SDA/RTA efficiency

[i4gotmyid]

does anyone know the efficiency of the following models:

SDA CRS+ blade/blade model
SDA 1c Studio
SDA SRS 2.3
RTA 11T
RTA 12c

I believe the 2.3 was like 87dbl/w but the other two i am not sure of.

any help would be nice

[DarqueKnight]

All of these efficiency specs come from Polk brochures:

SDA CRS+ blade/blade model-- 92dB
SDA 1c Studio----------------------90db
SDA SRS 2.3------------------------90dB or 91dB**
RTA 11T -----------------------------90dB
RTA 12c------------------------------92dB


**I have two Polk brochures which contain the SDA SRS 2.3. One gives the efficiency of the SDA SRS 2.3 as 90 dB and the other gives the efficiency as 91 dB. Both figures may be accurate depending on when a particular set of speakers were manufactured.

My owner's manual for the SRS 2.3 does not list a figure for efficiency in the specifications!!

[i4gotmyid]

If this is for

each individual speaker or for the pair
in an real room or freestanding space measurement

[DarqueKnight]

Well, the industry "standard" way of measuring efficiency is in an anechoic chamber with a calibrated microphone one meter in front of one speaker, with the speaker given one watt of input.

However, speaker efficiency ratings, like amplifier power ratings, are arrived at by different means by different manufacturers.

Ken Swauger in Polk's customer service department should be able to tell you how Polk measures efficiency for their speakers.

[i4gotmyid]

I read elsewhere that the 1C's were 92dbs is that the "home" version? and the studio's were 90dbs? If there is a difference, does that mean that the studio and home version were not the same speaker?

[DarqueKnight]

The SDA 1B had an efficiency of 92 dB. I have never seen a listed efficiency rating of 92 dB for the 1C in any of the Polk literature.

The only difference between the "studio" version 1C and the "home" version 1C was the cabinet exteriors. The studio version was clad in black vinyl and had no oak end caps. The home version had heavy, 1 inch thick solid oak caps on the tops and bottoms of the cabinets. The home 1C weighed 100 pounds per speaker and the
studio 1C weighed 85 pounds. The two versions were identical with respect to drivers and crossover components.

[i4gotmyid]

i thought so...i automatically thought that guy was wrong cause if anyone knows its you, but i thought i would check with you to make sure.

so the 20lbs diff is the oak end caps and cloth? thats some heavy end caps.

[DarqueKnight]

Originally posted by i4gotmyid
so the 20lbs diff is the oak end caps and cloth? thats some heavy end caps.

There is only 15 lbs difference between the home and studio version.

You bring up an interesting question. I did the following exercise to see if the end caps of the 1C could account for the total weight differential.

Dry oak has a weight of 59 lbs per cubic foot. If we take a solid oak cube of one cubic foot and slice it into 12 one inch thick boards measuring 12 inches by 12 inches, each individual board would weigh 4.92 pounds (59 divided by 12). Each board would have a volume of 144 cubic inches.

The oak end caps of an SDA 1C speaker measures 1 inch by 11.5 inches by 16.5 inches, which equals 189.75 cubic inches. Therefore, the 1C end caps are 32% greater in volume than a 1" x 12" x 12" board.

Multiplying 4.92 pounds by 1.32 gives 6.49 pounds for an unfinished SDA 1C end cap. Two of these unfinished caps would add 12.98 pounds to a 1C cabinet. I assume the other 2.02 pounds can be accounted for by the eight large metal bolts (4 on top and 4 on bottom), the several coats of stain and finish on each end cap, and the additional cloth on the sides of cabinet.

[F1nut]

Raife,

You really have to much time on your hands.....;)

FWIW, I noticed on Doro's 1C's that Polk applied the end caps and side boards (for the cloth) right over the black vinyl. Those side boards have to weigh a pound each, it adds up quickly.

[DarqueKnight]

Originally posted by F1nut
Raife,

You really have to much time on your hands.....;)

You're absolutely right. I'm off from work until Jan 12th, 2004! :D

[F1nut]

Ah, that explains it! The amp is on it's way, you'll have plenty of time to listen and enjoy it.

[i4gotmyid]

man you are awesome