2B drivers

Mr. Bubbles

No rush on this as i am still working on the SRS's. Since i was epoxying the magnets on the SRS's and had a rather large amount of industrial epoxy that once started needed to be used all at once I went ahead and pulled the drivers from my 1C's, 2B's, 5jr's, and RTA12B's as well and epoxied all of them at the same time. i found where one driver was replaced in the 12B's (no big issue, just another project for another time). What I found in the 2B's is what i am curious about. Instead of using the 6503's and 6511's as described in the schematics in the sticky by DK these have all 6503's. They do not appear to have been changed as there are no indications on the screws or cabinets that the screws had ever been removed. Also all 4 drivers have the same dating ; all are stamped with July '86 as well as Aug '86. None are marked as replacement drivers or have any warranty designation on them either. has anyone else ever ran into this? I am not in a hurry on this as this will again be another project for another time, after the SRS's are finished.

I am concerned about having the correct drivers. I do not know what t would sound like with the other dimensional drivers in the cabinets but i guess i could borrow those from the 1C's as a comparison. Also I am now wondering how much effect this had on the difference in the bottom end I was hearing between the 2B's and the 1C's when I got the 1C's. Does anyone know any of the basic specs on these drivers (4 ohm/ 8 ohm) so I could possibly determine how the different driver may be affected and or effect the sound with the crossover. I have not inspected the crossover at this point to see if it matches the one shown in the sticky.

heiney9

Are they blade/blade? Probably early 2B's, Polk had no delineation point when going from one model (improvement) to another. They tended to use up all left over parts first. I don't have my SDA compendium in front of me, but tonight when I get home I'll look it up. Are your 2B's with the oak end caps or are they on a base with a front trim piece. Both models are 2B's, but they are different.

H9

Mr. Bubbles

They are Blade/ Blade (1 small and 1 large) They are on the base with the trim piece in front.

I have read many times about how they would use up old stock and figured it may have something to do with that. it makes me curious how the crossover reacts with the different driver and how the sound would be with the other drivers. maybe I'll "borrow" them from my 1C's sometime to see what the difference is.

pitdogg2

2b studios? or another incarnation of the 2a's?
good question...

heiney9

Those are early 2B's and they did use 6503's in all positions. They could even be late 2A's as they were similar if not identical to early 2B's. Transistion models are always a given. I'm sure the 6503 and 6511 drivers are similar enough. The 6511's have side wound voice coils, how that related to how they sound vs. a 6503 with standard wound vc's I have no idea. IIRC, and I'm going purely on memory the side wound vc's allowed more power handling capabilities.

H9

pitdogg2

Brock do you know all the drivers that used side wound voice coils?
I'd be interested in knowing that info
Ivan

Mr. Bubbles

I guess the best way to tell if they are late 2A's or early 2B's is to check the crossover and interconnect since from what I understand the 2B uses only one of the blades in the interconnect and the 2A uses both. Is this correct or is there a better way?

heiney9

oliverbubbles wrote: »

I guess the best way to tell if they are late 2A's or early 2B's is to check the crossover and interconnect since from what I understand the 2B uses only one of the blades in the interconnect and the 2A uses both. Is this correct or is there a better way?

That is a great general assumption and will be true in most cases, again you have transistional models where anything is possible. There is no specific "line in the sand" where one model stops and the other starts. There has always been "crossover models" as they developed and tinkered on the fly back then.

I'd say you are on the right track.

H9

heiney9

pitdogg2 wrote: »

Brock do you know all the drivers that used side wound voice coils?
I'd be interested in knowing that info
Ivan

6510 and 6511 for sure. I'd have to check on the others. Side (edge) wound vc drivers started to be used in SDA SRS's and eventually trickled down to the 1C's in 1987 and then 1B's and CRS+, etc.

H9

pitdogg2

2a's also if mw6510 was one. Maybe that is why my 2a's have a larger sound than my SDA1 signature's that used mw6600 and mw6501's

sorry for the derail Oliver. just trying to soak all the info i can.

heiney9

Ivan, I know for sure 6511. I'll have to check my SDA Compendium when I get home. Might not be the 6510. I'll post difinitively tonight.

Mr. Bubbles

sorry for the derail Oliver. just trying to soak all the info i can.

No problem. H9 backed up what I was already thinking on my question. I'm going to get into the crossovers and IC's to get more in depth in my situation. But I'm going to finish the SRS's first. I'm trying to soak up as much info as i can here so if I can learn anything from your questions too, I'm good with it.

Mr. Bubbles

By the way, what is the member sales rating?

heiney9

oliverbubbles wrote: »

By the way, what is the member sales rating?

It used to be for positive sales in the flea market, but the rating system has be down for close to a year now so even though many, including myself, have had other sales our number has stayed the same.

I believe you get 1 point for each positive sale. Plus if you click on the number you can see the buyers or sellers comments about that particular person and the sale. But the system is down right now.

H9

Joe08867

From the parts list.

SDA 2 3x MW6501

SDA 2A MW6510 MW6510

SDA 2B MW6503 MW6511

Sounds like Polk had some extra 6503's they wanted to move.
The Original CRS's had all 6503's.

But non of the SDA2's had that setup that I know of.

gimpod

oliverbubbles wrote: »

Does anyone know any of the basic specs on these drivers (4 ohm/ 8 ohm) so I could possibly determine how the different driver may be affected and or effect the sound with the crossover. I have not inspected the crossover at this point to see if it matches the one shown in the sticky.

Here ya go from 04/14/2011 (Somebody really needs to make this a sticky hint, hint)

dorokusai wrote: »

These are the only drivers, aside from the RD tweeters, being manufactured to support vintage products, such as, Monitor, RTA and SDA. You should print this as a reference and keep it handy for the values it contains. There are no grill parts, cables, crossovers, plates or anything else available for the older loudspeakers, unless you know the Polk G O D.

1 Driver Type Q BL Compliance DC Resistance Fs

3 MW 6501 1.470 5.96 N 3.250 E - 3N/M 7.750 Ohms 31 Hertz
4 MW 6502 1.970 5.16 N 1.470 E - 3N/M 3.520 Ohms 44 Hertz
5 MW 6503 1.820 5.24 N 3.550 E - 3N/M 6.540 Ohms 29 Hertz
6 MW 6509 2.100 4.57 N 3.540 E - 3N/M 8.970 Ohms 30 Hertz
7 MW 6510 1.390 6.32 N 3.410 E - 3N/M 6.570 Ohms 31 Hertz
8 MW 6511 1.405 4.34 N 3.496 E - 3N/M 3.130 Ohms 29 Hertz
9 MW 6512 1.905 4.99 N 1.588 E - 3N/M 3.466 Ohms 40 Hertz

If all your drivers are MW6503 I suspect that there 2A's, Polk sometimes used 6503's in place of or as a replacement for 6510's they very close spec wise. One way to tell for sure is to see what crossover you have if it's a dual board design (one on the binding post cup and one on the big round inductor with 1 20uF and 2 130uF cap's) there 2A's, If it's a single board design with 1 12uF, 1 20uf and 1 40uF cap there 2B's and half your drivers are wrong. But I don't think this is the case I think you've got 2A's

heiney9

AFAIKT,

the 6503, 6510 and 6511 all were side (edge) wound vc models. I suspect this didn't happen until later so only later models after the SRS's had this feature. My guess, IIRC is was to increase power handling, I doubt there is a whole lot of actual difference in sound from a 6503 vs. a later 6503 with edge wound vc's.

Only the engineers know for sure and I am basing this on the Stereo Review article of the 1987 SDA 1C where they mention the 1C (which is also the single board x-over that can be used with isolated ground amps) uses drivers with edge wound vc's similar to those used in the flagship SRS models.

H9

heiney9

I think you are correct GIMPOD he most likely has 2A's.

H9

Mr. Bubbles

Thanks to all. I'll check the crossovers and IC and let you guys know.

Mr. Bubbles

If all your drivers are MW6503 I suspect that there 2A's

I think you are correct GIMPOD he most likely has 2A's

It appears that you both are correct; Haven't pulled the x-overs but these have the dual round x-overs and the 2 wires going to the IC. I was told when I got them that they were 2B's and they looked like 2B's so I just went with it. So far they sound much better than the 1C's. Haven't been able to get a true comparison to the SRS's yet but will soon. I was initially thrilled with these and just wanted more of what I was hearing with them. That's why i picked up the larger models. I am learning that even though it says SDA it will most likely not sound the same as other model SDA's. I know that sounds stupid but I am not referring to levels or volumes but actually the acoustic details the speakers reproduce. So far none have sounded even similar except for the SDA effect. (of the few that I have heard)

heiney9

oliverbubbles wrote: »

So far they sound much better than the 1C's. Haven't been able to get a true comparison to the SRS's yet but will soon.

Your 1C's must have some serious issues, because the 1C's will better 2A's in every aspect.

H9