searched enough drivers in India......conti...

[sumit]

Hi guys...i am back

this time with a woofer for OB application....or atleast i tried to make a suitable one for OB app. .... will keep on improving and pasting images and TSPs.....

Initial results are very encouraging ...pictures for u guys to suggest and comment on...

thanks for any suggestion....

http://i130.photobucket.com/albums/p...7/DSCI0025.jpg
http://i130.photobucket.com/albums/p...7/DSCI0024.jpg
http://i130.photobucket.com/albums/p.../DSCI00251.jpg
http://i130.photobucket.com/albums/p...7/DSCI0082.jpg
http://i130.photobucket.com/albums/p...7/DSCI0092.jpg
http://i130.photobucket.com/albums/p...7/DSCI0028.jpg

Fs = 30Hz
Qes = 1.38 ( can be varried in the next model from .7 to 1.8 with very little effort)
Qms = 9.399
Xmax lin = 10mm one way
Vas = 4.545
Other features:

Aluminum shorting ring + shorting stud
dual layer insulated pole piece
cast aluminum basket
uniform mag. field + T pole piece

thanks
Sumit

[Sanj1ay]

Hey Sumit,

Welcome Back!

Nice to see ur creation.
However.. I have a few questions:
1. What is the "Aluminum shorting ring + shorting stud" for in a subwoofer applcation? Are you intending to take it into the kHz range?

2. "dual layer insulated pole piece"
a. what's a "dual layer insulated pole piece"? I guess maybe i am missing a patent.. if so.. please give me the necessary links.
b. again .. maybe my ignorance.. but why is the pole insulated?.. and from what?

3. "uniform mag. field + T pole piece" - again a new term for me.. pls explain what "uniform mag. field" and "T pole piece" means.

About the Thiel/Small Parameters.. What is the target bandwidth of this driver? The qm is so high that it would take a HUGE cab to make it sound non sloppy if used in a ported cab. i guess the only way might be to use it in about a 100liter+ sealed cab.

[sumit]

Ok let me ans one at a time...

"1. What is the "Aluminum shorting ring + shorting stud" for in a subwoofer applcation? Are you intending to take it into the kHz range?"

The shorting ring is to short the eddy currents flowing in the pole piece. The ring is a bit away from the t pole , so to short out any eddy current in the visinity of the T pole ( where the coil interacts with the pole ) piece a aluminum stud is fitted. I am trying to design a woofer and not a subwoofer and that too for an Open Baffel application. When i start designing a motor i always keep in mind that this motor should also go with a 10" 8" also, so bandwidth is always a factor. Though copper sleve would have to be used if performance in range Khz required(but not with a 12" woofer ( bandwidth in mind 25Hz to 600Hz +-0dB)

"2. "dual layer insulated pole piece"
a. what's a "dual layer insulated pole piece"? I guess maybe i am missing a patent.. if so.. please give me the necessary links.
b. again .. maybe my ignorance.. but why is the pole insulated?.. and from what?"

- A dual layer pole piece is a pole piece made by joining two cylindrical pieces together using non conductive glue. This helps the T-pole to be electrically isolated and insulated from the rest of the pole and hence eddy currents. their is a link but i don't remember now.... somewhere in IEEE....and also an expired pattent...

3. "uniform mag. field + T pole piece" - again a new term for me.. pls explain what "uniform mag. field" and "T pole piece" means.

A conventional ferrite magnet's field is not uniform.So it creates a non uniform ( though little ) field around the top plate and pole piece junction. To improve this i used multiple magnets in a circular pattern. T pole is quite common, please google to find out more......

"About the Thiel/Small Parameters.. What is the target bandwidth of this driver? The qm is so high that it would take a HUGE cab to make it sound non sloppy if used in a ported cab. i guess the only way might be to use it in about a 100liter+ sealed cab."

BW - 25Hz to 600Hz or so +/- 0db
The woofer is optimised for OB ....Qes = 1.38 in a closed or vented box would result in a peaky or very peaky response.......in a 6cuft closed box 4bB at 50Hz was observed.

Hope i was able to ans all u wanted to know.....

rgds
Sumit

[Sanj1ay]

Hey Sumit,

Being focused on Pro Audio, where the priorities are high efficiency & power handling, and thereby higher spl.. we tend to forget "OB"!!

As for dual layer pole - I haven't come across this being applied in pro-audio drivers - i guess the obvious trade-off in this would be a slight loss of magnet flux in the coil gap..

"T-Pole": T-Yoke is what i was used to! Like spider/damper or frame/basket/chassis. Names!

What's the BL & Efficiency ? I guess around 10Tm & 0.25% ?

Cheers!
Sanjay

[sumit]

"As for dual layer pole - I haven't come across this being applied in pro-audio drivers - i guess the obvious trade-off in this would be a slight loss of magnet flux in the coil gap.." EXACTLY

""T-Pole": T-Yoke is what i was used to! Like spider/damper or frame/basket/chassis. Names!" YUP---names

What's the BL & Efficiency ? I guess around 10Tm & 0.25% ?


Eff - 85dB . BL - abt 9.134Tm

Hey will u be interested in a NIB 15" proaudio driver? I actually imported a few NIBs and was interested in making a motor for a pro audio driver...just to see how it goes......as this would be my first pro-audio driver u can be a great help.....if u r willing that is....cost is not the point here just to see weather a resoneanle driver can be made using these magnets........JFF


rgds
Sumit

[Sanj1ay]

I am already using ND magnets in some of my drivers. I am sure you could make a decent motor using them, but might be difficult finding a magnetizer in delhi for them.

You are most welcome for any help that you may need for your pro-drivers. I've been using Forged T-Yokes, muller & malaysian cones (including carbon-fibre composites) & all kinds of VC designs - Edgewound Copper & CCAR, inside-outside etc.

When you want to touch the extremes in efficiency & power-handling (which are very important in pro-audio), then the little things add up to make a diff.