Polk SDA crossover question

[jmitchnh]

I recently acquired a pair of very mint Polk Audio SDA-1Cs. The detail, accuracy and clarity of these speakers are amazing and are unlike anything I’ve ever heard before.

From what I’ve read, all of the four 6.5” drivers per cabinet are used when the interconnect cable is attached to create the “SDA” effect, and only two when it is not attached. True?

Since my listening room is not large enough to enable me to set these up correctly to gain the full SDA effect and more than likely I’ll never use the interconnect cable, I’m wondering if it would be wise to re-wire the crossovers to allow all four drivers to operate with out the cable?

From what I’ve read, some SDA owners have done this mod with excellent results. Has anyone else tried this mod and if so, how did it work out and are there instructions for this mod anywhere on the web?

Thanks in advance for your help!

 

[portnoy]

Hi mitch,

I have a pair of SDA 1Cs (original owner since 1990) and i have mine on a 19ft wall in my family room. They are about 7 ft apart and 4 ft from each corner.

As for modding the x-over to put all 4 mid drivers in play without the interconnect cable... well i wouldn't know.

But i'd venture a guess someone on the ClubPolk Forum would be more than happy to give you advice on this venture.

Good luck with that mod (and i'm curious how much the 1Cs cost ya ).

-wayne-

 

[HypnoToad]

The club polk forum is the place to go for information:

http://www.polkaudio.com/forums/index.php

I have a pair also and have them setup with the interconnecting cable and they sound fantastic.

I think you either love or hate the SDA effect since I got them the only other speakers I would want to try are Maggies.

The SDA effect is what makes them though IMO.

 

[jwalker]

From what I’ve read, all of the four 6.5” drivers per cabinet are used when the interconnect cable is attached to create the “SDA” effect, and only two when it is not attached. True?

Thanks in advance for your help!

Not true. With and without the SDA cable, the dimensional drivers are used to produce low frequencies for that same channel (like subwoofers). What is missing without the interconnect cable is the cancelling signal from the other channel, the "SDA" effect.

 

[cornhulio]

Never heard of this mod and I don't think you will gain much. If you do it I would do it at the speaker terminal end and not at the crossover so it's easily reversible. With some speaker wire and terminals just make some Y adapters to feed 2 6.5" mids instead of one. Totally plug and play and 100% reversible for resale purposes.

 

[SDA SRS 1.2]

Polk forum is a good place for the answer. I know that on my 1.2's (8 midwoofers per channel) that without the interconnect cable, only the stereo drivers operate (inside 4 midwoofers for each channel). I cannot imagine listening to SDA speakers without the interconnect cable!

 

[tubed]

I agree. If you don't use the interconnect you might as well sell the SDA's and find another set of nice sounding speakers.

 

[jmitchnh]

Thanks for all your sound (no pun intended) advice. Looks like the x-over mod is a def no-go! I'll need to locate/fabricate an interconnect cable as they did not come with one.

Someone on the Polk forum stated that I need to wire the neg terminals together on the back of my amp. Never saw anything bout that in the users guide, just that the amp/receiver needed to be common ground. Does that sound right to you?

Thanks again!

 

[cornhulio]

You only need to do that if your amp isn't common ground. SDAs require a common ground amp/receiver when using the cable. On the pin/blade cable I use a single run of 10 ga romex flattened a bit on each end to fit snug into the hole. Others use a rca connector with the ground flaps/clips cut off.

 

[kfalls]

I had a pair of the SDA Compacts when they first came out. From what I remember, the SDA effects uses drivers from the direct channel to cancel out the sound from the opposite channel from being heard by the ear of the direct channel.

In other words, the effect speakers of the left channel are out of phase with the direct speakers of the right channel. This causes cancellation of the sound from the right speaker from being heard by the left ear and visa versa. This supposedly causes what's considered to be an almost binaural sound similar to listening to headphones. It is supposed to provide better separation of right channel and left channel signal.

I don't think I'd change the xover. I would guess changing it would result in phase, frequency response peaks/dips and impedance problems. The compacts were already a difficult load to drive.

 

[Sir MLS]

If you have a common ground amp you can use any wire to make a conection between the pin socket ( use a RCA connector with the outer tabs broken off) on the SDA connection. If you don't you will need and A1-A isolation transformer. They are not available from Polk anymore but you can order an Avel isolation transformer ( I can not remember the model # off the top of my head ) but PM me and I can get it for you also with the wiring directions.

The SDA (dimensional speakers on the outside) work with the other 2 stereo dives below 150 htz to produce bass coupled with the Passive Radiator. I have never found it necessary to disconnect the SDA cable and it basically defeats the purpose of the SDA design.

Scott