Any inherent advantage to parallel vs series-parallel speaker wiring?

[Michael Smith]

I think I've finally settled on the speaker cabinet I will be building next. It will be a 4 x 10" (guitar not bass) cabinet based on the dimensions of a Super Reverb. I will use it exclusively with 4ohm amplifiers. So my choices are to buy four 16 ohm speakers and wire them in parallel, or four 4 ohm speakers wired in series-parallel. I am looking at four Jensen Alnico's or a combination of 2 alnico's and 2 ceramics (possibly WGS). I haven't decided on open back or closed back, but I will probably try it both ways before permanently installing a jack.

Is there anything else I should consider? The amps I will be using will be 50 to 60 watts RMS output.

[Offshore Angler]

Answer is, it depends. Wiring in parallel vs series changes the inductance and resistance of the speaker circuit. Without getting too geeky here and going into Thevinins and the response of LRC circuits- the inductance and resistance are important to the frequency response of the speaker circuit. You may find the "sweet spot" of the frequency response of the cabinet shifted one way or another. Or you may not. It all depends.

Chuck

[Michael Smith]

Answer is, it depends. Wiring in parallel vs series changes the inductance and resistance of the speaker circuit. Without getting too geeky here and going into Thevinins and the response of LRC circuits- the inductance and resistance are important to the frequency response of the speaker circuit. You may find the "sweet spot" of the frequency response of the cabinet shifted one way or another. Or you may not. It all depends.

Chuck

Thanks Chuck, I figured it would not be a simple answer. After looking closer at the Jensen P10R and P10Q speakers, the P10Q is only available in 8 or 16 ohms. The Q's have a 1.25 inch voice coil vs the lower power handling capability of the P's with a 1.00 inch voice coil, available in 4, 8 or 16 ohms. So if I wanted to go with four speakers wired in series-parallel, I would be limited to the P's.

What do you think of the idea of using two alnico's and two ceramics?

I don't really need to build any more cabinets, but after writing a substantial check to the IRS today, I figured why not spend my money on something I would enjoy building and tinkering with.

[phantomman]

I don't really need to build any more cabinets, but after writing a substantial check to the IRS today, I figured why not spend my money on something I would enjoy building and tinkering with.

LOL

I'll be dropping off all my documents at my accountant on Wednesday and dreading what he comes up with.

[Michael Smith]

I really like the sound of these CTS Alnico's but they are over 50 years old. I would like to find modern comparable speakers, but I don't know the voice coil size of the CTS, nor do I know the power rating. Some have suggested anywhere from 15 to 30 Watts RMS. Perhaps Weber 10A125's are comparable? Or Jensen P10R?

[phantomman]

I really like the sound of these CTS Alnico's but they are over 50 years old.

So what?!?!?

You won't find a sweeter sounding 10-inch speaker anywhere.

I have some original-cone Jensens from the early '60s that sound absolutely heavenly.

But if you're insistent on replacing those CTS alnico's I'll be happy to provide them with a new home.

[Michael Smith]

So what?!?!?

You won't find a sweeter sounding 10-inch speaker anywhere.

I have some original-cone Jensens from the early '60s that sound absolutely heavenly.

But if you're insistent on replacing those CTS alnico's I'll be happy to provide them with a new home.

Lol, you misunderstood. I am planning to build a new cabinet to sound as much as possible like the 50 year old CTS alnicos in my Super Reverb. The CTS's will remain in the Super Reverb. The new cabinet will be used in conjunction with other amps. ('68 Bassman, my modified Super Twin Reverb-now 60 Watts RMS, Vibro Champ, Sovtek Tube Midget). Basically all of my 4ohm amps

But I'm finding it hard to determine what the specs of those CTS's are (voice coil size, power handling capability).

[phantomman]

One-inch coils, ribbed cone, 25-watt power rating.

[Michael Smith]

One-inch coils, ribbed cone, 25-watt power rating.

Thanks, it looks like the Jensen P10R is a pretty close replica of the old CTS (based on specs at least). Do you have any thoughts on populating my cabinet with two P10R's and two C10Q's? (the C10R's are only available in 8ohms)

[phantomman]

Any ten-inch ceramic speaker will sound brighter than its alnico equivalent. You may find the mix-and-match sound to your liking, perhaps not. Only a field test can provide the audible data.

[Offshore Angler]

A lot of people get all gooey over magnet material but have probably never heard of remanence or seen a B-r curve for a magnet. The magnets are part of the equation, but so are the coils and the cone construction. Are the cones doped or not, etc. When you find a speaker that makes your socks go up and down, especially an older one, you just need to accept it as unique, and that its personal history makes it what it is. One that's from Louisianna for 40 years is going to sound different than one that's been in Arizona or Wisconsin.

Alnico magnets lose strength over time depending on a lot of different factors, both electromagnetic effects and environmental conditions. So again, just because you like one alnico speaker doesn't mean the next one will sound the same.

After 50 years of this stuff I've learned one golden rule for gear:

"If you like it buy it." Building something with the end goal of it sounding exactly the way you want it to is a fools errand. You may build it and it may sound great, but it will be unique. Take Strats for example. Have you ever found two that play and sound exactly the same?

Chuck

[Michael Smith]

I understand Chuck, nothing I build today is going to sound just like the speakers in my 1969 Super Reverb. What I build may sound similar, or better or worse.

As I finalize my decision on which speakers to buy, I've come up with another idea. Install a double pole, single throw switch connected to the input jack that will send signal to 2 of the speakers. The other 2 speakers will receive signal directly from the jack. When the switch is "off" the cabinet will be using 2 speakers in parallel (8 ohm load). When the switch is "on" all 4 speakers will be used in parallel (4 ohm load).

[DanTheBluesMan]

I understand Chuck, nothing I build today is going to sound just like the speakers in my 1969 Super Reverb. What I build may sound similar, or better or worse.

As I finalize my decision on which speakers to buy, I've come up with another idea. Install a double pole, single throw switch connected to the input jack that will send signal to 2 of the speakers. The other 2 speakers will receive signal directly from the jack. When the switch is "off" the cabinet will be using 2 speakers in parallel (8 ohm load). When the switch is "on" all 4 speakers will be used in parallel (4 ohm load).

I like that idea

[Michael Smith]

I like that idea

Thanks Dan, I have a couple of 8 ohms amps that I would like to try with my proposed alinco cabinet. A 1977 Deluxe Reverb and a Carvin Vintage 16. I will order the speakers tomorrow.

[Offshore Angler]

I understand Chuck, nothing I build today is going to sound just like the speakers in my 1969 Super Reverb. What I build may sound similar, or better or worse.

As I finalize my decision on which speakers to buy, I've come up with another idea. Install a double pole, single throw switch connected to the input jack that will send signal to 2 of the speakers. The other 2 speakers will receive signal directly from the jack. When the switch is "off" the cabinet will be using 2 speakers in parallel (8 ohm load). When the switch is "on" all 4 speakers will be used in parallel (4 ohm load).

Just remember, when the impedance goes down, the current goes up, sometimes with devastating consequences to the output transformer. You aways want to make sure you match the cab impedance with the amp output requirements.

[Michael Smith]

Just remember, when the impedance goes down, the current goes up, sometimes with devastating consequences to the output transformer. You aways want to make sure you match the cab impedance with the amp output requirements.

Yes, I always match the speaker impedance to the output transformer's requirements. When I use the switch to take 2 of the speakers out of the circuit, it will be for use with 8 ohm amps (Deluxe Reverb & Carvin Vintage 16).

I placed my order for 4 Weber 10A125 16 ohm speakers this afternoon. I like the fact that they are built in the US. I may have to wait a little longer than buying from someone with speakers in stock, but they don't start building them until the order is placed. They also allow you to specify the amount of doping on the surround. I selected light doping, since I don't play a lot of high gain distorted stuff.

Now I need some 3/4 inch plywood for the cabinet. I'll probably use 1/2 MDF for the baffle and pine strips for the cleats to hold the baffle and back on.

[Bill Moore]

I know finger joints were always the preferred cab building method, but I have been having great luck with biscuits. Too easy to do, and strong as hell!

[Michael Smith]

I know finger joints were always the preferred cab building method, but I have been having great luck with biscuits. Too easy to do, and strong as hell!

I could probably make a jig for my table saw to do finger joints, but I don't have a dado blade, and the saw is not that great anyway. I will probably do butt joints, and then reinforce with glued in strips of 3/4 inch pine where the 2 boards meet. That would make for a lot of glue surface, and I have had good results in the past. I don't anticipate my new cabinet will ever leave my studio.

I'm thinking the top and bottom of the rear panel will be permanently attached. I will cut rabbets in each panel facing the rear, so a rabbeted middle panel can be inserted if a closed back cabinet sounds better.