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Active crossover for Prodigy

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R

Rothen

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Hello Martin Logan Fans,

I'm a proud owner of a Martin Logan Prodigy. I already modified it by activing the bass and using only one high end bass chassis (Audio Technology). The two standard bass drivers caused only trouble - too much bass - in my small room.

Now I consider the option to use also a active crossover (24db) for the tranducer. Does anyone have experience? Since I use a digital preamplifier with room correction I can correct a lot concerning the frequency response, so I don't need a flat frequency responce. I think that makes it easier. Since I have a stable amplifier (Classe) I also can live with low impedancies.

Here are the major questions I have:
- in each of the both parallel applied transformers of the Prodigy 3 cables ar going in: red, brown and black - why 3 instead of 2? Can I connect red and brown when connecting the amplifier to the transformers?
- Do I need a resistor (which value) between transformer and amplifier to avoid a too low impedance?
- Are there other problems which will arise?
- When I apply 24db separation what would be the ideal frequency to separate: 250 HZ?

Your help is appreciated.

Volker Rothenpieler
 

roberto

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Rothen said:
Hello Martin Logan Fans,

I'm a proud owner of a Martin Logan Prodigy. I already modified it by activing the bass and using only one high end bass chassis (Audio Technology). The two standard bass drivers caused only trouble - too much bass - in my small room.

Now I consider the option to use also a active crossover (24db) for the tranducer. Does anyone have experience? Since I use a digital preamplifier with room correction I can correct a lot concerning the frequency response, so I don't need a flat frequency responce. I think that makes it easier. Since I have a stable amplifier (Classe) I also can live with low impedancies.

Here are the major questions I have:
- in each of the both parallel applied transformers of the Prodigy 3 cables ar going in: red, brown and black - why 3 instead of 2? Can I connect red and brown when connecting the amplifier to the transformers?
- Do I need a resistor (which value) between transformer and amplifier to avoid a too low impedance?
- Are there other problems which will arise?
- When I apply 24db separation what would be the ideal frequency to separate: 250 HZ?

Your help is appreciated.

Volker Rothenpieler
Hola Volker, welcome to the club. I think that you might have a low charge stat panels problem. Also to get rid of some bass energy, your Prodigies must be set at least one meter away of theirs back wall.
What you are trying to do, it is not an easy task. Before you do all the electronic work, why don't you try to use two amplifiers, one with volume control (for bass) to match the sensitivity of the panels wersus woofers?... using the same Prodigies crossover. Yes, the frequency cut is done at 250 Hz. Your question regarding why there are three cables? It is because you have a truly push pull speaker. You have positive pulse and negative pulse. A positive bias is placed at the panel diaphragm (around 7KV) and the transformers modulate the stators, one that face you (positive) and the other that face their back wall (negative), and then the speaker starts to work...two transformers also, they are in paralell connection, so better highs are achieved. If need better assistance, try to contact ML...they will help you with your project...hope this can help...happy listening,
Pura vida,
Roberto.
 
R

Rothen

Guest
roberto said:
Hola Volker, welcome to the club. I think that you might have a low charge stat panels problem. Also to get rid of some bass energy, your Prodigies must be set at least one meter away of theirs back wall.
What you are trying to do, it is not an easy task. Before you do all the electronic work, why don't you try to use two amplifiers, one with volume control (for bass) to match the sensitivity of the panels wersus woofers?... using the same Prodigies crossover. Yes, the frequency cut is done at 250 Hz. Your question regarding why there are three cables? It is because you have a truly push pull speaker. You have positive pulse and negative pulse. A positive bias is placed at the panel diaphragm (around 7KV) and the transformers modulate the stators, one that face you (positive) and the other that face their back wall (negative), and then the speaker starts to work...two transformers also, they are in paralell connection, so better highs are achieved. If need better assistance, try to contact ML...they will help you with your project...hope this can help...happy listening,
Pura vida,
Roberto.
Roberto,

thank you for your quick reply.

To be honest: I really love Martin Logan because of their panels, I'm not convinced concerning their woofer constructions. I don't like the Force Forward, I get a more precise bass if only using one activated woofer - at least in my room, which is a small one. There are some competitors in the market with a woofer quality I like more.

By the way: I bought the first Prodigy in Germany and detected some time later that the front and rear woofer cabinet, which should be separated, were not separated because their was a small hole in the clue where the cable are going through the separation board. A bug in the production. So if your bass of the Prodigy is not OK, check whether the back woofer moves when you move the front woofer by hand!

Concerning the active cross over for the panel: The fact that the speaker is a push pull speaker seems to make it impossible or at least very very difficult to activate the panel. So I assume effort and possible improvement seems to be not in balanced relationship. But any other experience concerning "active" is welcome!

Another comment to that: I already modified the passive crossover by replacing the capacitors in the signal path (Solen) by Mundorf MCap-Supremes. See mundorf.com. A huge improvement! A good investment and not very complicated to implement. I and also Mundorf have the circuit of the cross over and the specification what to replace - so in case of interest I or Mundorf can help.

Volker
 

miljac

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Hi Volker,

how about the Ascent crossover?
Have been thinking of tweaking the crossover with Mundorf components.

miljac
 
R

Rothen

Guest
Miljac,

I don't know the circuit of the Ascent. But I assume the positive effect will also happen for the Ascent. Mundorf offer an upgrade service - you send them the crossover, they do the upgrade. Another option is "reading" the crossover and implementing the upgrade by yourself. Take care that you have enough space for the MCap Supremes, for equal values they need far bigger dimensions, see specifiations at mundorf.com.

Volker
 

roberto

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Rothen said:
Roberto,

thank you for your quick reply.

To be honest: I really love Martin Logan because of their panels, I'm not convinced concerning their woofer constructions. I don't like the Force Forward, I get a more precise bass if only using one activated woofer - at least in my room, which is a small one. There are some competitors in the market with a woofer quality I like more.

By the way: I bought the first Prodigy in Germany and detected some time later that the front and rear woofer cabinet, which should be separated, were not separated because their was a small hole in the clue where the cable are going through the separation board. A bug in the production. So if your bass of the Prodigy is not OK, check whether the back woofer moves when you move the front woofer by hand!

Concerning the active cross over for the panel: The fact that the speaker is a push pull speaker seems to make it impossible or at least very very difficult to activate the panel. So I assume effort and possible improvement seems to be not in balanced relationship. But any other experience concerning "active" is welcome!

Another comment to that: I already modified the passive crossover by replacing the capacitors in the signal path (Solen) by Mundorf MCap-Supremes. See mundorf.com. A huge improvement! A good investment and not very complicated to implement. I and also Mundorf have the circuit of the cross over and the specification what to replace - so in case of interest I or Mundorf can help.

Volker
Hola Volker...in my case, I'm jsut a CLS IIz lover and no woofers around...and I don't like too much bass energy in my room. Also my room is small, so with the bass that my CLS produces, are just enough, I rather have quality than quatity, you should try to get one pair of CLS...so thanks for your offer...happy listening,
Pura vida,
Roberto.
 

Bruce Weiland

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Rothen said:
Roberto,

Another comment to that: I already modified the passive crossover by replacing the capacitors in the signal path (Solen) by Mundorf MCap-Supremes. See mundorf.com. A huge improvement! A good investment and not very complicated to implement. I and also Mundorf have the circuit of the cross over and the specification what to replace - so in case of interest I or Mundorf can help.

Volker
Volker,

Now that is has been a while since you replaced the caps, can you tell me how the Prodigy, with broken in caps, sound compared to the Solen caps?

What front-end source and electronics do you have?

What cap values, how many caps and what approximate cost?

Thanks for the reply.

Bruce

P.S. Plan to be in Germany late July to pick up oldest daughter who is currently studing in Gottening.
 

Bruce Weiland

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I haven' heard from you Volker? Are you still around? :confused:

I would like your input on Prodigy passive part upgrade.

I will be in Germany in late July. I am hoping to pick up some caps while there.

Thanks for the reply.

Bruce
 

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