# low effeciency vs. high effeciency speakers for my setup



## BEMUSofNrthAmra (Jun 9, 2012)

Hey guys,

I've been racking my brain for months over which speakers I'll be putting in my recently completed 4x12.

I run a '77 Marshall JMP Super Bass 100w head. I've already got a Marshall 1552 2x15. It has two Celestion Sidewinder 260watt 16 ohm speakers. The Celestion Sidewinders are known for being somewhat sterile sounding, and harsh with guitar distortion. I read they were created to compete with the EVM15L and JBL E130 guitar speakers, and based on the 60-5000Hz freq range, I've come to the conclusion that it is a guitar driver, not a bass woofer.

IME, it sounds good with my Super Bass.

I use a Gibson SG with 2 p-90s with a few distortion pedals.

The Sidewinders break up when the amp is set around 7-8. This leads me to believe they are a pretty efficient speaker.

What I'm looking for:

I play loud, distorted, heavy music. I make use of feedback, and not so natural guitar sounds. I play in Drop-C#. My tube amp is not high gain, I typically like to run the power section into break up and then use a Treble Booster to break it up further. Sometimes I'll run the amp clean and put on my Sunface NKT high gain for a different tone. I get plenty of tight bass response from my 2x15.

Here are some 12 inch drivers I've considered so far:

- Weber Legacy 12: these are based on the Greenback and have a few options. I was thinking of getting 2 with the 75hz cone style, and 2 with the 55hz cone style for a balanced sound. 50oz magnets for medium efficiency. British dust caps.

- Weber High Power Chicago/Thames: these would go well with my sidewinders and would provide lots of clean headroom for my distortion pedals.

- Weber Axis 12: for that Fane tone. I thought these would be great for that loud, smooth, creamy almost Hiwatt type tone.

- Celestion G12-65 Creambacks: these just sound amazing, it would be cool to have all Celestion speakers.

I'm wondering whether I should use high efficiency 12s to match my 2x15 in order to get a loud, clean sound, or if I should balance it out by getting some lower efficiency 12s that break up sooner. 12s that break up sooner might make it harder to keep a clean sound, but would sound better for power tube saturation.

I'd like to hear some options for Scumback and maybe some Eminence too. I bought a pair of 15 inch Eminence Delta A speakers for a cabinet a few years ago and they were great. Weber, Celestion, Fane, Eminence and Scumback all make great speakers, and each have about a dozen 12 inch models, making it very hard to choose. 

kkjqkkjq:thanks5qx:


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## mhammer (Nov 30, 2007)

You're confusing breakup and efficiency. A speaker's efficiency (sometimes listed as "sensitivity") is rated in terms of the sound-pressure level produced at one metre distance with one watt feeding the speaker.

So, for instance, the Celestion G12-65 Creamback lists a 97db SPL as its sensitivity, while the G12-60 shows 98db and a Vintage 30 shows 100db.

The Fane AXA STUDIO 12L comes in at a whopping 102db. Meanwhile this Eminence page for the Red Coat series - Redcoat Series | Eminence Speaker - lists sensitivities from 98.7 to 103db, while a Jensen P12R comes in at 95db. That's a more-than-quadruple difference in SPL between the P12R and the most efficient Eminence 12"-ers.

Now, it may well be that a speaker can break up well before it reaches its maximum SPL, and that different speakers will reach the breakup point in different ways. But that's something you'd need to audition, rather than something you could tell just from a listed spec.


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## BEMUSofNrthAmra (Jun 9, 2012)

I was going off what I've read on the Weber site.



> *Magnet size: smaller = less efficient, more breakup. larger = more effecient, louder, cleaner (generally).*


This is where I got the idea that bigger magnets means louder and cleaner.

All this efficiency talk aside, I'm still looking for 12 inch speakers that will pair nicely with my 2x15, which are pretty loud and clean.

Thanks for the mini lesson though, I'm always looking to learn more about speakers and how they work. Should help me make a better, more informed decision.


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## washburned (Oct 13, 2006)

I would suggest you check out the Eminence site and their charts that describe the speakers' sound re bottom, middle and top. Based on what you said above I would reccomend a speaker with a "tight" bottom end, since you will get lots from the fifteens, a "pronounced" or "focussed" mid range to keep up with all the bottom end and cut thru, and a "clear" top end. I think anything along those lines would work well with the other gear you have for the style of music you are playing.


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## hollowbody (Jan 15, 2008)

Don't forget that when we're talking breakup, there's a couple different kinds. There's amp breakup, which is easier to get when you have low-efficiency speakers, because you'll have to turn the amp up further to get the same volume and you'll start overdriving the tubes. Amp breakup can also be divided into preamp tube breakup and power tube breakup, which are totally different sounds. Then there's speaker breakup, which is the actual speaker cone distorting when it's being pushed hard. Speaker breakup (which I think is what you're asking about) sounds different then amp breakup, and is a matter of taste.

For example, I like the way my amp sounds when it's breaking up, but I do NOT generally like speaker breakup, so I prefer speakers that stay clean and an amp that gets dirty. It's kind of all about the sound you're after.

Generally a lower wattage driver will break up earlier than a higher wattage one, which is what Weber is getting at with magnet size (which is directly proportional to a driver's wattage). The efficiency, as mhammer pointed out, has more to do with how loud a driver can get given a certain amount of wattage, but as far as I know, a 30 watt driver with 91db efficiency isn't likely to breakup any earlier or later than a 30 watt driver with 97db efficiency. The more efficient driver will just sound quite a bit louder.


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## mhammer (Nov 30, 2007)

Think of speakers like cars. A 300 horsepower engine pushing a 6-ton vehicle won't generate as much movement and acceleration for the same amout of engine work and gas consumption as 300hp pushing a 3-ton vehicle. Similarly, 120hp on a small vehicle with 16" diameter tires won't get as much acceleration and zip as the same vehicle with 20" diameter tires. And finally, the same engine, tires, and vehicle size won't result in the same speed and acceleration when one has less compression in the cylinders than the other.

So, moving to the speaker context, the same output current from an amplifier going into an identical coil will accomplish more "work" at the speaker if:

- the magnet is stronger (usually associated with size, but also with type) - akin to horsepower
- the gap between the magnet and the coil is narrower - akin to compression
- the cone is lighter - akin to vehicle weight
- the cone has greater compliance (forward/backward motion) - akin to tire diameter

A speaker that can easily deliver greater SPL may well break up a little earlier in some instances. Keep in mind that sensitivity/efficiency is different than power rating. The power rating tells you how much current that speaker can tolerate before the voice coil goes poof. Part of what makes a voice coil go poof like a fuse is friction, and friction can occur from having a smaller magnet gap and less room to move around in for the voicecoil - the very thing that increases sensitivity. So, a speaker can be very responsive, perhaps because it has a light cone and voice coil, but like a small vehicle that starts to get shaky when you're pushing 135 on it, the speaker might start breaking up.

Conversely one could have a speaker with a fairly bulky and stiff cone and coil. Part of what makes that coil heavy is thicker wire (what you use for higher current-handling capacity), and part of what allows that coil to tolerate higher current is a spider that does a better job of centering the coil, ultimately adding more mass to the cone structure and - you guessed it - reducing efficiency. So, the very things that allow the speaker to handle more wattage can be the very things to reduce efficiency.

Weird, I know, but you can have speakers with puny magnets that kick the ass of seemingly more powerful speakers. And remember as well that one generally requires roughly 10x the wattage into the same speaker to produce double the loudness. The power-handling rating on the speaker does not provide nearly as much of an indicator of low "loud" it is as many people think. If I have a speaker rated at 30W handling, and another rated at 100W, the second one will not be capable of being "three times as loud" as the first one. Certainly, if they had identical efficiency, the second one is able to be somewhat louder than the first, since I can push more power into it, safely. But where I could probably safely push 25W into the first (though not at sustained levels, as with a signal generator), I won't be able to push 250W into the second (the power difference required to produce double the apparent loudness).

All of this is partly why cab design matters as much as it does. The differences in loudness between any two speakers of the same size and relative efficiency doesn't matter nearly as much as the extent to which the cab itself is able to harness all that energy productively.

So, bottom line, look for efficiency/sensitivity ratings as a first approximation, but don't rely on them too heavily for an indication of higehr-volume tones and breakup.


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## BEMUSofNrthAmra (Jun 9, 2012)

Thanks for all the info guys.

I obviously have a lot to learn about speakers.

When I was looking for 15 inch speakers for Bass, one of the major ratings, if not the most important I was told to look for was Xmax. The higher the Xmax, the better. Is this figure as important for guitar drivers as it is for bass? I know most modern bassists care more about accurate sound reproduction vs. instrumental coloring like most guitarists, so Xmax might not be as important in choosing guitar speakers.


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## hollowbody (Jan 15, 2008)

Never heard of it. Does it have to do with the drivers' excursion?



BEMUSofNrthAmra said:


> Thanks for all the info guys.
> 
> I obviously have a lot to learn about speakers.
> 
> When I was looking for 15 inch speakers for Bass, one of the major ratings, if not the most important I was told to look for was Xmax. The higher the Xmax, the better. Is this figure as important for guitar drivers as it is for bass? I know most modern bassists care more about accurate sound reproduction vs. instrumental coloring like most guitarists, so Xmax might not be as important in choosing guitar speakers.


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## mhammer (Nov 30, 2007)

Well, I just looked it up and it's a real thing. I just don't think it matters all that much in our context. It would appear to be a spec for subwoofers, and especially smaller ones for cars and such. If you can't have a properly designed cab (because you still want trunk space) and you plan on never playing any content above 200hz, then Xmax can matter. But here? Nah.


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## BEMUSofNrthAmra (Jun 9, 2012)

Hollowbody, yeah it has to do with excursion. It's basically how far the speaker cone can move from rest. From what I've read over the years, it's pretty important when choosing bass woofers.



mhammer said:


> Well, I just looked it up and it's a real thing. I just don't think it matters all that much in our context. It would appear to be a spec for subwoofers, and especially smaller ones for cars and such. If you can't have a properly designed cab (because you still want trunk space) and you plan on never playing any content above 200hz, then Xmax can matter. But here? Nah.


That's what I thought. It was BillFitzMaurice at Talkbass.com who touts Xmax as the most important rating when looking for speakers. He actually builds some pretty cutting edge cabinet designs for bassits, and is more about accurate sound reproduction than "coloring" sound like with guitar cabinets. He is also a strong supporter of neodymium magnets. Xmax must be more of a hi fi thing.

It's coming down to the ears. Specs and ratings do nothing but make my head hurt.

One thing I know for sure is that I want a "british" tone. I am also looking real hard at Weber, but sure why. I like their prices, I can get them easy in Canada. I'm going to do some more youtube research. I don't know anywhere around here I can even hear a cabinet with Weber speakers...


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