KVR Audio

Van_Mocen · Post by **Van_Mocen** » Mon Dec 17, 2007 12:19 am

hey there,
i was just looking at the re-issue of the fender champion 600 and happened to mention it to a friend. we were saying how 5 watts may not sound very attractive but it's well worth as the amp has an incredible tone and its price is really cheap. I then said ' well you can always connect it to an external speaker' and this is where im not sure weather im right or wrong. the amp has 5 watts and 4ohm. if I connect it to an external speaker, apart from the impedence matching thing ( which im not very familiar with, actually ), can i get an higher output ? in other words, if this 5 watt amp has an external cabinet, say, a 200watts marshall connected to it.. do i get a higher output overall ? or does it stay it the same since the power amp in the fender amp is 5watts ? Thanx in advance for your time. cheers !

Hink · Post by **Hink** » Mon Dec 17, 2007 12:36 am

if it's 5 watts at 4ohms I doubt you'll get much more volume out it, unless of course you have a 2ohm speaker

nuffink · Post by **nuffink** » Mon Dec 17, 2007 12:45 am

Van_Mocen wrote:hey there,
i was just looking at the re-issue of the fender champion 600 and happened to mention it to a friend. we were saying how 5 watts may not sound very attractive but it's well worth as the amp has an incredible tone and its price is really cheap. I then said ' well you can always connect it to an external speaker' and this is where im not sure weather im right or wrong. the amp has 5 watts and 4ohm. if I connect it to an external speaker, apart from the impedence matching thing ( which im not very familiar with, actually ), can i get an higher output ? in other words, if this 5 watt amp has an external cabinet, say, a 200watts marshall connected to it.. do i get a higher output overall ? or does it stay it the same since the power amp in the fender amp is 5watts ? Thanx in advance for your time. cheers !

Volume (loudness) isn't measured in watts it's measured in decibels.
Loudspeakers have an efficiency measured in decibels per watt. For a guitar loudspeaker this is typically in the range 95db per Watt to 105dB per Watt. If you want more volume from the same amp, get a more efficient speaker.

The rated power (your 200 watt marshall cab) is the maximum power the speaker can take. It has nothing to do with its efficiency.

p.s. a 10dB increase is subjectively twice as loud. Doubling the wattage of an amp increases the maximum output by 3dB. Doubling the number of (identical) drivers adds 6dB.

Your 5 watt amp will drive a high efficiency loudspeaker (105dB/W) to >112 decibels. This is pretty loud.

Hanglow · Post by **Hanglow** » Mon Dec 17, 2007 12:49 am

To go twice as loud, you roughly need 10X the power. So a 5w amp is only 1/2 loud as a 50w amp, everything else being the same. The speaker in the 600 is a pish little 6" one that I imagine is not very sensitive, this limits thge volume a lot. So if you connect that bad boy up to a nice 4X12 it will indeed sound a lot louder, although you are still limited by other aspects of it, like what is probably a substandard OT so the bass response will be lacking. However, it will be a lot louder.

With regards to the impedance matching, it is advisable to got with matching impedance. Tube amps can die if they have an open load (no speaker attached). However, I wouldn't have a problem with attaching an 8Ohm or even 16ohm speaker/cab to a 4ohm output. You might not like the sound though.

Hanglow · Post by **Hanglow** » Mon Dec 17, 2007 12:50 am

Damn you quicker repliers. Damn you all.

Van_Mocen · Post by **Van_Mocen** » Mon Dec 17, 2007 1:10 am

well, i say, bless you quick repliers

anyway , i knew about volume being measured in dB, i just didn't the get. thanx a lot guys, very helpful indeed !

Van_Mocen · Post by **Van_Mocen** » Mon Dec 17, 2007 1:23 am

so let me see if I got this straight... i can use an eternal speaker with 'my' fender champion 600 amp... there will be some limitations regarding tone perhaps ? but it'll get louder. as to the db per watt. but exactly do you mean by getting a more efficient speaker ? cheers !

nuffink · Post by **nuffink** » Mon Dec 17, 2007 1:27 am

Van_Mocen wrote:so let me see if I got this straight... i can use an eternal speaker with 'my' fender champion 600 amp... there will be some limitations regarding tone perhaps ? but it'll get louder. as to the db per watt. but exactly do you mean by getting a more efficient speaker ? cheers !

Efficiency is how loud the speaker will go (in decibels) for 1 watt of input from the amp. Hence it's measured in decibels per watt (often shortened to dB/W).

C00kie · Post by **C00kie** » Mon Dec 17, 2007 10:07 am

I'd guess Fender has already put in a darn efficient speaker in their amp. So using another speaker cabinet would alter the tone (more bass) but probably not be any louder.

Want louder? Get a frigging big amp like the big boys do.

Hanglow · Post by **Hanglow** » Mon Dec 17, 2007 12:47 pm

I couldn't find the specs on the Fender speaker, but I would imagine it is around 92 dB/w. more sensitive speakers like your average 12" Jensen Mods are around 98db/w. Plus they have a better low end frequency response, obviously as they are bigger so they can push more air.

The difference between my vj clone played through a generic 8" speaker and a 12" G12L with a sensitivity of 95dB/w (not particularly sensitive/loud) is pretty big.

I would say if you want a "loud" cabinet then check out the specs of the speakers within, and make sure they are at least 100dB/W.

pgvpgv333 · Post by **pgvpgv333** » Mon Dec 17, 2007 1:07 pm

May I ask one question?
Can I ruine a amp if I use a 16 ohm speaker, if it is made for a 4 or 8 ohm? Hope you dont mind asking here.

Hanglow · Post by **Hanglow** » Mon Dec 17, 2007 1:12 pm

Probably not, but I think you will sacrifice some headroom. Best to match the impedance

nuffink · Post by **nuffink** » Mon Dec 17, 2007 1:15 pm

pgvpgv333 wrote:May I ask one question?
Can I ruine a amp if I use a 16 ohm speaker, if it is made for a 4 or 8 ohm? Hope you dont mind asking here.

You can only damage a transistor amp by driving a speaker with too low an impedence. In reality it's difficult to find speakers with an impedence below 4 ohms so this shouldn't be a problem.

Valve (tube for you yanks) amps are slightly more problematic. They can be damaged by driving a high impedence load such as an open circuit (infinite impedence or no speaker attached).

Both types will usually have protection circuits to prevent any damage, but you can't guarantee it.

mauseoleum · Post by **mauseoleum** » Mon Dec 17, 2007 1:58 pm

Re: impendance matching (I assume this is a small tube amp, otherwise ignore - I'm not familiar with that particular amp and didn't look it up on the internet)

A) Tube power amps with output transformer in general want the load to be present, in other words the amp wants to be connected to speaker when it's active. In other words, don't power-on the amp if your speaker is disconnected.

B) Naturally it's best to wire it to 4OHM speaker if that's it's nominal output impendance. For i.e. 8OHM output, it would need to have a special terminal on the output transformer (higher impendance winding) in order for impendances to match (maybe via an impendance selector on the amp). Mismatching a practice 5W amp woudn't have such drastic consequences as f.e. some muscular bass amp otoh.

C00kie · Post by **C00kie** » Mon Dec 17, 2007 2:49 pm

If you hook up a 16 Ohm cabinet to an amp that expects 4 Ohms, it will be four times less loud (given that the efficiency of both are the same)

NB: the main reason that small amps can be so loud is BECAUSE of the tiny speaker. It takes less energy to produce high levels of higher frequencies than of lower frequencies.

NB2: Refreshing to see the old-fashionned loudness-war over here... Takes me back to the days I was in a school band, and every one wanted to play the loudest.

Impedence and Connecting external speakers in guitar amp...