Good Idea, Bad Idea?

[BKr0n]

Two woofers with PR in separate and seperated enclosure in the basement and mid/high seperated on top.

What about a sandwich? One woofer and PR pair on the bottom, mid chamber, and woofer/PR pair on top? Would probably have better imaging. Funnily enough, I think that's actually sort of the concept that KEF goes with for a couple of their high end speakers. The difference being they use 4 bass drivers as opposed to 2 and 4 PR

 

[BKr0n]

Amplification and Xover would be then the next challenge.

That one I actually have a little better handle on. Already have a design for the subs. Just need to assemble and prototype. The mid and tweeter will be a little more interesting...

 

[voodooless]

Already have a design for the subs.

If you use subs, it may be much more efficient to have the bookshelf’s just play until 50 to 80 Hz. You’ll also have more choice in woofers.

Also note that like KEF does, you could mount two or four woofers on the sides. You’ll have more surface area for a bigger woofers and more choice.

And with subs, a closed box may also be good enough.

 

[BKr0n]

If you use subs, it may be much more efficient to have the bookshelf’s just play until 50 to 80 Hz. You’ll also have more choice in woofers.

Also note that like KEF does, you could mount two or four woofers on the sides. You’ll have more surface area for a bigger woofers and more choice.

And with subs, a closed box may also be good enough.

4 woofers in bookshelves? that's madness!!!... I like madness that actually may not be a bad idea. They are definitely going to be some chunky bookshelves that's for sure. I guess since they're going to go on stands that won't matter too much. The only thing to account for there would be the mass of the stand and a way to control reverberation through it. Additionally, I also then need to figure out if there will be any drawbacks to keeping them all in the same chamber. I would probably also need to use a nice dense material for the enclosure. (also I think a regular sub will upset the neighbors)

 

[Salt]

"What about a sandwich?"
The woofer has Xmax of 11.4 mm, and if You will (and You will) use it to this max it will shake mid/tweet and compromise settlement, if the top is not fixed.
Imaging/soundstage/whatsoever lies not in the position of the woofer to be as close to mid/high in ranges of some inches.
Going the KEF way it would work with floorstands, centering the enclosure for mid/high and draping woofer and PR around.
You don't need subs additionally (as quoted by voodooless) if construction in itself fullfills Your needs in respect of small to medium environment.

 

[voodooless]

a way to control reverberation through it.

Two on each side, they would cancel The KEF unit should get it’s own compartment, but it can be small.

 

[Salt]

Two on each side, they would cancel The KEF unit should get it’s one compartment, but it can be small.

Agree

 

[BKr0n]

Ok then 4 subs it is. I guess next question would be how to set up the electronics. Inside or in a separate chamber altogether? Probably the trickiest part will be to set it up in such a way there will be no delay. In the amplifier circuit I have in mind for the subs, the signal goes all the way through a feedback loop. Would probably need to put it closer to the speakers themselves to mitigate delay, but that would also vibrate the shit out of the board...

 

[Salt]

Plate amp by hypex, dayton ... with dsp onboard.

 

[voodooless]

Ok then 4 subs it is

It’s just a suggestion There are plenty of other schemes possible. I would definitely not use the Dayton drivers when using 4 woofers. There are cheaper options out there with decent performance and better efficiency.

As for the feedback loop: the signal is almost speed of light, distance is irrelevant.

 

[BKr0n]

Plate amp by hypex, dayton ... with dsp onboard.

I've been told this whole time to steer clear of DSP... then again, with what I had in mind, that may be for the best.

I would definitely not use the Dayton drivers when using 4 woofers. There are cheaper options out there with decent performance and better efficiency.

They're not my first choice either. But when it comes to size and price to performance, they're just about it. If i had all the money in the world, this would be a very different project.

As for the feedback loop: the signal is almost speed of light, distance is irrelevant.

Well then there's no problem lol

 

[voodooless]

But when it comes to size and price to performance, they're just about it

But only if you really need the low end extension. With 4 drivers you can easily halve the Xmax and opt for more efficiency.

 

[BKr0n]

But only if you really need the low end extension.

I mean... I would like the low end extension if possible.

With 4 drivers you can easily halve the Xmax and opt for more efficiency.

Yes I agree. I was just contemplating that a bit. So if I wanted 40 watts from the main driver, that would mean 320 watts from the subs. But that's at 4 ohms. Since each sub has 2 coils per, there's a lot of ways I could wire that. Additionally, since it's further spread amongst 4 woofers, that will definitely lower the xmax.

 

[BKr0n]

Here's a neat question... Can vituixcad simulate this? If so, and the numbers look good, I may just stick with analog. Also, any considerations for the enclosure? Also, since they're going back to back, should I adhere them to each other so they don't clack together inside?

 

[voodooless]

I may just stick with analog.

You’ll still have an efficiency issue. And in a closed system, you’ll need to EQ the bass.

 

[Salt]

Are You aware of the dimensions of the woofer? One of them needs 10 cm and two 20 cm inside the cabinet, so front of the speaker would be at least 24 cm wide.

 

[BKr0n]

You’ll still have an efficiency issue. And in a closed system, you’ll need to EQ the bass.

Hence why I was asking if I could make this in vituixcad lol. As far as efficiency, I don't think I'll be able to match the kef perfectly, but with 4 subwoofers I would like to think I can get close.

Are You aware of the dimensions of the woofer? One of them needs 10 cm and two 20 cm inside the cabinet, so front of the speaker would be at least 24 cm wide.

If it's going on a stand then that's OK. Stand is a little easier of an engineering problem than the speaker imo

 

[BKr0n]

@voodooless you reminded me of a post I saw a while ago. Would like to hear your thoughts on it. It talks about Hoffmann's iron law https://www.diyaudio.com/community/threads/subwoofer-efficiency-is-mostly-irrelevant.358153/

 

[voodooless]

Reads the topic carefully. There are many caveats there, most notably box size.

In the end, displacement tells you how loud you can go. Next your need to be able to put enough power to reach that displacement. The size of the box is crucial here. The smaller the box, the more power you need.

 

[BKr0n]

From the looks of it, the products that use this method are floor standing units. Additionally, the center cavity, the space between each set of woofers, would be to what scale. I'm not sure I would want floor standing units, but I won't dismiss it as an option. As far as power, I'm using the TPA3255 chip for the sub amplifier. It's just a question at that point of how much and how many.