Maximum safe measured constant spl for sierra raal tower?

I was talking to my dad about how to calculate max spl for a speaker and he told me about how to calculate it by doubling the wattage for every 3 db over baseline sensitivity until you reach the maximum input power of the speaker but it seems like there would be more to it. Wouldn't the real max spl be limited by how high the lowest rated driver can go before the sound becomes distorted? Just wondering how high I can crank these babies before one or more drivers start to get speed wobbles or can't keep up with the other drivers. My amp is respectably strong but I'm too chicken to keep turning it up until they give. Can I do 115db (just guessing) actual in room spl like an imax theatre? I just saw the hobbit in imax and the sound was so loud it felt like it was punching me in the heart. Awesome :) If I'm doing my math right my 150 watt amp should be able to get the towers to 112db with 128 watts. Does that sound right?

Depends on how far away you are from the speakers,sensitivity, how many speakers,how close to boundaries, etc...

Try this to get an idea, and I am not vouching for it's accuracy- maybe Dave or someone else can answer that.

http://myhometheater.homestead.com/splcalculator.html

I had a fellow Audiologist who tried 90db RMS for 15 minutes straight of white noise and threw up right around the 14 minute mark. The body does crazy things when exposed to high SPL for prolonged periods. Its hard watching at 80db constant with 20db peaks at a measured 10-15 feet back. Peaks are one thing but constant sound pressure is not always healthy. If a speaker is 90db sensitive at 1 watt, its very difficult listening to a constant output for that long. That's beyond yelling volume. fwiw

Forgot to also mention, 140db will make a person vomit in under 5 minutes, crazy loud!

I t sounds like what your saying is that I'm probably not even feeding my speakers a single watt at normal listening levels. Well, maybe I am if the db is halved every meter away you are (I think?) but it sounds like I'm not even getting close. I usually sit about 10 feet away in a 15x15 feet room.

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Originally Posted by hearing specialist

I had a fellow Audiologist who tried 90db RMS for 15 minutes straight of white noise and threw up right around the 14 minute mark.

Forgot to also mention, 140db will make a person vomit in under 5 minutes, crazy loud!

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Wow, that is unreal! :eek:

I've never tried white noise for that long and at that volume. Was he testing a theory about vomiting or was that an unexpected reaction? I remember using pink noise at 90 dB for 10-15 minutes back when I worked in live audio, although I was glad when the EQ'ing was done!

Regarding 140 dB, there's no way I could stand that, especially with mid and high frequencies. I start running for the exits around 110 dB average.

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Originally Posted by Brannigan

I t sounds like what your saying is that I'm probably not even feeding my speakers a single watt at normal listening levels. Well, maybe I am if the db is halved every meter away you are (I think?) but it sounds like I'm not even getting close. I usually sit about 10 feet away in a 15x15 feet room.

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Are you referring to the inverse square law? That is to say, a decrease of 6 dB for each doubling of distance (or for the other way around, an increase of 6 dB for each halving of distance).

So at 10 feet back, the SPL is about 6 dB less than it would be at 5 feet, and about 10 dB less than it would be at 3.281 feet (1 meter). However, it may not be quite this much due to the presence of reflection points in your room. :)

"Are you referring to the inverse square law? That is to say, a decrease of 6 dB for each doubling of distance (or for the other way around, an increase of 6 dB for each halving of distance).

So at 10 feet back, the SPL is about 6 dB less than it would be at 5 feet, and about 10 dB less than it would be at 3.281 feet (1 meter). However, it may not be quite this much due to the presence of reflection points in your room."

I'm probably just confused as usual. The main point of the thread is basically how much volume the drivers can put out. I know it says 300w max input if I remember right but I have the high pass set at 70hz so the speakers won't draw as much power for the same volume right? Doesn't bass require the most power?

Low frequencies usually do require more power/energy to reproduce compared to mid and high frequencies, and while there are several reasons, one of them is that the woofers have more mass to move compared to a small dome or ribbon tweeter. I don't know how much SPL / voltage each Sierra Tower driver can handle. In other words, the RAAL tweeter can cope with X watts, the mid driver can manage Y watts, and the woofers can handle Z watts. That's definitely one for Dave. The crossover handles the main input signal and determines what gets sent to a specific driver, and there's all sorts of voodoo involved there. :D However, I'm confident that everything is well balanced in the crossover so you don't run into a serious case of "the weakest link."

For the Towers, 300 watts is 300 watts, but that is continuous power. They can handle 500 watt unclipped peaks when necessary. In your case, the amplifier/receiver can be more efficient because it doesn't have to reproduce the stuff below 70 Hz (to be more precise, frequencies below 70 Hz are attenuated at a certain rate), and all that low frequency content is sent to the subwoofer. The Tower woofers also won't have to work as hard, but I don't believe that changes input power limits. 300 watts input is still 300 watts whether it has low-frequency content or not.

If you're looking for pure SPL output figures for the entire tower, then it's kind of a balance between input voltage and distance. The closer you sit to the speakers, the louder it will seem. You can break it down by wattage and distance, but that's just a general idea of what to expect. There's more to it than that. Correct me if I'm wrong, but this is what you're thinking about:

1 watt = 92 dB
2 watts = 95 dB
4 watts = 98 dB
8 watts = 101 dB
16 watts = 104 dB
32 watts = 107 dB
64 watts = 110 dB
128 watts = 113 dB
150 watts ~ 113.5 dB

Adding a second Sierra Tower (making a pair) gives another 3 dB increase = 116.5 dB

These values would be possible in a perfect world at 1 meter from the loudspeakers. However, these measurements are usually done with something like band-limited pink noise. They can also vary according to typical in-room acoustic effects (peaks and nulls, boundary reinforcement), amplifier efficiency (not 100%), and general loss of maximum output signal due to resistance and heat just to name a few. Then you've got the fact that SPL will decrease the further back you are from the source.

For real-world music and movies in a home environment, it's uncommon to achieve continuous 150 watts output from the amp. That's not even accounting for peaks and transients. You would be getting tons of distortion and heavy clipping at that point trying to reproduce typical 3-20 dB peaks. Two reasons the IMAX can get loud is that they use specialized loudspeakers (often with very high efficiency), plus a LOT of amplifier power (12,000 - 24,000 watts depending on the theater).

I dunno if any of that helped or if I just threw more mud in the water. :)

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Originally Posted by Brannigan

I was talking to my dad about how to calculate max spl for a speaker and he told me about how to calculate it by doubling the wattage for every 3 db over baseline sensitivity until you reach the maximum input power of the speaker but it seems like there would be more to it. Wouldn't the real max spl be limited by how high the lowest rated driver can go before the sound becomes distorted? Just wondering how high I can crank these babies before one or more drivers start to get speed wobbles or can't keep up with the other drivers. My amp is respectably strong but I'm too chicken to keep turning it up until they give. Can I do 115db (just guessing) actual in room spl like an imax theatre? I just saw the hobbit in imax and the sound was so loud it felt like it was punching me in the heart. Awesome :) If I'm doing my math right my 150 watt amp should be able to get the towers to 112db with 128 watts. Does that sound right?

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There is really no possible way to answer this as there are just too many variables involved to give a definitive answer. Distance from the speakers, room modes, reverberation, amplifier power and power supply capabilities, source material, full range or high passed...

In our extremely well damped 2500 cu ft listening room, I have run a pair of towers reaching 110dB peaks without issue for an hour, measured at 4 meters from the speakers. Our listening room is well treated to eliminate first and second reflections and is nearly completely "dead". In a typical environment, you can add 3-6dB for room gain due to reflections. The towers were being run full range and this was not the the max spl capability of the towers. This was being run off a high quality 150 wpc amp, which was at its limit.

This is a listening level I would not recommend for anyone -- it is extremely loud and at the threshold of causing hearing damage.

Basic rule of thumb, if you are pushing insane volume levels and you hear either mechanical distress or distortion, quickly turn the volume down. An instantaneous peak above a driver's power rating will typically not cause damage, but it will if continuously driven this way. The more serious concern is if the amp/receiver goes into clipping which can instantly take out multiple drivers and this type of damage is not covered under warranty -- and in the case of ribbons, can be quite expensive.

It is complicated because you really do not know what the actual power capability of your amplifier/receiver is. Just because it is rated at 100 watts into 8 ohms, does not mean it can really output that amount of power continuously, especially when multiple channels are being driven and when you have no idea of what your actual AC power is. Even a slight AC power line drop can send your amp into clipping and it is also important to keep in mind the speaker impedance varies all over the place. Hit the speaker with a huge dynamic peak at a frequency where speaker impedance is at 4 ohms, and depending on the quality of your amplification, it may only be able to supply 50 watts of power before clipping.

Be sensible and protect both your hearing and equipment, develop a critical ear so that you will know when you have either reached the speaker's maximum capability or your amp's and you will have no issues. And the best way to develop a critical ear is to listen at lower volume levels, which forces you to really focus on what you are hearing without getting other senses involved.

It sounds like my guesstimation of about 112db is in the ballpark and fairly consistent with the spl calculator and what davef is saying. The short answer seems to be "louder than I need". As far as clipping I think I'm ok there if harman kardon is at all honest about their claims about the hk 990 amp. A review I read suggests it may be under rated at 150 watts continuous. Not that I want to blow my ears out all the time of course. I doubt I'll get close to the speakers limits any time soon but I'm pretty sure they can do more than I've been asking of them. I appreciate every ones input which all seems to be right on the mark. Thanks!