Speaker Switcher

[minions]

I've been thinking about getting an empty 2x12" amp cabinet and filling it with one Celestion Blue and one Jensen C12K.

Is there a way to add a 3-way switch in order to switch between speakers and maybe even add an LED per setting (Celestion, Both, Jensen) to indicate which one is on?

Thanks.

[newey]

minions-

2 issues right off the bat: Matching the impedances between your amp when it's driving both speakers versus only one of the two, and the power needed to run LED(s).

If your amp needs an 8Ω speaker load and you have 2 speakers, the usual way this is matched is by having each of the 2 speakers be a 16Ω and wiring the 2 in parallel to give an 8Ω overall load. If you switch off one of the 2, your amp is running into a 16Ω load.

A tube amp won't like this at all; a SS amp will probably tolerate it, but there would be a drop in power when switching to one speaker, making for an annoying drop in volume if you switch in mid-riff.

The alternative of using 2 4Ω speakers and wiring them in series to give 8Ω together is worse, since running one alone gives only 4&Omega, which may damage even a SS amp.

About the only way I see out of this problem is to run each speaker as a separate channel of a stereo setup, using either a 2-channel amp or 2 separate amps. You would then switch off one whole channel to get a single speaker, one or the other.

As far as the LEDs are concerned, you'll need a battery of some sort to power them, and the battery circuit for the LEDs will need to be isolated from the speaker signal to avoid adding noise to the speaker signal. This can all be done, but seems like a lot of foofaral just to see an LED light up.

[JohnH]

Yes, but you won't go switching the speakers while the amp is on will you? Please say no, (unless sumgai disagrees). Given that these are nice speakers, I'm assuming a nice tube anp will be driving them, and such switching under power woukl be bad indeed.

Having one speaker acting passively while only jhe other is driven will affect the tone of the driven speaker, compared to it being in its own cab. So you might want to have a central divider so both cab halves are seperate.

John

[minions]

Haha ok then, no speaker switch. But is there a problem with combining these two speakers, as long as their impedances are the same?

[ux4484]

We actually discussed this with the Gai and ChrisK ages ago (though not with LED's).
The one speaker or the other (individually) could be done with two 1/4 jacks w/switch (one disconnects the other when jacked in): The two together is the problem. You'd have to add a third jack to a DPDT switch to bypass the individual jacks and switch to the combined wiring, I believe one of them came up with going parallel adding a 4 ohm load in series to keep the impedance at 8 ohms. In addition you'd have a dummy load on the off position of the switch so a tube lamp would not go unloaded if you jacked it when it was in the off position.
If you you added a wall-wart and a relay, you could have power isolation and indicators, but since you have three jacks and a switch it's kind of a moot point.

*update* You'd still have the possibility of unloading the amp using the individual speaker jacks accidentally when the combined switch was "on" which is why I recall the the idea as scrapped as non-practical.

[minions]

Jan 22, 2010 11:19:30 GMT -5 ux4484 said:

The two together is the problem.

Wait, just concerning the switch, or anytime.

I realize my whole switch idea is way to complex to lose any sleep over, so there's no point.

But I still want to use a Celestion and and Jensen together in the same cab with the same head. Is this a problem?

Thanks.

[JohnH]

Its OK to mix them if they are the same impedance, though Im not familar enough to know how they might sound. You can wire them in series or parallel, depending an whether you want 2x the impedance or 1/2 x that of one speaker. The total power rating is 2x that of he lowest powered speaker. I think Celestion Blues are only 15W, so the whole cab will be 30W - youll have to be careful unless you are using just a small amp.

John

[stevo58]

You should also check the sensitivity of the two speakers. It won't hurt anything, but if one speaker has a higher sensitivity than the other you will have a volume difference. A blue is, iirc, 100db/w/m, and a C12K is 99.1db/w/m so with those two you won't have much of an issue. 3db would be too much though. The apparent loudness could be affected by the frequency response of the speakers, though.

As far as power handling, rule of thumb is it will be twice the power handling of the weaker speaker, in this case, the blue, so 2x15 =30 watts.

steven

[minions]

Jan 22, 2010 16:46:46 GMT -5 stevo58 said:

As far as power handling, rule of thumb is it will be twice the power handling of the weaker speaker, in this case, the blue, so 2x15 =30 watts.

When you say power handling, you mean the wattage of the amp, right?

The amp I have in mind is 25 watts, and has a switch to select 5W, 15W, and 25W. That should be fine, right?

[newey]

Should be fine with a 25 watt amp, unless using the 15 watt Blue by itself is still part of the plan here.

I had forgotten the idea of using a resistive load to equalize impedances.

A while back, JohnH and I exchanged several PMs on the subject of a "newey-proof" switched speaker jack to my SS Fender, such that the internal 8Ω speaker was on, by itself, unless a plug was inserted into the external speaker jack, in which case the internal speaker was in series with an 8Ω external cab to give 16Ω, suitable with a SS amp. JohnH provided a diagram, which I posted around here somewhere, if I can find it . . .

[minions]

Oh okay thanks .

I know this is kind of off topic but it relates to my first post.

I've been looking at the Weber counterparts of the Celestion Blue and the Jensen C12Q (Alnico Blue Dog and Ceramic 12F100T) which are both the same wattage and together are about $100 cheaper.

Are these Weber speakers as good as the Celestion and Jensen they replace, or am I better off going with the originals?

Thanks.

[stevo58]

Webers are excellent speakers and you can't go wrong with them. If they are 'as good' is really up to your ears.

Another thing you should be aware of is that an amp can peak at roughly twice it's rated power, so you really want 50 watts or more power handling for a 25 watt amp especially if you crank it often.


steven

[minions]

Jan 23, 2010 15:18:16 GMT -5 stevo58 said:

Another thing you should be aware of is that an amp can peak at roughly twice it's rated power, so you really want 50 watts or more power handling for a 25 watt amp especially if you crank it often.

Oh okay so the 100W Jensen would be a better idea?

[stevo58]

For a 25 -watt amp, a pair of 25 -watt speakers would be fine. Most Webers can be ordered with the power handling you want.

If you use a high-power speaker with a low-power amp, you should also consider that the speaker will never really be working hard. This may or may not be what you want, depending on the music you play. For example, in my (12-watt) tweed deluxe clone, I have a (Italian) Jensen C12K, which hardly even notices it is being used. It's really overkill for that amp, but I didn't want any speaker distortion in this case. It took ages to break it in. If I had put a 15-watt speaker in there, it would have been working hard and distorting, which could be what you want, but wasn't what I wanted in that amp. So I put the C12K in there, which gives me just what I want.

The thing about speakers is that they have more influence on the tone of an amp than anything else, more than the tubes or any electronic components. There's a reason why Eminence offers so many speakers in its (very good) Patriot and Red Coat lines.

I'll go out on a limb and make a suggestion. If I were to do a 2x12 cab (and I probably will soon) I would do something similar to what you suggest - a Celestion-style Alnico, and a Jensen-style ceramic. Probably both from Weber. I'd choose ~50W handling per speaker and try to match the efficiencies as close as possible. That would pretty much cover everything.

just my 2 cents worth.

steven

[minions]

Jan 24, 2010 10:12:58 GMT -5 stevo58 said:

There's a reason why Eminence offers so many speakers in its (very good) Patriot and Red Coat lines.

I'll go out on a limb and make a suggestion. If I were to do a 2x12 cab (and I probably will soon) I would do something similar to what you suggest - a Celestion-style Alnico, and a Jensen-style ceramic. Probably both from Weber. I'd choose ~50W handling per speaker and try to match the efficiencies as close as possible. That would pretty much cover everything.

Thanks for this. I was looking at the Webers, and it looks like a 50W 12F150 would be the best bet for the Jensen-like one. I think I'd go with a 50W 12F150 and a 30W Blue Dog because I want the more crunchy tone from it. I'm also looking at Eminence speakers.

Tonally, what is the difference between series and parallel speakers? Is series just a darker tone?

[stevo58]

No, it's just a way to hook them up. There are no 'series' or 'parallel' speakers.

If you hook two 8 ohm speakers in series, you get 16 ohms. If you hook them up in parallel, you get 4 ohms. People with extremely good ears can hear a difference, maybe.

The impedence of the speaker(s) gets reflected back to the power tubes through the output transformer. The transformer 'transforms' the impedance from 8 ohms (or whatever) to something that the power tubes want to see, which is somewhere between 2000 and 10000 ohms, depending on a lot of things. This is the range the tubes work 'best' at, depending on the tubes used, how many tubes, and what your definition of 'best' is - it's different for guitar than it is for hi-fi.

But there is quite a tolerance. So for example, a Fender combo amp - let's say a Deluxe Reverb - has a single 8-ohm speaker. The extension speaker jack is just hooked up in parallel, so when you are using an extension speaker, you are only presenting 4 ohms to the output transformer. Most Fenders take this without blinking an eye.

This is probably more than you want to know. You've probably figured out by now I am an amp freak.

steven

[minions]

Yeah, that's great. So it's really only to change the overall impedance, not the tone.

Thanks.

[stevo58]

Right. Pick the speaker impedance and the way you hook them up so that they match the amp.

What kind of amp are we talking about here?

[sydsbluesky]

It may be a moot point, but when I built a cab to mate with my 5 watt blackstar I went with a 65 watt Jenson.

It has more headroom than a hobbit in Grand Central.

[stevo58]

That's right, and that's similar to what I did with my Tweed Deluxe. But you may be more of a Marshall-type guy, then you want those speakers working hard and just hanging on.

[minions]

Jan 24, 2010 15:28:39 GMT -5 stevo58 said:

Right. Pick the speaker impedance and the way you hook them up so that they match the amp.

Yep.

Jan 24, 2010 15:28:39 GMT -5 stevo58 said:

What kind of amp are we talking about here?

I'm thinking a Mesa Boogie TransAtlantic. It's new and sounds and even looks great. There's a demo here.

Jan 24, 2010 15:44:33 GMT -5 sydsbluesky said:

It has more headroom than a hobbit in Grand Central.

Haha nice. I like the metaphor.

[sydsbluesky]

Jan 24, 2010 15:58:03 GMT -5 stevo58 said:

That's right, and that's similar to what I did with my Tweed Deluxe. But you may be more of a Marshall-type guy, then you want those speakers working hard and just hanging on.

Mmmm Vox AC30...

Those Celestion blues seem to get put into very difficult situations and manage very well. I think they're 20ish peak according to the site.

They make another speaker... heritage something or another... with higher wattage and lower cost... It's worth it to poke around on the Celestion site for a bit, at any rate.

Heritage 30? I think it's a 25 watt speaker for some reason. I could be wrong.

I wouldn't write off the lower wattage speakers so easily. Have you rocked out with A Vox AC30?

Weeeellll My frame of mind when it came down to speaker wattage selection was that I wanted somethin that would stay clean until I told it to be dirty. (every guy's dream, right?)

I use pedals for my OD, so I wanted that little tube amp to be as clean as possible until I stomped my foot. If you're looking for that nice "tube" break up, then the speakers are going to bring a little of their own break up to the table when pushed hard. Also, with pedals one must be quite careful not to overdo it... anything with a master volume can be potentially harmful, I'd imagine... Maybe there's some electrical crap about the amp's power section or something keeping that from happening - I'm not the one to ask about that stuff, - but I know I can get a hell of a lot more volume out of my 5 watt head when I have my pedals going in front of it. I'd hate to stomp that bad boy and send that madness through a wattage matched cab.

[stevo58]

Wow, I hadn't seen that Mesa before. First one that ever interested me. Cool little amp!

steven

[sydsbluesky]

I'm with ya on that, Steve.

Too bad it has a full sized Mesa price tag, eh?

EDIT: Then again, the price per watt is about half that of my Blackstar... I guess it's fair.