Seems all the waveform generators available, whether PC based or stand alone, do not permit automatic amplitude correction. Here's the issue: using an electric guitar, my low E produces an output of about 250mV immediately after the pick strike, while the note on the 22nd fret of the high E string chimes in at 100mV.
Is there a way to sweep through all the guitar frequencies, or any musical instrument, while simultaneously correcting the amplitude? I know it's possible to build one, I just want to purchase something. Battery powered preferred.
It may not make a difference in most situations, but if one were to build a speaker cabinet and test it, would not a constant amplitude possibly yield erroneous results? For instance, say a 2kHz signal at an amplitude that will never be achieved in a real world scenario, causes a resonant frequency to oscillate the cabinet, or otherwise ruin the natural speaker response.
Is there a way to sweep through all the guitar frequencies, or any musical instrument, while simultaneously correcting the amplitude? I know it's possible to build one, I just want to purchase something. Battery powered preferred.
It may not make a difference in most situations, but if one were to build a speaker cabinet and test it, would not a constant amplitude possibly yield erroneous results? For instance, say a 2kHz signal at an amplitude that will never be achieved in a real world scenario, causes a resonant frequency to oscillate the cabinet, or otherwise ruin the natural speaker response.
It is my understanding the compressor would compress the high amplitude notes and amplify the lower amplitude notes, thus everything would stay the same. I never messed with one of those, with the exception of fuzz boxes, which essentially do the same thing except for the near, square wave output. Roger McGuinn of the Byrds used two in series. It yielded his unique tone and I bet it made the guitar easier to play with finger picking.
In my experience it depends a lot on how you set the compressor. But the part about it being easier to play electric guitar with lots of compression is spot on in my situation (but I'm not that bad on electric bass guitar though...).
Well, I'm trying to keep it simple. I found a free 32 band EQ plugin for Audacity: 32 Band RedRockSound.pro The guitar has a fairly narrow range of fundamentals, so I would want at least ten bands to cover the range D2-E6, which is the inclusive span of the Drop-D through the highest note on the high E string if you have 24 frets.
Wow, I do not have much experience with Audacity, except I remember messing with the built-in EQ. It had these lines that were dragged up and down with the mouse. I just used it to get rid of bass in one a cappella song. I planned on doing a 2 minute, continuous sweep for my testing, but individual notes should work, too. A half step isn't that much. I guess you were contemplating using the amplitude adjustment for each note, which is in dB. Well, I'll try the EQ and see what happens. I don't have good linear mic to do a real test, but right now my concern is cabinet vibration, as it is lightweight. There was significant 60-100 Hz flexing at high power and had to add stiffeners. It is a semi-sealed cab, and for the first test, the rear cover was flexing between the mounting screws, and in the center, even with the stiffeners. A center support plus extra screws were added. Sounds good though. Thanks everyone for all the tips.
It´s not good engineering to build a somewhat flawed speaker cabinet and "pray" certain frequencies are not played through it.
You simply can´t count on that,Murphy´s Law rules 🙁 (don´t ask)
I suggest you drive your amp and speaker hard, even into clipping, (hint: Guitar cabinet), using band limited Pink Noise instead.
Cut below 80Hz and above 5kHz and you´ll have a pretty good approximation.
Detect and correct any vibration, buzzing, flapping you detect and then sell/use that cabinet with confidence.
Disclaimer: built and sold over 10000 Guitar and Bass speaker cabinets over 50 years.
Thanks. I'm aware of Murphy's law--both parts, and, especially in a live guitar environment, one should pay heed to it.
Agreed it must be tested hard with given the peaks of my 80w amp can hit 250w. into 80w worth of speakers. The stress was quite dramatic in my preliminary testing. Only the back cover was an obvious problem.
I never heard of using pink noise for this. It makes sense, though, since actual guitar output is a cacophony of frequencies, especially all those harmonics produced by fuzz.
But why not any of the other colors of noise?
Oh, it is quite multi purpose 🙂
Plain white noise stresses tweeters if present, new kid in the block Red noise (I didn´t even know it existed) sounds like distant thunder or a subway running below, it might be good to test subwoofers, not the case here.
But the "fine tuning" to pink noise comes to band limiting it to frequencies of interest.
Almost forgot the real detector of rattles and resonances is a slooooowwwwww sweep, from 20 Hz (no music there but you might have some ugly resonance) to , say, 1 or 2 kHz.
Painfully shows them.
Just last week I made a very light 2 x 10" 100W guitar combo out of 12mm plywood, with front and back panels using 9/10mm .
Sweeping it showed an ugly resonance, probably coming from an internal void or layer-to-layer poor gluing.
I found an area where hand pressing from both sides: outside and inside showed it, nothing visible from outside, no bulgings, nothing.
So I drilled a 4 mm hole NOT reaching the far edge and injected (with a needleless plain syringe) some polyester resin, because it is quite fluid , and left it overnight.
It worked, apparently it diffused and filled some internal void.
Plain white noise stresses tweeters if present, new kid in the block Red noise (I didn´t even know it existed) sounds like distant thunder or a subway running below, it might be good to test subwoofers, not the case here.
But the "fine tuning" to pink noise comes to band limiting it to frequencies of interest.
Almost forgot the real detector of rattles and resonances is a slooooowwwwww sweep, from 20 Hz (no music there but you might have some ugly resonance) to , say, 1 or 2 kHz.
Painfully shows them.
Just last week I made a very light 2 x 10" 100W guitar combo out of 12mm plywood, with front and back panels using 9/10mm .
Sweeping it showed an ugly resonance, probably coming from an internal void or layer-to-layer poor gluing.
I found an area where hand pressing from both sides: outside and inside showed it, nothing visible from outside, no bulgings, nothing.
So I drilled a 4 mm hole NOT reaching the far edge and injected (with a needleless plain syringe) some polyester resin, because it is quite fluid , and left it overnight.
It worked, apparently it diffused and filled some internal void.
Good info. That may have been one reason Fender used solid panels, (besides the dovetail joint) and they are open-back. I had a blackface Vibrolux that surprised me how heavy it was empty. The super thick alum. chassis and transformers topped off the Patton tank. I'm expecting my semi-sealed, combo design to present some unexpected results. 9-10mm is 3/8" nominal, which is what I used for the whole thing, but it's heavily stiffened. The baffle is glued to the sides and bottom, and since it's semi-sealed, there had to be an internal "top" which the last place the baffle is glued to. The amp sits above it with the traditional top above.
How slow would you have the sweep you mentioned? I made one at 100 seconds; I think now it should be much slower so not to miss anything. Maybe 3 minutes....
Congratulations on being brave enough for making that thin walled cabinet.
I do that often because some of my customers go on Tour and travel as light as possible.
2 to 3 minutes sweep is fine, just be focused because some resonances are narrow and either side of them there´s no problem.
Or use a hand controllable oscillator, either by pot or touching a screen, so when you hear something weird you can back to the exact annoying frequency.
I do that often because some of my customers go on Tour and travel as light as possible.
2 to 3 minutes sweep is fine, just be focused because some resonances are narrow and either side of them there´s no problem.
Or use a hand controllable oscillator, either by pot or touching a screen, so when you hear something weird you can back to the exact annoying frequency.
We can get the cab and the amp only so light, after that it's the speaker iron and magnet. Powered electromagnet speakers are feasible today with light ferrites and light SMPS supplies but $$$$.
I read an article where some guys designed a guitar cab made out of Kevlar or some kind of composite. Same there, too expensive.
Is the oscillator you refer something that shakes the cab or is it totally electronic?
I read an article where some guys designed a guitar cab made out of Kevlar or some kind of composite. Same there, too expensive.
Is the oscillator you refer something that shakes the cab or is it totally electronic?
The oscillator I mention can be hardware , as in a PCB inside a small case with a potentiometer selecting frequency and turned by hand, or a software one, many "frequency generator" Apps available.
There even is one where you can set automatic sweeps, within any frequencies you choose (say 20Hz to 200Hz) and how long it takes.
As of weight, in my particular case I also make the speakers themselves, so as light as possible in their class.
Here´s my own 10" 80W version, physically similar to Jensen C10Q-MOD1050-Celestion Tube 10, etc.
Only 1600 grams / 3.5 Lbs.
No significant savings going NEO, which in any case I can´t magnetize 🙁
There even is one where you can set automatic sweeps, within any frequencies you choose (say 20Hz to 200Hz) and how long it takes.
As of weight, in my particular case I also make the speakers themselves, so as light as possible in their class.
Here´s my own 10" 80W version, physically similar to Jensen C10Q-MOD1050-Celestion Tube 10, etc.
Only 1600 grams / 3.5 Lbs.
No significant savings going NEO, which in any case I can´t magnetize 🙁
White noise is all highs, will not excite bass much.
Pink noise is reasonable except the sub-50Hz energy may be too exciting, and the >2kHz energy adds to the spec without really stressing the speaker much.
40+ years ago EV proposed a filtered noise, pinkish with the extremes cut; the sweet trick is that the implementation could be simpler than a proper pink filter. I think it was the basis of an IEC standard.
Random noise never has the thump-thump-thump-thump abuse of real music. Put Inagaddadavida and LA Woman on auto-repeat all night long.
No spell needed, I answered in another thread (the flat speaker cable one) showing these same speakers that on this exact same "mechanics" (frame, magnet , polepiece and plates) I can build MANY speaker versions, changing the "soft" parts: cone, suspension, voice coil, adhesives.
With same frame, 6.35mm plates, 102x15 mm magnet and either 32 or 38mm polepieces, in an extreme up to 45mm ones, I regularly build speakers from 12/15W paper voice coils for old "Alnico sound" to 20W Nomex ones to 50W Kapton to 80W Aluminum former (which stands and spreads heat better) to 100/120W woofers with aluminum or epoxy fiberglass edgewound copper or aluminum ribbon windings, in different lengths.
"Alnico sounding" ones use real old school "speaker cement": nitrocellulose based, while for higher power ones I use Swiss made CIBA high temperature oven cured Industrial Epoxy, as tough as can be.
In fact in the 80´s my shop caught fire because the speaker drying oven had an electrical malfunction while I was not at home, came back to find Police cars and Fire trucks at my door 🙁
The very best investment decision in my 53 year career making Guitar amps was to invest (heavily) into making my own speakers. BY FAR
Besides setting up the metallurgical shop to make chassis and panels at home, transformer winding machine, carpentry, painting (including oven dried Industrial paint), silkscreening, a lathe for speaker parts, paying for punching - stamping - pressing - injecting dies for corner protectors, strap handles, knobs, rubber feet, small horn drivers, cast frame speakers, the works.
All of them "free" after 1 or 2 years production and cash cows since.
Just NOW making a plastic thermoforming machine for custom pedal boxes, small chassis covers, DIY power bricks, etc.
I was wrong about electromagnet speakers; they are still around. Here's an interesting discussion: Design Discussion Electomagnet Speakers
Cost, complexity, weight, power wastage makes this approach no good for light guitar amps. What I do like is the option of adjustable field strength which, according to one respondent, affects the response drastically.
My intuition that SMPS is the way to go, and probably a resonant type which is better for fast load changes, is correct. The iron and magnet are gone and replaced with very light, low iron, ferrite, the same as the power supply that would power it.
Or, if you have a good PA system, just get a fuzzbox, and run it into a Pignose.