Seas 22TAFG and Monacor Waveguide Measurements

[Loiti]

Hi,

i am new to this forum and want to post my measurements of the Seas 22TAFG combined with the cheap Monacor Waveguide (WG-300).
First I'd like to say that nothing was calibrated, neither the soundcard nor the microphone.

Frequency Response without Waveguide (0°, 15°, 30°, 45°)


Frequency Response with Waveguide


THD without WG


THD with WG


After some easy editing, the Waveguide did easily fit to the Seas Tweeter!
I hope I get some comments about my measurements.

Best regards,
Stefan

[mgoedeke]

I'd recommend repeating the measurement with higher s/n as it seems a noisy as seen byt he level of the <1kHz nosie. The directivity is already evident is some respects, but the measurements don't tell one all that much yet. Doing such directivity measurements is best done at 1-2m ime so that one doesn't influence the relative values too much with simple geometric error.

Seems your system migth have a large wide-band peak centered above 10khz.

[owdi]

You need to increase the volume during your tests, and reduce the microphone input sensitivity. Try taking a measurement with the volume turned all the way down, and you'll see just how much background noise the mic is picking up.

Dan

[Loiti]

Hi,

yes there is much noise! But I am sure there will be no changes in the amplitude above 1kHz. I measured in a distance of 50cm (20 inch?; 1,5 ft?).

The peak is only at 0 degrees (or due to a faulty measuring?), 15° work fine.

I think the Waveguide is usable for the Seas, isn't it?

Mfg
Stefan

[phase_accurate]

I think the Waveguide is usable for the Seas, isn't it?

How is the mechanical fit ? This waveguide is made for a 30 mm Monacor dome (which doesn't seem to be bad either BTW).

Regards

Charles

[Loiti]

So, I finally mounted the Waveguide to the Seas Tweeter, AND: It's very very easy, and cheap(!).
And I did some useful new measurements with gating.




Here you can see how easy it is to mount the Waveguide. You just need a metric screw thread with the size M4,0 x 15 and a fitting shim (I hope you understand my english )


Fits well after some grinding.


A nice picture for the archive

And finally, the measurement:


Before you say: That looks ugly, well it does at 0°. But it looks fine at 15° (remind the amplitude above 10kHz is also between 3dB!). Also keep in mind that my soundcard was not calibrated, so the amplitude begins to fall very early (much before 20kHz).

Costs: WG-300 (Monacor): 7 EUR, some screws: <0,5 EUR.

I hope I helped someone with this thread and I want some Feedback!



Mfg Stefan

[phase_accurate]

Here you can see how easy it is to mount the Waveguide. You just need a metric screw thread with the size M4,0 x 15 and a fitting shim (I hope you understand my english )

That is the less important part of the mounting question. More important is the mechanical matching and acoustical discontinuities at the THROAT. These can lead to severe response irregularities (but don't necessarily have to of course).
The hole at 10 kHz could be caused by such an irregularity. The original (cheap) Monacor dome doesn't show this behaviour in this waveguide.


Regards

Charles

[mgoedeke]

That is a bit more information. On axis reveals some diffraction effects and not quite optimal coupling to the WG above 6kHz, a common problem with domes terminating into a WG. It does however seem useable and an axisymmetric WG will generally have some form of artefact on axis.

[mgoedeke]

@phase accurate: It does, just over a narrower bandwidth and in the application for which it was meant originally it doesn't matter (small 2-way PA tops)

[Loiti]

Originally posted by phase_accurate


That is the less important part of the mounting question. More important is the mechanical matching and acoustical discontinuities at the THROAT. These can lead to severe response irregularities (but don't necessarily have to of course).
The hole at 10 kHz could be caused by such an irregularity.

So what do you want to know? You can see everything you need at the frequency response. Yes, probably the 10kHz dip is caused of acoustival discontinuities at the throat. But I don't care, because If I had to choose wether I spend a LOT of time solving this problem or just listen to it at 15° or above, I would choose the last possibility.

Regards, Stefan