Vifa Drivers

wrenchone · 20th March 2004, 04:16 AM

I just ponied up and bought 32 pieces of a 4 ohm, 4.5" Vifa mid-bass from Parts Express (P/N 299-495). For the time being, I'm loading them into my old cabinets, which are hexagonal prisms with 16 midbass drivers and 3 tweeters per side. However, I've had these speakers for over 20 years, and I could be interested in something new.

I was thinking of using 8 drivers per side in series-parallel to get 8 ohms nominal impedance. The speakers have a decently low Fs (65 Hz), low Qts (0.27), and a half-decent Xmax (3.5mm). What would be a suitable way to use these drivers?.

Bill Fitzpatrick · 20th March 2004, 05:02 AM

The curve is interesting in that it appears to have built in baffle step compensation. A 16 driver line array barely wider than the driver with a tweeter in the middle might be interesting. Cross over as low as possible to avoid the comb effect. Use a sealed enclosure for a Qts of .7 and cross at F3 to a nice sub - 4th order low pass and second order high pass.

sreten · 20th March 2004, 01:50 PM

Hi BF,

Interesting observation but the step is far too rapid for
BSC, at least the sort of baffle step slopes I've seen.

If the 3 tweeters are arranged around the hexagon, i.e. to
give a horizontal omnidirectional field, and the same thing
is done with the bass units then BSC will not be needed.

WO, how are your drivers currently arranged ?

I'll also note 8 drivers with 8ohm loading,
(the driver seems to be 90dB/2.83V around 500Hz)
will be 96 dB/W !.

sreten.

Bill Fitzpatrick · 20th March 2004, 02:27 PM

Quote:

Originally posted by sreten
Hi BF,

Interesting observation but the step is far too rapid for
BSC, at least the sort of baffle step slopes I've seen.

Right. What was I thinking?

wrenchone · 20th March 2004, 04:32 PM

For your reference, my boxes (built in 1979) are hexagonal prisms 24" high, with 8" faces. The speaker loading is : front - 2 mids plus one tweeter, either side of front - 3 mids plus one tweeter, next two faces - four mids , back face - blank with connectors. The mid drivers are
5 1/4" "Westwells", purchased from McGee Radio, an early source for DIY speaker builders and sadly defunct. I had to load the cones with polyurethane varnish to smooth out the midrange sound, as the drivers were originally rather harsh. The tweeters started out as Motorola piezo horns, and were changed to Vifa textile dome tweeters.

I want to try a new concept, or at least, a new set of enclosures. One possibility would be to keep the hexagonal prism concept, but taller, so that the more forward facing segments of the hexagon could be loaded with the bulk of the drivers. The current boxes are closed; the new ones could be ported. A line array is also a possibility. The question I was really asking was, given the characteristics of the new mid drivers, which approach would be best suited for them?

20th March 2004, 04:16 AM	#1
wrenchone diyAudio Member Join Date: Feb 2004 Location: Silicon Valley	Vifa Drivers I just ponied up and bought 32 pieces of a 4 ohm, 4.5" Vifa mid-bass from Parts Express (P/N 299-495). For the time being, I'm loading them into my old cabinets, which are hexagonal prisms with 16 midbass drivers and 3 tweeters per side. However, I've had these speakers for over 20 years, and I could be interested in something new. I was thinking of using 8 drivers per side in series-parallel to get 8 ohms nominal impedance. The speakers have a decently low Fs (65 Hz), low Qts (0.27), and a half-decent Xmax (3.5mm). What would be a suitable way to use these drivers?.

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20th March 2004, 05:02 AM	#2
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	The curve is interesting in that it appears to have built in baffle step compensation. A 16 driver line array barely wider than the driver with a tweeter in the middle might be interesting. Cross over as low as possible to avoid the comb effect. Use a sealed enclosure for a Qts of .7 and cross at F3 to a nice sub - 4th order low pass and second order high pass.

20th March 2004, 01:50 PM	#3
sreten diyAudio Member Join Date: Nov 2003 Location: Brighton UK	Hi BF, Interesting observation but the step is far too rapid for BSC, at least the sort of baffle step slopes I've seen. If the 3 tweeters are arranged around the hexagon, i.e. to give a horizontal omnidirectional field, and the same thing is done with the bass units then BSC will not be needed. WO, how are your drivers currently arranged ? I'll also note 8 drivers with 8ohm loading, (the driver seems to be 90dB/2.83V around 500Hz) will be 96 dB/W !. sreten.

20th March 2004, 04:32 PM	#5
wrenchone diyAudio Member Join Date: Feb 2004 Location: Silicon Valley	For your reference, my boxes (built in 1979) are hexagonal prisms 24" high, with 8" faces. The speaker loading is : front - 2 mids plus one tweeter, either side of front - 3 mids plus one tweeter, next two faces - four mids , back face - blank with connectors. The mid drivers are 5 1/4" "Westwells", purchased from McGee Radio, an early source for DIY speaker builders and sadly defunct. I had to load the cones with polyurethane varnish to smooth out the midrange sound, as the drivers were originally rather harsh. The tweeters started out as Motorola piezo horns, and were changed to Vifa textile dome tweeters. I want to try a new concept, or at least, a new set of enclosures. One possibility would be to keep the hexagonal prism concept, but taller, so that the more forward facing segments of the hexagon could be loaded with the bulk of the drivers. The current boxes are closed; the new ones could be ported. A line array is also a possibility. The question I was really asking was, given the characteristics of the new mid drivers, which approach would be best suited for them?

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