ATC SM75-150S off-axis response

[Tytte71]

The ATC SM75-150S is known to be a very good dome midrange and one of very few that is equipped with a waveguide from the factory.
AEROnet has proven very good off axis-response on is driver and have been my reference for measurements on it... until now. In September Zaph also measured this driver but got very different results with regards to the off-axis response.
I must admit that the AEROnet measurements looks almost to good to be truth when concidering the size of the waveguide. Does anyone have done other measurements on the ATC SM75-150S or have an explanation to the difference between the two measurements?

Best Regards,

[ShinOBIWAN]

They look consistent to me.

Ralph gain shifted his measurements for clarity in case you were confused about the level differences at various angles he tested. If you were to normalise them then you'd see pretty much the same trends as Zaphs barring some minor frequency response deviation that could be anything from batch number to the test baffle.

I used the ATC mid about 5 years ago and both sets of measurements are pretty much what I remember even down to the blip at 4.5Khz.

[Tytte71]

Originally Posted by ShinOBIWAN

They look consistent to me.

Ralph gain shifted his measurements for clarity in case you were confused about the level differences at various angles he tested. If you were to normalise them then you'd see pretty much the same trends as Zaphs barring some minor frequency response deviation that could be anything from batch number to the test baffle.

I used the ATC mid about 5 years ago and both sets of measurements are pretty much what I remember even down to the blip at 4.5Khz.

Thanks ShinOBIWAN, I hoped for you to answer this
I might have misunderstood both Ralph's and your explanation here, but in Ralp's measurement is shows a pretty much an ideal off-axis response down to about 400Hz, while in Zaphs' measurements the dispersion control ends at 1kHz. That's what confuses me.

Best Regards,

[ShinOBIWAN]

I can't remember if Ralph had the earlier straight profile waveguide version or the current curved profile.

Its could explain the slight differences and Ralph did those measurement about 5-6years ago now if I remember so that may be the case.

[Tytte71]

Originally Posted by ShinOBIWAN

I can't remember if Ralph had the earlier straight profile waveguide version or the current curved profile.

Its could explain the slight differences and Ralph did those measurement about 5-6years ago now if I remember so that may be the case.

I don't see why the WG profile change should make such (big) difference in the lower frequency region.
Could it be that Ralph have done the measurements with the driver baffle mounted, while Zaph has measured the raw driver?

[Tytte71]

I was thinking contacting Ralph (AERONet) and John (Zaph Audio) for clarification on measuring setup, but can not find the contact details on their web pages. Anyone that can help me here?