K-55 sensitivity rating?

[Blvdre]

Can anyone tell me what the sensitivity rating for the k-55 is (1W, 1M)? I'm finishing up a pair of Al's gentle slopes for my 902 /511/ lascala bass combo, and would like to get a ballpark on my autoformer setting. Tried the search, no dice.

[Guest " "]

see attached

SL2.1551.PDF

SL2.1551.PDF

[Blvdre]

Thanks SF, just what I was looking for.

[WMcD]

Note that the spl's given there are on a plane wave tube. In such a set-up the microphone is just next to the output of the driver (roughly the throat of a horn). Of course that makes it very loud. The drive level, for this reason, is 1 mV (1/1000th of a volt). The bottom line is that this does not tell you the spl when you put a microphone 1 meter away from the mouth of a horn (at 2.828 volts).

OTOH, there is a listing on that spec sheet of other sheets for the output of various horns. You'll have to search around the Atlas website. This may or may not be similar to your horn.

Wm McD

[Blvdre]

Thanks for the clarification, Gil. Since I'm using the autoformer to adjust the high-end attenuation, and have several options (taps), I just wanted a ball-park starting point. One x-over's done, so I'll hook it up today and see how it sounds.

[WMcD]

Sorry if I was a bit of a stickler there.

I would think the -3 dB tap is a very good start.

= = = = =

I was a stickler because decriptions of frequency response of drivers are sometimes stated as plus or minus X dB from Y to Z Hz, as you see in Parts Express. That is pretty much inaccurate, or not enough information, unless you know more.

Actually, the Atlas sheet and ones like it, are accurate about response on a plane wave tube.

But it doesn't tell you about response on a given horn.

The other good specs show the response of a named horn with a named driver. But you have to read carefully regarding whether there is any electrical equalization used when any plots or specs are given.

If I may continue. It is really a matter that the horn affects the ultimate frequency response.

The acoustic output of the horn with a given driver at the low end is controlled by the Fc of the horn.

The high end depends on the directionality of the horn. The acoustic pattern narrows down and gives some on-axis gain. (Constant directivity horns are somewhat of an exception. )

The narrowing of the pattern (and gain) allows people to claim a given driver has response up to, say, 6000, or even 15,000 Hz. What they are not telling you is that the horn used is giving the HF gain.

Wm McD

[Blvdre]

Stickler? There's nothing wrong with that (my reply did read a bit flippant, not intentional). I appreciate your insight into the various approaches to measuring sensitivity, and the part the horn plays. Specs can certainly be misleading if the test criteria and conditions aren't clearly defined.

[djk]

Use the -6dB tap if the 902s are 8 ohms.

[Blvdre]

Use the -6dB tap if the 902s are 8 ohms.

That they are. Thanks djk .