Played the tastiest cab ever (IMHO) this past weekend

Rawrawk said:
If you measure a V30 average SPL say LAeq,1m playing with a fairly driven sound, at lest from our experience, you will see that SPL at around 2kHz is quite noticeable when compared to that of say a creamback.
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You need to feed either of those speaker a LOT of power before they get non-linear and the response is materially different than the 1w curves.
 
jay mitchell said:
"Average SPL" is, by definition, frequency-blind except for whatever weighting (A in your citation) you use in the meter.
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Hi Jay, not really. You can record Leq or LAeq for each relevant frequency. The single figure value is actually determine from the log sum of each frequency band.

jay mitchell said:
How do you define "a fairly driven sound" in a way that is repeatable? And what test conditions apply? IOW, cab placement, mic placement, proximity to room boundaries, etc.
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“A fairly driven sound refers to the speaker operating in a nonlinear way, typically when driven by a tube amp with gain settings high enough to induce preamp or power amp distortion. Close-miking at 2 or 3 cm, on-axis, highlights the 2kHz (or 1-3 kHz boost) which becomes more pronounced with harmonic distortion from high-gain signals.

jay mitchell said:
How are you discriminating between "SPL at around 2kHz" and other frequency ranges? And what specifically does "quite noticeable" mean in decibels?
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Just from FR curves. You can clearly see this effect either by recording Leq values or real time frequency response in a DAW software. When we say quite noticeable in this case it means 3 to 5 dB, from our experience.

jay mitchell said:
Correct. There are, at least in principle, no enclosure effects on the response curves. That's by far the most reliable way to compare transducer responses when you don't know anything about the enclosures they'll be loaded into.
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Of course, but it is juts a a setpoint.
That is juts the response at 1m with 1w of power. It changes as you increase power, gain etc. A greenback have a smoother treble response.

jay mitchell said:
Raw transducer response and box modes are independent of each other. Standing waves will alter the response of different speakers mounted in a given box in the same ways. A mode that causes, for example, a response notch at 550Hz will cause the same notch for any speaker mounted in it.
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It does alter the response in the same way. But, if you have a speaker that has a set point frequency response that shows higher SPL at frequencies below 400 or 500 Hz (which the v30 does) than another one you sare comparing it to, once they are both inside a closed enclosure that response (below the first order modes) means almost nothing.


Going back to placing the Vintage 30 on the bottom and Greenback on top in a 2x12 cab, I can see why some players prefer this. The V30’s is louder so sticking it on the bottom uses the inverse square law to tame its output a bit (at ear level, if you are standing). There’s also a floor reflection as the bottom speaker gets a low-end boost and the V30’s tighter bass maybe handles that better than the Greenback’s? Or maybe having the Greenback at the bottom benefits from the floor reflection and balances it a bit better with the V30 )in terms of SPL? Maybe some players just don’t want that V30 midrange growl (that 1-3 kHz punch) dominating all the time, so they stick it lower to reduce it?


I guess my point is that there’s a strong psychological angle too. It’s not pure science I know. Depends on the player and setup.

But it is fun to challenge this "set" beliefs, though, because I see lots of players doing stuff because they read that ... or because the heard that ...
 
Chocol8 said:
0.5 db is perceptible by every single human I have ever tested with a blind A/B test and it is a 3 digit if not 4 digit number of people, including a ton of non-musicians and non-audiophiles. The idea that people can't perceive less than 3db is an Internet myth.

As for why to put the V30 in the bottom, I would use your ears, and also consider weight. I almost always put the heavier speaker in the bottom of a vertical cab.
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Hi Choco,

I have never tested people but I have tested myself a few times and I certainly cannot find a just noticeable diference (JND) of 0.5 dB. Guitar sound are not mid or high frequency pure tones.

There are numerous papers bout this and in summary (from memory though I might be wrong) authors say that:
JNDs in the ~1 dB range for pure tones under lab conditions
JNDs in normal listening are closer to 2–3 dB depending on frequency
 
Chocol8 said:
You need to feed either of those speaker a LOT of power before they get non-linear and the response is materially different than the 1w curves.
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Hi Choco,

You do need lots of power to get to cone distortion. You only need about 20w of power to change the FR considerably with power section gain and less than that with pre amp gain. Even hi-fi speakers do this although to a lesser extent. The 1w infinite baffle response is really just a set point. And this is all not even taking into account the fact that when playing guitar the speaker rarely has "time" go go back to its resting position note after note so this effect of FR change is a constant.
 
Power amp and preamp “gain”/distortion are in the amp. They don’t change the frequency response of a linear driver.
 
Chocol8 said:
Power amp and preamp “gain”/distortion are in the amp. They don’t change the frequency response of a linear driver.
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Hi Choco,

You are right about the preamp.
What I meant is for example in a non master volume amp, the preamp distortion comes first and as you increase gain you are also increasing the voltage the speaker sees. From about 5w upwards the speaker is in non linear territory already.

If you increase the power amp above 5watt you are definitely changing the speaker FR.

In a master volume amp increasing the preamp gain alone should not increase voltage and therefore any FR changes are coming from the amp itself.
 
Chocol8 said:
I don’t know what speakers you are measuring that are non-linear at 5w, but none that I have ever measured was.
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Hi Choco,

This is well established knowledge. n a guitar speaker like a Vintage 30, Xmax is only about 1 mm, so even a few watts of input power can put the cone well outside that linear range. If you want to bid deeper you can read Klippel papers of loudspeakers measurements and you will see that they more or less corroborate what I am saying here.
 
Rawrawk said:
Hi Jay, not really. You can record Leq or LAeq for each relevant frequency.
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If and only if you confine the excitation to that frequency, at which point any non-flat frequency weighting is irrelevant.
Rawrawk said:
The single figure value is actually determine from the log sum of each frequency band.
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State the formula you use to determine the "log sum."

SPL figures that quote a weighting other than flat necessarily apply to broadband signals. They were specifically developed for that purpose. If you're interested in comparing response variations at specific frequencies or in specific narrow (say, 1-octave or less) frequency ranges, then weightings are not appropriate. Direct comparison will yield the correct result. Referencing weighted SPL figures is, at best, superfluous.
Rawrawk said:
“A fairly driven sound refers to the speaker operating in a nonlinear way, typically when driven by a tube amp with gain settings high enough to induce preamp or power amp distortion.
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IOW, levels at which both the linear and nonlinear responses of the amp contribute substantially and will vary depending on load impedance vs. frequency, which is different for different speakers. IOW, the differences you cite could be caused entirely by the differences in the behavior of the amp. Pro tip from one whose entire career has relied on accurate testing of loudspeaker response: in order to isolate the behavior of a speaker, you must eliminate all nonideal behavior from every other element in the signal chain - including power amp, microphone, and analyzer electronics - to the greatest degree possible. If you haven't done so, you cannot attribute the behaviors you observe to any single component.

Rawrawk said:
Close-miking at 2 or 3 cm, on-axis, highlights the 2kHz (or 1-3 kHz boost) which becomes more pronounced with harmonic distortion from high-gain signals.
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Again, this is most likely due to the effect of different impedances on the amplifier's nonlinear behavior (distortion).

Observed distortion products at, for example, 2kHz necessarily came from excitation frequencies an octave or more below that. A speaker's impedance in the range of 100Hz-1kHz will affect the amplifier's distortion in that frequency range, and those distortion products will be manifested (and observered) at higher frequencies. Add to that that a speaker with lower sensitivity will need more amplifier power, which will be accompanied by higher distortion, to be driven to a given level.

All this to say simply that nothing you have described establishes the effect you claim.
 
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jay mitchell said:
If and only if you confine the excitation to that frequency, at which point any non-flat frequency weighting is irrelevant.

State the formula you use to determine the "log sum."

SPL figures that quote a weighting other than flat necessarily apply to broadband signals. They were specifically developed for that purpose. If you're interested in comparing response variations at specific frequencies or in specific narrow (say, 1-octave or less) frequency ranges, then weightings are superfluous. Direct comparison will yield the correct result. Referencing weighted SPL figures is, at best, superfluous.

IOW, levels at which both the linear and nonlinear responses of the amp contribute substantially and will vary depending on load impedance vs. frequency, which is different for different speakers. IOW, the differences you cite could be caused entirely by the differences in the behavior of the amp. Pro tip from one whose entire career has relied on accurate testing of loudspeaker response: in order to isolate the behavior of a speaker, you must eliminate all nonideal behavior from every other element in the signal chain - including power amp, microphone, and analyzer electronics - to the greatest degree possible. If you haven't done so, you cannot attribute the behaviors you observe to any single component.


Again, this is most likely due to the effect of different impedances on the amplifier's nonlinear behavior (distortion).

Observed distortion products at, for example, 2kHz necessarily came from excitation frequencies an octave or more below that. A speaker's impedance in the range of 100Hz-1kHz will affect the amplifier's distortion in that frequency range, and those distortion products will be manifested (and observered) at higher frequencies. Add to that that a speaker with lower sensitivity will need more amplifier power, which will be accompanied by higher distortion, to be driven to a given level.

All this to say simply that nothing you have described establishes the effect you claim.
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Thanks Jay,

I see what you mean I guess but I think you are making all this overly complex. You don’t need to isolate anything if you are simply comparing two speakers with the same amp and settings.

True that in acoustics and audio nothing is really equal!

I was simply stating that a v30 enhances frequencies around 2kHz more than a greenback does despite the 1w infinite baffle plot might suggest otherwise.

This is, I believe the general opinion on v30s.

I am well aware that the amp introduces its own thing to the sound. But anything at and above 5w of power enters non linear region and this is when in my view the 2kHz thing come up!
 
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