Crossover rebuild for RTA15TL

HBombToo
HBombToo Posts: 5,256
edited April 2004 in Speakers
I just received the crossover from our friend Ken at Polk and the circuit is very straight forward. I would like to rebuild the crossover with all new high end resistors, capacitors and Inductors and here are the specifications:

Tweeter
R1 2 Ohms ~5 Watts
Note: the diagram shows 1.5 Ohm in the earlier models but Polk changed to a 2 Ohm. The resistor is inline with the Tweeter and has a cap in parallel(C2).

C2 12uF 50V NP in line with the tweeter.
L2 .4 mH 22ga across the tweeter.
C3 12uF in line with tweeter.

a Polyswitch is in line with the tweeter and I'm going to eliminate it but wanted to mention it for this portion of the network.

Mid Drivers 4 and they are arranged as 2(parallel) in series with 2(parallel)

L1 1.75mH 18ga in line with the array.
C1 20uF 50V NP across the array

So all in all a pretty straight forward 2 way design. I would really appreciate all of your opinions on replacement parts prior to my order.

Thanks in advance

HBomb
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Post edited by HBombToo on
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Comments

  • phoneisbusy
    phoneisbusy Posts: 867
    edited April 2004
    Polyswitches are suppose to function like fuses right? Just learning about crossovers and design.

    Sounds like fun.

    Good luck

    Dave
    Time is the best teacher. Unfortunately it kills all its students.
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  • dorokusai
    dorokusai Posts: 25,577
    edited April 2004
    I have sourced all my inductors from North Creek Loudspeakers. North Creek They had the best prices in my searches, and were able to custom wind, not stock pull, closer to spec than Michael Percy Audio and a bunch of others for the replacements on my 1C's.

    As far as the other parts, I would just go www.soniccraft.com Jeff is cheaper than MPA, and always nice on the phone....what else do you need. I spec'd out my whole crossover, just haven't made the purchase.

    It's easy, just expect much larger parts, and a creative engineering head...which I know you have. Get you hot glue gun ready.

    CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint.
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  • jcaut
    jcaut Posts: 1,849
    edited April 2004
    Personally I would just upgrade the caps and resistors, and leave the stock inductors. Well, I take that back: If the inductor on the tweeter network is NOT an air core, I would change that too. That would mostly avoid the problem of dealing with much larger-than-stock parts. I've experimented with everything from cheap laminated core inductors up to the high $$ foil types, and concluded that I just can't hear a difference. The difference in caps and resistors is much more apparent, IMO. Switching to Mills resistors and the Sonicaps from Sonicraft would give the most "bang for the buck", again, IMO.

    If you change that 1.75 mH on the woofer network to an air core---assuming the original is iron core--- you'll need to try and keep the DCR as close as possible to the original. That can be difficult because obviously you're dealing with a lot more wire on an air-core. You'd probably have to go with 12ga wire or foil.

    Changing the DCR is bad because it affects Qes, sensitivity, bandwidth of the filter, etc.. But I doubt I'm telling you anything you don't already know..:)

    Jason
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  • HBombToo
    HBombToo Posts: 5,256
    edited April 2004
    Originally posted by jcaut

    If you change that 1.75 mH on the woofer network to an air core---assuming the original is iron core--- you'll need to try and keep the DCR as close as possible to the original. That can be difficult because obviously you're dealing with a lot more wire on an air-core. You'd probably have to go with 12ga wire or foil.

    Changing the DCR is bad because it affects Qes, sensitivity, bandwidth of the filter, etc.. But I doubt I'm telling you anything you don't already know..:)

    Jason

    I hear ya Jason and the whole process scares the crap out of me because I never did it before but then again thats the point. I'm going to leave the original circuit intact and build an entirely seperate network for play and experimentation. You nailed it regarding the inductors but will be the most fun IMO.

    Thanks for the Link Mark... When you posted the link for the inductors I was beginning to get frustrated but you relit the flame.

    Thanks
    HBomb
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  • HBombToo
    HBombToo Posts: 5,256
    edited April 2004
    Originally posted by jcaut
    You'd probably have to go with 12ga wire or foil.

    Changing the DCR is bad because it affects Qes, sensitivity, bandwidth of the filter, etc.. But I doubt I'm telling you anything you don't already know..:)

    Jason

    I was actually considereng 8ga at best but I'll settle for 10ga depening on cost and size.

    Doro and Tour both listened to the 15's and both confirmed the mids were/are weak. I figure I'll get the biggest bang for the buck changing out the inductors.

    I don't believe Polk publishes all the specs to the general public; however if Polk will provide engineering advice and support, Qes could come into play. My thoughts are that by decreasing the DCR the sensitivity should increase for the drivers so I should get an increase in the midrange. I'll leave the tweeters alone. Russ is sending some speakers with the yellow tweeters so I'll probably have to swap them out ;) Just to see... What the hell I'm thinken.
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  • dorokusai
    dorokusai Posts: 25,577
    edited April 2004
    The biggest bang for the buck and easiest upgrade, are the Capacitors and Resistors. The Inductors are a pricey upgrade, if you get high quality. Just a thought.
    CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint.
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  • HBombToo
    HBombToo Posts: 5,256
    edited April 2004
    Originally posted by dorokusai
    The biggest bang for the buck and easiest upgrade, are the Capacitors and Resistors. The Inductors are a pricey upgrade, if you get high quality. Just a thought.

    From what I have looked at, the Inductor is 25% that of the caps.

    :confused:
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  • F1nut
    F1nut Posts: 50,729
    edited April 2004
    Yellow tweeters???
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • RuSsMaN
    RuSsMaN Posts: 17,986
    edited April 2004
    Listen to what Jcaut said, don't eff with the inductors, unless you plan on getting the EXACT same guage.

    Cap and resistors, all day all about.

    Dorokoshot and Al Borland were listening to White Zombie at 110db. How could they even discern the midrange? Effin wackos, I tell ya.

    F1, the 'yellow' tweets he's referring to are the SL2000 in the 5b's I'm sending him.

    Cheers,
    Russ
    Check your lips at the door woman. Shake your hips like battleships. Yeah, all the white girls trip when I sing at Sunday service.
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  • dorokusai
    dorokusai Posts: 25,577
    edited April 2004
    Inductor? or Inductors? There is more than one inductor on the board. If you are just buying one, why bother at all. I am going by my source for inductors, North Creek. Compared to some Solen or Axiom caps, they are more expensive.
    CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint.
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  • HBombToo
    HBombToo Posts: 5,256
    edited April 2004
    Originally posted by dorokusai
    Inductor? or Inductors? There is more than one inductor on the board. If you are just buying one, why bother at all. Compared to some Solen or Axiom caps, they are more expensive.

    2 X L1 1.75mH

    Black Gate does not have a direct replacement

    HBomb
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  • dorokusai
    dorokusai Posts: 25,577
    edited April 2004
    Henry - Why worry about Black Gate? Just source another.

    North Creek will wind them per your spec's....but I wish you luck man, looks like a neat project.
    CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint.
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  • F1nut
    F1nut Posts: 50,729
    edited April 2004
    Originally posted by RuSsMaN
    F1, the 'yellow' tweets he's referring to are the SL2000 in the 5b's I'm sending him.

    Ah, the ones you pissed on......
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • jcaut
    jcaut Posts: 1,849
    edited April 2004
    I wasn't really trying to talk you OUT of changing the inductors...I mean, if your goal is to go through and rebuild the crossover with "good" parts, then I can see how you might not want to leave that puny looking little inductor there. I'm just saying that, of the three, I think they make the least difference in sound. That, plus the DCR issue (which IS entirely workable though) and the fact that a heavy-gauge ( 8ga ?! :eek: ), 1.75 mH inductor is going to be a monster.

    On the other hand, purposely changing the DCR on the woofer network is not a good way to try and boost the midrange. There's just too many things in play there. Changing the value of the parallel cap might be a better way.... still if'y. The poly caps and better resistors on the tweeter network might help, too. Even modifying the amount of damping material inside the cabinet might improve the clarity, and perceived quantity, of the midrange (and that's pretty easy and cheap to experiment with).

    Unless you have a way to take measurements or you want to buy a lot of extra parts and tweak by ear, I personally think you're better off sticking with the stock values on the crossover parts.

    Jason
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  • jcaut
    jcaut Posts: 1,849
    edited April 2004
    Another place you might save a few bucks if you wish, is that aforementioned parallel cap on the woofer network. I think the Sonicaps would be overkill there, and the 20uF is getting rather expensive. Solen or even the Dayton polys from PE should be just fine there, IMO. The others might be better, but I think it's diminishing returns when you go above that level.

    Again, just my opinion!

    Jason
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  • HBombToo
    HBombToo Posts: 5,256
    edited April 2004
    Good advice here guys and its appreciated. I think I'll forego the whole inductor excersise and just swap out the caps. Ken did mention the caps from Solen have impressed quite a few people.

    HBomb
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  • dorokusai
    dorokusai Posts: 25,577
    edited April 2004
    Originally posted by HBombToo
    Good advice here guys and its appreciated. I think I'll forego the whole inductor excersise and just swap out the caps. Ken did mention the caps from Solen have impressed quite a few people.

    HBomb

    Yea, and so did a couple people here....this isn't the "never done an upgrade" forum you know.
    CTC BBQ Amplifier, Sonic Frontiers Line3 Pre-Amplifier and Wadia 581 SACD player. Speakers? Always changing but for now, Mission Argonauts I picked up for $50 bucks, mint.
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  • HBombToo
    HBombToo Posts: 5,256
    edited April 2004
    Originally posted by dorokusai
    this isn't the "never done an upgrade" forum you know.

    why do you think I came here and asked for advice BUTMUNCH;)

    ***:D LOL:D ***

    1/4twin
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