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Old 3rd February 2013, 09:51 AM   #1
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Default small 3 way. Is this a good idea?

ive wanted to build a 3 way for a while, and i have a surplus of drivers lurking, waiting to be used.

The idea is to use these, if its feasible.

They are: a 6 1/2 inch woofer (good to about 2k and Fs at 40hz), A5 for mids (~600-6k), and ribbon from 6k up.

What do the 3way experts think? Waste of time?

My goals are to control polar patterns, and keep crossover points out of the critical 1-4k area, bass extension with the woof should be 35-40hz vented.
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Old 3rd February 2013, 01:10 PM   #2
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I too have been thinking small three way for the same reasons. My plan is to use the same woofer/tweeter as my best set (Seas ER18 etc.) and trying to keep as many things the same as possible, then do a midrange. First guess is 800, 5K first order crossovers. Is Vanderstein right? Picking the mid has been the issue. I am leaning to the FE89. I have not found any mid I think would be happy higher.

So, is a three way shallow crossover really better in a typical living room over a two-way steep crossover? Can this really nail Joni Mitchel's voice? Can it keep John Williams's guitar from sounding metallic? Harry James trumpet from being edgy?

Let us know what mid you pick.
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Old 3rd February 2013, 01:10 PM   #3
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Good idea as it reduces distortion due to the doppler effect. I would not use a ribbon though there overpriced and the performance is not as good as a ring radiator/dome. I would use the vifa xt-19 and cross ~4k. Don't know what the A5 is.
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Old 3rd February 2013, 01:42 PM   #4
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Quote:
Originally Posted by kipman725 View Post
Good idea as it reduces distortion due to the doppler effect. I would not use a ribbon though there overpriced and the performance is not as good as a ring radiator/dome. I would use the vifa xt-19 and cross ~4k. Don't know what the A5 is.
This is the second time recently the XT-19 has been mentioned over the 25. I am assuming it has the same basic tendencies to be very smooth when used higher? I was also thinking OM-1 put will use the Seas so I can keep as many things the same as the "reference" two ways.

I bet we are thinking about the same thing, but could you describe Doppler effect in the context you mention?
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Old 3rd February 2013, 03:03 PM   #5
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Thanks its nice to know i havent lost the plot!

The woofer is Mission CP168, the midrange is an Alpair5, and the ribbon is a Fountek.

All of these are 'budget', except maybe the Alpair5, though it wasnt expensive. Around 50 per speaker without the cost of the alpair5 (dont recall their price). 1st or low order is the aim, within the xo points mentioned. I own all these already.

Normally Id follow the formula of 8 inch for a 3way, but im using what i have sat here unused.

The CP168 is paper cone smooth natural roll off, slight peaking at 2k and 3k.

The Alpairs I have show a cone edge resonance at bang on 400hz (recently found with test tones during a Zplot).
Im hoping the small alpair is omni enough at the HF xo point to match the ribbon.

Also Im itching to use the ribbon, and this seemed to be the perfect opportunity (or excuse) to use it.

Perhaps a little compromised, but maybe not too bad.
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Old 3rd February 2013, 03:45 PM   #6
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I'd consider going steeper than 1st order on the ribbon, or it'll be distortion aplenty - they really don't like low frequencies (for a tweeter).
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Old 3rd February 2013, 04:10 PM   #7
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Default @ Chris661

Yes I agree Chris.

Since the cross over is intended to be ~6k I was musing that perhaps 1st order at 6k would be ok. It may well turn out that 2nd is the lowest order that is practical.

This would likely mean that the Alpair5 would have a matching 2nd order BP, and perhaps only the woofer would use a 1st order LP. In this way a measure of BSC may be applied, since the A5 efficiency will dictate the system efficiency (its the lowest)

I plan to align phase between Mid and HF, and have the inversion on the woofer, provided I can get away with doing that.

However, the NeoCD3.5H I have here are recommended to use a 3rd order at 3k minimum, so I would have around 6db less attenuation (using 1st order), and since Im thinking of using the Alpair, I could move the HF x-o higher still (polar behaviour of the A5 being the restriction)
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Old 3rd February 2013, 05:59 PM   #8
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Looks reasonable on paper. The 5 looks smoother than the 7. Don't know why the quit making it.
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Old 3rd February 2013, 09:08 PM   #9
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To be fair the Alpair5 I have are the original model (is there gen2?). They have their flaws, the cone edge resonance mine have is a bummer. Saying that i cant recall if it occurred in a free air or enclosed Zplot, so i should verify when i get time.

Also, id really like to get some decent metal woofers to replace the missions, but the CP168 are cheap and surprisingly clean. Just a tad ugly.

Im sure however, that the newer alpair6 are comparable.

Some may be thinking 'why not just build a FAST?) Well. Nice as these small near fullrange drivers are, they arent as good at HF transiently.

Ive been so impressed by the ribbon (Quoted 95.5 dB@2.83V). It was padded down to about 85dB, to match the woofers in my mains. Xo'd 3.5k 2nd order, so far from the recommended.
The thing is, padded some 10dB+, they arent 'full of THD'. Thats at modest levels, 85db@2m.

I wouldnt run it like this forever, i wouldnt want to risk it, but despite that i know they would play clean to higher volume that the woofers.

Its the ribbons reproduction of 'inaudible' freqs that is addictive. I often wonder if a dome with the same VHF bandwidth would also have similar distortion profiles.
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Old 3rd February 2013, 11:16 PM   #10
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I wonder if that is the attraction of the OM1? People seem to love or hate ribbons, so I suspect there is something there to be known.

What I have learned about full range drivers with the Fostex and Fountek is that they rely on breakup modes to give the perception of a balanced HF. So to use them as mids, they need careful crossover and/or notches. Just looking at their specs, I suspect the Mark to do the same. I was successful to a point in doping the Foxtex 125's to kill a couple of the breakup modes, but the total end result was still not the best. I killed one of the breakup modes on the little FE85's by doping the dust cap. But I tried the same kind of thing on a Zaph that worked on the Fostex and it was a disaster. I wonder what the csd on the Mark looks like?
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