The MLP ATTENUATION PROJECT !!!

GrouchyDog

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The best volume reduction device for a tube amp that I've seen is a Fluxtone speaker (Google is your friend). The Fluxtone essentially replaces the stock magnet assembly on the back of your favorite speaker (say, a Vintage 30) with a variable electromagnet. This doesn't intrude on the whole output transformer <-> voice coil loop at all, and the distinctive sound of the speaker, which comes from the moving parts (not the magnet) is unaffected.
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I think this looks really cool. Although I can't imagine it'd fit in many combo amps - it's pretty deep.

Does the magnet really NOT affect the tone? That's one of the core components and I have a bit of trouble (based on no real hard knowledge) believing that. If true, why would so many folks willingly pay up to a couple hundred more per driver for Alnico magnets and rave about the tone? :hmm:
 

Soul Tramp

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I think this looks really cool. Although I can't imagine it'd fit in many combo amps - it's pretty deep.

Does the magnet really NOT affect the tone? That's one of the core components and I have a bit of trouble (based on no real hard knowledge) believing that. If true, why would so many folks willingly pay up to a couple hundred more per driver for Alnico magnets and rave about the tone? :hmm:


I have my doubts about this approach. Just in the few amps I work with I use about five different speakers. Each speaker has it's own unique voicing. Some are ceramic and others alnico. Each has a different cone design, different VC, and different size magnet. One speaker will not produce all the different tones I require.
 

LPV

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I have my doubts about this approach. Just in the few amps I work with I use about five different speakers. Each speaker has it's own unique voicing. Some are ceramic and others alnico. Each has a different cone design, different VC, and different size magnet. One speaker will not produce all the different tones I require.

Definitely the least flexible approach.
 

Titi1506

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Even if this approach has great results, you have to buy 1 to 4 speakers per cabinet&#8230;

Imagine that you have 2 half stacks, 1 2x12 and several combos&#8230; It's gonna be really expensive!

And they seem to sell speakers with the system integrated but no stand alone kit&#8230; I like my Scumbacks a lot!
 

Soul Tramp

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LPV, I love "Blues Litigator" moniker. It fits the picture perfectly. It just works!!
 

dspelman

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I have my doubts about this approach. Just in the few amps I work with I use about five different speakers. Each speaker has it's own unique voicing. Some are ceramic and others alnico. Each has a different cone design, different VC, and different size magnet. One speaker will not produce all the different tones I require.

According to Fluxtone, the magnet material doesn't affect the tone. Other speaker components do, of course -- and this includes the cone material, the voice coil diameter, etc. In short, all the moving parts.

Essentially, Fluxtone replaces the existing magnet with a variable electromagnet and leaves the rest of the speaker alone. If you hear one of these in person, you will hear (for example) the distinctive sound of a Vintage 30. If you break it in, you'll get the same characteristics as a broken-in Vintage 30. If it's another speaker design, you'll hear that one.

If you're not able to get your "tone" with one speaker, you'd have to buy more than one (and they're pricey), so these won't work for you unless you have the bucks to support that.
 

dspelman

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I think this looks really cool. Although I can't imagine it'd fit in many combo amps - it's pretty deep.

Does the magnet really NOT affect the tone? That's one of the core components and I have a bit of trouble (based on no real hard knowledge) believing that. If true, why would so many folks willingly pay up to a couple hundred more per driver for Alnico magnets and rave about the tone? :hmm:

If you'd checked the website, you'd have already seen that the illustrated speaker is not the only one they've done, and that the magnet looks different (and has different dimensions) on different speakers. You can ask them about specific speakers in specific boxes and you'll probably get a lot more concrete information than through idle speculation.

There's a lot of elven mythology about speaker magnets. There's actually a lot of completely whacked-out misinformation out there about speaker magnets, and there are "so many folks" willing to make generalizations about them based on absolutely no real hard knowledge. "Neo magnets always sound shrill and fizzy to me" "I really like the warmth of an Alnico V magnet." "Ceramic magnets sound harsh..." and so on.
 

Soul Tramp

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Below is an excellent white paper on alnico vs. ceramic magnets. The one critical point for us guitar players is not addressed, and that is compression. It's ignore in the write up below because audio speakers systems are designed NOT to compress.

Ceramic speakers do not have the smooth compression of alnico speaker. This can be good or bad, depending upon the voicing of the amp.

And Don McRitchie is just about the final word on the subject!



The subject of Alnico vs ferrite magnet drivers comes up fairly regularly on our site. The following is my attempt to clarify some of the issues involved. Before I get into a discussion on the merits and disadvantages of each magnet type, it is important to separate fact from fiction. To understand how this debate began, it is necessary to know a bit about loudspeaker history. Up until the late 70’s, most high end speaker manufactures used Alnico magnets due to their greater energy/weight ratio. Starting in 1978, all major manufactures (JBL, EV, Altec, Tannoy etc.) switched to ferrite drivers. That was when the myths began.

Myth #1 – Speaker manufactures switched to ferrite as a way to lower their production costs and cheapen the quality of their drivers.

Fact – The switch to ferrite was in response to a crisis situation whereby Alnico became totally unavailable. A civil war in Zaire led to the complete embargo of the world’s only source of commercial cobalt used in Alnico. There was no choice but to switch. This is why, in less than one year, every major Alnico speaker manufacturer had switched to ferrite.

Myth #2 – Due to the lower energy/weight ratio of ferrite, drivers using this material have lower total flux and lower flux densities compared to the previous Alnico drivers.

Fact – The initial ferrite conversion had the exact same magnetic energy of Alnico drivers they replaced. For JBL, the initial conversion effort focused on bass drivers since that represented their largest consumption of magnets. They had sufficient magnet stock on hand to continue Alnico compression drivers for a number of months.

To be able to continue production of the speaker systems in their catalogs, the ferrite bass drivers had to be the exact sonic equivalents of the Alnico drivers they replaced. Otherwise, the entire systems would have to be re-engineered and there was no time to do this. To give you an example, the L300 Summit, both before and after the ferrite bass driver conversion, used the exact same Alnico tweeter, Alnico compression driver, enclosure and network. The only change was that the 136A driver had its Alnico motor replaced with a ferrite motor to become the 136H. The basket, cone and suspension remained identical. The only way this could work was if the ferrite motor had the exact same magnetic energy as the Alnico motor.

As the demand for high power drivers increased, the magnetic energy of the ferrite drivers began to exceed the former Alnico systems. As an example, the last ferrite version of the Altec 515 had a flux density of 15kgauss compared to the 14kgauss of the Alnico version. The Alnico embargo proved short lived. Alnico became available in limited quantities after a year or so, but at a much higher cost. This happened before the compression drivers were converted and it was decided to continue their production to save the costs of redesign. Therefore, Alnico HF drivers remained in production for another three or four years, until it became too cost prohibitive to continue. Around 1983, they were converted to ferrite motors as well.

Nonetheless, the costs of the ferrite replacements in constant dollars remained about the same as the Alnico drivers before the civil war broke out in Zaire. Any savings in cheaper magnetic materials were outweighed by the sheer size of the magnets and the need for a large pole piece to accommodate the external magnet topology.

Now to factual differences. There are three main advantages of Alnico over ferrite:

1) greater immunity to flux modulation

2) greater heat stability.

3) greater suitability to shielded applications

There is also one significant disadvantage – Alnico is susceptible to demagnetization due to large voice coil currents.

None of these differences are absolute. It is possible to design out all of the limitations of each material. However the issue becomes one of cost.

Ferrite designs can equal or exceed an Alnico magnet’s flux stability with the addition of a copper shorting ring around the pole piece. With the use of vented cooling and heat sinking, you can manage the heat build-up on a ferrite driver to where it stays below the threshold of non-linear response. Finally with the addition of secondary magnets, you can shield the motor of a ferrite driver to the same degree as an internal ferrite equivalent.

In the same manner, Alnico drivers can be engineered to be immune to demagnetization from overpowering. JBL has done this though the use of a series of flux stabilization rings in their new 1500AL driver. However it is extremely expensive.

All in all, the major speaker manufacturers have found it more cost effective to engineer out the limitations of ferrite drivers than to do so with Alnico drivers and hence the dominance of ferrite designs.

In conclusion, I believe the modern ferrite drivers are superior to the vintage Alnico designs. This is not because ferrite is inherently superior to Alnico. Instead, manufacturers have been able to engineer out any limitations of ferrite and apply the advantages of 25 years of technological progress in driver designs unrelated to magnets. For example, cone materials, suspension design and construction has progressed significantly since the last Alnico drivers were made.

Don McRitchie - Lansing Heritage Forum


 

dspelman

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Definitely the least flexible approach.

Sort of yes, sort of no.

No (lemme repeat that...NO) attenuator in any of the lists above allows the interaction between output transformer and speaker voice coil to happen unobstructed. No attenuator in any of the lists above maintains the tone of the amp/speaker combination; they all change things. If you LIKE what they do, you're in good shape. If you don't, then you're off and running trying various attenuators and various EQ setups to try to adjust things to get back to what you like. And the amount of tone change varies according to the amount of attenuation necessary, so you're constantly chasing EQ.

The Fluxtone is the only system that puts nothing between the output transformer and the voice coil of the speaker.

The first time I heard the fluxtone was at the LA Amp Show several years ago. They had two cabinets set up, one with a standard speaker, the other with the same speaker, but with the Fluxtone setup on the back. They switched back and forth for a bit, and it was obvious that the two speakers sounded identical. They cranked things up (it gets LOUD in those airport hotel rooms, but the additional sound proofing in each room necessary to allow people to sleep under an airport flight path is why the amp show is held there). And then the fluxtone rep began to dial the thing down.

The tone stayed the same, but things eventually got to the point where you could hear the sound of jaws bouncing off the carpet and the occasional "no WAY!" It's 25 dB of difference (roughly the equivalent of taking your 100W amp down to 1/2W).

The ONLY real problem with this approach is its expense. It's prohibitive to put a quartet of these speakers in a 4x12 or a 2x12, no question. But if you're recording or practicing, or even doing a gig where stage volume is a serious issue, why would you be working with those larger speaker cabinets anyway? I have, for example, one of the loudest four EL34 amps I've ever heard. It's a 1x12 combo that usually houses an EV and between the bigass Mercury Magnetics transformers and the magnet on the back of that EV, it's insanely heavy for a combo. It's run pairs of 4x12s to ear-melting levels for gigs, but it's crazy loud just on the efficient internal speaker as well. I tried it, cranked, with a Fluxtone speaker based on the EV in an open-backed cabinet. Then dialed it down as far as it would go. Fletcher-Munson aside, there was all the good stuff but at a volume that would allow a muted conversation. We put it in a room and put a mike on it (try this with your attenuators) loud, dialed down, and then on the internal combo speaker. The obvious differences were between the Fluxtone and the internal speaker (this speaker was the original from 1988), but between the cranked Fluxtone and the dialed-back Fluxtone, very little, approaching nothing. Try that with an attenuator and see what you get.
 

dspelman

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The one critical point for us guitar players is not addressed, and that is compression. It's ignore in the write up below because audio speakers systems are designed NOT to compress.

Ceramic speakers do not have the smooth compression of alnico speaker. This can be good or bad, depending upon the voicing of the amp.

Unfortunately, the assertion regarding compression differences between magnet types is NOT backed up by anything in the white paper information, as you note. It's also worth noting that in any system using attenuators to reduce power, speaker compression is not an issue. Attenuation is about attaining power tube saturation, but NOT transmitting that accompanying power level to the speaker.

We're currently going through some of the same supply-side problems with neodymium-based speaker magnets; Chinese supplies are being closely regulated to keep costs high. There's plenty of neodymium available here in the US, but when it was cheaper to buy from China, US refining simply shut down. At this point, there's a bit of gamesmanship taking place as China tries to keep the US from refining its own by tight-roping the price very close to the critical point. At the moment, however defense contractors seem to have pushed hard enough for US refining to ramp up, and we should see prices drop again.

Neo-speakered magnets are also the subject of some guitar-player mythology regarding tone. Simply slapping a different magnet on the back of a speaker will produce differences (as noted in the information you supplied), but engineering the magnet structure makes for a different result. Outside the confines of guitar players and their "everything's got to be a 12" speaker with a mid-hump" realm, neodymium-based speakers have become the go-to for high power long-excursion systems that need to produce flat, smooth response at insane power and volume levels in tightly controlled/designed speaker cabinets.
 

Soul Tramp

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Unfortunately, your assertion regarding compression is NOT backed up by anything in the white paper information.


Exactly. Hifi speakers systems are design to eliminate compression and any other form of coloration. However, many guitar speaker systems are designed to incorporate and leverage compression.

There are countless drivers that are available with either an alnico or ceramic magnet (hifi and guitar). All you have to do is listen to them to hear the difference. In most of the test I've done the ceramics get hissy when they compress, where as the alnico retains articulation (for the most part) and sounds smoother. When not over-driven, all other things being equal, I can't hear a difference.
 

homenote

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Sort of yes, sort of no.

No (lemme repeat that...NO) attenuator in any of the lists above allows the interaction between output transformer and speaker voice coil to happen unobstructed. No attenuator in any of the lists above maintains the tone of the amp/speaker combination; they all change things. If you LIKE what they do, you're in good shape. If you don't, then you're off and running trying various attenuators and various EQ setups to try to adjust things to get back to what you like. And the amount of tone change varies according to the amount of attenuation necessary, so you're constantly chasing EQ.

The Fluxtone is the only system that puts nothing between the output transformer and the voice coil of the speaker.

The first time I heard the fluxtone was at the LA Amp Show several years ago. They had two cabinets set up, one with a standard speaker, the other with the same speaker, but with the Fluxtone setup on the back. They switched back and forth for a bit, and it was obvious that the two speakers sounded identical. They cranked things up (it gets LOUD in those airport hotel rooms, but the additional sound proofing in each room necessary to allow people to sleep under an airport flight path is why the amp show is held there). And then the fluxtone rep began to dial the thing down.

The tone stayed the same, but things eventually got to the point where you could hear the sound of jaws bouncing off the carpet and the occasional "no WAY!" It's 25 dB of difference (roughly the equivalent of taking your 100W amp down to 1/2W).

The ONLY real problem with this approach is its expense. It's prohibitive to put a quartet of these speakers in a 4x12 or a 2x12, no question. But if you're recording or practicing, or even doing a gig where stage volume is a serious issue, why would you be working with those larger speaker cabinets anyway? I have, for example, one of the loudest four EL34 amps I've ever heard. It's a 1x12 combo that usually houses an EV and between the bigass Mercury Magnetics transformers and the magnet on the back of that EV, it's insanely heavy for a combo. It's run pairs of 4x12s to ear-melting levels for gigs, but it's crazy loud just on the efficient internal speaker as well. I tried it, cranked, with a Fluxtone speaker based on the EV in an open-backed cabinet. Then dialed it down as far as it would go. Fletcher-Munson aside, there was all the good stuff but at a volume that would allow a muted conversation. We put it in a room and put a mike on it (try this with your attenuators) loud, dialed down, and then on the internal combo speaker. The obvious differences were between the Fluxtone and the internal speaker (this speaker was the original from 1988), but between the cranked Fluxtone and the dialed-back Fluxtone, very little, approaching nothing. Try that with an attenuator and see what you get.

This is one of the most informative post I have ever read!
In addition to what sounds like a possible final solution to what has seemed to be an impossible, never ending challenge, I also just learned where I can go to dime my amp and get pancakes via room service at the crack of ass!:dude:

Thank You Dude!
 

dspelman

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While we're on the subject -- attenuators exist to reduce the power output of tube amps.

Attenuation isn't an issue for most solid state amps, and that's part of the reason for the popularity of modelers of all shapes and sizes (and price ranges), right up to the high-end Axe and Kempers.

The increasing number of attenuation systems available speaks to the increasing difficulty many of us find in locating a place to use a tube amp at the high volume necessary to produce what we think are traditional rock sounds. We can't even play them full-chat at most gigs any more. At some point, it will strike most of us that a tube amp run to distortion levels is a leftover from another era. It will be as frustrating as driving a 230 mph Lamborghini...well...anywhere. Like the Lambo, it will be mostly a poser's tool, awesome in its potential, lacking in practicality.
 

LPV

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I have often thought that it would be interesting to have a speaker providing a basic attenuated tone on the floor combined with some sort of amplified guitar strap that transmits enhanced mid and lower frequencies directly to your shoulder to mimic the feel of a big amp. Just for quiet home play.
 

dspelman

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Exactly. Hifi speakers systems are design to eliminate compression and any other form of coloration. However, many guitar speaker systems are designed to incorporate and leverage compression.

There are countless drivers that are available with either an alnico or ceramic magnet (hifi and guitar). All you have to do is listen to them to hear the difference.

First, guitar speaker systems are largely not "designed." 4x12s were "designed" to house four speakers (the initial sketch involved chalk on a cement floor), and that's about it. When they realized that they were getting a hellish resonance from the back panel at a frequency corresponding to the partial wavelength equal to the diagonal of that panel, they stuck a 2x2 from the center of the baffle to the middle of the back panel to run it up a few octaves and to reduce the cabinet's "oilcanning." No guitar 2x12 is designed to incorporate or leverage compression. Fact is, these things were simply cobbled up (for in those days T&S parameters were unknown...<G>) and the specific speakers weren't even important; they used whatever was available.

Once again, there are countless drivers with alnico, ceramic, neo magnets. But those drivers also differ widely in magnet structure design, amount of magnetic flux, cone dimension, stiffness, composition, voice coil diameter, coil wire used, cone suspension surround material, vmax and a whole raft of other factors that take precedence in creating sound OVER the magnet material differences. Just look at the differences between a broken-in V30 and a brand new one. The magnet doesn't change, but the sound does.
 

dspelman

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I have often thought that it would be interesting to have a speaker providing a basic attenuated tone on the floor combined with some sort of amplified guitar strap that transmits enhanced mid and lower frequencies directly to your shoulder to mimic the feel of a big amp. Just for quiet home play.

How about headphones and one of those chairs that transmits the bass "bump". Ooooh! a BassShaker!!!

Bass Shakers :: What is a bass shaker?

Maybe we could set up something that would flap pants legs as well.
 

dspelman

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So that's why they do it in hotels, huh.

I haven't been to the NY Amp Show, but the LA Amp Show is held in a separate building of the Airtel Hotel next to the Van Nuys airport, in the rooms (beds and most furniture are usually removed). When you crank your amps, you close the door as a courtesy. They hand out Hear-O's as you come in, and they usually have a few free V-Picks if you're there early on Saturday.

Not at all unusual to be rubbing shoulders with rock royalty (most of whom are in t-shirt and jeans like everyone else). I've had to ask the Premier Guitar people (they wander around doing short vids and interviews) who's who on occasion. Dweezil Zappa, Phil X, etc. Most of the small manufacturer folks are there, so you'll trip over Dan Boul, Bruce Egnater (though I didn't see him last year). If you're looking at amps, it's a far better choice than NAMM, where the sound police are nipping at your booth and where there's just an overall high noise level anyway.
 

LPV

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Would love to attend the LA amp show one day.
 

Soul Tramp

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First, guitar speaker systems are largely not "designed."


I don't agree with this at all. The single most important element in the design of a speaker system, be it hifi or guitar, is the driver. I believe guitar amp manufacturers put great thought into the drivers(s) that will be used.

It's for this very reason a company like Weber offers over 170 different speakers.

Granted the cabs are not designed at Lincoln Labs, but they don't need to be for a guitar speaker system. But despite this there are many guitar speaker cabs designed for specific a voicing and/or purpose.
 

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