Hi everybody,
On some tracks my loudspeakers (Pensil 10.2) exhibit a very worrying behaviour: The cone excursion just goes crazy, while the music is not playing any low frequency notes. Now, I have previously noticed this on my previous loudspeakers, a pair of Tannoy D300's.
What could be the cause? Could it be the amp? It's a hybrid amp, a Unison Research Unico. Could dying tubes in the pre amp stage cause this kind of behaviour?
On some tracks my loudspeakers (Pensil 10.2) exhibit a very worrying behaviour: The cone excursion just goes crazy, while the music is not playing any low frequency notes. Now, I have previously noticed this on my previous loudspeakers, a pair of Tannoy D300's.
What could be the cause? Could it be the amp? It's a hybrid amp, a Unison Research Unico. Could dying tubes in the pre amp stage cause this kind of behaviour?
Is your source a record player? It could be some kind of ELF feedback loop. If it was an amp power supply AC leak, you'd likely hear it at 60Hz or 120Hz (or make that 50Hz or 100Hz in your country?) depending on design.
IG
IG
No, the source is a cd player. I also played the offending tracks on my dvd player, with the same results.
Agreeing with Cal here.
I've heard of studios that have picked up near-by trains and things like that, which add a lot of LF content.
To be on the safe side (for your speakers/amp's sake), it would probably wise to add in an infrasonic filter, to cut out the frequencies that'll cause silly excursion with no output.
Chris
I've heard of studios that have picked up near-by trains and things like that, which add a lot of LF content.
To be on the safe side (for your speakers/amp's sake), it would probably wise to add in an infrasonic filter, to cut out the frequencies that'll cause silly excursion with no output.
Chris
i have found this with some 'action' movie DVDs. Some SFX 'rumbles' are subsonic and i have no idea why they are present, i always thought the BW of CD/DVD was 20-20k, but these are maybe 5hz tones. I can only imagine that they are to move air and provide 'IMPACT', but they just seem to waste my amps power, and unload the speaker.
I have a RadioShack amp that produced 1Hz excursions on the woofer when music was turned up. Replacing a bulging and cracked capacitor seemed to fix the problem. Perhaps something to check?
Also, you could try some very large caps on the audio output, to reduce signals below 20Hz, for example. That is if you don't fix the problem another way...
Also, you could try some very large caps on the audio output, to reduce signals below 20Hz, for example. That is if you don't fix the problem another way...
I have had a similar situation with my McIntosh pre-amp, same problem as mentioned by enigmaticEntity.
Only question I have is where Swifty mentions that this happens only 'on some tracks', pointing to perhaps a different problem altogether.
Only question I have is where Swifty mentions that this happens only 'on some tracks', pointing to perhaps a different problem altogether.
I think we all have that problem. Interesting to find out if Swifty is the same as most of us. Like Chris says: Studio too close to train tracks or is there is actually something wrong. 🙂
It's something right on the source is my guess. I've come across that before. Particularly pop music or movies. They'll have frequencies that cause total unloading.
With the right sub, these sometimes add a lot of enjoyment to the sound.
With the right sub, these sometimes add a lot of enjoyment to the sound.
Well,
I just went over to my neighbour to see whether I could repeat this effect on his stereo, a Cambridge Audio receiver, CD- player and speakers. The track I played is "Blood Embrace" by Bonny Prince Billy and Matt Sweeney on their album "Superwolf". On my neighbours set there is no hint of the excessive cone excursion that is so evident on my set. Feel free to test this for yourself on your set if you happen to have this cd in your collection.
Another track the has this same strange effect on my set is "Recorda Me" by McCoy Tyner from the album "New York Reunion" on the Chesky label.
Could it be that some amps/receivers limit the lower end bandwith? This would explain why I cannot reproduce the phenomenon on my neighbour's set...
Any other bright ideas?
I just went over to my neighbour to see whether I could repeat this effect on his stereo, a Cambridge Audio receiver, CD- player and speakers. The track I played is "Blood Embrace" by Bonny Prince Billy and Matt Sweeney on their album "Superwolf". On my neighbours set there is no hint of the excessive cone excursion that is so evident on my set. Feel free to test this for yourself on your set if you happen to have this cd in your collection.
Another track the has this same strange effect on my set is "Recorda Me" by McCoy Tyner from the album "New York Reunion" on the Chesky label.
Could it be that some amps/receivers limit the lower end bandwith? This would explain why I cannot reproduce the phenomenon on my neighbour's set...
Any other bright ideas?
Any non-sealed speaker system, bass reflex, open baffle, etc - it will be suseptable to cone pumping below Fs. If your sure there's nothing wrong with your equipment, I'd try an infrasonic filter like chris661 recommended.
Mike
Mike
The Pensil 10.2 is a ported box, around 2.38 cubic feet, with a 11 square inch port only 3/4 “ deep.
The Fb is probably about 60 Hz, any appreciable power below that will make the speaker flap, and will produce no appreciable sound output.
The Low B on a five string bass is 32 Hz, (almost an octave lower than the Pensil 10.2's Fb), you don’t need to look too hard to find music tracks that have plenty of LF energy down that low.
You can download sine wave tones and easily determine the exact Fb, the cone movement will be minimum there, but will go up rapidly below Fb.
You could add a shelf duct to the port and tune lower, but though it will go lower, the speaker will not be as loud at the new Fb as the tuning it has now.
If you don't want to change the enclosure, best use a HP filter as has been suggested.
Some amps are DC coupled others are AC coupled using input and/or output coupling caps. This would limit the low frequencies.
What amp are you using?
Oops. Nevermind. Just noticed you mentioned your amp in the first post.
Don't see any output coupling caps so unless it has a cap coupled input, it's a DC coupled amp.
se
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Could you elaborate? I have no experience fiddling with filters/electronics. Do I need to place a cap between the source and the pre-amp input?
I’d like to hear the elaboration too, for a capacitor to work as a HP it needs to be precisely matched with the load impedance. The HP frequency needs to be specific to the box tuning (Fb).
The capacitor, if properly tuned, only will provide a 6 dB per octave filter, while your speaker probably needs a 12 dB per octave filter to protect it from over excursion below Fb.
That said, a little cone flop won’t damage the speaker, but you should look up the Xmax and Xlim (or Xmech, the excursion limit that will damage the speaker) specifications and make sure you are not close to Xlim.
You may want to look at post #14 again.
just put it inline with the In+, need more bass, increase the size, need less decrease it. It forms a high pass filter together with the resistor to ground you will find somewhere connected to the input. I have some LP's that scare the bejuices out of me the way they can flop my drivers around, I suspect a slight warp...
Yes, it's the source material. I've experienced this with all ported loudspeakers. Post #14 describes the scenario well. Any reasonable amount of output much below the tuning freq will cause the driver to "unload". With quick 1-5 Hz pulses (don't know why they're throughout so many tracks, but they are), the driver just flops around and can be damaged fairly easily, depending.. particularly smaller full-range drivers. The person's system you tried could have used a sealed enclosure and/or built-in high-pass filter. Just remember though that adding a high-pass filter will result in significant increase in delay and phase shift at low frequencies. With the box tuning supposedly around 60 Hz, it's likely already high enough. Only add it if you have no other choice and really must do it to protect your drivers. That's my recommendation.
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