full range idea

[goraman]

Just been thinking of building an odd animal in the speaker world.
A mid size sealed speaker cabinet with a 8 inch full range driver and directly behind it in a push pull configuration a 10 or 12 inch passive radiator.

Cabinet would be 2.80 cubic ft. but will using a large passive radiator allow me to use a smaller cabinet?
Lets say 24 tall x 18 wide x14 D.

speakers up for consideration so far.

http://www.youtube.com/watch?v=IWDxf4Or5Vs http://www.parts-express.com/pe/showdetl.cfm?partnumber=295-346&utm_source=Bazaarvoiceps
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=293-680
Any body try this?
Any feed back would be greatly useful and appreciated.

Front and rear baffle of birch 3/4 plywood, sides 3/4 inch MDF with internal bracing.

[Patrick Nash]

Would this be similar to the Lecontoure speakers?

http://www.soundscapehifi.com/images/lecontoure-mobile-160.jpg

Amazing bass for a small standmount - Midland Audio Exchange sell them.

[John]

Jeff why not consider going Open Baffle and getting drivers to suit you get so much more more sound per pound and you could build them not to much bigger than the diamensions you mentioned width would be 19" you can do it even less and height would depend if you just have one or two drivers
If you interested in the idea I give you my diamensions but you can eaisly do them a lot smaller than mine

[goraman]

Jeff why not consider going Open Baffle and getting drivers to suit you get so much more more sound per pound and you could build them not to much bigger than the diamensions you mentioned width would be 19" you can do it even less and height would depend if you just have one or two drivers
If you interested in the idea I give you my diamensions but you can eaisly do them a lot smaller than mine

My only experience with open baffle was much like electrostatic panels, placement had to be at least 1 meter from the rear wall and a defuser between the wall and the speaker.

Or imaging gets weird, Open baffles also require a very low Q much like car speakers or back loaded horns if i'm not mistaken.

[goraman]

Would this be similar to the Lecontoure speakers?

http://www.soundscapehifi.com/images/lecontoure-mobile-160.jpg

Amazing bass for a small standmount - Midland Audio Exchange sell them.

Oddly small but I really need efficiency as well as bass in a slightly larger enclosure.
So basically I'm revisiting the imposable.

Those speakers are only 87.5 DB.

[Reid Malenfant]

Hi Jeff, you won't need a huge beast like that 12" passive radiator - take it from me ;) All you'll need is some kind of PR that can move 2-3 times as much swept volume as the driver can.

Calculate the driver area & then with it's Xmax the peak volume it can move & then look for something like a 10" PR. Also whatever you do make sure that the VAS of the PR is much bigger than the enclosure volume you plan to put it in.

The reason for having the much bigger VAS is so the enclosure volume controls things & not the mechanical parameters of the PR :)

If you like i can show you what happens & how the PR will mess things up big style if the VAS is smaller than the enclosure dimensions like the one you linked to. You simply won't be able to tune it fella :eek:

Look for something with a minimum VAS of 4 times the enclosure volume...

I'll have to take a look at the 8" driver specs as over 2ft^3 is pretty big :scratch:

E2A:- Took a look & i reckon you could do good stuff with that driver in the kind of enclosure you are thinking of. The QTS is lowish so fast response, place a PR on the back will give you some deep bass reinforcement & kind of boost it a bit as it'd be rolling off without it..

You just need a more suitable passive radiator ;)

[John]

Yes geoff you ned space behind thm for them to work sorry did not know you had this as a issue If you ewre interested in the open baffle route I would of suggsted other drivers

[Reid Malenfant]

Had a look at the PRs on that site Jeff. There is a Dayton 10" which would do the trick, but it's VAS is still not much more than the enclosure size you are planning on. However i reckon the 12" might be a good one (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-496) ;)

The thing is though is this, it has a pretty low resonance frequency so you may find that you simply won't be able to get the thing to resonate at a high enough frequency.

However if you use 2 of these 10" daytons in each enclosure i reckon you'll get the resonance frequency up above where you want it & can then add mass to tune it lower. Also using 2 of them the combined VAS will be much higher & the enclosure air volume will predominate much more, rather than the suspensions of the PRs. Two of these (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-494) is still way cheaper than one of those things you were originally linking to :eyebrows:

[goraman]

Had a look at the PRs on that site Jeff. There is a Dayton 10" which would do the trick, but it's VAS is still not much more than the enclosure size you are planning on. However i reckon the 12" might be a good one (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-496) ;)

The thing is though is this, it has a pretty low resonance frequency so you may find that you simply won't be able to get the thing to resonate at a high enough frequency.

However if you use 2 of these 10" daytons in each enclosure i reckon you'll get the resonance frequency up above where you want it & can then add mass to tune it lower. Also using 2 of them the combined VAS will be much higher & the enclosure air volume will predominate much more, rather than the suspensions of the PRs. Two of these (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-494) is still way cheaper than one of those things you were originally linking to :eyebrows:

Wow! I 'm now sure I have no idea what the hell I'm doing.
I think I have to learn alot more about speaker physics.

[Reid Malenfant]

Wow! I 'm now sure I have no idea what the hell I'm doing.
I think I have to learn alot more about speaker physics.
I guess it's a good job you know someone that's been designing them for 30 years then innit :lol:

I have no idea why damn near every one of those PRs has such a miniscule VAS :scratch: It just doesn't make sense at the end of the day :mental:

But i reckon with a bit of messing about you can get something close to what you want Jeff.

By the way, take a look about over your side of the pond & see what other 8", 10" or 12" PRs you can find & link me to them. There should be stuff with bigger VAS out there & this would be even better. Like i say, i can show you why if you like :)

[goraman]

Thanks Mark,
You have been doing this for 30 years! Wow!
I really don't get any of this but I will do some more looking.

[Reid Malenfant]

Yep, i was 13 or 14 when i designed & built my first pair of loadspeakers :eyebrows:

Some mod that has the capability might like to move this thread to the drawing board by the way ;)