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Post by Hohn on May 22, 2006 5:54:29 GMT -7
Just curious:
How would a 2x12 configured with 50W speakers compare volume-wise to a 4x12 with four 25W speakers, if all the drivers had the same sensitivity?
Assuming, of course, they are cranked wide open operating at max power rating....
On one hand, logic seems to tell you that 4 speakers would be louder.
On the other hand, the total amount of power being consumed is the same, so you COULD reason that same power+same sensitivity= same volume...
Justin
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Post by billyguitar on May 22, 2006 10:50:40 GMT -7
Another important consideration is the phase cancelling you get with 4 x 12s in one box. Sucks out some of the mids compared to a 2 x 12 cab.
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Post by Hohn on May 22, 2006 12:37:19 GMT -7
Does a cab have to be wired in series to avoid phase cancellation? So it would seem to the amatuer mind (me).
jh
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Post by billyguitar on May 22, 2006 13:13:47 GMT -7
No it can't be avoided. It's part of the signature Marshall 4 x 12 sound.
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Post by Hohn on May 31, 2006 13:11:11 GMT -7
TTT
So what about the <<VOLUME>>?
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Post by billyguitar on May 31, 2006 15:10:50 GMT -7
Depends on the efficiency of the speakers in question. 2 EVs in a box will be louder than 4 greenbacks in a box. If not louder at least equal. The wattage of the speakers won't matter. If they are the same efficiency then the 4 x 12 box will be louder, may not be that much though. I've never a/b'd this arrangement before so I'm speaking hypothetically. In other words I might be full of poop!
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jbro
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Post by jbro on Jun 4, 2006 11:26:30 GMT -7
I don't think it's the difference in volume that you notice primarily when changing the number of drivers. Theoretically, you can get a 1x12" as loud (dB wise) as a 4x12" - with the right speaker and cabinet choice. From my experience the difference you notice is the "feel" of more air moving because of the additional vibrating surface of more speakers.
For example, plug into a loud 1x12" in a live band scenario, and smack your strings with your right hand while muting them with your left (for a percussive effect). You hear a "whack" come through the speakers. Now do the same thing with a good 2x12" or 4x12".. and instead of hearing a "whack", you feel a "thud". While the overall volume may not really change, it is moving more air.
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In the scenario you gave, I think it all comes down to cabinet size and construction.
Are we using the same 4x12" cabinet for both sets of speakers? 2 speakers in a 4x12" gives us a "detuned cabinet" - there is a lot of debate among cab builders and speaker manufacturers as to the result of a detuned cab. Some say it is more efficient with a more linear frequency response than a fully loaded cab, others say it's nonsense.
Now if we stick the 2 50 watters in a tiny open backed 2x12", and the 4 25 watters into a sealed back/front ported 4x12"... one would expect more volume and projection from the 4x12".
The opposite is also true, though. I have an Earcandy Buzzbomb 2x12" - sealed back, front ported, 16" deep(!), front mounted speakers, etc.. this thing sounds "bigger", "fuller" and "louder" than any 4x12" I've played through or along side of.
I think when you stick speakers in a box, the box has perhaps a more important role than the speakers in determining the final sound and projection qualities. Try taking your favorite, most beloved speaker out of the cab, then stick it on a towel/blanket face up on the floor, hook it up to an amp, and see how much you like how the actual speaker sounds by itself. Yuck.
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If you're asking this question because you want to get more volume out of your rig, definately look into a good 2x12" (like a Z best) and some efficient speakers. IMO even the best 4x12" on the planet won't yield enough of a difference to justify lugging it around.
If you're asking from a technical/theoretical aspect, then we need to debate actual dB vs percieved volume, projection/dispersion patterns, frequency cancellation, etc... I think it's best to say that there's no easy answer to this question and it mostly depends on the cabinet!
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Post by Hohn on Jun 5, 2006 8:22:43 GMT -7
I ordered a 2x12 with Blues when I ordered my Stang Ray, so this is somewhat of a hypothetical.
Really, what prompts all this is my reading of the articles on Phil Jones's website (the bass amp guy). The theory of multiple smaller drivers makes sense to me.
So I'm looking to build a cab unlike anything seen yet: a 9x8 or 9x10 in a 3x3 configuration, and I'm doing some homework now to see if it makes sense.
JH
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Post by billyguitar on Jun 5, 2006 9:05:34 GMT -7
Curious about the multiples of three? Ampeg had a V9 cab that had nine 10s, I never knew why. I think the Stones used them in about 1971. Gibson had amps with 4 x 8" and a 6 x 8". I don't know what the intent was but they make good harmonica amps. Little Walter used them. You might try one of those SWR bass cabs that have 6 or 8 eight inch speakers. You can turn the tweeter off. I don't mean to buy but so you can hear the what the configuration sounds like.
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jbro
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Post by jbro on Jun 5, 2006 9:33:30 GMT -7
I ordered a 2x12 with Blues when I ordered my Stang Ray, so this is somewhat of a hypothetical. Really, what prompts all this is my reading of the articles on Phil Jones's website (the bass amp guy). The theory of multiple smaller drivers makes sense to me. So I'm looking to build a cab unlike anything seen yet: a 9x8 or 9x10 in a 3x3 configuration, and I'm doing some homework now to see if it makes sense. JH A friend of mine in the pro audio engineering field has a bunch of Phil's stuff - one of his cabinets has something like 24 5" or 6" drivers, with another slanted cab on top with 8 more. He's powering it with a couple amps of his own design.. it's scary. Phil has some great ideas and you can absolutely get a huge frequency range and dB level out of an array of small drivers, but I'm not sure I would personally want to take such a hi-fi type of approach to amplifying the guitar. I've played through his cabs, both with his amp and a few of mine... the clean sounds with a solid state amp are great. If you're going for the crystal clean Metheny jazz tone, that's it. But put any kind of hair on the notes and it gets ugly fast. A tube amplified/overdriven guitar really lends itself to a certain frequency range.. and you can't really have a lot of small, efficient drivers and still expect to attenuate the tones outside of that range effectively. Personally I can't imagine a semi-dirty or overdriven guitar through a tube amp sounding very good through a bunch of 8" speakers. I would think you'd end up needing to dampen the high frequencies somehow. The 10" thing is somewhat common.. I know there's people on here with 4x10"s.. you know somewhere, someone bought 2 4x10" cabs and stuck them side by side. I think if it was a great sound more people would probably be doing it. And again, I think the cabinet has more to do with the end result than the speaker configuration. What exactly are you trying to achieve by using an unconventional setup like this? More volume? Extended frequency range? A "bigger" sound?
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Post by Hohn on Jun 5, 2006 11:48:07 GMT -7
Goals: 1) Make the ratio of voice coil/diaphram mass more favorable-- get better control over drivers (think more percussive attack and tighter bottom end) 2) Preserve overall tonality 3) Reduce "ice pick" factor by having more HF sources than just one or two. This to me would make for a "bigger" sound overall. 4) Allow use of lower-wattage speakers and still have good power handling. Here's a burning question: PHASE CANCELLATION.Specifically, how is it that some speakers are "out of phase" in a standard 1960 Marshall 4x12 for example? I just can't see it! By my reasoning, "out of phase" can either mean 180 degrees out of phase, or anything other than perfectly "in phase." In a multi-speaker cab, you won't have any drivers 180° out of phase unless the current flows through them the "wrong" direction-- easily avoidable by reversing polarity. Thus we're left with "anything other than perfectly in phase". Again, by my reasoning, you're talking about time relationships, and so I suppose that theoretically different wiring lengths like you'd have series/parallel cab could cause some of this, but anyone who can hear the difference phase relationships between a couple inches or feet of wiring carrying a signal at the speed of light has some REALLY special (of not imaginative) ears. Besides, this could easily be remedied by making all the wiring the same length. So, how is it that a 4x12 "has to be" out of phase? I just can't see it. As for semi-dirty or OD guitar through a 9x8 or 9x10, it would depend on the individual drivers. If you can find an 8" driver that actually sounds good in a 2x8 or 4x8, then it would sound better in a 9x8, imo. And we all know that a 10" is capable of some great tones. An old 4x10 Bassman comes to mind. So what about a 9x10 with some Alnico Jensen-like drivers from Weber? Sounds like plan to me! As for the question of "why aren't more people doing it", well that's a separate issue for a social psychologist to answer, along the lines of "why do some people like Ford, some Chevys, and others neither?". Thanks for the great input so far, fellas. For the record, this will be a GUITAR cab for use with tube amps. Either 30w Stang or 100W Peavey. Justin
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Post by billyguitar on Jun 5, 2006 12:10:20 GMT -7
I can't tell you the science behind it but a 4 x 12 cab has a sound and that's the reason, phase cancellation. At least that's what I read but it's been so long I can't tell you where. Some time back on this forum, someone had a mini-Marshall home made cab with four 8s. It was cute as a button! I thought it would be great with a Carmen Ghia. One time at a guitar store I plugged into a Fender Acoustosonic Junior with two 8s. I thought it sounded very loud and clean. Some jazz amps have 8" speakers, like Evans. They wouldn't use them if they didn't sound good but 'good' is subjective. 8" speakers will be very fast and snappy and won't sound like traditional guitar speakers so there will always be resistance there from some people.
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Post by Hohn on Jun 5, 2006 12:45:33 GMT -7
No offense, Billy-- but until someone can explain to me HOW this is the case (the phase cancellation, I just can't see it.
Got any links for me? I've been Googling this to death with no luck...
justin
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Post by billyguitar on Jun 5, 2006 12:54:58 GMT -7
Some of the DI boxes refer to this, I believe, when they say they emulate a 4 x 12 cab. I'm sorry I can't be more specific. Sometimes I only remember the bottom line answer and not the formula that leads up to the answer. I'm not the sharpest tool in the box but I don't make things up either. I'll let the subconcious work on it. If it tells me anything I'll let you know.
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jbro
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Post by jbro on Jun 5, 2006 14:13:40 GMT -7
The only issue relating to phase cancellation that I know is if one driver is wired backwards and working reverse of the others (180* out, as you mentioned). A similar effect may come from putting more than one type of speaker into a cab (not perfectly "in phase" due to different response times). If your drivers are all matched, I don't think you have much to worry about.
There might be some type of frequency-specific cancellation or interference with a pair of parallel wired speakers that are wired in series (or vice versa), but I can't say I've ever heard of that.
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I think you're on the right track with your goals, I just personally have never heard an 8" speaker that really "did it" for me amplifying anything but clean guitar. I would imagine a nice set of low-wattage 10"s would sound great in an array like that. I like the idea of the greater dispersion/beam reduction, and being able to use undoped, low wattage speakers at a high power level.
I hope you keep us updated about this project, I'd love to see/hear this cabinet when you're done. Any reason you want to go with an odd number of drivers?
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Post by billyguitar on Jun 5, 2006 14:22:48 GMT -7
Out of phase is different than frequencies that cancel out. It's a common phenomenon that's most apparent in bass frequencies. Stereo guys stroke about it all the time when standing waves cancel or reinforce bass frequencies in a room in particular. It's also important inside speaker cabinets. Detuned cabinets are an attempt to minimize these effects for a more neutral sound.
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Post by Hohn on Jun 6, 2006 11:54:09 GMT -7
The reasoning for an "odd" number of drivers is simple: impedance matching.
If the number of drivers in a cab is a "perfect square", meaning it's the results of "squaring" some other number, then matching impedance becomes easy.
For example, say I have an 8 ohm speaker. Obviously, the total impedance is 8 ohms (1 is a perfect square).
Now I go to two speakers. I can't combine two 8 ohms speakers and get 8 ohms-- I have to have either 4 ohms (parallel) or 16 ohms (series).
But when I go to the next "perfect square of FOUR (2 squared is 4), I can now use 4 each 8ohm drivers and get a total impedance of 8 ohms for the whole cabinet.
You have to increase the number of drivers to NINE to get to the point where the total cabinet impedance will or even CAN be the same as the impedance of an individual driver. So here's how I wire a 3x3 configuration of drivers: group them in three groups of three, with each group wired in series within itself, and in parallel to the other two groups. I have 3 groups of 24ohm loads (from the 3, 8-ohm drivers in series), and the total impedance of three 24ohm loads in parallel is PRESTO-- eight ohms!
A person can build a cabinet with 16, 25, 36, etc drivers and repeat this scenario-- the total cabinet impedance can easily be made to equal the impedance of a single driver.
This matters to me because I want to use drivers that are all the same, and I want the total impedance to be 8 ohms to match my THD Hotplate.
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As for the phasing, I think of phasing as simply time relationships. If there's ANY shift in the timing of one frequency relative to another as it travels through a system, then you have some phase shift.
Backwards wiring just represents the most severe case of out of phase. You can't get more out of phase than 180°, so that's the worst case. But even a difference of 2 or 3 degrees can be said to be "out of phase".
The bass instances that billy is talking about are phase-related because it can either cause CONstructive interference or DEstructive interference. In the former case, the amplitude will increase to the sum of the two amplitudes at the same frequency. In the latter case, the amplitude is lessened by the "destruction" caused by a frequency being 180° (or close to it) out of phase.
Interference will be "neutral" at about 90° out of phase relative to the original frequency. The closer you get to zero, the more "constructive" it will be, and the frequency will be louder. The closer you move from 90 towards 180, the more "destructive" it will be, and the frequency will get quieter.
But since we're talking about many many frequencies all happening at the same time, you can see how the relationships can get extremely complicated when you talk about sympathetic resonance, harmonics, etc...
The only way I can see that phasing is changed in a cabinet is IF a speaker does NOT conduct all frequencies the same. Even if a speaker has different impedance to different frequencies, this would affect the LEVELS of those differenct frequencies, but not their TIMING, correct???
The changing of time constants (resistance plus capacitance or inductance) only affects resistance in a frequency-specific way. That's how crossovers work to make something have HIGH resistance and some frequencies and LOW or NO resistance at others.
But even in such a case as this, you are just changing the relative proportions of frequencies, much like a tone stack might.
But you are NOT changing HOW LONG it takes one to get someplace relative to another frequency, which is necessary in order to have any phase change.
I can see, on paper, how series would be different than parallel wiring of a 2-speaker cab. In the parallel configuration, both drivers see the exact same signals. But in the series configuration, the "later" speaker sees a signal only after it has been "filtered" (if this exists) by the other speaker. Then again, when the current alternates the other way, the inverse happens, so the speakers still put out identical signals.
I wish I could see the lack of linearity that would cause a phase change in a multi-speaker cab.
Justin
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Post by billyguitar on Jun 6, 2006 12:41:20 GMT -7
Right over my little pointed head! Another consideration regarding different wiring schemes is something that Gerald Weber mentions in some of his writings, branch inductance. He says that will effect the sound of speakers in a cabinet. Didn't Ampeg use 32 ohm speakers in the SVT 8 x 10 cabinet so they could somehow end up with a usable impedance? I could be totally wrong but I'm a dancin' fool..............
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Post by Hohn on Jul 18, 2006 14:42:58 GMT -7
UPDATE: I looked it up online, and all else being equal, a 4x12 will be louder than a 2x12 because of the greater swept volume (and hence, air displacement).
JLH
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Post by billyguitar on Jul 18, 2006 15:22:06 GMT -7
"All else being equal" I'll bet you a donut that a stock Z Best 2 x 12 will be louder than a 4 x 12 with Greenbacks! Some speakers are more dished than others. What does that do to the swept volume? It's an interesting debate. One best decided by a/b testing.
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