sony buyout

[michiganpat]

Re: sony buyout

I'll create a thread for my crossover designs once I can get another frequency response measurement with the frame dampened.

I'm thinking of doing a TM, MTM, and a 12-driver line array.

could you use the TM xover for a MMTMM, and the MTM xover for an 8 driver array (with padding ajustments for the tweet) since the low pass impedance should the the same as the single and MTM configs?

[XtremeRevolution]

Re: sony buyout

could you use the TM xover for a MMTMM, and the MTM xover for an 8 driver array (with padding ajustments for the tweet) since the low pass impedance should the the same as the single and MTM configs?

I imagine you could by padding the tweeter more, but I haven't been designing crossovers long enough to say for sure. Sounds fine to me though. I first need to get some more comments on my second crossover design to see if it would work better than the first one. The tweeter is now more protected than last time, and I managed to raise the low impedance point of the tweeter from 3 ohms to 3.7ohms.

[XtremeRevolution]

Re: sony buyout

Looks like my line array crossover is just about done. 3rd revision finally looks good, and there's some room to play with the padding. I'll be ordering the parts and building it within the next month.

For now, I'm almost done with my TM design. Still working out a bit of fine tuning, but I believe I'm getting pretty close. I'm using this tweeter:

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=279-168

Its about the cheapest tweeter I can find that I can cross low enough, and its $8 per when you buy more than 4 (which I certainly will be). I'm working on some better phase alignment while keeping costs as low as possible. So far, its looking like a 2nd order on both tweeter and driver with heavy padding on the tweeter.

A bit more fine tuning when I get home tonight, and I should be able to post that. I'll be ordering those parts immediately after I get some expert approval on it.

Another note, I should post the T/S specs of the drivers as I measured them. They're a bit off from what r-carpenter posted in his consistency check. They're actually dead on what the driver lists in the product description. I believe I had an Fs of 78hz and an Re of 7.74hz.

[r-carpenter]

Re: sony buyout

A bit more data.
Foam pads were glued in on the underside of the frame.
Fist CSD was taken at 3 volts, which frankly is pushing the boundary for this little driver. No Foam pads.
Second CSD was taken at 1.2volts No foam pads.
Third CSD was taken with foam pads as well at 1.2 volts.
Mic was 20cm away. Between second and third CSD, nothing was changed but the driver.
After foam pads were applied, frequency response change slightly. Mainly, the change took place between 1k and 2k.
CSD shows minor ringing decreasing. Changes are very small.
I will also compare this driver surface and rear mounted.

[Sydney]

Re: sony buyout

Yes, 4th order electrical filter will surely roll it off. But we are going back to the summed up response, tweeter efficiency and capability. Hard to say at this point.
Let me throw an array of 12 on a piece of MDf, measure it and then we can see more clearly.
BTW Sydney, I think you should get a case of these. Cheap, good for experiments and if you don't like them, you'll never be short of an ashtray.

CSD shows minor ringing decreasing. Changes are very small.

Heck of "ring" there - lotta hang time
How sure are you that the frame is the source of the 5k issue?
That type of foam seems ineffective.
Perhaps try a denser dampening coating like a B rubber or silicone caulk on the frame?

RE: Ashtrays: I don't smoke tobacco; I just got some "novelty" ashtrays given to me at a yard sale so "I'm covered". ;)
( unless these drivers start being given away at yard sales in NYC )

My advanced age makes me stingy with my time; so I'm not inclined to approach a project that would require a lot of modification to a lot of drivers. Particularly with this large of a driver and the intrinsic CTC issue.
I wondered if an active crossover ( albeit more expensive ) would eliminate a lot of time/labor ( in driver mod work ) allow a lower xover point and keep the passband below the ringing frequency.

[r-carpenter]

Re: sony buyout

Heck of "ring" there - lotta hang time
How sure are you that the frame is the source of the 5k issue?
That type of foam seems ineffective.
Perhaps try a denser dampening coating like a B rubber or silicone caulk on the frame?

I've made a conclusion that 5k ringing is a diafragm, not frame. Relates to the size of the cone as well.
Foam was meant to negate the reflections between wide wide frame wings and rear of the diaphragm. It worked somewhat.
Frame rings as well and will benefit from silicone or B Rubber but that will be done later. Look at the voltage I am exciting the driver with. I doubt very much that it'll see 3volts or even 1.2v in the array. And so the fundamental output of our little pin cushion driver will be progressively higher in relation to distortion, ringing and so on. I should say it in reverse. The problems of each individual driver will be progressively less in relation to the fundamental at given voltage.

Active is better, sure.
My opinion is that CTC issue is overstated and in subjective listening of line arrays is less important because of stable vertical image. But, that's just my opinion.

[Sydney]

Re: sony buyout

I've made a conclusion that 5k ringing is a diafragm, not frame.

I wondered if it had a breakup pattern similar to a Chladni plate that could be addressed by cone mods.
The CSD looked like the 5Khz ridge was there regardless of level albeit decaying faster.
The foam seemed to have a ridge @ 4Khz however.

I respect your opinion...
I've held concern for the issue of CTC since I first heard "sound columns" in the 60's and before the extensive study on such consideration that came with the resurgence of arrays in the Pro world.
It is related to the same basic Ka issue that has to be dealt with in simpler multi-driver configuration ( like MTM ). A 5" typically rolls from about 2100Hz ( -3db ) and 3200Hz ( -6db ).
I've studied the numerous efforts of those published in SB as far back as the "Linear Array Chronicles" and "Focused Arrays" and noted how they rejected drivers that were too large. Don Keele's paper:
Implementation of Straight-Line and Flat-Panel Constant Beamwidth Transducer (CBT) Loudspeaker Arrays Using Signal Delays has caught my focus at this time.

* Apologizes if I'm being the "flatulent elephant" in this thread with my diversions.
I'll quietly observe and let you carry on .
Syd

[r-carpenter]

Re: sony buyout

Mutual Sydney. Pleas do not stop expressing concerns and citing articles and papers. There isn't a sea of info on line arrays and every bit and opinion is very useful. As I mentioned before, arrays are hard to build for DIY, harder to measure and even harder to model.
Me been a lucky sob and having a woodworking shop handy, I'll often resort to just simply making project and working with it till the end (scrap in the dumpster or glory awaits).

[r-carpenter]

Re: sony buyout

so, as you can see, I've build prototypes open baffle lines with 12 drivers and space left for a tweeter. This coming week will be very busy so I may sporadically continue during but most likely will get back to it by the weekend.

[[email protected]]

Re: sony buyout

nice work mr. carpenter. those drivers look rather nice with the roundover.

[XtremeRevolution]

Re: sony buyout

Ok, so you have to tell me how you made that. Just a router and a circle jig? That looks amazing. What thickness material did you use? I'm going for exactly the same look.

[[email protected]]

Re: sony buyout

appears to be 3/4 with 1/2 inch roundover.

[r-carpenter]

Re: sony buyout

10"x74"x1" Ranger board (MDF variety)
CTC 5.25
Cutout diameter 4.7/8
Round over bit 5/8 if I remember correctly.
Circle jig and a router. Bits used: Onsrud 1/4" spiral down cutting.

http://ctsaw.com/cnc/cnc-onsrud-57-200.jsp

Flush trim to clean up the tit after center puck would fall out.

http://ctsaw.com/store/html-amana/at_47090.php

And then a round over

http://ctsaw.com/store/html-amana/at_49492.php

HTH

[nottaway]

Re: sony buyout

How would these do in a center channel channel? Maybe a WWTWW wired up for 8ohms? Anyone eyeing a crossover for something like this? My brother wants a center built and this would be a fun multiple driver project...... He would have to lay it horizontal so would the higher crossover of this driver knock it out of contention for something like this? Thoughts? Worth trying?

[XtremeRevolution]

Re: sony buyout

How would these do in a center channel channel? Maybe a WWTWW wired up for 8ohms? Anyone eyeing a crossover for something like this? My brother wants a center built and this would be a fun multiple driver project...... He would have to lay it horizontal so would the higher crossover of this driver knock it out of contention for something like this? Thoughts? Worth trying?

I'm guessing a new crossover will need to be built, or you'll need to pad the tweeter a bit more. It would be something you'd have to buy a few extra resistors to experiment with.