Improvements To Modified SDA SRS 1.2TL Crossover

PolkMaster1

I added re-enforcement into my SDA SRS 1.2 TLs to hold up the Solen Inductors. The project took 5 weeks to complete thanks to a mistake of placement of the added reenforcement and that I took my time. The project allowed me to replace the original low-frequency inductors and the original high-frequency inductors with the Solen and Jantzen Inductors respectively. The speakers back on line today. This project was long overdue. I purchased the Solen inductors back in December to replace the Northcreek Inductors purchased last year. Thanks to Cincycat purchasing my Northcreek Inductors, it "motivated" me to think about how to tackle the re-enforcement issue, and get the ball rolling installing these big-bad-boys.

I am blown away by the results. Now I cant wait to get the Dreadknought on line with the new AL toroidal transformer when it arrives.

All speakers should sound like this!!!

Toolfan66

Pics??

PolkMaster1

Ill offer pictures next weekend or so. Right now, I am enjoying the sound that these speakers produce. Alot of work went into getting the additional bracing to support the inductors. With the new inductors in place, I deffinetly feel more tactile sensation. I cant wait to hear how these speakers sound when the inductors are fully broken in.

One of the other reasons why my speakers were down for that amount of time is that I worked on finalizing modifications to my turntable. That project is complete. It is the best sounding component in my system.


Overall, I put alot of work put into these speakers these past 3 years. The same can be said about my turntable!!!

Now to get you

PM1

PolkMaster1

As promised - Pics.

The pics shown are the crossover circuit board for the SRS 1.2TL. All original caps, resistors, and inductors have been replaced with Sonic Caps Capacitors, Mills Resistors, and the inductors are Solen and Jantzen for the low and high inductors respectively. The crossover circuit board is the Gimpod Crossover Circuit Board.

The large torodial inductor is the Solen 16mH inductor. The inductor is sitting on the original brace above the PR. More about this work will be explained in another thread.

Since the original stock inductor could not be used to hold the crossover circuit board in place, I had to get creative and hold it in place with a piece of wood which attaches to the crossover Iso-Phase Plate.

The last picture is the circuit board pictured onto the Iso-Phase Plate, getting it ready to insert it into the speaker.

Boy I can hardly wait to hear how this sounds!!!

PolkMaster1

You may be able to notice that added re-enforcement is in place on both sides next to the brace, which adds additional bracing to the speaker. In the picture of my previous post, you will not see the original bracing. When adding the total area of all the bracing above the PR and the inductor, the inductor takes up an estimated 70% or more of the total bracing area.

I cut four pieces off of an 8 foot 2*4 piece of wood, measuring the cuts to 272mm and sanded it down appropriately to fit inside the speakers. Each speaker has two of these pieces of bracing to hold the inductor in place. The top part of the additional bracing had to line up exactly where the top of the original bracing is. The 2*4 wood does not line up to the bracing on the bottom of the original bracing. Life is not totally perfect. Once it was lined up, Gorilla Glue was used to hold the additional bracing in place. I let the drying process take place overnight.

The next step was to add additional support to the bracing in an attempt to distribute the weight of the inductor evenly across all three bottom braces. I cut four pieces off of a square 1 inch by 36 inch piece of wood. Each peice was cut to 7 inches. Sanding was performed to smooth out any left-over wood debris that could be left by sawing. Each speaker gets two of these peices each. The first piece goes flush back to the speaker and on-top of the bracing. It is possible that the excess glue of the original bracing can prevent the wood from flushing back to the speaker. When this happens, cut off this glue and replace it with Gorrila Glue. Then flush the 7 by 1 inch square wood to the back of the speaker and on top of the bracing. Gorilla Glue was placed on the wood where the 7*1 meets the back of the speaker and the top part of the bracing. Both of these procedures can be done at the same time. I used metal braces to hold the wood in place and left it nearly 24 hours to dry. I place the second piece of 7 by 1 inch on top of the bracing, near the front of the speaker, but not flush. This leaves room to put the circuit board in place. I left a finger-length of room between the front of the speaker and the second 7*1 inch brace in place, then applied the Gorilla Glue. I used metal bracing to hold it in place and let it dry 24 hours.

PolkMaster1

After 24 hours elapsed, I removed all of the metal braces and tested for rigidity on the 2*4 bracing and the 7*1 inch bracing. There was no movement what-so-ever. Even trying to use incredible strength to find weakness in the additional support structure that I put in place, no movement was detected on the 2*4's or even the 7*1. I gave it a mini stress-test placing the inductor on top of the bracing. Gotta love Gorilla Glue!!! It held it in place. I left the inductor in for 24 hours as I repeated my steps in the other speaker. After 24 hours elapsed, I wanted to have additional support below the bracing. Using the leftover 2*4, I cut four additional 7 inch peices, placing the first peice flush in back of the speaker and below the additonal bracing 2*4. Note that because the 2*4 does not match the original bracing, this peice of wood does not line-up with the original brace that Polk used. I decided to live with this for now. If excess glue is encountered from the original bracing that prevents the wood being flush to the back of the speaker, cut the excess glue. Use Gorilla Glue to hold the original bracing in place if necessary. I placed the second peice of wood below the bracing near the front of the speaker, but did not flush it to the front of the speaker since this would interfere with the PR. Use bracing to hold the wood in place and let it set for 24 hours. Remove braces and repeat stress-tests below and above the bracing and be impressed. A Gorilla would not be able to budge the wood-work. The bracing to hold the massive Solen inductor in-place was complete.

In order to keep the Solen Inductor in place to keep it moving within the plane of the bracing, I used a 4 foot dowel which is 1.25 inches in diameter. I cut 7 pieces off of the dowel for each inductor. Each peice measured 62mm in height. I sanded each peice for smoothness which gives better surface-contact the peices are glued onto the bracing. To make sure that the inductor does not move, I placed the inductor onto the bracing, glued four peices of dowels, placed them inside the outer rim of the inductor opening, then braced them down and let it dry 24 hours. Once that was complete, I placed the remaining three dowel peices inside the inductor. Because the braces I had would not reach the inner-most part of the inductor, I let them dry as-is and left it for 24 hours. I then removed the inductor (warning - this inductor is HEAVY!!!) gave the dowels a stress test and was satisifed with the results. I repeated the same steps for the other speaker.

PolkMaster1

More to follow tomorrow.