Blue Shadow
Waiting for Vintage Gear from this century
No wonder multi-amping and eliminating the speaker crossover can make the sound much better.
Can anyone help with Magnepan 3.5r external crossover build?
- Thread starter Brandosees
- Start date
MuseChaser
Super Member
The Maggie XO in question has an 8.5mH inductor in the mid/tweet filter, and 5.6mH and 1.7mH inductors, all drawn as solid core, in their schematics. The designers, without doubt, took the DCRs into account when designing the circuits, and large changes in those values will result in different filter behavior. The 8.5mH inductor in particular is more than large enough where the cost/quality/ergonomic benefits of a quality solid core outweigh by a large margin those of an air core in this instance. @R Swerdlow covered all of this beautifully in post #8 of this thread.
This would be mostly correct if "louder" equated with "better," but it doesn't....it just means louder. The Maggie 3.5 in question is a beautiful, well-balanced speaker as designed, perhaps lacking only in extreme significant low bass output below 30Hz (a guess..they may have some energy a bit lower). In this instance, of course, if one insisted on substituting in air core inductors, it does mean that you'd need to make sure the DCRs were comparable to the existing solid core inductors or you would, indeed, suffer reduced output from the connected drivers among other things, mesing up the overall system's frequeny response curve.
Try the same experiment with A/C at the level present in speaker level signals.
This has nothing to do with the original poster's goal; to recreate Magnepan's original crossover with better components. Active crossovers and bi- or tri-amping certainly have their benefits, but they have nothing to do with eliminating bad things induced by well-designed passive crossovers.
1. They give a one a ton more flexibility, so you don't have to "get it right the first time" like you do with a passive xo build.
2. They present easier loads on the amplifiers as they are only required to amplify specific frequency bands.
3. Amps can be chosen that excel for each purpose..high current amps for the bass drivers, etc.
Drawbacks?
1. Expense.
2. Huge increase in length of signal path.
3. Complexity/number of failure points.
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NeilBEN
Well-Known Member
If the active crossover is digital, that certainly introduces its own set of issues. I use a miniDSP 2x4 HD to design a crossover - trying out any number of combinations is just a click or two away.
A louder woofer means that you don't have to tamp down the midrange and the treble as much - your speaker has (slightly) higher sensitivity, and requires less from your amp. This also means that it will possibly sound more dynamic; because it can respond in a better proportion to the signal. So, it is certainly not just about just being louder.
The magnetic eddy currents occur proportional to the voltage, and the higher the frequency, the more of an issue *any* time lag is. And the amp will "see" the voltages generated by the magnetic eddy currents.
A coil generates a magnetic field when there is a voltage in the conductor - and the magnetic field generates a voltage in the coil. This is how an inductor functions, as I'm sure you know. So, having a lingering magnetic field that is delayed in relation to the input signal - means that additive distortion and phase shifting is occurring. Bass is generally a higher voltage, and therefore those will have a stronger magnetic eddy current that lasts longer. Treble has a bigger challenge - even though the voltages are generally lower, the higher frequencies make it more susceptible to smearing.
Whens the last time you saw an metal core coil on a tweeter? The same effects are present in all metal core coils. If you want better sound quality, then using air core coils is key.
Yes, this is more costly - more windings are required, and then to keep the DCR lower, the windings need to be larger gauge. Again, the woofer is usually the limiting factor, so on the midrange and the tweeter, the coil gauge can be smaller - and you then can use slightly smaller value resistors. This lowers the inductance of those parts, and so the treble can be less affected.
The bass quality improvement with an air core coil is something you have to hear to appreciate. After spending thousands on a speaker, ten or twenty or fifty more on a better coil seems pretty reasonable to me. As was mentioned, a coil doesn't age, so as long as that speaker lasts - it will sound significantly better that whole time.
A louder woofer means that you don't have to tamp down the midrange and the treble as much - your speaker has (slightly) higher sensitivity, and requires less from your amp. This also means that it will possibly sound more dynamic; because it can respond in a better proportion to the signal. So, it is certainly not just about just being louder.
The magnetic eddy currents occur proportional to the voltage, and the higher the frequency, the more of an issue *any* time lag is. And the amp will "see" the voltages generated by the magnetic eddy currents.
A coil generates a magnetic field when there is a voltage in the conductor - and the magnetic field generates a voltage in the coil. This is how an inductor functions, as I'm sure you know. So, having a lingering magnetic field that is delayed in relation to the input signal - means that additive distortion and phase shifting is occurring. Bass is generally a higher voltage, and therefore those will have a stronger magnetic eddy current that lasts longer. Treble has a bigger challenge - even though the voltages are generally lower, the higher frequencies make it more susceptible to smearing.
Whens the last time you saw an metal core coil on a tweeter? The same effects are present in all metal core coils. If you want better sound quality, then using air core coils is key.
Yes, this is more costly - more windings are required, and then to keep the DCR lower, the windings need to be larger gauge. Again, the woofer is usually the limiting factor, so on the midrange and the tweeter, the coil gauge can be smaller - and you then can use slightly smaller value resistors. This lowers the inductance of those parts, and so the treble can be less affected.
The bass quality improvement with an air core coil is something you have to hear to appreciate. After spending thousands on a speaker, ten or twenty or fifty more on a better coil seems pretty reasonable to me. As was mentioned, a coil doesn't age, so as long as that speaker lasts - it will sound significantly better that whole time.
MuseChaser
Super Member
I tried. @Brandosees , still just trying to help. Choose wisely, and best wishes.
NeilBEN, you're ignoring a couple key things, already stated. I'll try one more time, more succinctly, and then just let it go.
1. The orignal poster wants to build the Maggie xo with better components, not redesign it.
2. Changing the efficiency/sensitivity/performance of one part of the filter, as would happen with a large change in DCR, would require changes in the rest of the XO, requiring a redesign.
3. You keep recommending a low DCR for louder bass, thereby lessening the requirement for "tamping down" the mid and high drivers. Yet, you recommend air core inductors for the large value inductors which makes achieving that goal expensive for very small potential gain... MUCH more than the additional $50 you assert. More like a couple hundred, and an additional ten or more pounds of wire.
4. Air coils are used on tweeters for all kinds of reasons. At those values, they're relatively inexpensive, they DO have the benefits you mention, and DCR isn't a problem because often times a bit of attenuation of the high frequency driver is necessary to get a good system-wide frequency response. Those reasons don't translate to chosing air coils for large values and for low pass filters, and they DEFINITELY don't translate when replacing existing components in a given design unless inductance and DCR specs match, space and weight aren't issues, and money isn't part of the equation.
Here's a low DCR (0.54 ohms) 8.2mH air coil I found, if this is really something anyone would want to do. It weighs almost 8 pounds, and costs over $150, but it's values seem pretty close, although I don't know the DCR of the original Maggie coil. I am NOT recommending this... just throwing out options.
https://solen.ca/products/inductors...r-core-inductors-s128_2-8_2mh-12awg-inductor/
NeilBEN, you're ignoring a couple key things, already stated. I'll try one more time, more succinctly, and then just let it go.
1. The orignal poster wants to build the Maggie xo with better components, not redesign it.
2. Changing the efficiency/sensitivity/performance of one part of the filter, as would happen with a large change in DCR, would require changes in the rest of the XO, requiring a redesign.
3. You keep recommending a low DCR for louder bass, thereby lessening the requirement for "tamping down" the mid and high drivers. Yet, you recommend air core inductors for the large value inductors which makes achieving that goal expensive for very small potential gain... MUCH more than the additional $50 you assert. More like a couple hundred, and an additional ten or more pounds of wire.
4. Air coils are used on tweeters for all kinds of reasons. At those values, they're relatively inexpensive, they DO have the benefits you mention, and DCR isn't a problem because often times a bit of attenuation of the high frequency driver is necessary to get a good system-wide frequency response. Those reasons don't translate to chosing air coils for large values and for low pass filters, and they DEFINITELY don't translate when replacing existing components in a given design unless inductance and DCR specs match, space and weight aren't issues, and money isn't part of the equation.
Here's a low DCR (0.54 ohms) 8.2mH air coil I found, if this is really something anyone would want to do. It weighs almost 8 pounds, and costs over $150, but it's values seem pretty close, although I don't know the DCR of the original Maggie coil. I am NOT recommending this... just throwing out options.
https://solen.ca/products/inductors...r-core-inductors-s128_2-8_2mh-12awg-inductor/
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Blue Shadow
Waiting for Vintage Gear from this century
And with many speakers, maybe most that aren't from top end manufacturers this will probably yield good results. Magnepan is known to built speakers to a price point and improvements in the crossover can make them sound a good bit better. They wanted folks to be able to afford their speakers not just see them in the showroom and not consider them for purchase.
MuseChaser
Super Member
Price points are always a consideration for manufacturers, agreed. The folks at Magnepan are very nice to deal with.. I've spoken on the phone with their sales folks, and the folks that actually build and do the factory repairs and refurbishment of the speakers on a few occasions. They, above all, would know what would constitute an improvement to the crossover they designed, and may very well be willing to offer advice; if they held back on certain things to hit a price point, they may be willing to tell the OP what they would have done differently component wise without those constraints. At this point, that may be the best course of action for the OP.
There was a change I wanted to make to one of the smaller pairs of Maggies I own, so I called them maybe six months ago. The tech was great... enjoyed talking to him, very personable, and VERY knowledgeable. He explained why what I wanted to do wasn't a great idea and he didn't recommend it, but still explained what I'd need to do if I wanted to do it anyway. I love my Maggies, I respect the folks at Magnepan... so I didn't do it.
Blue Shadow
Waiting for Vintage Gear from this century
Yes, good people.
I mentioned the Peter Gunn upgrades and a big part of what he did was the crossover change. Some of those parts were high dollar caps and folks seem to talk very positively about the improvement. Magnepan knows they cannot more than double the price of their speakers just to use crossover components only 10% of the buyers would appreciate.
True, but as someone already pointed out, the negative effect of iron cores may not be audible, and the sheer size of some air core inductors may present location issues and might limit the ability to place them at right angles to other inductors, and that might be just as audible.
The expense is another issue, but apparently not one the OP is too concerned about.
The expense is another issue, but apparently not one the OP is too concerned about.
Blue Shadow
Waiting for Vintage Gear from this century
Last Aug someone posted a pair of 3.6 with Peter Gunn crossovers on CAM. Worth a look to see the quality parts used in that one.These were owner built but with John's input on what to use. Easy to tell as they appear to be built into humidors. John being a self taught joiner he made quality boxes for these external crossovers.
Not an active ad so I'll link it so folks can look over the crossover.
https://www.canuckaudiomart.com/det...magneplanar-36r-custom-peter-gunn-crossovers/
Not an active ad so I'll link it so folks can look over the crossover.
https://www.canuckaudiomart.com/det...magneplanar-36r-custom-peter-gunn-crossovers/
MuseChaser
Super Member
One thing to be aware of is that components frequently do not measure accurately in place in the circuit. It may be worth lifting/unsoldering one leg of the capacitor(s) you are measuring to verify your measurements. I hope you're doing well and feeling better.