Woofer Diameters, for Pete B.

[kkantor]

Pete,

Per your email, I have measured the cone diameter of a 303a woofer and an NHT 1259. This was just a ruler/eyeball measurement, made from halfway across the surround roll. As such, it will differ somewhat from effective acoustical radiating area, and is also probably not reliable down to the mm. But, I did measure both at the same time, and so my guestimation error is probably close in both cases.

303a woofer:

diameter = 253mm

Sd = 502.7cm^2

NHT 1259 woofer:

diameter = 251mm

Sd = 494.8cm^2

This conforms pretty well to the published data on the 1259, which I did not look at before I did the measurement. On the other hand, my recent measurement of the 303a Sd is much higher than what is shown in the Klippel report I have on my website. Though I did the response measurements and basic SSP's in this data package myself, I did not do the Klippel work. I will ask the tech who did the Klippeling how the Sd number was derived.

-k

[Pete B]

>Pete,

>

>Per your email, I have measured the cone diameter of a 303a

>woofer and an NHT 1259. This was just a ruler/eyeball

>measurement, made from halfway across the surround roll. As

>such, it will differ somewhat from effective acoustical

>radiating area, and is also probably not reliable down to the

>mm. But, I did measure both at the same time, and so my

>guestimation error is probably close in both cases.

>

>303a woofer:

>

>diameter = 253mm

>

>Sd = 502.7cm^2

>

>NHT 1259 woofer:

>

>diameter = 251mm

>

>Sd = 494.8cm^2

>

>

>This conforms pretty well to the published data on the 1259,

>which I did not look at before I did the measurement. On the

>other hand, my recent measurement of the 303a Sd is much

>higher than what is shown in the Klippel report I have on my

>website. Though I did the response measurements and basic

>SSP's in this data package myself, I did not do the Klippel

>work. I will ask the tech who did the Klippeling how the Sd

>number was derived.

>

>-k

Thanks Ken,

I have a 1259 here and I get about the same number measured as you do with a ruler half way across the surround.

I was concerned about the 303 Sd number because it is especially important when the test box method is used for the derived T&S parameters.

Here's what I measure for the 200003s:

Cone Diameter 1/2roll -1/2roll Sd

200003 8-1/2" 9-1/8" 422.0 cm^2

Most of the 200003s were listed as 450 cm^2 in the measurements of Bret's 200003s, not too different from 422 but it does effect the mass calculation when the test box method is used. The 303 woofer was listed as 416 cm^2 and I wonder if this should have been the 200003 value.

Thanks again for confirming and looking into this.

Pete B.