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Brandon Hartwick

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I recently defeated the internal woofer crossover in my Aerius i's and drove it with its own amplifier with an active electronic crossover. This modification totally brought these speakers to a whole new level. This is how the bass is handled in the newer Martin Logan models. Below I will show everyone how it's done and what equipment you need.

To do this you will require an amplifier with internal DSP crossover capabilities. The easiest way to do this is with modern Class D professional audio amps, I'm my case I've picked a Crown XLS Drivecore 1002, these are very good sounding Hypex amps. I bought this nearly new for $275.

We will need to open up the back the speaker to get at the the woofer and binding posts. The back panel can be very stuck and can be tricky to get off. I found by hammering a razor blade into the gap between the door and cabinet broke the seal without damaging anything.
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After you get the panel off you will need to run a set of wires straight from the lower set of binding posts to the woofer. In my case I decided to add another set of binding posts for this purpose. CHECK YOUR POLARITY, in my case the woofer in the Aerius i are wired out of phase inside the cabinet, this is verified by crossover schematics.
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Here you can see the new posts. If you can't solder you could probably get some of those little copper spades and just clamp them under the binding post nuts.
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After you get everything back together get your new amp hooked up, you will need to use a Pre-out on your pre-amp or receiver to feed a full range signal.

Turn the gains all the way down and turn everything on, setup your crossover slopes the same as factory to start. In my case I have a bandpass crossover setup at 450 Hz and 80hz, I'm running a subwoofer the the bandpass feature is awesome.
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After you get everything setup the way you like play some music and setup the gains to a comfortable level, go listen and repeat until you get them where you like. This took my less than 1 track to get them set so don't overthink it.

Closing thoughts: You can do this with DSP plate amps, or you can buy pro audio processors and output to other amplifiers. But both of these options are many times more expensive than this and more complicated. There are several other models of pro audio amps that have more extensive DSP capabilities, but again, more expensive. With an active crossover and gain control it would be easy to try different woofers and be able to blend them easily.
 

Robert D

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So, when using rca cables, I'm guessing you have to use a splitter to turn a single output wire into 2. One for the woofer amp and another for the amp that powers the panel?

Same for balanced. Do they make good quality splitters so that you don't lose quality when splitting it?
 

Robert D

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Does your Aerius have dual woofers? I guess having two should not complicate matters too much.

I worry about taking a rear panel off. Couldn't that end up lose and then rattle or let air escape during bass output? I had an air leak on my depth sub that required work.
 

Tosh

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RobertD, here's the beginnings of going active bass on Prodigy:

 

Brandon Hartwick

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So, when using rca cables, I'm guessing you have to use a splitter to turn a single output wire into 2. One for the woofer amp and another for the amp that powers the panel?

Same for balanced. Do they make good quality splitters so that you don't lose quality when splitting it?
In my case I have 3 sets of pre-outs on my pre-amp, if you don't you can use splitters no problem. I used splitters for the longest time before this preamp.
 

Brandon Hartwick

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Does your Aerius have dual woofers? I guess having two should not complicate matters too much.

I worry about taking a rear panel off. Couldn't that end up lose and then rattle or let air escape during bass output? I had an air leak on my depth sub that required work.
The aerius only have one woofer each, with 2 woofers you could it should be the same depending on how the crossover runs each of them.

Taking the panel off is easy, it's held on by a bunch of screws so it's really secure. If you're concerned put some gasket tape around the edges, that's what I did.
 

Robert D

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RobertD, here's the beginnings of going active bass on Prodigy:

Looks like I'd need 2 different amps with their own crossovers. One for the front speakers and one for the rear. Guess each amp wouldn't need to be too powerful then. Thanks for the info. I see a schematic there.

Maybe I'm wrong about needing 2 amps? The thread says I need a 2 way active crossover. Not sure what a 2 way is
 

Brandon Hartwick

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Looks like I'd need 2 different amps with their own crossovers. One for the front speakers and one for the rear. Guess each amp wouldn't need to be too powerful then. Thanks for the info. I see a schematic there.

Maybe I'm wrong about needing 2 amps? The thread says I need a 2 way active crossover. Not sure what a 2 way is
Just means you need 2 crossover channels per speaker, so 2 amps. The amp I'm using has 2 channels and both channels have active crossovers.

I'm my case, the difference was pretty substantial.
 

DanR

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Ok I need to ask this. Tosh is it possible on the Odyssey or Prodigy to use just one of the two woofers on each speaker? I have Odysseys and have a subwoofer system that I run with them tuned with REW from 20hZ-110hZ so I’m wondering if there would be any harm with possibly replacing the 10” woofer and running that alone with a crown amp/crossover? I’m hoping that I would be able to pick a woofer of my choice to the specs of my choice in a 4 ohm speaker.
 
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With an active crossover and gain control it would be easy to try different woofers and be able to blend them easily.
Correct, the flexibility this allows is massive. Thanks for the write-up.

One item you did not mention is delay management, as it is useful to time-align the impulse response of the woofer and the panel, especially around the XO frequency. Only higher-spec models or external processors deal with that. But it's icing on the cake.
 

Tosh

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DanR, I attached a combo of the Odyssey bass xo and bass drivers' specs. This spec sheet describes both the front 8 inch woofer and the rear 10 inch woofer as being paper cone, but iirc later Odysseys used the awesome 10 inch aluminum cone from Ascent i? So if yours have the aluminum cone 10 inch, then I don't feel that woofer itself can be improved upon.
On both Odyssey and Prodigy the rear woofer is crossed lower than the front woofer (as the front woofer plays up into the lower mids and joins the ESL), so I could even imagine forgoing the rear woofer altogether if you had a sub.
To try to answer the question, yes, you could run either woofer separately if you bypassed the passive xo and added the needed binding posts. Happy to discuss further....
 

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Tosh

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I'm my case, the difference was pretty substantial.
I can just imagine, Brandon! Unrecognizable, right? I have a friend with Aerius and I'm trying to get him to appreciate the difference. Great job!

With active bass, it's also really handy to have access to the bass level control (bass amp input level) for adjusting bass preference or correcting certain recordings, but with Aerius i being crossed fairly high at 450Hz, perhaps this is not as simple or effective as with SL3 and Ascent (250Hz and 280Hz)?

I've also gone active bass on my previous SL3 and now with my Ascent'i', and indeed the improvement is staggering: bass is low and tuneful, and quick like the ESL (no overhang, no boom). And to think that the bottleneck is >entirely< the series inductor in the passive xo causing the amp to lose control of the woofer in a passive low pass xo...
 

Brandon Hartwick

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I can just imagine, Brandon! Unrecognizable, right? I have a friend with Aerius and I'm trying to get him to appreciate the difference. Great job!

With active bass, it's also really handy to have access to the bass level control (bass amp input level) for adjusting bass preference or correcting certain recordings, but with Aerius i being crossed fairly high at 450Hz, perhaps this is not as simple or effective as with SL3 and Ascent (250Hz and 280Hz)?

I've also gone active bass on my previous SL3 and now with my Ascent'i', and indeed the improvement is staggering: bass is low and tuneful, and quick like the ESL (no overhang, no boom). And to think that the bottleneck is >entirely< the series inductor in the passive xo causing the amp to lose control of the woofer in a passive low pass xo...
It's crazy, it totally changed how the bass sounds, it's just so much cleaner and faster. You're right about the 450hz crossover, it doesn't really allow you to use gain as bass control.

I imagine with the DSP offerings of the more expensive amps you could really do some cool stuff with some of the dual woofer speakers. That's basically what the new masterpiece series does, 2 woofers with individual time alignment and DSP.
 
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