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Multi-Way Conventional loudspeakers with crossovers

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Old 19th April 2007, 07:33 PM   #381
owen is offline owen  United Kingdom
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The only concern I'd have with that is the driver break up will start to occur in a 15" around 2 k maximum, and thats only 1 octave away, so 6 or 12 db down on a simple non-digital crossover.

I understand the concern with the dispersion of a larger driver, but as such life is always a compromise...


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Old 19th April 2007, 07:53 PM   #382
BudP is offline BudP  United States
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Hi all,

Not to belabor the point ...oh no not at all.... and here we go again...

The EnABLE cones, from my experience, all have dispersion angles that are controlled by the cone angle of incidence. If the driver has a dome, and the dome is treated, you can be certain of getting significantly smoothed high frequencies and they will be controlled in dispersion by the cone walls.

Not kidding here, but, I have almost no experience with open center drivers. Although the highs will be just as smooth, I am not dead certain that the dispersion will be just as it is when the dome is present.

A center horn can also be integrated much more smoothly with a treated cone, but , you will have to ditch the screen, and you want to, trust me.

Bud
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Old 19th April 2007, 07:57 PM   #383
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My own choice for best voice reproduction is no more than 6 to 8 inches in diameter for a midrange without crossovers at voice frequencies.
Baffle trials with a modified Alpha 6 then become possible with LF helpers gradually crossing into the upper bass range.

Hi John,

I am curious about your comment for the rear wave being angled downwards when you tilt an OB. Presumably you mean where a FR driver is completely open backed.

If there was some felt like damping behind the main driver and the baffle was sitting on the floor, do you expect the same thing to be deleterious, especially for a system that will need to be domesticated and sit closer to a room corner?

On the same tack, surely this would not affect LF only drivers mounted at floor level?

Cheers ........ Graham.
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Old 19th April 2007, 09:26 PM   #384
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Quote:
Originally posted by swak
Owen and Jeff Mai,

the dispersion mismatch would be large if a 12" driver is used, that was the problem I tried to point at.

I feel the 6" from 18sound looks really nice, no crossover, very high sensibility, low stored energy...

Now, since the idea has been here to use a larger driver for higher dynamics I have a question:

how bad would the combing effects be if a PAIR of 6" are to be used to 5kHz? The straight sides of the drivers make them placeable very close to each other, naturally in TMM config.

if this is bad, how about one of them with an appropriate low pass filter?

Looking at the 6ND410 data, it has a piston-band efficiency of 98 dB/metre. Two of them in parallel would be around 5~6 dB more, or about 103~104 dB. However, with the limited Xmax a true crossover no lower than 300 Hz with a 12 dB/oct slope would be wise.

The horizontal and vertical dispersion would start to diverge around 1 kHz in classic MTM fashion, with an implication that direct-arrival freq response curves no longer mirror the subjective impression of frequency response (this was my experience with the Ariel). As mentioned previously, a half-crossover could roll off the lower driver around 1 kHz, offsetting the gain from directivity we see in the published curves. This leaves the lower driver with 1.5 octave effective bandwidth, which begs the question of using it at all, since it's only "helping" in the 300 to 1 kHz bandwidth.

The added complexity of the polar pattern - using both together or with half-crossover - bothers me a little bit. There are a lot of polar-pattern transitions in the 200 to 5 kHz range, making the job of tuning the crossover subjectively a lot more difficult. I've designed 4-way speakers before, and tuning the crossover to be subjectively flat takes a very long time with all that complexity going on.

I guess this approach, with a full crossover somewhere around 300 Hz, and the onset of vertical beaming at 1~2 kHz, is more suited for folks who are comfortable with 3 or 4-way active-crossover systems, line arrays, or big, complex speaker systems. I've done 'em myself, but I've never felt the results justified the huge, years-long effort that goes into them.

The "telephone bandwidth" of 500 Hz to 3 kHz is a region where very small changes in directivity, deviations from flatness, or shifts in tonal character are extremely audible. Transgressing this bandwidth with multiple drivers of different sonic characters is the downfall of most overcomplex hifi speakers, and the reason why they don't sound integrated or coherent - unnatural, in other words, the opposite of a fullranger.

In other words, one or two 6ND410's would work fine, measure well, have plenty of power-handling, etc. etc. - but it takes away from the underlying design philosophy of what I'm trying to do - a wideband pro-quality driver with high power-handling that is augmented by complementary drivers in the bass and a HF transducer that comes in at a fairly high frequency. It reverts the design to a more traditional 3-way with a mid driver array - to me, this is the traditional "high-end" sound, which some like, but I'm not one of them. I'm guessing some of the readers of this thread would like it just fine, though - this is a matter of personal taste.

As for the sonically bad effects of beaming in a 12" mid driver, well, I very much liked the image, spatial, and 3-dimensional qualities of the Bastani Apollo. I didn't much care for the Prometheus, but then, the driver is completely different, and the whole Bastanis concept is critically reliant on the sonic goodness of the widerange driver, which uses no crossover at all, on either end. There's an actively-powered monopole sub that comes in around 160 ~ 200 Hz, and a horn tweeter with a phenolic diaphragm that comes in at some high frequency.

I'm not quite as much a purist as Bob Bastani, and am willing to do things like equalize and have complementary groups of drivers to flatten out the response. But I don't want to go as far as Siegfried Linkwitz, with multi-amping, low-efficiency audiophile drivers, and extensive line-level equalization. Having met both designers and spoken with each for several hours, I have a good idea where they're coming from, and what they want to accomplish.

My goals are different enough I don't feel I'm "ripping off" either of them - I'm not using their techniques directly, and my end goals are a bit different as well. It's kind of a middle ground between the two, maybe a bit more tilted in the Bastani direction.

The whole exact-control-of-polar-pattern is a religion I'm not a member of, having not been that impressed with any speaker that hews to this design philosophy. I'm especially unconvinced by the 90-degree controlled-dispersion school - maybe for PA use, but I don't think it works all that well in domestic environments. The claim of improved imaging in particular I find to be inapplicable - to my ears, speakers that follow these home-theater-influenced philosophies sound dry and closed-in, with not very good reproduction of depth and extra-width effects (which are part of any normal stereo recording).

Which is why I can see the need for rear-facing tweeters if HF directivity in the front is on the narrow side. In fact, I can see the need for two rear tweeters, one facing straight back and looking upwards at the junction between the rear wall and ceiling, and another facing sideways and looking up at the junction between the side wall and the ceiling.

Ideally, the "side" HF enhancement tweeter could be connected in the old Polk cross-channel arrangement, with the Left side tweeter having a +L-R feed, and the Right side having a -L+R feed. This way the antiphase signal - which is mostly reverb - keeps the ambient impression wide at the highest frequencies, countering the HF narrowing that is typical in narrow-dispersion speakers.
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Old 19th April 2007, 10:06 PM   #385
Variac is offline Variac  United States
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I remember references to "Stiff cones " and "pistonic behavior" here.

I believe that the old 15-16" drivers such as Altec had rather flexible cones, which allowed them to decouple for various frequencies. The the whole cone produced the low frequencies, the smaller area close to the center produced the higher frequencies.As the higher frequencies were produced by a smaller diameter of the cone, they had better dispersion. Smaller diameter voice coils seem to promote this characteristic. Is this impression correct?

I believe most "modern" PA drivers have stiff cones and huge voice coils. They are made to reproduce a narrow band of frequencies and handle lots of power. These characteristics are not necessarily what we want here. Now we also might not want a flexible cone either, for the disadvantages it brings, but we shouldn't be surprised that most current 12" drivers have a narrow range of response.

This is one of the advantages of the Eminence Beta, it is a more "old school" driver- small voice coil, more flexible cone. ( I think they recently changed the cone material and suspension though) Modifying this model is commonly done not just because it is cheap, but als ofor these other reasons.
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Old 19th April 2007, 10:08 PM   #386
Variac is offline Variac  United States
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Speak of the devil, I just looked up the Apollo and found this:

http://www.audioasylum.com/forums/ba...sages/470.html


here's the Apollo:
http://www.bastanis.com/catalog/prod...233290ef3c8154
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Old 19th April 2007, 10:19 PM   #387
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Quote:
Originally posted by Graham Maynard
...I am curious about your comment for the rear wave being angled downwards when you tilt an OB. Presumably you mean where a FR driver is completely open backed.

If there was some felt like damping behind the main driver and the baffle was sitting on the floor, do you expect the same thing to be deleterious, especially for a system that will need to be domesticated and sit closer to a room corner?

On the same tack, surely this would not affect LF only drivers mounted at floor level?

Cheers ........ Graham.
Yes, any kind of OB alignment excluding if you heavily damped rear wave for the main driver. I wouldn't say it's necessarily detrimental, but typically if you fire the rear wave angled down, it lowers the soundstage quite noticeably.

Lynn's a box guy, so I have to keep reminding him not to forget about the rear wave.
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Old 19th April 2007, 10:43 PM   #388
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Quote:
Originally posted by Lynn Olson
Two of them in parallel would be around 5~6 dB more, or about 103~104 dB.
2 drivers (in relatively close proximity) give 3 dB more efficiency whether in series or parallel. Sensitivity may be more or less depending on series or parallel wiring and the amplifier you are using.

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Old 19th April 2007, 10:56 PM   #389
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Quote:
Originally posted by Variac
Apollo
speaking of Apollo, the Llambda Apollo was probably one of the best 15s ever made... last comment Nick had on them said it would cost 10k in tooling to put them back in production... John at Styke (called something else now) would know who has the rights to the design.


http://www.diyaudio.com/forums/attac...amp=1133022200

http://www.diyaudio.com/forums/showt...333#post792333

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Old 20th April 2007, 12:29 AM   #390
Variac is offline Variac  United States
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Doesn't seem to go out to 8k like Bastani says his does...

(not that we have seen any that do in stock form.)

Then again, the Bastani might be rolling off at that point and be augmented by the tweeter a bit..

8K......
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