Cabinet recommendations

[Eric***]

The Power Block is SS and needs some clean headroom. At its 75 watt rated output, that's shaving the headroom. That cab should be fine with the Power Block...................you're not going to dme it.

Yeah, I figured it was too low for a power block (which I did manage to score last month for $60), but was just asking in general. Seems like most 12" cabinets I have noticed are well above 100 watts, like 300 watts or something.

[Plank_Spanker]

Keep in mind that you will probably never dime out the Power Block. Given that, the cab you are looking at will more than likely work just fine with the Power Block.

Chances are the Power Block will start clipping before you hit the stop on volume.........................and that will kill just about any speaker, regardless of power rating. More speakers are killed this way than by being over powered.

[Eric***]

Chances are the Power Block will start clipping before you hit the stop on volume.........................and that will kill just about any speaker, regardless of power rating. More speakers are killed this way than by being over powered.

Oh, good point on not exactly needing that much power.

So wait, SS clipping will kill a speaker, or just severe clipping in general?

[Plank_Spanker]

Oh, good point on not exactly needing that much power.

So wait, SS clipping will kill a speaker, or just severe clipping in general?

Clipping is clipping........SS or not. Severe clipping is the killer.

The cab you mentioned should work just fine with the Power Block as long as you don't dime it out. Your ears will stop you before you get there.

[Eric***]

Clipping is clipping........SS or not. Severe clipping is the killer.

I did not know that. Interesting.

[Bloozcat]

A couple of other factors to consider when choosing a speaker cabinet:

Closed back/open back were mentioned, and your choice is usually dictated by the venue in which you're most likely to play. The closed back cabinet is directional and generally used where you want to project your sound over a greater distance. For instance: If you're playing in an auditorium/gym setting where you want to ensure that your sound reaches accross the room, over the people in it, and is clear and audible in the back of the room.

An open/semi open back cabinet is more suitable for smaller venues like clubs where you want the sound to "surround" you and your audience - which will likely be in close proximity to the stage. Think Marshall stacks with their closed back cabinets being used at large venue concerts vs. open back combo amps used in club settings.

Speakers sound different depending on which back you choose as well. Some like closed back, some open back, and some do both well...differently, but well.

And then there's the size of the cabinet. There are formula's as you noted (like the "golden rule formula"), but they are mainly applicable only in closed back cabinets. Still, a cabinet should be of sufficient size so as to allow air to move around an not stiffel the tonal range of the speakers. Some cabinets on the market are just too small to allow the speakers to "breath" properly and the tone is thus affected.

The size of the Avatar 2X12 cabs are similar to the older Fenders and others out there. The Avatars, and others of this size/dimension, have sufficient volume to allow the speakers to properly breath. When I make a 2x12 cab, I use the dimensions from an older Bandmaster cab because I know that size works...for both open or closed backs.

[tunghaichuan***]

Chances are the Power Block will start clipping before you hit the stop on volume.........................and that will kill just about any speaker, regardless of power rating. More speakers are killed this way than by being over powered.

To add to what Plank_Spanker said: this is especially important when dealing with solid state amps. Tube amps clip softly and gradually. A solid state amp will stay clean right up to the point when it clips and then it square waves, and as Plank_Spanker said, this kills more speakers than putting too much power into them.

[Eric***]

To add to what Plank_Spanker said: this is especially important when dealing with solid state amps. Tube amps clip softly and gradually. A solid state amp will stay clean right up to the point when it clips and then it square waves, and as Plank_Spanker said, this kills more speakers than putting too much power into them.

That's sort of what I was asking (albeit in a very unclear way) in my response. I didn't realize this was an issue -- what about clipping makes it a speaker-killer?

[tunghaichuan***]

That's sort of what I was asking (albeit in a very unclear way) in my response. I didn't realize this was an issue -- what about clipping makes it a speaker-killer?

It's not the clipping, it's the square wave clipping. Most tube amps clip, but do so in a gradual and softer fashion. When a solid state amp clips, it is sudden and you get the square wave variety.

Here is a good discussion on the subject:

http://www.bcae1.com/2ltlpwr.htm

Severe Clipping (square wave):
It always amazes me when I hear some idiot driving down the road and the audio is clearly distorted (is that possible :-). Many people drive their amplifiers into what could be called a square wave output (white line below). When an amplifier is pushed that hard, it is actually possible to drive the speaker with twice as much power as the amplifier can cleanly produce into the speaker. As you can see below, the yellow sine wave is the maximum 'clean' output that the amp can produce. When an amplifier is pushed way too hard, the signal will eventually look like the white line. The effective voltage of the white line is ~1.414 x the yellow line. This means the the total power driven into the speaker by the clipped (square wave) signal is double the power delivered by the 'clean' signal (yellow line). This means that the power is double but the cooling of the voice coil will not increase in proportion with the power increase (since the voice coil isn't moving as much as it needs to be for the given power dissipation). This will lead to the voice coil overheating. If we compared the output of a 100 watt amp (the one that's clipping) to a 200 watt amp, the 200 watt amplifier would be able to push the speaker as much as 40% farther than the 100 watt amp (depending on the frequency of the signal). This extra travel (in each direction from its point of rest) would result in added airflow around the voice coil.

[Ch0jin]

Well said Tung, I was about to write up a similar explanation

It's really important when we discuss things amp and speaker related to keep tube amps and SS amps separate, lest more misinformation be spread around the web. SS and Tube amps could not be more different in the way they operate, they are in fact almost polar opposites to each other, so it -should- be obvious that the rules are quite different.

Clipping is a fine example, as has been explained here. People try to drive tube power stages into clipping because it sounds more musical, where a SS power stage should never ever be forced into clipping.

Something I'd like to drop in here is power ratings. Everyone who has dimed an 18W, or heck, even a 50W tube amp will tell you emphatically that 50W tube is FAR louder than 50W Solid State. Myself included. One of the main reasons behind this phenomena is actually to do with clipping, hence my thought to include it here.

Surely an amp rated to deliver 50W RMS is delivering the same 50W RMS as a SS amp right? If not, our fancy "Watts" and "RMS" measurements are meaningless surely? The good news is a SS amp and a tube amp rated at 50W RMS will both deliver exactly the same amount of power, so our rating system is in tact.

For the sake of this explanation I am overlooking the fact that a SS amp designed to deliver 50W will do so consistently from amp to amp and from day to day, whereas a tube amp, especially an older one, will see it's power output vary depending on your mains voltage, age of tubes and filter caps etc. Thats another discussion.

I'll also gloss over the very real effect of signal compression on perceived volume by simply stating that tube power stages compress the signal and this makes it sound louder, SS amps don't do this anywhere near as well, if at all.

Anyway, so we know both amps are capable of pushing 50W of power into the speakers, so why on earth does the tube amp sound so much louder? Well, as I said, it's to do with the way tubes and transistors clip, and also the way our ears hear.

Before I launch into the next bit, I'll explain what I mean when I refer to clipping and distortion, because again, it's confusing. Especially when us electro-nerds keep referring to clipping as part of a distortion pedal!

Distortion happens when you feed a signal (your guitar for example) in one end of a device and it comes out the other looking different. It can be a change so small we need to measure it in .0001 of a percent, or it can be a horrible screaming mess that obliterates the original signal. It's all about the original signal being reshaped in any way.

Without going into why clipping occurs, although I'm happy to if anyone wants me to, clipping is where the top and bottom of our nice smooth signal are sheared off. Because we have altered the signal, clipping is therefore a form of distortion.

A tube amp has more distortion at signal levels below clipping than a solid state amplifier. A lot of the flowery terms we use to describe why the cleans of a tube amp are more pleasant than a SS amp are really just prettier ways of describing what is actually low volume distortion. Yes, your big old Fender is actually distorting the signal long before you hear any "grit", or "growl" or "bite" or, well you get what I mean.

Incidentally, this inherent distortion is part of the reason tubes are rarely used outside the music game these days. If you want clean, linear amplification, for audio or otherwise, transistors run rings around tubes.

This tube distortion increases slowly until the signal starts to clip, and then more rapidly after the onset of clipping. You know this sound as the roar of a cranked tube amp.

The SS amp on the other hand has no such gradualism. It is almost perfectly non-distorting right up to the point that it clips, and then it clips HARD.

Hang on. I've just said that both SS and Tube amps will clip and therefore distort the signal, although they both do it in a different way, so how on earth does that make one louder than the other?

Well, in the end it actually comes down to evolution, or God depending on you point of view, because it's actually a result of how your ears work.

For reasons unbeknown to me, the human hear detects the effect of hard clipping transistors as harsh distortion, and the softer low order harmonics generated by tube clipping as musical distortion AND VOLUME.

So simply put, all that extra distortion in a tube amp at full noise is detected by your ears as volume! Something that can't happen with a SS amp. If we drive a SS amp into clipping our ears just tell us "OUCH"

So there you go. I'm not at all a religious guy so I say this in jest, but maybe this phenomena is Gods way of saying "Play Tube Amps"

[marnold***]

Great stuff, Ch0jin. I was just doing some more research on this too, because my 20W Jet City does sound much louder than my 30W Vox. Granted, besides the tube vs. SS thing, it's not exactly an apples-to-apples comparison. For example, the Jet City has a 12" speaker vs. the AD30VT's 10". The Jet City enclosure is also bigger and better constructed. Both have Eminence speakers, although I'm pretty sure the Jet City one is not made in the U.S.

It seems counter-intuitive that a meter would tell you that two amphs are at the same volume but our ears are telling us something entirely differently. Of course, compression also helps explain why commercials on T.V. are so annoyingly loud, even though the volume hasn't increased.

It's good to have one's mind blown in a non-pharmaceutical way every so often.

[Eric***]

Cool stuff. Thanks for posting that.

When I was reading your intro, the point I figured you would end up making is something like this:

If you're looking for clean headroom, perhaps tube and SS would be of comparable volume. However, the entire spectrum of clean into clipping is considered "good" on a tube amp, whereas when a SS amp cilps, you're pretty much done with its volume range. Therefore, an 18W tube seems to have more volume/power than a 50W SS.

But then you blew my plan to pieces by saying something else...

So my question to you: is there anything to the stuff I wrote above, or is it just me being completely incorrect?

[Ch0jin]

Cool stuff. Thanks for posting that.

When I was reading your intro, the point I figured you would end up making is something like this:

If you're looking for clean headroom, perhaps tube and SS would be of comparable volume. However, the entire spectrum of clean into clipping is considered "good" on a tube amp, whereas when a SS amp cilps, you're pretty much done with its volume range. Therefore, an 18W tube seems to have more volume/power than a 50W SS.

But then you blew my plan to pieces by saying something else...

So my question to you: is there anything to the stuff I wrote above, or is it just me being completely incorrect?

Not at all Eric. You are on the right track for sure. If we introduce a measurement of distortion into the discussion it should be clearer.

Firstly lets remove "compression" from the equation. I'll come back to it in a sec.

A tube amp producing 50W RMS at 0.1% THD (Total Harmonic Distortion) should sound exactly as loud as a SS amp producing 50W at 0.1% THD.

However, whilst its dead simple to design a SS amp with that kind of performance, it's a lot harder to do so with tubes, so in reality you'd never see a 50W tube amp and a 50W SS amp with the same THD rating.

Side note. Whilst researching my reply here I've decided I want to smack THD (the attenuator people) up side of the head. I was looking for THD, as in -distortion- specs for common tube amps, but all i can find are thousands of mentions of the damn hotplates....grrrrrrr!
I wanted to give you some THD figures for a few Fenders and Marshall's, but it seems they don't list them. I'd assume thats because a. they are enourmous, and b. largely irrelevant because the distortion sounds good.

Anyway, back to what I was saying..

Yes you're correct. Your 18W would be distorting its brains out at full noise and and that tube distortion is interpreted by the ear as an increase in volume as well as an increase in distortion.

There is even the chance that an 18W tube amp could have been rated as (for arguments sake, I have no data on this) 18W @ 1% THD meaning that it'll belt out far more than 18W before it distorts so badly it's no longer musical.

So yes, "clean power" Vs "clean power" should be close to the same.

I hope that makes sense regarding distortion

OK now compression.

Tube amps also "compress" a signal and this is significant also.

I think perhaps the simplest way of explaining it is that where a transistor will "slice" the peaks of a wave (hard clipping) and sound horrible. Tubes "squish" the peaks of a wave down into the available "space" (Space being the maximum amplitude determined by the B+ of the amp).

This "squish" is known as compression and if I've explained it O.K. you should be able to envisage that a compressed signal still carries all the original signal, just distorted somewhat by the "squishing", where a clipped signal just loses all the extra bits above and below the clipping point where the transistors slice it off.

The result to your ears is that the compressed signal sounds louder (and often more musical because of increases harmonic content and apparent sustain).

As Marnold said, the best place to observe this if you don't own a compressor is simply to watch TV.

I think its fair to say most people think the TV stations turn up the volume for ads. I know thats certainly how it -sounds-

In reality though, there are restrictions for that kind of thing. I think the FCC regulates this in the USA actually. What they actually do so sneak past any volume level regulations is compress the guts out of the ads audio.

That increase in volume as a result of highly compressed audio in TV ad's is the same thing your hearing when your ears tell you a tube amp is louder than an equivalent SS amp. (It's also why built in volume limiters don't work well, if at all on TV's)

Does that help?

[Eric***]

Does that help?

Very much so. Thanks for all of the info!

[deeaa*]

Hey Eric,

Cabs are largely a matter of taste I guess.

IMO the best way to go for compromise in big sound and usability is a 2x12" cab, and most preferably one you can use both open and closed, i.e. has a partially removable back panel, so you can choose according to the venue/use. Something like the Framus 2x12", but the Framus isn't exactly the best materials or build - sort of light/flimsy even.

Closed back: best for gigging, and punchy rock - good projection and no spilling of sound everywhere you don't want, plus they always sound much the same despite the room they are in. Basic 4x12" closed is the ONLY cab that can truly deliver the biggest and best rock sounds live IMO especially with more than one guitars playing.

Open back: best for recording and bluesier/softer stuff and reverb use etc. and work arguably the best for single big lead guitars etc. Usually 2x12" works quite well. Downside is the sound can change surprisingly much according to placement/proximity to walls behind etc. and it can be hard to get a really punchy rock sound from 'em, and the wash of the sound can drown other guitars present.

Mixing cabs is always good...a 4x12" with a 2x12" open back on top can sound incredible.

Mind you, one of the best cabs I ever had was a 4x12" with just 2 speakers installed...open at front it sort of had best of both open and closed backs to it, but was a tad big though.

Ported cabs...their problem is the port is tuned to a certain frequency, which means they have to be matched with the amp.

Put a Marshall thru some ported cab and it's possible the frequency the cab is tuned to is way wrong and the low end sounds just damn weird. They usually work best for bass amps and such, which also have compreshensive EQ's - acoustic guitar cabs etc. But I'd not get one for rock guitar.

All you really need for good rock rock guitar sound is one good 12" speaker in a solid enclosure, open or closed is matter of taste.

But for live applications, 2 or 4 is better.

4x10" cabs like the old Marshall Mosfet series cabs can be really nice and tight too, but they won't have the flab-yer-pants power of 4x12"'s.