V8 Thought the same - leads me in to a noobie question. Let's say we've got a SM57, how would you mic up a cab to get the 'cleanest' (I'm not sure what word to use here) response for the purposes of Modulator's experiment?

The way to correct for the microphones frequency response is to apply the inverse EQ, see pic

Black is the frequency response of the Shure SM57, red is the EQ you need to apply to get a flat frequency response into the recording (excuse my paint skillz)

There is one thing I am unsure of, according to Shure there is a proximity effect when the mic is close to the source, check halfway down this page (http://blog.shure.com/how-to-read-a-microphone-frequency-response-chart/) where they talk about the Beta 58A. It looks like the proximity effect causes a prominent bass boost, but I'm not sure how much of a role that plays when mic'ng up a cab.

I guess if it were me (and in the absence of fancy test equipment) I would keep alternating between playing some notes on the the instrument and listening to the recording while playing with the EQ until they sound identical. You have to trust your ears at some point ?

Re: the proximity effect, I'm going to leave this here:

https://ledgernote.com/columns/studio-recording/microphone-proximity-effect/

@klaasvakie - thanks, all very interesting!

I'll use the summation on ledgernote as my takeaway : "The goal is always to "get it right at the source." And that means don't take close miking too literally. Maintain at least 12 inches of distance between your source and your microphone unless you specifically intend to draw upon the bass response of tight proximity"

I am not an acoustic engineer/expert, and finding one with time to do this sort of thing for free to post here is not going to happen. Fortunately the professionals do this and info is available. What I would have liked to do (time permitting) is to do this in an acoustically "neutral" room, with good recording equipment, decent software, and Hi-Fi playback. To test the instruments will be an interesting project in itself. "Testing" speaker choice will have me recording the guitar (acoustic with microphone, electric will have to go straight from the pickup to the recording medium), do the equalization filters to "simulate" various guitar speakers (in "pure" form, no effects from room, cabinet, amplifier), and play back through the Hi-Fi to see if one can actually hear a difference in response. In no way does this relate to the real-world sound you will get from a cabinet. But it might help to decide whether you fork out money for the green backed thing or a cheap speaker, or to decide between two or three options. All the time remembering that you are doing this to find a setup which pleases your ears.

I'm sure many thesis'es have been done on this, and surely the manufacturers do this all the time. As I said, I needed to know. And also see that some more questions pop up. As for now, I will have to use my equipment, and have frustrating fun.

I need a better microphone, without spending a nice playable SX's worth of money. I was thinking about an USB mike for the laptop. Any advice?

modulator

Where do you plan to play? How much damage does it need to withstand? If you're going to take it live, you'll want something sturdy. I have a Shure SM58 that I use for live gigs and it is built like a beast. I also have an AKG C214 that's great for vocals.

Slightly off topic, but how do you evaluate the frequency response of a pair of speakers? Is there any software tool that will do it?

Norman86 posted in another thread (uhm, moderators, how does one reference here?):

2 x 8" Celestion drivers in a custom cab, 200W power handling...
Celestion TF0818 drivers..

oh, and it's WAY too loud. I love it! ?
And yes, it's mine! ?

Two Celestion TF 0818 drivers for a 200 Watt 2 x 10” cabinet. These are Hi-Fi drivers, low-midrange, specified frequency response of 70 – 6000 Hz, sensitivity 94 dB. Rated power 100 Wrms. The interweb is full of horror stories about using Hi-Fi speakers for guitar, most of the arguments against it not well thought through, defeating themselves. The consensus seems to be, plug your guitar amp into a Hi-Fi cabinet (driver) and you will cause Earth’s atmopsphere to ignite in a supernova fireball, destroying life as we know it. Some even venture to say that guitar speakers are full on all the time, whereas audiophile type (read PA?) speakers have a on-off (loud-soft) job, so run cooler, etc. Sure. Listening to some heavy music, that Hi-Fi driver has to handle not only one guitar, but drums, bass, keyboards, more guitars, screaming (sorry, vocals) etc. And live gigs through a PA is not for sissy speakers, but they are full range flat response (like Hi-Fi) cabinets and run hard all the time. While the guitar amp/speaker is run just enough to monitor, being miked to the deck etc.

Note the TF0818’s frequency response curve, off-axis: It drops off nicely at 3KHz. The on-axis peak at 3 – 4 KHz is much like a guitar driver, so I would venture a guess that adding a “beam blocker” over the dome will result in a pleasing guitar speaker without shrill painfull treble. And the speaker will have a more “controlled” sound as well, if the user does not try to drive it into flubbering destruction.

Indeed, Celestion now markets a speaker for modelling amps, a true full range flat response speaker, the F12-X200. 60 Hz – 20 KHz. Look at that response curve:

It has a 97 dB sensitivity rating too. I would merely remove the on-axis compression driver to get the ideal “guitar” speaker. Note the catalogue blurp implies that this speaker allows you full control over your sound. So where are the Hi-Fi type speaker detractors now? The times (and requirements) have changed.

I feel I have to put my 5c in here so here we go, note these are generalisations, differt speakers may have different "ideas" I am not looking at HF units for this discussion.

Hi Fi speakers
Generally need to be fairly compact, have extended bass and flat frequency response, to achieve this sensitivity at anywhere from 85 to just over 90 dB is generally way too low for guitar or PA applications. Power handling is usually smaller as it is just not needed in the average living room.
Car speakers
Will be of lower impedance, usually 4 Ohm, to match the requirement of the car amp which runs into a lower impedance to provide more power with less current draw and therefore less drain on the battery. They need to survive the harsher enviroment in a car, perform in less than ideal placement positions and get loud enough to overcome the background noise level.
PA or pro audio speakers
The bigger more powerful units will have very stiff cones and heavy voicecoils. Bass response will be limited in order to get decent efficiency and most will need a properly designed ported or otherwise loaded cabinet. They respond slowly and with less attack compared to a guitar speaker. Power handling will be higher when driven by high continuous power amps but this will reduce substatially on a bass or guitar amp. Less costly units will have more in common with guitar speakers such as lighter cones and suspensions and smaller voice coils but still need good continuous power handling. This improves sensitivity at the expense of bass response but who needs 40Hz from their guitar?
Bass speakers
Obviously need to get lower down than guitar speakers but still need attack and good sensitivity. Power handling needs to be high but additionally they ney need to cope with sudden large inputs and cone movements from percussive playing styles.
Guitar speakers
This is where the "dark arts" of speaker design come in. guitar speakers are designed to produce a specific tonal quality and to break up in a particular manner when overdriven. Frequency response graphs are virtually meaningless in illustrating the results you will get. Guitar speakers sensitivity is often 97dB or more, response drops off sharply below 80Hz and they respond quickly to small nuances in the signal. Smaller cone drivers such as 6 or 8 inch will have much in common with the less costly pa drivers discussed above but 12" speakers are another story.

The new modeling type amps provide a different requirement with a need to tonally influence the signal as little as possible. For the audience these are usually fed to the FOH PA system and for the guitarist back to the monitors.
In the "old days" most of the guitar sound reaching the audience came from the on stage guitar cabs, think double stack (or more) 4 x 12 cabs and 100W valve heads. Oh, and incidently, guitarists with damaged hearing. This is no longer the case and the crowd is used to hearing guitar sound through the PA. Not so the guitarist who now has to listen to wedge monitors which do not have the same characteristics as a guitar cab.

This is why Celestion have developed the new Copperback and the F12-X200. The intention is to keep the "feel" of a guitar speaker while providing a fairly neutral platform for the modelling gear to do it's work. I feel the F12 will be more suited to studio work and the Copperback to live but time will tell. There would not be much point in removing the HF driver, just use a Copperback instead.

Another reason why you would want a full range speaker in a modelling amp is that the cab simulation is usually part of the modelling, so playing it through a guitar speaker will effectively apply the speaker frequency response twice.

I have a Line6 Amplifi practice amp which explicitly has a full range speaker (but no published frequency response). This allows me to load different cab-sims in software and still reproduce them as they should be. This also means that the Line-in/Bluetooth inputs get reproduced accurately and only the guitar bits get their frequencies chomped.

Obviously there can be some lively debate about the ability of the Line6 to model a cab accurately in software, but the principle should stand.

Good information on speaker design here. OK, more questions pop up as to Hi-Fi, where sickening amounts of cash gets spent buying equipment which allows the fortunate owner to be "at the concert" 24/7/365. From that I assumed that the speakers have the ability to reproduce the tiniest nuance and sound of good (this is important) recordings. The lightest pick attack, the smallest squeek, the subtle hammer-on, etc. Which apparently happens.

Another thing is that the only reference I (and most other people alive) have of the classic rock sound, the true blues tone, what Clapton sounded like in studio when he recorded whatever, Gilmour's magic tone, is derived from Hi-Fi. We have recordings to listen to, and form opinions of what we like, but that is possibly not what it sounded like when played.

I never had good guitars, good amps, good speakers. I have never heard/played any . I cannot blindfolded say "Fender/Marshall/Vox" and ID speaker cabinets, strings, guitars. My only reference is my Hi-Fi. The few live shows I attended was coloured by the PA 'Mix". So what does a guitar really sound like? Likely why I am not getting the "tone".

So to add to this... Patrick Quilter of Quilter amps and QSC audio has many, many speakers at his disposal.
I'm pretty sure he knew what he was doing pairing his amps with the "hifi" speakers.

As I said in the other thread, if you're in JHB, you're more than welcome to come check my cab out and listen to how it responds.

"OK, more questions pop up as to Hi-Fi, where sickening amounts of cash gets spent buying equipment which allows the fortunate owner to be "at the concert" 24/7/365. From that I assumed that the speakers have the ability to reproduce the tiniest nuance and sound of good (this is important) recordings."

Yes exactly. I spent most of my younger years in the hi fi business when it was still fresh and good fun. Good Hi Fi speakers, like any other speaker, are a compromise of factors but are trying to achieve a diffent goal to PA or others.
They must:
Be reasonably sized
get loud enough to fill the listning room
have a broad, flat, smooth frequency response
look good
and be priced reasonably.
There are of course exceptions, I have seen very large hi fi speakers, heard very loud units and also some awful units with spitty top end and boomy or "one note" bass.

The objective of a good hi fi system should be to reproduce the source as closely as possible AND allow the listner to enjoy the result. Some do a very good job but something is always missing. How many times have you heard music from another room or outside a venue and you just know it's live before you walk in? Hi Fi just doesn't do that for me.

"So what does a guitar really sound like? Likely why I am not getting the "tone"."

In my opinion a guitar should sound like, well, the way you want it to.