Tweeter front plate design

[YSDR]

Well now, I was about to build something just like this, almost a cheaper DXT mon if you will, but it's good to hear some feedback on the idea. Guess I will pass.

I experimented several popular, highly regarded tweeters before like the famous Scan-Speak D3004/6600 AirCirc for example but I was not happy with any of them (I mean how they sounded in the complete system). Recently I tried that cheap, wg loaded Dayton soft dome and wow, one of the best tweeter that I've ever heard. I would choose this over the soft dome SS AirCirc any day.

Just try to find a cleaner waterfall or sonogram plot above 2 kHz amongst the tweeters on the site below! You won't succeed.
https://www.dibirama.altervista.org...n-audio-nd25fw-4-tweeter-1-4-ohm-40-wmax.html

 

[mv8]

Well now, I was about to build something just like this, almost a cheaper DXT mon if you will, but it's good to hear some feedback on the idea. Guess I will pass.

The Dayton tweeter costs about $20, and at that price it's really hard to point out any flaws. If someone wants to build a low-cost project like the DXT-Mon, I can recommend this Tweeter.

I built an even slightly larger monitor, with two Sba midwoofers and the same Dayton. A dozen people listened to the project and were impressed by how such cheap speakers can offer sound at a very decent level.

 

[Artyaya]

Have you ever wondered why the tweeter front plate design is somehow the same and yet different and if these small differences matter at all? Some tweeter front plate are just flat, some have something like tiny little wave-guides or "lenses" integrated,...
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I would like to try, to show here with a few simple simulations, what certain changes of the tweeter front plate cause. For this purpose we simulate an ideal 1'' tweeter with about 700Hz resonant frequency fs.

1) Flat front plate
Let's start with the tweeter dome on an infinite baffle. So the tweeter front plate is simply a flat plate.
First the sketch (lateral cutaway drawing of the tweeter dome), then the frequency responses from 0° to 80° (in 10° steps) on infinite baffle (IB) of the dome on a flat front plate and then those normalized to on-axis frequency response:
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2) Front plate with 3mm step
Next we introduce a 3mm high step (I use the term "step" because it looks like a step in the lateral cutaway drawing of the tweeter dome), one could also say the tweeter has 3mm off-set/recess to the front plate. It is a tiny wave-guide which on-axis contributes to an increase of the SPL of the high frequencies and at the same time makes the radiation less wide.
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3) Front plate with 2mm + 1mm steps
Instead of just a big 3mm step, we round the corner a bit. The diameter of the tiny WG remains unchanged.
The radiation becomes minimally narrower, but more uniform above 15kHz.
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Something like this is what most tweeters have.


4) Front plate with 2mm + 1mm + 2mm steps
Let's add another step, creating a small wave-guide with 40mm diameter. In the 2-9kHz the on-axis SPL has increased. The radiation becomes a bit narrower.
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5) Front plate with 2mm + 1mm + 2mm + 3mm steps
The next step with a height of 3mm and a diameter of 70mm provides a wave-guide that most would recognize as such.
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If we now compare the normalized frequency responses of the tweeter with flat front plate with our 70mm WG, for example, at 80° radiation angle the frequency responses at 4kHz are offset by 2.5dB SPL.
View attachment 296771
The less wide dispersion in the frequency range 2-4kHz usually makes the transition to the woofer more even. However, there are other effects such as edge diffraction that are not discussed here.

6) Front plate with 2mm + 1mm + 2mm + 3mm steps and reflector
If you now want to straighten the on-axis frequency response up to almost 20kHz, you can add a reflector at the expense of radiation - this would look like a washer when viewed from above.
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If we now compare the frequency responses (deg0-80 in 10° steps) of the tweeter with flat front plate and the tweeter with the 70mm wave-guide with just 8mm height and reflector on IB, the differences are dramatic (same color, same angle):
View attachment 296772



To see the impact of each change in direct comparison, here is the FR as a series:

1) Flat front plate
2) Front plate with 3mm step
3) Front plate with 2mm + 1mm steps
4) Front plate with 2mm + 1mm + 2mm steps
5) Front plate with 2mm + 1mm + 2mm + 3mm steps
6) Front plate with 2mm + 1mm + 2mm + 3mm steps and reflector
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7) Front plate with "small lip" around the tweeter dome
See post#12 for more details.

8) Tweeter flush mounted but with gap around face plate?
See post#19 for more details.

Computer simulation brings us new perspectives.

The significance of waveguide horns should be understood from both strategic and tactical levels:

• Horns in stage loudspeakers: Primarily to increase sound pressure level and reduce the overlap of radiation patterns when using multiple loudspeakers.
• Waveguide horns in small loudspeakers: Primarily to reduce the impact of reflections from the walls of small rooms on the listening experience.

Your research is very meaningful for designing compensation circuits, thank you for your efforts.

Regardless of whether it's a large horn or a waveguide horn, inverse compensation of the frequency response curve should be performed in the circuit. Therefore, the curve distortion caused by the tweeter panel design should not be too complex, otherwise it will be difficult to design a compensation circuit.

Each compensation stage can only compensate for one slope. Each additional compensation stage will change the phase in the adjusted frequency band, which is not a problem for mono.

However, for stereo, too many cascaded compensation stages will lead to misalignment of the left and right phases due to the accumulation of component value errors, resulting in a blurred instrument focus.

The common tolerance for correction capacitors is 5%, and for other capacitors it is 10%, thus the compensation frequency will also shift by the same range.

 

[Artyaya]

In a home listening environment, I used to really like the waveguide horns of Genelec speakers.

However, in both Genelec 1031 and Behringer B203x speakers, there was surprisingly no inverse compensation in the circuit for the frequency response curve distortion caused by the waveguide horn.

Later, I discovered that complex horn designs can actually compensate for frequency response curve distortion, which is amazing! This means that compensation in the circuit is no longer needed.

If you have the opportunity, you could 3D scan JBL horns and input the data into computer simulations to see what happens. I look forward to that day.