Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Tim McCulloch]

Thanks bob and everyone else.

The reason i OPed was the fact i'm borrowing these speakers with an option to buy. Like i said before i powered them with much less last year. As this main/sub configuration is getting old i was really just worried about blowing speakers that don't belong to me.

I was told that "you can never overpower a speaker but it's very easy to underpower" (not sure after a few years how reliable this guy really was). The only thing i've ever had the opportunity to "overpower" is my carvin subs. Rated at 1600W @4ohms I drive them with the 2000W Dcm's bridged with no problem except if I can't get enought AC Amps for the DCM's they trip breakers. They sound WAY better to me than when powered with my 1500W DCM's bridged.

However I have had problems with blowing the CD's in my carvin monitors. They were originally fitted with (old motorola) Piezos-IMO they are better than the CD's i replaced them with (pyles, I needed to be cheap at the time ). I have also replaced the xovers with better quality units that match the new CD's better. The mons are only getting about 200W when rated at 400W. I feel this is why i'm blowing CD's.

How are the compression drivers (cross dressers, compact discs, Carl Duncan, other CDs) failing?  Diaphragm shattered, torn, separated from the suspension?  Is the voice coil open or shorted?  What does the coil look like?  A couple of years back, Ivan or somebody else posted pictures of voice coils subjected to over power, peak over-voltage (on a HF voice coil that was hard to spot), etc.  It's probably searchable...

But in general, transducers die because they got too hot or were pushed to far, physically... or both.

[Paul G. OBrien]

I was told that "you can never overpower a speaker but it's very easy to underpower"

That's an oft repeated statement that has some merit but as you have hopefully learned here there is a lot more to the story.

The only thing i've ever had the opportunity to "overpower" is my carvin subs. Rated at 1600W @4ohms I drive them with the 2000W Dcm's bridged with no problem

Well.. actually that's not overpowered is probably the perfect combo to get the maximum out of the speakers, the amp will be just below clipping when the drivers are seeing just enough voltage to produce their maximum output.

However I have had problems with blowing the CD's in my carvin monitors. They were originally fitted with (old motorola) Piezos-IMO they are better than the CD's i replaced them with (pyles, I needed to be cheap at the time ). I have also replaced the xovers with better quality units that match the new CD's better. The mons are only getting about 200W when rated at 400W. I feel this is why i'm blowing CD's.

There is more to properly configuring a compression driver than installing an over-the-counter crossover, an L-pad will also be needed to reduce output of the CD to match the LF driver and this L-pad also serves as protection for the CD. In pro cabinets this L-pad consists of fixed value ceramic power resistors arranged in an "L" pattern between the crossover HF output and the CD driver, and the value of those resistors is determined by how many Db of attenuation is required to match driver output levels. Setup this way it will be virtually  impossible to blow the CD driver at the power levels you're talking about assuming a decent quality CD is used

[Ivan Beaver]

, an L-pad will also be needed to reduce output of the CD to match the LF driver and this L-pad also serves as protection for the CD. In pro cabinets this L-pad consists of fixed value ceramic power resistors arranged in an "L" pattern between the crossover HF output and the CD driver, and the value of those resistors is determined by how many Db of attenuation is required to match driver output levels. Setup this way it will be virtually  impossible to blow the CD driver at the power levels you're talking about assuming a decent quality CD is used

I would argue that not all (probably very few actually) pro cabinets use the attenuators in a L configuration.  It is mostly a series resistance with a parallel bypass capacitor to extend the upper HF response.  The crossover is designed with this attenuation in mind.

The purpose of the L pad is to maintain a constant impedance to the crossover-sot he crossover freq does not change with a changing series resistance/impedance between the crossover and the loudspeaker.

[Bob Leonard]

I would argue that not all (probably very few actually) pro cabinets use the attenuators in a L configuration.  It is mostly a series resistance with a parallel bypass capacitor to extend the upper HF response.  The crossover is designed with this attenuation in mind.

The purpose of the L pad is to maintain a constant impedance to the crossover-sot he crossover freq does not change with a changing series resistance/impedance between the crossover and the loudspeaker.

Correct. The crossovers resistor network is designed for this purpose and provides a fixed and reduced amount of power through the network to the compression driver. The L-PAD would be used to manually alter the amount of high level output, or in some cases the overall output, and always lower from the fixed point, never higher. This is sometimes referred to as shading.

[Brad Weber]

That's an oft repeated statement that has some merit but as you have hopefully learned here there is a lot more to the story.

I would argue it actually has little merit as you cannot underpower a speaker, a speaker will output something with even a fraction of a Watt and running it that way will not hurt it.  What you can have is a system that cannot handle the application, basically a system that is 'underpowered', and that may be the result of a number of factors that could include the amplifier.


Conversely, you can overpower a speaker, however as noted, there is often more to it than just a single number power rating.

[Ivan Beaver]

I would argue it actually has little merit as you cannot underpower a speaker, a speaker will output something with even a fraction of a Watt and running it that way will not hurt it.  What you can have is a system that cannot handle the application, basically a system that is 'underpowered', and that may be the result of a number of factors that could include the amplifier.


Conversely, you can overpower a speaker, however as noted, there is often more to it than just a single number power rating.

And just to add-there is no problem hooking a 10,000 watt amp to a 10 watt loudspeaker.k

AS LONG AS you don't drive the amp to hard and allow it to produce more voltage than the speaker can handle.

[Paul G. OBrien]

The purpose of the L pad is to maintain a constant impedance to the crossover-sot he crossover freq does not change with a changing series resistance/impedance between the crossover and the loudspeaker.

Actually that's called a zobel network and it's a common component of the low freq portion of a passive crossover where driver impedance can be a factor of 10 higher at the crossover frequency than it is at it's minimum. In comparison the impedance of a compression driver may only vary a few ohms from the crossover up so impedance matching isn't as big a deal although.. a shunted resistor is a good way to compensate for the drivers natural reduction in output at higher frequencies.
All that said we're not dealing with a custom designed crossover here, it's a store bought textbook crossover and I was just suggesting a way to get relatively flat response from both drivers and some basic driver protection.