Closed Speaker Resonance PA equalization tied to Master Volume level

[shatteredsquare]

I'm chasing an amplifier master volume characteristic behavior at an obnoxious and unnecessary level of minutiae. When the MV is barely cracked the lows should be nil, barely there, super thin, highs too. As MV comes up from barely cracked, the lows and highs should get drastically more prominent and bloom into the MV sweet spot.

 

[FractalAudio]

I'm chasing an amplifier master volume characteristic behavior at an obnoxious and unnecessary level of minutiae. When the MV is barely cracked the lows should be nil, barely there, super thin, highs too. As MV comes up from barely cracked, the lows and highs should get drastically more prominent and bloom into the MV sweet spot.

Says who? I've never seen, heard or measured an amp do this and I've measured hundreds.

 

[shatteredsquare]

Says who? I've never seen, heard or measured an amp do this and I've measured hundreds.

It's mainly in the lows, and it's probably mainly in this one particular model (recto modern, no negative feedback). If you have the master super low, 0.05 and turn the Speaker LF resonance down to 0.00, keeping the Speaker HF resonance at default, that's what I'm using to hearing when you barely crack the amp MV open. Not a lot of balls. As the MV comes up, the effect I'm using to hearing as the amp moves into its sweet spot, blooming, is that of turning up the Speaker LF resonance along with the MV. I understand the speaker resonance points themselves don't change much, but that's the only control I can use to reduce the resonance effect on the output equalization. The boost/bloom happens in the highs too in a similar fashion, just to a lesser extent. That's how you can have bass and treble cranked at bedroom levels, but if you just turn up the master with those settings it usually needs a lot of re-tweaking...you have to readjust the tone controls...to accommodate the new EQ curve that the output section now has...on a gradient depending on where the MV is set.

 

[FractalAudio]

It's mainly in the lows, and it's probably mainly in this one particular model (recto modern, no negative feedback). If you have the master super low, 0.05 and turn the Speaker LF resonance down to 0.00, keeping the Speaker HF resonance at default, that's what I'm using to hearing when you barely crack the amp MV open. Not a lot of balls. As the MV comes up, the effect I'm using to hearing as the amp moves into its sweet spot, blooming, is that of turning up the Speaker LF resonance along with the MV. I understand the speaker resonance points themselves don't change much, but that's the only control I can use to reduce the resonance effect on the output equalization. The boost/bloom happens in the highs too in a similar fashion, just to a lesser extent. That's how you can have bass and treble cranked at bedroom levels, but if you just turn up the master with those settings it usually needs a lot of re-tweaking...you have to readjust the tone controls...to accommodate the new EQ curve that the output section now has...on a gradient depending on where the MV is set.

Compared to what? You keep making these statements with nothing to back them up except ostensibly a 10-year old memory. I just showed you a tone match that proves you are completely wrong and you keep at it.

I'm out.

 

[chris]

Why would there be a dip in the lows when it's barely cracked open?

When the MV is barely cracked the lows should be nil, barely there, super thin, highs too.

these statements seem opposite.

 

[shatteredsquare]

these statements seem opposite.

right, the baseline would be the speakers frequency response on it's own, low MV, barely cracked open, just like that tone match plot. The bloom is when you add speaker impedance curve + power amp resonance to the equation...it's additional equalization effect applied to whatever signal would be coming through the whole rig. The bass boost comes from the speaker impedance curve and its influence on the power amp resonance, its bass boost, and some highs, forms an EQ scoop that gets stronger the higher you push the MV.


with MV barely cracked you would see a frequency response that looks close to the speaker frequency response as published by the manufacturer, the power section isn't flexing hard enough to be adding much tonality to the signal, looks like that tone match plot.

as MV comes up, the power section starts flexing harder against the speaker, the speaker impedance curve starts having more influence on the power amp resonance (especially in a recto modern mode, no negative feedback), and the result at the listener position is amp bloom, more bass/highs/scoop. Resonances are being added to the signal, an additional layer of equalization on a gradient connected to MV level. Coincidentally its a similar EQ curve to fletcher munson, but it's not just fletcher munson. There are physical resonances being added on a gradient connected to MV level, that has to be measurable.

 

[GreatGreen]

@shatteredsquare It seems like you're describing the Fletcher Munson curve. It's a theory that explains how the human ear hears things. Basically, at low sound pressure levels, your ear hears mids the most prominently. At high SPL, low bass and high treble sound louder. It's not the amp that puts out relatively more bass and treble as you turn it up, it's your ears and brain being more sensitive to bass and treble at those louder volumes.

https://ehomerecordingstudio.com/fletcher-munson-curve/

So any extra eq layers that add more bass and treble like you're talking about should probably be applied post-everything. Like not just guitars, but the entire mix.

edit: just saw this has already been covered in the thread. So to answer your 1. and 2. points... your eyeballs would shake because of the additional volume, which will still raise the bass (that vibrates your eyeballs) equally with the other frequencies. As for making the PA sag and fart out... yes the bass frequencies are probably doing that, but again, that's the bass being raised equally with the other frequencies.

It's all your human ears and human brain hearing things differently at different volumes.

 

[shatteredsquare]

@shatteredsquare It seems like you're describing the Fletcher Munson curve.

Fletcher munson is occurring simultaneously, as it does anywhere else you turn something up louder. Incidentally, the fletcher munson curve is similar to the same scoop curve as the speaker impedance curve. You're getting both at the same time. It isn't just fletcher munson.

Coincidentally its a similar EQ curve to fletcher munson, but it's not just fletcher munson.

the speaker impedance curve starts having more influence on the power amp resonance (especially in a recto modern mode, no negative feedback)

Resonances are being added to the signal, an additional layer of equalization on a gradient connected to MV level.

There are physical resonances being added on a gradient connected to MV level,

@shatteredsquare
So any extra eq layers that add more bass and treble like you're talking about should probably be applied post-everything. Like not just guitars, but the entire mix.

A Mesa Mark amp with a graphic EQ set to the standard scoop shape boosts lows and highs, cuts mids. The Rectifiers in modern mode don't have negative feedback in the power section, so the impedance curve of the speaker has the effect on the power section to boost lows and highs in a similar fashion as a scooped graphic EQ. The difference being on a Mark amp you get to add the scoop in manually. In a rectifier, the scoop amount is a result of how high the MV is set, that's why you have to crank them to get the roar. The harder the power section pushes against the speaker, the more the speaker impedance curve makes the power section resonante along that scoop and that scoop shape gets imprinted in the sound, just like a graphic EQ. At very low MV levels, the resonant EQ effect should be nil in a rectifier....as you turn up, the EQ effect should become stronger on a gradient, up to the MV sweet spot, past which point it just starts falling apart.

 

[GreatGreen]

I promise that what I’m about to say is being said to help you, not to be mean...

You are flat out, factually incorrect about that. You are objectively wrong. You don’t know what you are talking about. Amps do not work that way. At all. Master volume does not have this effect on the way an amp follows an impedance curve. An amp does not “naturally scoop more” as you turn it up. I’m sorry you think it does, but it does not. People have literally shown you data proving this in this thread. Any relative increase in bass that you think you are hearing is due to the nature of how the human ear works, and how the human brain interprets sound. It’s your ear and brain being more sensitive to deep bass and high treble at high volumes that makes you think the amp is “approaching to match” the impedance curve. That is not actually happening outside your own head.

You’ve had multiple people who know what they are taking about, including the founder and technical lead of a decade+ old company at the absolute top of this industry directly tell you that you are wrong, exactly how you are wrong, and have then gone on to explain what actually happens, and they have all matched in their explanations. An amp’s output EQ does not work in the way you are explaining that it works. Turning the amp’s volume up does not change the impedance curve. An amp’s output impedance curve does not change depending on volume. You are wrong.

Think about it. If an amp’s impedance curve always changes dynamically with volume, how could they even measure what the impedance curve is supposed to be in the first place? Impedance curve measurements don’t have an agreed-upon industry standard volume level because volume is not a relevant variable. It doesn’t matter. The impedance curve is the same no matter the volume.

It sounds to me like, even not considering Fletcher Munson, if anything, you think the way you do because you’re used to amps with badly designed master volume knobs (like 5150s and old Rectos) where with the volume turned as low as it can possibly go while still producing some audible sound, you still get the slightest treble bleed through with no bass frequencies present, and you don’t get all those frequencies represented until you turn up to at least TV volume, so you think this is evidence of some kind of impedance curve shift. That’s not what’s happening though, it’s just an imperfect Master Volume control whose fault is slight treble bleed through at very low settings.

 

[shatteredsquare]

Turning the amp’s volume up does not change the impedance curve. An amp’s output impedance curve does not change depending on volume. You are wrong.

Think about it. If an amp’s impedance curve always changes dynamically with volume, how could they even measure what the impedance curve is supposed to be in the first place?

Nowhere in three pages did I or anyone else once ever mention the amp's output impedance curve changing in relation to MV level. That's not even relevant to the topic. The topic is referring to the effect of the speaker impedance curve on the power amp resonance at differing MV levels, and the resulting added output EQ curve that becomes prominently stronger with increasing MV level, specifically in an amp with no negative feedback in the power section (recto modern modes).

That’s not what’s happening though, it’s just an imperfect Master Volume control whose fault is slight treble bleed through at very low settings.

That's new information to me and makes perfect sense, and could also be a source for output frequency differential at different MV levels.


When the bass goes to flub above a certain MV level it's from power section distortion, distortion happens in the low end first because there is increased low end being produced by the speaker impedance curve making the power amp resonate more along that curve until there is no longer sufficient energy to push the requested low end. That tells me that prior to the power amp falling apart, there is an output equalization gradient that will be getting stronger along the speaker impedance curve up to that point, directly proportional to MV level.

 

[Randalljax]

3 pages in an I am still not sure what OP is trying to do

SS , Cliff has been doing this a long time and could likely write a university paper on it


Perhaps it time to just let it go as a wish

 

[GreatGreen]

Nowhere in three pages did I or anyone else once ever mention the amp's output impedance curve changing in relation to MV level. That's not even relevant to the topic. The topic is referring to the effect of the speaker impedance curve on the power amp resonance at differing MV levels, and the resulting added output EQ curve that becomes prominently stronger with increasing MV level, specifically in an amp with no negative feedback in the power section (recto modern modes).

These are literally the same things. A tube amp's output impedance curve is what the speaker dictates it is, meaning an amp's impedance curve is the speaker impedance curve. It's the same thing.

When the bass goes to flub above a certain MV level it's from power section distortion, distortion happens in the low end first because there is increased low end being produced by the speaker impedance curve making the power amp resonate more along that curve until there is no longer sufficient energy to push the requested low end. That tells me that prior to the power amp falling apart, there is an output equalization gradient that will be getting stronger along the speaker impedance curve up to that point, directly proportional to MV level.

With respect, you are incorrect. That is not an opinion. You are factually wrong. There is not relatively increased low end being pushed to the power section as the MV is increased. The same relative amount of low end is being pushed to the poweramp no matter what the volume is. The key is that with a speaker impedance curve like the one you showed earlier in the thread, the low resonance is often the loudest frequency, so it's going to hit the poweramp's breakup threshold before any other frequency, yes, but the other frequencies are still being increased equally with the low end. If the master volume is increased and it causes the low end to increase by 5 db, the mids are also going to be increased by 5 db, as well as the highs.This is going to happen equally whether the master volume is increased from 10% to 15% output, or 50% to 55% output, etc. Before the tube breakup threshold, the lows do not increase more than the mids or highs as the master volume knob is turned up, whether by speaker impedance or any other means, because the speaker impedance curve is not dynamic. It does not impart a different curve on the amp as it increases in volume.

 

[shatteredsquare]

With respect, you are incorrect. That is not an opinion. You are factually wrong. There is not relatively increased low end being pushed to the power section as the MV is increased. The same relative amount of low end is being pushed to the poweramp no matter what the volume is.

Never said there was increased low end being pushed to the power amp. I said the power amp starts to resonate more along that speaker impedance curve...boosted lows/highs as the MV comes up, forming the scoop on the power amp output EQ on a gradient connected to MV level. It's an integral part of how the recto gets its sound, the reason why you have to crank the MV to get them to sound good, the reason why they are intrinsically difficult to dial in, and the reason why when you do get them dialed in in the real world, if you barely bump the master it's no longer dialed, because the power amp output EQ curve has changed. It's recto modern mode specific, most amps have negative feedback in the power section and don't respond like this to the speaker impedance curve.

The key is that with a speaker impedance curve like the one you showed earlier in the thread, the low resonance is often the loudest frequency, so it's going to hit the poweramp's breakup threshold before any other frequency, yes, but the other frequencies are still being increased equally with the low end

If the master volume is increased and it causes the low end to increase by 5 db, the mids are also going to be increased by 5 db, as well as the highs.This is going to happen equally whether the master volume is increased from 10% to 15% output, or 50% to 55% output, etc. Before the tube breakup threshold, the lows do not increase more than the mids or highs as the master volume knob is turned up, whether by speaker impedance or any other means, because the speaker impedance curve is not dynamic. It does not impart a different curve on the amp as it increases in volume.

A resonant peak is a prominent bandwidth. There is a low resonant peak and a high resonant peak in the speaker impedance. There is no middle frequency resonant peak. When that speaker impedance curve starts effecting the power amp resonance as the MV comes up, the resonant peaks cause increased low end and high end output equalization at those peaks. The middle bandwidth does not have a resonant peak, the middle doesn't get boosted. That forms an EQ scoop that gets stronger on a gradient the higher the MV gets pushed, an additional layer of power amp output equalization, from power amp resonance, along the speaker impedance curve.

 

[GreatGreen]

You are incorrect. Amps don't work like that. That is simply not how tube amps work, with or without negative feedback.

When that speaker impedance curve starts effecting the power amp resonance as the MV comes up, the resonant peaks cause increased low end and high end output equalization at those peaks.

No, they don't. You are wrong. This does not happen. At all. Ever.

The middle bandwidth does not have a resonant peak, the middle doesn't get boosted. That forms an EQ scoop that gets stronger on a gradient the higher the MV gets pushed, an additional layer of power amp output equalization, from power amp resonance, along the speaker impedance curve.

No it doesn't. That is not how amps work. You are wrong. This does not happen. At all. Ever.

Anything having to do with these dynamic changes you are describing that you think you are hearing is due to the Fletcher Munson curve which is a phenomenon that happens inside your head. Nothing is actually dynamically changing on the part of the amplifier+speaker in this way. At all. Ever.

I'm sorry, but I can't contribute anything else to this conversation as long as you continue presenting these ideas you simply dreamed up in your imagination with absolutely zero science behind them as fact. Good luck.

 

[FractalAudio]

 

[yek]

. It's an integral part of how the recto gets its sound, the reason why you have to crank the MV to get them to sound good, the reason why they are intrinsically difficult to dial in.

The last thing you want to do with a rectifier is crank its master.

Furthermore, the rectifier is a reasonable straightforward, simple amp to dial in.

 

[hippietim]

Furthermore, the rectifier is a reasonable straightforward, simple amp to dial in.

Exactly! You simply unplug it and get a Marshall.

 

[yek]

Exactly! You simply unplug it and get a Marshall.

 

[AlGrenadine]

Exactly! You simply unplug it and get a Marshall.

Some kind of blasphemy

 

[lscottk]

Quote from GreatGreen: "No it doesn't. That is not how amps work. You are wrong. This does not happen. At all. Ever."

This discussion in general and GreatGreen's comment quoted above remind me of this:

Monty Python's Dead Parrot Skit