Friday, May 28, 2010

Nic Clark Channels Sonny Boy

This is at Erik Boa's blues jam at Q's BBQ in Denver on May 26. Nic Clark on harp. He's 14 years old!

Tuesday, May 11, 2010

How Loud is Your Amp?

You see it all the time when this topic comes up: The chart showing the ratios of speaker surface area. It shows that a 15-inch speaker is 1.5 times larger than a 12-inch speaker, which is 1.5 times larger than a 10-inch speaker, which is 1.5 times larger than an 8-inch speaker. So, will you get 1.5 times more loudness out of your amp with the bigger speaker? In a word, NO.

Total speaker surface area has almost nothing to do with perceived loudness. That chart is meaningless, but it certainly helps perpetuate a common amp myth.

Let’s take for example a typical 4x10 Bassman-style amp. It has 312 square inches of speaker real estate, compared to 113 inches for an amp with a single 12-inch speaker. So, is the 4x10 Bassman nearly 3 times louder than the 1x12? No, not even close.

Remember, it takes ten violins to sound twice as loud as one violin. That is an immutable law of psycho-acoustics and the nature of the human ear.

With the 4x10 Bassman you have 4 speakers sharing the output of a 45-watt amp. Each speaker is “seeing” 11.25 watts. Adding a second sound source (another 10-inch speaker) that carries the same signal does not double the perceived loudness, but makes the sound seem only slightly greater. The Bassman’s four 10-inch speakers each driven by 11.25 watts will have the same total perceived loudness of a single 10-inch speaker driven by the full 45 watts.

Now we will hear owners and makers of 4x10 amps cry, “But the four tens move more air!” Perhaps, but “moving more air” has the same effect on perceived loudness as speaker area. By itself, it has almost no effect.

The proponents of “bigger is always louder” are confusing sound intensity with sound loudness. Sound intensity can be measured by instruments as a linear curve, while sound loudness is perceived by the human ear as a logarithmic curve. (Keep in mind the ten violins.) When you stand in front of your big amp and feel all that air making your pants cuffs flutter, it might impress you but it has almost nothing to do with the audience’s perceived loudness of your amp.

If speaker surface area does not affect perceived loudness, what does? Simply put, the two most important factors are 1) the power you apply to the speaker and 2) the efficiency of the speaker. When the bigger-is-better crowd insists they need a big amp for bigger rooms, they are right only to the extent the bigger amp is more powerful. But a lesser-powered amp with a more efficient single 12-inch speaker can have the same perceived loudness as a typical Bassman-style amp. Better tone, too.

Additionally, the smaller amp is likely to weigh less and cost less. It is axiomatic with vintage-style tube amps that a small amp turned up sounds better than a big amp turned down. And since your amp can be mic’ed through the PA in nearly any gig, the reasons for using a big multi-speaker amp are pretty weak.

Saturday, May 8, 2010

In Defense of the 1x12 Harp Amp

I’ve seen a few remarks online by harp players maligning combo harp amplifiers that have a single 12-inch speaker. They take it as a given that the 1x12 configuration is known to be inferior for blues harp.

WTF are they talking about?

David Barrett has a Museum of Vintage Blues Harmonica Amplifiers at his Harmonica Masterclass website, and the most common configuration of all the amps listed is 1x12.

The list of legendary harp amps with a single 12-inch speaker includes (but is not limited to):

-Ampeg Reverbrocket
-Ampeg Jet
-Fender Tweed Deluxe
-Gibson GA20
-Gibson GA40
-Premier 120
-Silvertone 1432
-Silvertone 1482
-Kendrick Texas Crude

Indeed, the Masco PA amp that Little Walter was believed to have used had two 1x12 cabinets.

The Kendrick Texas Crude has been unfairly maligned by a certain competitor, which may have started this weird canard. I’ve played the Texas Crude and it is a beast: Loud, crunchy, and soulful, and remarkably feedback resistant.

Certain 12-inch speakers are well suited to harp tone. They have a great balance of fat lows and punchy mids, more so than other single speakers. Smaller speakers sound too pointy, and larger speakers sound too woofy. Amps with multiple speakers often cost much more then single-speaker combo amps, and they lose the cohesion of sound that emanates from a single driver. There is a very good reason so many classic harp amps are 1x12: They sing.

When I asked the question on Harp-L last year I got many different answers about the best speaker configuration for a gigging harp amp. Two very well known gigging pros replied with something like, “Just give me a good 1x12 amp.” I agree.

UPDATE: I thought of another great vintage 1x12 harp amp: The Flot-A-Tone amp my friend Al Chesis owns. Two 6L6 power tubes, great tone.