Inexpensive wavguide for 1" drivers

On the tail of the excellent work published by Zilch and others, I've been testing a cheapo waveguide that might be of interest.

MCM sell a $10 circular 6.5" waveguide that fits on 1" screw mount compression drivers. Part number 54-580. http://www.mcminone.com/product.asp?...%5Fid=54%2D580

It works very well with a nominal directivity of 90 degrees circular.
Cut-off frequency is about 1.5kHz and it starts to lose direction control below about 2.5kHz although still useable down to a least 2kHz. Could be a good option for something like a 2407 driver.

Note that some rough EQ has been added to the on axis response to make it easier to see the what's happening.

Cheers,
Ralph.

There are similar devices on Parts Express.

Ian

I'm always a little confused when doing similar testing.

The specs are usually "included" angle, i.e., "90°" being +/- 45° from axis.

Is your 45° "off-axis" or included angle?

Nice measurements, in any case. :thmbsup:

Hi Zilch,


My plots show the degrees off axis, so the 45 degree plot has an included angle of 90 degrees.

Cheers,
Ralph

What's the "rough EQ" entail? Top end lift? Could you post a curve of on-axis without the EQ?

Looks like a pretty "linear" curve, though. No real discontinuities. Very good performance, from that standpoint...

Regards,
Gordon.

Let's try and guess the driver Ralph used from the curve.

Not a 2407, apparently.

Zilch guesses 2416 or 2426.

Only one? 2426, then.... ;)

Zilch is right on the money. 2426 with the snout removed.

I can't offer a plot of the driver plus waveguide before EQ.

The purpose of the tests were just to get an idea of the off-axis response of the wave guide. I wasn't too worried about the actual frequency response, just how it changed as I measured at increasing angles.

But I can give you the EQ settings I used with my driverack:

MCM waveguide on 2426 with baffle approximately 270mm x 500mm.
Equalised for flat on axis. Measurement distance= 0.5m, 1/24th smooth.
EQ: HP Shelf 5.6kHz, 10.5dB, S=9; 2.12kHz, 6dB, Q=1.57;
3.15kHz=-3.5dB, 4kHz= +3.5dB, 5kHz= -1dB, from here just tried to add HF boost as the HF Shelf ran out of gain, 10kHz= +0.5dB, 12.5kHz= +2.5dB, 16kHz= +6dB.

From my notes it says I ran out of parametric HF EQ and so I just boosted a bunch of frequencies in the top octave with the graphic. Hence the response is a bit rougher than could be achieved with more parametric bands.

Below is the on axis response on its own:

The response isn't as smooth as the first plot I posted 'cause it doesn't have as much smoothing, 1/24th octave vs 1/6th octave.

Here is the original set of plots with the same 1/24th octave smoothing applied.

Cheers,
Ralph