Has anyone heard this driver?

SteveG

Account Disabled
2002-01-07 7:20 pm
Newton Falls, Ohio
Vifa MG10MD09-08- 4" glass fiber wide band midrange... has a very flat response- looks interesting. I found it at Madisound's site. Looks like it may be a candidate for my next system.
Has anyone heard it?
Also, what is the difference between the scan-speak drivers with the special magnet system, and the plain old Vifa drivers, which seem to lack the upper midrange peak of the Scan-Speak? It seems like the Vifa's could be used with a simpler network, so what is the benefit of using the more expensive Scan-Speaks? More resolution?
Steve
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
Steve:

For one part of your question, I was going to refer you to the thread on diaphragm displacement, but you beat me to it and went there yourself.

Looking over the Vifa you mention-with a cast basket, the mark of a quality driver, (even though I am not sure how important they are)-I do not see any mention of a symmetrical magnetic system.

I suppose that theoretically the same thing should happen, cone displacement-wise, as happens with a bass driver. However, I have not observed this happening.

It could be that the requirements for cone dispacement are so much less at higher frequencies that it actually is happening and we don't know it. Unless the cone travels all the way back, (or forward), and therefore clips the waveform, it really doesn't make that much difference, I don't think.

The other possiblity is that there is something about bass frequencies that causes it to happen only down there. I don't know. But nobody seems to mention it much regarding midrange drivers.

Aside from the symmetrical drive, though, I just thought I would mention one glaring difference between the Vifa and the Scan-Speaks. The Scan-Speak has ten times-that's right, ten times-the one way cone excursion of the Vifa!!

Whether you will actually use it or not is another story. But it is there. Where do you plan to cross these mids over, both on the low end and the high end?
 

SteveG

Account Disabled
2002-01-07 7:20 pm
Newton Falls, Ohio
I was refering to the Scan-Speak having the symmetrical drive magnet system. I have to wonder if it makes any difference at all in the midrange.
As far as you refering me to the displacement thread- it's funny how much these topics end up crossing over sometimes.
Speaking of crossing over- I will be running these mids no lower than 200hz with at least a second order active... probably more like 300Hz, possibly 4th order. I plan to use 4 in series parallel, crossed over at 2khz passively to a Morel MDT-33 to handle the upper mids from 2K to 5K. I will then cross actively to either a Raven R1, or something similar (is there anything similar, ha ha).
I had no idea that the linear excursion on the scan-speaks was so much better! Wow! I think by using four in my design, and crossing over at 300Hz that it won't be as much of a problem. Less excursion by sharing the signal between all drivers should reduce doppler distortion also.
What I was really getting at is the fact that everyone makes a big deal out of the drivers with exotic cone materials, even though they seem to all have a strong upper resonance peak/breakup. I wonder if there is really something else better about them, or if it is just myth. I would prefer to work with the cheaper, smoother drivers. Makes crossing them over a much easier task. Thanks for the reply.
Steve
 

kelticwizard

diyAudio Moderator Emeritus
2001-09-18 2:33 am
Connecticut, The Nutmeg State
Steve:

I want to give you an important figure. It takes 6 cubic inches of air moved to produce 112 dB at 100 Hz.

Double the volume and you go up 6 dB at 100 Hz.
Double the volume and you can go down one half octave, (70 Hz) and remain at 112 dB. The lower you go, the more air must be moved to maintain the same SPL.

Cut the volume in half and you go go down 6 dB at 100 Hz.
Cut the volume in half and you can play one half octave higher, (141 Hz) at 112 dB.

This according to Small, of Thiele-Small fame. This is for closed boxes only. Bass reflex and transmission lines are different.

So to maintain the SPL at 112 dB @ 1W/1M you need:

6 cubic inches for 100 Hz
24 cubic inches for 50 Hz, (okay round it off to 25 cu inches)
100 cubic inches for 25 Hz
400 cubic inches for 12.5 Hz

The Vifa model you selected has a cone area of 6 square inches, (38 sq cm). The requirement for 112 dB @ 100 Hz is 1.5 cu inches.

So one Vifa has to move .25 inches.

However, you are using four Vifas, so each one only has to move .06 inches.

The linear excursion of the Vifa is .025 inches. That means all four Vifas together can only move .1 cubic inches.

So you go down 3.5 dB. The loudest the Vifas can produce, linearly, at 200 Hz is 108.5 dB. That is all four of them working together.

On the other hand, just one of the Scan-Speaks can produce 112 dB @ 100 Hz.

With four Vifas playing, they are likely to be more efficient than 86 dB due to mutual loading. Still, they should be able to produce 200 Hz linearly if 200 watts are passed through them. They should just make it. More than that, and they enter into the non-linear region.
 
With a constant voltage input, cone excursion decreases as frequency increases. By the time the frequency rises to about 200-300Hz, excursion no longer needs to be considered. For a mid-range driver crossing at 400Hz, excursion is a non-issue for home systems.

I am currently building a MODULE with the Vifa M10MD-39-08 and the Vifa D27DG-35-06. The crossover will be passive, first order at 4000Hz. This is a MTM module.

This module will be part of a system with 4 12" woofers, crossed over at 90Hz, 4th order (acoustical + electrical), to an array of 15 inexpensive Pioneer 5" midranges. The Pioneer array will cross to the module at 400Hz, 4th order.

The Pioneer array operating in the range of 90Hz to 400Hz will be operating in a band that contains a great amount of musical energy but because of its efficiency (about 112db/2.83 volts/1 meter, give or take) and the fact that it can handle about 300 watts continuous, will just be coasting along in this tri-amplified system. In term of harmonic distortion, doppler distortion, thermal compression and the dreaded acoustic floor bounce, this array should do very nicely.

The band of frequencies from 400Hz up, handled by the module, should be near perfect given the characteristics of the drivers and network used.

The low frequencies should also be excellent since they will be in sealed boxes with a Q of .6. Room gain will very nicely make up for any deficiencies below F3 but a touch of electronic boost might be in order, depending.

In a tri-amped situation amplifer requirements are very relaxed. For this system, 50 watts for the woofers, 5 watts for the array and 30 watts for the module will be more than enough most music and home theater situations

With judicious shopping the cost of the drivers for BOTH channels has been $660; 8 woofers, 30 lower mid-range, 4 upper mid-range and 2 tweets.

The electronic crossovers will use quality op-amps and since I can do my own boards the cost will be less than $70 and I can easily make sure that everything above 400Hz does NOT go through an op-amp, if I cared.

For amps, the field is wide open. All you need then are enclosures.
 
SteveG said:
Vifa MG10MD09-08- 4" glass fiber wide band midrange... has a very flat response- looks interesting. I found it at Madisound's site. Looks like it may be a candidate for my next system.
Has anyone heard it?

Yep, I have.

I used them in computer speaker design. On paper it looks like the perfect computer speaker, however in my opion these driver really need the help of a tweeter from about 5kHz.

The sound is analytic but with a musical feel that suit most kinds of music, the only caveat IMO is the reproduction of very high frequencies (above 5 kHZ). And they are a real bargain.