Modifing SDA-1C's

nascarmann

raife1 has says he modified his SDA's. What does he mean by this? I have heard of bypassing the SDA crossover. Does this change the ohms? Someone try to explain what or how or why you do this.

RuSsMaN

I believe he used upgraded caps and resistors, modifying the current (stock) network....

Check the system showcase, he does provide some information on the mods.....

Cheers,
Russ

DarqueKnight

Nascarman,

I think you may be referring to my post in the "What Polks Do You Guys Have" thread in the Opinion Forum.

Some people like to disconnect (bypass) the internal crossover of their speakers and use an external crossover. This gives the users the flexibility of adjusting crossover frequency points and also better, more defined sound if the external crossover uses higher quality parts than what is used in the speaker. I've never tried it. It sure seems more convenient than the long drawn-out ritual I go through.

With regard to my SDA 1C's, I replaced the mylar and electrolytic capacitors with polypropylene film capacitors. The stock cerment resistors were replaced with lower inductance wire wound 1% tolerance resistors. The stock binding posts were replaced with Vampire BP-Hex binding posts. The grille cloths were replaced with a lighter weight knit fabric. The parts for both speakers cost $275.

I have experimented with replacing internal wiring with heavier gauge OFC (oxygen free copper), but I heard no discernable improvement in the sound. Same with the inductors. Therefore, I left them alone. I have read that some people have heard improvements by cutting off the clips that attach the internal wires to the drivers, but I have not tried this.

The capacitor replacements made a big difference in detail, especially with regard to bass and treble definition. Image solidity was improved also. These qualities also improved over the next couple of weeks as the capacitors were "broken in". When I did the modifications, I did one speaker at a time. That way I could do a quick A/B comparison. I did listening comparisons in mono and in stereo and with the interconnect cable connected and disconnected. The improvements provided by the resistors and binding posts were subtle, but noticeable.

I was somewhat skeptical of realizing any improvements with the resistors or binding posts, so I did the modification in stages. First replacing the caps and comparing the modified speaker to the stock speaker. Then replacing the resistors and comparing the modified speaker to the stock speaker. Finally replacing the binding posts and comparing the modified speaker to the stock speaker. This method is more tedious, but at least I can return half of the parts for a refund if I don't hear any improvement.;)

Don't ever become a tweak. It's a sick addiction.

nascarmann

OK, so changing the capacitors is a noticable improvement and the resistors and binding posts were not? Do you recommend this modification? Interesting, very interesting!

DarqueKnight

OK, so changing the capacitors is a noticable improvement and the resistors and binding posts were not?

Nope, that's not what I said. I said:

The improvements provided by the resistors and binding posts were subtle, but noticeable.

The change in caps made a much bigger difference than the change in resistors and binding posts.

As to whether I recommend this mod, it depends on your musical tastes and associated equipment. I listen to a lot of well-recorded acoustic jazz CD's and LP's from the late 1950's-early 1960's. For me, it was well worth it.

madmax

One day I will try these mods. I read something on a speaker building site that said "be sure to mount the low pass section of the xover on one side of the cabinent and the high pass section on the other". I could see the coils inducing signal from one to the other if they were on the same board so I might try separating them from each other. Another tweek I heard of is mounting a very heavy weight to the bottom of the cabinent. All this stuff could concievably help in my opinion. I would be a little afraid of eliminating the internal xover network and using an external active xover because it would be too easy to damage the drivers if a mistake is made while connecting the cables, if you had a power outage while playing them or if someone changes around the xover points.
madmax