Weber MASS Attenuators

Tube or solid-state, this section goes to eleven!

Re: Weber MASS Attenuators

Postby phatt » 01 Nov 2010, 14:06

Rogue wrote:
phatt wrote:Hi chum,
Have you considered the DI Box might be the problem?
If me?
I'd have the lid off and a quick schemo down on paper to see whats happening inside that thing. :scratch:

Check my simple *Voltage divsion on page 3* thats all you will need.

If you wish to use the weber, a speaker or resistor,, or other weapon of choise makes little diff as long as you have a load the Voltage division works a treat.
Phil.

I don't think the DI box is the problem. Like I said, I did a test where I recorded a progression with the Weber attentuating and recorded the same progression just be turning the Weber to bypass. The bypassed signal sounded much better, and even more interesting the wave form looked more "free" as well.

This is kind of what the waveform looks like with the Weber attenuating...

Image

This is what it looks like with the Weber bypassed...

Image

These are not the pictures from my test, but that is what basically what they look like. The levels were the same. The sound of the bypassed weber sounds much better, more open and clean, than the attenuated signal and the waveform would suggest it as well.

I haven't tried more expensive attenuators, but I suspect they all pretty much degrade the signal at full load.

I measured the load from the weber. It's about 27ohms.


As for using the speaker motor alone....DON'T!!!!! I tried it and there was arcing around the magnets. I very quickly ended this experiment as I didn't want to damage my amp. :)


Hi Rouge,
Those two screen shots have got me to thinking again. :scratch:
Have you considered that you might not be picking/strumming the guitar as hard in bypass mode?
I noticed you mention you use a 50Watt Amp somewhere,,, so it would be an automatic reaction to play a little less hard without attenuation engauged. This would definitly give a difference in SPL going to tape.
(Yikes A 50Watt Amp in a small room is deafening )

The only way I can think of to be sure would be to isolate the Amp in a sound proof room and have someone switch Attenuator on and off without you knowing while you play the song through a headphone set or monitors.

Just a thought.

If the problem is still there then yes absolutely the attenuator is effecting the level out.
In which case I'd look at the voltage division in the weber unit. (If that is where you take you line level from?)

The 3 schematics shown here use voltage division that to my mind is way to low.
I believe the series resistance should be large so as to isolate it from Speaker,Attenuator or whatever load.
Phil.
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Re: Weber MASS Attenuators

Postby Phatburner » 01 Nov 2010, 15:02

Well not exaxctly 'just an inductor" no. The coil is floating on the pole piece just as in a speaker motor. A normal inductor when made on a core is generally glued to the core so there is no movement. With this device there is a complex interaction involving eddy currents in the core which I'm thinking will result is a different response than a normal inuctor.

J
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Re: Weber MASS Attenuators

Postby dubyayoungq » 30 Dec 2010, 19:37

Has anyone actually tried to build one of these from the schematics provided? I was going to try to put a kit together for my son's Birthday as a project he and I could work on, but it rapidly became economically unrealisitc. I don't know if you all have super cheap parts sources, but just going to my local electronic supply shops I was over budget, and that didn't include the speaker motor (which I had ordered for $45 plus shipping) and the giant 50 ohm 100 watt rheostats, which I haven't seen for less than $50.00, or a box to put it in.
Just curious if anyone has successfully built one of these.
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Re: Weber MASS Attenuators

Postby phatt » 01 Jan 2011, 12:00

dubyayoungq wrote:Has anyone actually tried to build one of these from the schematics provided? I was going to try to put a kit together for my son's Birthday as a project he and I could work on, but it rapidly became economically unrealisitc. I don't know if you all have super cheap parts sources, but just going to my local electronic supply shops I was over budget, and that didn't include the speaker motor (which I had ordered for $45 plus shipping) and the giant 50 ohm 100 watt rheostats, which I haven't seen for less than $50.00, or a box to put it in.
Just curious if anyone has successfully built one of these.


Hello dubyayoungq, $Cost !! Welcome to the world of electronic stuff. 8)

If you care to read *Soulsonics* posting you will notice that he mentions there is very little difference between this Over-hyped *Mass hysteria speaker* and a real inductor (when all mathamatically dusted down it's just a friggin inductor)
and none at all.

Mass driver or inductor will matter little,, AND use of either will only make small differences in the sonic result.

So just throw your money at a couple of big fat resistors and be done.

If you tell me how manty Watts the Amp in question is outputting then I can throw up some schematics for you if you wish?

Note I have personally built and USED *Live* some of the stuff you read about so although I can't argue the maths I can tell you what works and what is mathamatical mindless dribble from a guitar player perspective.

Attenuation done without any serious *Compensation setup* will always be less than ideal,, especially at very low SPL outputs.
Cheers, Phil.
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Re: Weber MASS Attenuators

Postby dubyayoungq » 04 Jan 2011, 01:09

Thanks Phil,
I did read all of the posts, which only enforced the fact that I'm in over my head :shock: , and trying to put this together on my own wasn't going to be worth it! I just bought a used Weber Mass on ebay and fixed my problem! :horsey:
I was just curious if anyone had used the schematics *Soulsonics* provided, and successfully built an attenuator from them, and what it cost them to do it.
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Re: Weber MASS Attenuators

Postby mangy » 17 May 2011, 09:21

Just to add some info on using an l-pad.. Was reading some tech specs from a manufacturer of a metal & ceramic cased wire wound l-pad rated at 100w with 0db attenuation.. the power rating/attenuation curve followed 50w/-2db, 35w/-6db & 25w/-12db which I guess is why they only work well for lower powered amps etc..
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Re: Weber MASS Attenuators

Postby phatt » 17 May 2011, 09:42

I think mangy will find that if you pull one apart and consider that at the lowest attenuation there is only a few turns of wire that cop the full power and this is why they blow up if overdissapated.

Be very aware the 100 Watts is refering to *System power* inside a crossover circuit where a lot of low frequency (the Low FREQ is burns up resistive elements) is bypassed and sent to the Woofer.

So you have to derate that 100 watts if you want to use them at full bandwidth.
Phil.
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Re: Weber MASS Attenuators

Postby alexp » 06 Nov 2011, 21:41

Soulsonic,

by comparing your Weber Mass 150 schematic to the Mass 150 that I own, bought in 2009, I noticed some differences:

    Speaker motor shows 16Ohm resistance, not 8
    the speaker motor is connected in parallel with the 4x16ohm resistors, not to the rheostat
    the caps are 4.7uF, not 10uF (that's a minor difference of course).
Do you think that this is correct, or that they might have incorrectly mounted / soldered it?

Thanks for your help!

Alex
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Re: Weber MASS Attenuators

Postby mstang01 » 07 May 2013, 20:36

Really interesting schematics (I know this is a really old thread but it's new to me). So for a truload type test setup would you basically dump the output,bypass, and tone sections and tap your DVM and O-Scope jacks off the line in? Would the speaker motor still do anything in this config? Looking at the MassLite I was a little unsure if the impedance of the speaker motor affected anything or if that is purely defined by the load resistors.
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Re: Weber MASS Attenuators

Postby rockgod212 » 11 Aug 2017, 04:45

does anybody have the weber 200watt mega dump schematic? looking to build a beefed up air brake type attenuator.
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Re: Weber MASS Attenuators

Postby Latam » 19 Nov 2017, 11:14

Hello everybody! I'm new here, but I've already went through this tread. And I've been wondering - you solve using of a speaker motor in attenuator, but have anybody tried just to connect motor parallel with normal speaker cabinet? I'm looking for solution which provides just a little bit of attenuation. And 3 or 6 dB should be enough for me. So do you think it's possible to connect a speaker motor or just some old speaker with removed cone? Just like this guy did? https://mhuss.com/SmallBox/page7.html

Are there any potential problems? Thank you in advance!
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Re: Weber MASS Attenuators

Postby phatt » 19 Nov 2017, 15:11

Yes the idea is valid BUT you can't just remove the cone as that helps the stability of the VCoil. There is an inner spider (around the VC) and then there is the cone spider (the one you can see around the edge of the cone) you would have to add a stiffer spider for the VC if you remove the cone which is not a simple task,,May as well just purchase the motor. [smilie=a_whyme.gif]
Phil.

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Latam (20 Nov 2017, 19:18)
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Re: Weber MASS Attenuators

Postby Latam » 20 Nov 2017, 19:16

Hello Phil, thanks for quick reply! I thouht it wont be so easy. Do you have any idea where to buy a speaker motor? Weber do not sell them for more than 10 year I guess. In additon, their motor nowdays look pretty different:
Image vs Image

And also regarding the other components, Im a little bit puzzeled. Weber in past recomended this wiring
Image
but in that picture i found with motor mounted in a cabinet, motor is wired just parallel
Image

EDIT: I found an interesting video where someone is making a generator from speaker. The way he placed the ball onto in might be a way how to stabilize VC, or not?
https://www.youtube.com/watch?v=XU_OHh2JR1c

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Re: Weber MASS Attenuators

Postby phatt » 21 Nov 2017, 13:17

Sorry I don't have any idea of where to purchase the motor, others here might help. The ball on the VC you linked to should work but a lot of muckin about to setup. :hmmm:
(Clever idea and shows you just how much EMF energy is sent back to an amplifier [smilie=a_holycrap.gif] )

If all you need is to reduce the SPL of the Speaker Cab then as long as it's not a 100 Watt monster rig the simple 50 Watt Lpad will work for a lower wattage Valve Amplifier,, say around 30Watts.

Lpads work fine until you turn down to very low Level then it's just 90% resistor and hence the Back EMF from the VC is no longer working against the output.
Lpads get a bad rap BUT if you run an Lpad higher on the dial then the Amp output is still receiving a fair bit of Back EMF from the VC so it's still fairly good.

Another way around the issue is to use Speakers with a lower SPL. :secret:
I did that for a chap some years back who had a speaker which had insane SPL which made the Amp very harsh,, I replaced the speaker which made the rig far more usable for the style he played. He was about to dump the Amp it was so bad,, he was so glad he brought it to me :mrgreen:

I'm not sure what you mean about the Huss drawing of his Cab?
Without the motor it's a 16 Ohm Cab (2x8R in series = 16R)
With motor engaged it's an 8 Ohm cab (2x16R in Parallel = 8R)
A lot of quad box layouts use the classic 4x8R drivers wired series/parallel brings the total Z back to 8 Ohms.
The huss drawing it effectively the same trick.
HTH, Phil.
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Re: Weber MASS Attenuators

Postby Latam » 21 Nov 2017, 20:42

Hi Phil, thank for reply. Im already using a preatty weak amp (15w blackstar artisan) and 1x12 with heritage greenback (96dB). I also owned original Weber Mass, but the efect on sound was significant, so I sold it. Thats why Im looking for "pure" solution for minor attenuation. The best option would be to have a second cabinet closed in other room, but thats no possible :) Thats also why I didnt consider Lpad.

Regarding the wiring - Huss is clear for me. But I dont understand the Weber wiring - there are two resistors used and I dont know why - Huss wiring make more sense to me.

Btw. today, I bought a cheap hi-fi speaker, 8ohm, 60w with only 86dB. Ill try to conect it parallel with my cabinet and close it insto some small "iso cab". If it wont be sufficent, Ill try to put some weight on cone or make some holes in it :)
https://www.ges.cz/cz/reproduktor-arn-150-03-8-GES07000196.html this one

Matěj
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Re: Weber MASS Attenuators

Postby phatt » 22 Nov 2017, 07:33

Arr-huh now see what you ask.
Both drawings show speaker and motor in *Parallel*
The only difference is that there is resistance in between motor and speaker, the second resistor is a pot to allow some volume adjustment.

Regards to SPL
I had an old powered subwoofer with a bulitin LM3886 50W poweramp.
By simply removing the low pass filter and adding a preamp it certainly pulled down the SPL to bedroom levels. (you need to block off the port otherwise it farts) The same Amp through a normal MI speaker was very loud.
This allowed me to crank the OD without ripping your ears off,, Considering it was not a MI speaker it sounded pretty good.

Something that folks need to realize about any kind of Attenuation is the "Munson effect" (Google Munsons Curve for an idea of what happens)

The effect is well understood by engineers;
Those old silver face HiFi Amps from years past often came with a "Loudness switch" when engaged the high and low frequency was boosted to keep the sense of fullness. It was often wired so that past halfway on the volume the effect was bypassed otherwise it got too boomy.

At low levels the big sound is lost and it's the way our ears work so not much you can do,,unless you buy a set of Elephant Ears, [smilie=a_chuckle.gif]
That's why we cup our ears to hear low levels to increase the pickup area because the definition is lost down low.

I went with a reamping system for a small Valve Amp because you can do post power stage tone adjustment as well as post power stage effects.
That brings back the BIG sound but at much lower SPL.
Of course that is more complex to setup but vastly better than attenuation alone.
Phil.
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