Did I lose a hertz or two?

[nhpm510]

Scary to say, but I've been thinkin'. Which always causes a question.

If I have a bookshelf speaker rated down to, say 48hz, and a song has notes in the 30 hz range, does the speaker make distortion while trying to playback those notes? Wouldn't all that distortion be bad for a speaker/voice coil?

Or, does the speaker not produce any notes at all below the 48 hz range?

tanks and artillery fer answerein'

 

[MDS]

If the speaker is rated down to 48 Hz that is usually it's -3 dB point, meaning at 48 kHz the sound will be down 3 dB from what was input. The speaker will have output below that point but it will be attenuated even more until at some point you won't hear it at all.

 

[nhpm510]

It is that not hearing it part that worries me. Would I be damaging the speaker? Esp. if I was listening at a high levels as this signal attenuates?

Or, does the speaker/voice coil not recognize the electrical sound signal?

 

[skizzerflake]

Some speakers will double frequencies below what they can reproduce correctly, so the 30 Hz note becomes 60 hz and a bunch of harmonics. The good news is that isn't really much in the 30 hz range except a few pipe organ notes. Below 40 is mainly the territory of pipes and sound FX in movies.

 

[Sheep]

Some speakers will double frequencies below what they can reproduce correctly, so the 30 Hz note becomes 60 hz and a bunch of harmonics. The good news is that isn't really much in the 30 hz range except a few pipe organ notes. Below 40 is mainly the territory of pipes and sound FX in movies.

Actually, I think it goes up to 90Hz. My friend played a 30Hz tone on his PC sub, and the sub played a 90Hz tone. I don't know, his sub is garbage.

The speaker will be fine as long as the driver isn't throwing excessively. Do you know have a subwoofer?


SheepStar

 

[nhpm510]

Sheepstar,
I use sub for my HT and 2 ch listening, all crossed over as necessary.

But I use a bedroom system which does not have a sub, hence the question as to what is hapening inside my spks. (Mostly thinking out loud and bouncing ideas off the audio gurus)

How do you know if the driver is throwing excessively?
By hearing distortion?

thks

 

[Sheep]

How do you know if the driver is throwing excessively?
By hearing distortion?

thks

By looking at it.

Just make sure it isn't doing this.

SheepStar

 

[j_garcia]

If your speaker doesn't sound like it is doing something wrong, then there is nothing to worry about, exactly as MDS said. Those notes will simply get ignored if they are outside the physical range of the speaker. 30Hz will most likely still be in the range of the speaker if it is -3dB at 48Hz.

 

[Resident Loser]

Do yerself a favor...

Scary to say, but I've been thinkin'. Which always causes a question.

If I have a bookshelf speaker rated down to, say 48hz, and a song has notes in the 30 hz range, does the speaker make distortion while trying to playback those notes? Wouldn't all that distortion be bad for a speaker/voice coil?

Or, does the speaker not produce any notes at all below the 48 hz range?

tanks and artillery fer answerein'

...don't lose sleep over it...that lower limit is a product of the natural driver roll-off and the enclosure's loading of it...Without a sub, the signal will be there but, if indeed 48Hz is the down 3dB point, anything below that number will most likely drop off, perhaps precipitously, and not even cause the woofer to move...It's when you try to apply some sort of bass boost that the driver will not tolerate, that damage can occur. Besides if you are using a sub, and depending on your set-up scheme, there is a slope (XdB/oct) where the hand-off is made...anything below the subs' Xover point shouldn't be making it to your stereo pair...

jimHJJ(...worry about what you can hear...)

 

[MACCA350]

Without a sub, the signal will be there but, if indeed 48Hz is the down 3dB point, anything below that number will most likely drop off, perhaps precipitously, and not even cause the woofer to move...

It depends if the speakers have internal subsonic filters. To illustrate this a while ago I played some test tones through my mains.

With the mains set to 'LARGE' I played a 10Hz tone, which I burnt to cd so I could check the whole chain of equipment. What happened was the bass drivers in the mains pounded full throw in and out trying to reproduce the 10Hz, although there was no sound at all and they didn't have the ability to produce enough SPL to pressurize the room(the DD15 gets the windows rattling at 10Hz, so I know how 10Hz effects my room) they were most definitely moving and using amp power to do so.

Depending on what you listen to and how loud you listen to it, this may not be an issue.

cheers

 

[Resident Loser]

OK but...

It depends if the speakers have internal subsonic filters. To illustrate this a while ago I played some test tones through my mains.

With the mains set to 'LARGE' I played a 10Hz tone, which I burnt to cd so I could check the whole chain of equipment. What happened was the bass drivers in the mains pounded full throw in and out trying to reproduce the 10Hz, although there was no sound at all and they didn't have the ability to produce enough SPL to pressurize the room(the DD15 gets the windows rattling at 10Hz, so I know how 10Hz effects my room) they were most definitely moving and using amp power to do so.

Depending on what you listen to and how loud you listen to it, this may not be an issue.

cheers

...you are purposely feeding a 10Hz signal and I sincerely doubt there is much cause for concern in any commercial release containing any quantity of that sort of low frequency info...Additionally, your loudspeakers are rated to 30Hz, so I'm fairly certain 20Hz, while beyond a spec of -3dB, still has some useful output at that frequency. I would think that your Denon would have some infasonic filtering, since I see no claim as to it having wide bandwidth capability and a published spec whose low end is 20Hz...At 10Hz you are well into TT rumble-land and perilously close to force-feeding DC to your woofers.

jimHJJ(...which would not be a good thing...)

 

[MACCA350]

At 10Hz you are well into TT rumble-land and perilously close to force-feeding DC to your woofers.

jimHJJ(...which would not be a good thing...)

Yes, this is partially why I have them set to small and advise others to do the same(if they can or need to)

Sub 20Hz information is quite common in movies and even some music(more likely synthesized music though). The method I used above is the easiest way to see what is happening to that subsonic information in your system and see if there is any need to do anything about it.

cheers

 

[Resident Loser]

...you are purposely feeding a 10Hz signal and I sincerely doubt there is much cause for concern in any commercial release containing any quantity of that sort of low frequency info...Additionally, your loudspeakers are rated to 30Hz, so I'm fairly certain *20Hz, while beyond a spec of -3dB, still has some useful output at that frequency. I would think that your Denon would have some infasonic filtering, since I see no claim as to it having wide bandwidth capability and a published spec whose low end is 20Hz...At 10Hz you are well into TT rumble-land and perilously close to force-feeding DC to your woofers.

jimHJJ(...which would not be a good thing...)

*CORRECTION: Sh/be 10Hz...and now my brain Hz...

 

[Ampdog]

To stress what was said by Macca350, one thing one should be careful about with all low frequency speakers especially in these days of DVDs made for cinemas (containing low frequencies that could be reproduced there), is overloading the loudspeaker. In some cabinet designs woofers can be "activated" by such signals without audible output and either hit their mechanical stops or incur some other damage. (Amplitude is inversely proportional to frequency.) Fortunately this is easy to see when looking at the cone - high amplitude excursions should trigger an alarm. (One would like to see a low cut-off filter built into such circuitry to take care of the above mentioned situation. I am not familiar with commercial equipment - do some amplifiers have such filters?)

 

[no. 5]

Amplitude is inversely proportional to frequency

so: lower frequency need more power, and higher frequencys less power, proportional speaking?

 

[Nuglets]

Correct me if I'm wrong, but wouldn't the most simple answer to the original question be...No it will not damage the speaker's because the crossover will cause the lower frequencies to roll off substantially so the amplitude of the low frequencies going to the speaker's will be quite small.

 

[MACCA350]

Correct me if I'm wrong, but wouldn't the most simple answer to the original question be...No it will not damage the speaker's because the crossover will cause the lower frequencies to roll off substantially so the amplitude of the low frequencies going to the speaker's will be quite small.

Correct, IF the speakers are set to 'small'.

cheers

 

[Ampdog]

so: lower frequency need more power, and higher frequencys less power, proportional speaking?

No, no 5, this is a basic physics thing. The same power, the same output "volume" (disregarding imperfections). The fact is that for that "same volume", i.e sound intensity, there is a velocity relationship between cone and output (again talking in principle only, disregading particular cabinet designs etc.). You would have noticed that one cannot see or even feel the cone movement in a tweeter. The lower the frequency, thus the slower the cone movement, the further it has to move to create the same pressure wave. You do not do anything from the outside to create this; it goes naturally. That is to say, if you use a signal generator as input source (it normally has a constant voltage output) and you turn down the frequency, you will feel and later notice that the driver cone has an increasingly longer amplitude. I just mentioned this to indicate that it will be at the lowest frequency that a woofer cone could run up against its stops.

But I want to ask again (also judging from the comment by Nuglets) and not being familiar with the market (I make my own stuff): Do commercial cross-overs have low frequency cut-offs for woofers? As far as I know the lowest frequency cross-over only provides a high frequency cut-off at the cross-over point. (It does of course provide a low frequency cut-off for the mid-range driver, but that is not the problem being discussed here.) I also repeat that this would be easy to install in an amplifier circuit, but nobody seems to care very much.

 

[no. 5]

No, no 5, this is a basic physics thing. The same power, the same output "volume" (disregarding imperfections). The fact is that for that "same volume", i.e sound intensity, there is a velocity relationship between cone and output (again talking in principle only, disregading particular cabinet designs etc.). You would have noticed that one cannot see or even feel the cone movement in a tweeter. The lower the frequency, thus the slower the cone movement, the further it has to move to create the same pressure wave. You do not do anything from the outside to create this; it goes naturally. That is to say, if you use a signal generator as input source (it normally has a constant voltage output) and you turn down the frequency, you will feel and later notice that the driver cone has an increasingly longer amplitude. I just mentioned this to indicate that it will be at the lowest frequency that a woofer cone could run up against its stops.

ooooh, thanks for answering that for me (I was waiting a while for your response).

 

[emorphien]

I wouldn't worry too much. My new bookshelf speakers have a -3 of 42Hz (what a blessed thing, I can actually hear audio in the 40s now) and lower frequencies just roll off either gradually or precipitously as mentioned depending on the drivers and cabinet tuning. You can get frequency doubling, perhaps tripling as some said (I don't know, I've never experienced that but I have seen doubling in action often enough on some subwoofers).

Ampdog, wouldn't the same amplitude (SPL) for higher frequencies demand more power?