Need drivers for some dual 18 cabinets

[droberts]

I already have six dual 15 " cabinets any of which I could translate into bass cabinets , as far as the drivers are concerned . I'm really just trying to fill these dual 18 cabinets at the moment , and then getting some JBL SRX 728 s

[Cal Weldon]

Originally Posted by mulletdude

OK well the reason i have hear the 15's being tighter is the lower overall moving mass of the cone. it would take less power to give the same bass and the cone would move faster (more desireable in DJing) Also Cal ive been thinking of posting up my DJ rig on here, its all bought stuff nothing DIY'ed yet. where would you reccomend i post it?

Right here:

System Pictures & Description

It would take less power to achieve the same SPL with the 18"s all things being equal.

No the cone does not move faster. That's a misnomer.

Originally Posted by droberts

looks like I need an asbestos recognition refreshers course ... Is that the final word ?

Can't see that being asbestos. No reason to have used it in a speaker cabinet. That looks like common felt used in a number of things including upholstery

[Andrew Eckhardt]

Cal's got it. That's felt and fiberglass.

18's are great for what 18's do. You can get about half as many to do what 15s will do, 3/4 at a minimum. If you already have a cabinet with 18" holes in it, you should probably shop for some 18's


What is the cabinet volume? Do your 15's have good upper end performance, so you wouldn't need to bother your 18's with that? Those cabinets don't look like they need more than about 200 dollar drivers.

[droberts]

Originally Posted by Andrew Eckhardt

Cal's got it. That's felt and fiberglass

What is the cabinet volume? Do your 15's have good upper end performance, so you wouldn't need to bother your 18's with that? Those cabinets don't look like they need more than about 200 dollar drivers.

The guy who sold them to me said they formerly had hl2880c PAS drivers in them ( 600 watts RMS ) . Thinking about those or JBL 2245 , I am looking to get some nice mid bass from my subs as well, sound quality is a priority (although they'll be backed up by atleast one or two JBL 728s and hopefully some folded horns. I will need to upgrade my mains as well , I have 4 JBL soundfactor (SF) dual 15 , 2 SF 12" monitors (which I might actually use for monitors ) . And 2 more dual 15" with a 5" and 1" horn ( they seem like much more solid cabinets than the JBL's) . I've upgraded some of the 1" compression horns to Seleniums from the stock JBLs .

[Xoc1]

OK Asbestos scare over!
From the dimensions you gave in your first post you seem to have a speaker box of about 500 litres or maybe a bit less internal capacity.
This is about the right size for a pair of 18" drivers
There are 2 off, 6" ports they seem to be quite short, so they are probably tuned to give a bass peak around 50hz . The tuning could be OK but the cross sectional area of the ports is probably too small to really work well.
The box looks quite basic so maybe you might concider modifying them.
Look at these plans on the speakerplans forum, g sub, to see what I mean about the port area!
Speakerplans.com
I think that at least another 2 off 6" diameter ports would help.
The 4 off, 6" ports would need to be longer to compensate for the larger area.
Or maybe you could cut out the baffle between the speaker holes and make a rectangular port like the G sub design.
Once the choice of driver is decided the ports can be tuned to suit.
As for what drivers to use. Questions to you are:-
What is your location (this is a global forum!) Speakers cost a lot to ship.
What budget are you looking to spend?
What power are you likely to drive the cabinet with?
Have you concidered the cost of an active crossover?
The size of the speaker cutout holes would also be handy!

[Andrew Eckhardt]

Maybe if you wanted to trim your amp rack and leave the 15s at home top end from the 18s would be important, but I'd try to design the subs for sub performance, even if it meant you usually needed 15s, which you already have.

The drivers that were in the cabinet don't mean a whole lot. Again, I would go for maximum bottom end at power. I don't think I would drive a whole lot more than a real 600 watts into that cabinet, unless there is hidden bracing. The one that goes from the center divider to the ends is a little funny. Those outside panels are the smallest area surfaces on the box, and the center divider will stay still at fundamental because each driver will load it equally. An "easy" way to beef that box would be to make posts or vented tube for the magnets to press against, and use T nuts to seat the driver, essentially pre-loading the largest faces. Of course you need to be sure the rest of the cabinet construction can withstand this or you will blow it right apart. By immediate looks, it wouldn't take it.

Please excuse, I didn't notice you posted the dimension right off the bat.

[Andrew Eckhardt]

Using your dimensions and everything easy to see I get about 9 cubic feet left over for the drivers.

The 2245h is perfect for that volume with a 20Hz port. Will give you a slowly falling response (for a ported box) with (edit: not very good) transient response at 20, but are there really any "transients" at 20?

I suppose the JBL has plenty of upper end, if you want that sound.

I didn't look at the other driver. The Peavey Low Rider will give you higher efficiency and much lower excursion at 30Hz, but that's the bottom of the band for it, while the JBL will go to 20 with good loading (at -10dB out).

[Andrew Eckhardt]

If you have the PAS driver available, do you have the specs handy?

[droberts]

Originally Posted by Andrew Eckhardt

If you have the PAS driver available, do you have the specs handy?

The spec sheet can be viewed here . http://www.pas-toc.com/pdf/LF.pdf , but if you get what you pay for I need to go higher end . mid bass is very important for the music I play , dubstep is a style with very fluid frequency shifts . I'm not sure how low I really need it to go though , is there some sort of frequency monitor you can purchase to measure the frequency of certain notes and hits ? I have logic ? All I know is that the 728 bridged on a crown xti 4000 seems to produce precisely the right kind of bass for this style of music , but I think I am leaning towards the 2258 as opposed to the 68's off a suggestion I got from a buddy of mine .

[droberts]

Andy where are you from in PA , I just left Philly not that long ago