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Old 21st March 2013, 12:08 PM   #11
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Thanks, will do
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Old 21st March 2013, 03:54 PM   #12
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From Pieter Treurniet:

"What am I missing that you guys keep talking about step-up transformers?
Function of the transformer here is to adapt the low impedance ribbon to the amplifier; the amp likes to see a 4 ohm reflected load. When the midrange ribbon is 0.1 ohm (which will be about right when I calculate the DC resistance of a 50 mm wide, 10 mu thick and 2 meters long aluminium midrange ribbon) we need a 4 : 0.1 ohm step-down transformer, which will have a turn ratio of some 6.3 : 1. Therefore it will have 16 dB of attenuation at the same time.
Other point is that for a transformer working from 300 Hz and higher it is not necessary, even not very clever, to pick a "150 watt transformer core"; power at these frequencies is much less.
You can do it with autoformers as well but be sure that the amplifier output is DC free".

PS. Pieter asked me to post this for him.
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Old 25th March 2013, 10:10 AM   #13
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Update:
-I've measured the ribbons, 0.1 ohm for MF, 0.9 for HF, so seems around the same as LineSource's readings.
-Since I'll be replacing the ribbons someday Ive emailed Graz for impedance figures of his replacement ribbons, but no reply so far.
-Peter Treurniet of Tribute Audio Transformers, very helpfull guy btw, is making potted amorphous c-core step-down transformers for the midrange at a decent price, he has actually made some for Graz in the past.

So getting there Only thing i'm doubting are the LF amplifiers, the hypex nc400 outputs 570W/2Ohms with a 24A limit. Alternatively I could get the ucd2000 which output 2000W/2Ohms with a 50A limit. The nc400's output impedance is 10 times lower then the ucd2000's and Ive heard em, the NC400 sounds much better. SO Prefer the NC400 but will it be strong enough!!
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Old 30th June 2013, 04:44 PM   #14
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by tyu View Post
http://www.apogeespeakers.com/.............i gess you saw this...crossover is in the manul
you can down lode.......bewair of the Apogee panel Buzz!...theses are the oldest... i think?... I have Had the Stages an the Duetta Sig....
Good luck
Link does not work
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Old 30th June 2013, 04:46 PM   #15
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by Bas Horneman View Post
From Pieter Treurniet:

"What am I missing that you guys keep talking about step-up transformers?
Function of the transformer here is to adapt the low impedance ribbon to the amplifier; the amp likes to see a 4 ohm reflected load. When the midrange ribbon is 0.1 ohm (which will be about right when I calculate the DC resistance of a 50 mm wide, 10 mu thick and 2 meters long aluminium midrange ribbon) we need a 4 : 0.1 ohm step-down transformer, which will have a turn ratio of some 6.3 : 1. Therefore it will have 16 dB of attenuation at the same time.
Other point is that for a transformer working from 300 Hz and higher it is not necessary, even not very clever, to pick a "150 watt transformer core"; power at these frequencies is much less.
You can do it with autoformers as well but be sure that the amplifier output is DC free".

PS. Pieter asked me to post this for him.
Why a transformer when he could use resistors and match impedance with the bass panel ...
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Old 30th June 2013, 04:53 PM   #16
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by edbk View Post
Update:
-I've measured the ribbons, 0.1 ohm for MF, 0.9 for HF, so seems around the same as LineSource's readings.
-Since I'll be replacing the ribbons someday Ive emailed Graz for impedance figures of his replacement ribbons, but no reply so far.
-Peter Treurniet of Tribute Audio Transformers, very helpfull guy btw, is making potted amorphous c-core step-down transformers for the midrange at a decent price, he has actually made some for Graz in the past.

So getting there Only thing i'm doubting are the LF amplifiers, the hypex nc400 outputs 570W/2Ohms with a 24A limit. Alternatively I could get the ucd2000 which output 2000W/2Ohms with a 50A limit. The nc400's output impedance is 10 times lower then the ucd2000's and Ive heard em, the NC400 sounds much better. SO Prefer the NC400 but will it be strong enough!!
The NC400 would be a poor choice at that impedance , if you examine its distortion spectra you will see its knee is at 100 watts giving you best sonics at 10 amps, the 24amp rating is greek mythology if wanting good sonics ..

Regards
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Old 30th June 2013, 05:33 PM   #17
a.wayne is offline a.wayne  United States
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Good stuff Source, i guess you have an apogee for every room


Quote:
Originally Posted by LineSource View Post
Hi edbk,

We have a pair of Apogee Full Range Speakers in our living room. They came with the 4-ohm network box.


Over the Full Range production lifetime Apogee made a few minor changes to the construction of the Bass Panel, midrange ribbon, and tweeter ribbon which affected their resistance, efficiency, and resonance.
MY SPEAKERS:
Bass Panel = 1.86 ohms
Midrange Ribbon = 0.14 ohms
Tweeter Ribbon = 0.88 ohms

Original passive front-end crossover box is 6db at 320Hz between the bass panel and mid-tweet ribbons.
=================

You will want to measure your speakers before you build a custom crossover, or decide to clone a production circuit. Bi-Amping (bass + mid-tweet) using an active circuit crossover is a good starting option. The low efficiency 1.9 ohm bass panel can easily consume 300-1000 watts.

The midrange ribbon step-up transformer that you build or purchase will be the cornerstone specification for the rest of the passive or active crossover design. The turns ratio will set the impedance step-up. The inductance of the production midrange step-up transformer input is actually part of the low-pass crossover slope. The inductance of any transformer you purchase will need to be measured and factored into the total crossover design. This step-up transformer will set the midrange ribbon efficiency and effective amplifier input inpedance load. The ribbon impedance is almost pure resistance, and this simplifies the design of a passive crossover between the MID-TWEET ribbons.

Apogee also offered a 1-ohm network box for JUST the midrange+tweeter ribbons. This box included a 0.14-to-1 ohm step-up transformer for the midrange ribbon, plus R+C crossover network for the tweeter ribbon. There is potential for sonic improvements with this 1-ohm network box vs. the 4-ohm network box, but only if the amplifier can deliver HUGE amperes into 1-ohm like the BIG Krells.

Naturally, constructing a custom Bipolar amplifier that can drive 0.2 or 0.5 ohm resistive ribbon loads directly is another option, and not very difficult. From my listening experiments, adding a small series resistance to increase the 0.14 ohm midrange ribbon up to 0.2-0.5 ohms improved the sonics.
=================

My Speakers...
Each 3-way Full Range is bi-amped with one Krell KSA250 located just behind the speaker. A Krell KRX-1 electronic crossover with 18db/octave at 200Hz is used for for bass-MT outputs to each amp. One KSA250 channel direct drives the 2 ohm bass panel, and the second channel drives Apogee's M-T interface box which is ~4 ohms. This interface box contains a large toroidal step up transformer for the 0.14 ohm M-ribbon, plus resistors to step up the tweeter ribbon resistance to ~4 ohms, plus a 6db/octave passive L + C Xover at 10Khz. This is a very robust setup for the Full Range.

I have built DIY amps which direct drive the 0.1 ohm midrange ribbon and 2 ohm tweeter ribbons. Direct drive always produces greater dynamics and detail, but it is also easier to damage a ribbon by human error.
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Old 4th July 2013, 10:52 AM   #18
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I have the hypex dlcp and 6 ncore's sitting here for a while now.

Waiting for the midrange transformer from tribute audio but it's been 3 months now, running out of patience on those so one of these days I'm gonna hook it all up with a 2 Ohm resistor for the midrange and see what happens. I'll see if I can cancel the order and get some transformers elsewhere if it doesnt work out.

The dlcp suprises me in pure SQ performance, it sounds significantly better using it as a 2 channel dac then my former modded lavry da-11 did! More dynamic, more musical. Currently experimenting with powersupplies on it, gonna try simple C, CRC, LCLC, superregs, in stead of the aux on a smps600, may make a difference, may not
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Old 6th July 2013, 07:19 PM   #19
a.wayne is offline a.wayne  United States
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I would use resistors instead of a transformer for mid , less distortion and of course will affect sensitivity , you will have to adjust gain accordingly to compensate best .7-1.5 max based on ncore 1 ohm resistor may work ...
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Old 28th August 2013, 12:18 PM   #20
BillWW is offline BillWW  United States
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Question Full Range stock cross over

I just brought home my fully restored Apogee full Ranges. Unbelievably heavy to carry into my basement with 4 guys for each crate/module They are now assembled. But I still have not been able to listen to how well they will sound restored yet!!!

Would anyone have any photos or be able to verify how to wire up the transformer portions of my stock impedance box?

I needed to rebuild my stock impedance box, because the original owner removed a lot of capacitors and I do not trust if he wired up the impedance transformer correctly.

Specifically, does anyone know if it matters on the mid-range impedance transformer of which polarity on the speaker side to solder up the transformer to? I have seen some photos showing the top side of the transformer going to the red lead and the bottom wire coming off of the transformer going to the black lead. Is this correct?

On the speaker side of the box the top black heavy 6 gauge wire goes to the top black colored post with the bottom going to the white post. Is that correct?

Also, I notice my larger black 6 gauge winding is not wrapped uniformly around the toroidal impedance transformer. It seems to go only about half way around apparently avoiding the bass panel transformer? Would it interact if I spread the 6 gauge wire around evenly near the other bass panel transformer?

The reason I am asking is because the prior owner had modified my interface box and I found it had some original wonder caps missing.

I can figure out the capacitors, but do not know if the mid-range transformer needs to be wired to the correct polarity or I worry there might be phase issues?



Thanks, Bill
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