Apogee Centaurs- going active

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#22

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#23
Any idea if the Minor x-over linked is correct? As I read it, the woofer 'high' position transitions the low pass from a second to a first order. Parts Express measurements of the original Vifa woofer shows a fairly dramatic upper-mid bump above 1.5 kHz.
 
#26
Active, to my ears, is far superior.
Yes has been...well be in most cases....the ribbon can be setup for lower output...with out so much move ment....what amps are you using....vary good look...thanks for info an pic
 
#27
I am planning to take mine active, but the starting point is always understanding why things were done the way they were in the passive version. Of course like you this also opens up the option of a completely different solution at the low end...
 
#28
billshurv said:
....matches what I have seen when the cabinet fell off mine.
Click to expand...

Thanks Bill, the phase orientation doesn't surprise me. Phase coherency was a hot topic when the Minor was designed. The hole in response across the x-over range also shows up in Stereophile's measurements. Apogee recommended listening off the inside axis, I suspect leveraging lobing to fill it in. The hop from second to first order is a head scratcher and negatively audible to me.
After twenty years with the Minor, like you the performance of that ribbon continues to impress.
 
#29
rdf said:
Any idea if the Minor x-over linked is correct? As I read it, the woofer 'high' position transitions the low pass from a second to a first order. Parts Express measurements of the original Vifa woofer shows a fairly dramatic upper-mid bump above 1.5 kHz.
Click to expand...

Yeah, that particular crossover diagram is incorrect. (I noticed that many years ago on the old Apogee forum.)
Unfortunately, the Apogee crossover diagrams are user supplied in most cases and mistakes were sometimes made in analyzing the wiring configurations and translating them into conventional format schematics.

Cheers,

Dave.
 
#30
well starting at the top, the crossover I linked, which is close to the Mk1 eyeball of a real minor crossover seems to have a presence dip around 3KHz based a quick back of envelope calculation. Any one have any ideas on this?

Once that cleared then its the question of how low you can run the 26" ribbon. 750Hz isn't a bad point as you are pretty much splitting the power 50/50 between the drivers, but is there an advantage in going a bit lower with LR4 electrical?
 
#32
billshurv said:
well starting at the top, the crossover I linked, which is close to the Mk1 eyeball of a real minor crossover seems to have a presence dip around 3KHz based a quick back of envelope calculation. Any one have any ideas on this?

Once that cleared then its the question of how low you can run the 26" ribbon. 750Hz isn't a bad point as you are pretty much splitting the power 50/50 between the drivers, but is there an advantage in going a bit lower with LR4 electrical?
Click to expand...

Bill,

If you believe the component values on that notch filter in the high-pass section, then the dip frequency is approximately 9.2khz. (10uF/30uH) I'm not sure how you're computing 3khz. However, 3khz seems like a more realistic frequency considering that driver. It's like I said, you can hardly believe anything you see regarding Apogee schematics. 🙂

I think it's probably preferable to run the ribbons as low as they can go.....considering the electrical roll-off of the filter you use. If you start seeing them move around quite a bit, it's time to raise the xover frequency or steepen the slope or both.

Cheers,

Dave.
 
#33
It was a 'quick' calculation some time ago so I can believe that as I didn't check it, but made a note to come back and work out why it was there. In what was a cheap speaker for Apogee they would have had a reason for putting it in. Looking at the impedance plots from the stereophile measurements there is is a wrinkle in the impedance plot around the 9KHz point so that makes sense. Looking at the frequency plots again there is a hump off axis vertically so I would need some correction for that.

Hmm off to muse choices from 500Hz down. If I didn't have such a small room I would be tempted to go Open baffle.
 
#35
There are certainly better ways to do it than apogee did. If the damned things weren't so good at some things i would abandon them for something with different compromises. The transition from line to point source is one thing that I haven't got a full handle on from a spacial perspective. What drive units would you consider for an array?

The other thing I wonder if is the ribbon would benefit from different loading with some sort of waveguide.
 
#36
Got say,I got this pr of Minors for $200-250..with stands....look like new..picket them up for the MT ribbons...incase I lost one of my stages ..but I like the topend better than my stages....but ezey to see why....the minor ribbon is open in the back an the base box......... works like a horn .....I get more hight in the image, than the stages an for the money there a lot too for give....crossover are made with better parts than some B&W 801-803s I have paid big money for...back in the 90s...........
 
#37
billshurv said:
What drive units would you consider for an array?
Click to expand...

Haven't given it significant thought. Zaph's driver looked interesting for a single row of four, the Dayton RS100-4 for double. This is from a passive x-over perspective. If I were to do this the goal would be covering the lower range of male voice with a single driver, which means at least down to 100 Hz.
Re: the transition, I still hear its presence. On axis the flat first arrival does wonders to minimize the impact but to my ear it's central to the Minor's overall character.
 
#38
I haven't either, mainly because I know that it is very easy to make things worse and I am am relearning some stuff I haven't used since the 80s ( 3 kids use up a lot of your free time for 20 years).

I got as far as looking at some OB calcs but realised I just don't have a big enough room for that, so need to stick with a box for low frequencies. The cabinet on the minors is at best adequate so happy to hack that off and build a new one. I have some dibs on enough Corian to build new baffles so can start from scratch.

Over the last week I have been wondering about a midrange ribbon to get down lower, but that is just thoughts rather than any calculations yet.
 
#39
Thanks for the stimulus, you guys!
Open baffle lower mid/woofer seems like it may be worth experimenting with.
The original Vifa 8" is a candidate, also I have four peerless 6.5" nomex that are doing other duty right now. How about a pair of Hivi B4 on each side?
I haven't played with open baffle since the 1960s - sounds like fun.
 
#40
No Thank you. My minors have been languishing waiting on ribbons and I was close to parting with them. It seemed I was looking at a path no one else had considered. Now I am more confident it is worth seriously considering.
 
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