Waveguides and horns

[_Wim_]

CAD drawing of DE250 based on measuring them with the calipers. It was hard to measure the exit tube, so that is the least accurate part - a shame because it is also the most useful part!

Many thanks. I was indeed also looking for the exit shape, but you drawing if already much better then what I could do myself...

 

[jzagaja]

First comparison - 12" OS waveguide without baffle, original driver and membrane with strong breakup (titanium), "faulty" Fresnel phase plug with low compression. Simulation - ideal flat diaphragm and wavefront.

 

[jzagaja]

Same with 18sound NSD1095N diaphragm.

 

[jzagaja]

4-slit Fresnel phase plug with conventional Ti diaphragm.

 

[gedlee]

Jacik

I fear that you might be missing something critical in this analysis. You will not see any effect of the phase plug until you have a waveguide that shows little to no internal reflections and diffraction. In other words, the phase plug is not a limiting factor until the waveguide approaches almost ideal characteristics. The waveguide used here is not very "clean" and it will obscure what you are looking for.

I think that I have made this point on several occasions in the past.

 

[jzagaja]

Like I said it's for fun Waveguide is without baffle and radius at mouth is ca. 2".

 

[jzagaja]

Same with NSD1095N. Please note that 18sound uses deeper dome profile.

 

[rajacat]

Good work! Looks like there's a smoother response with a little better directivity, if I'm reading the graph properly. Going into production soon?

 

[jzagaja]

I'm checking possibility on BC DE250.

 

[rajacat]

I've never heard the BC DE250 but I gather that most find it competent and very smooth. Some complain that it's little shy of detail and high freq. extension. It would be great if your design would help in those areas.

 

[noah katz]

I'm checking possibility on BC DE250.

That would be great; there should be a lot of demand from the many I expect who will be using the DE250 on all the SEOS WG's soon to be available.

Will this be a simple retrofit?

 

[Defo]

Is the E-JMLC in the picture below really 92 cm wide? Sure doesn't look like it considering the iwata one is 59

 

[jzagaja]

Yes they are 92cm wide and doesn't destroy space around. I have them in my living room, impressive looking horns.

 

[_Wim_]

Some complain that it's little shy of detail and high freq. extension. It would be great if your design would help in those areas.

Look at the measurement I have taken of my DE250 combined with an OS12 waveguide + foam plug from Geddes.
I does not lack any high frequency extension. I think people often mistake high frequency resonances for "detail", and if they here a system without, they say it lacks "detail"...
The measurement is taken with a 10ohm resistor in parallel with a 1µF capacitor to correct the roll off from the waveguide. No other equalizing is applied in this measurement.
For listening, I use a DCX2496 to correct the bumps at 2.2kHz,4.4kHz and 16kHz, the roll off correction is done passively with the 10ohm/1µF to avoid big boosts in the DCX.
Off coarse the correction of the bumps could also be done passively with 3 notch filters, but since I have an active system, it was easier in the DCX...
Overall I think this combination sound very good, but I am also interested in the phase plug to see what the effect is.

 

[jzagaja]

BC DE250 compared to previous. It seems when phase plug curvature is much different (radius is larger) than of diaphragm then HF rolloff is higher. Polars are made of using 30 frequencies.

 

[jzagaja]

Sonograms: 18sound vs. DE250
SPL 20deg: BMS 4550 vs. DE250
SEOS-15 with BMS 4550

 

[jzagaja]

Let's do 5-slit plug for DE250.

 

[gedlee]

Ouch!! That's a disater waiting to happen. You need to rethink that plug! The long channels with no flare is not a good idea.

What you need to look at is the DE500. Not my preference from a materials standpoint, but its short throat would lend itself very well to this modified phase plug.

 

[jzagaja]

Problem with ferrite drivers is long path (with low flare rate) from diaphragm to the exit aperture. I have to choices:

1) Remove some material like I did before so that phasing plug flare rate is slower.

2) Leave as is - see below

 

[gedlee]

Well neither is ideal and this is where "development" comes into play. You need to build them and test them and find out what the pros and cons are. The DE250 just may not be a good choice.