Another Question About Matching an Amp Head with a Cabinet

I

ijq94

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May 17, 2016
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#1
Hi there everyone I have a simple question regarding matching an amp head with my new cabinet! I have an Acoustic B200H (head), which has two 1/4" speaker outputs (parallel I think) on the back to connect to the cabinet(s). It is rated at 200 watts @ 4 Ohms.

So my first question is; if I used both of the outputs on my head and connect them to the same cabinet (a cabinet at 4 ohms that also has two 1/4" speaker inputs) am I sending 100 watts @ 4 ohms from each output to my cabinet? So my total would be 200 watts into the cabinet? Or am I sending 200 watts @ 4 ohms from each output to my cabinet; so then my total would be 400 watts?

My second question is; if I only use one of the 1/4" speaker outputs of my head and connect it to a 4 ohm cabinet am I getting 200 watts @ 4 ohms? Or am I only getting 100 watts?








My third (not really a) question; my current setup is pretty much close to my dream rig.
IMG_20160526_212437.jpg
I have been looking for an Acoustic 360/361 since before I could play bass, I always thought Jonesy had one of the best tones for bass, and I always loved the way Acoustic gear has sounded. I luckily came across a super huge deal, this 361 HEAVILY MODDED cabinet. It is from the 70s, original 18" speaker, new white covered, wheels, metal handles kinda like and Ampeg has (thank you whoever did this, I am a small skinny dude, this is the heaviest thing I own), hard-mounted Shure condenser mic (forgot the exact model) place inside in the bottom where the power amp section was, the power amp was ripped out and the owner before me took it out so any amp head could be used with this cabinet! (I don't know if that bottom part of the 361 was called the power amp but that is what I am calling it). Also they replaced the back panel (pic soon) with a whole new setup, it has two Speakon inputs, and two 1/4" speaker inputs as well, and a volume control for a horn that is inside.

I took the cabinet to get maintenance by a music repair shop. And they were amazed by my cabinet, I still am, and it works perfectly.

So I just don't wanna be an ignorant (in the sense of of just being bliss) bassist who has no idea what I am plugging in and such. I just wanna make sure I am not gonna blow my cabinet, or mess something up, I wanna take good care of my gear and I just wanna ask someone who is more experienced.

Currently, I am only plugging in one of the 1/4" speaker outputs from my head into the cabinet but I wanna know if I could plug in both of them into the cabinet.​
 
#4
Just for emphasis, see post 2.
And for clarification,
There are two outputs on the amp just for a situation where you have maybe two 8ohm cabs and each only has one input.

Same with the cab... If your amp only had one output and could run another cab (not in your case though) you could use one of the other parallel connectors to hook to said second cab.

Your amp is only going to give you that 200 watt capability at 4 ohms (which your cab is). Any more speakers hooked up with that amp will drop your load below the stated minimum. If you had two 8 ohm cabs, you could use one or both (but no more) and be fine.
 
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#7
Juicyanalog said:
so, question...

2 bass speaker cabs....

bottom 1X15 400W rms 8 ohm
top 2X10 400W rms 8 ohm
Power needed (SS) to run both simultaneously/in-conjunction at 4ohm?
thx
Click to expand...
There is a myth about underpowering cabs. It's like the Loch Ness monster; a few people swear it exists, but science and rationale can't prove it.

Ideally, you don't want your power to exceed the lowest rated cab, to prevent blowing it out in the event you run the volume too high. Realistically, you can power a 250 watt cab with a 3000 watt power amp if you're very conscience of volume. My vocalist has a 2500 watt power amp into 500 watt mains- no issues at all.
 
#8
B-string said:
1 watt to 800 watts. How loud you need to be is the question.
Click to expand...

"1W to 800W"... Forgive me, but I don't understand that..and I am finding that statement ambiguous...

As far as the 'how loud I want to be' thing,... I would say headroom of three quarters of the way up the head,..with minimal distortion at that point ...( I think basically everybody wants that ..lol)
 
#9
blubass said:
There is a myth about underpowering cabs. It's like the Loch Ness monster; a few people swear it exists, but science and rationale can't prove it.

Ideally, you don't want your power to exceed the lowest rated cab, to prevent blowing it out in the event you run the volume too high. Realistically, you can power a 250 watt cab with a 3000 watt power amp if you're very conscience of volume. My vocalist has a 2500 watt power amp into 500 watt mains- no issues at all.
Click to expand...

Very interesting… I was told the opposite by prominent speaker techs.. Using my example,…I was under the impression that I needed at least 1200W to 1600W power output, to properly "Drive" that speaker configuration... I obviously asked again, because in practicality, I have doubts as well...
 
#10
Juicyanalog said:
"1W to 800W"... Forgive me, but I don't understand that..and I am finding that statement ambiguous...

As far as the 'how loud I want to be' thing,... I would say headroom of three quarters of the way up the head,..with minimal distortion at that point ...( I think basically everybody wants that ..lol)
Click to expand...

It is not ambiguous. You could practice by yourself with 1 watt or play to a large crowd outside with 800 watts. "Headroom" is not just a "buzz word", but a real misused term. The amount of "headroom" is determined by the amp output power against the maximum input wattage of the speaker cab.

Example with 1 watt of amp power and 800 watts of cab input capability you have 1 watt of headroom available. 1200 watt amp into 800 watt cabs you have 800 watts of headroom, over 800 watts burnout the cabs so they limit your "headroom".

Juicyanalog said:
Very interesting… I was told the opposite by prominent speaker techs.. Using my example,…I was under the impression that I needed at least 1200W to 1600W power output, to properly "Drive" that speaker configuration... I obviously asked again, because in practicality, I have doubts as well...
Click to expand...

Your "prominent speaker techs" need to learn their craft instead of repeating internet myths. JBL has white papers available on these subjects free for the search from their tech papers.
 
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#11
And be aware that an 800w amp puts out peaks much higher than 800w. Also 800w is a rose coloured glasses statistic for how much power a 115 and 210 can get through. It is a thermal rating which takes no account of the excursion required to generate the lower bass frequencies.
 
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#12
B-string said:
It is not ambiguous. You could practice by yourself with 1 watt or play to a large crowd outside with 800 watts. "Headroom" is not just a "buzz word", but a real misused term. The amount of "headroom" is determined by the amp output power against the maximum input wattage of the speaker cab.

Example with 1 watt of amp power and 800 watts of cab input capability you have 1 watt of headroom available. 1200 watt amp into 800 watt cabs you have 800 watts of headroom, over 800 watts burnout the cabs so they limit your "headroom".



Your "prominent speaker techs" need to learn their craft instead of repeating internet myths. JBL has white papers available on these subjects free for the search from their tech papers.
Click to expand...

ok..thanks for the info
 
#13
Downunderwonder said:
And be aware that an 800w amp puts out peaks much higher than 800w. Also 800w is a rose coloured glasses statistic for how much power a 115 and 210 can get through. It is a thermal rating which takes no account of the excursion required to generate the lower bass frequencies.
Click to expand...

ok...alot of that is over my head...but good info to know, no doubt
i just landed that mid 70's Jazz bass,
and i wanted to know a good match for my
Peavey 2x10 & 1x15 config (both 400w @ 8ohms)
that would drive them both properly
(the cabs would be crossed over properly as well...)

i really want this...
walter_woods.jpg
NOT happening...lol

im kinda leaning towards these at the moment...
ATH500.jpg
swr700.jpg
< used only:this is not made anymore

...but my wallet is pushing me towards this...lol
peavey_headliner_1000.jpg
< peavey headliner 1000

so, this is the tone(s) i'm kinda going after....
the "Straight to the Board, without being Sterile" tone..
any suggestions, enlightenments, criticisms, etc. welcome...
 
#14
There are two ways to kill a speaker. Heat and over excursion. A few milliseconds worth of too much heat is nothing that can't be absorbed in the next millisecond but a single overexcursion can start a tear in the cone.

Power of audio signals is dependent on the form of the wave and its voltage but not the frequency.

During a bass wave the speaker flys out for a longer duration of time. Ergo it travels way further doing it. The power is the same.
Juicyanalog said:
ok...alot of that is over my head...but good info to know, no doubt
i just landed that mid 70's Jazz bass,
and i wanted to know a good match for my
Peavey 2x10 & 1x15 config (both 400w @ 8ohms)
that would drive them both properly
(the cabs would be crossed over properly as well...)

i really want this...
walter_woods.jpg
NOT happening...lol

im kinda leaning towards these at the moment...
ATH500.jpg
swr700.jpg
< used only:this is not made anymore

...but my wallet is pushing me towards this...lol
peavey_headliner_1000.jpg
< peavey headliner 1000

so, this is the tone(s) i'm kinda going after....
the "Straight to the Board, without being Sterile" tone..
any suggestions, enlightenments, criticisms, etc. welcome...
Click to expand...
running full range bass cabs crossed over means carrying a lot of cab for little output.
 
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#17
Downunderwonder said:
There are two ways to kill a speaker. Heat and over excursion. A few milliseconds worth of too much heat is nothing that can't be absorbed in the next millisecond but a single overexcursion can start a tear in the cone.

Power of audio signals is dependent on the form of the wave and its voltage but not the frequency.

During a bass wave the speaker flys out for a longer duration of time. Ergo it travels way further doing it. The power is the same. running full range bass cabs crossed over means carrying a lot of cab for little output.
Click to expand...

wow...interesting... i was just trying to minimize the "woof" & increase the "tightness"...but ok
 
#20
Munjibunga said:
I was talking about running two cables from the head to the cab. However, as someone else said, crossing over two full-range cabs is kind of a waste of effort for little return.
Click to expand...

sorry bro..i dont mean to keep this going...and i appreciate this info (from everyone)
but this is news to me...
"dont" run 2 spkr cables from the head to the cabs???....i though the heads were 'made' for that?? {parallel outs}
 
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