[pne]

So i've just purchased telrac's well known fantasy adventure album and 1812. For those of you who aren't familiar with these, they both have digitally recorded bass going down to the single digits. On the cd bookets there are clear warning signs that say establish safe listening levels to prevent equipment damage. My question is, what would be a safe listening level?? I'm afraid of turning these tracks up because I have a horrible image of both my woofers bottoming out and dying a horrible death. Should I have a low frequency cutoff at a more realistic level, say 20hz? I assume the track is meant to be listened to at a reference 85hz?

 

[rickcr42]

It is always a good idea to impose limits on the frequency response of a system.Unlimited bass would actually be DC and we know we can not have that (and do not) but even at the high end some garbage (especially clipping) in the ultrasonic range can fry a tweeter over time.

And that is where the problems come in.
Not the instantaneous peaks but either continuously loud levels or hitting those peaks in rapid succession over a period of time.This heats up the voice coils and could cause it to fail.Ferro-fluid is a help but not perfect


a 20 hz high-pass filter will actually be -3db @ 20 hz and
-15db @ 40 hz plus will need to be at least 18dB per octave if you are to have any actual rolloff occuring that is useful.
-6db looks pretty on a scope but will be useless unless the filter is started very high up in the bass frequencies and -12db produces a really nassty phase shift (180 degress)

Best bet would most likely be a -18 dB high-pass bessel filter @ 15-18 hz.Not very intrusive and allows some protection

 

[Necros]

Too many variables and cannot be predicated...

Size of room
Requested SPL
Distance to speakers
Amplifier (power and current delivery)
Speaker (sensitivity, impedance)
Speaker frequency response- full range or not?
Pre-amp stage (bass/treble adjustments or bypassed)
Bass management- set to full-range, or another setting- 40/60/80hz etc?
Subwoofer- capable of reproducing the frequency at that SPL without bottoming out? Calibrated low/correct/hot?

 

[pne]

Size of room- very small

Requested SPL- not sure on this, but the level the cd was meant to be heard at. I've been told this is 85dB, and assume this is an average.

Distance to speakers- 8-9 feet

Amplifier (power and current delivery) sonic t-amp, 5 watts, unknown current. SLA can deliver quite a bit of current in a spike though.

Speaker (sensitivity, impedance) 8ohm 92db

Speaker frequency response- full range or not? 50hz-22khz 3way, nonfullrange

Pre-amp stage (bass/treble adjustments or bypassed) bypassed

Bass management- set to full-range, or another setting- 40/60/80hz etc? fullrange

Subwoofer- capable of reproducing the frequency at that SPL without bottoming out? Calibrated low/correct/hot? not used, incapable of producing 20hz above 90db.

 

[Necros]

Only use this is a a guide..as the page states "This calculator does not account for room acoustics, amplifier dynamic headroom or off axis listening positions."

http://www.myhometheater.homestead.c...alculator.html

I get 96.2dB maximum possible spl output with your system.

In my 2 channel Hi-Fi system I get 105.2dB maximum possible spl output. 87dB speaker 8ohm, 75W amp high current, 2 speakers, 7', near a wall.

As for your amp...mentioned elseware "ndeed, the Sonic Impact T-Amp finds its natural competitors in a price range that is 100 times its price"

Ahh more hyping up..why can't they just be reasonble and perhaps compare it to budget SS gear? These fanboys really do loose their credibility with stating BS like that.

 

[pne]

so does this mean i shouldnt exceed 96db for listening? I don't really know how this number applies. If my system can put out 96 dB, will 96db peaks of 15hz hurt it? I am not concerned at all about my subwoofers clipping during the 15hz peaks, they are replacable and expendable, but I don't want to damage the woofers on my towers which are quite expensive and rolloff at 50hz.

 

[Necros]

Hard to say- your system could be fine at a usual approx 91dB peak level, but if the amp is insufficient at lower loads / during lower frequency (impedance/frequency sweep) then it's possible distortion will be much higher. Since you're using one amp for both channels and HF & LF if the amp clips it will effect LF and HF. You might get away with short clipping on LF, but not HF.

One solution- buy a Krell Master Reference

 

[dvw]

I have the 1812. At normal listening level, when the canon fired it is a very very loud boom. It will shake the window and knock things off the table.

The peril of this is if your amplifier can provide the current it will clip and become DC and that will fry your speaker. The other problem is the speaker cone might push out too far and get blown out.

As far as your concern if you have the proper cross over, and direct most of the energy to your subwoofer. That should be okay.

First time I listen I did not realize the cannon was so loud. But my speakers survived, so I think speakers might be sturdier than we think.

I would recommend you turn down the volume as the misic get to the cannon part. This will give you an idea how loud they can be. Then gradually turn it higher until you are comfortable with the volume.

 

[rickcr42]

Quote:

so does this mean i shouldnt exceed 96db for listening? I don't really know how this number applies. If my system can put out 96 dB, will 96db peaks of 15hz hurt it? I am not concerned at all about my subwoofers clipping during the 15hz peaks, they are replacable and expendable, but I don't want to damage the woofers on my towers which are quite expensive and rolloff at 50hz.

no harm will come to your system from hitting music peaks higher than the average levels it can produce.
It is continous music power over a period of time that will fry a voice coil from overheating it and that is from compressed music which has little variation from loud to soft (most pop and rock) and NOT from dyanamic peaks unless accompanied with clipping signals.These signals are usually in the ultrasonic range and it is the tweeters that will blow,not the woofers from these peaks if the amp is not up to it.

The main reason for a low cutoff is to free up the amp from trying to reproduce subsonic signals that have no musical content (below 20hz) thus allowing more actual power to flow to the speakers.

Quote:

I have the 1812. At normal listening level, when the canon fired it is a very very loud boom. It will shake the window and knock things off the table.

a perfect example of highly dynamic music.the system is loafing along and then WHAMMO !!!

again,this is easily handled by the average mid-high to high end system and even lesser systems will usually just compress the peak-flatten out the extremes

Quote:

The peril of this is if your amplifier can provide the current it will clip and become DC and that will fry your speaker. The other problem is the speaker cone might push out too far and get blown out

Wrong answer man.Clipping will not produce a DC signal (only if DC is present at the input can it be at the output unless the amp fails and then you have bigger fish to fry) but the opposite extreme-an ultrasonic signal.this can cause two major problems and both are heat related.

1-the power transistors are producing or trying to anyway,a full power signal in a frequency range they are not meant to due to power supply limitations and design.this causes one or more to fail which in turn takes out more and those even more.It is called "thermal runaway"

2-if the amp CAN sustain this then the ultrasonic power will not be heard but your tweeters will be very unhappy with the presence of it.Since most are not designed to handle a full power continous signal in this range they will heat up and pop the voice coil.

DC has nothing to do with clipping unless the amp has failed and the power supply is somehow reaching the output-highly unlikely.

BTW-a speaker sensitivity of 92 db means you will use far less amp power to reproduce the peaks than a less efficient system.
What this actually means is you are getting 92 decibels of music at 3.5 feet and most likely close to that at the three meter point with just 1 Watt of amplifier power.
Your system most likely can hit 115db at peaks and at some frequencies without unduly stressing any part of the system as long as you stay at a reasonable average level.

again I stress it is continous high level volumes over a longish period of time with a steady state of clipping you need worry about and NOT music power that will be mostly loafing along at one or two watts allowing the use of the other watts to hit the peaks with grace.

Enjoy the disc man and don't sweat the details

 

[pne]

Quote:

Originally Posted by dvw I would recommend you turn down the volume as the misic get to the cannon part. This will give you an idea how loud they can be. Then gradually turn it higher until you are comfortable with the volume.

this is what I have been doing, but it's no fun jumping out of my listening chair, running over to the volume dial when the track hits 15:00 or so. Not to mention the rest of the track is so quiet compared to the cannons.



Quote:

Originally Posted by rickcr42 2-if the amp CAN sustain this then the ultrasonic power will not be heard but your tweeters will be very unhappy with the presence of it.Since most are not designed to handle a full power continous signal in this range they will heat up and pop the voice coil.

if the amp can sustain it, then there would be no ultrasonic sound caused by clipping right? I don't quite understand this part. Chicken/egg?

 

[dvw]

Rick;

While I respect your knowledge greatly especially in amplifiers, I have to disagree with you on clipping.

While light clipping will produce no significant DC, a high level of clipping will. When severe clipping happens, the waveform will become almost like a square wave in the time domain. And if you do a Fourier tranform of this waveform into the frequency domain, you'll find DC content in the power spectrum.

This is what I mean by DC caused by clipping.