Hi,
You can get a circa clean 8 Watts out of an EL84 single ended but you'll
need a transformer core good for 30 to 40 Watts push-pull. I believe that
poster is simply mistaken as to the operating point of the amplifier.
Only if the operating point is set such that at 4W into 16 ohms the amplifier
is voltage clipping and not running out of current (which in single ended is
nearly always the case at recommended load) will it produce more power
into 8 ohms.
Take a look at : http://www.lundahl.se/pdfs/claus_byrith/cb-amplifier_8wse.pdf
As an article its one of my favourites, a highly informed good read.
That uses 80mA standing current and would give around 4W into 16 ohms.
However with 40mA standing current * it would still give 4W into 16 ohms
(* and hence a smaller transformer core, all things being equal)
but only 2W into 8ohms, which is far more likely to be the case here.
8 ohms should not damage it, just somewhat less power, and mushier,
as the output damping factor will be halved relative to 16 ohms.
FWIW 3 watt wirewound resistors can take something like 10 times that
power for a few seconds, and I don't agree with that posts observations.
Regarding your combo cabinet, I can't see the point of binning it.
Looking at pictures it seems the driver may actually be vent loaded,
i.e the slot in the top acts as a port. Easy to tell, use the back of
your fingers to look for airflow at the slot, playing music through it.
I would consider trying different drivers if you don't like whats fitted.
Regarding your extension cab, the bigger the drivers and the
more of them you have generally the more efficient it will be.
You'll never get a concensus opinion regarding guitar drivers.
Checkout the sound clips for some drivers at eminence.com.
You can go vintage, but with 4W I'd look for as high efficiency
as possible with a really large presence band boost to make
the best use of the limited power.
Speaker Detail | Eminence Speaker
Would make a nice compact loud extension cabinet, with what I'd
call a relatively controlled sound, presence boost, but the response
is not all over the place, YMMV.
If you use two 8ohm drivers for 16ohm, add 3dB to the efficiency.
rgds, sreten.
You can get a circa clean 8 Watts out of an EL84 single ended but you'll
need a transformer core good for 30 to 40 Watts push-pull. I believe that
poster is simply mistaken as to the operating point of the amplifier.
Only if the operating point is set such that at 4W into 16 ohms the amplifier
is voltage clipping and not running out of current (which in single ended is
nearly always the case at recommended load) will it produce more power
into 8 ohms.
Take a look at : http://www.lundahl.se/pdfs/claus_byrith/cb-amplifier_8wse.pdf
As an article its one of my favourites, a highly informed good read.
That uses 80mA standing current and would give around 4W into 16 ohms.
However with 40mA standing current * it would still give 4W into 16 ohms
(* and hence a smaller transformer core, all things being equal)
but only 2W into 8ohms, which is far more likely to be the case here.
8 ohms should not damage it, just somewhat less power, and mushier,
as the output damping factor will be halved relative to 16 ohms.
FWIW 3 watt wirewound resistors can take something like 10 times that
power for a few seconds, and I don't agree with that posts observations.
Regarding your combo cabinet, I can't see the point of binning it.
Looking at pictures it seems the driver may actually be vent loaded,
i.e the slot in the top acts as a port. Easy to tell, use the back of
your fingers to look for airflow at the slot, playing music through it.
I would consider trying different drivers if you don't like whats fitted.
Regarding your extension cab, the bigger the drivers and the
more of them you have generally the more efficient it will be.
You'll never get a concensus opinion regarding guitar drivers.
Checkout the sound clips for some drivers at eminence.com.
You can go vintage, but with 4W I'd look for as high efficiency
as possible with a really large presence band boost to make
the best use of the limited power.
Speaker Detail | Eminence Speaker
Would make a nice compact loud extension cabinet, with what I'd
call a relatively controlled sound, presence boost, but the response
is not all over the place, YMMV.
If you use two 8ohm drivers for 16ohm, add 3dB to the efficiency.
rgds, sreten.
Last edited:
Thanks for the article. It'll take me a while to digest it, but I like it.
When you say vintage you're talking about alnico vs. ceramic magnets? Okay.
Please tell me what you think about box size for a 1x12 cabinet. I have seen a lot of reports in a lot of places to the effect that classic cabs were sized the way they were primarily to save on materials and shipping costs (in other words they were built "just big enough") but not a whole lot thought was given to acoustic design. I've had a lot of recommendations for oversize boxes and that this yields a fuller sound for a given speaker. I've also read a little about "detuned" designs that require a baffle large enough to hold two speakers of a given diameter. This is part of my rationale for starting out with an oversized box. (The other part I've already stated and it's more aesthetic and functional than it is acoustic.) I thought that that would give me the most latitude for trying various configurations.
When you say vintage you're talking about alnico vs. ceramic magnets? Okay.
Please tell me what you think about box size for a 1x12 cabinet. I have seen a lot of reports in a lot of places to the effect that classic cabs were sized the way they were primarily to save on materials and shipping costs (in other words they were built "just big enough") but not a whole lot thought was given to acoustic design. I've had a lot of recommendations for oversize boxes and that this yields a fuller sound for a given speaker. I've also read a little about "detuned" designs that require a baffle large enough to hold two speakers of a given diameter. This is part of my rationale for starting out with an oversized box. (The other part I've already stated and it's more aesthetic and functional than it is acoustic.) I thought that that would give me the most latitude for trying various configurations.
Hi,
Oversize boxes will give a fuller sound, as the baffle size determines
the baffle step frequency, where bass steps down by 6dB. Practically
for working musicians this was irrelevant, they want a portable box
that is no bigger than it needs to be, acoustic niceties aside.
And most drivers are designed to work with compact boxes.
But you can of course make boutique speaker cabs that will never
see the road. Large open baffles work well with guitar drivers,
open backed cabs are simply folded open baffles.
Sealed or vented cabinets are needed for real low down heavy chunk,
the bass player needing a serious rig to keep up, open backed is less
heavy styles generally and more about top end.
Many good guitar cabs started life as bass cabinets, especially open
backed, 15" and 4 x10" stuff, that ended up working far better with
a guitar than bass.
(open backed simply doesn't work well with bass that goes low.)
Yes you can use bigger baffles for a fuller sound, but be sensible.
24"w x 18"h x 9"d is IMO about as big as you want to go for a 1x12",
and it would be a bit of a pain to use on the road. Big baffles for
small drivers do work though, adding quite a bit of body, but
again pretty useless on the road.
Recording sound and a consistent live sound are very different.
Regarding vintage style drivers, they are not particularly efficient,
alnico or ceramic versions, due to the smaller voice coils fitted.
rgds, sreten.
Oversize boxes will give a fuller sound, as the baffle size determines
the baffle step frequency, where bass steps down by 6dB. Practically
for working musicians this was irrelevant, they want a portable box
that is no bigger than it needs to be, acoustic niceties aside.
And most drivers are designed to work with compact boxes.
But you can of course make boutique speaker cabs that will never
see the road. Large open baffles work well with guitar drivers,
open backed cabs are simply folded open baffles.
Sealed or vented cabinets are needed for real low down heavy chunk,
the bass player needing a serious rig to keep up, open backed is less
heavy styles generally and more about top end.
Many good guitar cabs started life as bass cabinets, especially open
backed, 15" and 4 x10" stuff, that ended up working far better with
a guitar than bass.
(open backed simply doesn't work well with bass that goes low.)
Yes you can use bigger baffles for a fuller sound, but be sensible.
24"w x 18"h x 9"d is IMO about as big as you want to go for a 1x12",
and it would be a bit of a pain to use on the road. Big baffles for
small drivers do work though, adding quite a bit of body, but
again pretty useless on the road.
Recording sound and a consistent live sound are very different.
Regarding vintage style drivers, they are not particularly efficient,
alnico or ceramic versions, due to the smaller voice coils fitted.
rgds, sreten.
Last edited:
sreten - When you say an open-back cab is like a folded open baffle, do you mean that the depth of the box would be added to the baffle dimension for the purpose of estimating the F3 of the baffle step response function our is it more complicated than that?
Also, this is going to be a permanent installation in my music room. It won't be for gigging or recording. It's 100% for my own personal enjoyment. Well... 95% musical enjoyment and 5% enjoyment I'll derive from my brother-in-law's envy. 😀 So size is really no issue.
Also, this is going to be a permanent installation in my music room. It won't be for gigging or recording. It's 100% for my own personal enjoyment. Well... 95% musical enjoyment and 5% enjoyment I'll derive from my brother-in-law's envy. 😀 So size is really no issue.
Last edited:
Hi,
Baffle step depends on the size of the baffle. Baffle loss depends on the
distance from the front of the driver to the back. For folded OB you
sort of get both. Too deep open backed can resonate.
rgds, sreten.
Baffle step depends on the size of the baffle. Baffle loss depends on the
distance from the front of the driver to the back. For folded OB you
sort of get both. Too deep open backed can resonate.
rgds, sreten.
So let me see if I have it straight. The step function has to do with high frequencies only being radiated in a hemisphere in front of the cabinet and low frequencies radiating in a full sphere to the front and back. So, from a point in front of the cabinet, you only perceive half the low end power but all of the high end. I'm not sure I understand the physics that causes this transition from half space to full space output but that's the explanation more or less right?
The baffle loss has to do with out of phase signal from the rear of the speaker cancelling the signal from the front of the speaker and if the path length from the rear of the speaker to the front is greater than the wavelength you don't get cancellation? Again am I more or less correct in my understanding?
For right now, I think I've just got one more question. When you say that an open back cab that's too deep can resonate, what is it that actually resonates? Is it the volume of air described by the box... or is it the whole box... or one member of the box? I ask because if I run in to a resonance like that, I'd like to know what's the best way to damp it. i.e. lining the box to dissipate internally reflected pressure waves or adding cross-bracing or... other? I don't know.
Thanks for all the info. I really appreciate it. I feel like I'm at least a little better informed now.
The baffle loss has to do with out of phase signal from the rear of the speaker cancelling the signal from the front of the speaker and if the path length from the rear of the speaker to the front is greater than the wavelength you don't get cancellation? Again am I more or less correct in my understanding?
For right now, I think I've just got one more question. When you say that an open back cab that's too deep can resonate, what is it that actually resonates? Is it the volume of air described by the box... or is it the whole box... or one member of the box? I ask because if I run in to a resonance like that, I'd like to know what's the best way to damp it. i.e. lining the box to dissipate internally reflected pressure waves or adding cross-bracing or... other? I don't know.
Thanks for all the info. I really appreciate it. I feel like I'm at least a little better informed now.
I think you're seriously overcomplicating this 😀
Simple answer - use a guitar speaker for playing a guitar through, HiFi speakers aren't really suitable.
Cabinet design for a guitar speaker is simple, it's low quality, poor frequency range and doesn't really matter much - just chuck a speaker in a box, and that's about it.
Hi, I tend to agree with NG, just don't make a deep open backed cabinet, rgds, sreten.
FWIW the airspace acting as a tunnel will have "pipe" resonances.
I assume semi opened backed is one way of reducing them.
But its all getting way too theoretical for the practical reality.
FWIW the airspace acting as a tunnel will have "pipe" resonances.
I assume semi opened backed is one way of reducing them.
But its all getting way too theoretical for the practical reality.
OhIknow! 😡 ... 😀
This is how it goes with all my hobbies... and I've got several. Model aeronautics, home brewing and cider making, cabinetry, amateur astronomy... I think next I'll build a sweet *** slot car. 🙂
A big part of what draws me to these things is the technical aspect. Once I've learned a little bit I tend to get obsessive. It's usually as much for the satisfaction of knowing as it is for practical application. I appreciate your patience on the face of my barrage of questions. You've all been very helpful and informative. I'll let you know if I come up with anything good. Thanks again!
This is how it goes with all my hobbies... and I've got several. Model aeronautics, home brewing and cider making, cabinetry, amateur astronomy... I think next I'll build a sweet *** slot car. 🙂
A big part of what draws me to these things is the technical aspect. Once I've learned a little bit I tend to get obsessive. It's usually as much for the satisfaction of knowing as it is for practical application. I appreciate your patience on the face of my barrage of questions. You've all been very helpful and informative. I'll let you know if I come up with anything good. Thanks again!
- Status
- Not open for further replies.