DIY biamp 6-24 crossover

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cubicincher

Member
Joined 2016
to JRKO #859

Hello JRKO,


I have built two 6-24 XOs.


I use one for my 2-way-speakers (at 2500 Hz crossover-frequency),
the other one for the crossover at 80 Hz between sub and the 2-way speakers
(all fully active with different Pass DIY amps).

It is way above its price point. For me the 6-24XO is a present/gift from Mr. Pass to us DIYers.

Hopefully the rest of your system is as good as this active crosssover?! ;)



Cheers
Dirk :D
 
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RogerGustavsson

Member
Joined 2004
I think the passive crossover is slightly different. If the values given in the schematic are correct, the low pass is about 150 Hz not 108 Hz.

The high pass is just a capacitor and could be done without additional active circuitry. In many cases that high pass cut-off can be made in the power amplifier driving the mid/tweeter, simply by changing the value of one or two capacitors.

Adding a balanced output can be done in several ways but it is not necessary in most cases, certainly not if you have short interconnect cables. If the power amplifier have differential inputs, the component driving it do not need to have differential/balanced outputs. Balanced output means the impedance of the positive and negative pins/connections are balanced. You will need a resistor and a capacitor for that. You need to measure the output impedance of the last bufferstage of the crossover.
 
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RogerGustavsson

Member
Joined 2004
From the manual "output impedance is about 250 ohms". As that include a resistor of 100 Ohms, the circuitry itself should be about 150 Ohms. The hot and cold impedances should be as close as possible for good rejection of disturbances, maybe within 1%. I have measured the output impedance of some microphones with a guide from Jensen Transformers but I do not remember the procedure right now.
 
Last edited:
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wtgraham1

Member
Joined 2015
RogerGustavsson said:
I think the passive crossover is slightly different. If the values given in the schematic are correct, the low pass is about 150 Hz not 108 Hz.

The high pass is just a capacitor and could be done without additional active circuitry. In many cases that high pass cut-off can be made in the power amplifier driving the mid/tweeter, simply by changing the value of one or two capacitors.

Adding a balanced output can be done in several ways but it is not necessary in most cases, certainly not if you have short interconnect cables. If the power amplifier have differential inputs, the component driving it do not need to have differential/balanced outputs. Balanced output means the impedance of the positive and negative pins/connections are balanced. You will need a resistor and a capacitor for that. You need to measure the output impedance of the last bufferstage of the crossover.
Click to expand...

I have the MG20 not the MG20.1 and you are right I could just use a cap for the high pass. I'm using a Sonic Frontiers Line 3 pre amp. The unbalanced output on the preamp are going to my Subs and the balance output are going to go to the speaker amps. I don't have the passive crossover for these speakers. That is why I need balance for these speaker. I would need two 132uf cap that would cost about the same as to build this active crossover and the inductors and cap for the low 18db slope would cost more also. My amp to drive the MG are Classe CA2300 for the bass and Classe CA 300 for the mid/tweeter.

The 108 crossover is for the the MG 20.1 and you are right the crossover for the MG 20 is about 150.
Thanks
 
pixelpusher

pixelpusher

Member
Joined 2004
RogerGustavsson said:
From the manual "output impedance is about 250 ohms". As that include a resistor of 100 Ohms, the circuitry itself should be about 150 Ohms. The hot and cold impedances should be as close as possible for good rejection of disturbances, maybe within 1%. I have measured the output impedance of some microphones with a guide from Jensen Transformers but I do not remember the procedure right now.
Click to expand...

Nelson mentioned a figure of 75 ohms as the output impedance of the jet. So I used a 175 ohm resistor. Not sure about adding a capacitor. I did not.
 
Nelson Pass

Nelson Pass

The one and only
Joined 2001
Paid Member
wtgraham1 said:
when using two of these in the balance mode what should the input impedance and output impedance be.
Click to expand...

For things like this we are generally looking at low output impedance
and high input impedance. The input of the 6-24 filters are buffered
to allow for level pots at the inputs. Depending on the Jfet follower
used, the output impedance will be 20 to 80 ohms plus the output
put resistor which is necessary to assure high frequency stability -
100 ohms is the typical minimum.

You can easily create a balanced filter using two of these filters, one for
plus and the other for minus, but you generally need to set the input
levels as equal.
 
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wtgraham1

Member
Joined 2015
RogerGustavsson said:
I think the passive crossover is slightly different. If the values given in the schematic are correct, the low pass is about 150 Hz not 108 Hz.

The high pass is just a capacitor and could be done without additional active circuitry. In many cases that high pass cut-off can be made in the power amplifier driving the mid/tweeter, simply by changing the value of one or two capacitors.

Adding a balanced output can be done in several ways but it is not necessary in most cases, certainly not if you have short interconnect cables. If the power amplifier have differential inputs, the component driving it do not need to have differential/balanced outputs. Balanced output means the impedance of the positive and negative pins/connections are balanced. You will need a resistor and a capacitor for that. You need to measure the output impedance of the last bufferstage of the crossover.
Click to expand...

Hello do you have the manual for the MG20. What are the crossover points.
 
C

cubicincher

Member
Joined 2016
MG20R

Hello,


this is the crossover-schematic I found for the 'Maggie' MG20R.


Cheers
Dirk
 

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wtgraham1

Member
Joined 2015
cubicincher said:
Hello,


this is a link to the manual of the 'Maggie' MG20.1:


MG20.1 Manual 201


crossover and slope are mentioned. Most important to me: adjust by ear :D
or specrum analysis...


Cheers
Dirk
Click to expand...

Thanks I have the MG20 not the MG20.1. I just wanted to know what the MG20 suggest for crossover points for the active crossover, and what are the crossover points and slopes. I have the MG20.1 manual and was going off what it says.
 
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RogerGustavsson

Member
Joined 2004
Magnepan do not publish the schematic of the crossover anymore. If the schematic above is correct, something like 280 Hz as there must be some series resistance in the coil before the driver. It is not really a must to use an active circuitry for that first order slope, a simple capacitor ahead of the power amplifier driving the mid/tweeter will do. The signal path within the Pass 6-24 includes a couple electrolytics and active devices that may add some "signature" of its own to the sound. At least they make the path longer and some of us want to reduce it to a minimum. It should be noticed that the removal of the passive external crossover of the MG 20, will increase the bass level a bit when an active crossover is used. How much depends on the series resistance of the large coils.
 
jamayfie

jamayfie

Member
Joined 2006
Paid Member
DIY Sony VFET and the 6-24 crossover?

Just at the thought experiment stage: if I use the DIY Sony VFET I won in the lottery for the top end (about 2000 MHz and up), what should go on the bottom?

1000 watt class D amplifiers are a common suggestion for the bass, but pairing that to a 10 watt amplifier seems like a mismatch to me. I have a 50 watt IcePower ASX50 gathering dust. Would that make a better pairing?

My speakers are > 96 dB sensitive.

Curious what other 6-24 users are employing....
 
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