i need some educating on speaker cabs

[treymonfauntre]

i knew i should have known better

last december i was in a hurry for a bass cab, so i ordered a 2x10 from "steel sound", they had them clearanced for $80 cause they were changing names to legion sound. legion sounds email does not work.
one of the speakers that came with my 2x10 is completely dead and always has been. i'm so dense that i just didn't use the cab because i couldn't figure out why it sounded so bad. i thought it was just the horn. today i finally got time to take off the grill and much to my dismay the speaker isn't making any noise and the dust cover on the speaker is totally stiff and doesn't give in at all like the other speaker.

i really don't know what i'm talking about here, as you can see. is this what a recone fixes? these are probably some cheap ass speakers and i'm more than willing to buy new ones. any suggestions? i also have a 15" cab that i wouldn't mind getting a new speaker for.

[Farview]

Eminence makes good stuff for bass. It isn't overpriced either.

[treymonfauntre]

another question, the cab is 300w at 8ohms, but each speaker is 16ohms. does that means its wired parallel? at the same time, if one speaker isn't working, would that mean that the one 10" speaker that works has been looking for a 16ohm load?
the reason i ask is because i've been using a 150w 8ohm 15" speaker under the cab. i know the power mismatch is dumb but would the ohm mismatch be even worse? what watt/ohm replacements should i get? my amp head is 300w at 4ohms so i guess i should match that.

[Farview]

It depends on why the speaker doesn't work. If the speaker is just not able to move but the signal is going through the coil, the impedance is 8ohms. If the speaker is disconnected or the coil is shorted, you have a 16ohm cab now.

Don't worry about the power of each cabinet. When you hook both up, the power handling adds together.

[treymonfauntre]

am i correct in saying that 2 16ohm speakers wired in parallel make 8ohm? or is that something else?
if i got a 4ohm 15" speaker and 2 8ohm 10"s that would give me the right impedence?

[Farview]

Yes, 2 16 ohm speakers in parallel is 8 ohms. It gets more complicated when you have different impedences mixed. The formula for parallel wiring is
(Za x Zb)/(Za + Zb) = total Z 'Z' is impedance, a and b are the different speakers. With a 4 ohm and an 8 ohm cabinet wired in parallel, you would end up with a 2.6 ohm load. Probably not a good idea.

Your 4 ohm 15 and and 8 ohm 10s would get you down to 2 ohms. If you wired the 10's in parallel and wired the 15 cab and the 10 cab in series, you would end up at 8 ohms.

[treymonfauntre]

you've been extremely helpful
now can you help me clarify in series? my amp head has 2 outputs, my 2x10 has 2 jacks, and my 15" has 2 jacks. i've just been running one cable from each output on the amp head into the left jacks on the cabs. would series mean i run the output of the amp to the 2x10, and then run the right jack into the 15"?

[ggunn]

Originally Posted by Farview

It depends on why the speaker doesn't work. If the speaker is just not able to move but the signal is going through the coil, the impedance is 8ohms. If the speaker is disconnected or the coil is shorted, you have a 16ohm cab now.

Not exactly; when a voice coil is not free to move, it's essentially a resistive load, which is somewhat less than the 8 ohm reactive load of a moving voice coil. Also, if the voice coil were jammed but still passing current, it wouldn't be that way for long before it burned out.

If the voice coil were shorted (not likely), it wouldn't be a 16 ohm cab, it would be a zero ohm cab.

[Farview]

Originally Posted by ggunn

Not exactly; when a voice coil is not free to move, it's essentially a resistive load, which is somewhat less than the 8 ohm reactive load of a moving voice coil. Also, if the voice coil were jammed but still passing current, it wouldn't be that way for long before it burned out.

YOu got me on that. I didn't think it all the way through.

[ggunn]

Originally Posted by Farview

YOu got me on that. I didn't think it all the way through.

Jeez, you're fast; you missed my edit! ;^)

[Farview]

Originally Posted by treymonfauntre

you've been extremely helpful
now can you help me clarify in series? my amp head has 2 outputs, my 2x10 has 2 jacks, and my 15" has 2 jacks. i've just been running one cable from each output on the amp head into the left jacks on the cabs. would series mean i run the output of the amp to the 2x10, and then run the right jack into the 15"?

Both of those would be running in parallel. In order to run the cabinets in series, you would have to make a special cable snake wired in series.

The 4 ohm 15 is what is screwing up the works. If you had an 8 ohm 15, you would be in great shape.

[treymonfauntre]

well, i do have one, but its 150w. its peak power is 300w, if i'm only playing for 10/15 minutes at a time do i run the risk of destroying it?

[ggunn]

Originally Posted by treymonfauntre

well, i do have one, but its 150w. its peak power is 300w, if i'm only playing for 10/15 minutes at a time do i run the risk of destroying it?

Blowing up a speaker by overpowering it is most commonly an instantaneous event, like forcing the voice coil to exceed its excursion limit. OTOH, just because you are playing through a 300w amp doesn't mean that you are using all 300 watts.

[treymonfauntre]

hah, alright
so if i were to get 2 8ohm 10" speakers i would be fine?

[Farview]

Not unless your amp can go down to 2 ohms. Most amps like to be at 4 ohms or above. If you start out with a 4 ohm cabinet, you can't add any more speakers. Like I said before, if you are using the 10s and the 15, you won't blow any of them. Hell, you won't blow the 15 unless you turn the amp all the way up. The speaker will start distorting long before it burns up, that will be an indication that it is too loud.

[VSpaceBoy]

How about this, post your amp and/or specs. We'll tell you what speakers to look at.

Also remember, when you mismatch speaker impedance, the one will the lower will get more power. In the case of the larger speaker with the lower it might sound good, but not the other way around.

[treymonfauntre]

hah, well heres the specs again:

amp head: 300w @ 4ohms http://www.gallien-krueger.com/produ..._hd_600bl.html
15" cab: 4ohms, 150rms 300peak
current 2x10: 16ohms, 300rms 600peak

i've been playing with just the 15 for a while and its just barely loud enough, but i'd prefer to have some 10s filling in the top end since i'm playing this in a funky 2 man drum/bass band and need lots of midrange.

[VSpaceBoy]

ok well, if it was me I would not use the 15" at all. (at least until you get another power amp). Get two DELTA 10's and wire them 4ohms.

300w still may not be loud enough for what your after though.

[Farview]

I would get a 4x10 and dump everything you have now.

BTW, I thought your 2X10 was 8 ohms?

[treymonfauntre]

each speaker is 16ohms but the spec sheet says its 8ohms so i guess its wired parallell

[treymonfauntre]

and i have to play a show tomorrow and only have about a hundred bucks to blow on speakers
unless my friend will let me borrow his hartke 4x10 combo, which i don't really like

[Farview]

$100 won't get you anywhere with speakers. Save up and get a decent cabinet. If you can find one that is 8 ohms, you can always get another one in the future.

[Thatupstateguy]

If I am reading this whole thing right,..... you are loading your amp with one cab that is an 8 ohm load,... then adding another that is a 4 ohm load,....and your amp head is an output of 4 ohms,....... is this correct so far.???



if so,.... what you are doing by using both cabs at once, is adding the two together giving you an ohm load of 12 ohms,.... and since your amp has an output of 4 ohms, you are taking an awful chance of overheating your amp,....

the proper thing to do is to match the output of your amp,... that way when you want to use it for it's 300 watts, you will at least have that to work with,....

the problem is,... when you add more speakers,.... if you use other plugs on the back of your amp,.... you are adding ohms together for one output,.....


Try plugging the 4 ohm 15" as a piggy-back to the twin 10",.... by daisy-chaining the cabs, you are running them at a lower ohm load than doing it the other way,....


and as for the one 10" not working,..... double check the solder connection,.... and try taking a piece of zip cord, (common two lead wire),... and while a signal is being fed to the cab,... take the zip cord, and touch the contacts from the other speaker,.... if you get signal,.. it could be the connection, the soldering, or the wire,..... if no signal,.... it could be the voice coil,... but a speaker not working right from the factory sounds to me like a warrenty thing,... or at the very least,.. a replacement at no cost,....


I would keep trying to contact the place where you bought the cab.....


Steve

[ggunn]

Originally Posted by Thatupstateguy

If I am reading this whole thing right,..... you are loading your amp with one cab that is an 8 ohm load,... then adding another that is a 4 ohm load,....and your amp head is an output of 4 ohms,....... is this correct so far.???



if so,.... what you are doing by using both cabs at once, is adding the two together giving you an ohm load of 12 ohms,.... and since your amp has an output of 4 ohms, you are taking an awful chance of overheating your amp,....

the proper thing to do is to match the output of your amp,... that way when you want to use it for it's 300 watts, you will at least have that to work with,....

the problem is,... when you add more speakers,.... if you use other plugs on the back of your amp,.... you are adding ohms together for one output,.....


Try plugging the 4 ohm 15" as a piggy-back to the twin 10",.... by daisy-chaining the cabs, you are running them at a lower ohm load than doing it the other way,....


and as for the one 10" not working,..... double check the solder connection,.... and try taking a piece of zip cord, (common two lead wire),... and while a signal is being fed to the cab,... take the zip cord, and touch the contacts from the other speaker,.... if you get signal,.. it could be the connection, the soldering, or the wire,..... if no signal,.... it could be the voice coil,... but a speaker not working right from the factory sounds to me like a warrenty thing,... or at the very least,.. a replacement at no cost,....


I would keep trying to contact the place where you bought the cab.....


Steve

Hmmmm, there's a bit of disinformation here.

1) When you add speakers to an amp, they nearly always (maybe always always) add them in parallel, not series, so connecting a 4 ohm cab with an 8 ohm cab is not a 12 ohm load, it's more like 3 (too early in the morning to do the math, but 3 ohms is close). A rule of thumb is that a combined load in parallel is ALWAYS lower in ohms than the lowest impedance single load.

2) It makes no diff whether you plug the second cab into the second output on the amp or the parallel connection on the first cab, it's the same connection and gives you about 3 ohms.

3) The risk to an amp is in having a load of less ohms than the spec, not more. Do not give a 3 ohm load to an amp which is spec'ed at 4 ohms.

4) If you do what was suggested and go poking around with a test wire while the amp is running BE VERY CAREFUL. If you touch the wrong connector and short out the load, it can damage your amp VERY QUICKLY.

5) An amp does not "output" ohms, it puts out current at a voltage; the impedance (ohms) is dictated by the load.

[ggunn]

If you are looking for a quick and cheap stopgap measure, open the two speaker cab and cut the wires to the non-working speaker. Make sure that the cut ends cannot touch anything (tape them off). Now it is a 16 ohm cabinet (assuming that we are correct in that what you have is two 16 ohm speakers in parallel) Connect the single speaker 8 ohm cab. That will give you a 6 or 7 ohm load, well within the comfort range of the amp.

Now, the 8 ohm speaker will dissipate more of the amp's power than the 16 ohm speaker; it will get 2/3 of it and the 16 ohm speaker will get 1/3. For a 300 watt amp, that's 200 and 100 watts, assuming that the amp is running at max power. If the 8 ohm speaker is spec'ed at 150 watts, there is a potential prob, although the power limits on a speaker tend to be quoted conservatively. If you back off on the amp a bit from maxxed out, you will probably be OK.