ReQuest Melted Crossover Inductor

[Asepguy]

So what you and the folks who are "liking" your statement appear to be saying is that statements which I clearly framed as personal concerns, are somehow being construed as "blanket incorrect" statements????? Seriously????!!!! The "blanket" covering is one sided and it's NOT from my side. You and the others of like mind are leaving absolutely no room for the possibility of any other solution other than what you want it to be. You are not open to the reality of the situation that it is possible some other piece of equipment can out perform a PA amp? And you accuse ME of making incorrect blanket statements? Please elaborate on how my statement is wrong instead of blindly repeating that sentiment over and over with no support. I'm happy to listen to what anyone has to say. But none of you are saying ANYTHING except attacking me for "false" or "blanket" statements with no basis or support for your argument. On top of that, you are not even listening to what I have said.

 

[Brandon Hartwick]

I don't think anyone's arguing that you can't do better than a PA amp, but it's definitely the easiest, most compact and cost effective solution. New PA amps also sound fantastic.

The only way I can see anyone surpassing this is to go with an external processor and a pair of power amps. But since the bass amp is only handling around 300hz and down its getting close to subwoofer territory and the differences are negligible (if you can even hear them at all). This way would allow you to use DSP on the panel to really dial the speaker into your room.

But using any amplifier through the passive crossover, regardless of how amazing it is, won't even get close to having an active Xover handling the bass, those are facts.

 

[Asepguy]

Thank you! I can appreciate what you are saying here, and it's much more in line with the question I originally asked - about crossovers. Talk more about that last sentence...what are you basing that on? Why would combining an active crossover with an arbitrary frequency range (not matched to the factory crossover network) create better sound? It seems to me you are guessing what frequency to set it to, and run the risk of duplicating some frequencies from both areas of the speakers at different roll off curves now that we are using two completely different crossovers. That is strictly a crossover discussion and does not even touch on the differences that come into play with gain matching the "subwoofer amp" to that of the main system amp or the drastic power difference that potentially would be induced by this modification.

 

[Brandon Hartwick]

Because the factory crossover is extremely rudimentary and has a very shallow slope that allows much overlap between the panel and the woofer. You need to keep in mind that a cone woofer behaves very different from an ESL panel and getting them to properly mesh together isn't easy to do with passive components.

Using active crossovers you can get slopes of 24db/octave or more, at any frequency, at any gain setting, with the ability to add delays for time alignment. This allows for LESS frequency overlap not more. The power difference doesn't matter because you set your gain on the amplifier. Subwoofer integration is also made easier because of bandpass filters within the digital crossover.

Many years ago Martin Logan offered an active crossover option on the Monolith as a very expensive upgrade. Newer technology allows us to do this at home with even better results.

 

[Asepguy]

The power difference doesn't matter because you set your gain on the amplifier.

This is where I am very skeptical, and wonder if you are assuming that the subwoofer amp is more powerful than the main stereo amp? What if it's the other way around...and by a large amount? I think I read in the specs for the crown amp that was mentioned it could put out 350W x 2 at 4 Ohms. My stereo amp offers 3 times that and has a sensitivity of 2.95V compared to 1.4 on the crown.
I do however, see benefits could be realized from changing the crossover network. It sounds like it would take a fair amount of trial and error to find the sweet spot though.

 

[Robert D]

This is where I am very skeptical, and wonder if you are assuming that the subwoofer amp is more powerful than the main stereo amp? What if it's the other way around...and by a large amount? I think I read in the specs for the crown amp that was mentioned it could put out 350W x 2 at 4 Ohms. My stereo amp offers 3 times that and has a sensitivity of 2.95V compared to 1.4 on the crown.
I do however, see benefits could be realized from changing the crossover network. It sounds like it would take a fair amount of trial and error to find the sweet spot though.

The $3500 Martin Logan BF 210 sub only has an 850 watt amp to push its two 10 inch woofers, so 425 w a piece. That's a class D. It doesn't specify what ohm load that is, it could be 4 ohms. I have one and that's more than enough power. The gain on it is at under 1/2.
https://www.martinlogan.com/en/product/balancedforce-210
The $29,000 15a speakers have 2 amp channels for each speaker 2 x 500 watts/channel (4 ohms).

 

[DanR]

I have found your last sentence about taking a fair amount of trial and error to get it “right” is right on the money. I replaced both the 10” and 8” woofers on my Odysseys and have been playing around with the settings for months now but I knew this going into it. I already had a DCX-2496 controller that has 6 channels on it for running my multiple subwoofer system so I was able to use the extra channels on that which makes it great for making changes. So if someone wants a plug and play type set up this may not be for them but for me the sonic benefits far outweigh the adjustments. I’ve also find if you make changes to the system like changing brands of cables I’ve had to make changes to the woofers to get it just right again.

 

[Asepguy]

I have found your last sentence about taking a fair amount of trial and error to get it “right” is right on the money. I replaced both the 10” and 8” woofers on my Odysseys and have been playing around with the settings for months now but I knew this going into it. I already had a DCX-2496 controller that has 6 channels on it for running my multiple subwoofer system so I was able to use the extra channels on that which makes it great for making changes. So if someone wants a plug and play type set up this may not be for them but for me the sonic benefits far outweigh the adjustments. I’ve also find if you make changes to the system like changing brands of cables I’ve had to make changes to the woofers to get it just right again.

Good to know! I get the concept of the whole idea. I have an early set of Definitive Technology speakers with powered subs from when they were a new company and Sandy Grossman was designing them - they are AMAZING sounding speakers. I'd love to have a set of the Golden Ears that he worked on as well. I think it would be easier to just run a powered sub/subs rather than have to spend months of tinkering to find the right balance. But I do get the fun of it as a hobby as well.

 

[Asepguy]

The $3500 Martin Logan BF 210 sub only has an 850 watt amp to push its two 10 inch woofers, so 425 w a piece. That's a class D. It doesn't specify what ohm load that is, it could be 4 ohms. I have one and that's more than enough power. The gain on it is at under 1/2.
https://www.martinlogan.com/en/product/balancedforce-210
The $29,000 15a speakers have 2 amp channels for each speaker 2 x 500 watts/channel (4 ohms).

I get that, and as I just posted to DanR I'm not against the concept of powered subs inside a speaker - I have a set of Definitive Technology towers that do it quite nicely. The difference in it being done from the factory, is they have already done the work of tuning the internal amp and the crossover. The modification puts that burden squarely on the shoulders of the person making the mods - not an easy plug/play task by any means.

 

[msimanyi]

This is where I am very skeptical, and wonder if you are assuming that the subwoofer amp is more powerful than the main stereo amp? What if it's the other way around...and by a large amount?

I am not an engineer, but have you checked the reQuest specs? On my 15As, I believe I recall seeing they can drop as low as 0.5 ohm in the upper frequencies. So one question might be what's the impedance of the panel vs the impedance of the woofer, as that will potentially play a role in balancing two different amps powering the two different drivers.

Also my understanding is that even playing VERY LOUDLY (for most people), only uses trivial amplifier power. Like, maybe you'll be pushing 4 or 5 watts. Get heroic and assume you'll push 100 watts, and both an insanely powerful amp and not-quite-insanely powerful amp - driving different speaker components - should be manageable.

Finally, if you're not using the crossover for the factory woofer, it occurs to me you can replace the woofer with one of your choosing, and select an appropriate spec. Might be a fun - and not very expensive - project with one of the non-esoteric amp/crossover products.



Edit: regarding my recollection of the 15A impedance, from this page:

The impedance plug-in for Fuzzmeasure 3 doesn't produce graphs of high enough quality to publish. However, using a 0.1%-tolerance 10 ohm resistor as a reference with the Fuzzmeasure plug-in, it looks as if MartinLogan's specifications of 4 ohms for the ESL 15A's impedance and 0.52 ohm at 20kHz for its minimum magnitude are correct.

 

[Brandon Hartwick]

If all you want to do is power the original woofers with a seperate amp with active Xover getting the sound dialed in is much easier than it is if you replace the original woofers with something else.

The original woofers will be matched to the panel from factory so you know they're going to blend well and not have a wild sensitivity difference. When I did this modification with OEM woofers it only took a few minutes to get the levels exactly where I wanted them. I'd honestly suggest leaving the original drivers alone unless something's wrong with them.

You're overthinking the rated power difference between the amplifiers and it's not really relevant anyway in this case. When driving the woofer separately you're no longer using the power sucking passive Xover and the woofer is connected directly to the amplifier. That speakers will almost certainly never see the full rated power of the amp, it would probably catch fire if it did.

 

[Brandon Hartwick]

My advice

Buy a used Crown, because it's by far the cheapest way to fix this speaker.

Maybe you'll hate it and your suspicions were right all along. Put the amp up for sale the next day and you'll get what you paid (maybe more).

 

[Robert D]

If all you want to do is power the original woofers with a seperate amp with active Xover getting the sound dialed in is much easier than it is if you replace the original woofers with something else.

The original woofers will be matched to the panel from factory so you know they're going to blend well and not have a wild sensitivity difference. When I did this modification with OEM woofers it only took a few minutes to get the levels exactly where I wanted them. I'd honestly suggest leaving the original drivers alone unless something's wrong with them.

You're overthinking the rated power difference between the amplifiers and it's not really relevant anyway in this case. When driving the woofer separately you're no longer using the power sucking passive Xover and the woofer is connected directly to the amplifier. That speakers will almost certainly never see the full rated power of the amp, it would probably catch fire if it did.

The crossover is only for the woofer, right? The panel is still running off of an internal crossover?

How did you know what to set the crossover at? Did it require the use of REW to get it right? Im curious because ive thought about doing this with my Prodigy speakers, but Im not very knowledgeable about some of these things, at least not like guys on this thread. If it was truly easy to set up the crossover then maybe I can do it without a big headache.

Are we able to find out what the ML speakers have their internal crossovers set at? The amount of improvement in sound for the low cost really has me intrigued.

 

[Brandon Hartwick]

The crossover is only for the woofer, right? The panel is still running off of an internal crossover?

How did you know what to set the crossover at? Did it require the use of REW to get it right? Im curious because ive thought about doing this with my Prodigy speakers, but Im not very knowledgeable about some of these things, at least not like guys on this thread. If it was truly easy to set up the crossover then maybe I can do it without a big headache.

Are we able to find out what the ML speakers have their internal crossovers set at? The amount of improvement in sound for the low cost really has me intrigued.

- the seperate amp with crossover is ONLY for the woofer, the panel runs off the original passive crossover

- the crossover frequency can usually be found in the owners manual, or through a little online research

- REW is not needed or required

You have Prodigys with 2 woofers per speaker so that makes things a little more complicated. You'd need 2 amps or a 4 channel amp, that might exist? If you're really interested PM me and I might be able to look into it.

 

[Robert D]

- the seperate amp with crossover is ONLY for the woofer, the panel runs off the original passive crossover

- the crossover frequency can usually be found in the owners manual, or through a little online research

- REW is not needed or required

You have Prodigys with 2 woofers per speaker so that makes things a little more complicated. You'd need 2 amps or a 4 channel amp, that might exist? If you're really interested PM me and I might be able to look into it.

Ok. If I get brave I will. One problem is I don't have room in my cabinet for more amps, but could probably figure something out. I'd probably just get 2 two channel amps, one for each speaker.
Mine sound pretty damn good now, but you guys have piqued my interest and made me wonder how much better they could sound!

 

[Leporello]

I'm reluctant to jump into this food fight, but I will. I won't shout "FACTS" in all caps, but the following is pretty much beyond reasonable dispute:

1. In engineering, almost everything involves trade-offs, in cost, various desired performance parameters, or both.

2. It's pretty much been acknowledged since almost the beginning of time that active crossovers offer performance advantages over passive ones--both theoretical and actual audible differences. Probably mostly in the former category today is the fact that two or more amps being driven with bandwith-limited signals will produce fewer intermodulation products, all other things being equal. More practical, perhaps, is that passive crossovers require large component values at the impedance speakers operate at. This usually necessitates bipolar electrolytic capacitors which, among other things, have crappy unit to unit consistency, and sometimes even iron core inductors, which are subject to hysterisis nonlinearities. Connecting each driver directly to a separate amplifier enables greater control of the speaker by the amp, especially important for dynamic woofers. Finally, active crossovers offer finer control over the crossover parameters. Even in the analog domain, 24dB/octave is no problem. You can have Butterworth, Linkowitz-Reilly, anything your heart desires. Thanks to elegant circuits like "negative inductors" and "gyrators", you don't need coils of wire at all. And if you're willing to use DSP, the sky's the limit, as far as tweaking filter parameters.

3. PA amplifiers, of the kind designed to drive "70 volt line", with multiple crappy little in-wall speakers each with its own step-down transformer, should not be confused with the type used to play large rooms and theaters (where highly regarded "audiophile" brands like McIntosh are often to be found). Nor should it be confused with an electric guitar, amp and speaker, which is a musical instrument unto itself.

When one of the first commercial actively crossed over speaker systems came out, the Infinity Servo-Static, the Crown DC 300 was frequently recommended to drive the power hungry mid-range. Since that time, Crown has drifted more into the pro market. In my time in broadcasting I saw many D-75's and D-150's used to drive studio and control room monitors. Doesn't mean they started to sound worse than before. I don't believe for one instant that all competently designed amplifiers not driven into distortion sound the same, but I do believe they sound more the same than they did, say, 30 years ago. Thanks in part to better components, true complimentary power transistors (in the case of SS), better output transformers (in the case of hollow state) and better construction and manufacturing techniques.

No matter how much you may love the "magical liquid mid-range" Stereophile and TAS reviewers may rave about a $30,000 or $300,000 amplifier, it's pretty much irrelevant driving a woofer up to 300hz. I wouldn't hesitate to use a class D amp for that application. And you have to ask yourself in any case at what point the law of diminishing returns kicks in.

 

[Robert D]

Empirically, we have many knowledgeable members on here running crown amps with crossovers on their speaker woofers and reporting remarkable improvement in sound. That's good enough for me as proof.
I'm glad I wondered onto this site because there are some knowledgabke folks here! Saves me time having to search the web for answers.

 

[Asepguy]

I'm reluctant to jump into this food fight, but I will. I won't shout "FACTS" in all caps, but the following is pretty much beyond reasonable dispute:

1. In engineering, almost everything involves trade-offs, in cost, various desired performance parameters, or both.

2. It's pretty much been acknowledged since almost the beginning of time that active crossovers offer performance advantages over passive ones--both theoretical and actual audible differences. Probably mostly in the former category today is the fact that two or more amps being driven with bandwith-limited signals will produce fewer intermodulation products, all other things being equal. More practical, perhaps, is that passive crossovers require large component values at the impedance speakers operate at. This usually necessitates bipolar electrolytic capacitors which, among other things, have crappy unit to unit consistency, and sometimes even iron core inductors, which are subject to hysterisis nonlinearities. Connecting each driver directly to a separate amplifier enables greater control of the speaker by the amp, especially important for dynamic woofers. Finally, active crossovers offer finer control over the crossover parameters. Even in the analog domain, 24dB/octave is no problem. You can have Butterworth, Linkowitz-Reilly, anything your heart desires. Thanks to elegant circuits like "negative inductors" and "gyrators", you don't need coils of wire at all. And if you're willing to use DSP, the sky's the limit, as far as tweaking filter parameters.

3. PA amplifiers, of the kind designed to drive "70 volt line", with multiple crappy little in-wall speakers each with its own step-down transformer, should not be confused with the type used to play large rooms and theaters (where highly regarded "audiophile" brands like McIntosh are often to be found). Nor should it be confused with an electric guitar, amp and speaker, which is a musical instrument unto itself.

When one of the first commercial actively crossed over speaker systems came out, the Infinity Servo-Static, the Crown DC 300 was frequently recommended to drive the power hungry mid-range. Since that time, Crown has drifted more into the pro market. In my time in broadcasting I saw many D-75's and D-150's used to drive studio and control room monitors. Doesn't mean they started to sound worse than before. I don't believe for one instant that all competently designed amplifiers not driven into distortion sound the same, but I do believe they sound more the same than they did, say, 30 years ago. Thanks in part to better components, true complimentary power transistors (in the case of SS), better output transformers (in the case of hollow state) and better construction and manufacturing techniques.

No matter how much you may love the "magical liquid mid-range" Stereophile and TAS reviewers may rave about a $30,000 or $300,000 amplifier, it's pretty much irrelevant driving a woofer up to 300hz. I wouldn't hesitate to use a class D amp for that application. And you have to ask yourself in any case at what point the law of diminishing returns kicks in.

Thanks for adding your thoughts, it took more than a few keystrokes to put all that down in writing! I agree with the tradeoff statement (I'm an engineer ). I don't dispute that all other things being equal an active crossover would be the better choice - but when you are modding a speaker design - you are now the product designer and must figure out how to match everything - not sure it's worth that kind of risk/trouble for me personally.
3. I'm not confusing any of the product applications you mentioned. The amps being promoted for this mod are PA amps designed for throwing sound long distances in concert venues. I'm not concerned about the other applications.
In terms of cost and diminishing returns - That's kind of a big part of my point. For those end users who ALREADY invested in the high end gear, switching to a PA amp of a few hundred bucks is a downgrade. Regardless of the crossover improvement. The user purchased the amp to be capable of driving the full range of the speaker. By removing the low frequency load from the amp, you are basically throwing half of it's use in the dumpster, and paying to do so. If you ALREADY made that investment - why would you do ever want to take that course of action?

 

[Asepguy]

Empirically, we have many knowledgeable members on here running crown amps with crossovers on their speaker woofers and reporting remarkable improvement in sound. That's good enough for me as proof.
I'm glad I wondered onto this site because there are some knowledgabke folks here! Saves me time having to search the web for answers.

That's a fine way to look at things. To each their own, live and be happy! I'm not of the same mindset. That's not to say the folks here are not every bit as knowledgeable as you say. It's just how my brain is wired. I've spent a career working with people who are "professionals" in their trade - meaning they get paid and earn a living to support themselves/families performing a type of work, but they are not even close to understanding their trade or performing it properly. You can be "good enough" at something to make it work/get by and even make a living at it, but that doesn't mean it's correct or as good as it gets. Anyone, in any role who believes they have it all figured out and they have no room for growth and accuse others of being 100% wrong has a serious case of the Dunning-Kruger effect!

 

[DanR]

Wow what an excellent response Leporello, and it helps answer a question that has bothered me for more than 15 years. I have nowhere near the education and understanding of electronics and theory as you do and never will. But what has bothered me for more than 15 years is why on the pair of Ascent i speakers that I bought new so many years ago could I never get the bass to integrate with the panels to my liking. I loved everything about those speakers except that and that’s why I ended up selling them. Now all these years later I came back on here and started reading on the active crossover topic and said you know what that’s worth a shot. So I bought the Odysseys and new panels and took the plunge. And as soon as I fired them up the first time with the passive bass crossovers out of the picture and was actively crossing them over. Bingo!!!! The bass was integrating with the panel so much better and the speakers sound absolutely wonderful. So I may not understand the theory and how all the electrons flow but I do understand this. My speakers now have the sound that I have been searching for, for a long long time. A big thank you to Jonfo your post was the one that got me started down this path.