A problem (or not) with Scan-Speak 9500, please help

[Misa A.]

Hello, good people at DIYAudio.

I need to clarify one little question, which confuses me.

I am building myself a pair of good speakers, 2 x Scan-Speak 8545 and 9500 in MTM configuration, like a North Creek Rhythm, but in a TL cabinet similar to the Seas Thor.
Unfortunately I don’t have a pre-designed crossover schematic so I have to do all the work myself. I built the Eric Wallin’s microphone preamp, bought a couple of Panasonic WM-62A mikes, put together a jig and so on.

After I measured speakers’ impedance and in cabinet SPL characteristics, I got the graphs for a Scan Speak 9500 tweeter shown below. The SPL curve shown is valid in the range above 400-500 Hz due to a small size of my room.

I know that a lot of people use this tweeter in their designs and want to ask one simple question:
is such a sharp resonance at about 1.8 kHz, right in the crossover range, normal for this driver, which is considered by everybody to be one of the best?

Both of my drivers have the same problem. This nasty 7 db SPL hump at this frequency makes crossover design much more complicated.

For you to understand my concern, I can say that these tweeters are being sold here in Moscow for 122 Euro, which is today $156 a piece, $312 a pair.

So, is this normal and I should go ahead with crossover design applying notch filters, or I should ask guys I bought them from for replacement? Or after some run in time things will improve?

Thank you in advance for your replies.

Misha

[Misa A.]

Here are the graphs

[PHilgeman]

It is likely that it is due to your baffle width, and some sort of diffraction effect.

Your measurements did not show up.

It sounds like you are really going for broke with this speaker. I would definitely think about some large roundovers on the edges of the speaker. They can really help reduce diffraction effects.

-Paul Hilgeman

[Misa A.]

Paul, I attached graphs twice, saw them on prewiew...

The baffle width is 23 cm with edges rounded with 1/2" radius.
Impedance measurements in free space show exactly the same secondary resonance peak.

OK, thank you for reply, i am trying to attach pictures for the 3rd time

Misha

[Misa A.]

The graphs

[Misa A.]

Why do I see attached pic on preview and it dissapears every time my post appears in forum? Is it moderation or a techical problem? I reduced it's size to 50 kB..

[Misa A.]

One more time

[Misa A.]

OK, the question is:
Has anybody who measured a Scan-Speak 9500 tweeter got such a picture?