Speaker's corner

[Jensen P]

New member with some speaker related questions:

I got my first guitar amp in the '70s and have had a few over the years. A long time ago I learned that the power rating of the amp and the size of the cab and the number of speakers don't necessarily translate into actual volume output. I later found out what different speakers could do to change the character of an amp (or at least the amp-speaker system...). I've just accepted this as part of nature until I recently ventured into the universe of Tweed amps and would like to understand these things a little bit better . So, I turn to you guys:

Some speaker models perform over the entire volume range, whereas others needs to be played fairly loud to open up and "breath". The latter sound stiff, chocked and dull at low volume, but can shine with the best of them when played loud. As far as I know, this characteristic is not revealed by specification parameters like sensitivity (dB) or power rating (watts) or magnet size/weight;

-What are the dependencies? suspension? -Is there a specification parameter that can be used to get a hint on how a speaker will perform over the entire volume range?

-Sensitivity is measured as dB at 1w and 1m. But what's the sound pressure level at 25w ?

A certain speaker might sound great with a particular amp, but not so good combined with another amp. A Speaker has an official frequency response curve, but the actual output frequency spectrum obviously depends on the amp and the instrument plugged into it. Let's say that the target is to get a flat frequency response; Then If I have a brittle amp, I could combine it with a speaker that emphasize bass reproduction and vice versa....

Problem is that since the frequency response of both speaker and amp varies with volume output, there's not much meaningful information to get from the speaker spec sheets to make an informed decision. Especially when entering the realms of distortion. You're on your own, trial and error...

-And what about a speaker's impedance curve? A speaker’s impedance isn’t just one number; its actual value will vary by frequency. Part of how hard a speaker is on an amplifier depends on the actual impedance curve;

-Is this also dependent on output volume? And is the actual speaker impedance in fact dependant on the particular amp, considering phase angle and damping etc?

Thanks

[Chuck H]

So, are you just making observations or asking a question?

Indeed, speaker/amp pairing is probably the most critical component of the final tone/feel. It's good then that guitar amps and guitar amp speakers have, for the most part, been designed analogous to each other. The amps designed load and damping paired against a particular speakers dynamic impedance as well as an amps specific frequency characteristics paired with a particular speakers as well as an amps actual power paired with a particular speakers rating/efficiency can certainly make the whole ordeal daunting. Because of the sheer number of variables, lack of comprehensive investigation reports, that many parameters alter WRT each other and the fact that tone is an entirely subjective issue, there are no hard rules and very few useful guidelines. That's probably why many of us here have several different speakers in boxes or have sold or traded several different speakers. And we do this with experience from a design perspective!

About the best you can hope for is to read reviews and recommendations to try and glean what has been a successful amp/speaker match and then try a model that seems like it might suit you. If that doesn't work, try another. Keep going until you're happy or you run out of money and patience. This is literally what we all do. There are many, many threads here that cover speaker selection and clearly demonstrate the inherent difficulties around the subject.

You WILL get a feel for what sort of speakers YOU like with different types of amps eventually now that you're looking for it. It may be helpful for you to consider what you thought were some of the better amps you've used and try to discover the nature of the amps (Marshall type, Fender BF or tweed type, other) and if you know what speakers were used, try to find similar after market models. Many guitar speakers anymore are described as being like a familiar, vintage model or at least state if they have a "British" or "American" voice, how bright or dark they are and their efficiency. You simply need to start with an educated guess and hone in from there. No straight path here that I'm familiar with.

[Jensen P]

Thanks Chuck for taking your time, I appreciate it.
I'm making observations (like the frog at the bottom of the well) and probably have too many questions.
I'll be more be specific:

-How come many guys put a 15W Celestion Blue into a 15W 5E3 Tweed Deluxe , when conventional wisdom recommends at least 25W to prevent damage to the speaker?

The Jensen P12R reissue is rated at 25W, but the '50s original was rated only at 12W; -Is this the same speaker, but with different principles of power rating? and If so, would the Celestion Blue be closer to 30W with modern standards? (rated power - not peak power).

The Jensen P12Q (40W according to modern standards) is rated at the same sensitivity (95 dB) as the P12R, but in reality the P12Q is louder and stiffer (needs to be played at higher volume to open up). The amp also appears to dissipate more heat with the P12Q. But the 9.3 lbs heavy weight 15W Celestion Blue is even louder at 100 dB (Big magnet , heavier than my LP, ouch) . Then there are Eminence Legends rated at 50W and beyond, with a sensitivity at 101 dB but open up already at low volume...

The speaker specs don't seem to provide any meaningful information whatsoever, at least not when it comes to the vintage reissue speakers mentioned above paired with my Fender 5E3. I personally think the P12R (or P10R) is a supreme choice for most of the classic Tweed circuits. Just like these amps were originally designed. The reissues sound great, but;

-Would you trust a 60 years old original? or maybe an original P12Q is closer to a reissue P12R in overall performance?

[Enzo]

-How come many guys put a 15W Celestion Blue into a 15W 5E3 Tweed Deluxe , when conventional wisdom recommends at least 25W to prevent damage to the speaker?

A 15w amp does not sit there making 15 watts, 15 watts is the maximum power it produces into load. In the sense that your car is a 120 mile per hour vehicle. it is only if you push it there. Your 15 watts will be the peaks on your big KABANG strum. I shouldn;t run 20 watts of steady sound through a 15w speaker, but the occasional peak won't kill it.

The Jensen P12R reissue is rated at 25W, but the '50s original was rated only at 12W; -Is this the same speaker, but with different principles of power rating? and If so, would the Celestion Blue be closer to 30W with modern standards? (rated power - not peak power).

Same? No. Equivalent? Yes. Chevrolet brought out the Impala model in 1958, and they still make it. If they were the same, everyone would be clamoring for them.

Don't get hung up on numbers. The specs are there to help compare models, that's all. Not rocket surgery. The efficiency rating tells us how loud it should be with respect to others. We all know the impedance of a speaker is a broad curve, not a steady number, but it is measured consistently so we can use it to establish comparisons. Your speaker is NOMINALLY 4 ohm or 8 ohm, and all that means is the response curve is further up or down the impedance scale.

[soundguruman]

You are over-thinking it.
The speaker depends heavily on the cabinet, and any different cabinet produces a different result.

The speakers that sound really good...are really expensive.
And the cheapo speakers that don't sound so good...are cheap.

And all manufacturers brag that their speakers sound great...which most of them don't.

It's about 95% hype, and 5% truth. And most of the published specifications (from cheap manufacturers) are pure BS.

So, when we buy a speaker we do not analyze the specifications, because (mostly) it tells us so very little.

[Chuck H]

Another thing to consider is that most modern speakers. even vintage re-issue models, are made with better tolerances, materials and adhesives than the originals. Usually their actual power capacity is higher than their rating as designated by their namesake. But since there are no clear definitions on this it's best to stick to the rated wattage. But my point is that some people have successfully run modern speakers of questionable wattage rating and discovered this.

Basically, if you're going to run the amp cranked a lot you'd probably do well to have a speaker of twice the amps rated wattage. If you're going to use the amp clean much of the time, any of the recommended speakers will do. Even the 15W Celestion. A speaker of 15W isn't likely to blow up from over powering in small bursts it in a 20W amp, but if you put the screws to it full time it will probably overheat the coil. And that's where the real danger is.

[Tooboob]

Makes sense to replace a Jensen speaker with a Jensen speaker if you like the first one, but today's Jensens aren't like the old ones. I could try to describe the difference in sound, but my point is that they don't sound the same. You'd get closer with some other vendors that try to get that vintage Fender sound. There are lots of vintage Fender fans here who can give you free advice at a fair price.

Speaker specs can be somewhat useful for designing a matching tuned cabinet. Fender combos don't even have backs. For most audio applications, the cabinet linearizes the response of the speaker and extends its low-end range. You need to know the speaker's resonant frequency, etc. to do this properly. Combos only provide a bit of interference between the front and back of the speaker, and even closed-back speaker cabs for guitar lack such niceties as internal damping material. The result is that the speaker is flapping in the breeze, the science pretty much goes out the window, and you pick with your ears at $80 a taste. You listed lots of reasons for this yourself. If it was science, they wouldn't all sound so different.

You also need to remember that speakers need to be broken in, and this can take hours at fairly high volume. There's a recent thread on that.

The amp, speaker, guitar, etc. all interact together to get the result. You get things tuned until you find them acceptable, then change an element. You probably won't like it, but changing another piece of the puzzle too might result in something you like better than the current state of affairs - at least until you walk away and come back.

That's the source of the addiction.

[Jensen P]

Thanks guys, good input.
I enjoy your philosophical aspects of the matter; speaker matching is a form of art, where trial and error is "the source of the addiction". I appreciate that this is probably the driving force behind the evolution of these amp icons in the first place. And I have no problems to embrace a speaker like a fine wine (where the match certainly is more important than the price).

I'm back at square one (at the bottom of my well). Content with the fact there's no need to surface.