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Multi-Way Conventional loudspeakers with crossovers

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Old 8th February 2017, 10:12 AM   #11
system7 is offline system7  United Kingdom
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There's not much to reverse engineering the Ariel electrical response. Interestingly, the impedance correction is not flat. This gives it a little bass boost and 2dB midrange presence at 2kHz. Which may be why it works better with valve amps.

If you put the Vifa DCR of 5.7R and Le of 0.7mH into an impedance correction calculator, you find that the bass shunt (and adjusted for parallel MTM) is just a near Zobel with half the theoretical capacitance. Which is what Lynn said it was.
Impedance Equalization (L-Pad) Circuit Designer / Calculator
Attached Images
File Type: png Reverse Engineer Ariel Electrical.PNG (13.8 KB, 313 views)
File Type: jpg ArielII_bass_crossover_Lynn_Olson.JPG (25.3 KB, 308 views)
File Type: jpg ArielII_tweeter_crossover_Lynn_Olson.JPG (22.9 KB, 306 views)
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Old 8th February 2017, 12:14 PM   #12
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To post #6: last time my workbench looked like that, was some 5 years ago ...
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Old 8th February 2017, 01:37 PM   #13
system7 is offline system7  United Kingdom
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Yes, I was impressed. It's industrial grade! Nice equipment too.

Most of my stuff is in tatty cardboard boxes...
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Old 9th February 2017, 05:36 AM   #14
rabbitz is offline rabbitz  Australia
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Quote:
Originally Posted by system7 View Post
Scott Blaier has harsh things to say about single cap crossovers
I agree with him but they can have their place in speaker design. The single cap idea was suggested early in the thread as a starter but it eventually went to 3 variations of standard series xo's and a AR series xo.
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Old 9th February 2017, 06:43 AM   #15
suzyj is offline suzyj  Australia
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Thanks for the analysis of the crossover Steve. I'm interested what you used to model the drivers? Simply a series LR circuit or something more involved?

I started reading up on driver modelling last night and my eyes rapidly glazed over. I'm just a simple engineer...
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Old 9th February 2017, 09:51 AM   #16
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"I remember reading, years ago, about your take on the AEM5000."

Oops, just checked your blog. It was the ETI5000 by David Tilbrook, which evolved to the AEM6000. Memory is a funny thing. Having said that; I see you are in Geraldton but weren't you in Sydney? I could be completely wrong here. If I'm right, they are world's apart, and not just geographically.
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Old 9th February 2017, 11:58 AM   #17
suzyj is offline suzyj  Australia
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Indeed I was. This whole power amp thing started with a trip to the work library looking for an old ETI article. When I couldn't find it I instead found the AEM articles describing the AEM6000, which led me on a rather pleasant design exercise.

The power amp I built from that is still running in my loungeroom, and hasn't missed a beat.

We've relocated from Sydney to Geraldton for work, as out here is where all the action is. I'm rather liking Geraldton after Sydney. We didn't have a snowball's hope of owning property in Sydney, not on my wage. Here in Geraldton we're looking at acreages
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Old 9th February 2017, 01:14 PM   #18
system7 is offline system7  United Kingdom
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Quote:
Originally Posted by suzyj View Post
Thanks for the analysis of the crossover Steve. I'm interested what you used to model the drivers? Simply a series LR circuit or something more involved?
I started reading up on driver modelling last night and my eyes rapidly glazed over. I'm just a simple engineer...
I think people make this stuff more complicated than it really is when they start talking about microphones and importing files.

I just used a similar 5" Le=0.6mH 8 ohm driver. The Visaton W130S, as it goes.

Boxsim is a very good simulator that an ordinary human being can get good results out of quickly:
Downloads
Import a similar project like this Couplet Light MTM into projekte folder, and you're in the right ball park already:
https://boxsim-db.de/couplet-light/

We don't have to reinvent the wheel in established territory like 5" MTM. It's easy, because 5" drivers are flat. 3kHz crossover.

Click the image to open in full size.
Seas CA15RLY X2 cabinet volume suggestions

Troels Gravesen does an easy MTM here:
Vifa PL14WJ-

Now, actually, he uses a very familiar design of 2nd order bass at 4 ohms, which is always near 1mH with 8-12uF shunt, and a third order tweeter. The second to fourth images are the SEAS CA15RLY idea we tried with a ribbon tweeter. The main thing is to have the right idea.

In practise, when you include the (0.3mH for parallel drivers, it would be 0.6mH for a single one) voicecoil inductance, the bass is the familiar 3rd order in 3:1 ratio, which lies deep in the maths of filtering. As is the tweeter filter at 1:3. This ends up an order higher than Lynn Olson's design on bass and treble. In practise, a filter has an impedance, and at 4 ohms, the capacitors get bigger, and the coils smaller than with 8 ohms. But they are otherwise the same idea.

The slopes are not entirely symmetrical to allow for very slight time alignment issues between the drivers, and keep phase aligned. An old trick.

BTW, you will notice the electrical response is steeper than than the mechanical response here. That is the bafflestep allowance for the box, which is needed unless you wall mount. In the real world with a cabinet the lower bass sort of disappears round the back of the baffle by 6dB (which is quarter power), whereas the mids go forward to you. If you want to appear wiser than you really mostly are, you might waffle about 2Pi space and 4Pi space and diffraction. Which always loses noobies completely.
Attached Images
File Type: jpg Troels Vifa PL14WJ-09-08 D'Appolito.JPG (35.7 KB, 269 views)
File Type: png MTM Electrical 2nd-3rd Order.PNG (7.9 KB, 44 views)
File Type: png MTM Ribbon Tweeter Easy Filter.PNG (7.3 KB, 36 views)
File Type: png MTM Ribbon Tweeter FR.PNG (16.9 KB, 46 views)
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Last edited by system7; 9th February 2017 at 01:43 PM.
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Old 9th February 2017, 03:57 PM   #19
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The Ariel crossover is 4th-order acoustic at 3.8 kHz, so adjust your active crossover accordingly. The tweeter will never need more than 20 watts, more likely 10 watts in the real world, so you might consider a Class A option for the HF amplifier.
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Old 9th February 2017, 04:09 PM   #20
chrisb is offline chrisb  Canada
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Can't get better advice than that on "modernizing?" this stellar design

Which raises the question - Lynn, for those of us with less time to wade through the noise of thousands of forum posts, could you share your opinion on the latest generations of very affordable DSP based crossover approaches? I almost said "solutions", but that might seem leading.
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