Guitar player lingo: what does "spongey" mean?

[Rhodesplyr]

In the last few weeks, I've had one guitar player tell me that he likes his amp because it has "spongey" highs, and, last night, someone told me he was looking for an amp with a "spongey" tone.

I've smiled and nodded both times, but, to be honest, I'm not really clear about exactly what these guys are referring to in terms of tone, other than the fact that it seems generally to be a favorable evaluation. If I had to guess, I'd say that it meant compressed, but I'm not sure.

To ask the question another way, are there any particular amplifier characteristics that tend to produce a 'spongey' tone, such as tube rectification, voltage sag, compression, etc...? To what degree does the speaker contribute? What is the opposite of 'spongey'?

Or could anyone point me to an example of a recording featuring this tone?

[exclamationmark]

The thing about all these words is that they're subjective... they have no real definition (audiophile reviews make me burst into fits of laughter).

I can however give you MY opinion. Playing a little game of word association, we realize sponges are soft. Something soft is usually easily compressed (aha!). Soft things are also very good at damping things. (I know this is silly, but it's probably how people relate sounds to physical phenomena/objects). Transient response is related to damping and is mostly influenced by the type of output stage. Fixed bias, big tube stages, (6l6, kt88, etc), tend to be very 'hard' sounding, in relation to the fact that they have a very fast transient response. They also don't distort much or clip at sensible input levels, hence don't compress the signal (and usually have a crapload of NFB). Cathode biased, small tube stages, however, are usually driven to higher levels (clipping), producing a more compressed signal (also having no NFB). You can also look into damping factor and how it affects speakers, although it's mostly a solid state amp thing. Tubes generally have lower damping factors than their solid state cousins, and hence control the speaker LESS effectively, leading to a difference in tone.

Adding to this, we can get tube rectifiers which 'sag' when a hard chord is struck, reducing voltage to the amp (thus reducing headroom) compressing the signal further. This can also have a sort of 'blooming' effect, where the signal will slowly increase as the voltage charges back up.

In regards to the 'favourable evaluation' it would definitely depend on the genre on music. 'Spongy' sounding amps usually tend to have terrible bass response, whereas with 'harder' sounding amplifiers you can feel it hitting you in the chest! (hence popular for metal genres).

[Mark Hammer]

Though we attribute much to tubes and other things, "sponginess" frequently stems from the characteristics of the power supply. Not just in the guitar-amp world either. For instance, car audio folks have historically referred to additional or higher value power-supply caps as "stiffening" the power supply and amp, by providing reserve current.

In the pedal world, there have been numerous devices and efforts to mimic the legendary "dying battery" sound with fuzzes. In most instances, this simply consists of reducing the voltage supplied by an adaptor. However, because the adaptor provides robust current at that reduced voltage, it doesn't quite nail the effect of a well-used carbon-zinc battery that can supply enough current for an instant but is quickly depleted by a transient in a circuit set for high gain. Again, it is the peculiarity of the power supply that creates the "sponginess". not the audio circuit itself.

One of the things that "sponginess" gives you, however, is the ability to elicit different tonal quality from pedals and amps by how one picks, without necessarily producing substantial changes in volume level. That's a desirable quality, since it allows one to separate the tonal aspects of emotional expression from the volume aspects; a useful characteristic in a band context.