choosing a cab for a small full tube amp: power vs sensitivity

[gtirard]

Hi,

I'm confused…

In the world of class D amps, it's easy to match cabs and amps: most amps are 450W @8Ohms and 800W @4Ohms, you can pair them with a 112 cab (400W @8Ohms) or a 212 cab (800W @4Ohms).

But when you use a small full-tube amp, say 50W or 100W, how does it work?
- In one hand, it seems to be ridiculous to use a 400W or 800W cab with a 50W or 100W head.
- But on the other hand, the sensitivity of a 212 cab is higher than that of a 112 (let's say 97dB/1W/1M for a 112 and 100dB/1W/1M for a 212), so the same 50W or 100W full tube head should sound much louder with a 212 than a 112, in real life? Twice louder?

 

[JimChjones]

In one hand, it seems to be ridiculous to use a 400W or 800W cab with a 50W or 100W head.

Its not ridiculous at all. There are lots of good reasons why having plenty of spare speaker capacity is a good thing, and more speaker area gives you extra volume far more readily than more watts do.

 

[Redbrangus]

If you're using a low power amp, it's pointless to be concerned about the maximum power ratings -- it's not as if you're leaving some unused capacity on the table. But you are right about being concerned about the sensitivity -- that's the number that's important to you.

Yes, a 212 cab has a sensitivity rating that is 3dB higher than a 112 cab with the same driver. Twice the number of drivers = 3dB increase in SPL. That's noticeably louder, but not twice as loud. Twice the apparent loudness is a 10dB increase.

 

[ThisBass]

There are lots of good reasons having NOT plenty of spare speaker capacity with a low wattage tube head.

Very often rather low wattage loudspeakers show a noticable higher SPL versus high power loudspeakers.

The difference isn't almost always too much (about 2..3dB difference) but, with a low wattage amplifier 50..100 Watt it may be a noticable difference if the cab shows a 2..3dB higher SPL versus a high power cab

 

[Freightshaker]

Tube amp watt ratings are usually listed as cleanish watts. Many tube amps can produce short bursts at double the clean rate. I personally use extra cab.

 

[basscooker]

Yeah, you aren't leaving money on the table using high powered speakers and lowish powered amps.

Remember that with bass signals, you're far more likely to over-excurse speakers than burn them out with power. That being said, higher powered speakers will as well have higher Xmax, generally. Higher Xmax gives a lower powered amp room to really shine down low, as compared to a less robust speaker neatly matched to a low powered amp.

In the guitar world lots of players want that "speaker breakup". In the bass world, that "breakup" is often the sound of a cone about to leave its basket.

No problem what so ever having a cab capable of handling many times what the amp is capable of putting out. That's just built-in gear insurance, IMHO.

 

[rodl2005]

Yeah, I often use my NV215 (750w ?) Iwith a 100w V4B. Secure that the cab will take all the amp has... and more

 

[abarson]

Keep in mind that on an amp, the power rating is how much signal strength can be delivered to a specific speaker load.
The power rating on a cabinet is how much signal strength it can receive before destruction.