Tiny head, big body

[tot_Ou_tard]

Is there any reason not to get a larger cab, say 2 x 12, as a partner to a 5 watt tube amph (or head)?

Do big cabs sound good at lower volumes?

Aquiring (;) ) minds want to know.


Actually, I won't be doing the aquiring anytime soon, but I like to be prepared.

[tunghaichuan]

I see this question a lot in the mod forums.

There is no reason at all not to use a large cabinet and a low wattage amp.

Some people think that a higher wattage speaker is harder to drive than a lower wattage speaker, but it just isn't so.

Speakers sensitivity is rated using dB/watt/meter. So a speaker with a rating of 100 will produce 100 deciBels when one watt of power is put into the speaker and measured at one meter. So what counts is how sensitive the speaker is, not how much wattage the speaker is rated for. Most guitar speakers fall in the 97-103 range.

The wattage rating of the speaker is how much wattage can be pushed through the speaker without burning out the voice coil. It has nothing to do with how loud the speaker gets when driven by a certain wattage.

Large speakers sound better than smaller ones, (10" and 12" speakers sound better than 6" and 8" speakers). Multiple speakers sound better than single speakers: 4x12", 2x12", 4x10", 2x10". In fact, a 5W silver face Champ sounds *huge* through a 4x12" cabinet.

The only caveat to using high wattage speakers is that some players like some speaker distortion in their sound. Pushing a 70 watt rated speaker with a 5 watt amp isn't going to get any cone distortion. Pushing a 10 watt rated speaker with a 5 watt amp will.

tung




Is there any reason not to get a larger cab, say 2 x 12, as a partner to a 5 watt tube amph (or head)?

Do big cabs sound good at lower volumes?

Aquiring (;) ) minds want to know.


Actually, I won't be doing the aquiring anytime soon, but I like to be prepared.

[tot_Ou_tard]

Thanks tung! I knew that I could count on you. The reason I was thinking of a 2 x 12 was to be able to use two complementary speakers. The big body was not only a reference to the physical size of the cab, but also the body of the sound produced.

How about impedence. The Fender Champion 600 expects 4 Ohms, as I understand it, it is fine seeing anything above that as well.

Is there any sonic difference if an 8 Ohm or 16 Ohm cab is used instead of a 4 Ohm one?

[tunghaichuan]

Thanks tung! I knew that I could count on you. The reason I was thinking of a 2 x 12 was to be able to use two complementary speakers. The big body was not only a reference to the physical size of the cab, but also the body of the sound produced.


Glad to oblige :)

I feel that multiple speakers spread the sound out over a larger area, and consequently, sound bigger and better.

My BH Little Giant head sounds noticeably better through both of my RSA 1x12" cabs than it does through just one:

http://www.diycustomamps.com/images/BH_stack.jpg




How about impedence. The Fender Champion 600 expects 4 Ohms, as I understand it, it is fine seeing anything above that as well.

Is there any sonic difference if an 8 Ohm or 16 Ohm cab is used instead of a 4 Ohm one?

I personally don't like to mismatch cabinets, IOW, I like to match the amp's impedance to the correct speaker load.

The OT in the Champ 600 is most likely a stock Champ-style 5K-7.5K:4 ohms. If you plug an 8 ohm speaker into amp you get 10k-15k reflected back to the 6V6. If you plug in a 16 ohm speaker you get 20K-30K.

If you wanted to run multiple speaker cabinets with your Champ, I'd suggest replacing the stock OT with this one:

http://www.allenamps.com/parts.php#transformers

Model# TO7V

It is made for the Valve Junior, but should have the same mounting centers as your Champ's stock OT, 2.375", but I'd measure the stock Champ OT just to be sure. I eyeballed the stock OT when I was in GC, and it looks like it has 2.375" mounting centers.

tung

[tot_Ou_tard]

Thanks again tung!

[mrmudcat]

well ill add this :master: :master: :master: :master:

[M29]

Hello,

My dad had a 30 inch Electro Voice woofer that was part of his stereo back in the 1960's. This thing was massive. The magnet must have weighed 20 pounds and the woofer cone was 1/4 inch styrofoam. He wanted to sell it and we wrote EV for some plans to put it in a cabinet for bass guitar. Once we built it, it set around for a while and I used to hook up my clock radio to it. I was shocked at how loud it was. It was very efficient and the clock radio could not have been more then a few watts. I don't know how it did it but it moved that thick 30 inch cone with no problem.

M

[markb]

My last experience of this was plugging a Fender Pro Junior into a 2x12 that was available one show we played some years ago. Wow! The little PJ is loud enough by itself but when you get the tone through a decent sized cab it really opens up.

[Kazz]

One note....16 ohms is really not bigger than 4 ohms...it would technically be smaller....as in more power will come through the line if it is rated at 4 ohms than 16 ohms. For instance...I am getting ready to upgrade the stereo system in the new Dodge Ram Quad Cab I bought.....I have 2 amps to put in place...one for the sub and the other for the 4 door speakers....the speakers are 4 ohms each and the amp will deliver more power to a 2 ohm load...so I am going to wire the speakers together in parallel producing a 2 ohm load which will make the amp produce alot more power across each channel.

[tot_Ou_tard]

One note....16 ohms is really not bigger than 4 ohms...it would technically be smaller....as in more power will come through the line if it is rated at 4 ohms than 16 ohms.
That's why it's called impedance.

It must be related to what tung meant by



The OT in the Champ 600 is most likely a stock Champ-style 5K-7.5K:4 ohms. If you plug an 8 ohm speaker into amp you get 10k-15k reflected back to the 6V6. If you plug in a 16 ohm speaker you get 20K-30K.


What does this mean anyway? 10k - 15k in what units? What is the effect of reflecting back? Loss of volume? Something else?

[tunghaichuan]

What does this mean anyway? 10k - 15k in what units? What is the effect of reflecting back? Loss of volume? Something else?

Basically, an output transformer is an impedance matching device. Vacuum tubes are low current, high voltage, high impedance devices. Speakers are low impedance high current, low voltage, low impedance devices. The OT is an interface between the two. This is accomplished by having two coils of wire in close proximity to "step down" the voltage and step up the current. One coil is called the primary and this hooks up to the tube(s). The other coil is called the secondary and hooks up to the speaker.

A 6V6GT tube in a single ended circuit wants to "see" about 5K-7.5k on the primary of the OT when a speaker is plugged into the secondary. Increasing the speaker impedance on the secondary increases the impedance on the primary.

Generally the lower the reflected primary, the more power and more distortion the amp produces. A higher primary will give less distortion at the expense of less power.

I found the following information on RG Keen's site (http://www.geofex.com/tubeampfaq/taffram.htm):



however... the thing you CAN do to hurt a tube output transformer is to put too high an ohmage load on it. If you open the outputs, the energy that gets stored in the magnetic core has nowhere to go if there is a sudden discontinuity in the drive, and acts like a discharging inductor. This can generate voltage spikes that can punch through the insulation inside the transformer and short the windings. I would not go above double the rated load on any tap.

So you definitely don't want to plug a 16 ohm speaker into a 4 ohm tap.

tung

[tunghaichuan]

One note....16 ohms is really not bigger than 4 ohms...it would technically be smaller....as in more power will come through the line if it is rated at 4 ohms than 16 ohms. For instance...I am getting ready to upgrade the stereo system in the new Dodge Ram Quad Cab I bought.....I have 2 amps to put in place...one for the sub and the other for the 4 door speakers....the speakers are 4 ohms each and the amp will deliver more power to a 2 ohm load...so I am going to wire the speakers together in parallel producing a 2 ohm load which will make the amp produce alot more power across each channel.

This is true of solid state amps. They generally do not have an output transformer as the output of the SS devices goes directly into a speaker. The lower the impedance of the speaker, the more power out you get with an SS amp.

Tube amps have an impedance matching output transformer so all things being equal, a 4 ohm speaker plugged into the 4 ohm tap and a 16 ohm speaker plugged into a 16 ohm tap should produce the same amount of power.

tung

[tot_Ou_tard]

A 6V6GT tube in a single ended circuit wants to "see" about 5K-7.5k on the primary of the OT when a speaker is plugged into the secondary. Increasing the speaker impedance on the secondary increases the impedance on the primary.

Thanks again tung!


Is that 5-7.5 kilovolts, kilo-Ohms, kiloamps, or kilowatts?

That quote from RG keen's site uses the made up term "ohmage".

O, for an homage to current usage!

[tunghaichuan]

Thanks again tung!

Is that 5-7.5 kilovolts, kilo-Ohms, kiloamps, or kilowatts?

That quote from RG keen's site uses the made up term "ohmage".

O, for an homage to current usage!

Sorry, that is 5-7.5 kilo ohms.

Yeah, I noticed the use of "ohmage" too. I find that surprising from RG Keen who is a degreed engineer. I believe he is the chief engineer for Visual Sound pedals.

tung

[tot_Ou_tard]

OK, it all makes sense now. Thanks! :AOK:

Time to get into a little rhythmage & soloage.

[Jipes]

Glad to oblige :)

I feel that multiple speakers spread the sound out over a larger area, and consequently, sound bigger and better.

My BH Little Giant head sounds noticeably better through both of my RSA 1x12" cabs than it does through just one:


tung

That's exactly what I also experienced between my new Custom Vibrolux reissue which had only 2 10' speakers and my Concert amp which has 4 the difference is quite impressive in terms of diffusion I guess you call that Headroom. Both amps have the same power (40W for both)

Jipes