@ CharlieLaub
Thanx for the driver link etc
How do they make them for that $ ?
The "required" 6-dB-per-octave boost is just on paper etc, as every room is different ! Same thing applies to the Linkwitz trandform closed box 12dB boost, etc etc etc
Hope the 100Hz - 250Hz anomolies don't spoil things
Thanx for the driver link etc
How do they make them for that $ ?
The "required" 6-dB-per-octave boost is just on paper etc, as every room is different ! Same thing applies to the Linkwitz trandform closed box 12dB boost, etc etc etc
Hope the 100Hz - 250Hz anomolies don't spoil things
@ CharlieLaub
Thanx for the driver link etc
How do they make them for that $ ?
The "required" 6-dB-per-octave boost is just on paper etc, as every room is different ! Same thing applies to the Linkwitz trandform closed box 12dB boost, etc etc etc
Hope the 100Hz - 250Hz anomolies don't spoil things
Yeah, what you get for your $20 pretty amazing! It's (of course) a stamped frame driver, and the packaging is quite lean. A couple of mine arrived with minor dents in the lip of the frame where you mount the driver. Luckily these straightened right out when I screwed the drivers down. But seeing how the TS parameters were all very close to spec I am very happy with these. Not sure if the MFG Xmax value is really accurate, since I could not test it. The suspension quickly stiffens as the cone moves away from the rest position and there is definitely NOT any extra excursion capability. I am even questioning whether the Xmax is really a peak-to-peak number.
I'm not including any kind of room response corrections in the EQ. It's just what is needed to flatten out the free-field response model prediction. The classic dipole correction is a 6dB/oct boost below the first dipole peak...
Since I am planning to cross over to the main speakers around 80-100Hz the stuff going on between 100Hz and 250Hz is not all that important. I would not want to try to include that in the sub's passband anyway.
Looks good on paper at least. I haven't sat down to calculate the potential output SPL, but I don't think it will be all that high. The dipole arrangement causes quite a lot of SPL loss at lower frequencies. For instance I need to apply about 9dB of electronic boost to flatten the response. One way to think of it is that the 97dB@2.83v sensitivity is reduced to about 88dB. Also, even with 12 drivers the total displacement may not be enough to maintain high SPL at the lowest frequencies. Getting exact numbers for this is not really high on my list right now.
Well it's sitting in my garage running full range with no corrections. I only got it working for the first time yesterday. It's a little early to give any listening impressions... But it was definitely not an expensive project given the size and number of drivers and it has some interesting design attributes.
As for your question of "is it more effective than..." - that would involve quite a bit of a subjectivity. I can only suggest that you do some reading/research into the differences between vented, transmission line, open baffle, and dipole systems and make up your own mind about what would best suit your needs.
The sub cabinet is five feet wide and will sit directly in between the two satellites, oriented horizontally. Because there are 12 drivers, sound is eminating all along the length of the cabinet. I am doubtful that there will be any integration problems like you would for a single driver sub, especially one not centrally located, e.g. in a corner, etc.
The main speakers are an update of this prototype open baffle design that I demoed last year at the NorCal DIY Audio group meeting:
http://www.diyaudio.com/forums/multi-way/263597-mid-size-open-baffle-plus-fin-design-prototype.html
http://www.diyaudio.com/forums/multi-way/263597-mid-size-open-baffle-plus-fin-design-prototype.html
Quick update: since my last posted I have manage to accomplish... exactly nothing, except to drag this monster into my house and place in between the open baffle speakers.... I'm quickly realizing that I may not actually be able to bring this system to Burning Amp after all. It fits in my vehicles, but doesn't leave room for much anything else.
Also, I still have to do a bunch of crossover work, build the amps and computer into the sub cabinet, etc, etc, etc. So even if I wanted to I just might not have enough time. I'll focus on my other project(s) for now and maybe leave this one for next year's show.
Also, I still have to do a bunch of crossover work, build the amps and computer into the sub cabinet, etc, etc, etc. So even if I wanted to I just might not have enough time. I'll focus on my other project(s) for now and maybe leave this one for next year's show.
I haven't hooked it up yet in the horizontal orientation. I did some testing when it was oriented vertically (just after I finished building it), and there was some minor vibration but gravity was not helping. I believe that Siegfried Linkwitz discovered that you just cannot get 100% force cancellation, and I will likely find the same. Hopefully it's close to that, however.
@normanbates: Into each opening to the front or rear there is the front of one driver's cone and the back of the adjacent driver's cone. These are moving in opposite directions, e.g. both moving into the chamber or out of the chamber at the same time.
Charlie,
Have you seen Monte Kay's dipole sub woofers? There are some performance numbers on his site that give insight to some of the other questions on the thread.
http://http://www.mfk-projects.com/Home_Theatre/theatre_woofer.html
Have you seen Monte Kay's dipole sub woofers? There are some performance numbers on his site that give insight to some of the other questions on the thread.
http://http://www.mfk-projects.com/Home_Theatre/theatre_woofer.html
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Nice. Wiring them to be force self canceling over six sets will really help reduce mechanical vibration. Push pull reduces second order distortion. Slot loading boosts efficiency by a few dB. I am guessing you may get closer to 100dB sensitivity but as it is dipole - falls off faster with distance than monopole. Looking forward to results.
It's not the wiring that provides the force-cancellation....it's the physical configuration/layout.
In this case, all the drivers are orientated the same way so adjacent drivers are wired such that one cone moves away from the magnet and one cone moves toward the magnet......which achieves a certain level of even-order distortion reduction.
The "ripole effect" here is probably minimal since the cavities are still somewhat large....relatively speaking.
It's a neat project. Be careful of your back when lifting/moving Charlie.
Cheers,
Dave.
In this case, all the drivers are orientated the same way so adjacent drivers are wired such that one cone moves away from the magnet and one cone moves toward the magnet......which achieves a certain level of even-order distortion reduction.
The "ripole effect" here is probably minimal since the cavities are still somewhat large....relatively speaking.
It's a neat project. Be careful of your back when lifting/moving Charlie.
Cheers,
Dave.
Link is dead. I did see a writeup on those floor to ceiling monsters, but it's been awhile.
Just taking into account the wiring and number of drivers, the sensitivity should be 97dB@1m for a 2.83 v input.
I believe that the slot loading will actually reduce the efficiency a bit, although I have tried to keep the open area per driver as high as I could. It's about 0.75*Sd per driver.
It's not the wiring that provides the force-cancellation....it's the physical configuration/layout.
In this case, all the drivers are orientated the same way so adjacent drivers are wired such that one cone moves away from the magnet and one cone moves toward the magnet......which achieves a certain level of even-order distortion reduction.
The "ripole effect" here is probably minimal since the cavities are still somewhat large....relatively speaking.
It's a neat project. Be careful of your back when lifting/moving Charlie.
Cheers,
Dave.
You are right about the back! I didn't even trust that my wife and I could safely carry it, so I went out and bought a hand truck. Carting it around it very easy now, but getting it into and out of my vehicle is still looking like a challenge. If only I had one of those minivans in which all the seats fold down flat... or a moving van! I honestly thought about renting such a thing so that I could cart this and a bunch of my other stuff over to Burning Amp, but decided that it would be best to wait until I really had the system working and after some listening time, etc. So maybe next year.
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