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Possibly stupid question about amps and cabs

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Re: Possibly stupid question about amps and cabs

Postby ef37a » Sun Sep 06, 2020 12:52 pm

"In the plug" Sam? I was meaning one of these...

https://www.cricklewoodelectronics.com/ ... GYQAvD_BwE

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Re: Possibly stupid question about amps and cabs

Postby Sam Spoons » Sun Sep 06, 2020 1:59 pm

Sorry Dave, brainfart, obviously knew that :blush:
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Re: Possibly stupid question about amps and cabs

Postby SecretSam » Sun Sep 06, 2020 2:16 pm

Thanks Dave and Lord Spoons.

That sounds like a good way to remove worry.

And I just remembered that I have a couple of high-wattage bass cabs lying around: an old 4x10 and a spare SWR 2x10 with tweeter. Both have had 350w heads attached, and haven't yet ripped themselves to pieces (unlike a previous Trace Elliott rated at 250w, which was doing fine until it had to compete with a ten piece band with three percussionists and three miced horns)

That might get me started ... Although bass drivers are usually meant to deliver transients crisply, so might be a bit unforgiving with guitar?
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Re: Possibly stupid question about amps and cabs

Postby John Egan » Sun Sep 06, 2020 2:44 pm

ef37a wrote:Hi Jon, I am NO Vox historian! Just picked up a few things over time. I think the switch to Blues was done very early on. To be fair to Goodmans, the guitar speaker industry was in its infancy and I guess Celestion just got to a reliable product that bit sooner?

Today of course Cellies have pretty much cornered the UK market for gitamp speakers with Jensen doing much the same over The Pond. Some people bemoan the fact that a lot of production has left these shores but I can tell you from personal experience that doe not mean any loss of quality control.

You might also be interested to know that the very early AC30s used an EF86 pentode as the front end valve? Yes it gave oodles of gain but was noisy and prone to microphony. They soon switched to the standard ECC83. Nothing wrong with the EF86 of course! Especially as back then they would have been Mullards but the valve was designed for more genteel use in hi fi RIAA pre amp stages not the rough ass world of guitars!

Dave.

Thanks for that, Dave. I did know about the EF86 preamp valves, but not the Goodmans speakers. I had an early AC30 Super Twin, but it was a six input model, so I suspect that it didn't have EF86s but it definitely had Celestions.
Regards, John
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Re: Possibly stupid question about amps and cabs

Postby ef37a » Sun Sep 06, 2020 4:33 pm

SecretSam wrote:Thanks Dave and Lord Spoons.

That sounds like a good way to remove worry.

And I just remembered that I have a couple of high-wattage bass cabs lying around: an old 4x10 and a spare SWR 2x10 with tweeter. Both have had 350w heads attached, and haven't yet ripped themselves to pieces (unlike a previous Trace Elliott rated at 250w, which was doing fine until it had to compete with a ten piece band with three percussionists and three miced horns)

That might get me started ... Although bass drivers are usually meant to deliver transients crisply, so might be a bit unforgiving with guitar?

I would not use the cab with the tweeter, they usually make guitars sound horribly spiky and you might even burn it out with heavy distortion.

I think the 10s would sound ok? Remember, in the early days of R&R there WERE no bass speakers as such and they just multiplied up things like V30s and Greenbacks. We had a 200W 15" Fane in a 6cuft relfelx cab and that sounded fine driven from a Dommy' clone and a Mex'Strat (son playing of course!) .

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Re: Possibly stupid question about amps and cabs

Postby Sam Spoons » Sun Sep 06, 2020 5:39 pm

ef37a wrote:I would not use the cab with the tweeter, they usually make guitars sound horribly spiky and you might even burn it out with heavy distortion.

I think the 10s would sound ok? Remember, in the early days of R&R there WERE no bass speakers as such and they just multiplied up things like V30s and Greenbacks. We had a 200W 15" Fane in a 6cuft relfelx cab and that sounded fine driven from a Dommy' clone and a Mex'Strat (son playing of course!) .

Dave.

+1 but does the SWR have a tweeter defeat switch? They often do.
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Re: Possibly stupid question about amps and cabs

Postby SecretSam » Mon Sep 07, 2020 7:12 am

Yes it does. The switch has three settings: on, not-so-on, and off. It's billed as an attenuator rather than a defeat.

I suppose the settings could be re-labelled as on, defeat and humiliate ?
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Re: Possibly stupid question about amps and cabs

Postby SecretSam » Mon Sep 07, 2020 11:41 am

ef37a wrote:
SecretSam wrote:Thanks Dave and Lord Spoons.

That sounds like a good way to remove worry.

And I just remembered that I have a couple of high-wattage bass cabs lying around: an old 4x10 and a spare SWR 2x10 with tweeter. Both have had 350w heads attached, and haven't yet ripped themselves to pieces (unlike a previous Trace Elliott rated at 250w, which was doing fine until it had to compete with a ten piece band with three percussionists and three miced horns)

That might get me started ... Although bass drivers are usually meant to deliver transients crisply, so might be a bit unforgiving with guitar?

I would not use the cab with the tweeter, they usually make guitars sound horribly spiky and you might even burn it out with heavy distortion.

I think the 10s would sound ok? Remember, in the early days of R&R there WERE no bass speakers as such and they just multiplied up things like V30s and Greenbacks. We had a 200W 15" Fane in a 6cuft relfelx cab and that sounded fine driven from a Dommy' clone and a Mex'Strat (son playing of course!) .

Dave.

From out of the mists of memory: When I first got a Night Train, I ran it through one of the bass cabs. I wasn't sure what to listen for, but it sounded ok at the time. Having spent a lot of time having a good 1x12 made, though, it would be nice to use it and a lot easier to carry. So the option of a fused speaker cable is very appealing.

Thanks so much for all the advice.
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Re: Possibly stupid question about amps and cabs

Postby Funkyflash5 » Wed Sep 09, 2020 5:22 am

You could also do the 2 cabs together in series to both increase the impedance and spread the load. Just mic the good cab for recording, maybe even use a long speaker cable to put the bass cab in the next room.
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Re: Possibly stupid question about amps and cabs

Postby ef37a » Wed Sep 09, 2020 8:41 am

Funkyflash5 wrote:You could also do the 2 cabs together in series to both increase the impedance and spread the load. Just mic the good cab for recording, maybe even use a long speaker cable to put the bass cab in the next room.

I never like the idea of speakers in series. Guitar amplifiers afford very little in the way of electro-magnetic damping but putting speakers in series destroys what little they have (but as with almost everything in the gitamp world, 'wrong' can become 'right'! The characteristic sound of a genuine AC30 is due in part I am sure to the series 8R Blues)

Then, one speaker is acting as 'fuse' for the other. I have been told by an amp tech I respect greatly that a speaker in series with another is no more likely to fail O/C than the same pair in parallel but I still don't like the idea!

You must NEVER put speakers of any kind of quality in series. Celestion even made a specially wound 12" speaker of 32 Ohms impedance so that four could be loaded in a bass cab in parallel to give an 8R resultant.

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Re: Possibly stupid question about amps and cabs

Postby John Egan » Wed Sep 09, 2020 9:36 am

Hi Dave,
I always thought that most 4x12 cabs were wired with 2 parallel pairs in series ?
Regards, John
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Re: Possibly stupid question about amps and cabs

Postby ef37a » Wed Sep 09, 2020 10:38 am

John Egan wrote:Hi Dave,
I always thought that most 4x12 cabs were wired with 2 parallel pairs in series ?
Regards, John

Indeed they be! But, the 'classic' 4 by 12 is a prime example of how guitar speakers are NOT hi fi speakers!...Bit o history... The first 12" guitar speakers were really just PA speakers that you would have found in thousands of factories around uk. Put in "Box Baffles" they were hung along walkways and delivered sound from both front and back (each would also have contained a 100 volt line transformer but that is whole other story!)
Rated at about 15W they could just about cope with a push pull pair of 6V6s. To get more power they had to be wired up in fours and the only way to do that was series p'llel.*

The sound they produced became THE definitive rock tone that everyone loved. The cabinets too were totally 'no-fi'. Although 19mm ply they were far too flimsy for their side and had minimal bracing and buggerall internal absorbent! But, put a V30 in a 19mm MDF cab filled with wadding and it sounds dreadful for guitar.

*I once built a pair of line source speakers. Each contained six 4x3" ex telly speakers and each one had its own 3W 100V transformer with each primary in parallel which were saved from small cabs from an old bakery that closed down. Old transformers never die! Those speaker could chuck out quite some level and was nicer quality than straight horns.

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Re: Possibly stupid question about amps and cabs

Postby John Egan » Thu Sep 10, 2020 10:01 am

ef37a wrote:
John Egan wrote:Hi Dave,
I always thought that most 4x12 cabs were wired with 2 parallel pairs in series ?
Regards, John

Indeed they be! But, the 'classic' 4 by 12 is a prime example of how guitar speakers are NOT hi fi speakers!...Bit o history... The first 12" guitar speakers were really just PA speakers that you would have found in thousands of factories around uk. Put in "Box Baffles" they were hung along walkways and delivered sound from both front and back (each would also have contained a 100 volt line transformer but that is whole other story!)
Rated at about 15W they could just about cope with a push pull pair of 6V6s. To get more power they had to be wired up in fours and the only way to do that was series p'llel.*

The sound they produced became THE definitive rock tone that everyone loved. The cabinets too were totally 'no-fi'. Although 19mm ply they were far too flimsy for their side and had minimal bracing and buggerall internal absorbent! But, put a V30 in a 19mm MDF cab filled with wadding and it sounds dreadful for guitar.

*I once built a pair of line source speakers. Each contained six 4x3" ex telly speakers and each one had its own 3W 100V transformer with each primary in parallel which were saved from small cabs from an old bakery that closed down. Old transformers never die! Those speaker could chuck out quite some level and was nicer quality than straight horns.

Dave.

Thanks Dave,
That's interesting info.
Regards, John
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