Modifications to the RTA 15TL

Pegaso55 · April 2015

Good morning, I'm writing from Italy. I've a pair of RTA 15 TL since 1990, I've upgrated the old tweeter SL 3000 with the new RD 0198-1. Now I'm interested to upgrading
the crossover how can I find the schematic of Decato xover?
Than You

westmassguy · April 2015

http://forum.polkaudio.com/discussion/48075/modifications-to-the-rta-15tl/p1

Parts list:
2 x 13.5uF caps
2 x 12uF caps
2 x 10uF caps
2 x 1.75 mH, 16 awg inductors
2 x 0.22 mH, 19 awg inductors
2 x 2.7 ohm resistors
2 x 0.5 ohm resistors

Pegaso55 · April 2015

Thank You very much Westmassguy

... and Happy Easter tu all the Forum

Steve

westmassguy · April 2015

You're welcome, and Happy Easter to you as well.

Pegaso55 · April 2015

Dear all I've a question who may know. I find a Munford Supreme but non with the exactly capacity. Can I use 1 X 10 UF caps + 1X1.8 uF for the 12Uf Cap and 1X10 uF + 3.3 uF for the 13.5 uF in this crossover? Also can I leave in place and use the original 1.75 mH? I will change only the 022mH with a new one. Thank You very Much

westmassguy · April 2015

Pegaso55 wrote: »

Dear all I've a question who may know. I find a Munford Supreme but non with the exactly capacity. Can I use 1 X 10 UF caps + 1X1.8 uF for the 12Uf Cap and 1X10 uF + 3.3 uF for the 13.5 uF in this crossover? Also can I leave in place and use the original 1.75 mH? I will change only the 022mH with a new one. Thank You very Much

It's always best practice to use the exact value Capacitor when possible. If you must combine 2 or more Capacitors to make up the required value, the Capacitors should be close in value. For the 12uf, a 5.6uf and a 6.2uf or four 3ufs will get you there. For the 13.5uf, two 6.8uf caps would be better.
The 1.75MH inductor must be changed. Decato went from the stock #18 gauge, to #16 gauge. This affects the crossover frequency, and the SPL of the woofers.

Pegaso55 · April 2015

Grazie :-) thank you very much
Steve

Pegaso55 · April 2015

Dear Westmassguy before start to assembly the xover I've a last question, for the resistor (I find 0.47 ohm instead 0.5) is better 10w or 5 w ? Or they have the same effect?
I thank you in advance
Steve

westmassguy · April 2015

Pegaso55 wrote: »

Dear Westmassguy before start to assembly the xover I've a last question, for the resistor (I find 0.47 ohm instead 0.5) is better 10w or 5 w ? Or they have the same effect?
I thank you in advance
Steve

.47 ohm 10 watt

Pegaso55 · April 2015

Thank You ... :-)

Pegaso55 · May 2015

First Step ... Done! :-)
But I do not know why I can not publish the photo :-)

Pegaso55 · May 2015

[img][/img]

Recap RTA 15 TL ... First Step :-)

westmassguy · May 2015

All point to point, very nice. Two things, the type of bolt you used to secure the large Inductor, and the Sandcast resistors. If the bolt is stainless steel you're good. If its regular steel, you've increased the value of the inductor. I would have used Mills, or Mundorf MOX Resistors.

decato · May 2015

I'm not sure if I'm seeing this correctly, but do you have the 0.5 ohm resistor in series with the 1.75 mH inductor? If so, that's incorrect. The resistor is in series with only the tweeter circuit.

-- Nevermind, I see it...

Pegaso55 · May 2015

[img][/img]

The 0.5 ohm resistor is in series with only the tweeter circuit.
Before closing I covered the xover with a thin layer of soundproofing.
Now the sound is incredible ... amazing ... wonderful
I want to thank all of you for the advice
Thanks a lot from Italy

westmassguy · May 2015

very nice

Fanatic · July 2016

westmassguy wrote: »

http://forum.polkaudio.com/discussion/48075/modifications-to-the-rta-15tl/p1

Parts list:
2 x 13.5uF caps
2 x 12uF caps
2 x 10uF caps
2 x 1.75 mH, 16 awg inductors
2 x 0.22 mH, 19 awg inductors
2 x 2.7 ohm resistors
2 x 0.5 ohm resistors

If i would do as the picture states, i would end up with the 13500uf on the tweeter side. C2 and C3 is switched in the drawing. Or is it just my late -92 RTA15-TL thats different?

westmassguy · July 2016

Did Polk switch to a smaller, square circuit board on your 15tls? Trace the circuit. The 13.5uf is the shunt in the low pass circuit.

Fanatic · July 2016

westmassguy wrote: »

Did Polk switch to a smaller, square circuit board on your 15tls? Trace the circuit. The 13.5uf is the shunt in the low pass circuit.

Yes they have the small square board, the shunt is named C2 on this one.

westmassguy · July 2016

There's your answer. Just carefully trace it out. Do them one at a time, so you can refer back to the original.
The last Decato Mod I did, had the old round circuit boards:

boston1450 · July 2016

Hey. Those look fimiliar

maybe one day soon i will put em in & see how they sound. Im a slacker

westmassguy · July 2016

Yeah you think? Rat Bastage, get'em in already..............

boston1450 · July 2016

Ive been painting for 2 days straight & im outside sweating like a pig in heat. Im so backed up between work & the house. If i live to see it all done i will be a happy man

westmassguy · July 2016

It's Wicked Hawt"....
Try working with a house full of non-English speaking relatives for two weeks.

Fanatic · July 2016

westmassguy wrote: »

It's Wicked Hawt"....
Try working with a house full of non-English speaking relatives for two weeks.

Try restoring a couple of Polk speakers when you live in Sweden.

Those crossovers look really neat, thats the look i'm aiming for.

westmassguy · July 2016

There should be some suppliers in the EU for Inductors that match the specs on the Madisounds, Jantzen is in Denmark. Clarity Caps are made in Wales, so there should be a supplier in the UK at least. Vishay/Mills is International, so their Resistors should be available. The Nylon Standoffs I get off eBay, and the riser board is Masonite.

Fanatic · July 2016

Well, now the speakers are back in action with redone x-overs and new tweeters. The short listeningsession iv'e done is promising!

This is how the X-overs look redone:

westmassguy · July 2016

Looks great. Did you remember to reverse polarity on the tweeter leads?

Fanatic · July 2016

westmassguy wrote: »

Looks great. Did you remember to reverse polarity on the tweeter leads?

Of course!

Did also replace all the internal wires, same gauge but new single core wire. Stranded wires tend to give a bit more resistance.

decato · July 2016

I'm really glad that everyone likes the sound of this modified crossover. I still have the pair that I modified back in late 2006/early 2007. Nearly 10 years later, they still sound good to me.

Modifications to the RTA 15TL

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