Are you asking the resulting nominal impedance? 12 ohms. in series you just add 'em up.
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Ohms FAQ
- Thread starter IvanMike
- Start date
Are you asking the resulting nominal impedance? 12 ohms. in series you just add 'em up.
Hey guys,
To begin, I have a Hartke HA3500 amplifier and a DIY cabinet with 2x12" 8 ohm Celestion green label speakers. The speakers are wired parallel so it's a 4 ohm cabinet.
But now, I want to expand my gear.
My plan was to make an extra small cab with two 10" eminence LEGEND BP102-4 speakers. These are 4 ohms each.
But.. I don't know anything about ohms and stuff so that's the reason I post this. My head has 1x4ohm output or 2x8ohm output.
Is it possible to make that cabinet and plug it in to my amp without ruing my amplifier? Or is it possible to get my 2x12" cab to 8ohm in total?
I hope it will work, but i'm not sure. I hope someone of you guys might find the answer.
C.
To begin, I have a Hartke HA3500 amplifier and a DIY cabinet with 2x12" 8 ohm Celestion green label speakers. The speakers are wired parallel so it's a 4 ohm cabinet.
But now, I want to expand my gear.
My plan was to make an extra small cab with two 10" eminence LEGEND BP102-4 speakers. These are 4 ohms each.
But.. I don't know anything about ohms and stuff so that's the reason I post this. My head has 1x4ohm output or 2x8ohm output.
Is it possible to make that cabinet and plug it in to my amp without ruing my amplifier? Or is it possible to get my 2x12" cab to 8ohm in total?
I hope it will work, but i'm not sure. I hope someone of you guys might find the answer.
C.
billfitzmaurice
Commercial User
- Sep 15, 2004
- 16,860
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- Owner, Bill Fitzmaurice Loudspeaker Design
The answer lies at the beginning of this thread, which specifically exists so that you don't have to ask this question to begin with. Read the thread from the first page.
Short answer (if you are not looking to learn here) You can't do that.
Wow that hurts my brain to read .Thanks for the info
an electrical enginerr i used to work with found away to simplify this on paper.. sucks that i lost that piece of paper it made wiring cabnents so much ezier
So much knowledge in this thread, amazing. However I'm on my third bottle of aspirin. I read about eight pages and think I'm about as knowledgeable as I started... here's my question. I'm concerned about mismatching considering the issues with plate voltage, and I'm thinking what I'm planning on doing is a recipe for smoke. I have a 400+ that I run an ampeg 6x10 with. I just picked up (from a forum member) 2 old ampeg pa cabs rated at 16ohms. 4x10 and two tweeters. I love the idea of the tall thin cabs and would happily respeaker/rewire to make the 14 10" speaker result work. Any way this could without turning my Mesa into junk?
Would need to know the impedance of each driver in the two 410 cabs. I neleive the 610 is a 5 ohm cab?
IvanMike -
I would correct the definition of impedance.
Impedance includes resistance, inductive reactance and capacitive reactance,
not inductance and capacitance.
Good submission!
I would correct the definition of impedance.
Impedance includes resistance, inductive reactance and capacitive reactance,
not inductance and capacitance.
Good submission!
I would add this. Think about the word "impedance" and the word "impede". If you understand what impeding something means, then you understand that less impedance means more current (and power) and more impedance means less current (and power).
So many posters are confused by the concept of impedance and "less ohms=more power". If they stopped and thought about the words, I'm sure they would be less confused.
So many posters are confused by the concept of impedance and "less ohms=more power". If they stopped and thought about the words, I'm sure they would be less confused.
Some considerations that is confusing (I think).
Last night I did some impedance measurements to my 212 cab.
The cab is rated to be a 4 Ohm nominal. The speakers are Beyma 12LW30/N rated 8 Ohm nominal with a minimum of approximate 7 Ohm.
At first I measured Zmax of the 212's cab:
Zmax: 24,7 Ohm at 75 Hz.
I compared this to the cab simulation that is saying 27 Ohm at 78 Hz.
Knowing that a real speakers behavior is most of times a little bit different to ideal factory specs I'd say my cab's real impedance is identical to the impedance simulated for the cab.
All in all the frequency band 50..200 Hz shows a significant greater average value then the rated 4 Ohm.
At next I gave different stimulus of pink noise with different bands to the cab and measured U(rms) and I(rms) and calculated the impedance.
Pink-Noise:
40..1000Hz
Z = 7 Ohm
100..1000Hz
Z = 5,4 Ohm
100..500Hz
Z = 5,2 Ohm
200..800Hz
Z = 5 Ohm
Note:
for the band 200..800Hz I'd expected near 4 Ohm but the result was 5 Ohm.
Maybe there was some error in the meters accuracy cause I used a normal non clipped pink noise with 10dB Peak To RMS. Normally for audio measurement techniques the stimulus pink noise is clipped to +6dB Peak To RMS Ratio which is then low enough to capture by most common TRMS meters like Fluke 185/187.
But never the less there is a clear context between signal and cab impedance.
Interesting is the result for the band of 40..1000Hz.
Most amount of the pink noise energy is placed in the lower frequencies band 40..200Hz, thus the strong average range 40..200Hz with it's maximum 25 Ohm at 75Hz becomes dominant.
Have a look to the frequencies spectrum of a bass guitar for note E0.
The fundamental can be neglected cause it is weak normally.
The most powerful Harmonic is the second one at 82 Hz. And above 82Hz the Harmonic with 124 Hz even is strong but, reduced a little bit. And so going on and on ...
If the note E0 is played to the cap and all the EQ settings and tone controls are all flat the resulting impedance of the cab will be something about 4..5 Ohm.
Allthough there is some frequencies content with powerful Harmonics in the band 40..150Hz this band would not become strong enough to become dominant. Cause a very lot of power is in the band above/greater 150Hz as well.
The situation runs very different when the eq is used.
Bump the bass frequencies by +12dB and then the impedance of the cab runs out of order.
The low harmonics become very dominant in the frequncies power spectrum and thus the impedance between 50..150Hz becomes a dominat impact.
Allthough the cab is rated to 4 Ohm nominal the real world shows now approximate 8 Ohm for the note E0.
I never measured by now what is going on whenever I use my 70's SVT with the 212 cab.
Considering my prefered eq settings then all I'm knowing is that the impedance of the 212 cab will not be a 4 Ohm one.
I'd assume something like 6 Ohm.
That's nothing to talk home about I think!
Even with a strong bass boost sound and then resulting 8 Ohm for the cab I would not bother about it here.
But I'm shure a lot of users drive heavily bass boosted sounds with valve amps ....
There is a guy named Paul Apollonio who wrote some researches related with the Ohm question.
read the following and enjoy:
http://www.audioholics.com/education/loudspeaker-basics/loudspeaker-power-handling
Invalid Link Removed
http://www.audioholics.com/educatio...akers-power-ratings-part-iii-the-test-results
It's rather a question of power dissipation indeed but the theory of impedance is a big manner even in this way.
Last night I did some impedance measurements to my 212 cab.
The cab is rated to be a 4 Ohm nominal. The speakers are Beyma 12LW30/N rated 8 Ohm nominal with a minimum of approximate 7 Ohm.
At first I measured Zmax of the 212's cab:
Zmax: 24,7 Ohm at 75 Hz.
I compared this to the cab simulation that is saying 27 Ohm at 78 Hz.
Knowing that a real speakers behavior is most of times a little bit different to ideal factory specs I'd say my cab's real impedance is identical to the impedance simulated for the cab.
All in all the frequency band 50..200 Hz shows a significant greater average value then the rated 4 Ohm.
At next I gave different stimulus of pink noise with different bands to the cab and measured U(rms) and I(rms) and calculated the impedance.
Pink-Noise:
40..1000Hz
Z = 7 Ohm
100..1000Hz
Z = 5,4 Ohm
100..500Hz
Z = 5,2 Ohm
200..800Hz
Z = 5 Ohm
Note:
for the band 200..800Hz I'd expected near 4 Ohm but the result was 5 Ohm.
Maybe there was some error in the meters accuracy cause I used a normal non clipped pink noise with 10dB Peak To RMS. Normally for audio measurement techniques the stimulus pink noise is clipped to +6dB Peak To RMS Ratio which is then low enough to capture by most common TRMS meters like Fluke 185/187.
But never the less there is a clear context between signal and cab impedance.
Interesting is the result for the band of 40..1000Hz.
Most amount of the pink noise energy is placed in the lower frequencies band 40..200Hz, thus the strong average range 40..200Hz with it's maximum 25 Ohm at 75Hz becomes dominant.
Have a look to the frequencies spectrum of a bass guitar for note E0.
The fundamental can be neglected cause it is weak normally.
The most powerful Harmonic is the second one at 82 Hz. And above 82Hz the Harmonic with 124 Hz even is strong but, reduced a little bit. And so going on and on ...
If the note E0 is played to the cap and all the EQ settings and tone controls are all flat the resulting impedance of the cab will be something about 4..5 Ohm.
Allthough there is some frequencies content with powerful Harmonics in the band 40..150Hz this band would not become strong enough to become dominant. Cause a very lot of power is in the band above/greater 150Hz as well.
The situation runs very different when the eq is used.
Bump the bass frequencies by +12dB and then the impedance of the cab runs out of order.
The low harmonics become very dominant in the frequncies power spectrum and thus the impedance between 50..150Hz becomes a dominat impact.
Allthough the cab is rated to 4 Ohm nominal the real world shows now approximate 8 Ohm for the note E0.
I never measured by now what is going on whenever I use my 70's SVT with the 212 cab.
Considering my prefered eq settings then all I'm knowing is that the impedance of the 212 cab will not be a 4 Ohm one.
I'd assume something like 6 Ohm.
That's nothing to talk home about I think!
Even with a strong bass boost sound and then resulting 8 Ohm for the cab I would not bother about it here.
But I'm shure a lot of users drive heavily bass boosted sounds with valve amps ....
There is a guy named Paul Apollonio who wrote some researches related with the Ohm question.
read the following and enjoy:
http://www.audioholics.com/education/loudspeaker-basics/loudspeaker-power-handling
Invalid Link Removed
http://www.audioholics.com/educatio...akers-power-ratings-part-iii-the-test-results
It's rather a question of power dissipation indeed but the theory of impedance is a big manner even in this way.
Limiters and Compressors work in the same manner.
Both need a couple of signal periods to "calculate" the RMS before they can react and therefore reduce the signal.
That means it does not matter because for both, limiter and compressor, the first couple of signal periods remain always "as it is".
I'd never suggest you are save with half the RMS/AES.
Or on the other side you have to be very carefull with some watt more of that 1/2 power.
500 watt vs. 350 watt results in an increase of +20% of cone excursion. That's it all!
+6dB bump at low frequencies (bass) result in an increase of +100% cone excursion below approximated 80Hz.
The most amount of increase is normally below critcal frequency of the cab.
This behavior is due to the shelf filters that are used for the preamp eq's.
Take an amp with half the power of the cab, give +12dB boost @ bass, take a five string bass guitar and play a lot of percussive notes, I'm shure I'll kill any cab in between very short time.
Take an amp that's power is twice the cab's rated rms/aes, let the eq nearly flat, take a four string bass and play something like pop song material, I'm shure the cab will never die even if short time transients/dynamics run slightly into clipping and are constantly as high as twice the rated power of the cab.
I wouldn't trust too much in manufactures power ratings.
These power rating values are most of the time of theoretical nature and can therefore be very different for one and the same loudspeaker.
To tell an example. The Audio Engineering Society AES recommends to calculate the power rating by the Zmin of a loudspeaker, however for all the "RMS" ratings (as far as I know) the power dissipation values are calculated by Z nominal. So far as I know is this done by Eminence and many other well known manufactures.
Example:
a well known popular 8 Ohm 12" loudspeakers Zmin runs down below 6 Ohm (5,7 Ohm measured in free air).
The loudspeakers RMS power is rated to 250 Watt.
This 250 Watt RMS power consumption is calculated by using Z nominal (8 Ohm).
The AES specification will lead to a significant different value cause of using Zmin for the power calculation. Let's say 350 Watt AES then for the same loudspeaker.
I think there is a lot of discussion in forums if a 350 Watt amplifier is capable to burn off a 250 Watt RMS loudspeaker cause the amplifiers RMS power is significant above the loudspeakers rating.
No problem!
Consider the AES recommentation and calculate the loudspeakers power dissipation by Zmin, and so everything is fine.
Fortunately there are some professinal manufactures on the market which provide us engineers with some additinal specs we need to make proper estimate how much amp power we can provide to a given loudspeaker system.
Depending on the nature of audio signal, cause different signals cause different force to the system.
Unortunately there are a lot of manufactures leaving us poorly abandoned. That's very poor cause without additional specs we do not know anything about the cab we are playing with.
The only specs given by most manufactures are Ohm and Watt. And in addition to it some doubtful value for the lower frequency limit.
It would help a lot if at least the real -3dB lower limit would be given. Most of the time we read in the manufactures specs something like a theoretical -10dB lower limit that says nothing.
Compared this practice to my own 212 custom cab I could perform a SPL measurement direct to the vents and would get a plenty value of SPL even at 40Hz.
By the other hand, If I know the realistic -3dB lower limit and this limit is at 65Hz for example and the rated power is something about like 500 Watt RMS.
Then I know I have to take care a little bit with to much amp power cause the critical point starts already at 65Hz.
On the other side I'm a good bit more on the save side with a 500 Watt RMS cab when the -3dB lower limit says 55Hz or 50Hz.
But it's curios to spec a cab's lower limit to 35Hz for example. Although it is often done by many manufactures.
Specs like this are meaningless.
These power rating values are most of the time of theoretical nature and can therefore be very different for one and the same loudspeaker.
To tell an example. The Audio Engineering Society AES recommends to calculate the power rating by the Zmin of a loudspeaker, however for all the "RMS" ratings (as far as I know) the power dissipation values are calculated by Z nominal. So far as I know is this done by Eminence and many other well known manufactures.
Example:
a well known popular 8 Ohm 12" loudspeakers Zmin runs down below 6 Ohm (5,7 Ohm measured in free air).
The loudspeakers RMS power is rated to 250 Watt.
This 250 Watt RMS power consumption is calculated by using Z nominal (8 Ohm).
The AES specification will lead to a significant different value cause of using Zmin for the power calculation. Let's say 350 Watt AES then for the same loudspeaker.
I think there is a lot of discussion in forums if a 350 Watt amplifier is capable to burn off a 250 Watt RMS loudspeaker cause the amplifiers RMS power is significant above the loudspeakers rating.
No problem!
Consider the AES recommentation and calculate the loudspeakers power dissipation by Zmin, and so everything is fine.
Fortunately there are some professinal manufactures on the market which provide us engineers with some additinal specs we need to make proper estimate how much amp power we can provide to a given loudspeaker system.
Depending on the nature of audio signal, cause different signals cause different force to the system.
Unortunately there are a lot of manufactures leaving us poorly abandoned. That's very poor cause without additional specs we do not know anything about the cab we are playing with.
The only specs given by most manufactures are Ohm and Watt. And in addition to it some doubtful value for the lower frequency limit.
It would help a lot if at least the real -3dB lower limit would be given. Most of the time we read in the manufactures specs something like a theoretical -10dB lower limit that says nothing.
Compared this practice to my own 212 custom cab I could perform a SPL measurement direct to the vents and would get a plenty value of SPL even at 40Hz.
By the other hand, If I know the realistic -3dB lower limit and this limit is at 65Hz for example and the rated power is something about like 500 Watt RMS.
Then I know I have to take care a little bit with to much amp power cause the critical point starts already at 65Hz.
On the other side I'm a good bit more on the save side with a 500 Watt RMS cab when the -3dB lower limit says 55Hz or 50Hz.
But it's curios to spec a cab's lower limit to 35Hz for example. Although it is often done by many manufactures.
Specs like this are meaningless.
After much reading I'm still a bit confused.
Quick question, possibly silly but want to make sure
Is there much audible difference in volume between a 700 watts 4 ohm cab and the same cab in 8 ohms?
My amp is rated 750 watts at 4ohms and 400 watts at 8 ohms
Quick question, possibly silly but want to make sure
Is there much audible difference in volume between a 700 watts 4 ohm cab and the same cab in 8 ohms?
My amp is rated 750 watts at 4ohms and 400 watts at 8 ohms
Audible yes, useful is doubtful. 700 watts of bass frequencies is a tall order for a single cab unless it has multiple stout speakers (in which case it would probably be rated higher).
Sorry, I forgot to mention it's a 410 cab, an Aguilar DB410, rated at 700 watts and 101 dB sensitivity.
It will be paired with a DB750 amp, rated at 750 watts at 4 ohms and 400 watts at 8 ohms.
So, will there be much difference in volume between the 4 and 8 ohm versions?
Apparently, one (1) cabinet showing an amp 8 ohms is not as "loud" (slightly > about -3db) as the same amp pushing the 4 ohm version of the same cab, BUT . . .
If you get two (2) of the 8 ohm cabinets (showing 4 ohms to that very same amp), you will get tons(?) more air moving (loudness) . . .
Thanks.
I only want to use one cab on my rig, two 410 is too much, so I want to make sure I make the right choice with the 8 or 4 ohm cab so I can have as much volume as possible with just that one cab.
So, much difference between those two cabs?
No, not really much difference. certainly not enough to choose a 4 ohm cab, which limits future expansion.
