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Old 2nd January 2013, 10:36 PM   #11
Xoc1 is offline Xoc1  United Kingdom
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The Delta 15 LF requires a far bigger cabinet to get a smooth frequency response. In fact Chris661's suggestion to use only one driver per cab is not to impractical. But this would severely limit the power handing.
have a look at the cabs on the Eminence site
http://www.eminence.com/pdf/Delta_15LFA_cab.pdf
Notice the big cab is limited to 175W & the medium size cab is 250w.
For a double 15 simply use twice the volume shown for a single cab to get the same response. Note that Eminence are suggesting 4 X 4" 100mm ports per speaker.
One suggestion. If you can not get the ports to fit in the front how about putting them in the back of the speaker? Not common I know, but would work better that you might expect!
We know the outside dimensions of the box and the drivers that you have. If you can post some pics of the cabinets and maybe some details about how you plan to use them that would help people to help you get the best out of them.
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Old 2nd January 2013, 11:25 PM   #12
sreten is offline sreten  United Kingdom
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Hi,

Forget about ports, they wont work with your drivers and cabinets,
go sealed and stuffed. The lower your maximum levels, the more
low bass boost you can use, making the set up very flexible.

Small space - use them unassisted with bass boost,
big space - use them flat with some additional big subs.

The high Qts of the raw drivers, 0.6, prevents simply venting for
power handling and SPL rather than extension, though you could
still do that with advanced EQ, to cut the upper bass boost.

rgds, sreten.
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Old 3rd January 2013, 12:02 AM   #13
Mr dB is offline Mr dB  United Kingdom
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Riiigghht ok. Well I plan to use them as subs, but I've only bought enough drivers to fill 2 of the cab atm, so the other 2 could have better drivers in them.

So you think ill have know chance of getting a decent sound out of them? I mean i've done some calculations on ISDwin (forget the name, correct if wrong) and it says with the cabs I have and 4 - 4" ports with a 13cm length I could get a good 45-50Hz. But maths, weirdly, can lie.

I desperately need to use these cabs, and these drivers some how, as I can't afford anything else atm. In future I will purchase some good RCF or better eminence.

And, tbh, I don't really want a closed box, unless it will really benefit?
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Old 3rd January 2013, 12:06 AM   #14
Mr dB is offline Mr dB  United Kingdom
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And looking at that link Xoc1 the single 15 cab has a volume of 5.5 cu.ft well my cabs are 9.1 cu.ft atm, so it's only 2 cu.ft out, will this effect them that much? or am I being young and naive?
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Old 3rd January 2013, 11:38 AM   #15
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Quote:
Originally Posted by Mr dB View Post
And looking at that link Xoc1 the single 15 cab has a volume of 5.5 cu.ft well my cabs are 9.1 cu.ft atm, so it's only 2 cu.ft out, will this effect them that much? or am I being young and naive?
Undersized cabinets give higher cutoffs. WinISD will show you (to some extent) what you can get away with.

Block the existing ports, add your own at the back - you'll have far more control over the system performance.
The biggest problem with small ports is that they work fine at lower volumes, but when the cones start moving, they can't move the air fast enough (too much friction) so kind-of "lock up": you won't get much more output from them.

Alternatively, go sealed.

Still not sure why you want to end up with 8x 15" drivers: you will be able to cause structural damage to buildings. What's your application?

Chris
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Old 3rd January 2013, 12:54 PM   #16
Mr dB is offline Mr dB  United Kingdom
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Right ok, thx for the help!

Well i'm only going to have 2 - 2x15" cabs and then get some 18" and fill the other two for real low end, 30-90/100Hz stuff. then have the 15"s above them.

Tom
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Old 3rd January 2013, 08:55 PM   #17
Mr dB is offline Mr dB  United Kingdom
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Hello, update! i'm sacking the deltas! your right of course, the cabinets are way too small!

Gonna go with some Kappa's like you suggested, thank you. sorry for being a pain, but i'm new to all the mathy stuff and i'm just finding a leg to stand on. Thanks for the help, no doubt ill need more soon :L

Cheers, Tom
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Old 4th January 2013, 01:41 PM   #18
Xoc1 is offline Xoc1  United Kingdom
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The Eminence Kappa Pro15LF2 is a nice sounding driver.
So a plan of action might be......
Block the existing ports with decent thickness timber and lots of glue. Do this on the outside face of the baffle to keep the inside volume as large as possible.
Source some plastic drainpipe for ports maybe 100mm dia or similar, measure the inside diameter for calculating the cross sectional area.
Carefully measure the cabinet internals to calculate the true volume.
Input all the data for the cab and driver into winISD pro which is a free download program.
Tune the cabinet sim for a flat response.
Add additional ports matching the pipe diameter and see how this increases the port length required. The ports meed to be short enough to fit in to the box with at least the port diameter clearance to the back of the box, ie the port tube needs to be at least 100mm less than the box depth to breathe.
Cut out holes and fit the new port tubes.
Preferably measure the speaker using a frequency generator, amplifier & DVM to confirm the port tuning is correct.
Lots of steps maybe, but if you do it right you wil have something to be proud of at the end!
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