Rewiring the cab

[lapideusvir]

Hi folks,
I have a RE 2x8 cab that loads 4Ohm. This means that the speakers are wired parallel.
The amp I use (ss) delivers 400W on 4Ohm.
So a lot of loudness. I have to be very sensitive on the volume poti, just a tad more it gets soo loud / too loud for my practice room.

I´m thinking about rewiring the Speakers in series. This will lead to a load of 16Ohm.
If in series, the power will be ...100W?

Will this affect the sound of the box?
Would you recommend doing this?

Thanks.

[sgosnell]

It may affect the tone. I would recommend doing it, and seeing whether you like it better. It's easily reversible, so if you don't like it in series you can return it to parallel, no harm no foul.

[Gitterbug]

The lack of replies to your straightforward question reveals what I believe to be a common source of confusion: does connecting two speakers in series reverse the polarity of the second one? The education available on the web is all over the subject. Some people say a speaker only gets + impulses and returns to zero after those. Others say there's a zero position between + and - impulses. With some 800 cabs made, I've never tried connecting two in series. A 4x12" Toob I made for show purposes years ago failed because one of the speakers was mis-wired. The idea was to have two banks of 2x12 (4 Ohm) connected serially for a total of 8 Ohm load. Calling Dr. Nevershouldhavesoldit to the rescue!

[jads57]

Mojo Tone Plug and Play! Then you have multiple options always available!

[Danny W.]

The lack of replies to your straightforward question reveals what I believe to be a common source of confusion: does connecting two speakers in series reverse the polarity of the second one? The education available on the web is all over the subject. Some people say a speaker only gets + impulses and returns to zero after those. Others say there's a zero position between + and - impulses. With some 800 cabs made, I've never tried connecting two in series. A 4x12" Toob I made for show purposes years ago failed because one of the speakers was mis-wired. The idea was to have two banks of 2x12 (4 Ohm) connected serially for a total of 8 Ohm load. Calling Dr. Nevershouldhavesoldit to the rescue!

Hey Marku,

I have a great deal of respect for what you've done, so please take this in the spirit it's intended: what the heck are you babbling about?

Standard wiring for a Marshall-style 4x is 8 ohm drivers wired in series-parallel or parallel-series. It doesn't really matter which, either way gives you an 8-ohm cab and they sound the same. Series get connected + to -, parallel get connected + to +. Two speakers in series can't magically invert the phase of one of them through some as yet to be discovered principle of electronics.

The thing I don't understand is that you've got speakers and you've undoubtedly got a 9v battery lying around. Series-up the speakers, watch the cones as they move when you hook up the battery both ways, mystery solved!

As for the OP's question, he's already gotten a useful answer, but I'm surprised that between the guitar and amp volume controls he can't set a useful volume for home playing. I use an amp rated at 800 watts into a 4-ohm cab, albeit one that's less sensitive than an RE 2 x 8", in a 12' x 12' x 9' room with no problems. Perhaps if he gave us more info about the amp there's another solution we could find.

It is possible that rewiring the cab to series will cause a small change in sound from the change in damping factor.

Danny W.

[Gitterbug]

[QUOTE=Gitterbug;1351172]

Thanks, Danny! I do recognize that phase is a function of time and polarity about plus or minus. Judging by the volumes of web "babble" on the confusion between the two concepts, I'm not in a minority of one.

Here's one of the many web quotes I found:

Polarity is either a positive or negative state, relative to the original waveform. A waveform is of positive polarity until you invert or "flip" the polarity to make it negative, relative to its original state. Since polarity can be flipped, you can control that with a switch. A negative polarity version of a waveform will be a mirror image of its positive polarity counterpart. For those who are science buffs, you might imagine positive versus negative polarity being almost like matter and antimatter. Assuming that everything about two waveforms is the same other than their polarity (time, amplitude, etc.), when you mix them together they cancel each other out and you are left with nothing, [as illustrated below.]

Doesn't that suggest that connecting two speakers in series, i.e. reversing polarity between them, will cause them to cancel each other out?

[aquin43]

Hi folks,
I have a RE 2x8 cab that loads 4Ohm. This means that the speakers are wired parallel.
The amp I use (ss) delivers 400W on 4Ohm.
So a lot of loudness. I have to be very sensitive on the volume poti, just a tad more it gets soo loud / too loud for my practice room.

I´m thinking about rewiring the Speakers in series. This will lead to a load of 16Ohm.
If in series, the power will be ...100W?

Will this affect the sound of the box?
Would you recommend doing this?

Thanks.

Rewiring in series will give a useful 12dB drop in voltage sensitivity and will probably sound OK.

Actual speaker impedances vary widely over the audio frequency range. When speakers are in parallel, their impedances are isolated from one another by the low impedance of the amplifier and each one takes power according to its impedance. When they are placed in series, they share a common current and each speaker produces an output that depends on its actual impedance. Now, the parameters of loudspeakers that affect their impedances are poorly controlled in manufacture. If the two speakers turn out to be identical, they will behave as one and share power equally. If parameters such as the cone mass or compliance differ by 10%, which is not uncommon, then the speakers will interact around the resonant frequency and not share power equally although the sum of their outputs will be very similar in shape to the output of a single speaker.

If this were HiFi I wouldn't do it but for a guitar speaker, it will probably sound perfectly OK.

[Danny W.]

Here's one of the many web quotes I found:

Polarity is either a positive or negative state, relative to the original waveform. A waveform is of positive polarity until you invert or "flip" the polarity to make it negative, relative to its original state. Since polarity can be flipped, you can control that with a switch. A negative polarity version of a waveform will be a mirror image of its positive polarity counterpart. For those who are science buffs, you might imagine positive versus negative polarity being almost like matter and antimatter. Assuming that everything about two waveforms is the same other than their polarity (time, amplitude, etc.), when you mix them together they cancel each other out and you are left with nothing, [as illustrated below.]

Doesn't that suggest that connecting two speakers in series, i.e. reversing polarity between them, will cause them to cancel each other out?

If you connect the + to - you are not reversing the polarity. Just as you want to connect + to + when in parallel. That’s called connecting them in phase.

Danny W.

[Gitterbug]

If you connect the + to - you are not reversing the polarity. Just as you want to connect + to + when in parallel. That’s called connecting them in phase.

Danny W.

So how to reverse polarity? And how did I manage to screw up with the 4x12"? The musicians present said it sounded like out of phase.

[Danny W.]

So how to reverse polarity? And how did I manage to screw up with the 4x12"? The musicians present said it sounded like out of phase.

If you wired it as I said and if the speakers were correctly marked it wouldn't have been out of phase. Without having the cabinet in front of me I can't tell you which was the cause.

If you have a speaker cab with 2 speakers in either series or parallel and it sounds out of phase, simply reverse the connections on one of the speakers. If it now sounds better, the problem is solved. If it sounds worse it wasn't out of phase to begin with. For a 4X cab, could be one or two speakers that need to be reverse-wired--I'd disconnect one pair completely, swap the wiring on one speaker in the remaining pair. When that's in phase, so the same thing with the second pair, then make sure it's still okay when both pairs are wired up. Or hook the cab up to a DC source and make sure the cones all move in the same direction.

I'm not a manufacturer of speaker cabs, but if I were I'd want all of my products to be wired with the same phasing, so that a player could combine them in close proximity without introducing sonic issues, using standard cables. I've had a half dozen RE cabs and a similar number of AI cabs and have worked with them in various combinations problem free.

Danny W.

[lapideusvir]

Hi folks,
I think this will make the trick:

Volume Attenuator | Lazy-Bear

Will try it!

[Gitterbug]

I'm glad the OP found a solution that seems to make better sense than re-wiring. Chapter closed? Not quite. I was so puzzled by Danny W's posts and embarrassed by my apparent lack of knowledge that I did a quick test using two identical SICA speakers laid on the table side by side, facing upwards.

First, polarity. With the speakers wired in parallel (my preference anyway), the two cones, predictably, moved into the same direction when given an impulse from a 9V battery. Forward with +, backward with -. Changing into serial - i.e. connecting + to - on the second speaker, made the cones move in opposite direction. This was my assumption and, if I've understood Danny correctly, against what he says.

Second, tone. I played a few chords through both setups. The difference was remarkable, and not only attributable to different impedances. In parallel, the speakers had a lot more bottom end and character, while in series, the sound was thin and nasal. Indeed, out of phase. It's conceivable that speakers in the nude make the difference more obvious than in an enclosure with much internal ping-pong and criss-crossing frequencies.

I have this all on video, but would need help from someone with more advanced editing and posting skills. Yeah, my son's a video pro but he's on vacation, and so am I again once this text has been fired off.

[Danny W.]

Are you sure you wired them in series and not just in parallel out of phase? Series would be positive from supply to + on speaker #1, - on #1 to + on #2, - on #2 to - on supply:

[Gitterbug]

Thanks for yor patience, Danny. TBH, you're probably right. I'm hopeless with electronics and schematics, but yours is the clearest I've seen. Must follow it the next time at the workshop, i.e. next weekend. Will report my findings.

Cheers,

Markku

EDIT: Danny is right, I was still in parallel mode but out of phase. Finally worked my way through parallel/series wiring of multiple speakers. At 77, never too old to learn. Apologies for the B/S!

[Danny W.]

Glad to help, Marku. You can send a Toob 12J in lieu of my consultation fee.

Danny W.

[JazzNote]

Thanks for yor patience, Danny. TBH, you're probably right. I'm hopeless with electronics and schematics, but yours is the clearest I've seen. Must follow it the next time at the workshop, i.e. next weekend. Will report my findings.

Cheers,

Markku

EDIT: Danny is right, I was still in parallel mode but out of phase. Finally worked my way through parallel/series wiring of multiple speakers. At 77, never too old to learn. Apologies for the B/S!

Markku: As often is the case, missing information leads to difficulties in understanding. The following statement was missing a piece of information, that's why it was hard to understand: series get connected + to -, parallel get connected + to + and - to - . I'm initially a trained electrical engineer and it took me a while to figure out how the logic of the statement works ;-). The same with the statement: If you connect the + to - you are not reversing the polarity if in series.

red = missing info in original posts

[Danny W.]

Markku: As often is the case, missing information leads to difficulties in understanding. The following statement was missing a piece of information, that's why it was hard to understand: series get connected + to -, parallel get connected + to + and - to - . I'm initially a trained electrical engineer and it took me a while to figure out how the logic of the statement works ;-). The same with the statement: If you connect the + to - you are not reversing the polarity if in series.

red = missing info in original posts

I assumed he knew the difference between series & parallel wiring, so was just discussing polarity.

Danny W.

[Gitterbug]

In theory yes, I knew. In practice, I've always built single-speaker cabs with two parallel-wired jacks for an extension cabinet. Always 8 ohm. Connecting separate cabs in series requires a "black box" for the necessary wiring. Never figured out how to do it, because there was no need. Nobody's buying a 4×12 anymore, even if I could make one weighing 40 lbs and portable in four pieces. OTOH, a parallel-wired, 4 ohm twin makes perfect sense, and brings the be(a)st out of your amp. My original post was careless in that some of the B/S was not mine but found over time on various websites, without making the distinction. I hope this discussion has been useful. At least it was for me, whose high-school physics has gathered moss since mid-1960s.