# Can running speakers full range cause damage if they are not truly full range?



## tonyvdb (Sep 5, 2007)

So this topic was brought up in another post and thought it would be a good discussion.

Can you damage a speaker running them full range if they really cant do full range say from 20Hz-20kHz

My understanding is that if you keep the input volume within its designed range and the crossovers are designed well there is no reason not to run them full range other than taking the load off the amps driving them. 

A crossover will filter out any frequencies below or above the drivers range.


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## nova (Apr 30, 2006)

I'm no expert, and hopefully AJ, or someone else well versed in speaker design will chime in again but, 40 Hz won't necessarily damage any properly designed speaker.

For example, I have some speakers that are rated at;
Frequency response: 85Hz-20kHz (±3dB)
Sensitivity: 84dB (2.83V @ 1 Meter)
Crossover Frequency:	3,000 Hz
Crossover Slope: 12dB/Octave
Impedance: 8 Ohms

I routinely run these full range driven by a 250w amp to well above reference levels with no damage at all. Because of the way they are designed, they just don't reproduce what they are not capable of. Therefore, no damage.


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## Wayne A. Pflughaupt (Apr 13, 2006)

It would depend on the particular speaker, the bass content of the signal, and the volume level. Good-quality full-range speakers with large woofers can probably handle just about anything, even at high levels. However, something like rap played at high levels, or if someone applied a lot 30 Hz boost via equalization, that could indeed blow a bookshelf speaker.

Regards, 
Wayne


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## nova (Apr 30, 2006)

I'd assume that if, as Wayne states, I played some rap at high volume with a lot of boost at 30Hz I could damage my speakers. I don't think it would be due to the low frequency but most likely some distortion that would cause some damage.


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## ajinfla (May 10, 2009)

tonyvdb said:


> So this topic was brought up in another post and thought it would be a good discussion.
> 
> Can you damage a speaker running them full range if they really cant do full range say from 20Hz-20kHz
> 
> ...


Unfortunately, no, there are no highpass filters in passive speakers to filter very low frequencies, so indeed, they stand more chance of being damaged when run full ranged.
Luckily, AVRs have electronic high pass filtering available to prevent this.

cheers,


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## JBrax (Oct 13, 2011)

Great idea for a thread Tony! This isn't something I've given much thought but I'd guess any speaker can be pushed to the point of damage. Luckily as noted most AVR's have protection circuitry but is that circuitry protecting the AVR or the speakers? I thought the protection was for the AVR.


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## dgmartin (Oct 29, 2011)

Interesting discussion Tony, 3 topics into one...



tonyvdb said:


> Can you damage a speaker running them full range if they really cant do full range say from 20Hz-20kHz


You are more likely to exceed excursion limits. For instance, with typical 7in drivers (rated at 70W) and doing 30Hz, excursion/distortion rapidly limits the practical volume in this case and therefore there may be less risk of overheating (i.e. I can bottom them full-range with 30w or feel power compression above 100W when high passed). I'm not sure it applies to your system...



tonyvdb said:


> My understanding is that if you keep the input volume within its designed range and the crossovers are designed well there is no reason not to run them full range other than taking the load off the amps driving them..


Another reason is reduced distortion. The upper range of the driver will be much cleaner when high-pass filter is applied. The smaller the driver, the bigger the improvement. Of course this does not apply to a 15in woofer in a domestic environment.



tonyvdb said:


> A crossover will filter out any frequencies below or above the drivers range.


It depends on the crossover design but I suppose an high pass filter on the woofer is seldom/never implemented. In a passive XO, it requires large inductor and/or capacitors at low frequency (good economic rationale not to do it).


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## tonyvdb (Sep 5, 2007)

All great info, interesting to know about crossover design not having any HPF. I guess Im just spoiled with the speakers Ive been using as even my surrounds can go down to 35Hz. My mains much lower. I can totally see causing damage to a bookshelf with a 5"driver as there is no physical way for it to move enough air to produce anything below 60Hz.
So what is being said is that the crossover only controls/protects the region where the tweeter and woofer overlap?


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## Delphunkey (Jan 15, 2007)

Effectively, once clipping occurs at any frequency, could cause damage to a speaker. ...So a crossover will cutoff frequencies to speaker and reduce from clipping at a frequency not designed for the speaker. 

You can use the example of tire speed ratings for a car, you can certainly go faster than the rating, but if you continually exceed the speed, this will cause greater wear and the possibility of a breakup. If you put a limiter on the engine to be below or match the speed rating, your risk of damage is significantly reduced.

A speaker is effectively a motor with a speed rating (frequency and db) and a crossover is the speed limited on the motor and clipping is the break up of a tire run in excess.


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## kingnoob (Mar 12, 2013)

I once blew a vintage book-shelve woofer, later repaired it. From running a Yamaha amp on large to them as fronts. Turns out it exceeded xmax and woofer cable disconnected. I dont use those woofers anymore , they weren't very good.


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## tonyvdb (Sep 5, 2007)

Ok but lets not steer this in the wrong direction. My question is based on keeping the amp/speaker within its operational range. People who try to get 110db out of their bookshelf speakers running full range are just asking for it.


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## dgmartin (Oct 29, 2011)

tonyvdb said:


> So what is being said is that the crossover only controls/protects the region where the tweeter and woofer overlap?


Basically yes... it depends on how we define the crossover. For some people, the function of the crossover is simply to split the low and high frequencies (the fact pre-made "X" Hz crossovers are still sold testifies some people adhere to that definition). In a broader definition, the crossover function is also to shape the drivers' response towards a target response. So in the broader sense, it LP the woofer and HP the tweeter near the crossover point but it also controls the response of each well below/above the crossover point (examples are taming driver resonances, attenuating the woofer above the 2pi/4pi transition frequency etc...). So, coming back to your question, the crossover will only/mostly protect the tweeter from over-excursion and/or thermal distress.

The only external protection for the LF driver is the stiffness of the air in the enclosure and/or the mass of air in the port. Ported designs limits excursion at the box tuning frequency but to offer little control below that. If there is not much signal content below a ported box tuning frequency, it does a better job than a closed box. Vented box with tunings above 80Hz (totally arbitrary but you see the point) are problematic since most modern material has content below the tuning. 

Amplifier clipping is another issue. When clipping occurs, the amplifier produces high-frequency distortion which is more susceptible to damage the tweeter since the HF distortion level is above the normal content of program material.


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