Guide for active crossover for Prodigy?

[DanR]

Is it worthwhile to crossover the panels too, or not so much to be gained there?

This is exactly the point I’m at now Robert. It’s also the point where I don’t know the answer to that question. From what I understand the panel covers everything in the frequency range above the crossover point (250 Hz) for the Odyssey and Prodigy models. So what there is to be gained by being able to control that point I’d love to hear an explanation on too. And there may be more advantages in doing this also that I don’t understand yet. I’m sure the more knowledgeable guys here can explain this.

 

[Russr]

Sorry if I am being dense, but in the diagram posted earlier, it shows different driver sizes (8" and 10") , along with different impedances (4 Ohm & 8 Ohm) for the 2 drivers. ML documentation shows 2 X 10" drivers. So, which is it?

Also, I'm going to assume that the ML configuration is that of a bipole, as that is the core concept behind the whole "balanced force" thing that future ranges and subwoofers were based on?

 

[DanR]

Sorry if I am being dense, but in the diagram posted earlier, it shows different driver sizes (8" and 10") , along with different impedances (4 Ohm & 8 Ohm) for the 2 drivers. ML documentation shows 2 X 10" drivers. So, which is it?

Also, I'm going to assume that the ML configuration is that of a bipole, as that is the core concept behind the whole "balanced force" thing that future ranges and subwoofers were based on?

Russr, you are putting way way too much emphasis on the diagram. I don’t wan to speak for Tosh but I’m sure he put that up there as an example or reference. It IS NOT a diagram of a Prodigy xover, it looks to me like it is a diagram of an Odyssey xover which is what I have it has a 8” front woofer and a10” rear woofer. But the size and impedance of 8 or 4 ohms doesn’t matter. Your Prodigy has 2 10” woofers one is an aluminum cone driver and the other is a stiff fiber cone driver, I’m not sure on the impedance because Logan doesn’t make that available in their specs. If you go with the active crossover the impedance difference if there is any in the Prodigy doesn’t matter at all, any imbalance in volume can easily be adjusted with the gain knobs on the amps, believe me I’m using a 4 ohm and an 8 ohm woofer in my Odysseys and it works out just fine. Those crown amps are capable of driving either impedance speaker.

 

[Russr]

Thanks, DanR. My taking the diagram too literally is more based on my trying to figure out the tuning of, (and signals presented to) the 2 bass drivers and their respective enclosures (taking into account volumes, resonant frequencies, etc.).

If The ML BF design (and its forebears, which I assume the Prodigy and Odyssey bass sections are) is fundamentally a Bipole one, I'm trying to figure out the implications of each being driven by different outputs from a passive X-over (or separate amps driving different frequencies).

Sorry for belaboring this, just trying to develop a sense for it.

 

[Robert D]

Russr, you are putting way way too much emphasis on the diagram. I don’t wan to speak for Tosh but I’m sure he put that up there as an example or reference. It IS NOT a diagram of a Prodigy xover, it looks to me like it is a diagram of an Odyssey xover which is what I have it has a 8” front woofer and a10” rear woofer. But the size and impedance of 8 or 4 ohms doesn’t matter. Your Prodigy has 2 10” woofers one is an aluminum cone driver and the other is a stiff fiber cone driver, I’m not sure on the impedance because Logan doesn’t make that available in their specs. If you go with the active crossover the impedance difference if there is any in the Prodigy doesn’t matter at all, any imbalance in volume can easily be adjusted with the gain knobs on the amps, believe me I’m using a 4 ohm and an 8 ohm woofer in my Odysseys and it works out just fine. Those crown amps are capable of driving either impedance speaker.

How do you decide where to set the gain on the 2 woofers? Is there some kind of DSP program that helps with that? Maybe just use a meter to match the dB output?

 

[DanR]

How do you decide where to set the gain on the 2 woofers? Is there some kind of DSP program that helps with that? Maybe just use a meter to match the dB output?

Hi Robert, you are probably going to be surprised by this. For me I set up my multiple subwoofers using REW, I did this 5 years ago and my room hasn't changed at all so I don’t need to make any changes there, they handle the frequencies from 20Hz to about 80Hz and in that range it plays dead flat +\- 0dB. I ran the REW with a mic set at ear level from my listening position.
For the woofers in my Odysseys I use this crazy device I’ve had for ever it’s a two piece design, one piece on each side of my head…hahahahahahahaha yep I set the gain matching by ear to what sounds best to me. And for me that is the biggest advantage to the active crossover. I’ve played around with the crossover frequency points and slopes and types on my behringer I have the choice of (Linkwitz-Riley, Butterworh, Bessemer) all with slopes of either 6,12,18,24 dB.
What I do is simply turn the main amp off and play music thru the woofer amps and try all different combinations to find WHAT I LIKE BEST. It sounds crazy but it works great.

 

[DanR]

Thanks, DanR. My taking the diagram too literally is more based on my trying to figure out the tuning of, (and signals presented to) the 2 bass drivers and their respective enclosures (taking into account volumes, resonant frequencies, etc.).

If The ML BF design (and its forebears, which I assume the Prodigy and Odyssey bass sections are) is fundamentally a Bipole one, I'm trying to figure out the implications of each being driven by different outputs from a passive X-over (or separate amps driving different frequencies).

Sorry for belaboring this, just trying to develop a sense for it.

Oh don’t be sorry for anything Russr, questioning things is how we learn, and your questions are very well founded. I had a lot of these same questions before I dove head first into this. The funny part to me is the fact that you are hitting all around EXACTLY the reasons the passive crossover is SO LACKING, and why the active makes such a big improvement IMO of course. The factory xover is trying to do way way too much with way way to little and the results are not good.
I need to shut up here and let some of these guys that are much more into this whole process add some of their insight they are a wealth of knowledge and info on this.

 

[Robert D]

Hi Robert, you are probably going to be surprised by this. For me I set up my multiple subwoofers using REW, I did this 5 years ago and my room hasn't changed at all so I don’t need to make any changes there, they handle the frequencies from 20Hz to about 80Hz and in that range it plays dead flat +\- 0dB. I ran the REW with a mic set at ear level from my listening position.
For the woofers in my Odysseys I use this crazy device I’ve had for ever it’s a two piece design, one piece on each side of my head…hahahahahahahaha yep I set the gain matching by ear to what sounds best to me. And for me that is the biggest advantage to the active crossover. I’ve played around with the crossover frequency points and slopes and types on my behringer I have the choice of (Linkwitz-Riley, Butterworh, Bessemer) all with slopes of either 6,12,18,24 dB.
What I do is simply turn the main amp off and play music thru the woofer amps and try all different combinations to find WHAT I LIKE BEST. It sounds crazy but it works great.

Nice. Thanks for the explanation. That makes a lot of sense to me. That's great that you can chose which crossover slope to use too. I'm assuming the Crown amps can do that also.

 

[Robert D]

Oh don’t be sorry for anything Russr, questioning things is how we learn, and your questions are very well founded. I had a lot of these same questions before I dove head first into this. The funny part to me is the fact that you are hitting all around EXACTLY the reasons the passive crossover is SO LACKING, and why the active makes such a big improvement IMO of course. The factory xover is trying to do way way too much with way way to little and the results are not good.
I need to shut up here and let some of these guys that are much more into this whole process add some of their insight they are a wealth of knowledge and info on this.

Do you use an active crossover on the panels as well?

 

[Tosh]

The diagram shows differently sized drivers with different impedences... help?!

Until you find your glasses:

 

[DanR]

Do you use an active crossover on the panels as well?

No just the woofers

 

[Russr]

Until you find your glasses:

Dagnabbit! Hate it when I do that! Thanks!

 

[DanR]

Until you find your glasses:

View attachment 24276

I must need my eyes checked too, the original attachment even says Prodigy low pass on it

 

[18000rpm]

Some interesting info about the woofers:

The bass module is a sealed dual-woofer design. The forward-facing 10" ScanSpeak aluminum-cone woofer carries the bass audio signal. An independently enclosed, 10" ScanSpeak fiber-cone cone faces to the rear and is driven by a circuit that processes level, phase, and frequency range to create a partial cancellation of the front woofer's output in the lower frequencies (footnote 2). This ForceForward technology specifically reduces the common 50Hz null and 100Hz peak found in many rooms. For those requiring more forward bass, the Prodigy has a rear-panel switch for increasing the below-50Hz response by 3dB.

(From MartinLogan Prodigy Stereophile review)

The front woofer has ~80Hz high pass in addition to the main 250Hz low pass.

Why would the front woofer have a 80Hz high pass when the speaker plays down to 28Hz, unless only the rear woofer is handling deep bass?

 

[Robert D]

Anyone know why the back woofer isn't identical to the front? Wonder why its paper and the front aluminum.

 

[DanR]

Some interesting info about the woofers:

The bass module is a sealed dual-woofer design. The forward-facing 10" ScanSpeak aluminum-cone woofer carries the bass audio signal. An independently enclosed, 10" ScanSpeak fiber-cone cone faces to the rear and is driven by a circuit that processes level, phase, and frequency range to create a partial cancellation of the front woofer's output in the lower frequencies (footnote 2). This ForceForward technology specifically reduces the common 50Hz null and 100Hz peak found in many rooms. For those requiring more forward bass, the Prodigy has a rear-panel switch for increasing the below-50Hz response by 3dB.

(From MartinLogan Prodigy Stereophile review)



Why would the front woofer have a 80Hz high pass when the speaker plays down to 28Hz, unless only the rear woofer is handling deep bass?

That is not quite the case, it is not a sealed dual woofer design. It is TWO independently sealed enclosures, the panel that goes vertically in the middle of the bass module splits the front and back halves into independent sealed enclosures for each woofer which explains why two different woofers were used. The speakers have their own parameters controlled by that passive xover. I myself believe this was logans way of trying to match the bass output to the panel which was the thing that always drove me crazy, it NEVER sounded right period. They have finally figured out the only way to do it right was to what they did with the masterpiece series and control the woofers with their own amps and room correction. Why didn’t they do this earlier on it’s real simple, it’s a money thing which is what running a business is all about. a pair of 15A speakers are 26k which is out of a lot of people’s budget but they obviously have found a way to make it profitable now. It’s at least good to see them do it right finally, because the end product finally sounds RIGHT.

 

[JonFo]

Is it worthwhile to crossover the panels too, or not so much to be gained there?

It is very much worth it, but it adds complexity and a requirement for a very stable amp, such as the Sanders ESL amp.

There is more to be gained from going active on the low end, as the passives are truly nasty. So a hybrid of active bass and passive high-pass is a decent compromise and yields great improvements.

But all active is the end game. A driveRack Venue360 would be the ideal speaker processor for a dual-woofer ESL, as it can be configured with 3 outputs per channel.

 

[DanR]

Thanks for posting that JonFo, I am considering going active on the panels too. Let me ask you this. I use a Krell KSA 100 MKII class A amp in my system. This amp was completely gone over, recapped, and brought to original specs 1 year ago, it’s basically like new inside and out (see pics). Do you consider this amp to be sufficiently stable to go active on the panels with, I’m thinking it should be up for the task no problem but I’d love your opinion on that.

 

[DanR]

Also JohnFo what can I expect as improvements in sound if I go this route as opposed to the sound thru the passive unit to the panels as it is now. And what exactly is involved in making this change, besides disconnecting the passive crossover, and adding an active controller.?

 

[Robert D]

It is very much worth it, but it adds complexity and a requirement for a very stable amp, such as the Sanders ESL amp.

There is more to be gained from going active on the low end, as the passives are truly nasty. So a hybrid of active bass and passive high-pass is a decent compromise and yields great improvements.

But all active is the end game. A driveRack Venue360 would be the ideal speaker processor for a dual-woofer ESL, as it can be configured with 3 outputs per channel.

Does going active on the panel place even more demand on the amp? Not sure why.