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Old 5th October 2004, 07:39 AM   #1
amo is offline amo  United States
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Default Please assist with a Vifa design

Hi-

I recently picked up 4 Vifa OEM drivers, designed for the Mackie active monitor. These are 8 inch poly cones, and are very nice all the way up to 2khz. I also got a pair of Vifa OEM tweeters, which are pretty good, but I feel like the higher I can cross them over the better. I like the Macke monitors as long as the few problems can be cured. First, the Mackies have a passive radiator, and second, I believe they loose clarity in the crossover region, maybe because the 8 inch drivers are pushed too high. The way I was going to cure these ills is by doubling up on the 8 inch, thus increasing the output in the crossover region as well as in the low end (so that a sealed enclosure can be used).

I was hoping to make this a quick/cheap project, but now that I have started construction, I can not help it but to put forth quite a lot of effort. So in search of that great midrange, I keep thinking about turing this into a 3-way by using the Vifa Classic P13MH midrange. This driver would match well with the poly woofers. I am hoping that I can "clear up" the 800 to 3.5K range by using this, and use first order filter as well.

Sorry for rambling on, but please please help me decide if I should go with the mids, or just keep it simple. BTW the filters will be line level, active or passive, not sure yet... but defenantly line level.
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Old 6th October 2004, 09:32 PM   #2
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Hi Amo,

Just thought I would bump this. Seems a lot of people run into this problem with 8" speakers trying to make two ways....

three ways get discouraged a lot in here, but IMO you can probably make *your* speakers sound better going three way..... yeah crossovers will be much more difficult, but I think, a non optimal 3 way crossover should still be better than poorly matched drivers in a two way

I must say though, having played a lot with 3 ways with different drivers and crossovers (all very unscientifically) you can get some very ordinary results!!!!!!!!!!!

Tony.
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Old 6th October 2004, 11:36 PM   #3
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I think your chance of success will be far better with a 2way.
An MTM with two 8s can provide excellent results, the trick will be picking the right tweeter which can be crossed relatively low, say around 2k.
Now having said that I'm pretty sure the Vifa 8 you've got is the P22wp - 4 ohm, which really rules out using two of them in parallel, yoyu could try them in series but some people have found that not to sound as good as paralleled - go figure.

So you are probably stuck with using a single driver, if you want to go 3 way by all means give it a shot, the P13 is an easy driver to work with.
I would reocmmend a single 8 ported, sealed mid in a large stuffed enclosure with a non-parallel back wall.
Get your mid/hf xover right - 2nd order at 3.5k is as good as any starting point then work on the bass/mid xover & work between 350-500hz.
Also, If you are going line level xovers then go active.
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Old 7th October 2004, 09:30 AM   #4
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I think you would be better off with biamping the woofers and using the P13 as a mid. Then you are effectively making a simple and easier to design 2 way and adding some woofers to do the bass. This is probably easier than trying to get your 2 way sound right. Last time I heard a 2 way with 8" drivers was the Vaf DCX and the midrange was pretty ordinary.
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Old 7th October 2004, 11:10 AM   #5
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Australians to the rescue!!! Thanks guys!

I have amassed enougph transformers to throw together a gainclone for each driver, so no problems here. Each of the 8 inch drivers will have its own amp, so the fact that they are 4 ohms is ok (by the way AP, they are P22wp manufacted in '97, but never used and still in original packaging). I am in the middle of constructing some serious enclosures for this thing and making them flexible to be either 2 or three way. The funny thing is that I have already spent more money on the wood and glue then on all drivers combined! This is the only reason I began contemplating adding a mid. In other words, "ordinary midrage" was part of my innitial design, but now that all this money has been spent, I feel like adding a mid may be in order. The issue is that this means building 2 more amp channels..... I really do not mind this, but here is what I need to know:

Considering that these drivers are all poly cones, and are otherwise fairly well matched to each other, can I use 6 db slopes? If not, should I just go for a digital crossover (Behringer) where I can have huge slopes but phase compensated. If this is the case, can I just go 2-way and have like 50 db slope at 2 Khz ? This is the kind of junk that is driving me crazy! Again thank you Australia!!!! You mates are the BOMB!
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Old 7th October 2004, 11:16 AM   #6
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By the way, if 6 db slopes are used, will driver spacing be a problem as these are fairly large. An 8 inch driver may be 10 inches away from another 8 inch driver, both of which are low passed using a gentle slope, and therefore playing fairly high. Does this spell weird canelation patterns?
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Old 7th October 2004, 01:24 PM   #7
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If it were me I'd go with 4th order LR with an active xo. With the P13 you have more flexibility than the 8" as it is smooth and can handle a higher crossover point. With a 4th order slope to the tweeter you can cross lower without pushing the tweeter too far. The crossover point is therefore probably not as crucial as with a 2 way with the 8".

I'd then cross to the woofers at say 300 Hz. If you have a pair of them it will help a little with BSC.

The idea of the Behringer digital crossover has interested me as well. However in this situation I'd say it would be more expensive. I'm not sure the extra power and flexibility is needed and I suspect a good active crossover is more transparent.

If someone can prove me wrong on this point, please do so!

You might find this interesting. This guy has a system using the Behringer digital crossover with some nice drivers. I think it would be very impressive:

http://users.pandora.be/airborne/
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Old 10th October 2004, 11:09 PM   #8
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A lot of people have used the Behringer digital xover at Madisounds site', keeping in mind you will then need a 6channel volume control.
You could end up with an excellent system with two 8s, the P13 in a 3way full active. You will need 4 channels of amplification for each speaker though (as the woofers are 4ohm, paralleling them will drop them to 2, so best add another amp).
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Old 11th October 2004, 03:28 AM   #9
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Quote:
Originally posted by Ap
A lot of people have used the Behringer digital xover at Madisounds site', keeping in mind you will then need a 6channel volume control.
You could end up with an excellent system with two 8s, the P13 in a 3way full active. You will need 4 channels of amplification for each speaker though (as the woofers are 4ohm, paralleling them will drop them to 2, so best add another amp).

I am not sure why I would need 6 channels of volume control. I have a balanced out on my source, which I was going to run through a BOSOZ for volume control, and then into the Behringer, which takes in two channels and puts out 6 (I think). Are you saying the crossover has to come before the volume control?
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Old 11th October 2004, 05:51 AM   #10
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Not sure what a BOSOZ is, but as I understand it people were using Cd player digital out to the Behringer DCX2496 which then outputs 6 channels 2 x bass/mid/high. Hence the need for a 6 channel volume control.
Then again if you are using the analog input you can attenuate there before the Behringer.
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