performance. Getting the correct levels with another solution is going to be a challenge...

Roscoe


I already figured out the cabinet redesign for the lower height. I just want to try an entire open baffle system. It would be less trouble to make a slot loaded bass bin than a complete enclosure.

Right now, I am looking into drivers. Either 6-8", 4-10" or 4-12". I think I would stand a better chance of ending up at 95dB/1W using 4-12" using 8 ohm series/parallel connected. I may even overshoot. Just have to find 8 drivers.

I could also do it with a pair of 15" per side, but the slot depth resonance may come into play at my crossover point (200 Hz).

David


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PostPosted: April 24th, 2017, 6:48 pm 
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David:

Be careful of using series connected dynamic drivers around resonance. You can get out of phase results which result in dips in the response i used a strobe to examine a number of "identical" Peerless 10" woofers and found that with the inevitable differences in parameters, some pairs would get out of sync at resonance when they were slightly different. When the phase of one driver was leading the other was lagging. One of the contestants at last summer's Midwest Audiofest had the same result in a speaker he built with series connected woofers. Series connecting coils on the same voice coil former is no problem as they are physically held together. Not so with separate drivers. Once out of the resonance range the problems go away.

Tom


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PostPosted: April 24th, 2017, 10:40 pm 
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Tom,

Good point, but will be hard to avoid unless I get 32 ohm drivers and parallel 4 of them. Either that or I get a pair of 16 ohm 15 inch (which are few and far between, and just use two drivers in parallel. Otherwise I am pretty much forced into series/parallel arrangement.

At this stage, I have to consider what I am doing is an experiment, so may mock it up with inexpensive drivers to see if it works.

David


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PostPosted: April 25th, 2017, 8:56 am 
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Or you could use a multi channel amplifier so you have extra channels, then run the bass separately.

Tom


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PostPosted: April 25th, 2017, 9:36 am 
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Well, I am wrapping around to the idea of a single driver slot loaded open baffle implementation, using a single 15" or 18" per speaker. There was a prototype system that Nelson Pass developed with a 15 inch Eminence Definimax-LF slot loaded at the base of a Lowther open baffle. This actually should work great with my Fostex/Aurum Cantus open baffle for an integrated system. With slot loading, you lower the F3 and raise the Qt for better open baffle extension, pickup a bit of directional gain, with the slot at the floor you maximize room gain. There are a couple of 18 inchers to consider, the Eminence KiloMax-Pro, and the Beyma SM-118n. I think this actually might be a bit more practical than dealing with multiple drivers. My intention is not to use this as a subwoofer, but to replace my current bass cabinet (which extends down to 40 hz) with an open baffle implementation. I will probably lower the current crossover point of 200 Hz down to 150 Hz (widening the Fostex baffle).

The attached pictures are the Nelson Pass implementation for inspiration (neat Lowther field coil driver!). My intent is to run it passively, which means I may have to extend the back of the OB frame further to increase the baffle width to get more extension. I am sure Mr. Pass uses one of his high impedance current amplifiers and a bit of equalization.

David


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PostPosted: April 25th, 2017, 10:24 am 
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Like I said, I've got 4 of the 18" Daytons (https://www.parts-express.com/dayton-au ... r--295-036), you're welcome to try a pair... Any more info on the design that goes with those pics anywhere?

Roscoe


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