Vifa PL18WO-09-08, MTM - diyAudio
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Old 19th June 2003, 02:01 AM   #1
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Default Vifa PL18WO-09-08, MTM

I want to use the Vifa Pl18WO-09-08 in a MTM configuration. I noticed that the Vas is 13L which is pretty small. What will be the optimum Vb for this driver in a MTM config.

Does the MTM config affect the Volume of the box?

Thanks
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Old 19th June 2003, 01:35 PM   #2
Nisbeth is offline Nisbeth  Denmark
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For a finished, recognised design using the PL18 in an MTM, try looking at the "Eros" and the "Eros mkII" (different crossover) here:

/U.
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Old 6th July 2014, 02:33 AM   #3
vglaso is offline vglaso  United States
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I've been gifted w/4 vifa pl18woo9 and 2 scanspeak tweeters- The eros design, I can not find? Does anyone have it, and can share w/me? have tried my best to find it, however, am blocked, or, it's gone? my email is vglaso@basicisp.net. Am trying to help a friend- (or any design using same 8 ohm woofer and a scanspeak 9300, ) crossover and box volume? anyone? thank you-
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Old 6th July 2014, 08:04 AM   #4
Nisbeth is offline Nisbeth  Denmark
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Well, the thread is 11 years old...

I am not sure where you have looked, but the MK II Xover schematic was reposted here: Eros MKII crossover

/U.
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Old 6th July 2014, 10:40 AM   #5
system7 is offline system7  United Kingdom
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Quote:
Originally Posted by vglaso View Post
I've been gifted w/4 vifa pl18woo9 and 2 scanspeak tweeters- The eros design, I can not find? Does anyone have it, and can share w/me? have tried my best to find it, however, am blocked, or, it's gone? my email is vglaso@basicisp.net. Am trying to help a friend- (or any design using same 8 ohm woofer and a scanspeak 9300, ) crossover and box volume? anyone? thank you-
The Vifa PL18WO-09-08 Woofer has a Qts of 0.34 and a Vas of 25 litres. That says a reflex box of 0.75 Cu Feet in your quaint old American units.

A series filter simply doesn't work without time alignment or some other clever tricks, which can't be applied to a 6" bass anyway. In fact the "Eros" filter was one of the awfullest things I have ever seen. No phase alignment whatsoever, it gets no "love" from me!

Below is a filter that should work very well with the two drive units. I won't consider an MTM because that is another fashionable but broken design. You can adjust the attenuator for level on the tweeter to taste. This approximates a 2.2kHz LR4 filter, with a 6kHz woofer notch suitable for the woofer's worst cone resonance, for the technically minded.

You can tune the bass reflex tube length with some sort of online calculator.

Should sound very nice. Hope it helps, and feel free to ask further questions.
Attached Images
File Type: jpg Dayton 22L or 0.75 Cu Foot.JPG (27.8 KB, 197 views)
File Type: png Vifa PL18WO-09-08 Woofer.PNG (7.3 KB, 195 views)
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Well, there it is! Best regards from Steve in Portsmouth, UK.
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Old 6th July 2014, 10:58 PM   #6
Dissi is offline Dissi  Switzerland
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Default Eros MK II

I couldn't find the construction plans of the Eros MK II, they seem to have disappeared. Nevertheless I was able to do a simulation based on pictures on the net. If polarity of woofer or tweeter is reversed then the frequency response at 3 m is very flat. My only concern is the tweeter, which gets way too much low frequencies IMO.
Attached Images
File Type: jpg SimulationErosMKII.jpg (113.9 KB, 180 views)
File Type: jpg CrossoverErosMKII.jpg (63.5 KB, 176 views)
File Type: jpg DriverVoltagesErosMKII.jpg (109.8 KB, 176 views)
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Old 7th July 2014, 12:32 AM   #7
system7 is offline system7  United Kingdom
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I did the sim too, Dissi. I've still got things to learn about series filters, but the "Eros" is broken on a flat baffle if only on phase. Your comments about the low crossover make sense too.

Actually there is some nice phase alignment lurking if you time align it by setting the tweeter back 2.2cm. But it's still broken on tweeter distortion from the silly low and shallow crossover.

How long do we have to endure these stupid designs?
Attached Images
File Type: png Eros Time Aligned 2.2cm.PNG (21.9 KB, 25 views)
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Well, there it is! Best regards from Steve in Portsmouth, UK.
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Old 7th July 2014, 12:49 PM   #8
Dissi is offline Dissi  Switzerland
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Originally Posted by system7 View Post
How long do we have to endure these stupid designs?
Besides the tweeter issue there is nothing wrong with the Eros MK II. The speaker gets very positive reviews by most of the owners.

There's absolutely no reason to call it a "stupid design" or "one of the awfullest things I have ever seen". Steve, you really shouldn't simulate a tweeter with Fs of 550 Hz by one having Fs at 1700 Hz and then conclude on the phase response!
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Old 7th July 2014, 01:08 PM   #9
system7 is offline system7  United Kingdom
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Well, I think somebody has to call out the rotten designs that abound. It's not enough to say "Dude, I got a series filter!" Most people must be deaf, considering some of the designs they rate as good IMO!

But what phase did you get with a different tweeter on flat baffle? I tried loads. They were all about 90 degrees out around crossover. I'm open to the science, which always wins in the end! And good phase alignment really matters to integrate drivers.

I can get a bit rude sometimes I suppose. But science is no place for feelings. The physics does what it does, regardless of your feelings.
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Old 7th July 2014, 04:35 PM   #10
Dissi is offline Dissi  Switzerland
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Originally Posted by system7 View Post
But what phase did you get with a different tweeter on flat baffle?
According to my simulation there's a slight phase match error of 20-30 degrees, but that's acceptable IMO. Please consider that the result is not necessarily very accurate, because the exact location of the acoustic center of a driver actually is hard to predict.
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File Type: jpg PhaseErosMKII.jpg (113.3 KB, 14 views)
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