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Committed to 12" WO (Read 2265 times)
Braggi
Ex Member



Committed to 12" WO
12/01/05 at 16:07:00
 
After searching for 10" drivers for too many months that would give me the low Fs and min 96db I was looking for, I gave up and ordered some Emminence Kappa Pro 12s. I'm planning on building a pair of Wicked Ones with the 12" mod. Any advice would be most welcome since I'm going to use expensive wood and really want to get it right the first time. Fortunately I have good tools and lots of experience building precision parts. I'll probably take way too long building them, but that's my life.

I hope to stick as close as possible to Steve's design while still making room for the big drivers.

Thiele-Small Parameters:
Resonant Frequency (fs)37Hz
Impedance (Re)    5.46 ohm
Coil Inductance (Le)1.22mH
Electromagnetic Q (Qes) 0.25
Mechanical Q (Qms) 6.93
Total Q (Qts) 0.24
Compliance Equivalent Volume (Vas) 121 liters
4.27 cu. ft.
Peak Diaphragm Displacement Volume (Vd)247cc
Mechanical Compliance of Suspension (Cms) 0.32mm/N
BL Product (BL) 17.3 T-M
Diaphragm Mass inc. Airload (Mms)  59 grams
Equiv. Resistance of Mechanical 
           Suspension Loss (Rms) 1.97N*sec/M
Efficiency Bandwidth Product (EBP)148
Voice Coil Overhang (Xmax) 4.8mm
Surface Area of Cone (Sd) 519.5cm2
Impedance at Resonance (Zmax)158 ohm
Maximum Mechanical Limit (Xmech)29.59mm
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J_Rock
Ex Member



Re: Committed to 12" WO
Reply #1 - 12/01/05 at 17:30:43
 
I don't remember exactly who did it, but someone was saying that they had good results when adding the 2 inches for a 12 incher, and then angling the compression chamber top down to a 10 inch throat height.

The 36 x 36 version also goes lower better than the 36 x 24.

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60ndown
Ex Member



Re: Committed to 12" WO
Reply #2 - 12/01/05 at 19:38:30
 
messing with the desighn could mess with the performance?
i would scale everything by the ratio of a 10 inch sub to a 12.(1.2)? not just angle the baffle.why do you need such high sensitivity? surely your going to be useing a seperate sub amp?
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J_Rock
Ex Member



Re: Committed to 12" WO
Reply #3 - 12/01/05 at 22:40:42
 
nah, scaleing isn't really the way.  Steve actually says to just add 2 inches to the height.
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60ndown
Ex Member



Re: Committed to 12" WO
Reply #4 - 12/01/05 at 22:48:45
 
[quote author=J_Rock  link=1133456820/0#3 date=1133476842]nah, scaleing isn't really the way.  Steve actually says to just add 2 inches to the height. [/quote]

in 35 words or less can you explain the difference between the 1.2 scaleing and the 2 inch add on with regard to final performance? it just seems to me that a 10 inch driver in the origional desighn would do its thing to the volume of air in front of it, and a 12 would need a little more room to perform in the same way?
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J_Rock
Ex Member



Re: Committed to 12" WO
Reply #5 - 12/01/05 at 23:02:58
 
Well, I haven't built both the scaled WO and taller WO at the same time in order to compare, but the taller sounded better.

I would explain but I just look to the way Steve suggests addign two inches to go from a 8 inch woofer to a ten inch woofer.

But look at the way steve's design is able to be changed in only one direction, anywhere from 24 to 36 inches long. The width stays 36 inches.  By scaleing you change the width, heigth, and length.  If you do decide to scale, scale all dimensions by an equivalent number. 1.2 to go from 10 to 12.
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DirtDawg
Ex Member



Re: Committed to 12" WO
Reply #6 - 12/01/05 at 23:36:27
 
Braggi,  :D Cheesy Cheesy Cheesy Cheesy

Nice driver. I have used a similar Eminence (older) and they KICKED A55 as midbass on a PA, direct radiating with 2 drivers in a 4 cubic foot sealed box. As much as I love big horns, DR Line Arrays have their place, too.

I remember reading that Steve D. recommends simply adding 2" to the height. I have done that and it works with Kickers in a car. Small Vas and large Xmax seemed fine and fairly well controlled.

Scaling the entire design may be better in this case because this driver's Vas=4.27 cubic feet. I would hate to see your driver have to face life in a bass cab with too much control over it's motion. Just a guess.
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Braggi
Ex Member



Re: Committed to 12" WO
Reply #7 - 12/02/05 at 02:24:58
 
[quote author=DirtDawg  link=1133456820/0#6 date=1133480187]Braggi,  :D Cheesy Cheesy Cheesy Cheesy
Scaling the entire design may be better in this case because this driver's Vas=4.27 cubic feet. I would hate to see your driver have to face life in a bass cab with too much control over it's motion. Just a guess.
[/quote]

Hmmm. I also have a fairly small Xmax so I don't want too much excursion either. It's always a tradeoff. That's one thing I've learned over and over on these forums.

60ndown, I wanted high efficiency because the tweeters are in the neighborhood of 110 db and I'd like to keep the system as balanced as I can. I'd like to be able to open up those HF horns and still be able to hear the bass. I'm building a PA system, so all the oomph I can get will be appreciated some day. If it works out I might even build a second pair. I chose readily available drivers partly for that reason. If they don't work as subs, I can always stick them in a DirtDawg style mid-bass horn, although, I got some less pricey 8 inchers for that little task. I have a 1,300 watt sub amp so I should have enough power for the WOs.

I have another reason for wanting a lot of efficiency. I'm hoping I can get a usable SPL using tiny digital amps. Not that I personally wil do much of that, but imagine a parade with a flatbed truck and a small band with a battery operated PA. Imagine a protest march where you can actually understand what the speaker is saying through what would otherwise be an undersized and overdriven PA. For voice only, the WOs wouldn't be needed, but most protests these days also feature a bit of live music. Activists typically have terrible sound systems. I want to offer a solution to that.

I've always thought that bass horns should work best while loaded somewhat more than the textbook amount; that is, similar to a compression driver. The additional loading should increase SPL and power handling. Seeing the plans for the Imperial SO and the WO-32 and hearing about DD's midbass setup supports that thought for me. The tradeoff, I'm sure, will be in the lowest octaves where too much loading will cause too steep a rolloff. I wish I could test it without building the boxes, but the build will tell. I may be able to make alterations after the fact if I'm not getting the performance I hoped for.

So, Mr. DirtDawg, I'd like to learn more about your midbass setup, although you did let a lot of the proverbial cat out of the bag. I've not figured out where such a discussion should take place. It seems we need a forum for PA applications.

Thanks for your observations everyone. It will be a couple of weeks before I start making sawdust, but I'll put up pictures and a nauseating amount of posts every time I panic and need support. Thanks for being there.
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J_Rock
Ex Member



Re: Committed to 12" WO
Reply #8 - 12/02/05 at 02:53:14
 
Also, widening the throat opening will increase high frequency output.
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richard03
Ex Member



Re: Committed to 12" WO
Reply #9 - 12/18/05 at 19:32:16
 
for handy info on pa applications use a different forum such as speakerplans (at least for stuff not covered by steves designs)
www.speakrplans.com
the faq is helpfull and the plans are good,, ive built some scaled down variants of their mt122 as single mid horn boxes for 10's work well and go pretty loud

ive aso built a pair of scaled up wo's for 12" pa drivers (beyma lx60)
be assured, they are nails cabinets when run loud from about 30-80hz , never had enough to give them their rms power of 1400w @4ohms but i imagine they would be pretty scary

also used a pair of eminence omega pros in one and that sounded ok so all should be well
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