Backward 1Bs

bigaltx24

I've had my 1Bs for about four years now and never had any problems with them. I've done all the mods and even did the "unofficial" TL mod. They sound great and I'll never get rid of them. I've been playing with the resistance in the tweeter circuit to get the voicing just right. This afternoon I changed the resistance in the tweeter circuit, buttoned them back up, ran the quick checks, everything was fine.

Just for kicks I decided to check the resistances per the SDA handbook, never really saw a need before. What I found is that the readings on my speakers are backwards, or the SDA handbook is backwards. Is this something that will affect the speakers performance, or something I should be concerned about?

Dennis Gardner

Give examples of what you mean by backwards.

westmassguy

If you have the original Polk Binding Posts, make sure the polarity is correct, Red/Hot on left, Black/Ground on right. If you changed inductors when you upgraded, especially the sub-base drive inductors, this will affect your resistance readings. Double check the wiring between the two halves of the crossover. It's easy to accidentally reverse the polarity on them.

bigaltx24

I went through them and double checked the wiring yesterday. They are wired per the schematic in the SDA handbook. If you reverse the wires between the high and low crossovers the resistance readings are way off, not just backwards.

westmassguy

Well, if everything checked out, and the sound the way they're supposed to, I wouldn't worry about it.
Errors have been found in the Handbook before.

Schurkey

bigaltx24 wrote: »

I've had my 1Bs for about four years now and never had any problems with them. I've done all the mods and even did the "unofficial" TL mod...

...Just for kicks I decided to check the resistances per the SDA handbook, never really saw a need before. What I found is that the readings on my speakers are backwards, or the SDA handbook is backwards. Is this something that will affect the speakers performance, or something I should be concerned about?

My 1Bs also have the "TL" mod; I'd be happy to take resistance readings so you have something to compare to. I remember that mine were different from the Handbook, but not so different that I thought there was something "backwards".

Of the 8 MW6509 drivers, none of them had the same DC resistance. Not surprising that the speaker assemblies vary in the readings.

bigaltx24

I found that mine were wired wrong from the factory, and it does make a huge difference. I bought them from the original owner and I know he never opened them up or messed with them. When I originally opened them up to do a recap I marked the locations of the wires with Sharpies. I used to do Industrial Maintenance, so I am very thorough about marking wires when taking something apart.

Yesterday I assumed that they were wired correctly from the factory (they were wired per the schematic), today I decided to question everything. I was pretty sure the boards were good, the resistances were right, just backwards, so I decided to look at the wiring first. I started at the binding posts, the white wire was on the post I had marked with a Sharpie. I flipped the speaker up to find that it was actually on the black binding post. Both speakers were wired like this, but when I swapped them the resistances were wrong but not backwards. Then I swapped the interconnect leads where they join the low crossover, bingo, the resistances were right.

I buttoned the speakers back up, ran the quick check, and put on some music. They almost sound like different speakers. The soundstage is more coherent, they have better detail and the bass is tighter. I probably listened to them for about four hours this afternoon, all the time with a big smile on my face.

westmassguy

Glad you got it straightened out.