passive speakersim shotout..

[Johan]

I sometimes need to be quiet when I want to record, so speakersims is something that have interested me for some time. especially passive ones...taping signal from a speaker out should have plenty of strength even to push a high loss filter..or so I think...here is a small shotout I did a few days ago..
it's a highly distorted JCM800 type amp. the sample is first an sm57 on the speaker( for reference). the rest is the speaker out straight into my soundcard, then "re-amped" through the different speakersims.
the only thing done to the sound is normalizing, so they are all the same level then added slight reverb.

so the order on the soundfile is SM57/straight/trace-elliot/Mesa-boogie/Marshall valvestate8280/CarvinLegacy
http://www.aronnelson.com/DIYFiles/up/passive_speakersim_shotout.mp3

as you can hear, they all differe a fair bit, but I still think it's interesting what you can do with passive filters if you can afford high signal loss( as you can if you taking down a speakersignal to line level)
..only thing to keep in mind is that since they are passive, they will be sensitive to the input impedance that follows
I am collecting all the circuits on one document and will upload as soon as I understand why the file gets so large..( don't fully understand how computers think/work.. )

what do you think?...

j

[Johan]

here is a link to the schematics..
http://www.aronnelson.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=38207&g2_
j

[wavenator]

sounds great!
ill build it soon
thx bro

[George Giblet]

It's an interesting experiment - thanks for posting the results.

I listened to these quietly in the early hours of the morning and they sounded OK but I just listened to them again and for the most part I can hear some buzz coming through, which is a result filter being too simple.    I did some re-normalization particularly for the boogie, dropped about 2dB.

On the whole I think the boogie is the best.  I know a lot of people have said they like boogie in the past.

Forgot to ask what load did you use on the amp output?

[Johan]

It's an interesting experiment - thanks for posting the results.

I listened to these quietly in the early hours of the morning and they sounded OK but I just listened to them again and for the most part I can hear some buzz coming through, which is a result filter being too simple.    I did some re-normalization particularly for the boogie, dropped about 2dB.

On the whole I think the boogie is the best.  I know a lot of people have said they like boogie in the past.

Forgot to ask what load did you use on the amp output?

thank's
yeah, I like the boogie best too..not totaly unlike a sm57 on the speaker and quit passable for late night demoing, I think.
perhaps I should clearify. I only played the riff once.  with a mic on the speaker and the parrallell speaker output going into a mixer then into my soundcard. (so no speakerload was needed)

the first two samples are 0-15seconds SM57 on the speaker, 15-30 seconds is the unprocessed signal straight from the speaker out, so that you have something to compair too.

the four following samples are then the unfiltered/straight signal, "reamped" through the headphone out, through the sims then back in again.
the order being  TraceElliot, Mesa, Marshall and last Carvin
I used a lot of distortion only to get a complex signal with many overtones, as I felt that would be the most telling of how well these performed. and I think it is interesting how well these simple filters perform.
I do have a H&K redbox ( passive version G+) laying around somewhere too, but find that one sounding a bit synthetic althou much more complex than these circuits

when/if I find more of these passive designes, I might do another shotout, or perhaps an "active speakersim.." someday, but for now, I just wanted to share this with you guys

j

[George Giblet]

I only played the riff once. 

Ah, now I get it - thanks.  So it's the same signal from the amp output terminals in each case.

I used a lot of distortion only to get a complex signal with many overtones, as I felt that would be the most telling of how well these performed. and I think it is interesting how well these simple filters perform.

Yes, I agree 100% the wider spectrum demonstrates the difference much more readily.

I ran a simple filter over your raw signal and produce this mp3 file, so the file now contains

SM57/simple_filter/trace-elliot/Mesa-boogie/Marshall valvestate8280/CarvinLegacy

http://www.geocities.com/george_giblet/effects/passive_speakersim_shotout_simplefilter.mp3

I've also re-normalized some of the samples.  It's pretty convincing compared to the other simulators (?).  I could make it slighltly more convincing with more EQ but I didn't want to complicate things.

The "simple filter" can be implemented using only two opamps - wait a sec and I'll draw it up.  I suspect a reasonable approximation could be done with a passive circuit using one inductor like the boogie circuit.  The way I've done it on the sample was using DSP but it's not a fancy convolution thing it's a using filters that directly translate to circuits.

[George Giblet]

I'm going to see if I can improve the low-end match.

[Johan]

The "simple filter" can be implemented using only two opamps - wait a sec and I'll draw it up...
....The way I've done it on the sample was using DSP but it's not a fancy convolution thing it's a using filters that directly translate to circuits.

..that's cool, but then it's not passive anymore.  I kind of like the idea of it being passive and since the high signal loss is not a problem anyway, I'd like to go that rout.
the Mesa sim is, to my ears really good.
I guess the slight lack of low/low-mid is due to impedance missmatch..I guess that could be compensated for a bit by adjusting the pot( at the expence of even more signal loss). on the other hand, I almost allways find myself cuting those frequencys, to give room for vocals and other instruments when mixing my demos
it could also be a more accessible build by rescaling the caps/resistors around a common wha-inductor( 500mH) instead of the 220mH, wich might be hard to find..?..

.I also think it's interesting how well a simple filter like the Carvin-Legacy performes. yes, it lacks in the mids..but hey...it's only three components..

thank's for your input

j

[George Giblet]

I've been looking at the simple passive idea and I've come up with this one.

http://www.geocities.com/george_giblet/effects/gg_passive_sim.png
http://www.geocities.com/george_giblet/effects/gg_passive_sim.mp3

Oh, first sample is your mic'd speaker second is the dsp equivalent of that circuit.

[bamera]

George Giblet

Wow!!!! Sounds amazing for such a simple design

[rnfr]

cool stuff george.  for what it's worth i've read guitar speakers have resonant peak around 3k and then have a steep roll off higher than that.  i think that roll off would help these designs quite a bit.  i'm hearing a bit too much of that "rasp" up there.  other than that they sound great.  you might want to try it out and see how it sounds.

[newfish]

Would any of these designs be suitable for making a headphone out more useable as a recording output, or am I missing the point?

I understand I may need transformers etc for this so I don't damage the Headphone section of the amp.

[grapefruit]

Johan,
What are you using as a load for the amp?

Cheers,
Stew.

[Johan]

after playing with these for a few days, I really think LC-filters is  the way to go.  but I did come up with this one


quiet simple..   ..the Mesa is still better to my ears, but for a quick solution...

Stew. ....the amp had a speaker attached ( celestion super65 ) wich is where I put the mic...the direct signal was taped from the parrallell speaker output, then reamped through the different sim's

j

[oskar]

Hejsan...


I love this thread. Thanks Johan and George.
I would concider going onstage with one of those things. An amp and a speaker simulator... There is an air of herecy about it...   
And good sound is good sound no matter how it was produced...

Johan. The first schematics you present, where are they from?
Did you draw them?
What's the way to go about when you model/mimic a speaker?
Do you run a sinewave through it at different frequencies and register amplitude and phase?
Is there any other conciderations?


Oskar

[Johan]

Johan. The first schematics you present, where are they from?
Did you draw them?
What's the way to go about when you model/mimic a speaker?
Do you run a sinewave through it at different frequencies and register amplitude and phase?
Is there any other conciderations?

Oskar

hallå där Oskar..
...the schematics are "cut and paste" from schematics found on the web..
...I would asume a good way is to first spend some time geting the right mic in the right position, so you have a good reference when tweaking, then record both the direct out and the mic. then finaly tweak whatever circuit you like until you get the same sound with the direct signal through the sim as the reference.

I'm not a big fan of looking at the spec.sheet and trying to match that, since it usually dont tell you much about the dynamic responce across the freq.spectrum, but I guess it can be a good place to start..

..as for signal, I like to use something I'm used to hearing...like the guitar through an amp( I know what that usually sounds like ), but if you're going to look at the signal on a oscilloscope, a low freq. square wave probably tells you most

j

[guitarman89]

hey johan, I've looked at the schems and listened to this sample since yesterday. That sound is amazing but i was wondering about two things:
1) what kind of distortion do you use and what's the tuning of your guitar in it?
2) is there a big difference in terms of level between the recs with sm57 and the simulated ones? (without normalization)

The second answer was born from the computer simulation of the mesa and marshall 8280: there is a big attenuation of the signal which is caused by use of only passive components.

However, nice works Johan, it can be useful!!

[grapefruit]

Stew. ....the amp had a speaker attached ( celestion super65 ) wich is where I put the mic...the direct signal was taped from the parrallell speaker output, then reamped through the different sim's

j

Ah, Ok. I guess you could use a power resistor if you don't want sound coming from the speaker...

Cheers,
Stew.

[Johan]

Stew. ....the amp had a speaker attached ( celestion super65 ) wich is where I put the mic...the direct signal was taped from the parrallell speaker output, then reamped through the different sim's

j

Ah, Ok. I guess you could use a power resistor if you don't want sound coming from the speaker...

Cheers,
Stew.

..thats the plan when I need to be quiet..that or my old powerbreak..

Guitarman.  the amp is an marshall 50w combo moded to groovetubes "trio" mean channel..it's basicly three resistors and one cap away from the 2203/2204 preamp but a bit smoother and a lot more gain
guitar is a Les Paul with burstbuckers, regular tuning.
yes, there is a lot different levels between the different sims, but it doesnt matter...tapping the output, you can loose 95% of the signal and still have a strong line level...( 15watt into 16ohm is a 15volt signal)

j

[Pauldebass]

Hi , i built Mesa Simulator, but it sounds allmost like unprocesed and i would ask you, if the schematic was ok, thx a lot in advance, Paul

It's an interesting experiment - thanks for posting the results.

I listened to these quietly in the early hours of the morning and they sounded OK but I just listened to them again and for the most part I can hear some buzz coming through, which is a result filter being too simple.    I did some re-normalization particularly for the boogie, dropped about 2dB.

On the whole I think the boogie is the best.  I know a lot of people have said they like boogie in the past.

Forgot to ask what load did you use on the amp output?

thank's
yeah, I like the boogie best too..not totaly unlike a sm57 on the speaker and quit passable for late night demoing, I think.
perhaps I should clearify. I only played the riff once.  with a mic on the speaker and the parrallell speaker output going into a mixer then into my soundcard. (so no speakerload was needed)

the first two samples are 0-15seconds SM57 on the speaker, 15-30 seconds is the unprocessed signal straight from the speaker out, so that you have something to compair too.

the four following samples are then the unfiltered/straight signal, "reamped" through the headphone out, through the sims then back in again.
the order being  TraceElliot, Mesa, Marshall and last Carvin
I used a lot of distortion only to get a complex signal with many overtones, as I felt that would be the most telling of how well these performed. and I think it is interesting how well these simple filters perform.
I do have a H&K redbox ( passive version G+) laying around somewhere too, but find that one sounding a bit synthetic althou much more complex than these circuits

when/if I find more of these passive designes, I might do another shotout, or perhaps an "active speakersim.." someday, but for now, I just wanted to share this with you guys

j