September 26, 2017

Polk Audio SDA Compact Speakers System

When choosing a speakers system, I usually need to evaluate it directly on my listening room. It is not an easy pick up stuff and hope it will suit to my listening preference or with the room acoustic. There is no way I can tell how good one speaker to another by just only looking to the specification.

Like this Polk Audio SDA Compact Speakers that just coming to my house last week. I can only say nothing than WOW. The finished of this speaker is astonishing and the drivers configuration are extraordinary.

Remembering this speakers are actually build around 80's and maybe the older it get, the mature sound it is. Just like a bottle of wine.



I am pretty sure that most of Polk Audio fans already enjoy a good sound system from this type of speaker. Perhaps not exactly like this SDA compact type, but many others Polk Audio speakers that built at that era has impress many audience so far.

By looking to this vintage Polk Audio SDA speakers on my desk is in a very good condition. No wear on the drivers, just a small dirt spotted but overall presentation is just like new.


The weight of each speaker is around 15 kilos and it is quite heavy due to the high quality of the MDF board and others material use inside.

The dimension of this speaker is approximately a meter. This is not bookshelf speaker, and of course not floor-standing speaker either.

This kind of speaker is horizontally mount and typically found in the recording studio.




The driver for each speaker have an identical dual 2 way system. Dual 5 inch woofer and dual 1 inch tweeter. They just like 2 system in a box.

One pair is for main speaker and the others is Polk Audio proprietary multi way system that will explain later on this review.


I'm moving to the back side of this speaker and there's something really attract me. There is a big driver covered with steel grille is actually a 12 inch passive woofer system. This means only a cone without any motor coil driver that move based on the back pressure of the main drivers. This to help better bass response compare using the port size which naturally cause more distortion.

There is a warning notes from the maker that should be understand by the user on how this speaker system works.


This warning tells that this speakers is only works for the common ground amplifier. I am using Tripath amplifier that  in bridge tied load (BTL) system and this is not recommended to use with this speaker.

First things first, what is common ground? Easy explanation is when the speaker output from the amplifier share the same negative for both channel. This can be check by using multi-meter and test the continuity for both negative speaker output from the amplifier.

While on the BTL amplifier, they are totally separate amplifier for each polarity of the speaker output. The problem would be occurs when connecting the BTL amplifier to this Polk Audio SDA because the internal configuration of the speaker has connected the negative polarity of each speaker right and left. This could damaging the amplifier.


This speaker system using proprietary interconnect cable to connect between left and right speakers. Just like my explanation on dual driver on each speaker above, the function of this interconnect cable is actually to activate the second speakers system to get more bandwidth, more dynamic and more spacious sound.

This configuration is possible just like using the cross feed on digital system. This could expanding the sound-stage of the speakers presentation.

The BTL amplifier like the Tripath amplifier still can be use with this speaker but without the interconnect plugged. Of course you will missing the extra benefit from the system.


Looking at the terminal speaker cable, this speaker using the banana plug along with the screw type for spades or bare cable connection.

Above it, there are 2 fuse for protecting the tweeter drivers.


As usual, I always clean up the speaker connector with contact cleaner before do any connection to my audio system. This is to get full potential from the speaker itself.


Comes my curiosity about what components inside this speakers.

So I open up the speakers terminal which is very easy, then I have one package cross-over circuit at the back of that speaker terminal housing.


The big air core inductor is uniquely winding to the speaker terminal housing. A clever design by Polk engineering to save space internally.

There is another cross-over circuit identical just like at the terminal speaker housing. It is inside the box and it is really hard for me to take the photo of it. I can confirm both cross-over are identical, so there are 2 cross-over circuit on each box.


I also wondering what is inside this woofer driver.


So I simply open it up.

The woofer driver are original and the production date is July 1984, very nice!


Here is the passive woofer viewed from inside the box. It is directly facing to the back of the woofer drivers.



So after all, how does it sound?

I connected this speakers to my main audio system. I playing several music album and the most noticeable performer when I playing the music from Inger Marie - Make this Moment and Diana Krall - Live in Paris.


One things for sure, the vocal is very sweet. I feel the singer voice is detail and warmth. I just can tell it is a little bit forward presentation compare to my previous speakers system but overall this speaker is amazing.

The bass are solid and the timing is correct. One more plus point from passive woofer at the back of this speakers is I can adjust on how loud is the bass by playing the distance between wall and speakers.

The others common problem from this multi way speaker are mostly phase and timing are not correctly implemented. But not for this speaker. The tweeter and woofer played coherent, no gap, no timing delay between those drivers. What I hear is all perfect sound.

I could only say WOW again and again for this vintage speakers. I think for recent speakers with mediocre build quality and higher price tag are still struggling to get better sound like this Polk Audio SDA.


Disclaimer: Any statement and photos in this article are not allowed to copy or publish without written permission from the writer. Any injury or loss from following tips in this article is not under writer responsibility.

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