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Underpowering Cabinet Question?

#61
billfitzmaurice said:
That chuffing indicates that you're exceeding the output capability of that speaker. That comes as no surprise, an isobaric 410 can go no louder than a standard 210.
That could be what's wrong using it with the Ampeg cab. SS amps don't get along as well with sealed cabs as they do with vented. I recommend you get to a well equipped music store with all your gear. Try your amp with some standard 410s compared to the Orange, and some ported 810s or paired 410s compared to your Fridge.
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Why do you say SS amps don't get along as well with sealed cabs as they do with vented ? I've brought this up in another thread and nobody seems to agree with this notion.
 
#62
jnewmark said:
Why do you say SS amps don't get along as well with sealed cabs as they do with vented ? I've brought this up in another thread and nobody seems to agree with this notion.
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The average impedance of sealed cabs is lower than that of vented. SS amps don't care for low impedance loads. Sealed cabs are also less sensitive in the lows, and that can result in stressing the current capacity of SS amps in general and those with switching power supplies in particular. By the same token tube amps don't care for high impedance loads and can be bothered by ported cabs.
 
#64
billfitzmaurice said:
The average impedance of sealed cabs is lower than that of vented. SS amps don't care for low impedance loads. Sealed cabs are also less sensitive in the lows, and that can result in stressing the current capacity of SS amps in general and those with switching power supplies in particular. By the same token tube amps don't care for high impedance loads and can be bothered by ported cabs.
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Would this also apply to the Thuderchild, with both port plugs in ? The reason I am asking, ( and not to get too OT here ), is that I have been fooling around with a TC and a GB 9.0 head, with both ports plugged, and really like the results I am gettin, over the both ports unplugged. Have'nt used it on a gig yet, though.
 
#65
jnewmark said:
Would this also apply to the Thuderchild, with both port plugs in ? The reason I am asking, ( and not to get too OT here ), is that I have been fooling around with a TC and a GB 9.0 head, with both ports plugged, and really like the results I am gettin, over the both ports unplugged. Have'nt used it on a gig yet, though.
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The permutations are too complex to make a long distance diagnosis, you should just be aware that the possibility for problems exists. Ampeg ran into a major problem with the combination of the Micro VR and two sealed SVT210AV cabs. I haven't seen an official confirmation from Ampeg that it was an impedance issue, but that's what I suspect.
 
#68
BurningSkies said:
Because a speaker is pushing against air (in both directions), that air has an impedance and the speaker impedance reacts or interacts with it, which shifts its own impedance in a given frequency range.
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+1

As a magnet moves through a coil it creates current. This current generation changes the impedance seen by the amplifier. Now if the ease of movement of that speaker changes because of a sealed/ported cab, it will also change the impedance see by the head.
 
#73
I’ll be darn, thanks Skies.

I think I’m running on slow today - I read impedance but I was thinking resistance (brain fart). But in any event I just learned something new (cool). Hey, by how much can a sealed enclosure change the impedance and what is the mathematical equation, formula? And I think I need to learn more about peak impedance - you wouldn’t happen to have a good link would you? And I still don’t understand why there could be a problem with SS only and not tubes - can you explain it better?
 
#74
billfitzmaurice said:
The average impedance of sealed cabs is lower than that of vented. SS amps don't care for low impedance loads. Sealed cabs are also less sensitive in the lows, and that can result in stressing the current capacity of SS amps in general and those with switching power supplies in particular. By the same token tube amps don't care for high impedance loads and can be bothered by ported cabs.
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Tube amps with ultra linear output stages tend to deal with ported cabs better in the low end, after all you don't want flutter on your bottom do ya!:D
 
#76
Joe Louvar said:
I’ll be darn, thanks Skies.

I think I’m running on slow today - I read impedance but I was thinking resistance (brain fart). But in any event I just learned something new (cool). Hey, by how much can a sealed enclosure change the impedance and what is the mathematical equation, formula? And I think I need to learn more about peak impedance - you wouldn’t happen to have a good link would you? And I still don’t understand why there could be a problem with SS only and not tubes - can you explain it better?
Click to expand...

Easy way to see it is to look at the cab design pdf's at eminences site for the DeltaliteII2512. Compare the impedance curves between the sealed and vented designs as well as the impedance curve for the driver tested in free air. Then compare those to the in box curve for a driver that isn't recommended for sealed enclosures at all. The differences will become obvious.
 
#78
Joe Louvar said:
Hmmm, no way - how can a cabinet design change the impedance?
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Anything that influences the loudspeaker mechanically or electrically will be reflected in the impedance. Press your thumb on the cone? It'll change the impedance curve. Block the port(s), that'll change the curve also. A tear or slice in the cone will show up in the impedance curve, too.

Thiele_equiv_circuit.gif


(From Link Removed)
 

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