Matching a tube amp with a speaker

Paul Seager · From: Augsburg, Germany

Hi all. I recently acquired a tube amp (DV Mark Gallileo) and I need to buy a cab for use with it. The instruments I'll use include a Rickenbacker console steel and a WBS E9 pedal steel. I play straight C&W and some basic jazz, so I'm after a clean sound. Two questions I guess:

The amp delivers 15 watts and has two outputs of 4 and 8 ohms (presumably the output stays the same for each impedance). Does a tube amp prefer less resistance or does it not matter?

How many watts should the speaker handle? I intended to buy something with a handling of 20 - 30 watts but I notice DV make their cabs with handing of minimum 150 watts. Does it make a difference, e.g., will I get less performance if the speaker can handle far more than the amp will deliver or vice-versa?

\ paul

Tony Prior · From: Charlotte NC

The DV / 150 watt speaker is a NEO, its reasonably good and pretty efficient. I have one in a DV Little Jazz 12 which is a 45 watt rated amp. I also use an Eminence 150 watt rated 15" speaker in an ext cab which I use very often with all sorts of amps, tube and SS. I'm talking a 50 watt Solid State to 60 watt HR Deville and also a Dr Z Maz 38 which is a beast ! It handles it all. ( so far )

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My opinion, a 50 watt rated speaker will probably serve you well. The rating is for bursts, transients, not full blown continuous power. Typically we will see lower rated speakers such as 25 watts in multiple speaker configurations. The Super Reverb is the perfect example, 4 x 10's @ 25 watt ratings.

For me, and I can only speak for me, I use a Fender branded Eminence 12's (the Gold Label) rated at 50 watts in most of my amps and cabs. The 15 watt rated Blues jr that I use very often has the exact same stock Emmi speaker from Fender. As does the 60 watt HR Deville I still own and all of the previous Blues and HR Deluxes. I used them in my Twins as well.

What you will run into is "which speaker do I like tone wise" . Thats where all the opinions will come from. There are serious tone differences from speaker to speaker even with the same amp.

IF it matters, the Fender 50 watt Gold Label branded Emmi 12 leans bright with a very mild mid range profile. Good strong low end. Its very consistent, amp to amp. Thats why I use them, consistency.

Good luck and enjoy that DV, I'm a big fan of DV amps.
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Paul Seager · From: Augsburg, Germany

Thanks Tony. You raise good points. I wish to understand the ground rules of matching amp to speaker (which you answered). The "Tone" subject interests me less because it'll be my ears that decide.

But weight is a factor. I also have a DV Little Jazz combo (6 kg), a Phil Jones bass amp (4 kg); a MarkBass combo (< 10 kg) and a compact Bose PA. I'm a fit 57 year old, I cycle to most gigs in my area and I'm used to packing amps onto a bicycle rack! My instinct is to test a Hughes & Kettner Tubemaster (ported 1x10") because it scores on weight, dimensions and 8 ohms and 30 watts seems to fit the bill. However I know tube amps are different to solid state and produce different transients, hence my questions.

Confusion reigns: I'm told that solid state amps do not like low impedance loads whereas a tube amp prefers them. I'm told that speakers should be close to (or actually less) in handling to the output of a solid state amp which sounds weird but hey, I know nothing!

Tony Prior · From: Charlotte NC

Donny Hinson · From: Glen Burnie, Md. U.S.A.

For sake of simplicity, just use a speaker configuration that matches that of the amp. If the amp calls for a 4 ohm speaker, use a 4 ohm speaker (or two 8 ohm speakers in parallel). If it calls for an 8 ohm speaker, then use an 8 ohm. That lets you ignore the "what impedance speaker a tube amp requires vs. what a solid-state amp requires" deliberation.

You can use a 100 or 150 watt speaker with a 15 watt amp, but it's overkill, usually in both cost and weight. Speakers are rated for their maximum continuous power capability, and amps are rated the same. The thing you should keep in mind, though, is how much power you're using. Someone who uses a 150 watt amp that has a 200 watt speaker will likely almost never be using the maximum capability of either. But someone who uses a 15 watt amp may get a lot closer to using all the power they've got. So for a 15 watt amp, a 25-50 watt speaker would be all that's ever necessary. Speakers rated for high power, aside from being heavy and expensive, usually have thicker cones and heavier voice coil assemblies to handle the power, so they don't respond as well as speakers rated for lower power. (I'm always amazed by the nuance, the sonic detail of smaller, lower power speakers. They really excel at the upper mids and highs.)

One other thing to keep in mind is size. Put plainly, a larger cone speaker moves more air, and that translates to putting out more sound, more audio power. I'm not talking about electrical power, here, I'm talking about audio power. Speakers are terribly inefficient transducers. Therefore, any increase in radiating efficiency (by having a larger cone, or radiating area) can be significant...just as significant as having a speaker with twice the electrical efficiency. Of course, as the cone and its components gets bigger, so does the mass. That can begin to affect the nuance I spoke of earlier.

The speaker cabinet is equally important. A speaker in an open backed cabinet may only put out 1% or 2% of the power that's fed into it. Whereas, a speaker in a properly-sized, closed-back or ported cabinet might be several times as efficient. However, that increased efficiency comes at a price. Speakers usually sound more "airy", bright, and clean when they're in an open-back cabinet. (Everything is a trade-off.) What you have to decide is how much physical size and weight you're willing to deal with. The cabinets are often as heavy, or heavier, than the speaker(s) that are in them.

For a 15-watt amp, I'd probably go with an efficient (95db or better) 8" or 10" speaker in an open cab, but that's just me. Cool

Stephen Cowell · From: Round Rock, Texas, USA

Tube amps are designed to work at an impedance. Often (not for Fenders) the output transformer has several taps to match different impedances (4,8,16).

The rule of thumb for tube amps, especially good ones like Fender, is that it's OK to go a factor of 2 away (e.g. 4 or 16 instead of 8 ). Some amps (big Marshalls) don't like mismatches and can blow stuff up if run mismatched.

Solid-state amps normally are rated for a *minimum* impedance... working the amp full-out below this impedance can overheat the output section, resulting in having it shut-down during a gig... or worse. As the impedance goes up, the power output goes down... so for max output, you want to run at the rated output impedance (normally 4ohms). If you have an efficient speaker that's higher-impedance than a less efficient one (think 8ohm JBL vs. 4ohm Jensen) then you might have more volume from the more efficient one.

You can run a solid-state amp with *no* speaker connected (in most cases)... basically infinite impedance... with no damage. On any tube amp, running with no speaker connected will tend to cause arcing inside, the voltages go way high (the transformer suffers from 'flyback effect'). You can ruin tube sockets or the output transformer running this way... so Leo made his amps with the NORMAL speaker output a shorting jack... if you forget to plug the speaker in, the amp is working into a dead short instead of an open. It will last longer in this mode... but not much! I learned this the hard way, by assuming they were the same... paid for a new OT. SS amps don't like shorts at all... you'll pop stuff quick.
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