Matchless Chieftan - WTH

[bob p]

are those Matchless combos open-back or closed-back? nobody ever shows the back side of a Matchless, Matchless doesn't say on their website, and I've never seen one in person.

their site does refer to the preferred pairing as a G12H30 with a Greenback with some "proprietary treatment" which if I had to guess is nothing more than de-doping the surrounds.

[Enzo]

When one of our stored we serviced for carried the Matchless, I was told they took the new speakers and pounded on the magnets with a mallet to reduce the magnetic charge in them.

[bob p]

When one of our stored we serviced for carried the Matchless, I was told they took the new speakers and pounded on the magnets with a mallet to reduce the magnetic charge in them.

[ATTACH=CONFIG]45300[/ATTACH]

Mallets?!? WTF?!?

(there's a "WTF" just for you, rjb. )

[g1]

When one of our stored we serviced for carried the Matchless, I was told they took the new speakers and pounded on the magnets with a mallet to reduce the magnetic charge in them.

Something I've meant to ask Juan about, but keep forgetting.
Why don't we just partially degauss speakers rather than using power attenuators? Something about the sound must fall apart if the gauss level goes too low?
How does Eminence modulate the flux density in their FDM speakers?

[J M Fahey]

Something I've meant to ask Juan about, but keep forgetting.
Why don't we just partially degauss speakers rather than using power attenuators? Something about the sound must fall apart if the gauss level goes too low?
How does Eminence modulate the flux density in their FDM speakers?

Notice some tried and it didnīt catch on.
2 problems:

1) degaussing definitely lowers sensitivity, no doubt about that, but not smoothly across the range.
Same as installing a corolla engine in a fully loaded 18 wheeler truck, you will lower maximum speed but you will *murder* acceleration.

The speaker becomes "slow" (literally), muddy, loses treble, bite, attack.
Also loses damping so you get a boomy "single note peak" at resonance, because it becomes underdamped.
Which in brochure language is described as "smooth" , "warm" , etc.
It definitely is not "the same sound but at lower levels" by any means.

2) power handling decreases dramatically.
If you think about it, voice coil handling is puny, just a small 2 layer coil of fine wire (typically around 0.16 to 0.22mm) wound on a poorly conductive thin sheet plastic or paper bobbin.
Easy to burn with a few Watts if laying static on a table ... or inside an unmagnetized speaker.

Yet Voice coils live standing tens or over 100W because they shake violently all the time, air around them is turbulent (and thatīs an understatement) , VC is 0.1mm to 0.2mm away from a massive (1 to 8 kilos magnetic structure)
FANE measured the turbulent air conductivity and found it "close to silver" , go figure.

So you have a speaker which stands, say, 60W continuous, any waveform including squarewave, you drive it with a 30W RMS amplifier which can give you some 50W RMS squarewave fully overdriven (not the exact double because power supply drops something) ... so far so good.

Now you attenuate it by 10 dB ... and you drive your amp balls to the ball (thatīs the point) ... still 50W RMS squarewave, besides sustain and feedback make your notes, specially power chords last longer ... but speaker voice coil now stands, say, 30W RMS because ventilation is poorer; by definition an accident waiting to happen.

Worst is that attenuation range isnīt that much, will never turn a Club/garage amp into a bedroom one.

I find conceptually better to add a resistive attenuator and let a big, robust (and inexpensive) resistor take the onslaught.

Sound will also change, in fact it will probably appear harsher (Fletcher Munson), but in any case thatīs easier to handle.

Never opened one, but I guess the Eminence speaker adds some variable gap or separates 2 steel pieces or adds a steel ring "bypass" , something to lose magnetic density **at the VC gap** ; the ceramic magnet is a "strong/square" material and canīt be altered itself .

Personally find "best" the variable +V system, which leaves everything exactly the same, just makes amp less powerful.
And second best the Ultimate Attenuator, which passively loads and reamps but in the least intrusive way.

[The Dude]

..... and, to top it off, that square wave you mentioned is holding the speaker at full excursion and incursion for longer periods of time than a sine wave would, so there is even more heat generated and less time for cooling.

[J M Fahey]

Yes, squarewaves are destructive.

To boot, clipping SS amp waves are almost perfect squarewaves (Music Man amps too), while regular tube amp ones, not that much.

A 100W SS amp makes speakers suffer more than a 100W tube one, because clipped waveforms are different, even if averaged power is the same.

Now, on a resistor load, that makes not difference.

[pdf64]

Notice some tried and it didnīt catch on.
2 problems:

1) degaussing definitely lowers sensitivity, no doubt about that, but not smoothly across the range.
Same as installing a corolla engine in a fully loaded 18 wheeler truck, you will lower maximum speed but you will *murder* acceleration.

The speaker becomes "slow" (literally), muddy, loses treble, bite, attack.
Also loses damping so you get a boomy "single note peak" at resonance, because it becomes underdamped.
Which in brochure language is described as "smooth" , "warm" , etc.
It definitely is not "the same sound but at lower levels" by any means....

Dunno how it's done but my FluxTone (field coil attenuation system) seems to keep the same tone over its range of control, which is wide (think they claim 35dB).
When measuring the bass resonance impedance peak, it becomes less and less as the field coil voltage is turned down, but it doesn't seem to affect the tone.

[g1]

Dunno how it's done but my FluxTone (field coil attenuation system) seems to keep the same tone over its range of control, which is wide (think they claim 35dB).
When measuring the bass resonance impedance peak, it becomes less and less as the field coil voltage is turned down, but it doesn't seem to affect the tone.

Yes, I was wondering about that one, also the Eminence FDM (flux density modulation) like the Reignmaker.
edit: sorry, I missed JM's comments on the eminence which seem the best explanation short of an autopsy.

[Enzo]

One could probably contact Eminence and ask them what the basic process is.

I contacted them once with a nerdly question about the magnetization process and machinery, nothing to do with using their product, and I got a very nice explanatory response from them.

[J M Fahey]

Well, itīs probably patented, or there would be a dozen copycats by now.
So somebody skould search for it, where they spill the beans, by definition.
At least the basic working principle.

[Enzo]

Oh just the basic principle. Anyone who wants to steal the idea needs to merely buy one and take it apart.

[J M Fahey]

Found more than I bargained for, a VERY detailed and advanced analysis at: Test Bench: Eminence Maverick Guitar Speaker

just as a notable point, this table shows *real* sensitivity, by the way a lot less than what Eminence claims (I routinely substract 3 dB from their SPL "number") but the main point is attenuation is *very* small, a meager 8dB or so.

Might do to fine tune an amp to a drummer, but definitely not enough for bedroom or quiet practice:


the 3 relevant lines for us are:

* SPL: from 95.4 to 87.9 dB , some 8dB ... very little to justify the expense and complication.

* BL from 8.4 to 3.6 <--- this is the main magnetic variation parameter, B is (variable) flux density. L is voice coil wire length which of course does not change .

* Qts , speaker Q at resonance, it shoots through the roof, from 0.99 to 3.90 , a whopping 4:1 ratio, as I predicted (without seeing this but making own design speakers for 40 years), speaker becomes poorly damped and controlled, bass becomes boomy.
*

[bob p]

Like Juan, I prefer a resistive attenuator. I never thought it was worth the effort to degauss speakers. I prefer EV speakers with their ginormous 4# 13 oz magnets because those big manly magnets will do things that little girlie magnets just won't do.

[Chuck H]

JMHE...

I've built resistive attenuators into some of my amps, but my personal attenuator uses the load design from the Randall Aiken article:

Designing a Reactive Speaker Load Emulator

instead of a resistor. Now, my design uses a rheostat as a sort of parallel valve to tell the amp which load (speaker or other) to play into. So in that regard it's partly resistive all the time. Using my active load attenuator side by side with the purely resistive units I'd have to say that the reactive element in my design sounds better. Especially at low settings. Since tone is subjective, of course, YMMV.