New Polk speakers, JBL subwoofer and wiring tweaks

Gentle reader,

Thanks for stopping by here to see what I've been up to. There have been many changes in the den/listening room. I'll start with the audio ones.

A few weeks ago, I mentioned that I'd found a like-new late model Polk Audio center channel speaker. Since they are selling new ones for less than $90 on ebay, I decided to keep it. Just as well as I discovered the woofer on the old Polk Audio central speaker had frozen and would not move! 

I sold some things on ebay to finance the purchase of matching late model Polk Audio speakers to match, sonically, the new center channel unit. To my delight, I found a "previously enjoyed" pair on ebay and won them for $61.00. Here the room is with them:

Yes, the face/drivers color is slightly off, they nicely contrast with the Axioms below. The important thing is that they were designed to match sonically with the center channel. These are model 30s, they make model 40s that are basically the center channel standing vertically. However, and you no doubt have noticed this, the 30s have the tweeter on the bottom. "What the heck?" That is the way they are designed to work. Plus, if you look closely, they line up horizontally with the tweeter in the center unit. Yeah, I planned it that way all along. ;-) Here's some more photos comparing the old and new Polk Audio Monitor speakers:

Basic two-way design. Note that the tweeter, now unprotected sits as close to the woofer as possible. Note the tiny reflex port on the old Polk, below the woofer. Speaking of woofers, they have rubber, not cheap "foam" surrounds, so no worries about them falling apart in later years.

See how large the reflex port is on the newer model? Note also the twin terminals.

The twin pairs of three-way binding/banana terminals have jumpers connecting them. This is for "Bi-wiring" the speakers. Ideally, one would have TWO stereo power amps from the same maker.  One putting out, say 50 watts per channel, the other 200 or so. It takes way more energy to drive a woofer than a tweeter. So, remove the jumpers, pull the caps out of the bottom terminals if using banana plugs, and run TWO pairs of wires to each speaker. The wires from the bigger amp to the woofers, the smaller amp to the tweeters. Some cable makers produce single cables with four wires in one unit for bi-wiring purposes. Not cheap, though.

Although the older units only have spring terminals, Polk Audio at least made them 3/4" apart and with holes large enough to accept banana plugs. So what are banana plugs? See below:

Above is one Monster M Series cable I bought via ebay to use in the main system. Why? In order to utilize the JBL subwoofer I found at Salvation Army:

Take a careful look at the photo above. Note the "LINE LEVEL IN" and "HI LEVEL IN" terminals. The former, is directly from your receiver or preamplifier outputs. In a home theater receiver, they usually have one or two RCA outputs marker "SUBWOOFER". Connect one or a pair of cables from there into the RCA inputs and you'll have all your Bass come from the sub. Another way, if you want to control where the Bass comes from is via the latter larger terminals. From your front channel speaker outputs, or in my case from the stereo amplifier, run speaker wires into the input terminals. Pay attention to polarity, and left or right. Red in red, left in left, etc.

These are the cables that originally plugged into the Dynaco power amp to feed the Axiom speakers. Below is the new cable cut in two with banana plugs and new speaker "pants". If you go two pictures up, in the close up you can see the difference in size of the total plugs. The important thing is the banana tips are always the same size. I got this cable cheap because it was only one and the insulation on the + side was gone.

No problem, red electrical tape to the rescue. These M Series cables have a mix of thick wires and thin wires. Monster thinks that the high frequencies will travel the smaller ones, the Bass, the thicker ones. True? Who knows. The only plugs I had the would fit these wires are Monster's units the screw on like wire nuts.

If you look closely at the two photos above, you can just see that there are two red and two black wires in each cable. These would work for bi-wiring. I bought some new Nakamichi banana plugs, but they would not fit the cables AND the covers. I'll find some use for them, I'm sure.

(Above is the Belden/Hubbel cable for the JBL, the AC-9 for the Dynaco and the Pangea AC-14 for the other (12") subwoofer. Note how BIG the AC-9 is!) I had a power cord/cable that I'd made for one of the CD units with Belden 19364 cord and a Hubbel plug plus an Asian IEC plug. Since then, I scored another Pangea power cable which replaced the one I made. So, I removed the stock zip cord plug on the JBL and installed the Belden. It was made to have a three conductor cord, so I soldered it in.

Above and below you can see the power cable plug I had to adapt to the massice Pangea AC-9 which has 7 gauge wiring and is huge. The plug came via ebay from Hong Kong. It was a job to make it work. One of the connections broke somehow in the factory molded on plug.

Above shows all four speaker cables attached to the Dynaco amp. The bottom ones (twisted blue and silver) travel into this room, the "office". More on that in a future episode.

Above, although it looks a mess, it is what I had to do to fit the new cables. So, in conclusion, the new ones come FROM the amp, TO the INPUTs on the JBL Sub, the OUTPUTs have the original Monster cables with the braided sleeves that connect to the Axiom speakers. I've been playing with the crossover frequency and Bass volume to find the right balance of Bass verses rest of the frequencies.

Below, is a Pangea AC-14SE cable I got via ebay with an IEC to C7 adapter. Looks funky and perhaps straining the cable.

Above and below are the two pieces. Note how small the three IEC terminals are. Those 7 gauge wires have to be attached to the female version of these. 

Below, is the newly completed cable with a purpose built AC7 plug.  Again via ebay from Hong Kong. I knew these plugs existed out there some where. One can buy Pangea and other brands of cables with an AC7 plug molded on, but they aren't cheap.

I ended up removing the ground plug from the male plug, it was no longer needed and I had to plug  it into a two-terminal outlet as you can see below.

Since we are in the den, prior to all that I'd done above, I decided to get the LP shelf off the edge of the Asian rug, it made the shelf tip back and just looked wrong. 

Above, to the right, you can see the rug is free of the shelf. I had to empty the shelf and move the heavy oak filing cabinet in order to move both off the rug. I also had to get it out from under the stereo shelf so that I could move it towards the left wall.

Note what the wall to the left of the shelf has on it right now, above.

Above is the corner where the filing cabinet used to be. Note the authentic Battlestar Gallactica recruiting posters to the right of the window and the new location of the sunset photo I shot from Skyline Drive MANY years ago.

Finally, above is the new home for the blue painted (why did the previous generation paint nice wood?) oak filing cabinet that someday I'm going to strip and refinish. As noted above, the floor radio sits in the corner now with the black and white TY cat on top.

Thanks for looking and suffering through my obsession! Over 30,000 hits so far!

Scott