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Author Topic: SPL TD1 Recondition & Improvements  (Read 5291 times)

Jeremy Young

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Re: SPL TD1 Recondition & Improvements
« Reply #80 on: January 22, 2019, 01:59:02 pm »

Looks great Nathan nice work, thanks for sharing the "after" side. 
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drew gandy

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Re: SPL TD1 Recondition & Improvements
« Reply #81 on: January 28, 2019, 02:30:45 pm »

Moar pics.

As you can see, heavily reinforced inside to heft the 130lb speaker safely.

Nathan, nice job.  And wouldn't you know it, now that you're finished, I just came across some details about the brackets.
Of course, I think you got it figured out.  I especially like the extra brace piece inside for the pole cup. 

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drew gandy

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Re: SPL TD1 Recondition & Improvements
« Reply #82 on: January 28, 2019, 02:41:01 pm »

Here's a hand drawn schematic of the original TD-1 crossover.   The astute viewer will notice that there is an interesting series resistor for the woofers.  You will also probably note (under your breath) that we don't know the resistance of the inductors. 

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John Halliburton

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Re: SPL TD1 Recondition & Improvements
« Reply #83 on: January 29, 2019, 08:22:11 am »

Here's a hand drawn schematic of the original TD-1 crossover.   The astute viewer will notice that there is an interesting series resistor for the woofers.  You will also probably note (under your breath) that we don't know the resistance of the inductors. 


DCR=0.185ohm

It's a stock Madisound 15ga laminate steel core coil.

I've had to replace some of the 8ohm resistors and 16uf caps in the midrange section, as the way we originally mounted them was too close, and no heat sink on that resistor.   Increase the power handling of the resistor, mount on a piece of aluminum L channel, and  space it and cap further apart.  All's good.

Best regards,

John
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drew gandy

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Re: SPL TD1 Recondition & Improvements
« Reply #84 on: January 30, 2019, 12:16:08 pm »

DCR=0.185ohm

It's a stock Madisound 15ga laminate steel core coil.
Thanks John.  For the folks at home, this is the resistance of the "big" 3.3mH coil in the woofer section.  Reading the schematic we are still blind about the resistance of the other coils.  Not that this is something too challenging.  It's simply an element to be considered when modeling etc a passive crossover. 

For instance, if you build a crossover from the schematic, the added resistance of a coil may or may not make a difference in the result.  Since the resistance of this coil is fairly low in comparison to the resistor that is also in series, I wouldn't think it's resistance is significant in the response.  But it also makes me wonder if lower distortion could be had using an air coil with a resistance of 1.2ohms in place  of this iron core AND resistor...   ;D 

(the air core would probably cost many times as much as the iron core and distortion from the coil in this band is probably minimal.  In fact, the unity type of loading causes an acoustic low pass filter for this band so harmonic distortion is filtered a little for free.) 

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I've had to replace some of the 8ohm resistors and 16uf caps in the midrange section, as the way we originally mounted them was too close, and no heat sink on that resistor.   Increase the power handling of the resistor, mount on a piece of aluminum L channel, and  space it and cap further apart.  All's good.
I remember glueing the big sand resistors to a piece of angle aluminum back when I was working with you.  But I believe later ones had a much smaller resistor that actually mounted to a heatsink? 
 
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