Cone breakup questions

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Hi,


Measurements can only be done gated nearfield typically, so the bass
end and BSC is usually simulated, further up you need to verify the
accuracy of the measurement process so not to be led astray.

http://focus.ti.com/docs/toolsw/folders/print/tina-ti.html

On the first page, post #4, I described the testing environment.

Distance 1 meter (39inches)
Time: 5ms

Each driver measured separately with existing crossovers wide open (without attenuation)


Are you suggesting this measurement isnt sufficient and I need another?
 
Here are the woofer specs since this it seems a bit unknown.

AC10R



Nominal Diameter: 10"

Impedance: 8 ohms

Range: 24-2kHz

RMS Power: 150 watts

System Power: 200 watts

Sensitivity: 89 db

Magnet mass: 1134 grams

BL: 12.12 Tm

Fs: 24 Hz

Qms: 3.978

Qes: .420

Qts: .380

Vas: 111 liters

Cms: 654.4944

Mms: 60.7277 grams

Mmd: 57.0430 grams

Xmax (linear one way): 7.68 mm

voice Coil Diameter: 2"

Voice Coil Height: 24.89 mm

Air Gap Height: 9.525 mm

Voice Coil Inductance: 1.7 mh

Voice coil Resistance: 6.45 ohms

RC Cap: 33

RC Resistor: 7.0
 
Hi,

You tell me. If its true shouldn't be hard to find a similar example,
or a x/o that addresses the same issue. If you can't then one
might suspect your own data / methods / assumptions.

rgds, sreten.

I did want to thank you for all those links and your explanations on the previous page. I will definitely look into those, although some of those I have already seen and read.

What do you mean by looking for a similar example or a x/o that addresses the same? Its not clear to me what you are suggesting.
 
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The peak starts to develop around 1200hz.
The dip at 1200Hz may be a part of the breakup process as well (your plots do have something else going on (perhaps some diffraction?) but I'll assume the peaks shown are breakup like you say).

I have an example here. The woofer shown has two peaks (500Hz and 1kHz) and a dip like yours (most likely for the same reasons). The extra issues at 2kHz are just a bonus ;).

It's obvious I didn't try very hard but using the dip to my advantage, achieved a close to useable crossover for it with not even a second order filter. The blue trace is a fourth order target.
 

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What do you mean by looking for a similar example or a x/o that
addresses the same? Its not clear to me what you are suggesting.

Hi,

Is always good to find someone else has also found a problem
you think you have, but info on the D54 is very thin on the ground.

I don't know what to make of measurements of what is supposed
to be a quality 2" mid-dome that implies it falls off ~ 15dB over the
two main octaves of its working range and then peaks up before
its final roll-off. I'm just advising caution regarding the measurements.

rgds, sreten.
 
Hi,

Is always good to find someone else has also found a problem
you think you have, but info on the D54 is very thin on the ground.

I don't know what to make of measurements of what is supposed
to be a quality 2" mid-dome that implies it falls off ~ 15dB over the
two main octaves of its working range and then peaks up before
its final roll-off. I'm just advising caution regarding the measurements.

It might also be worth noting that I used 1/24th octave smoothing on my tests. Obviously, the graphs would look smoother at 1/3 or 1/6th.

rgds, sreten.

I believe what you are seeing is the result of cabinet issues. I am in the midst of modifying/rebuilding the cabinets.

An externally hosted image should be here but it was not working when we last tested it.


This was the configuration. A RTR 300d. i bought these back in 1983 and in the early 90's replaced the drivers with what I have outlined. This is NOT a picture of my actual speaker, but gives you a framework for how the drivers were arranged on the front baffle. Not a great arrangement huh? Well, I am attending to this by building a completely new front baffle and aligning the drivers vertically with the tweet on top, the mid below, the the dual woofers below that.

It might also be worth noting i used 1/24th octave smoothing for my testing. Obviously the graph would look smoother at 1/3 or 1/6th. I dont know what others typically use in this regard.
 
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I'd say your RTR 300D is rather WELL laid out, as it goes. D'appolito arrangement at heart. Closed Box would be no bad thing either. :)

Have you broken down the original RTR crossover? That's gotta be the way out of this hole you have dug for yourself. Much easier to modify it for new drivers surely?

Onto your drivers. You now have all the inductance and Re data to calculate the Zobels. Here's your midrange:

An externally hosted image should be here but it was not working when we last tested it.


Seems to say 2kHz centre frequency to me. Use it over a very narrow range too. Say 1-4kHz. Gonna need fairly steep filters too, because it's not my idea of a great driver.

The rest, surely, is routine. ;)

An externally hosted image should be here but it was not working when we last tested it.
 
I'd say your RTR 300D is rather WELL laid out, as it goes. D'appolito arrangement at heart. Closed Box would be no bad thing either. :)

Have you broken down the original RTR crossover? That's gotta be the way out of this hole you have dug for yourself. Much easier to modify it for new drivers surely?

Onto your drivers. You now have all the inductance and Re data to calculate the Zobels. Here's your midrange:

An externally hosted image should be here but it was not working when we last tested it.


Seems to say 2kHz centre frequency to me. Use it over a very narrow range too. Say 1-4kHz. Gonna need fairly steep filters too, because it's not my idea of a great driver.

The rest, surely, is routine. ;)

An externally hosted image should be here but it was not working when we last tested it.

Oh yes, the original RTR x overs were scraped immediately. I agree that a opporating range of about 1-4k is about right. Maybe 900-3.5k. Yes, I have the dynaudio data sheets. I also have them for my woofers.

My minimalistic crossover for the mids is/was a .4mh coil and a 50 uf cap with a zobel. I tend to agree with you that now I need to go steeper than a 1st order network.
 
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Maybe using a higher Q second order high pass to fill in the mid dip below 1kHz to extend the useful range?

Currently (assuming you have 5 components on zobel duty) your 50uF and 0m4H should be giving you a lower f3 at around fs so I'd assume you have much to gain from this.
 
Jim, I think you want to get modelling this Symphonie visaton design. The dome midrange is VERY similar to yours. Fs 500Hz, Le 0.16. Layout almost identical.

Visaton - Lautsprecher und Zubehör, Loudspeakers and Accessories

The bass arrangement is optional here. It's a 3.5 design, as it goes. You can change it to suit. It'll let you see what goes on when you change the crossover frequencies. You've got flexibility on the crossover between the two domes too. You might get away with a lower order there.

You should get to know your drivers like the back of your hand after a while. :)
 
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