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Infinity Crossover mod?

Renegade

Renegade

Well-Known Member
I have a set of Infinity RS 3000 speakers with the polycell tweeters. Not bad, but not nearly the level of the Emits. I get it, I didn't buy the emits, but, I was reading a thread, https://www.diyaudio.com/forums/multi-way/268222-speakers-impedance-match-2.html and post 16 in that thread stood out to me. In particular,

"But that is not the issue for the poor treble sound of the RS-3000. It is the second order filter on the tweeter that needs correcting, as I said. A third order filter will increase treble energy above crossover. It will sound more lively. Simple as."

So, my crossovers for my polycells can be modded to sound better? The orders of filters and whatnot escape me, can someone tell me in English what that post means please?
 
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That looks pretty straight forward. No changes to the original crossover. Just the addition of a 6.8uF cap, to create the 3rd order filter. Then, a parallel 22 ohm resistor, to tame the tweeter level a bit. Both high lighted in Red. Oh, swap the tweeter leads too, since you need to change polarity, since the crossover roll off is now 18dB.

So, pull the tweeter, and swap the +/- wires at the tweeter. On the negative wire, somewhere close to the tweeter, solder in the 6.8uf cap. Then, solder a 22 ohm resistor across the plus and minus tweeter wires, connecting them. Probably a 10 watt or higher cast resistor will do. All the mods can be done by pulling the tweeter and adding the cap and resistor, with the tweeter hanging out.


Infinity RS3000 Mods.PNG
 
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One other thing. If you have decent soldering skills, you could solder the resistor directly across the tweeter +/- leads, and then add the cap directly in-line with the - side.
 
Renegade said:
"But that is not the issue for the poor treble sound of the RS-3000. It is the second order filter on the tweeter that needs correcting, as I said. A third order filter will increase treble energy above crossover. It will sound more lively. Simple as."
Click to expand...
Doesn't sound right to me. A third order crossover will reduce treble energy below the crossover frequency, yes, but why would it increase energy above the crossover frequency?
And is the treble quality poor, or just low in volume?
 
Renegade said:
I have a set of Infinity RS 3000 speakers with the polycell tweeters.
So, my crossovers for my polycells can be modded to sound better? The orders of filters and whatnot escape me, can someone tell me in English what that post means please?
Click to expand...

I see where you're looking to improve the sound of your Polycell tweeters. Are the caps in the crossovers electrolytic's or poly's? If they are electrolytic's a simple switch to poly's of the same values should perk them right up. Another option is this.
I have some speakers that cross the tweeters at 4000Hz with a third order network. i didn't like the stock tweeters so I put in some Polycell tweeters I have and they sound very good. Compared to an Infinity with the EMIT, the fine detail and top end extension isn't there but the rest isn't that far off. The HP has a 4.7uF cap, a .27mH inductor then a 10uF cap. Not textbook values but it works. Audyn Q4 caps and a air core inductor.
Don't forget to wire the tweeter out of phase :thumbsup:
 
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rothwellaudio said:
Doesn't sound right to me. A third order crossover will reduce treble energy below the crossover frequency, yes, but why would it increase energy above the crossover frequency?
And is the treble quality poor, or just low in volume?
Click to expand...
Good points, and I honestly don't know for sure. I was a musician for many years, drummer in primarily classic rock and blues bands. The speakers, as they are, sound very good, sourced by a medium to low 30 something watt tube amp. As a drummer, well I like drums and I just don't hear much of the top end (high hat and cymbals) work that I know is there. That is what I want to bring out. The mid and bottom are very good as is. The quoted description I posted from the other site described exactly what I'm after, just to liven things up a bit. Whether or not the method described is the fix I don't know, so that is why I asked for opinions over here at AK.
 
RickeyM said:
I see where you're looking to improve the sound of your Polycell tweeters. Are the caps in the crossovers electrolytic's or poly's? If they are electrolytic's a simple switch to poly's of the same values should perk them right up. Another option is this.
I have some speakers that cross the tweeters at 4000Hz with a third order network. i didn't like the stock tweeters so I put in some Polycell tweeters I have and they sound very good. Compared to an Infinity with the EMIT, the fine detail and top end extension isn't there but the rest isn't that far off. The HP has a 4.7uF cap, a .27mH inductor then a 10uF cap. Not textbook values but it works. Audyn Q4 caps and a air core inductor.
Don't forget to wire the tweeter out of phase :thumbsup:
Click to expand...
Yeah, just want to liven up the top end stuff a bit. I have not looked at the crossovers so I don't know what caps they have. I would expect they are original, but can't be sure. I've only had the speakers for 3 or 4 years and never really even used them regularly. I have done some recapping and such on my vintage gear but not these, yet. For me, swapping parts is usually pretty easy, and fun, but I don't have sufficient knowledge to always know what parts to swap. I am open to suggestions, actually, I welcome them.
 
Renegade said:
This is what I have,,,,
http://www.infinity-classics.de/technik/manuals/RS_3000_technical_sheet.pdf
Click to expand...
Two simple ways to increase the output from the tweeter would be to reduce the value of R1 and increase the value of C1/C2. You could tack on a resistor in parallel with R1 to reduce its value. Try about 1 ohm and 2 ohms to see what happens.
Same with C1/C2 - tack on a capacitor in parallel to increase the value. Doing so will also lower the crossover point and allow a bit more bass energy into the tweeter, which might not a great idea. Try adding 1 or 2 microfarads and see what happens.
This is not a particularly scientific method but worth trying anyway.
 
RickeyM said:
I see where you're looking to improve the sound of your Polycell tweeters. Are the caps in the crossovers electrolytic's or poly's? If they are electrolytic's a simple switch to poly's of the same values should perk them right up.
Click to expand...

I have to agree. From what I read of the tech sheet they are using electrolytics for both the tweeter and woofer. I would replace the caps with like for like value and sub a poly in for the electrolytic on the tweeter side. I have recapped a few of my own vintage Infinitys and it makes quite a difference.
 
The tweeter is already using a bypass cap. On most Infinity Tech Manuals, that cap type is noted as a poly cap. I expect that bypass is a film too, even though it's not noted. But, before modding the existing crossover, swapping in a 3.6uF poly would probably improve the treble response, with nothing else extra required.

Now, if you like to crank, doing the mods, to a 3rd order crossover, will definitely provide better tweeter protection, and higher power handling. Still, try the single poly, to hear what that does. Then try the 2nd cap, to see if you hear further improvements?
 
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StimpyWan said:
The tweeter is already using a bypass cap. On most Infinity Tech Manuals, that cap type is noted as a poly cap. I expect that bypass is a film too, even though it's not noted. But, before modding the existing crossover, swapping in a 3.6uF poly would probably improve the treble response, with nothing else extra required.

Now, if you like to crank, doing the mods, to a 3rd order crossover, will definitely provide better tweeter protection, and higher power handling. Still, try the single poly, to hear what that does. Then try the 2nd cap, to see if you hear further improvements?
Click to expand...
I think at this point I want to just try the 3.6uf switch to poly, but It seems I'm having trouble with finding this exact product. I have found this,
Solen Capacitor 3.9uF 700Vdc AGM Silver, and
Solen Capacitor 3.3uF 700Vdc AGM Silver, neither of which are very cheap at like 15 bucks apiece.

So, are either suitable and better yet, does someone have a better source. These are from Parts Connexion.
 
Parts Express has 3.0 and 3.3. You could always use 3.3 + 0.33. They have both film and foil, and metallized foil. No 3.5 though, kinda odd.
 
toxcrusadr said:
Parts Express has 3.0 and 3.3. You could always use 3.3 + 0.33. They have both film and foil, and metallized foil. No 3.5 though, kinda odd.
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So to add 3.3 to .33 would I solder them in parallel to each other? Also, how relevant is the voltage? I see price goes up significantly with higher voltage.

I have not yet pulled the xovers out yet so have no idea what voltages are in there.
 
Renegade said:
So to add 3.3 to .33 would I solder them in parallel to each other? Also, how relevant is the voltage? I see price goes up significantly with higher voltage.

I have not yet pulled the xovers out yet so have no idea what voltages are in there.
Click to expand...

Yes, wired (soldered) in parallel like the originals. Most all poly caps have a higher voltage rating than electrolytic's so that's not a problem. Parts Express has Audyn Q4 series caps in those values. I's what I used for my Polycell tweets and I can vouch for the SQ, ;)
 
Yeah, for some reason 'audio' grade caps seem to have 250, 400 or even higher ratings. The price is not necessarily directly related to the voltage rating. Usually other characteristics go along with fancy caps - polypropylene film spun by virgins and so on.

I wouldn't go for anything real fancy right off the bat. Dayton is fine for many applications and won't break the bank.
 
OK so I pulled one crossover and here is what I find,,,,,,,
xover1.jpg
So the blue one is 3.3uf and the little brown guy is .33uf, which is labeled on the datasheet as C1 and C2. These should be replaced with poly seems to be the general consensus. I plan to do that, but there is also another capacitor at C3, a 10uf I think. Is there a benefit to replacing it with poly as well?

The datasheet pdf is below.
 

Attachments

That 10uf is the shunt cap on the woofer section of the X-O. It's not directly in the signal path so changing it won't improve the tweeter. Now for the fun part. It may be easier/simpler to mount the tweeter X-O parts on a separate little board and use a couple of short wires to connect that to the present X-O circuit board.
 
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