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Old 30th January 2015, 09:58 AM   #1
microx is offline microx  Spain
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Default optimising a Zen design to specific drivers

Hi, I run a four way actve system with all drivers connected directly to their respective amplifiers. I would like to try some Zen for mid and treble and I am thinking how I should best match the output to the drivers. I dont mean only limiting the frequency response with smaller value coupling capacitors but rather the pairing of amp to driver so the most effective use is made of the limited power. Are there any calculations which can be made using the parameters of the driver, Pass Labs speakers have their amps optimised to the drivers, can I do the same?
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Old 30th January 2015, 05:09 PM   #2
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Quote:
Originally Posted by microx View Post
Hi, I run a four way actve system with all drivers connected directly to their respective amplifiers. I would like to try some Zen for mid and treble and I am thinking how I should best match the output to the drivers. I dont mean only limiting the frequency response with smaller value coupling capacitors but rather the pairing of amp to driver so the most effective use is made of the limited power. Are there any calculations which can be made using the parameters of the driver, Pass Labs speakers have their amps optimised to the drivers, can I do the same?



Hi Microx, which crossover system you plan use. Digital, Analogue.
Regards from Menorca.
Esteban
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Old 30th January 2015, 06:15 PM   #3
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You can decide how much power you want and pick a supply voltage and
bias current accordingly for that load impedance.

You can decide how much distortion you want, which might cause you to
raise the bias and the supply voltage.

You can decide what damping factor you want and set your feedback
for that figure.

You can decide how much gain you need, but if you are also adjusting for
damping factor then you might have to adjust gain before the amplifier.

There are other factors, but these are the most obvious.

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Old 30th January 2015, 09:42 PM   #4
OllBoll is online now OllBoll  Sweden
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If you will cross high enough to the mid ( say ~ 2 octaves above driver fs ) then a good idea is to make the Zens current sources.

The advantage of current sources is that impedance variation related distortion just disappears, so drivers without shorting rings perform as good as those with. Many pro drivers don't have copper in the motor but just go for pure efficiency, those are a match made in heaven as the current source just takes care of all that. My 6ND430 perform crazy good with my Zen-ish current source amps =)

On the amp side apart from that then you can always just use smaller output caps and input caps. And in my case my amps are inductor loaded so I have smaller inductors for my tweeter amps. (Hammond 193V for mids and 193T for tweets)
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Old 1st February 2015, 09:04 AM   #5
microx is offline microx  Spain
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Thanks for the replies. Esteban, I have three crossovers, Behringer 3 way stereo analogue, minidsp 8 bit (noisey) and minidsp 24bit 4 way.

Nelson, thanks for the pointers, as my first Zen will be for HF where damping is much less important I think I will go for 5 watts power and to start with no feedback, then later for mids a bit more power and an input buffer so I have gain to play with when I apply feedback.

OllBoll, yes they will be current source, I cross at 250-275hz to mids so within your parameters. I have never used inductive loading with solid state , valve stuff yes. Must give it a try
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Old 1st February 2015, 01:04 PM   #6
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Dear Mr Pass, thanks for your "always on" for help people with your valuable time, maybe me, or somebody a newbie like me , can not take all the essence that you spread. But with the respect I deserve to you, could you explain "The How to" in change your electronic designs, both: Damping, IE playing with distortion, gain and further, the current and the voltage for determinate load.
Undoubtedly for Microx system like , is easy for match this and put down not only the IM distortion and could be more feasible in multiamps than in a full range systems.
Thanks a lot for your generosity and thanks to other Gentlemen who spread their knowledge
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Old 1st February 2015, 06:02 PM   #7
OllBoll is online now OllBoll  Sweden
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Quote:
Originally Posted by microx View Post
Thanks for the replies. Esteban, I have three crossovers, Behringer 3 way stereo analogue, minidsp 8 bit (noisey) and minidsp 24bit 4 way.

Nelson, thanks for the pointers, as my first Zen will be for HF where damping is much less important I think I will go for 5 watts power and to start with no feedback, then later for mids a bit more power and an input buffer so I have gain to play with when I apply feedback.

OllBoll, yes they will be current source, I cross at 250-275hz to mids so within your parameters. I have never used inductive loading with solid state , valve stuff yes. Must give it a try
Feedback loops... but that makes it so complicated! An option is to just increase the source resistor on the midrange amp as degeneration is a form of feedback. Just make sure that the bias supply goes through a high resistance to keep it a current source amp.

And if you still want a feedback loop then make sure you do a current feedback loop and not a voltage one, or you will reduce the nice and high output impedance. But here a source resistor of say 2 ohm is probably easier as you won't need as wide bandwidth so you can up the source resistor some.

If you use inductor CS then output watts won't be much of an issue, I get 10W into 8 and 16 ohm for ~ 44W of dissipation on my JFets. ( 2.2A @ 20V ). Much more efficient than my F2J =)

If you want better distortion performance then just PM semisouthfan and buy som R125s, I think he still has a supply.
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