Are RDO198-1's "brighter" than RDO194-1's at 6 KHz ?

inspiredsports

Some of you have been following my concurrent modifications of SDA-2B's that I purchased brand new in 1987, and SDA SRS 2' that I purchased in late November '08.

The restorations have been handled identically: Crossovers, Tweeters, Connections, Dynamat, Mortite with very careful attention to detail (following schematics, cleaning contacts with DeOxit, careful sealing and tightening, etc.).

############## no need to go here, but these are the threads ##############
SDA-2B thread: http://www.polkaudio.com/forums/showthread.php?t=74945
SDA SRS 2 thread: http://www.polkaudio.com/forums/showthread.php?t=74946
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I upgraded both with all Sonicaps and Mills on the high pass, For the low pass, all Sonicaps on the 2B's a mix of Sonicap and Aeon (100+82) on the SRS 2's, Cardas Posts and new RDO's.

I upgraded the 2B crossovers to accomodate the mighty fine RDO198-1, and replaced the stock tweets onf the SRS 2's with RDO194-1's.

I have 2 essentially identical NAD Amps, the 7600 Receiver and the 1700 preamp/tuner mated to a 2600A Amp (the 1700+2600 are the IDENTICAL components used within the 7600). Cables and IC's on both rigs are identical MIT AVt-2's.

I now have 200 hours of burn in on the SDA SRS 2's, 200 hours on the IC's and Cables, and 275 hours of burn in on the SDA-2B's so the major changes are already in play. The sound on both pairs was horrible at the start, and is now very, very, very good, with the 2B's smoother by a slight edge, but with no where near the "balls" of the SDA SRS 2's.

One unique feature of these NAD tuners is what is best described as a semi-parametric equalizer feature. You have the abiliity to go PLUS OR MINUS 6 db at 50, 120, 250, 3,000, 6,000 and 12,000 Hz. I've swapped every permutation of amp, wire and speaker possible and the sources are identical. The equalizer feature on both units has a bypass (Off button) feature and I generally listen with it off (no equalization added).

I've done enough listening now to be very familiar with both sets and HERES THE RUB: The SDA-2B's sound perfectly balanced with no equalization. With the same source material, the SDA SRS 2's at 6,000Hz are about 5-6 db quieter than the SDA-2B's. I can verify this with my db meter and double check it by turning on the equalization feature and either decreasing 5-6db at 6,000Hz by 5-6 db on the SDA-2B's, or increasing by 5-6db at 6,000 Hz on the SRS 2's. Again, its the same if I switch amps, wires, etc. so I'm certain the difference is in the speakers.

The high passes are similar on these 2 units, with the SRS 2's having more resistance. Each 2B had one 4.4uf (now 5.8uf for the RDO198), one 12uf and one 2.7 ohm resistor. The SRS 2's use one 4.4uf, one 12uf, three 2.7 ohm resistors and one 3.5 resistor.

Does anyone know if the RDO198 is just that much (5-6db) brighter at 6,000Hz, or could I have a problem in both high pass crossovers on the SRS 2's ???

As a last note, I think the SDA-2B's are nominally 6 ohms and the SDA SRS 2's are 4 ohm.

BrettT1

Not sure if one of the replacement tweeters is brighter than the other.

The third generation SDA SRS 2 were 4 ohms, while the fourth generation were increased to 6 ohms. It depends how old they are.

The 2Bs, I believe, are 6 ohm.

Hope this helped.

Brett

inspiredsports

BrettT1 wrote: »

Not sure if one of the replacement tweeters is brighter than the other.

The third generation SDA SRS 2 were 4 ohms, while the fourth generation were increased to 6 ohms. It depends how old they are.

The 2Bs, I believe, are 6 ohm.

Hope this helped.

Brett

That matches with what my 2B owner's manual says and what I've heard about my SDA SRS 2's which have the 4 MW6509's per cabinet. I thought, however, these were the first generation of SRS SDA 2. I need a compendium!

I just ordered and received a Shure Stylus Tracking Force and have been tweaking my turntable. I think I finlly have it set up just right. I was just listening to these SRS 2's and the sound is absolutely magnificent. On the Genesis "A Trick of the Tail" LP, I had sound coming at me in a 180 degree line from left wall to right wall through my ears at my listening position 8-1/2 feet from the front of the speakers.

The point is, there is nothing wrong with the sound, it's just a bit rolled off from the way the 2B's sound, and I think the 2B's "tonal balance" with the "TL" mod is perfect.

I think I will start hallucinating if I ever get tubes :):)

MillerLiteScott

I also prefer the TL sound/mod for the 2B's over some of the larger non TL SDA's. YMMV.

Scott

Face

MillerLiteScott wrote: »

I also prefer the TL sound/mod for the 2B's over some of the larger non TL SDA's. YMMV.

You're not the only one.

F1nut

I didn't like the RD0194-1's, just sounded hollow, but they are far better than the SL2000's.

I wouldn't call the RD0198-1's brighter, better balanced would be my descrpition, but so were the SL3000's.

BrettT1

inspiredsports wrote: »

I think I will start hallucinating if I ever get tubes

There's nothing wrong with a stack of SS, either.:D

inspiredsports

F1nut wrote: »

I didn't like the RD0194-1's, just sounded hollow, but they are far better than the SL2000's.

I wouldn't call the RD0198-1's brighter, better balanced would be my description, but so were the SL3000's.

You're right, balanced is a better word.

I've been playing music through both sets of speakers for 3 hours, alternating amps, turntables, CD/DVD players since I first posted using multiple formats of the same song. I have some songs where I have the same album in multiple formats (CD burned from computer MP3, original factory CD, SACD, and Vinyl).

In every case, a boost of 5-6 db at 6,000 Hz balances the SDA SRS 2 RDO194-1 sound output to match the SDA-2B RDO198-1 sound. And in EVERY case I then stick with the smooth massive sound the SDA SRS 2's are kicking out.

I just don't like to have to provide that boost as I don't think my next preamp/amp combo up the food chain will have the unique feature my NAD's provide. I guess I won't let the 1700 preamp/tuner go until I have bigger TL enabled cabinets.

I'm glad to learn this is the nature of the tweeter and not a crossover problem.

I'm set with my speakers for a while. My next endeavor is adding a tubed DAC to my system and rebuilding my Thoren's TD 145 (the TD 115 is done).

inspiredsports

Questions:

1) Does anyone know the respective impedance values for the RDO194-1 and RDO198-1. ??
2) What would happen if you replaced an RDO194-1 with an RDO198-1 ??

Face

If you don't add the contour circuit(5.8uf cap) things may sound funny.

inspiredsports

Face wrote: »

If you don't add the contour circuit(5.8uf cap) things may sound funny.

I'm not sure that it was clear I am curious about swapping in the SDA SRS 2 cabinets: swapping the two RDO194-1's in each SDA SRS 2 cabinet with two RDO198-1's.

Knowing the Impedance of one versus the other is my first concern. I was told somewhere in an old post prior to having my high passes upgraded that it wouldn't work, but I didn't get the why part and I thought maybe it was impedance related.

F1nut

Well, it is more or less. Somebody, not me, would have to figure out a new HF circuit for the SRS 2 in order for you to use the RD0198-1 in that speaker.

inspiredsports

F1nut wrote: »

Well, it is more or less. Somebody, not me, would have to figure out a new HF circuit for the SRS 2 in order for you to use the RD0198-1 in that speaker.

Do you know if I would just get "bad sound" testing 198's with the existing crossover network designed for 194's, or would I put my amps at risk?

F1nut

Bad sound.

Systems

inspiredsports wrote: »

Do you know if I would just get "bad sound" testing 198's with the existing crossover network designed for 194's, or would I put my amps at risk?

You might put the tweeters voice coil at risk.If the xover is designed for a 4ohm tweet and you use one with an 8ohm rating the crossover point will be shifted downward ,thus the tweeter will see more low frequency energy.This will comprimise its power handling ability and most likely it will sound harsh because it is being overdriven by lower frequencies than it was intended to reproduce.

inspiredsports

GV#27 wrote: »

You might put the tweeters voice coil at risk.If the xover is designed for a 4ohm tweet and you use one with an 8ohm rating the crossover point will be shifted downward ,thus the tweeter will see more low frequency energy.This will comprimise its power handling ability and most likely it will sound harsh because it is being overdriven by lower frequencies than it was intended to reproduce.

Thanks! I'll leave well enough alone and just run the 5-6 db boost at 6KHz my preamp allows that solves the problem.