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Multi-Way Conventional loudspeakers with crossovers

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Old 5th April 2007, 10:27 AM   #81
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by Scottmoose
.............................
Nothing fancy at all. Cheap Eminence Beta 15 bass driver mounted fairly close to the floor, XO to a Fostex FE167E at ~180Hz. Series XO, utilising the natural roll-off of the drivers. The baffle is relatively narrow, roughly 16in, triangular side-pieces forming a semi U frame, roughly 12in deep at the bass, tapering to nothing at the top. Sonics were downright staggering. For the megre price, I've heard little that gets close. Easy 40Hz, seemless transition. I went hunting for the XO, and I flat couldn't find it. Design was by JamesD, who frequents the World Designs forum, and has much fancier & most expensive acrylic versions -effectively a very highly modified version of the original Quasar using a 12in Supravox bass unit and AER MK1 up top. Bass isn't really dipole in radiation pattern in this layout, but it certainly sounds like it, and the things can be used close up to a wall or in corners will little degredation. ........................................


Best regards
Scott
this two?
I mean -three............
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Old 5th April 2007, 09:21 PM   #82
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Default Hmmm - Acrylic

Certainly makes the panel "disappear" visually, no small consideration when you're talking about a 12 or 15-inch fullrange coax driver with one or two 15-inch bass drivers on the floor. Heat-treating the outer edges also gives a desirable curved rolloff to decrease diffraction, maybe a 3 to 6-inch radius would be about right, and it also stiffens the front panel as well.

Hmm, food for thought there ... you could even take a hybrid approach, a veneered Baltic Birch plywood cabinet with fairly deep side panels for the bass modules, and a transparent curved acrylic section for the top with gently curved "wings" to minimize diffraction. That would look nice, perform well, and be easier to move around, since the top and bottom would be in separate parts, with the acrylic top resting on a felt layer on top of the Baltic Birch bass units.

Also glad to see the specs for the Hemp Acoustics 8, 12, and 15-inch coax drivers. They look promising for the dipole project.
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Old 5th April 2007, 09:34 PM   #83
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Default Still Thinking ...

I like that hybrid acrylic/wood cabinet approach, the more I think about it. The top portion is sort of an art object, whether you're talking about Lowther/AER, Jordan, or pro-quality coax drivers. These are expensive drivers and look the part - like a good tube amp or a custom motorcycle, you don't want to hide the technological beauty of the working parts.

The wood bass cabinet is interesting as well. I'm thinking of asymmetrical side walls to minimize standing waves. One wall would be short, maybe only 6 inches deep, and the other would be more like 15 inches deep. If there are two drivers, one would go on the front (close to the corner with the deep sidewall) and the other could go on the deep sidewall. Mirror-imaged pairs, of course.

I'm guessing the bass quality might be a little better if the side woofers fired towards the left and right sides of the room, which would improve the sensation of "air" and dimensionality in the bass region. People with stereo subwoofers know what I'm talking about.

Hmm, that's intereresting, swapping the bass cabinets left-to-right would actually swing the dipole pattern around. With the arrangement of the previous paragraph, the nulls of the dipoles are a bit closer to the listener, with side woofers facing the center, the nulls are steered towards the side walls of the room. One more way to tune the system to the room - steering the dipole nulls either towards the center or the side walls.

With a multi-tapped inductor for the bass drivers to control the overlap region, steerable polar patterns, and a pair of dedicated stereo subwoofers for the below-60~80 Hz region, there are a lot of ways to tune the system to the room. This is good, considering the wide variety of rooms out there.
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Old 5th April 2007, 09:37 PM   #84
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Default Re: Hmmm - Acrylic

My existing proto baffles are BB in the centre (with removable driver module) and plexi-glass extensions (total ~1.2m x 1.1 m WxH)

Quote:
Originally posted by Lynn Olson
and a transparent curved acrylic section for the top with gently curved "wings" to minimize diffraction.
Syncronystically, when i was just digging for some boxes to ship out a couple pair of FE12x, i saw & was reminded that i have a pr of unobtanium 3" neo cast-basket Tangbands in just such a baffle. Now if i can get the 4 x 12" push-push ripole modules off the paper and into wood i'd have some bass support to play around with.

Sorta like this -- different top...

Click the image to open in full size.

dave
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Old 5th April 2007, 09:41 PM   #85
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Default Re: Still Thinking ...

Quote:
Originally posted by Lynn Olson
I'm thinking of asymmetrical side walls to minimize standing waves.
And non-rectangular. 2 dissimilar trapezoids (and the angled trialing edges should be at a different angle. We have 3 pieces of Mercedes Benz plywood tucked away for a permanent baffle for a lovely (and rare) set of Korean alnico 6" FRs.

dave
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Old 5th April 2007, 09:46 PM   #86
agent.5 is offline agent.5  United States
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Default Re: Still Thinking ...

Quote:
Originally posted by Lynn Olson One wall would be short, maybe only 6 inches deep, and the other would be more like 15 inches deep. If there are two drivers, one would go on the front (close to the corner with the deep sidewall) and the other could go on the deep sidewall. Mirror-imaged pairs, of course.
if you do something like this, how skiny can you make the front baffle. If you make it really narrow say 10" for a 8" full range speaker, you can use a piece of acrylic to go the entire length of the front baffle (48" maybe), and the two sides (6" and 15") can be veneered wood (I like Zebrawood, bubbinga, but you may like something else)

Obviously, a 15" woofer will not fitted onto a 6" sidewall. But a 20" sidewall will do it.

From the front you will see the 8" woofer and the magnet structures of the bass driver. I think it will look good.

Maybe, Hemp 12 coax on a 48" by 12" front clear baffle.
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Old 5th April 2007, 10:35 PM   #87
Zen Mod is offline Zen Mod  Serbia
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slightly off topic..or not ;
I'm really interested in "JamesD's " OB approach,especially suited for smaller rooms,or at least better suited than Bionor likes....
anyway-just today I tried row of different oval and round AlNiCo Iskra drivers ,all placed on topp of right cab on pic.
that right cab was disconected, and one by one eeny weeny diver was connected instead.

amp for test was veeeery old Pioneer ,around 15W/ch good for two reasons - easy on ear (even if not last word in resolution and neutrality) and more important-with cap in output ,so pretty forgivable for any short shortie with speaker wires

what most impress me is fact that(even if I'm long ago converted to ancient odd spks) all tried radio ,PA column and grammo spks were not much worse than entire cab on left side!!!
even if almost all of them sounds pretty mediocre in almost any sane cab.........

just for record: I also have several more than bad AlNiCo spks.......so-even than bad spk was bad

all this mumbling just in apologetic purpose for OB............any decent spk will sing on OB ,comparing it to situation when is closed in anything worse than perfect cab .........


hehe.....Eminence Alpha 15 is ~ 45 Euros a piece around me ......

I can see already one OB pair (Alpha 15 + some old AlNiCo) in every room


btw-interesting link.....not much theory but..........

http://www.lampizator.eu/SPEAKERS/PR...0projects.html
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Old 5th April 2007, 10:42 PM   #88
Floric is offline Floric  Europe
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Hi Lynn,

sorry for hiijacking this thread.

The first thing I want to tell you is that I hope, that you are able to cope with the experiences you made. I had a nephritic holdup some years ago and I do not miss the pain. I did not have an accicent like yours right now - I am lucky. I wish you, that you are able to forget the shocking experience you made and that you are able to take your advantages of the moments you can not forget. May the music and the stuff we are constructing here help you.

Several posts ago you wrote, that a linar array would lead to problems because of the timing - the sonics from the outermost sources of the array reach the ear of the listener later. You proposed a geometry that is tilt towards the listener to avoid this effect.

I Think that you are not right. The effect of a line array is that every driver gets focused in the horizontal plane with the help of the other ones because delays of a half wavelength get canceled (though I have been studying physics for some years, I am not able to explain it a better way with some words - if you want a better eplanation read "QED" from Richard P. Feynman or send me a pm). When you are listening to a line array, you are listening to the speaker that is at the hight of your ears. The problem of a linearray is, that this effect is dependent of the frequency. As a consequence you get this "comb filtering" effect. In normal listening environments this effect is smeared by the room with the consequence of an inaccurancy in the time domain. But you will never hear the sound of the outermost speaker with a delay.

Best regards and best wishes

Floric
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Old 5th April 2007, 11:18 PM   #89
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Zen Mod, that link is to the "Kingston" guy. He is from Poland I think, had a great website a while back with about half as many projects. At that point he had transitioned to open baffles for his wide mid range drivers with a ribbon tweet He was a strong influence on me and made a lot of sense. Probably made me decide to do the Basszillas ... that have open baffle mid and ribbon highs.

I still have text from that site and it is very informative. Too bad he doesn't include it now. Maybe I could ask to post it here..

Now he seems to have go all the way with open baffles and also uses vintage drivers... Planet 10 will approve of that! Makes them hard to clone though.
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Old 5th April 2007, 11:32 PM   #90
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by Variac
................... Makes them hard to clone though.

not if you have on shelf what I have

but- you're right for P10.........even if I hate him.........because of his shelves...
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