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jjl5590

Can I damage my cab by playing too loud too low?

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15 hours ago, Woodinblack said:

Agreed it is easier to do with a signal an octave lower than the speaker was designed to handle. Maybe when TC made the RH750 and matching cab they thought that they might be used together?

As I said, all of what you are saying is true for other amps and other speakers, and I have no questions on that. The RH750 has Active power management (that it is often slagged off for) which means it will never produce more than 35V (see attached) without clipping (as it peaks), and it has (according to talk bass where it was tested - I have no other sources) a 2nd order HPF starting at 70Hz at 12dB/Octave.

It is incapable of producing a 'signal an octave lower than the speaker was designed to handle' as literally the speaker was designed to handle the output of the RH750.

Add as a caveat to that, the HPF is only in the power amp, so if you take the output from the DI or the preamp out, and put that through an amp, then yes you really can damage it.

I don't see there is much point adding anything else to this, although seeing as the TC RH amps are very common and most of the time paired with the RH cabs, I am obviously happy to see links to all the 'my amp broke my speaker' threads that must exit.

To the OP, don't put any bass into any speaker, as apparently it is far too risky as none of them can handle it.

 

This is accurate as far as transients are concerned, but ignores the fact that as you limit the peak amplitude, this allows for an increase in average power. For example, a reduction of 3dB of transients allows for a 3dB increase in average power. The ear perceives average power as loudness. This is one reason why tube amps appear to sound louder than their power might suggest, and also one reason why compression is so useful.

With an increase in average power,  the risk to the speaker transitions from mechanical to thermal assuming there is an effective HPF involved.

Edited by agedhorse

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52 minutes ago, agedhorse said:

Yes.

Not sure what you mean then?

"Then why did you bother asking this question if you already knew the answer you wanted to believe?

There’s a lot to learn from the answers and comments that were made my members here and on TB, it appears you have missed the essence of this information."

What is the answer that I believe? What essence of information have I missed?

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5 hours ago, agedhorse said:

You have received in depth answers to your questions on both TB and here... never mind.

And for that I am extremely grateful and have learned a lot. 

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On 26/11/2020 at 14:54, jjl5590 said:

 

This lead me to wonder, could I possibly do any damage to the paper speaker cones of my cab by playing at such a low octave at high volume? Could it rupture them?

Cheers for any advice

You've got your advice and I think you realised this anyway from the way you asked the question. Yes you can damage your speakers with an amp even within the specified power rating of the speakers and the enemy is extreme equalisation/fx.

There are two ways to break a speaker and they are interrelated. you can do it one way or the other or a little of both. The enemies are overheating the coil and moving the coil and cone past their mechanical limits. The graph below shows the movement of the cone of the same speaker with the red plot at 1/4 of the power of the green plot. You can see tht the excursin rises as the frequency goes down but at 50 Hz the port takes over and the cone movement reduces right down. The horizontal red line is the excursion limit of 6.5mm. You can see that at full power the cab goes outside it's limits between 55 and 90Hz and again below 45Hz. If you put a bottom E at full power with an octaver (41Hz/2 or 20Hz) it would force the cone to travel through a 6cm round trip which would hammer it against the back of the magnet 20 times a second. Not good.

So for these frequencies (where the curve goes above the red line) the power handling is limited by the excursion. For the rest of the time the limit is the thermal limit.

 

image.png.a46bbc786eb750a1bd8752f4696856c0.png

So there you are the power to any speaker is less than the rated thermal limit at certain frequencies, genrally lower frequencies but there's almost always that dip just above the port frequency too. If you use just 3db of bass boost you will halve the power handling and an octaver is even worse. A decent HPF will pretty much help any reflex(ported) speaker cab by removing that huge spike in excursion below the tuning point.

 

Edited by Phil Starr
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Actually, if you add 6dB of bass boost, you reduce the power handling by a factor of 4 because 6dB of power increase is 4x the power and 2x the voltage. 

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6 hours ago, agedhorse said:

Actually, if you add 6dB of bass boost, you reduce the power handling by a factor of 4 because 6dB of power increase is 4x the power and 2x the voltage. 

Now corrected

I meant to refer the excursion, I got called away halfway through posting, sorry :)

Edited by Phil Starr
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On 29/11/2020 at 08:37, jjl5590 said:

And for that I am extremely grateful and have learned a lot. 

Of course you are, old boy.

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