Speaker/Cabinet Efficiency

Roger Mouton · #1 04-21-2006, 02:11 PM

I'm a little confused about the speaker cabinet efficiency issue. For instance, I'm an upright player in small combos, mostly jazz or church liturgy gigs using a 30 yr. old, carved German bass and Underwood p/u. I think I want either a Low B-1 or Epifani UL-110 for my Clarus III but I've read that Low Bs are not that efficient. I assume this means I will need more power or have to turn up the volume knob on my amp to get the same sound output as another cab that is more efficient. Right so far?

I recently acquired the Clarus III and for now am running it through one of my Carvin PA cabs (Model 822, 12", 8 ohm). I like the amp a lot. It sounds clean and undistorted at all volume levels so far. The volume control on the amp has never been turned higher than the 10 o'clock position. The range begins at the 7 o'clock position and goes around to the 5 o'clock position. Until I've experimented with different cabs I don't know if this Carvin PA cab is efficient or not. I'm wondering where or when this efficiency issue is going to affect the sound, if at all.

I rarely ever have to double and if I do, it's always been a low-volume kind of gig. No loud bands or wild drummers. An occasional big band but most of the time the volume requirements are not high. I'm coming from 15+ years of using a 15" Polytone Mini-Brute III with a Fishman pre-amp. Any comments or shared experiences are much appreciated. Thanks much.

ToneRanger · #2 04-21-2006, 05:03 PM

Speaker efficiency can make a huge difference to the amount of sound you get. Read the sensitivity specs carefully and be very suspicious if one is not provided.
A 3dB difference is equivalent to double the amp power; a 10dB difference is 10X the watts. For example, an Acme LowB2 at 93dB efficiency needs 10 times the watts to get to the same volume as an Eden 210XST (103dB efficiency).

fdeck · #3 04-21-2006, 08:48 PM

The difference between those two cabs exemplifies a rule of thumb for bass speakers: "Small, loud, and low, pick any two." The Acme has lower sensitivity because it has a lower cutoff frequency.

The Carvin 822 owners manual is at their website and gives a sensitivity curve. The speaker has 99 dB sensitivity, and a cutoff of 80 Hz (that's the -3 dB point -- the speaker definitely operates below 80 Hz, but at progressively lower sensitivity). If you like how it sounds, then you are going to think that the Acme has way too much low end.

It is my opinion that your existing system is pretty nice, and is actually quite efficient.

Roger Mouton · #4 04-21-2006, 10:15 PM

fdeck - Thanks so much for the feedback. I really like the sound (it's so much more like how my instrument sounds unamplified) but I considered it to be a temporary set-up until I could get a "real" bass cab. Now I'm not so sure that I need either the Low B-1 or Epifani UL-110. I will acquire one or the other and I will report on the result if anyone is still interested. Can't tell you all how much this forum helped me to make the decision to buy the Clarus III. Thanks again.

fdeck · #5 04-22-2006, 07:56 AM

One thing you can do if testing cabs is to bring your 822 along, and plug it into the amp in parallel with the cab that you are testing. Now you know that both cabs are receiving the same signal. Sit right in between the two cabs and play at a comfortable volume. If there is a major difference in sensitivity, you will notice it right away. I can't remember if you need a "Y" cable to do that experiment with the Clarus. On the BG forum, one person has suggested to play a CD of regular music through the cabs to really judge how they differ.

**Chris Fitzgerald** · #6 04-22-2006, 08:28 AM

Quote:

Originally Posted by fdeck

One thing you can do if testing cabs is to bring your 822 along, and plug it into the amp in parallel with the cab that you are testing. Now you know that both cabs are receiving the same signal. Sit right in between the two cabs and play at a comfortable volume. If there is a major difference in sensitivity, you will notice it right away.I can't remember if you need a "Y" cable to do that experiment with the Clarus.

I'm no techie and can't even remember the difference between parallel and series wiring, BUT...I did an experiment a couple of weeks ago that involved taking a VL108 (very inefficient cab) to a gig where they had extra Yamaha PA monitors lying around. I mounted the 108 on a stand right behind me and had the PA monitor sitting on the floor behind the drummer. Each was plugged directly into its own Focus II speakon output. The PA monitor was so much louder than the 108 that I could barely hear the 108 at all even though it was right next to my ear. On the basis of this experience, I'd guess that you wouldn't need any special cable to tell the difference in speaker sensitivity if it's very great.

fdeck · #7 04-22-2006, 09:12 AM

Quote:

Originally Posted by Chris Fitzgerald

I'm no techie and can't even remember the difference between parallel and series wiring, BUT...I did an experiment a couple of weeks ago that involved taking a VL108 (very inefficient cab) to a gig where they had extra Yamaha PA monitors lying around. I mounted the 108 on a stand right behind me and had the PA monitor sitting on the floor behind the drummer. Each was plugged directly into its own Focus II speakon output. The PA monitor was so much louder than the 108 that I could barely hear the 108 at all even though it was right next to my ear. On the basis of this experience, I'd guess that you wouldn't need any special cable to tell the difference in speaker sensitivity if it's very great.

Good point. I was probably over-complicating things.

Roger Mouton · #8 04-22-2006, 11:44 AM

Hey Tone Ranger - Thanks. That difference you describe is HUGE! If I read you correctly I'll be pushing my Clarus III real hard, perhaps a little too hard, to get decent volume from a Low B. Sounds like I should be running through a Focus or a WW High or even Ultra if I were to go wtih any Low B cab.

ToneRanger · #9 04-22-2006, 08:28 PM

Quote:

Originally Posted by Roger Mouton

Hey Tone Ranger - Thanks. That difference you describe is HUGE! If I read you correctly I'll be pushing my Clarus III real hard, perhaps a little too hard, to get decent volume from a Low B. Sounds like I should be running through a Focus or a WW High or even Ultra if I were to go wtih any Low B cab.

A 10dB difference between competing brands of speaker is hard to believe. I haven't had the chance to try Acmes here in Australia, but most of the stories I've heard indicate that the specs do tell the story.

fdeck said "Small, loud, and low, pick any two." I agree, but I've gotta say my Eden 210XST is the nearest thing I've found to having all three - compact, genuine 30Hz response, 103dB sensitivity. Only downside is weight.

If you're buying a 110 cab, make sure it's got 98-100dB sensitivity to get solid volume from your amp.

While we're on the issue of speaker specs, for URB extended low end is not as important as it is for BG. In fact it sounds like your PA box might suit DB better than some specialised bass speakers.

fdeck · #10 04-24-2006, 06:17 PM

With any cabinet, sensitivity given as a single number is practically meaningless. Unfortunately, that's what we get from gear makers. You need to look at a curve of sensitivity versus frequency to get a real handle on system performance. The published sensitivity rating could the maximum of the curve, in which case it is not representative of system performance. Realistically getting 98 to 100 dB out of a single 10" driver over all but a narrow range of frequencies is unlikely. Those values are more characteristic of 12" and 15" midbass drivers, respectively.

Note that my website gives instructions on measuring that curve.

Roger Mouton · #11 04-24-2006, 06:44 PM

Francis,

I can't thank you enough. My working life has not been music but technical marketing and has brought me to a patent application. My website is: www.smartcatshield.com

I don't take statistics at face value any more. What is sometimes done in the interest of smart "marketing" riles me to no end. I forwarded the information I received from ToneRanger to Andy Lewis. He offered a sound challenge of sorts. If you want I'll post his reply. I don't think he would mind but I'll ask him anyway. Thanks again for the enlightening post.

fdeck · #12 04-24-2006, 08:22 PM

From what I understand, the Acme cabs are designed to provide flat response down to a pretty low frequency. They give a sensitivity value with a dB range, which is a respectable way to rate a speaker. The low end response has its effect on sensitivity, but for those who want a flat curve, it's the price of admission.

Those cabs serve what may be a growing niche market. One player on the EB forum said that it was helpful to have the same sound in the studio and on stage, when he was exploring a lot of electronic effects to his sound. There are also players who want that fundamental tone, just for the sound of it.

There is another school of bass tone, where it is thought that reproducing the fundamental is not so important. Most classic bass cabs and combo amps fall into that category. By sacrificing the lowest octave, the speaker can be smaller and louder.

But it's an individual decision as to what kind of tone you actually want.

**Jeremy Allen** · #13 04-24-2006, 11:07 PM

May I just say what a true pleasure it is to run an inefficient cab with a flat response down to a very low frequency (a 2X10 Acme) when one has enough power to drive it. I had bad luck with inefficient cabs and a low-power Walter Woods (the VL108 Chris mentioned), and it's no fun; and I had so-so luck with the Acme and an Eden WT400 (which just ended up overheating). But then I acquired an iAmp 800 from the above-mentioned moderator, and the Acme cab has simply come to life. At very high volumes (and with "hi-transient" playing--endless strings of short, loud low notes [a la "Towe of Power" or what's-his-name, Jaco something] and "slapping," ashamed as I am to admit it) it just continues to produce perfect tone; no farting, flaking, or giving in of any kind. I had always scoffed at the people blithering about "headroom" (when one is playing a 100watt amp through a guitar speaker with a 10dB dropoff below 100HZ, why would one think any differently?), but now I have seen the light.
The Euphonic Audio Wizzy is a very efficient 1x12 cabinet with a 4ohm impedance that should make the most of anyone's amplifier; I would imagine it would work well with a Clarus, and I would give a first-hand report of how it sounds with a low-power Walter Woods if EA would get off their behinds and send me one when the next shipment comes in from the factory.

mje · #14 04-25-2006, 06:38 AM

There are a number of ways to improve efficiency in a speaker cabinet. You can use a larger diaphragm, which improves coupling at lower frequencies- the tradeoff being excessive directionality. You can use a horn enclosure- remember EV Eliminators?- with the increase in size and cost and complexity. You can use really massive magnets- which is part of what EA does in the CXL series. You can use tuned ports, or labyrinth designs of various sorts, which invert the backwave and make it work for you. And so on.

bassame · #15 04-25-2006, 08:06 AM

Quote:

Originally Posted by mje

There are a number of ways to improve efficiency in a speaker cabinet. You can use a larger diaphragm, which improves coupling at lower frequencies- the tradeoff being excessive directionality. You can use a horn enclosure- remember EV Eliminators?- with the increase in size and cost and complexity. You can use really massive magnets- which is part of what EA does in the CXL series. You can use tuned ports, or labyrinth designs of various sorts, which invert the backwave and make it work for you. And so on.

This thread sheds light on the relation between size and tone. There must be some kind of mathematical formula relating speaker size and dB drop-off below 100HZ. Some people swear by 12" or 15" speakers for bass, while some like multiple 8" or 6". Just from my primitive experience, I would say that a 12-15" needs less power to give you those low notes, and so requires less of a box to enclose it, while an 8" or 6" needs some kind of enhancement to get those notes: more power directed at the low end or a bigger enclosure tuned to enhance the low end. I fear that this is why we are not going to see an EA VL208 under 30 lbs. anytime soon.

mje · #16 04-25-2006, 08:22 AM

The important phrase to keep in mind is "all other things being equal". If you decrease the size of the speaker but increase the throw- how far the cone moves- you can still get good efficiency at low frequencies. Larger cones don't have to move as much, but the tradeoff is that the larger diameter and mass of the 15" cone is more flexible and has more inertia than an 8" cone, so the amplifier has a harder time controlling the motion of the cone, there's poorer damping and more distortion. My home stereo speakers use 8" woofers and a passive radiator to deliver excellent, room shaking fundamentals.

Double Bass players looking for accurate reproduction should stop thinking about "what size cone do I need" and think more like modern HiFi buyers. Find a an intergrated speaker system that delivers accurate reproduction over a wide frequency range, and can do it at the volume you require, with the amplifier power you have available.