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OK...
Why/when has the 15" speaker fallen out of favor with guitar players.

Hardly any mention of the 15" speaker anywhere. Maybe some bass cabinets but that's about it.

So I ask the question.....where has the love for the 15" speaker gone?
G.
 

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Why should it be? I see no reason. It's a matter of preference, whether tonal or ergonomic.

15s are still all the rage with steel players (pedal and lap) as well as some dobro and blues dudes. The main benefit being the extra low end over a comparable single 12. Also the resonance point (s) are different and tend to work better for those styles/applications.

I would suspect for rock guitar (with it's faster and denser arrangements) the extra low end is actually a bad thing (mud) and besides once you start piling on the 12s (or even 10s) 2x12s, 4x12s and even 4 or 6 x 10s are actually bassier than a single 15. 2x15s start getting large and hard to move around, never mind 4x15s (but they do still make them; just not many).

A Musicman 115RH with stock Eminence (vs the factory upgrade EV option) is actually really nice for guitar/steel (the EV is better for bass). Most 15 based cabs are bass cabs and these days (not so back in the day) there is a big difference between a guitar and bass 15 - a bass 15 will usually not have nearly enough top end to make a guitar player happy, but old ones did. That may have something to do with it.
 

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SRV made a 15" sound pretty good, too.

One downside to a 15" for guitar is that it is less dispersive at mid/hihg frequencies. A 12" starts to become directional at around 1200 to 1400 Hz, whereas a 15" starts beaming at even lower frequency (while 10s and 8s are better in this regard).
 

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SRV made a 15" sound pretty good, too.

One downside to a 15" for guitar is that it is less dispersive at mid/hihg frequencies. A 12" starts to become directional at around 1200 to 1400 Hz, whereas a 15" starts beaming at even lower frequency (while 10s and 8s are better in this regard).
I don't find mine to be any more beamy than a 12.

I do find it to have a huge sound spread from the rear of the speaker.
 

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I don't find mine to be any more beamy than a 12.

I do find it to have a huge sound spread from the rear of the speaker.
It's physics. I could dig out the math if you want to see it.

Basically, the wavelength of the speaker has a relationship with the diameter of the speaker. Shorter wavelengths (higher freq) will interfere and beam at some speaker diameter - the larger the speaker, the lower this frequency. Smaller speakers always have wider dispersion but suffer in other areas (power handling, bandwidth, bass extension, etc). That's why you will always see hi-fi drivers get smaller as freq goes up, to the point where tweeters are generally an inch or less and domed to maximize dispersion as freq is approaching (and exceeding) 20 kHz.
 

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I don't find mine to be any more beamy than a 12.

I do find it to have a huge sound spread from the rear of the speaker.
Whether or not you noticed, it is so. It is a matter of simple physics: the point at which reproduced sound becomes directional is determined by the width (shortest dimension) of the speaker baffle (or the width of the cone if not in a cabinet). 15s are generally in larger cabinets than (single) 12s so therefore...

That said, a 4x12 will be more directional than a 1x15, because it's at least 1.5 times as wide.

The basic rule of thumb is the frequency at which the (shortest dimension of) the baffle is 1/4 of the wavelength is where the sound starts transitioning from directional (hemisphereical radiation) to nondirectional (spherical) radiation. This effect causes a -6 db shelf starting at that point, which is why putting a cab up against the wall improves bass response - it effectively increases the size of the baffle (to a degree; better still if the speaker is soffit mounted in the wall).

Any speaker in an open back (or no cab) will have identical response from the rear vs the front; that's not what is being discussed here. The dispersion of any speaker should be a bit better from the rear because of the orientation of the cone vs the front - convex vs concave (same reason some hifi drivers use a phase plug vs a dustcap; to improve high freq dispersion to better match that of the tweeter in the crossover region... actually that's why they started using domed dustcaps vs flat ones back in the day). But this is irrelevant because you don't use the back - (assuming you use the cab normally, vs backwards) the treble from the back never makes it to the audience, and the bass wraps around and cancels with that from the front. An oversized sealed cab is a better subject for testing out these things because there are less variables at play.
 

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If 15's were better we would see more of them.
That would be true only if they were no bigger/heavier than 12s and not more expensive (which they are). There is always more than just the tone factor at play when talking about why a given type of gear is popular.
 

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That would be true only if they were no bigger/heavier than 12s and not more expensive (which they are). There is always more than just the tone factor at play when talking about why a given type of gear is popular.
For sure. I've moved and played a 2x15 Dual Showman before. 15s are really only great in 1x15 format. 2x15 or 4x15 is too damn big
 

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Shshhhh. The 15" is my dirty little secret.
LOL.

The best guitar tones I ever got were all the cabs on hand between the lot of us (included a Garnet 2x15) piled into 1 big wall; a single nice large condensor micing the whole thing from 2-3 meters out front. Forget a 57 on the cone.
 

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We seem to be ignoring the mass of a 15" cone and accompanying voice-coil. A speaker's ability to reproduce top end is a function of how quickly the cone can accelerate, and bigger cones don't accelerate as quickly.

That's not to say that it is impossible to design a 15" with a voice-coil and cone that can move quickly at a moment's notice, just harder and more likely expensive. On the surface, it seems more sensible to rely on a 12's ability to move as fast as needed, and design a cab to provide the enhanced bottom one might get out of a 15.

Didn't SRV use a 15 on one of his amps? Perhaps he did so because it smoothed out the harshness from a Strat.
 

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We seem to be ignoring the mass of a 15" cone and accompanying voice-coil. A speaker's ability to reproduce top end is a function of how quickly the cone can accelerate, and bigger cones don't accelerate as quickly.

That's not to say that it is impossible to design a 15" with a voice-coil and cone that can move quickly at a moment's notice, just harder and more likely expensive. On the surface, it seems more sensible to rely on a 12's ability to move as fast as needed, and design a cab to provide the enhanced bottom one might get out of a 15.

Didn't SRV use a 15 on one of his amps? Perhaps he did so because it smoothed out the harshness from a Strat.
Yes. He used a 1964 Vibroverb. Basically a 1x15 Pro Reverb or Super Reverb. I play a clone of one, and it has a unique tone. Incredible amount of dynamic range in the high and low end. I can rarely turn the bass or treble knobs past 4.
 

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I tend to roll off bass, so a 15 doesn't make much sense for me. I think 12s are just more versatile, being able to almost get into 10 or 15 territory.
 

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We seem to be ignoring the mass of a 15" cone and accompanying voice-coil. A speaker's ability to reproduce top end is a function of how quickly the cone can accelerate, and bigger cones don't accelerate as quickly.

That's not to say that it is impossible to design a 15" with a voice-coil and cone that can move quickly at a moment's notice, just harder and more likely expensive. On the surface, it seems more sensible to rely on a 12's ability to move as fast as needed, and design a cab to provide the enhanced bottom one might get out of a 15.

Didn't SRV use a 15 on one of his amps? Perhaps he did so because it smoothed out the harshness from a Strat.
The voice coils are easily made identical (usually are for the same series of drive unit, e.g. EV SRO or JBL D/K/E, for all sizes), and as for the cone, it is more an issue of weight than size. Identical design cones, 12 vs 15, will not be all that different in high end response (yes some, but might not even be noticable, especially if you're listening on axis). Cone materials /designs can very significantly from the thinnest paper (can be treblier than the average geetar 12) to a flat piece of foam core board with no treble response at all. There will be more difference in the bass response between otherwise identical 12s and 15s than the treble.

The fact is that these days, with some exceptions, 15s are made to be bassier (the side effect of which is less treble) - bigger voice coils, underhung for more extrusion, and heavier/stiffer cones to take more power required for repordcing bass without buckling or distortion (aka cone breakup). Back in the day when the only difference between a Jensen P12 and P15 was the size (and weight) of the thing (exactly the same design wise), there was much less difference in response from 12 to 15. Yes still some, but you could easily make it up by using a lighter (more hifi vs pro audio/instrument) cone and/or a more compliant suspension and actually make a 15 that was treblier than the 12. ... or just adding a whizzer cone.
 

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I was lead to believe 15’s were sloppy and a bad idea that went the way of other crappy equipment. 10’s and 12’s were more focused, efficient, and better sounding. If you need to move more air add more 10’s or 12’s. Their size is in the Goldilocks zone. Or not...sometimes I just make this shit up.
 
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