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Not me !!!! Ha... just kidding.

I've went and got myself all excited about my latest build... Two Dayton Audio 15"s mounted isobarically, and tuned with a 15" passive radiator. And the thing is, based on what turned out to be a test build, I'm super confident that it is going to be the shiz ☺ And the enclosure is going to be so freaking tiny... only a 16x16x16 cube.

So....... as is often the case, when I get myself on a roll, I got to thinking..... what if I did the same thing with two 18"s.... stronger, with more wattage of course ☺ This is what I came up with;
In fact, just so you know I'm not just throwing stuff out there, that will never happen, I already ordered one of these last night, to kind of lock myself in 😉
Going to order another one soon...... but I might go on and order the new mono amp first.... because I could hook it up to my two Dayton's now, which will only produce 2 ohms, and so "only" 1500 wts (they are rated for 800 wts rms each, but only getting 480 each right now) But with my next big build, with the two 18"s, the amp will only see 1 ohm, and put out 2500 rms.... 1250 for each sub, which is exactly what they are rated for.... Here's the amp

And then the only thing left to buy.... either two more 15" PR's (if I steal the one out of my current build) or, a pair of Dayton 18" PR's. Only thing that's kind of a bummer, is that neither two of the 15" PR's, or one of the 18" PR's are quite enough...... as I read that your PR's should have at least twice the Volume displacement (Vd) of your sub(s) ....and both options, two 15"s or one 18" PR, are like 180-190%.... figures. But it will look more impressive with more PR's anyway, and it won't take any more space. My cubes going to have 4 available sides anyway, right ? And again, for two 18" with 2 or 3 PR's, the cube enclosure is going to be very small, only 19x19x19, with 2.25 net cubes.

Anyway, going from the current isobaric 15" build, to the new 18" isobaric build I'm describing here, I will be increasing my speaker Vd by about 275%..... and also, going from my current amp, to my new amp, i'll be increasing my wattage by about 275% as well ☺ Should be a little louder, right ? But hey, I already know going into this, there are ways to get a LOT more SPL's for the same amount of hardware / $$$ spent. But for my purposes, I think these 18"s are going to be "substantially loud" and I'm hoping they are just super tight, snappy, and musical ☺
Whoo hoo ☺ Hoping it's kind of rediculous !
Super anxious. My better time of the year for $$$ starts in about April.... So hoping to have this done by early Summer. You guys will probably get tired of hearing about it by the time I'm finished.
 

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Wow - this is an interesting idea Chris. I would say that these rules of thumb are just that. If you are at 180% of your driver displacement, you are probably fine unless you're going with a very big box. Every build has a bottleneck and I would rather that be my PR than my drivers.
 

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Discussion Starter #9
Wow - this is an interesting idea Chris. I would say that these rules of thumb are just that. If you are at 180% of your driver displacement, you are probably fine unless you're going with a very big box. Every build has a bottleneck and I would rather that be my PR than my drivers.
I hear you. I guess maybe if I were to model the my next setup, and it showed the excursion of the PR(s) to be within the limits of excursion, then I might go with only one 18" PR, or two 15"s....
The obvious advantage would be the cost.
 

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I love them for sound quality in a car. Not so much in the house. Infinite baffle in a home. If you can pull i off in a car like this one dude did by sawing off a part of his trunk... :)

Love to see photos of the build.
 

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Discussion Starter #11
I love them for sound quality in a car. Not so much in the house. Infinite baffle in a home. If you can pull i off in a car like this one dude did by sawing off a part of his trunk... :)

Love to see photos of the build.
I'll post pics for sure. I know it's going to look crazy.... Like, "That box is way too small ! That will never work" 🙂 lol

But when you stop and think about how it's all happening, it seems very logical.... If you have twice the force on a speaker area, pushing back and forth, you need twice the compliance (half the space) to hold it in place.
 

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Vance Dickinson talked about this a while ago in his Home Audio Cookbook. So far he explained it best for anyone to understand.

Generally speaking, an isobaric subwoofer arrangement in a Horn loaded box would be the ultimate Cheap and cheerful sub box. You get massive output, and great driver control with the isobaric configuration. And you get just about the highest quality bass you can think off. Similar to the old 1952 Jensen Imperial speakers but with a Horn loaded front. Or some of the JBL speakers I have seen that are Massively popular in Japan.

I just don't think they would sound that good in the car, but outside the car? It would be loud as all hell. :)
 

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Discussion Starter #13
Vance Dickinson talked about this a while ago in his Home Audio Cookbook. So far he explained it best for anyone to understand.

Generally speaking, an isobaric subwoofer arrangement in a Horn loaded box would be the ultimate Cheap and cheerful sub box. You get massive output, and great driver control with the isobaric configuration. And you get just about the highest quality bass you can think off. Similar to the old 1952 Jensen Imperial speakers but with a Horn loaded front. Or some of the JBL speakers I have seen that are Massively popular in Japan.

I just don't think they would sound that good in the car, but outside the car? It would be loud as all hell. :)
But your saying, "He talked about Isobaric setups" right ? ....But Horn loaded, not tuned and ported, as I have already done, or, tuned with a PR, which BTW, mine is supposed to arrive today...

Now, while not exactly a loaded horn, I have actually already designed on paper, a T-line enclosure for my two 15"s set up Isobarically, which would make the pipe reasonable in size...not tiny, but doable. To do two 15"s which were not mounted Isobarically, in a T-line, would be ridiculously huge, and not doable in anything but a moving van... Or a walled, full sized SUV.
 
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