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Multi-Way Conventional loudspeakers with crossovers

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Old 28th October 2007, 12:52 AM   #2501
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I wouldn't be shy about separating things - don't forget small winglets on each side of the baffle quite substantially increase baffle area - see the baffle by Magnetar referenced a few pages ago.

As mentioned by Magnetar and in the JBL brochure, you are free to independently lowpass filter each woofer - one can get wideband sound up to the tweeter crossover, while the other gets lowpassed at a much lower frequency (two octaves lower). If you take this approach, I'd put the HF radiator directly above the wideband woofer, otherwise the radiation pattern at crossover will be tilted sideways (as it must be in the JBL).
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Old 28th October 2007, 01:14 AM   #2502
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I concur with Salas' suggestion of a slight angle between the paired woofers, similar to what JBL is doing, if you want a side-by-side pair. In my baffle, it gets a little awkward because I want another driver(s) directly above the close-to-floor-mounted pair, and all those conflicting angles makes for a weird and hard-to-build baffle.
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Old 28th October 2007, 01:36 AM   #2503
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A quartet of 12" drivers (my favorite 12NDA520's or similar) mounted on a pair of hinged baffles with a slight (15 to 30 degrees) inwards bend should work fine, with the HF driver mounted directly above the widerange driver closest to the center of the soundstage, and the other top driver lowpassed two octaves below the widerange driver. Both the widerange driver and the HF driver should point inward - I like the old BBC method of crossing the pair at a point about 1~2 feet in front of the listener.

As per the previous discussions, the two drivers closest to the floor have their own amplification and EQ, matching them to the room and complementing the dipole rolloff of the upper set of drivers.

The radiating area of four 12" drivers is about equal to the five 10" drivers used in Magnetar's setup, so there should be plenty of dynamic range. Small side wings similar to Magnetar are probably a good idea as well, although I'd certainly cover the wings with several inches of recycled cotton fill, and possibly fill the semi-enclosed area between the woofers as well, to decrease standing waves, move the radiation pattern closer to a quasi-cardioid, and gain a bit of LF extension.
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Old 28th October 2007, 02:37 AM   #2504
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I think it can have good base for floor contact, get narrower, and go deeper, if done like this.
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Old 28th October 2007, 12:51 PM   #2505
dobias is offline dobias  United States
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Gentlemen;
Thank you for the responses. I now have my work cut out for me.
Since I have to buy a few more of the same woofers on eBay, that could take some time & patience. In the meanwhile, I'll rework what speakers I have into Salas' recommended arrangement.
I'll report back with my impression of the results.
In my former life I was an industrial troubleshooter & inventor. I had a vast array of test equipment & experts at my disposal, including sound meters. Now I'm reduced to trusting my ears!
dobias
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Old 28th October 2007, 01:22 PM   #2506
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Quote:
Originally posted by Lynn Olson

The radiating area of four 12" drivers is about equal to the five 10" drivers used in Magnetar's setup, so there should be plenty of dynamic range. Small side wings similar to Magnetar are probably a good idea as well, although I'd certainly cover the wings with several inches of recycled cotton fill, and possibly fill the semi-enclosed area between the woofers as well, to decrease standing waves, move the radiation pattern closer to a quasi-cardioid, and gain a bit of LF extension.

I think the 18 sound driver has too low of QTS. It may not go as low as you want without EQ, then if you boost the bass you have to look at it's limited xmax.

When using a pair of woofers I found two 21" drivers (.7 QTS) was good, but not as good as 5 or 6 high qts 10's. The tens sound free from the box, or more realistic if you keep live music sound as your perspective. The 12's may sound free too. Free- when listening to live music bass has a homogenize sound that floats through the room into your body without a sense of 'bass' hifi sound or reproduced sound through a loudspeaker system. This character is very difficult to achieve , even with bass horns. The dipoles will do it! I beleive the dipole radiation and lack of box colorations is the reason BUT you need to be able to move a lot of air too with out compression or distortion to distract your free feeling.

Are you saying you will use four 12's in the bass with one pair running up higher than the other? How would you crossover / drive this quad?

I also high pass my bass drivers- this lowers the movement in the bottom octave and increases the dynamic range. It really cleans things up. 50 cycles seem to be the best place with the 10's.
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Old 28th October 2007, 03:16 PM   #2507
dobias is offline dobias  United States
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Magnetar,
Perhaps I didn't explain my set up sufficiently;
Each Wharfedale speaker assembly starts with a full range 12 CS-AL, no crossover.
The first augmenting woofer has an air wound 4 mH coil in series for a 280 Hz low pass.
The second augmenting (& the future third) woofer add another 4 mH coil for a 140 Hz low pass.
I've tried using a subwoofer to reenforce the bass and it only muddied the sound.
Using the amplifier's bass boost seems to ruin the bass quality.
After I get the additional woofers & build the appropriate baffles, I'll try high passing the woofers as you suggest. I have no clue as to the woofer's Qts or xmax. Wharfedale's factory burned down many years ago destroying their records of the old speakers.
I now have augmenting Super 3 tweeters aimed up. I plan on adding second Super 3's aimed to the rear. They are high passed at 5,000 Hz with 3.9 mfd.
Thanks for your interest.
dobias
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Old 28th October 2007, 04:33 PM   #2508
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Lynn,

I don't get the attenuation of the rear wave creating a cardioid response. Attenuation changes toward monopole, but if you're talking about low bass attenuation is difficult. An OB radiation pattern changes from dipole toward cardioid using the baffle structure. The area of greatest null (sides for dipole, rear for cardiod) occurs where the front and rear waves have traveled the same distance.

Also note that I've found that changing the radiation pattern has less effect sonically than you'd think, however, it does seem to affect the "live" sound that Magnetar mentioned, and placement combined with radiation pattern plays a big role in my narrow room. Dipoles are more "live" with near side wall placement, but they need to be well out from the front wall (2m+). My U-baffles with a dispersion change toward cardioid sound more "live" if placement nearer the front wall is needed.

With OB the room really is an integral part of your speakers, so optimum results will require tailoring your baffles specifically for your room. The beauty of OB is that test baffles are easy and you can make changes on the fly. You can even get away with McGyver type stuff using duct tape and scrap wood.

It's going on 7 months now, so it's time for actual building to become part of rehab. The rest of the guys have no excuse for not actually having built anything during this thread. Hands on experience is so important with OB, and that's what has enabled Magnetar and myself to hone in on our goals.

Happy building,

John
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Old 28th October 2007, 07:04 PM   #2509
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Originally posted by agent.5
Any idea when the 15" "Super Boy" Tone Tubby will be available?
It is available now. And cheap it is.

http://www.svvintageamps.com/catalog...roducts_id=369
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Old 28th October 2007, 08:52 PM   #2510
dobias is offline dobias  United States
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Gentlemen;
After relocating woofer #2 from it's right angle mount at the rear to the front firing location, I'm amazed at the improvement. I have the woofers turned inward by 30 degrees, but find it difficult to say it's much better than having them parallel to the main baffle.
What's most satisfying is the present ability to use the amplifier's bass boost (5.5dB) without coloring
or smearing the bass. I haven't tried stuffing anything behind the woofers yet.
I'm still perplexed by the ability of the 'columns' I have at the sides of the main baffle to improve the soundstage.
They're 4 1/2" OD carpet rolls made of heavy cardboard. I had taken a 1 1/2" slice out of the sides to fit them over the main 16" x 32" baffle. That leaves over 1 3/8" of the column sticking out in the front as well as the back. I would expect that would present an obstacle for the sound waves traveling across the baffle. If that reduces the streamlining of the corner, I sure can't tell! Removing the cardboard tubes shows an immediate reduction in the soundstage. With the tubes in place I can hear the soundstage widen by a yard or more to the outside of the two speaker baffles.
Rather than facing a sidewall or an endwall, my TV is across a corner & the speakers are spaced out & to the sides of the TV view. I know that is unusual but I find the stereo imaging to be superb. I'm planning on having the 'proper' rounded corners on the final setup.... still, I can't help but wonder if there isn't some benefit with the columns as they now are.
dobias
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