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Multi-Way Conventional loudspeakers with crossovers

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Old 1st October 2002, 05:35 PM   #21
diypole is offline diypole  United States
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Default my mid-high proposal

New here, so hello all!
How about this instead of the tang band in a line array.
http://www.partsexpress.com/pdf/264-712.pdf
I will be receiving my first pair tommorrow, and experiment with crossing them to a 10 inch audax and Peerless in a dipole (hoping for a 500hz xo).
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Old 1st October 2002, 07:21 PM   #22
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Has anyone bothered to read John Kreskovsky's web page? He has a lot of info on transient perfect speakers which can reproduce square waves. See http://www.geocities.com/kreskovs/John1.html especially his filler driver project.

Also, Dunlavy speakers supposedly reproduce square waves.

RonS
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Old 1st October 2002, 08:42 PM   #23
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Hi Transducer,

We went through John K's site in this thread:
Can't Reproduce a Square Wave.

He has some good stuff, but falls short of reproducing a square wave.
I'll checkout the Dunlavys

Rodd Yamas***a
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Old 1st October 2002, 10:32 PM   #24
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diypole:

I looked at the .pdf file and my first reaction was, "I wouldn't use this driver on a bet.". Anyway, it doesn't go low enough. I'm thinking that a mid with a sealed resonance of around 70-100Hz is the best choice. As a side note, if manufacturers can't come up with drivers that don't need notch filters, they should be in another business IMHO.

roddy:

I don't like the idea of padding drivers with resistors - the damping will go out the window for some of the drivers and, worse, the overall efficiency suffers. I see the mid-range system as sealed and curved and a diamond shape here would be more difficult though not impossible, woodworking wise. Still, the diamond shape, or it's reverse, the bow tie, is worth keeping in mind.

Following phase_accurate's suggestion would eliminate the need for a curved baffle in the first place. It would solve the vertical lobing problem, keep all drivers in the array active at the lower frequencies and therefore maintain the power handling capacity where it is most needed. In addition, it might help or possibly solve the step response problem. I believe I will try it but I'm thinking it might negatively impact the square wave response.

I think, conceptually at least, some progress is being made and there are some good suggestions. I very much like the idea of using the mid-range enclosure <i>shape</i> to carefully manipulate the response. In the past I have built a large number of extremely odd looking systems so I am no stranger to the aesthetically unusual.

My only hope is that project does not become my worst nightmare!
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Old 2nd October 2002, 12:20 AM   #25
diypole is offline diypole  United States
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Bill,
The resonance is due to the cavity created between the two rows of magnets. Since these drivers begin to beam around 6-7000hz, I would ideally cross them over at 3-4000hz to cheap 3/4 inch domes situated at the sweet spot, and shoot for a line of H baffled 10 inchers crossed between 5-1000hz on the low end. This would also help with the lobing issue, as well as "overblown" soundstage.
Right now I am experimenting with actively notching out the resonance and crossing to a ten inch peerless csc and a ten inch audax in a dipole baffle 11" wide with 3" wings. This will then be crossed to a W frame dipole subwoofer I have already built.
For all out dream square wave action though, it would be the big brother to the neo 8 the RD75, also sold at parts express for $685 a piece. This 75" planar magnetic ribbon would be actively crossed to a diy electrostatic panel such as the Metaxis around 500hz. I will look for links to post in the morning.
regards, Jason
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Old 2nd October 2002, 01:56 AM   #26
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diypole:

Regardless of what causes the resonance peak, I don't think these are suitable for a first order crossover, or something close to it, to a tweeter. To my mind, the big brother at $685 is out of the running. I don't really buy into the idea that a really good system needs to cost big bucks.

As far as I can tell, a non-curved vertical array relies on the "multiplicy of drivers" to fill in the holes created by the "multiplicy of drivers" not being "time aligned." This might result in a fairly uniform frequency response but this is not the only criteria of our project. <i>I image one could achieve a fairly uniform frequency response with 100 drivers randomly placed throughout a room.</i> One of the ideas here is to have everything arrive on time - not 360 degrees, or more, later. I don't believe that a non-curved array, phase_accurates suggestion being the only exception I've heard thusfar, can accomplish what we are after. In addition, what's the difference between an array of planar drivers and an array of small cone drivers? Mostly the cost, it appears. In fact, I think a vertical, non-curved array of 18 3" Tangbands at a cost of $180 will outperform the 75" RD75 at $685.

Nothing but the facts will deter me in my belief that a reasonably priced, superior system can be put together with the proper application of intelligence, off the shelf products and a vision.

I don't know what an "overblown" sound stage is and I don't understand your abbreviations - H Baffled, W Frame. How about sticking with terms we all know - even the newbies who may be attending this thread?

I did look at the site explaining the RD75 and was not overly exited by their presentation which seemed less than factual, mostly by omission of relevant data.
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Old 2nd October 2002, 12:04 PM   #27
diypole is offline diypole  United States
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A w frame dipole woofer- http://www.linkwitzlab.com/woofer.htm
Here is a link to John Whittaker's site, who has done considerable research with the RD75 since they became available to the DIY market- http://www.snippets.org/alsr/. The neo 8 is only about $58 a peice, and all these drivers have been used in highly praised commercial systems for some years now. Many on the dipole list are experimenting-dipoles@topica.com.
Line sources are unpredictable, and Whittaker has measured "floating peaks" with the RD75. Lobing and comb filtering at higher frequencies when using multiple drivers can be somewhat attenuated be tapering the array(successively lowering the crossover point toward the ends of the line). What I mean by overblown soundstage is that the size of certain instruments presence may be exaggerated by the line in my experience. Perhaps, as Linkwitz has suggested, the way to go is WWMMTTMMWW, which of course is a kind of tapering of the line, like a huge MTM.
I am not a rich man either, that is why my current experimentation uses the neo 8 to replace a tweet and lower the crossover on my dipole panel. The main reasons I suggest these types of drivers(planars and electrostat woof) for your project is that-
1) they have a much lower moving mass than dynamic drivers
2) The diaphragm is driven uniformly over it's entire area resulting in very little excursion
3) They store very little energy
4) If you run the Planars without a tweet you will have only one crossover to the electrostatic panel at between 3-600 hz.
5) The planar represents a very flat impedence of 6 ohms to your amp
which I beleive will all contribute to your goal of passing a square wave. I am an active crossover person and think that you will have a better chance of passing a square wave with nothing between your amp and the driver.
Regards, Jason
ps. This place is great
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Old 2nd October 2002, 03:57 PM   #28
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Bill,

Quote:
I don't like the idea of padding drivers with resistors - the damping will go out the window for some of the drivers and, worse, the overall efficiency suffers.
I agree, series resistors = bad, but parallel resistors = not so bad. If you just use parallel resistors to divert the part of current (as long as the impedance curve of the TBís arenít too bad) away for the driver, you attenuate the output without having a large effect on the damping. Efficiency is still less, but the net effect I no worse then the lo-pass filter, and you eliminate the extra 90 degree phase shift.

Rodd Yamas***a
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Old 2nd October 2002, 04:40 PM   #29
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roddyama:

Sorry, hanging a resistor across a driver doesn't "divert" current away from the driver. The resistor will just draw additional current from the amp.

diypole:

Your proposals and suggestions do not set well with me regarding this project. Now you have the Neo8, a tweeter, an electrostat and some woofers turning this into a 4 way system with all its attendant physical and electrical complexities.

Not wanting to be closed minded though, I'm wondering how far along you are with your project . Do you have any curves or listening experiences to share with us?
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Old 2nd October 2002, 06:31 PM   #30
diypole is offline diypole  United States
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Two different systems; Let me separate.
Dreaming dipole square wave system: two way, RD75 actively crossed to DIY electrostatic panel between 3-500hz.
More practical system might be line of neo 8's actively crossed to a line of 10" woofers on an open baffle. I, myself, am striving for a full range 2 way dipole.
Personally I would not use a tweet with the Neo8. It sounds fine to me without and I'm finding if I stack 2, I might not need the notch filter either, as the response seems to smooth a bit. Some have suggested that the 2" wide kaladex ribbon begins to beam around 6-7000hz(agreeing with the physics), thus I suggested the 3/4" dome crossed at 3-4000hz. I have a strong preference for live recordings, and detest the harsh, close mike techniques commonly used today, therefore the neo has plenty of high end for me without the tweeter. Even the guitarist himself does not hear treble like he has his ear to the instrument, but perhaps the violinist does, lol.
I have only been experimenting with these drivers a couple nights(after the kids are in bed), and currently lack the capability to post curves, but initial impressions are good and I am hopeful that I will be able to switch from two 8" drivers and a tweeter, to one 10" driver utilizing the neo 8.
In general though, I can say that the ambiance produced by this main panel is much closer to a real live presentaion than what I have previously experienced, and acoustic guitar has been let out of the box! Those strings sound plucking good.
What is the lowest xo that could be used with your tang bands?
I agree with phase accurate, in that a tapered array would be my first experiment with the tang bands. I also think I might build a test baffle hinged at listening height, so that I could keep pushing the center back and try physically time aligning the drivers as you suggest. Having someone sit at the listening position and hold a string to their ear while you run the other end from ceiling to floor would give you an idea of where this arc should contact ceiling and floor compared to center. But I'm probably nuts. Gotta go
regards,
Jason
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