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Multi-Way Conventional loudspeakers with crossovers

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Old 10th October 2006, 07:42 AM   #21
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At home I use a 6 1/2 inch woofer in my folded voigt style speakers, only 4 foot tall, length of line is 7 ft. sounds great, the midbass is far superior to ported designs, and people cannot believe the amount of subbass that comes from them, people are always looking for the seperate sub bass unit that does not exist. I am very interested to hear how awsome the results will be with a 12". Wow interesting plan
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Old 10th October 2006, 11:14 AM   #22
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I'm ready
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Old 10th October 2006, 12:16 PM   #23
Pano is offline Pano  United States
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Quote:
Originally posted by punkrokr1701
I'm ready
There is your birthday present then.

Plug in that table saw and put in the ear plugs.
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Old 10th October 2006, 12:31 PM   #24
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Quote:
Originally posted by tinitus
From what I can read the BIB is a compromise by simulating a number of drivers.... from 5" to 8" .... with a fixed length

Are you really sure this will work with a 12"

I am not good in maths ... but dont you get a big change in exstension of the horn when the slanted inner baffle is that much wider in relation to the BIBs with smaller drivers
Good questions. Answering them in order:

No. I occasionally restrict line-length with low Fs drivers to keep cabinet height, and driver position to reasonable levels. In a BIB, horn length is determined by 1/2 the wavelength of the tuning frequency. Usually this is set to Fs, or just below, but if you've a low Fs driver things can get out of hand, so I tune a bit higher. FWIW, I've built a pair with the Fostex FF225K for a friend before now, which were 89in tall, approximately 178in line length to math their 38Hz Fs. Sound was -er, rather impressive. Like my FF165K boxes, but larger. In this case, we've a 45Hz Fs, which equates to a half-wavelength of roughly 150in.

Oh yes indeed. Of course it will work with a 12in driver. The physics doesn't change just because it's got a hefty cone area. Higher Vas & Qt simply require a larger box (cone-area per se has little to do with it).

No. Vb needs to swamp, or come close to swamping, the driver's Vas. Width and depth dimensions are usually selected to preserve the conical horn profile (depth needs to be 1.414 times width) though there is plenty of room for experiment here. Terry Cain's original cabinet had a 1:2.2 ratio for example. So long as CSA is preserved, you can try different things out. The internal baffle terminates in the centre of the cabinet, the same distance from the floor as from the internal front and rear walls.

The point above the driver needs a light layer of stuffing, and a nice thick carpet of the stuff on the internal base will absorb any stray HF and damp out reflections. Beyond that, stuff to taste once in-room. Because they use the room as part of the speaker, they all need somewhat different quantities, though most of the time, the above is all that you'll find necessary.

Deflector panels are a bad idea BTW guys -the bass we want couldn't care less if a corner is smooth or not, but the unwanted HF does. So abrupt is the order of the day.

Doesn't sound too scientific I know, but it works. The more we learn, the more we forget. These simple, traditional corner horns are as effective now as they ever were. 3 watts into these will blow your windows out. And they do dynamics like little else you will ever hear from full range, or wide-range, drivers.
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Old 10th October 2006, 05:35 PM   #25
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Quote:
Originally posted by punkrokr1701
I'm ready

Miracle!!! We are all in agreement- or as close as is possible for this group. Punkrockr- I really think these will do it for you. It is amazing that you will get your wish at about a quarter of the budget we had gotten up to! The only expense is the 12" driver at this time, and a lot of plywood or MDF.

http://www.partsexpress.com/pe/pshow...90-409&scqty=2

I got their actual price and it's $58 each. So for under $150 including shipping you will have all you need to get started. You can add the tweeter later, after the cabinets are finished and even after you have tried them with just the 12" at first if you want..

If the cost of plywood is too much you CAN use MDF (medium density fiberboard) . MDF is available in lumber yards and Home Depot type places. It is like a very dense particle board (DON"T use particle board!) The good thing about it is that it is only about $25 a sheet in 3/4" thickness. The bad things are: It is very heavy. Each speaker will use about two and a half sheets minimum so you and your dad should try picking up two sheets together in the store and decide if you can or want to carry a speaker of more than that weight, plus the driver weight.. The other bad thing is that it isn't anyways near as strong as plywood, so if you move the speakers much the corners will be damaged and worse. Of course at that weight, you probably won't be moving them much, unless you are thrown out of your house because the police keep coming due to neighbors reporting too loud music.....

Many people prefer the sound of Plywood in this use, but the differences are sure to be subtle enough to not matter to you. Still plywood is the best choice, and I found someting called "imported birch" at about $40 a sheet which worked very well for my big home speakers. So check different places...

Seems like you will need six sheets....
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Old 10th October 2006, 06:00 PM   #26
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Hey Scott! the 16.5" dimension is a small problem. If the internal width were 16", then we could get 3 pieces from one of the pieces of plywood. (actually 2 saw kerfs would eat up another 1/4" so the optimal would be 15 and 11/12's ! . So can it be made a tad deeper front to back? and a smidge narrower? We would get three from a sheet. The sides could be more than two feet as we will probably cut one side and one front or back from a sheet...The saw could be set and cut the 4 fronts and backs , and 4 internal baffles in one shot.

THIS isn't a big deal, as only one sheet will probably have 3 side strips cut from it, so don't compromise if it is a problem...

I will draw up plans, and it would be nice to fix this if possible, but it isn't essential...

Punkrockr: this will take a couple of days or more to draw up!.
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Old 10th October 2006, 08:16 PM   #27
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You can reduce the width by 0.5in. Just boost depth to 24.25in to maintain Vb and you should be fine. it departs from the ~ideal conical, but not by much.

The drivers are PA, the BIB type cabinet less so (apart from the size). Frankly, I wouldn't worry too much about origins anyway. I see nothing that suggests this should not work, and be a very entertaining, inexpensive project.

Path starts at the point at the top, expands downward, then flares back up and vents out of the top of the cabinet.
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Old 10th October 2006, 08:23 PM   #28
Variac is offline Variac  United States
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OK, Mr. Moose, should you post or send me a sketch about the placing and size of the internal baffles or can I figure that out from the website?


Good name possibilities:

Crazy Overgrown Audiophile Project COAP
Very Entertaining Inexpensive Project VEIP
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Old 10th October 2006, 08:38 PM   #29
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Internal depth of the terminus is 24.25in. Assuming 3/4in build material (& I suspect doubling the side panels might be a good move BTW) add 2.25in to that for a total external cabinet depth of 26.5in. Nothing really... (though I did a dipole horn that's 32in deep a while back).

So the internal baffle needs to terminate centrally; 12 1/8 inches from the front and rear internal baffles, and the same distance from the internal base.
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Old 10th October 2006, 08:44 PM   #30
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OK, I have no idea where to start drawing thisI on't even kno what the cbinet would look like. Those links don't wrok for some reason.
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