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Mixing Ampeg Cabinets

F

Flaminio

Feb 29, 2012
6
0
52
#1
I have an Ampeg SVT 410hlf and using an Ampeg SVT Classic head. I just picked up an Ampeg 215e in near perfect condition for $150. I couldn't pass it up. Can I or do you foresee any issue if I mix the cabs and run both the 410 & 215 together. I played them both in our practice space but I haven't played out with that combo yet.

Any feedback would be appreciated.

Thanks..
 
#2
Hey Flamino,

The main thing that you have to be aware of is the lowest ohm load the head can handle and the ohm load that both cabs put on the head.

I'm not familiar with those pieces so I can't help you specifically but I'm sure someone else will.

I can explain impedance to you with a pretty good analogy but it's too much to type on an iPhone with one finger.

Email me your number and I'll call you.

peace,
anthony
 
#3
Hey Flaminio!

The SVT Classic is meant to run at either 2 or 4 ohms. The SVT 410HLF is a 4 ohm cab, so using it alone with the head would be fine. I can't find the 215e cab on Ampeg's website, so I'm not sure what ohm load it runs. Check on the back of your cabs; if they're both 4 ohm cabs, you'd be running a 2 ohm load, which would be fine, but if the 215e is a 8 ohm cab, running them both would result in a 6 ohm load, which your amp would NOT be happy with and could potentially damage your setup.

Hope this helps!

-Joe
 
#4
The 215 is a 4ohm cab. Its not a problem to run both add the SVT CL can handle it at 2 ohms. I'm more concerned with potential phasing issues. Both cabs go down to 28hz so the frequency should be similar. Just not sure about any delay phasing.
 
#6
I fired them up and it sounds INCREDIBLE!!! Unfortunately, I was really to close to them (10') to really hear any potential issues. I've always played with (2) 410 cabs and split the stage left and right. I'm not sure i want to do that with this set up since they're different. I think I'll stack them together and make the guitarists mad!!!!! lol
 
#7
With speaker cabinets and amps, as Ant pointed out, you have to be careful not to drop the total impedance of the load (your speakers) below that which the amp can handle. This rule mainly applies to SOLID STATE amplifiers which can be damaged (blown) by too much load (too low an impedance). Presenting too much load to a tube powered amp (not an amp with only a tube pre - an amp with a tube power section) is much less likely to lead to fireworks, the main result here will be distortion. The output transformer in a tube amp will simply reflect the lower impedance back to the tubes, which will cause them to operate at less than optimal efficiency and with altered frequency response. Unless you present a dead short to a tube amp, you're not terribly likely to damage the amp the way you would a solid state amp, which could potentially wind up needing new power transistors.

As I'm sure many people know, the total impedance of your load when you PARALLEL the speaker cabinets is easy to figure out. If you have two 8 ohm cabinets, in parallel they are 4 ohms. If you have two 4 ohm cabinets, in parallel they are 2 ohms. If you have an 8 and a 4 ohm cabinet and you parallel them, you get 2.7 ohms and the 8 ohm cab is likely to be half as loud as the 4 ohm if they are of the same efficiency (a whole different discussion).

If your amp is solid state, DO NOT go below the minimum impedance specified on your amp. At a minimum, the amp will get much hotter and sound more distorted. Worst case is you blow the whole output section and are looking at a couple hundred dollar repair (about what I charge to fix a power section in a solid state amp). In a tube amp, you can go lower than specified, but you'll probably not like the result. It's not likely, but it is possible to damage the amp.

As to the phase issue, you're not likely to encounter problems here unless the cabinets are of different design (a front-loaded and a folded horn for example). There is always the possibility that one was wired incorrectly inside and that happens from time to time when people wrongly assume that it doesn't matter which wire goes on the positive and negative terminals. An easy test to make sure your two cabinets are in phase with one another is the old 9-volt battery test. Please read CAREFULLY before attempting this:

1) Find a way to directly connect a 9-volt battery to your speaker cabinet's input. Obviously banana lugs work for this, and a 1/4" cable will work too if you touch the tip to the positive terminal and the shield to the negative. If you have Neutrik connectors, you'll need a spare connector or a butchered cable to do this.
2) While standing in front of the cabinet and observing the speaker cone(s) BRIEFLY and I mean BRIEFLY touch the battery to the terminals - make sure you use the correct polarity on the battery.
3) When the battery touches the terminals, the speaker will thump, and the cone will move visibly in one direction, either in or out. In most cases (except most notably old JBL) the speaker will move outward when positive voltage is applied to the positive terminal.
4) Do this test on both cabinets. If they move the same direction, the cabinets are IN PHASE. If they move in opposite directions, they are OUT OF PHASE with each other.

If they are out of phase with each other, this can be corrected by opening the cabinet and reversing the wires to the speaker. Also, if you have a 2x10 or 4x10 cabinet that just doesn't seem to sound right, check that all the speakers are in phase. You'd be amazed at how many cabs I see where a speaker got replaced and hooked up backwards.

ONLY TOUCH THE BATTERY TO THE SPEAKER BRIEFLY!!!



Hope this helps!


Jamie
 
#9
Man, I do get long-winded on replies, but that's just my nature. I have been using computers since I was a kid (and computers had like 1KB of ram) and I type REALLY fast. Couple that with having a thousand thoughts per second, and you get a phone book where a pamphlet was expected...

By the way, I do realize full well that this is the "Ask Anthony Wellington" Forum, so if I ever overstep my bounds, please feel free to let me know. No offense will be taken. I am eager and full of zeal at times. I'm not trying to show off what I know, I just really like helping people out, and I like information to be complete - as if somebody more expert than me on a given subject was grading my paper! I even go back a re-read my posts to make sure I didn't screw anything up.

That's just who I am, not trying to prove anything!


Jamie
 
#10
Hey guys! Sorry I posted misleading info on here; apparently I don't understand impedance as well as I thought. So, Jamie (or Ant, as this is YOUR forum), just to make sure I don't lead anyone down that dark trail toward blowing their rig up, could you give me the crash course in brain surgery on the whole impedance thing? I thought that if you daisy-chained a 4 ohm and 8 ohm cab, the ohms the amp would "see" would be 6 ohms? Correct, incorrect, totally ignorant? I'm not sure anymore! :help: Does the 2.7 ohm resistance only result when using the cabs hooked up straight to the head (i.e., using both speaker outs)? I'm confused! I used to think I knew, but obviously, I have much to learn. :(
 
#11
Resistance in parallel = 1/(1/R1+1/R2)= 2.66 ohms, this would be like connecting your amp to your cab if you had two speaker outs, one to each cab. The daisy chain or parallel setup that you speak of is R1 + R2 = 12 ohms. As longs as you head is capable of safely handling 2 ohms, you should have a problem. Hope this helps.
 
#12
Okay, I'll answer this since its wordy, and Ant is on the road (I think). So here goes. First, throw out the term 'daisy chain'. It's ambiguous and means nothing in electrical terms. There are three ways to connect speakers in circuit; series, parallel, and series-parallel.

In a series circuit, electrons flow from the source and through each device sequentially, then to ground or the opposite end of the source. A perfect example of a series circuit is a stack of batteries in a flashlight. The voltage flows from the negative terminal of the battery into the positive terminal of the battery next to it, out the negative terminal of the second battery to the positive terminal of the third, etc. Yes, electrons flow from negative which only makes sense when you stop and recall that an electron has a negative charge. Speakers are AC not DC, so + and - refer to polarity not direction of current flow with speakers, so don't let this extra info confuse you. Anyway, if you hook two speakers in SERIES, which is NOT accomplished by jumpering a wire from one cabinet to the next or 'daisy chaining' and almost always parallels your load, it will cause the total impedance to be simply the sum of all the speakers' impedance. Speaker 1 + Speaker 2, etc...

In a parallel circuit, the formula is a little more complex. Wiki search it if you want the exact recipe for a parallel circuit's resistance or impedance. The easy recipe that applies to situations where the impedance of two loads is the same (when you add a second speaker of the same impedance) is that it becomes one half of the impedance of one speaker. If you add a second door at a nightclub that is the same size as the first, twice as many people get through in the same amount of time because the impedance is half. Simple, right?

Okay, so the last situation is series-parallel. If I have four speakers and they are 8 ohms each and I parallel them, I wind up at two ohms. 2 ohms is too low for most amps. If I take two of the same speakers and wire them in series, I get 16 ohms, right? Well if I take two series wired pairs of speakers, each 16 ohms, and then I connect those pairs to each other in parallel, I'm magically back at 8 ohms! Lots of cabs are wired this way.


I hope that clears things up.


One more thing - a resistance meter, even though it measures in ohms, will not tell you accurately what the impedance of a speaker is. DC resistance and AC impedance are similar, but impedance, because it is AC, is frequency dependant. AC will react differently in a coil than DC will. That's a whole 'nother topic, there...


Jamie




Kermin VH said:
Hey guys! Sorry I posted misleading info on here; apparently I don't understand impedance as well as I thought. So, Jamie (or Ant, as this is YOUR forum), just to make sure I don't lead anyone down that dark trail toward blowing their rig up, could you give me the crash course in brain surgery on the whole impedance thing? I thought that if you daisy-chained a 4 ohm and 8 ohm cab, the ohms the amp would "see" would be 6 ohms? Correct, incorrect, totally ignorant? I'm not sure anymore! :help: Does the 2.7 ohm resistance only result when using the cabs hooked up straight to the head (i.e., using both speaker outs)? I'm confused! I used to think I knew, but obviously, I have much to learn. :(
Click to expand...
 
#13
dDaddybass said:
Resistance in parallel = 1/(1/R1+1/R2)= 2.66 ohms, this would be like connecting your amp to your cab if you had two speaker outs, one to each cab. The daisy chain or parallel setup that you speak of is R1 + R2 = 12 ohms. As longs as you head is capable of safely handling 2 ohms, you should have a problem. Hope this helps.
Click to expand...
,


That's not quite correct. See my previous post. The first example and the formula you gave is correct if you have an 8 ohm and a 4 ohm speaker connected in parallel. Thanks for providing the formula, I omitted it just for simplicity but that is the correct formula and necessary if you have more than two speakers or they have different impedances.

The second formula you cite would equal 12 ohms only if both speakers are 6 ohms and you connect them in series, not parallel.

Just wanted to clear that up.


Jamie
 
#14
dDaddybass said:
Resistance in parallel = 1/(1/R1+1/R2)= 2.66 ohms, this would be like connecting your amp to your cab if you had two speaker outs, one to each cab. The daisy chain or parallel setup that you speak of is R1 + R2 = 12 ohms. As longs as you head is capable of safely handling 2 ohms, you should have a problem. Hope this helps.
Click to expand...

Sorry, I meant series in the second situation. Daisy chain/series is R1 + R2= Rt or 4 ohms + 8 ohms = 12 ohms.
 
#15
dDaddybass said:
Sorry, I meant series in the second situation. Daisy chain/series is R1 + R2= Rt or 4 ohms + 8 ohms = 12 ohms.
Click to expand...

Yeah, that's the ticket. I don't know why I failed to assume an 8 and 4 ohm cab in the second scenario and went with 6 ohms (they do exist). I think we shared a brain fart there.


J.
 
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