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Multi-Way Conventional loudspeakers with crossovers

isobaric bookshelf?
isobaric bookshelf?
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Old 14th March 2018, 02:33 AM   #1
3wayaddict is offline 3wayaddict  Netherlands
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Default isobaric bookshelf?

Hello,

When I was sorting out the electrical part of the powered speakers and subwoofer I'm going to build I turned out to not need a couple of components I was first planning to use, this saved me quite some money. You would think: "well, nice little safe." but I would save so much money I kinda felt bad to not improve the speakers even further. So I just put together a few alternative designs together like making towers with two woofers in stead of bookshelfs with just one but none of them would be a good choice because I actually don't really want towers for my listening room and I want to use PRs but the towers would take so much PRs it would be just a little over the budget.

So I want to stay with my bookshelfs but I still want to do something to make them better. I know about the isobaric principle and adding another woofer and then putting both woofers in parallel would still fit in the capabilities of the amp, so I would love to make the bookshelfs isobaric.

So the isobaric should be good at reducing distortion and make the woofers move and so sound even quicker and better in control because of the doubled motor.
But I read about a couple of parameters changing.
In parallel the sensitivity of both woofers combined and the max output in db stays the same right? But the vas changes, and a couple of other things.

So the main question is: Can I use isobaric woofers in the same, previously not isobaric, enclosure design. So the same volume, tuning of the PRs etc. Only one of the woofers is radiating in the enclosure so should be right?
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Old 14th March 2018, 02:41 AM   #2
scottjoplin is offline scottjoplin  Wales
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Isobaric arrangement requires half the volume of a single driver, that's about it, very minimal reduction in distortion, in fact if you use the two drivers normally the distortion will be less due to less excursion
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Old 14th March 2018, 03:05 AM   #3
IG81 is offline IG81  Canada
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First thing, if you already have the enclosures built, then it would at best make it look like 2x the volume, but less so in reality, because you'll be eating a good deal of that volume with the coupling arrangement. Second, would this apparent increase in Vb be beneficial to the woofer and alignment in question? It was (most likely) not taken into account in the original design after all and would be a significant enough deviation IMO.

As far as sensitivity goes, parallel woofers will be the same as a single, but efficiency will be down 6dB, just make sure you have the amplifier power for it.

You'd also want to make sure to install the interior driver as close as you can to the exterior one and low-pass it at a frequency lower than a quarter-wavelength of the cone-to-cone distance.

All in all, I'd say it's not worth it as an afterthought and, even when planned ahead, all it really does is to essentially halve a single driver's Vas and thus resulting Vb.
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Old 14th March 2018, 03:11 AM   #4
adason is offline adason  United States
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Quote:
Originally Posted by scottjoplin View Post
Isobaric arrangement requires half the volume of a single driver, that's about it, very minimal reduction in distortion, in fact if you use the two drivers normally the distortion will be less due to less excursion
There is another mode of distortion reduction by using clam arangement, when one driver eliminates some distortion of the other.
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Old 14th March 2018, 03:33 AM   #5
adason is offline adason  United States
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This is one amazing sounding bookshelf, but those hating isobaric will never have a chance to hear it.
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Old 14th March 2018, 03:34 AM   #6
adason is offline adason  United States
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Not to mention simpler crossover...guess why?
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Old 14th March 2018, 03:46 AM   #7
IG81 is offline IG81  Canada
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While the motor-side sticking out certainly would not fly in a commercial offering, I guess you do get a "+1 order" bonus to your Xo. Is that midrange a Philips?
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Old 14th March 2018, 04:33 AM   #8
planet10 is offline planet10  Canada
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isobaric bookshelf?
Where are you XOing? At a frequency related to the half-wave of the distance from the inside of the baffle to the front odf th erear baffle you start getting significant ripple. You would want to XO wellbelow that… usually not possible with the typical cone + dome speaker.

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Old 14th March 2018, 08:02 AM   #9
3wayaddict is offline 3wayaddict  Netherlands
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I’ll give some more details,
I’m using the Dayton Audio ES180Ti-8 woofer, NOT TiA, Ti! And a Fountek NeoX1.0 ribbon tweeter. The amplifier I’m gonna be using is the Hifimediy T3S with Jantzen caps which has more than enough power to drive the woofers, 2x150 watts RMS @ 8 ohm, 2x300 watts RMS @ 4 ohm. And as far as the flexibility of the crossover goes I’m not limited because I’m gonna be bi amping via a MiniDSP 2x4 HD.

The enclosure haven’t been build yet, what I mean with the same design is pretty much keeping the current design but just with a second baffle on the inside.

But as I understand. If I first were to make the Vb 20 L I would now only need 10 L?
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Old 14th March 2018, 10:17 AM   #10
Old'n'Cranky is offline Old'n'Cranky  Australia
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Given up on your previous builds huh

Aluminum enclosure for 2-way bookshelf?
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