5f2a amp, 5e3 cab: 10" or 12" speaker?

[Sneakers]

Hi all,
I'm working on a 5f2a as a living room practice amp. It's going to be sitting out in the open, so I'm putting it in a homebrew 5e3 cab as I've always found very small cabs to be a little strange looking. I'm also trying to keep my future options open, as I may one day build a real 5e3.

Anyway, I've got some options speaker-wise. I'm most interested in the Weber speakers, and I'm hoping some of you kind souls would give me a recommendation. I generally prefer the blackface tone when playing with a band, but for this I'd like something different: an authentic 50's tone.

We have a relatively small apartment, so I'd rather not have something so efficient that I can't turn it up and get some breakup. I'm open to either a 10" or 12" speaker. I suppose that a speaker that would go well with either a 5f2a or a 5e3 would be a bonus, but I don't know that I'll ever switch it to a 5e3, so I can cross that bridge when I come to it.

I see a lot of recommendations for the 12A125A for the 5e3, but I don't know whether it would also be a good fit for the 5f2a. I also see recommendations for the 10A100T for the 5f2a, but I don't know if it would also be a good fit for the 5e3 cab. Something from the Sig series would be ok too.

[echuta13]

Maybe take a look @ the AlNiCo Sig 12S?

[cminor9]

Funny you should mention that. I just finished a 5F2-a last week. Meanwhile, I built a dummy load for my 5E3 (consists of 3 10w 8 ohm resistors) that I can switch in/out of the speaker circuit. Honestly, the attenuated 5E3 is the exact same volume as the 5F2-a but the 5E3 sounds SO MUCH better. The only thing that the 5F2-a does better than the 5E3 is that deliciously ratty amp-is-going-to-explode sound when it gets pushed really hard. Otherwise, the 5E3 has better cleans and a better dirty sound. Oh, I should mention: the 5E3 is in a slightly oversized cab. It is something like 20"x20"x10" (at the bottom) so it's more like a 5G9 cab.

I put an 8" weber sig alnico in the 5F2-A and a weber blue dog (ceramic magnet) in the 5E3. The weber blue dog is their take on a celestion blue. I liked it MUCH better in the 5E3 than I did the weber 12A150A (which also cost 2x what the blue dog cost). A lot of guys like some kind of a celestion blue in the 5E3 based on what I have read. The weber sig speaker in the 5F2-a sounds OK, but it's kinda thin and fizzy (but true to the original!) But it is an 8" speaker and a relatively cheap one at that. Not trashing weber (obviously I wouldn't keep buying their speakers if I didn't like them) but the 12A150A was an expensive disappointment. There was nothing I liked about it, and it cost me like $200. I could have bought a weber alnico blue dog for that.

If you build a 5E3 cab, a 5E3 amp, and a dummy load attenuator, you'll get the best of all worlds. Obviously, just my opinion. I build the 5F2-a with the intent of giving it to someone as a gift. Had I not built it for that purpose, I would actually have been kinda upset I built it for myself, since the attenuated 5E3 just kills it in every way.

I think the hardest part about building these old amps is that you don't really know what they sound like until you play them. You might really like your 5F2-A. But this is the second amp that I have built now (first being a 6G3) that kinda leaves me wanting. If you go with the 5F2-A I do hope you like it, but when you get around to that 5E3 you might kinda wish you had built it first. As always, YMMV.

This sure is a rambling post I just typed. Hope you can make use of some of this info though.

[cminor9]

Oh, just noticed the bit about not wanting an efficient speaker. Weber doesn't publish sensitivity ratings, but the blue is based on the celestion blue which is a very efficient speaker. IOW, it'll be loud. But, as I said, a few dollars worth of power resistors can quiet down an otherwise loud amp. The 5F2-a, while pretty darn quiet, might be a bit too much for an apartment. To break the amp in last night, I played it during a rehearsal with my band. The drummer had to bring it down a bit, but it could hang with the drums without being totally swamped. It's not going to tear your head off, but it might still be loud. If it's too loud, consider building the dummy load to quiet things down a bit. It works really well.

[Sneakers]

Wow - really great advice... thank you.

So, if I understand how the attenuator works...
When it's switched out, it's just the 8 ohm speaker connected to the OT. When switched in, you have two sets of impedances in series. The first consists of two 8 ohm resistors in parallel (for a total of 4 ohms), and the second consists of an 8 ohm resistor and the 8 ohm speaker (for a total of 4 ohm) in parallel. Altogether, it makes 8 ohms, but the speaker is only seeing half the current?

Would switching a single 8 ohm resistor in series with the speaker produce the same result? It would no longer be matched to the secondary impedance of the OT, but wouldn't the speaker see half the current? Or would that affect the tone?

Either way, I'm really liking this idea. Do you have the switch on the panel or inside the cab?

[Sneakers]

Two other questions:
1) I noticed that the Weber site doesn't have a whole lot of specs. Do you happen to know the BCD of their speakers? I'm working on the baffle and it would be nice to be able to drill the mounting holes without waiting for the speaker to arrive. I assume it takes an 11" hole.
2) Did you use linear or audio pots for the volume / tone on your build? I've seen a schematic that says linear, but it seems like most people use audio...

[cminor9]

Wow - really great advice... thank you.

So, if I understand how the attenuator works...
When it's switched out, it's just the 8 ohm speaker connected to the OT. When switched in, you have two sets of impedances in series. The first consists of two 8 ohm resistors in parallel (for a total of 4 ohms), and the second consists of an 8 ohm resistor and the 8 ohm speaker (for a total of 4 ohm) in parallel. Altogether, it makes 8 ohms, but the speaker is only seeing half the current?

Would switching a single 8 ohm resistor in series with the speaker produce the same result? It would no longer be matched to the secondary impedance of the OT, but wouldn't the speaker see half the current? Or would that affect the tone?

Either way, I'm really liking this idea. Do you have the switch on the panel or inside the cab?

I put the switch inside the cab by the speaker. I just mounted it to the side.

Imagine a 4x12 cab with four 8 ohm speakers. You have two sets of two speakers wired in parallel. Each set is wired up in series for 16 ohms, and then you wire them up in parallel so you are back to 8 ohms. Either setting, you are at about 8 ohms. Now, replace three of those speakers with power resistors. That's it. Each "speaker" is getting about 3 or 4 watts. I have a hot rod deville, so I just look at how the 4x10 cab was wired up. If you are stuck, I'll draw you a picture just like Bruce Collins did for me (I got this idea from him).

I have a heatsink that I snagged from an old computer, but so far those resistors have been ok in terms of heat. They are 10 watts, and on a good day the 5E3 puts about 15 watts. One caveat: this is a new device I slapped into my 5E3 last week. I haven't played it for like four hours on end yet, though I played it for about 30 min the other day and the resistors were OK.

This gives you something that will break up naturally (better than a master vol will IMO) at low volumes, but a 5E3 with a blue dog will get quite loud if you need it. All at the flip of a switch. You'll need a DPDT, BTW.

[cminor9]

Two other questions:
1) I noticed that the Weber site doesn't have a whole lot of specs. Do you happen to know the BCD of their speakers? I'm working on the baffle and it would be nice to be able to drill the mounting holes without waiting for the speaker to arrive. I assume it takes an 11" hole.
2) Did you use linear or audio pots for the volume / tone on your build? I've seen a schematic that says linear, but it seems like most people use audio...

1) I have almost ALWAYS regretted drilling, cutting, etc for parts that have not yet arrived. I would wait for the speaker. I have learned this the hard way more times than I care to think about.
2) For everything I have built it's been audio taper pots. For the 5F2-a it calls for linear. I tried to stay as true to the spec as is possible, so I went for linear. And what do you know? The 5F2-a circuit works great with linear pots.

[Sneakers]

Imagine a 4x12 cab with four 8 ohm speakers. You have two sets of two speakers wired in parallel. Each set is wired up in series for 16 ohms, and then you wire them up in parallel so you are back to 8 ohms. Either setting, you are at about 8 ohms. Now, replace three of those speakers with power resistors. That's it. Each "speaker" is getting about 3 or 4 watts. I have a hot rod deville, so I just look at how the 4x10 cab was wired up. If you are stuck, I'll draw you a picture just like Bruce Collins did for me (I got this idea from him).

Thanks - that's what I imagined. Although, I would like to see a picture to make sure that I have the switch positioned correctly.

[ThermionicScott]

I believe the 5F2a cabinet is roughly the same size as the wide-panel Deluxe cabinet, so I don't think a 12" would be too big for it. That 4 watts gets pretty loud and room-filling when cranked -- I like disconnecting the B+ from the rectifier socket and hooking up 18V worth of batteries when i want to overload it at low volume.

- Scott

[cminor9]

I kept mine pretty true to the original dimensions, it's 16" tall x 18" wide. That means the baffle is just a little over 14" tall. Subtracting an inch for each panel, that gives you just a hair over 12" to play with. While you *could* cram a 12" in there, it might be a bit rough. And then it would depend on how you make your baffle. Also, consider that if you don't line those tubes up just right, and depending on the speaker, you could have a tube/speaker magnet collision. If you're gonna try, I'd make sure you have all the parts in hand to make sure it all fits!

Just out of curiosity, when I built the 5F2 I took some measurements on my 12" weber blue dog just to see... and it would not have fit well at all.

[ThermionicScott]

Just thought I'd add that my 5F2A sounds great with a 10" speaker. I sometimes practice bass through it, and although the amplifier runs out of clean headroom quickly on the lowest notes, the frequency response is there. If that makes sense.

- Scott

[Sneakers]

Well, over the last month I worked some more on my cabinet and considered just building the 5e3. Ultimately, though, I think I'm going to stay with my original plan to build a 5f2a, but in a 5e3 cabinet.

It seems there was some confusion around my orignal question though. I know a 12" will fit in the cab (I'm using a 5e3 cabinet). Rather, what I'm wondering is whether I could find a 8", 10" or 12" speaker for a 5f2a that would give me a dirty roadhouse tone like this:

but would give clean tones that are fuller than the ones you can usually get out of the champ. I love the clean tones here:

but I prefer the breakup of the little champ.

Maybe I'm asking the impossible, but I was hoping that it would be possible to keep the gritty break-up of the champ, but that a 10 or 12" speaker would fill out the clean tones.

I wish Weber would post some sound samples of their speakers, as Jenson and Eminence do.

[cminor9]

glad you got a plan.

Speaker choice is tough. I can tell you I like a weber blue dog in a 5E3. It's a very efficient speaker, so you should get a good amount of volume out of it so that means more clean out of a 5F2a. The tone of that speaker might sound nice in a 5F2a; it absolutely kills in a 5E3. Just know you won't get THAT particular clean out of the 5F2a. The 5E3 has a nice meaty, compressed clean. The 5F2 that I recently built has a nice clean, but it's not *that* one in the video.

[Sneakers]

I do love that clean sound...

So, I know you can't get *that* clean on the 5f2a. So let me ask this: how close can you get to the champ breakup in the video on the 5e3?

I guess what I'm asking is whether there's a bigger difference between the two amps in the clean tones or in the dirt.

. Just know you won't get THAT particular clean out of the 5F2a. The 5E3 has a nice meaty, compressed clean. The 5F2 that I recently built has a nice clean, but it's not *that* one in the video.