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Old 21st November 2009, 09:02 PM   #1
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Default H-frame woofer ?

I plan to make two H-frame dipole woofer for music listening.
On my plan there are four Peerless 830669 drivers in both dipoles, total 8.
Crossover frequency is somewhere 80-100Hz and I use active crossover filter.
Height of H-frame will be 1,5 m (60 inch) and total width will be 34cm (13,3 inch) and deep of H-frame will be 40 cm (15,7 inch). Does anybody have experience of this kind of dipole? Do you think that it’s ok if I put drivers one on top of other, without any extra spaces?
Is that size ok? I don’t have room to make very wide H-frame (max width maybe 50-60cm (20-23 inch) but I have room to make deeper and higher. How deep is optimal in my case? I already thank you for answer!
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Old 1st December 2009, 01:40 AM   #2
tinitus is offline tinitus  Europe
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Im no expert
Actually I have never built a "sub"

Drawing shows a bit about how I think I would build what you suggest
I dont know if there really should be baffles between each woofer, but I would consider it
Somehow I reckon it would result in better more equal loading of woofers
And I have shown them with curves cut out in each
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Old 1st December 2009, 01:05 PM   #3
Rudolf is offline Rudolf  Germany
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Quote:
Originally Posted by pieskapov View Post
Do you think that it’s ok if I put drivers one on top of other, without any extra spaces?
It is perfectly OK to stack them. Don't try to isolate one from the other. Make them one rigid column. Since all drivers move in the same direction, you need to look for the resulting momentum. Don't try to isolate that column from the floor either. Give it a firm contact to the floor. And put as much weight on top as you can afford. Some 33x33 cm tiles or a terrace slab will come in nicely. This will most effectively keep the column from rocking.

You don't need to 'focus' that row of drivers to the listening position. With the shortest wavelength being 3 m plus, moving any frame from 5% of that back or forth doesn't change anything.

Dividing the column into compartments doesn't change anything WRT the acoustics, but it will keep the side walls from resonating. So it is strongly recommended.

Quote:
Is that size ok? I don’t have room to make very wide H-frame (max width maybe 50-60cm (20-23 inch) but I have room to make deeper and higher. How deep is optimal in my case? I already thank you for answer!
Making the frames wider and higher will lower the driver Fs a bit and will raise the efficiency. If efficiency is a problem (which I doubt), you may consider it.

Making the frame deeper will lower the driver Fs too (and to a larger extent), but will do the same to the frame resonance. It depends on the order of your crossover, how feasable that would be. May be someone could do a simulation with MJKs H baffle worksheet for you.

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Old 1st December 2009, 01:37 PM   #4
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Quote:
Originally Posted by Rudolf View Post
Don't try to isolate that column from the floor either. Give it a firm contact to the floor. And put as much weight on top as you can afford. Some 33x33 cm tiles or a terrace slab will come in nicely. This will most effectively keep the column from rocking.

Rudolf
Well, there is often a misunderstanding of what decoupling a loudspeaker from the floor means. If you put the resulting resonant frequency in the right interval you may gain in sound quality as the speaker then acts as a high pass filter and frequencies lower than this tuned frequency have less impact, they can´t excite floor resonances as easily.

My subs weigh more than 200 lbs each and are decoupled from the concrete floor by appropriate elastic devices called The SD feet. The gain in the clarity of bass notes is significant. The "spikes brigade" has a mental advantage in the the long "true" assumption that common sense says that speakers should not be able to "rock" back and forth. But when playing a decoupled speaker is often standing more still than a spiked one, provided that the decoupling is made in an appropriate way. Thus, a decoupled speaker can produce less Doppler distortion as well, quite contrary to what a maybe not that educated reviewer believed.

.http://www.sonicdesign.se/sdfeet.html



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Last edited by The golden mean; 1st December 2009 at 01:50 PM. Reason: Correcting grammar
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Old 6th December 2009, 10:41 AM   #5
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Default Thanks everybody!

They are now ready without drivers.
High is 150 cm, deep is 30 cm and total width is 45,5cm.
Material is wood plate, thickness is 28 mm.
There goes 4 pcs. Peerless SLS 12” 830669 drivers to both dipoles.
I think that I make the "roof" by concrete slab, so same time its increase weight of tower and it’s easy to move separately
When the varnish is dry I can put drivers in and made some measurements.
If they don’t work nice they goes next Midsummer festival bonfire…
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Old 8th December 2009, 12:47 AM   #6
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Hi There: What is your plan for placement of the two H-Frame towers in the room? Awaiting your listening experience. .... regards Michael
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Old 9th December 2009, 08:51 PM   #7
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Hi! They are now 242cm (7.9 ft) from front wall. That’s actually only place where I can place them now or otherwise I must turn everything vice versa. I don’t yet have any equalizer so now I can measure only draft response. I think I need some very adjustable equalizer for both dipole and power amplifiers of cource . One possibility is maybe Behringer DCX2496 Ultradrive Pro and power amplifier one or two Behringer A500. Regards Pies
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Old 30th December 2009, 07:01 PM   #8
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Default All together...

In the same time I made new main speakers. There is everything in same picture.
For dipole bass I also need low-pass filter and dipole and room equalization.
Do you have any experience from Behringer DCX2496 Ultra-Drive or Behringer DEQ2496 Ultra-Curve or DBX DriveRack PA+ or DBX DriveRack PX or some else? Thanks!
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Old 31st December 2009, 12:38 AM   #9
CLS is offline CLS  Taiwan
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Hi tinitus,

Interesting and nice looking idea of that H tower

However I think it's not necessary to make a curvy alignment. At the frequencies (wavelenghts) which the sub is working, air is pumped in a big scale and the waves are filling the room. So it doesn't have to 'focus' at the listener. I suppose you know that.

Cool looking though.
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