Speaker load simulator?

[Svart]

I just read about a device that simulates a speaker load on an amplifier so that you can use the amplifier's speaker output like a direct out to your preamp/line input.

They seem to all be pretty expensive.. ???

I assume it's just a big resistive power divider..  Or is it more?  Do they use inductive division? Active loads?

Anyone know what's inside that is supposed to make them so special?  Do they react differently over frequency/power like a real speaker?

what gives?

 

[CJ]

There are a few different ideas out there, you can make your own if you have a blown speaker around.

Glue the voice coil into the magenet gap and put it in a box, you are done as soon as you run the two wires out and solder the crockadile clips.
Equal time for Crocks, they have teeth too.

 

[Svart]

OK.  But how do you tap off of this for a direct out?

Like this thing:

http://www.thdelectronics.com/product_page_hotplate.html

I've seen a couple different ways that people claim to do it from simple resistor dividers to fully reactive loads.  How can we simulate it for real?

 

[schmidlin]

The speaker simulators react properly from the AMP's standpiont, and not necessarilly from an audio standpoint.  There is no real substitution for speaker load/mic'd, ie: with it being driven sonically to the point of saturation/fat/compressed sound.  Half of the the equasion is being ignored: the speaker itself has much to do with it.

If you are looking for an easy way to saturate an amp for studio purposes, check out compensative loads like the Weber Mass: it adjusts for lost and gained frequencies dependant on load.  Not cheap, but a nice option if you don't want to go the mic rout. 

Again, the right speakers add some real color to the sound, and a simulator may fall short.

 

[Curtis]

I'm currently doing a bit of DIY explorations into this sort of thing.  The dummy load is used to present an electrical simulation of the speaker when connected to an amp.  Speakers typically have a big impedance "lump" at circa 100Hz, which then tapers off back to the nominal impedance of the speaker (4/8/16/whatever ohms) at around 400Hz, before gradually rising again up around a few KHz.

Check out Aiken Amps for a good explaination of DIY-ing a speaker load circuit.  Go to "Tech Info", "Advanced", "Designing a reactive speaker load emulator".

Note that the dummy load simulates electrically what the speaker does to a connected amp, but it doesn't simulate acoustically what the speaker sounds like.  To get a usable signal to DI with you tap off the signal at the amp's speaker output, pad it down, and pass it through a bunch of peak/notch/HPF/LPF filters to get a roughly accurate guitar cab sound.  The dummy load is just one part of the chain.

There are a few threads floating around here on the subject, try searching "Speaker simulator" or "Guitar dummy load".  There's also the Groove Tubes patent that has a lot of interesting stuff in it.  Search for patent number 4937874 at http://www.patent2pdf.com

 

[PRR]

> Do they react differently over frequency/...

Yes.

> ...power like a real speaker?

Sorta.

> Glue the voice coil

Lose the bass resonance, a big bump which is significant on some guitar amps.

A speaker may be modeled to the amp as a 6R resistor, a 1mH choke shunted with 20R, and a parallel L-C of 10mH||330uFd.

These will be BIG parts if you must sell to any fool with $400 in his pocket and a 400W amp in his van. (Yeah, the specs say max 185W, but who reads specs?)

The coil-to-air transfer function is far too complex to do right. Most just shave the highs, and of course attenuate a lot.

The one you cite also has a lamp expander to reduce hiss in soft passages. AND it has a HI-power attenuator which goes in-line to your speaker, you can play a 100W amp at 1W levels (as well as play silently to line-out).

For what it is, with 2-year warranty, $330 street is not unreasonable.

Note the generally 5-star comments in the online stores, 9.3 at Harmony Central.

 

[tv]

http://www.richardbrice.net/hot_lamp.htm

looks simple

personally, I'd build it PTP on a riveted perfboard (the ones with no copper)

 

[abbey road d enfer]

I assume it's just a big resistive power divider..  Or is it more?

There are all sorts of cabinet simulators:
The simplest being a voltage divider with a rool-off cap at the output, and a power resistor at the input
Then there are those that emulate the frequency response of a cabinet; some do it passively, with LCR filters, some are active, some are even digital.
And there are those which include a real loudspeaker and a real mic in a sound-proof cabinet. generally the loudspeaker is a smaller size than a typical guitar speaker, with a good power handling but low efficiency, and tuned to exhibit the same humps and dips in the frequency response as a standard cabinet.
Anyway, they are all approximations, and will never beat the real thing:  a large diaphragm that distorts and resonates, air that is pushed in a more or less linear way, and another diaphragm that, again, distorts and resonates...
On a DIY point of view, I think the best approach, and the most satisfactory is the speaker-and-mic-in-a-box. Good performance is almost guaranteed, as lonfgas you know how to choose the speaker for the restricted volume, and you use a good mic. You can even make the thing in such a way that you can try different mics.

 

[Svart]

I like that hotlamps thing..

 

[sahib]

Marshall had one with a multitap auto-transformer as  power attenuator but I do not remember what it was called.

 

[okgb]

Just like a leslie or tube / xfmr combo [  instead of a o/d/ box ] , there's no way to replace the air
of mic'ing in a room we know that , but even if you stick a mic in a box with a speaker
it tends to sound  [ to me  ] as dry as if it were a simluated direct and often bassy because
of the closeness .
FWIW the best results i've gotten are using the hotplate into a palmer D.I. type speaker
simulator into a Millenia STT-1 [ with favorite amp ] this is simular to a set up Satariani
uses / used
But of course a ribbon  with any other mic combo does rule for gtr amps

 

[Tubefreak]

Marshall had one with a multitap auto-transformer as  power attenuator but I do not remember what it was called.

That would be the Marshall PB-100 Power Brake, their sonic qualities don't seem to be very sought after. But Marshall also made an SE-100, which is a very roughed build 100W speaker load + speaker sim with several nice options. Incluiding 18dB of power attenuation or simple full loading a 100W amp. It's 19" 2HE case is full with oa transformers, chokes and high power resistors.

I've used it in conjunction with a Palmer PDI-05 speaker sim. They compliment each other well. The Marshall is more mid orientated, the Palmer is more aggressive with a V shape sound.

Both are nice replacements for mic/cabs, imho. I've used the Palmer during gigs, which made life on stage easier. But for studio work... nothing beats a good sounding room with a nice cab (Bogner comes to mind) and some nice mics. On the other hand, for home/silent recording these speaker sims are easy to use and good sounding. I've bought two SE-100's and one PDI-05 for aprox 250 euro each, well worth their money imho.

Motherload seems to be the beesknees of speaker sims/loads that are produced today. Haven't tried it.
http://www.motherloadusa.com/motherload-amplifier-load-box-recording-products.asp

For my website I made a list of these products a few years ago:
ADA:
MicroCab  19", 1U, speakersim, several options
Ampulator   19", 12ax7 driven poweramp sim + speaker sim

DMC:
Cab Tone   small, speaker sim, several options

DOD:
285 Cabinet Emulator   small, DI Box

G-Tronix
Stimulator   small, stereo, speaker sim, several options
Power Control   small, powersoak, 2 presets

Groove Tubes:
SE II Speaker Emulator   19", several options + powersoak, mono, 1U

Hughes&Kettner:
Red Box Pro   small, 4x12" or 2x12" sim
Crunch Master    small, ECC83 + EL84, poweramp + speaker sim
Cream Machine     small, ECC83, poweramp sim + speaker sim

Koch:
Load Box 120   small, speaker sim, several options + powersoak

Kolbe:
Attenuater   small, powersoak
Silent Speaker    small, powersoak

Marshall:
SE 100 Speaker Emulation System   19", several options, 2U
PB-100 Power Brake   small, powersoak

Palmer:
PGA-04   19", speaker sim, several options + powersoak, mono, 1U
PGA-05   19", stereo speaker sim, several options, 1U
PDI-03   19", speaker sim, several options + powersoak, 1U
PDI-09   small, speaker sim, several options

Rath:
PSB-1   1/2 19", Tube sim+Speaker sim, 1U
PSB-2    same as above, without tube sim

Rockman:
PS3-Power Soak   small, powersoak

Rocktron:
Phantom Cab    speaker sim, several options
Juice Extractor   19", 1U, powersoak, several options

Sequis:
Motherload     19", 2U, advanced powersoak / speaker sim

THD:
Hotplate   small, powersoak



Aikenamps.com has some nice articles on this topic!
http://www.aikenamps.com/spkrload.html
http://www.aikenamps.com/DummyLoads.htm

Maarten