Speakerage...


Raskolnikov
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Raskolnikov
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02/08/2003 11:49 pm
So, I have an Ampeg head that will hand a 2 ohm load (the Sunn died... bummer), anyway:

I also have a 2x15 4 ohm cabinet. I have a line on another 2x15 cab (a Traynor!) for about $110, word has it is in good condition, but the casters are MIA. However, it is running at 8 ohms.

Now, can I use both cabs in paralell as is? Is it possible to make the 8 ohm cab 4 ohms, and would it be better to use two cabs at 4 ohms a peice?
Raskolnikov
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# 1
Lordathestrings
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Lordathestrings
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02/09/2003 10:57 pm
Rask!... you forgot this?

I'm sorry to hear you no longer have 1200 Watts at your command.

8 Ohms parallel with 4 Ohms comes to 2.6 Ohms. If your Ampeg is transistor, it should be OK. If it's a tube amp, you should try to get a closer match to the output transformer tap selection.

The 8 Ohm Traynor 2x15 is probably loaded with a pair of 16 Ohm speakers wired in parallel. Back in the day, nobody was stuffing 15" 4 Ohm speakers into their cars, so they weren't very common. The 4 Ohm cab you already have, probably contains a pair of 8 Ohm speakers in parallel.

I can't think of any tidy way to combine these to get a better impedance match for a tube amp output transformer. Since both cabs have two 15" speakers, I suggest doing an A-B comparison, and keeping the cab you prefer. Then get another cab, like a 4x10, to match up with that 2x15 cab.

The Ampeg Forum may be helpful in choosing a good combination. The consensus seems to be that two cabs, with different speaker sizes, gives a better balance of 'punch' and 'thump'.
Lordathestrings
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# 2
Raskolnikov
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Raskolnikov
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02/09/2003 11:22 pm
I did forget "that," but the fact is, adding resistances never quite works out right in my head.

The Ampeg is a solid state amp from front to finish (::glaring in the general direction of Lafayette and therefore my head::)

I'm keeping both cabs no matter what for now. It's a lot smaller and lighter than my Peavey cab, so even if I can't use both at once, I can move it around easier, and it's better suited to small gigs.

Eventually I may replace the speakers with Black Widows so I can use both cabs at once, but I'm not going to even think about that right now. I got myself a vintage cabinet for $120 that sounds good, is in good condition and fixes some problems I've been having.

Well, thanks.

So I can't use both at once? Or can I?
Raskolnikov
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# 3
Lordathestrings
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Lordathestrings
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02/10/2003 12:30 am
Originally posted by Raskolnikov
...So I can't use both at once? Or can I?
Yes, you can use both at once. Your transistor amp's output stage is much less finicky about impedance matching than a tube amp would be. The net impedance will be 2.6 Ohms. That's pretty close to the 2 Ohm lower limit specified for your amp, but if it's healthy, and you don't turn everything up to 11 all the time, you should be OK.

What will happen is the amp will provide a certain amount of voltage to the speaker terminals. The speakers will each draw as much current as the voltage drives to them.

It may make more sense to you if you think in terms of water pressure (Voltage) and pipe size (Impedance). If you hook up two different diameter pipes to the same source, the larger pipe (lower impedance) will flow more (higher Current) than the smaller diameter pipe. This means more volume (Power) through the larger diameter pipe.

So, the lower impedance speaker cabinet will draw more current than the higher impedance cabinet. Since Power = Voltage X Current, and the voltage is the same for both cabinets, most of the power will go to the lower impedance cabinet. In the case of a 4 Ohm cab and an 8 Ohm cab, the 4 Ohm cab will get twice as much power as the 8 Ohm cab (same Voltage; twice as much Current). If your amp is putting out 300 Watts, the 4 Ohm cab gets 200 Watts, and the 8 Ohm cab gets 100 Watts. [u]Keep this in mind if your amp is capable of providing more than 1 1/2 times the rating of your 4 Ohm cab[/u]!

Look in on the Ampeg forum to see if anybody with the same amp has any suggestons for you. That forum doesn't have anywhere near as much traffic on it as this one, but it does offer a narrower focus on Ampeg products.

Happy thumping! :)
Lordathestrings
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# 4
Raskolnikov
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Raskolnikov
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02/10/2003 6:14 pm
Originally posted by Lordathestrings
So, the lower impedance speaker cabinet will draw more current than the higher impedance cabinet. Since Power = Voltage X Current, and the voltage is the same for both cabinets, most of the power will go to the lower impedance cabinet. In the case of a 4 Ohm cab and an 8 Ohm cab, the 4 Ohm cab will get twice as much power as the 8 Ohm cab (same Voltage; twice as much Current). If your amp is putting out 300 Watts, the 4 Ohm cab gets 200 Watts, and the 8 Ohm cab gets 100 Watts. [u]Keep this in mind if your amp is capable of providing more than 1 1/2 times the rating of your 4 Ohm cab[/u]!


Last night I dug out my talkbox (for the extra speaker cables I keep with it) and tried plugging the both in. It worked, but I definately noticed my 4 ohm cab was louder. My amp only puts out 600 some odd watts at 2 ohms (bearing in mind the Sunn put out 1200 watts at that same impedance), so I'm not worried about overloading my 4 ohm cab. I'm woried about getting evicted.

Thanks!
Raskolnikov
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# 5
Lordathestrings
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Lordathestrings
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02/10/2003 11:23 pm
Originally posted by Raskolnikov
Last night I dug out my talkbox (for the extra speaker cables I keep with it) and tried plugging the both in. It worked, but I definately noticed my 4 ohm cab was louder. My amp only puts out 600 some odd watts at 2 ohms (bearing in mind the Sunn put out 1200 watts at that same impedance), so I'm not worried about overloading my 4 ohm cab. I'm woried about getting evicted.

Thanks!
With 600 Watts applied to the pair of cabinets, your 4 Ohm cab will get 400 Watts. The 8 Ohm cab gets 200 Watts. If your cabs are rated for that much power, rock on!

Evicted! :eek: Some landlords just have a warped sense of priorities.
Lordathestrings
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# 6
Lordathestrings
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Lordathestrings
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04/21/2004 3:03 am
I recommend reading this thread for some help in making sense of it.
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# 7
iamthe_eggman
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iamthe_eggman
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04/21/2004 3:19 am
Originally Posted by: LordathestringsI recommend reading this thread for some help in making sense of it.


Hmmm... So that's what a year's worth of research looks like....
... and that's all I have to say about that.

[U]ALL[/U] generalizations are [U]WRONG[/U]

[/sarcasm]
# 8
kingdavid
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kingdavid
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04/21/2004 12:06 pm
It's been a while since Rask said anything,so it's good to see you're still around.
And that quoting thing you and Lorda have going there takes me back to some very interesting times I had a while back with you guys regarding Dubya(that's a name I picked up from one of Pony's threads).
We should look for another controversy and have another ball!!(After Bush,girl guitarists and the Beatles,I can't quite come up with something vroomy!!,if you know what I mean).I must however hasten to add that I don't start a thread just to argue,but if we end up with something engaging,I DON'T MIND!! :D
# 9
iamthe_eggman
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iamthe_eggman
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04/21/2004 2:31 pm
Originally Posted by: kingdavidIt's been a while since Rask said anything,so it's good to see you're still around.
And that quoting thing you and Lorda have going there takes me back to some very interesting times I had a while back with you guys regarding Dubya(that's a name I picked up from one of Pony's threads).
We should look for another controversy and have another ball!!(After Bush,girl guitarists and the Beatles,I can't quite come up with something vroomy!!,if you know what I mean).I must however hasten to add that I don't start a thread just to argue,but if we end up with something engaging,I DON'T MIND!! :D


Hmmm.. you might wanna go back and check the dates of those posts...
... and that's all I have to say about that.

[U]ALL[/U] generalizations are [U]WRONG[/U]

[/sarcasm]
# 10
kingdavid
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kingdavid
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04/22/2004 11:38 am
I get into the forum by going straight to it(tricks.com/forum),then signing in,then clicking on new posts since I last logged in.This thread came up.I suppose it's a problem arising from after the forum changed or something,although I'm thinking it shouldn't coz the data stored stored in the forum database hasn't changed,it's just how it's presented to us that has changed. :confused:
*Shrug*
# 11
iamthe_eggman
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iamthe_eggman
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04/22/2004 2:27 pm
Originally Posted by: kingdavidI get into the forum by going straight to it(tricks.com/forum),then signing in,then clicking on new posts since I last logged in.This thread came up.I suppose it's a problem arising from after the forum changed or something,although I'm thinking it shouldn't coz the data stored stored in the forum database hasn't changed,it's just how it's presented to us that has changed. :confused:
*Shrug*


There's no problem with the forum... What happened is that Lord replied to a thread that was a year old. His latest post was 4/20/04, but the post directly before that was 2/10/03.

The reason I said "check the dates of the posts" was that you had taken this thread being active as meaning that Rask had posted recently, but it was a case of Lord reviving an ancient thread. I don't think Rask has posted in a long while yet....

BTW, did you ever read that post I made in the "Beer!" thread, where I lauded the virtues of Tusker?
... and that's all I have to say about that.

[U]ALL[/U] generalizations are [U]WRONG[/U]

[/sarcasm]
# 12

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