RTA 8Ts

deronb1

Believe it or not, my RTA 8Ts came with 4 mw6511s. Have long since sold drivers, but looking to replace. Would either 6503 or 6510 work?

skrol

Well that is a convoluted story. Based on the various schematics, the original RTA-8T used the MW6501. Then the revision used the MW6510. Then the RTA-8TL rev 2 calls for the MW6516, which I almost never see.

Here are the specs for several MW-65xx drivers:


Driver: MW 6500 Driver's model #.
Brand: Polk Driver's brand name.
Fs: 31.0000 Hz (Free air resonance)
Vas: 2.6486 ft^3 (Compliance volume)
Qts: 0.2190 Total Q
Qms: 1.3000 Mechanical Q
Qes: 0.2640 Electrical Q
Sd: 0.0130 M^2 (Piston area)
Xmax: 3.1800 mm (Cone excursion, linear)
Revc: 6.5000 ohms (DC resistance)
Znom: 8.0000 ohms (Nominal impedance)
Pmax: 35.0000 watts maximum rated power


Driver: MW 6501 Driver's model #.
Brand: Polk Driver's brand name.
Fs: 31.0000 Hz (Free air resonance)
Vas: 2.7545 ft^3 (Compliance volume)
Qts: 0.2790 Total Q
Qms: 1.4700 Mechanical Q
Qes: 0.3440 Electrical Q
Sd: 0.0130 M^2 (Piston area)
Xmax: 3.1800 mm (Cone excursion, linear)
Revc: 7.7500 ohms (DC resistance)
Znom: 8.0000 ohms (Nominal impedance)
Pmax: 35.0000 watts maximum rated power


Driver: MW 6502 Driver's model #.
Brand: Polk Driver's brand name.
Fs: 44.0000 Hz (Free air resonance)
Vas: 1.2360 ft^3 (Compliance volume)
Qts: 0.2790 Total Q
Qms: 1.9700 Mechanical Q
Qes: 0.3250 Electrical Q
Sd: 0.0130 M^2 (Piston area)
Xmax: 3.1800 mm (Cone excursion, linear)
Revc: 3.5200 ohms (DC resistance)
Znom: 4.0000 ohms (Nominal impedance)
Pmax: 35.0000 watts maximum rated power


Driver: MW 6503 Driver's model #.
Brand: Polk Driver's brand name.
Fs: 29.8600 Hz (Free air resonance)
Vas: 3.0017 ft^3 (Compliance volume)
Qts: 0.3100 Total Q
Qms: 1.7680 Mechanical Q
Qes: 0.3760 Electrical Q
Sd: 0.0130 M^2 (Piston area)
Xmax: 3.1800 mm (Cone excursion, linear)
Revc: 6.5400 ohms (DC resistance)
Znom: 8.0000 ohms (Nominal impedance)
Pmax: 35.0000 watts maximum rated power

Driver: MW 6517
BrandL Polk Audio
* Size / Type = 6.50" treater paper cone woofer
* SPL = 91 db @ 1w/1m
* Wattage = 125 Watts RMS / 250 Watts Peak
* Treated cone woofer, rubber surround
* Response = 40 Hz. to 10 kHz.
* Weight = Right a 4 pound ea.
* Magnet = UnShielded
* VC = 1" ( 25 mm)
* Ohms = 4 ohms
* f(s) - 55 Hz.
* Q(ms) - 7.261
* V(as) - 14.60 liters ( 0.516 cf. )
* n(0) - 5.02%
* M(ms) - 18.38 grams
* R(e) - 1.86 Ohms
* Q(es) - 0.048
* SPL - 92 dB @ 1W/1m
* C(ms) - 0.44 mm/N
* Z(max) - 281.50 Ohms
* Q(ts) - 0.048
* L(e) - 31.08 mH


This information won't tell you how a driver sounds, only what to plug in for basic mathematical modeling. For example, these drivers all used a doped paper cone & rubber surround (Polk made these themselves for many years, using cone & surround from Kurt Mueller Co in Gemany, don't remember where the basket & magnet assemblies came from), but the specs don't describe everything -- including the breakup/resonant modes of the drivers which have a lot to do with the resulting sound.

So simply substituting a different driver brand or model with different construction but having identical specs will virtually guarantee it will sound different. Better or worse? No way to know without trying.
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PartsExpress (Dayton) 295-305
Power handling: 50 watts RMS/75 watts max
Voice coil diameter: 1-3/8"
Voice coil inductance: 1.40 mH
Impedance: 8 ohms
DC resistance: 6.0 ohms
Frequency response: 33-4,000 Hz
Magnet weight: 15 oz.
Fs: 33 Hz
SPL: 88 dB 1W/1m
Vas: .98 cu. ft.
Qms: 2.75
Qes: .37
Qts: .33
Xmax: 3.15mm
Net weight: 3 lbs.
Dimensions: Overall Diameter: 6-1/2"
Cutout Diameter: 5-3/4"
Mounting Depth: 3-3/16"
Magnet Diameter: 4"
Magnet Height: 1-3/16"


The MW6510 is no longer available through us and the MW6503 is the substitute. It is *close* but not an exact match. Here's some of the basic differences:

6510 vs 6503
Q 1.82 vs 1.39
BL 5.24 vs 6.62 N /AMP
Compliance 3.55E-3 vs 3.41E-3 N/M
DCR 6.54 vs 6.57 ohms
Fs 29 vs 31 Hz.


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 1.47 5.96 N 3.25 E - 3N/M 7.75 Ohms 31 Hertz
4 MW 6502 1.97 5.16 N 1.47 E - 3N/M 3.52 Ohms 44 Hertz
5 MW 6503 1.82 5.24 N 3.55 E - 3N/M 6.54 Ohms 29 Hertz
6 MW 6509 2.1 4.57 N 3.54 E - 3N/M 8.97 Ohms 30 Hertz
7 MW 6510 1.39 6.32 N 3.41 E - 3N/M 6.57 Ohms 31 Hertz
8 MW 6511 1.405 4.34 N 3.496 E - 3N/M 3.13 Ohms 29 Hertz
9 MW 6512 1.905 4.99 N 1.588 E - 3N/M 3.466 Ohms 40 Hertz

deronb1

Thank you sir! I will print for future reference. It wasnt until i joined the forum, that i found having 6511s in the 8Ts as odd. Bought them in Germany, so dont know if that would have made a difference. Sounds like either 6503 or 6510 will work fine.

skrol

That is quite a difference in impedance between the 6510 and 6511. I'm curious about what the crossover components are and if they match any of the schematics.

pitdogg2

I'd be interested in that as well.

deronb1

I really dont know. I bought them at the PX on Ranstien AB in Germany in 1990.

deronb1

Found two 6503s on Ebay for a decent price. Need two more!

verb

Hello @deronb1 - Do you still have the MW6511's? I am in need of one. Thanks !!!

deronb1

verb wrote: »

Hello @deronb1 - Do you still have the MW6511's? I am in need of one. Thanks !!!

No. I have ( 4) 6503 tho

xschop

So 6516's are unobtainium at this point?

agfrost

Believe so. Ebay/scour CL for speakers to part out. Just the 8TLs have them, as noted above.

xschop

So the 8TLs have the front ports raised as opposed to the bottom-mounted 8T ports. Can anyone measure their 8Ts' port length and Inside diameter to compare? My 8TL's ports are exactly 5" length X 2.25" ID.

smglbrth

5" length X 1 3/4" ID.

xschop

This makes sense and possibly how Polk got rid of the chuffing of 8Ts and had the 8TLs dig lower?

smglbrth

Ya got me, I wouldn't have a clue. I've never heard the 8TL so can't compare. However, when I went through mine head to toe, including the crossovers, there was absolutely no internal bracing of any kind. This surprised me some. The manual for the 8t states frequency response at, overall, 30Hz-26KHz. From what I can find on the TL it's 30Hz-25KHz, plus it's an 8 ohm speaker verses 6 ohm for the 8t.

xschop

Do you guys think that the plastic wave guide is still needed when installing RDO plates? The RDO plates have a tweeter throat wave-guide whereas the SL2500s just have a flat foam piece around dome. It is difficult to say whether the plastic glue-on plates have curved and went out of angle alignment over time....

xschop

Bueller....Bueller...

Can anyone double- check their factory plastic wave-guide angles? I'll be making a set out of billet and want the correct angle. Thanks