Univox project amp renovation

[JMT]

I picked up a '66 Univox Bass Amp recently. Cathode biased 2x6L6, 2x12AU7 and a 12AX7 phase inverter. The single Jensen C15N [8 ohm] got my attention as I've always wanted to have a 15" speaker amp. Of course, when I took delivery the voice coil was locked up! LOL Now that some time has passed it's a little easier to laugh. My tech has updated the electrolytics and improved the treble control. I took it to a gig last week and was amazed by the power and cut with the no name loaner 15" speaker. I've order a Weber 15F150 for it and it's turning into a fun project. I'm going to make a new baffle as I need to move the speaker location an inch or two to clear the power tubes. I was thinking that I might go ahead and cut another baffle board to experiment with another speaker configuration such as:
2x 10
1x10, 2x8
1x10, 1x12
1x12, 2x8
I'm not a tech and I'll need some guidance, especially, on how to match speakers to the 8 ohm amp. This forum is a good place to get some informed opinions. So...fire away!....and thanks in advance!

[spsimmons]

This page seems pretty comprehensive.

Jumbo Sunshade - Speaker Wiring Diagrams

[JMT]

good link. However, I'm looking for opinions on various spkr combinations and how to figure impedance for 3 spkrs.

[arnenym]

I picked up a '66 Univox Bass Amp recently. Cathode biased 2x6L6, 2x12AU7 and a 12AX7 phase inverter. The single Jensen C15N [8 ohm] got my attention as I've always wanted to have a 15" speaker amp. Of course, when I took delivery the voice coil was locked up! LOL Now that some time has passed it's a little easier to laugh. My tech has updated the electrolytics and improved the treble control. I took it to a gig last week and was amazed by the power and cut with the no name loaner 15" speaker. I've order a Weber 15F150 for it and it's turning into a fun project. I'm going to make a new baffle as I need to move the speaker location an inch or two to clear the power tubes. I was thinking that I might go ahead and cut another baffle board to experiment with another speaker configuration such as:
2x 10
1x10, 2x8
1x10, 1x12
1x12, 2x8
I'm not a tech and I'll need some guidance, especially, on how to match speakers to the 8 ohm amp. This forum is a good place to get some informed opinions. So...fire away!....and thanks in advance!

The size of speakers doesn't matter. Its the resistance you should calculate

Series Parallel Speaker Impedance
Series Vs. Parallel Wiring

Search "speaker wiring" on google and you will find the answer

[spsimmons]

What I would add at this point is, I've read/heard that the impedance of the speakers should match. If, for example, you were to mix a 4ohm speaker with an 8ohm and a 16ohm, the 4ohm speaker will hog the current, making it louder than the other two. I've never experimented with that, but it makes logical sense.

My favorite for bass has always been 2x12. (I had a Musicman 2x12 for a while (on loan) that was incredible. Hated to have to give that one back.) I have an 8x8 right now that is almost as good. I always heard that the Carvin Triad (1x12,1x10,1x8 I believe) sounded really good.

So, different combinations can work really well, but with bass cabinets, there tends to be a lot of math involved in matching speakers to cabinets. Good cabinet designs are probably a large part of why the cabinets I sited sound so good.

But, for fun and for the sake of experimenting, I'd say anything goes. If it's fun, why not.

[JMT]

66 Univox Bass Amp FOR HARP

I originally posted on the harp amp forum but after re-reading my original post I realized that I didn't make it clear that the renovation was to be used as a HARP AMP. That's why I was looking opinions from the harp guys about speakers sizes, mixing and matching, impedances, etc.

Sorry if I was misleading any of you!

All the best,
Jay

[arnenym]

What I would add at this point is, I've read/heard that the impedance of the speakers should match. If, for example, you were to mix a 4ohm speaker with an 8ohm and a 16ohm, the 4ohm speaker will hog the current, making it louder than the other two. I've never experimented with that, but it makes logical sense.

My favorite for bass has always been 2x12. (I had a Musicman 2x12 for a while (on loan) that was incredible. Hated to have to give that one back.) I have an 8x8 right now that is almost as good. I always heard that the Carvin Triad (1x12,1x10,1x8 I believe) sounded really good.

So, different combinations can work really well, but with bass cabinets, there tends to be a lot of math involved in matching speakers to cabinets. Good cabinet designs are probably a large part of why the cabinets I sited sound so good.

But, for fun and for the sake of experimenting, I'd say anything goes. If it's fun, why not.

If you have a 50 watt amp and mix 4,8 and 16 ohms in parallell you get a total load of 2,28 ohms.
The 4 ohm speaker take 28,57 Watts
The 8 ohm speaker take 14,29 Watts
The 16 ohm speaker take 7,14 Watts..

IMHO Its not agood idea to mix speaker impedances this way.

[spsimmons]

Yeah, sorry JMT, I'm a bass player at heart, so I see BASS and my thoughts automatically go down that road. Plus- your amp is a '66 and therefore probably open-back, which makes what I was saying about cabinet design off-topic as well.

I really like the calculator arnenym linked to. If you wanted to use three speakers, you might have to also use a resistor to get to 8 ohms.

[spsimmons]

This has got me wondering though about matching the speaker loads.

For example: If you used two 8",8ohm,25W speakers wired in series, you'd have a 16ohm, 50w circuit. If you then wired that parallel to a 12", 16ohm, 50w speaker, you'd have an 8ohm load capable of handling 100w. Right?

Would the 8ohm speakers still suck up more of the current? Or, would they share equally half of the amp's output, with the other half going to the 16ohm speaker?

I don't know.