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Old 6th August 2004, 11:46 PM   #1
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Default open baffled all over again

hello guys, (and girls)

in between my exams so time for surfing. I have red the open baffle topics over and over.

i have got some questions about drivers.

i wanna make an complete open baffle,
the lows : open baffle sub
the rest : fullrange open baffle


for the fullrange open baffle, i think i would use an coral driver, but Frank, aka mr tube told me that the highs are not always there, so probably i'm gonna use an super tweeter; the woofer will be crossed over with linkwitz filter at ~100hz, then for 100 to 12000 (maybe 15000) the fullrange and then the tweeter comes in;

but now my two questions;

1) as a fullrange driver i have seen something new, (well for me personally cidada if i can lay my hands on a coral, probably i'm gonna buy that; but what do you take the coral, or the cidada; and most of all : why ; or would you step to a smaller model like fostex 127 or something. (i have the feeling that an 8 inch drive would perfrom better) (take for example the saba's of telefunken full range)

2)the subs; i have seen that nuke searched the whole got d*** planet, at least in europe, for a decent driver. He came up with a few; now i have found some to.

the question is are we gonna use PA material; if so on ebay you can get an eminence beta 15 for less then 50 euro.
But what if you wanna use "home" woofers; i have looked at gradient, because they are cheap, the have an 12 inch driver for 40 euro, it has an FS 32, allright not that deep, but i don't need anything lower. and also 93db sensitivity which isn't exactly super high, but still, i don't play that loud. oh yeah here is the url
http://www.plus-elektronik.de/shop/i...tieftoener.htm
but it is a light cone, and probably rather fast.
i know it isn't an xls 12 peerless with 40mm lineair excursion, no it's one with 4mm lineair excursion, but since it has more sensitivity and most of all more Qts i doesn't need to be driven so hard. personaly i think an home-woofer will sound better, but wil it be enough?

Well actually my question is: what do you guys think of it.

thanx a lot guys, now going back to Mr. Kant and his Grundlegung zur Metaphysik der sitten.

greetings
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Old 7th August 2004, 01:00 AM   #2
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There is one problem staring me in the face, the excursion capability of the fostex full range. There is a reason linkwitz chooses 8" drivers with large xmax in his dipoles, because you need it. Unless you can use "wings" or whatever to extend the dipole down to the xover of 100hz I think you will run into problems with max SPL. A larger cone reduces the excursion demand at lower frequencies so that will help somewhat.

The XLS has 25mm linear excusion.
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Old 7th August 2004, 01:33 AM   #3
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yeah, that's a good explanation, it sounds very logical to me, i think the baffle will not be more then 50cm wide, but i can always put whings on it.

damn you'r right, i have to think again, because i wanted to put the fullrange ontop of the open baffle woofers, but since they will be at least 60cm high, the baffle wil be to small in hight also; so probably i will have to seperate everything

thanx for the info
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Old 7th August 2004, 01:45 AM   #4
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Without big excursion you are going to need multiple drivers for the low frequencies because dipole bass is even more about moving a lot of air. Even 4 of those 4mm xmax 12's per side isn't going to cut it. A single high excursion 15" per side like the dayton IB15 may not even be enough to keep up with a highly efficient full ranger depending on the volumes you are looking for.
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Old 7th August 2004, 06:25 PM   #5
DougL is offline DougL  United States
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I have been sketching a design for a low frequency dipole unit.

Starting point for my "design" is the Likkwitz PW1. I am also examining the Na0 design.

For anyone that hasn't seen the PW1, itís an H baffle dipole with dual 12" Peerless XLT drivers and a D of 12 inches.

The drivers for the project are $150 or so each, for a total of $600. The challenge is to make other design choices that will work for us.

Doubling the D of the H enclosure to 24" would halve excursion requirements of the drivers. Choosing drivers with an F3 of 40 Hz
(And not compensating below that) would also halve your excursion requirements. This seems to indicate that "normal drivers" are possible candidates. The Na0 documentation indicates that the 24" U would halve the excursion requirement again, or allow for 1 woofer rather than 2. I may try both.

I was looking for something with a Qts of .5 to .8 so I could minimize compensation in the crossover.

I just saw that 15" Dayton IB. Looks perfect.

Let me know how your design works out.

Doug
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Old 7th August 2004, 08:49 PM   #6
NH7RO is offline NH7RO  United States
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Default TC2+ 12"ers

Doug, you might want to check out the new TC Sounds TC2+ woofers---John Marsh is using them in the Arvo Part dipoles with great success and they're garnering rave reviews in the Madisound Forums, too. About 20mm xmax, aluminum cones and cost is also around $150 each from O Audio in Texas. I've got four I'm building 18x19.5x28 well-braced H-frames for right now and can't wait to get them up and running....
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Old 8th August 2004, 02:16 AM   #7
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I used 2 per side of 18" Studio Pro PW1808. Xmax 4.6 mmQTS .82.
Small wings on the baffles. The cone hardly move on heavy rock at ear splitting levels.I have never seen in practive why this "thing" about huge Xmax. In theory yes. In practive no. Why is this?There seems something going on with open baffle that is baffling.
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Old 8th August 2004, 03:02 AM   #8
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Default I agree...

I put together a pair of simple H frame dipoles using a single hi-Q 12" driver for each, OK they soak up more power than the closed boxes they replaced, but unless you really want to annoy the neighbours (& lose your hearing) I think more than 2 drivers a side is a luxury....
Pete McK
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Old 8th August 2004, 03:11 AM   #9
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Peter,
The Fs of that driver is 24.5hz . The rock you are playing at "ear splitting levels" doesn't have low content. If you play something with content anywhere near resonance, the drivers will bottom out with relatively low power applied to them. It sounds like they are perfectly suited to your needs, just be careful of low frequency content. You also have the advantage of 4 18's which move alot of air with small excursions.
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Old 8th August 2004, 03:27 AM   #10
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Hi johninCR,

I do not listen to test tones for pleasure. 24 Hz is pretty low in my book. I have some EQ on the drivers, and playing say Dark Side of the Moon on an Allen Wright moded SACD player at very high levels, as I say, and others have confirmed, on an OB the cones do not move as the books tell us they should. Nothing like say my old Tannoy 15" in a reflex box. I know that this is comparing apples with pears, but I cannot see this fixation on Xmax when clearly it is not needed. There is more going on with OB's than is generally recognized
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