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Old 30th May 2008, 02:15 PM   #1
mjon is offline mjon  Sweden
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Question ESL transformer questions

I'm in the process of rebuilding my Martin Logan Ascent speakers. The plan is to remove the passive crossover and instead use an active DSP based crossover. First step however is to just go active on the woofer side and keep the passive crossover on the panel and step 2 will be full active drive. I'm also thinking about testing some other transformer (Amplimo).

That's the plan, but I have run into some problems and I have some questions, which basically are general ESL related.

1) On the input side of the transformer in the speaker there are three connections (Red, Brown, Black) while on other transformers such as Amplimo there are only two (Blue, Black on Amplimo). What's the deal here? See the links below. The crossover in the link is from another ML model but you see the brown input connection on the transformer there as well. In my speaker however there is only a single coil (no other components) connected to brown and the other side of the coil is connected to black.
http://www.martinloganowners.com/request_xo.pdf
http://www.amplimo.nl/download/ST105PP.pdf

Is it possible to replace the transformer with an Amplimo and what should I then do with the coil that is now connected between brown and black on the original transformer? The natural thing for me would be to place it between blue and black on the Amplimo as a "normal" coil in a 2nd order HP-crossover. Is that correct, and can I then keep the original value of the coil?


2) Lets say I have a transformer with ratio 1:75 and I replace it with 1:50 or 1:100. What will happen? Will it for example affect the crossover function of the existing crossover?


I hope that someone here can clear the fog a bit...

/Magnus
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Old 31st May 2008, 02:14 AM   #2
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Default Hey somebody else kinda had my idea...

If you look at the bass transformer of an Acouustat you will see that it has three input windings that get used for varous numbers of panels. I have found that you can dive the primary of this transformer at two (or more) taps at the same time. I see that Martin Logan were thinking the same good for them. If you go to Russ's site he can build you such a transformer or you can buy one used or you can buy one from Galaxy Transformer new about the same price as Russ. Any how that will only take care of your bass but you will need a nid /high frequency transformer as well. Take a look at the Acoustat schematic at the Izzy Wizzy site.
I have no idea if you really want to mess with all this. my advice is don't but that never stopped me (often). I would buy an Acoustat transformer interface used and go from there but that's just me. ML seem to make things as complex as they can and they use a lot of parts to get the job done. I would not miss (replace the m with a P) with this interface I woud do what I said . Good luck buddy. We can chat PM if you like.
http://eslrepair.com/default.aspx
http://www.izzy-wizzy.com/audio/spkr.html
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Old 31st May 2008, 10:03 AM   #3
Calvin is online now Calvin  Germany
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Hi,

Iīd recommend to read this thread. It should answer most of Your Qs.

jauu
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Old 31st May 2008, 11:46 AM   #4
mjon is offline mjon  Sweden
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Sounds good but which thread? Link?

/Magnus
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Old 31st May 2008, 12:39 PM   #5
Calvin is online now Calvin  Germany
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Hi,

uups...this one: Martin Logan frequency correction???

jauu
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Old 1st June 2008, 08:31 AM   #6
mjon is offline mjon  Sweden
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I've read that thread many times during the last days and it's really a great thread. Many interesting measurements and information but it doesn't really answer my questions (at least I don't think so...).

I've kind of figured out question number 2 but number 1 still remains. The transformer in my speaker has three primary taps but other replacement transformers, for example Amplimo, only has two. Is it then possible to replace the original transformer with an Amplimo and keep the original crossover?

What was the case with Prodigy and Sequel that you have measured with Amplimo? Did they also have three primary taps (red, brown, black), and in that case how did you connect the Amplimo?

BR
Magnus
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Old 1st June 2008, 08:55 PM   #7
Calvin is online now Calvin  Germany
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Hi Magnus,

all MLs I came across yet featured quite heavy equalization. The third wire on the primary is used together with the associated crossover components for this purpose.
Without deeper analysis I assume that this network equalizes the ground resonance of the panel or fills the dip caused by phase cancellation.
With a 2 pole primary You have to use a different circuit to achieve the same goal.
So the answer to Q1 is: No, but You may be lucky to use the inductance together with a new filter structure running into a 2-pole primary like the Amplino has.

The old Sequel had a 2-pole primary. The measurements and sims in the link stem from this. I donīt know about the Prodigy since I just had the panel for comparison purposes.
Itīd be probably best to measure what the single branches of the network actually do (electrical freq-response) and based on this to configure the filtering of the DSP and running the original tranny 2-pole or trying with a new tranny.

jauu
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Old 21st June 2008, 05:12 PM   #8
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This is simple enough.

If you use a single transformer on an ESL intended for wide range, you end up with a problem. The problem is that if you match for wide range, you get lower SPL. If you match for best SPL you get narrow range.

So what do you do?
Most ended up with some sort of EQ to boost the highs.

Acoustat found another way.

There's a patent from Audiostatic that tries to do the Acoustat trick and bypassing their patent - but apparently it didn't really work (??) because they don't actually use it in their speakers! Not sure why though - it looks ok to the unaided eye.

IF ur going DSP, you don't need passive xovers at all??
IF ur going DSP you don't need EQ in the speaker at all??

You get to decide what way to go.




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