Too Much Tweeter on RTA 12B conversion
Michael8it
Posts: 192
I bought some 12B x-overs to convert my 12's to 12 B's. Prior to conversion, I used my AC-101 and gained up the treble. After converting, I took it out completely, and am actually turning down the treble now. It seems as if they are unbalanced to the tweeter side.
After looking at the schematics, the HF modules are slightly different. I have the peerless tweeters, but I wonder if the x-overs (from 1984) were for the SL1000. The x-over design is slightly different in the 12 and 12B x-overs, most notable the removal of a resistor and cap on the 12B's.
Would this cause the x-overs to have so much more treble that the old? Or is this just a symptom of old caps in an extensive x-over.
After studying both the 12 and 12B x-over, it seems like it would be easiest to convert a 12 to a 12B (since I now have the x-over that goes in the cabinet) by slightly reconfiguring the LF module and leaving the HF module the same.
My dilemma is that I would like to get the treble in-between where it was and where it is now. If I add back in the resistor (R3) to the circuit on the HF side, what will that do to the tweeter output?
After looking at the schematics, the HF modules are slightly different. I have the peerless tweeters, but I wonder if the x-overs (from 1984) were for the SL1000. The x-over design is slightly different in the 12 and 12B x-overs, most notable the removal of a resistor and cap on the 12B's.
Would this cause the x-overs to have so much more treble that the old? Or is this just a symptom of old caps in an extensive x-over.
After studying both the 12 and 12B x-over, it seems like it would be easiest to convert a 12 to a 12B (since I now have the x-over that goes in the cabinet) by slightly reconfiguring the LF module and leaving the HF module the same.
My dilemma is that I would like to get the treble in-between where it was and where it is now. If I add back in the resistor (R3) to the circuit on the HF side, what will that do to the tweeter output?
Carver C-1, M-500 MKII, Yamaha HTR-5835, Polk RTA 12BM's (M-for mod'd).
Post edited by Michael8it on
Comments
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The resistor will attenuate the output. Maybe go half on the resistor if you want less but not totally less.
The original is like 1.5ohms right? Maybe go .75ohms.
The 12b's were designed around the SL2000 not the peerless maybe that is part of the issue as well. -
Joe, thanks, I am thinking that is the problem. Perhaps the Peerless was brighter to begin with than the SL100 or SL2000 (I think the original 12B's were the SL1000) - anyway I like that idea. I might just by a 1.5 and a .75 since I am only talking about $1 investment.Carver C-1, M-500 MKII, Yamaha HTR-5835, Polk RTA 12BM's (M-for mod'd).
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The Xover for 12Bs are all the same Does not matter what tweeter was used. They did change their supplier of caps but they are all the same. Late Cs added a resistor and polyswitch. You cannot compare original RTA 12 xovers and later RTA 12s. Completely different speakers.
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In the early 12s there is only one xover. On the 12Bs and later there are two xovers. The later speakers roll off the outside driver. the original 12s do not do that.
