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-   -   Still need assistance designing a midbass cab (http://www.diyaudio.com/forums/pa-systems/220889-still-need-assistance-designing-midbass-cab.html)

klampykixx 3rd October 2012 09:19 AM

Still need assistance designing a midbass cab
 
Hi guys. i had my first proper gig on the weekend and have established that 4x SS15 subs are well and truly awesome, but my tops just cant seem to make the right amount of noise to keep up.

now, they sound great. theyre currently reflex cabs, tuned on Bassbox pro to 80hz, with a 100hz 12db/oct HPF. fitted with Eminence Delta12a drivers, and a compression horn 1inch throat.

so, what im thinking is giving them more directivity and fitting them into a horn cab.

heres what i had come up with at the time of typing this, i have since played with HR a little more and come up with a smoother hump around the 300-400hz by shortening the horn down from 400mm to 150mm.

http://i930.photobucket.com/albums/a...ta12HRplot.jpg

i just feel from the weekend, that the deltas just arent enough on their own to give that full "kick" or "slap" that the SS15s dont seem to deliver.

on that note though, i didnt exactly play with the XO filter on the EQ either. so its possible that with a bit more tweaking on the active filter, that i could achieve more punch/kick from the SS15 subs.


here is the HR plot of my current reflex cabs, grey line, and the proposed horns, black line.

lengthening the horn spikes more, shortening it brings me a smoother response. i guess due to focusing i guess...

http://i930.photobucket.com/albums/a...flexvshorn.jpg


i can see that HR has tapered off the response of the upper mids naturally occuring to the delta, will having the "horn" (read waveguide...) in front help to improve upper mids as well?? if so, im probably going to go ahead with this basic design.

Xoc1 3rd October 2012 12:42 PM

Hi Klampykixx
Try looking at this thread
http://www.diyaudio.com/forums/pa-sy...ll-pa-top.html
It might give you a few clues towards designing your mid top.:)
Regards
Xoc1

klampykixx 3rd October 2012 12:47 PM

thanks Xoc1, i did read that thread actually, as i did do a bit of searching around before posting.

my only constraint is that it fits on top of my SS15 sub. so limiting myself to 22inch (~600mm)

http://i930.photobucket.com/albums/a...929_165111.jpg

additional to the existing tops to start with, and then replacing current ones if all goes well.

klampykixx 3rd October 2012 01:23 PM

just realised something rather stupid.

i purchased a while back, plans to built an OT12 off the BFM site. the strange thing is, that the cabs i have drawn up are so similar to the BFM design... i had completely forgotten about that design... well. at least i know im on the right track then.

anyone else have any suggestions or help on this matter?

can anyone explain why the pioneer speaker shows so much more spl than the delta? is it the impedance? (or lack of?) or just a combination of factors?

NoDestiny 3rd October 2012 04:07 PM

I have been designing some bi-amped 2x12" + 1" horn cabs for my future PA system, so this thread definitely interests me. Do you have any more information on your current cabs? I see "reflex cabs, tuned on Bassbox pro to 80hz, with a 100hz 12db/oct HPF. fitted with Eminence Delta12a drivers, and a compression horn 1inch throat.", but not sure on how many cubes per cab. Also, 2 drivers per cab I assume?

klampykixx 3rd October 2012 09:56 PM

What exactly would you like to know ?

klampykixx 4th October 2012 02:06 AM

Quote:

Originally Posted by NoDestiny (Post 3188788)
Also, 2 drivers per cab I assume?

currently i have 1x delta12a and 1x 1" compression horn in each cab.

i still might get another pair of deltas, but at this point im thinking that the horn cab will be enough to bring my perceived output to the required level.

as i said before, they sound great, certainly not complaining about their sound. just feel theyre not quite loud enough. its litterally only just not loud enough.


Quote:

Originally Posted by NoDestiny (Post 3188788)
but not sure on how many cubes per cab.


cabs are about 50L internal volume.

Xoc1 4th October 2012 12:54 PM

How miuch adjustment have you on your crossover settings?
100 Hz is quite low for a Delta 12a which has a fairly small Xmax.
As an experiment you could try stacking your existing 12" +1" cabs on top of each other - inverting the top cab to keep the HF as close together as possible. This will give you an idea how it would perform as a double 12 cab.
I tried this myself recently with a pair of my mid tops and it worked OK but I had to adjust the crossover frequency of the mids to the HF to below 2 KHz.
The other issue you have to address is your compression drivers and the crossover.
A horn loaded mid would require a better compression driver, as would a double 12" and compression driver cab.
Have you seen these mid top horn loaded plans for a double 12"
Speakerplans.com
Regards
Xoc1

klampykixx 4th October 2012 01:30 PM

i do like the look of the MT112. what i had in mind to build was much more simple than that tho... lol

had my system setup in a sporting hall tonight, and with a bit of EQ tweaking, and Sub LPF adjustment, it actually sounds reasonably clean and solid, without any real gaps in response. i didnt realise the sub LPF was set at 75hz. i lifted it tonight to about 120 and gained massive punch from the subs. normally i have the 35hz EQ slider minimised to -12db, but tonight i lifted it to 0 and must say, it sounded so much better. also, dropped the HPF filter from ~50hz to about 40hz on the EQ as well. (ive got a picture of the settings but cant upload right this minute, so ill have to do it later.)

as far as adjustment on the cabs XO, its passive, and i only recently tweaked it , i fitted a selectable 100uf cap on the input so i can select whether or not the cab plays full range. or is highpassed at approx 80-100hz (12db/oct) and yes, it makes a big difference to how much power they can take.

id be very interested in owning a second pair of Delta12's but havent got a spare $300 atm...

nothing will happen this side of november anyway, so it will stay as is for now. unless i find funds to build more cabs and slip the pioneer drivers in for interim. <which is the plan for the new cabs regardless, since i have them here sitting doing nothing.

chris661 4th October 2012 02:45 PM

Can you put any more power into the tops?

If its the drivers that are giving up, you could try a steeper and/or higher crossover to give them an easier time, but more power wouldn't help.


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