more on confused signals april 20
in [Live Sound]
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From: Rupert on 4 May 2008 11:17 On May 3, 9:38 pm, "Peter Larsen" <digi...(a)hotmail.com> wrote: > Peter Larsen wrote: > >> Rupert wrote: > >>> .. Damping issues and power losses occur regardless of what > >>> speaker you have connected at the other end of the cable. Of course, > >>> if the speaker is not running low register frequencies then damping > >>> isn't as much of an issue, > >> Why would damping be relevant in the bass range but not in the rest > >> of the tonal range? > >>> Rupert > >> Peter Larsen > > I got an emailed follow up from Rupert, first I thought I had goofed and > mailed rather than posted, OE makes that error easy, at least for me, but > no - so was not the case. I will then assume that he made that error or > cc'ed a follow up that just hasn't arrived yet and post my emailed reply, > hoping that it is not an error to so do. > > Hi Rupert, > > did I goof and mail rather than post ... no, but outlook express makes that > error easy, bear with me for assuming that was, what happened to you. > > > Damping is a issue of total system behavior both electrically and > > mechanically. Woofers due to their larger mass tend to keep ringing > > when unloaded. > > What makes you think that smaller units vibrating at a higher frequency will > not ring, what difference in newtonian laws apply? > > > The same is generally not true of mid and high > > frequency drivers. > > There is no reason why it should so be that I am aware of. What matters is > for how many cycles they ring, not now many seconds or microseconds. > > > So when you have relatively poor electrical > > damping, it tends to affect the low frequency drivers, especially > > subs. > > First yoi assert and then you use the assertion as proof in the next > sentence. > > > I suppose I should have clarified I was speaking of driver type > > more so than frequency range per se. And of course this would be in > > situations with direct connected amps. In case of passive full range > > boxes, if there is a choke across the woofer terminal in the x-over > > network, that would be an effective damper. > > My understanding is that the single largest reason for the dramatic > difference in quality between fully active and passive systems is that there > is damping of all loudspeaker units. > > > Rupert > > Kind regards > > Peter Larsen The compliance of mid and HF drivers is much, much stiffer compared to low frequency drivers, so electrical DF is not nearly as much of an issue. There is always going to be some ringing which varies with frequency in any driver regardless of electrical damping and this is one reason why all drivers have inherent distortion. But as far as which types of drivers benefit particularly with good electrical damping, it's low frequency drivers due to their large mass vs. relatively weak compliance of spider and surround components. Now I'm no speaker designer or engineer, but this is what I've learned over the years from those that are and I see no reason not to take them at their word. Other then reducing voltage drop in the wire, thicker or doubled up wire is generally used for subwoofers in sound reinforcement because of the increased damping factor. Smaller gauges are often used tops since you usually need to pack more wires into a single connector and the DF is not as much of an issue. But don't my word. Here's a brief paper by Chuck McGregor, formerly of EAW & Community: http://www.prosoundweb.com/studyhall/studyjump.php?pdf=df As for your assessment about why active systems are better then passive speaker systems, DF is only one factor. Other factors that improve with individual amps for each bandpass are greater power handling due to the use of steeper crossover slopes between the band passes resulting in greater driver headroom and output, less combing from driver to driver through the crossover region since the overlap is reduced from steeper crossover slopes, no crossover components to saturate and create distortion and waste some energy as heat, and the ability to EQ and time align the individual bandpasses independently. Rupert
From: Phil Allison on 4 May 2008 20:57 "Rupert" The compliance of mid and HF drivers is much, much stiffer compared to low frequency drivers, so electrical DF is not nearly as much of an issue. ** Wrong. The fact that mid and HF drivers are normally not driven at or near their resonant frequencies mitigates the need for high DF numbers. In fact, many mid and HF drivers have large mechanical and electrical resonances - larger than typical bass drivers do. There is always going to be some ringing which varies with frequency in any driver regardless of electrical damping and this is one reason why all drivers have inherent distortion. ** Gobbledegook. But as far as which types of drivers benefit particularly with good electrical damping, it's low frequency drivers due to their large mass vs. relatively weak compliance of spider and surround components. ** Wrong again - see above. Now I'm no speaker designer or engineer, ** Really ?? but this is what I've learned over the years from those that are and I see no reason not to take them at their word. ** You need to find some better advisers - Rupert. Other then reducing voltage drop in the wire, thicker or doubled up wire is generally used for subwoofers in sound reinforcement because of the increased damping factor. ** Horse poo. Smaller gauges are often used tops since you usually need to pack more wires into a single connector and the DF is not as much of an issue. But don't my word. Here's a brief paper by Chuck McGregor, formerly of EAW & Community: http://www.prosoundweb.com/studyhall/studyjump.php?pdf=df ** Pheeeewww !! That " paper " is total BOLLOCKS from beginning to end. Full of myths, confusions, half truths and plain nonsense. Amazing what you can find on the web - ain' it ? ...... Phil
From: Rupert on 4 May 2008 23:31 On May 4, 8:57 pm, "Phil Allison" <philalli...(a)tpg.com.au> wrote: > "Rupert" > > The compliance of mid and HF drivers is much, much stiffer compared to > low frequency drivers, so electrical DF is not nearly as much of an > issue. > > ** Wrong. > > The fact that mid and HF drivers are normally not driven at or near their > resonant frequencies mitigates the need for high DF numbers. > > In fact, many mid and HF drivers have large mechanical and electrical > resonances - larger than typical bass drivers do. Interesting. Hadn't heard that before but it makes sense. Thanks for the info. Rupert
From: Phil Allison on 4 May 2008 23:50 "Rupert" "Phil Allison" > > The compliance of mid and HF drivers is much, much stiffer compared to > low frequency drivers, so electrical DF is not nearly as much of an > issue. > > ** Wrong. > > The fact that mid and HF drivers are normally not driven at or near their > resonant frequencies mitigates the need for high DF numbers. > > In fact, many mid and HF drivers have large mechanical and electrical > resonances - larger than typical bass drivers do. Interesting. Hadn't heard that before but it makes sense. Thanks for the info. ** See page 3 and figure 6 for the impedance curve of a JBL 2425 driver. http://www.jblpro.com/pub/technote/tn_v1n08.pdf There is an impedance peak around 500-600 Hz that rises to over 30 ohms. This area must be damped, filtered & avoided. ...... Phil
From: Peter Larsen on 5 May 2008 00:02
Rupert wrote: > As for your assessment about why active systems are better then > passive speaker systems, DF is only one factor. Other factors that > improve with individual amps for each bandpass are greater power > handling ... Greater power handling is not about sound quality, which was what I referred to, another reason is of course that crossover slopes are easier to keep as intended. > due to the use of steeper crossover slopes between the band > passes resulting in greater driver headroom and output, This is not about active vs. passive. > less combing > from driver to driver through the crossover region since the overlap > is reduced from steeper crossover slopes, Nor is this. > no crossover components to > saturate and create distortion and waste some energy as heat, and the > ability to EQ and time align the individual bandpasses independently. There is no difference between designing an active and a passive cross-over, but it is a lot easier to make an active cross-over do what you want it to do ... indeed! Phil has addressed some other issues very well and included a very interesting link, skipping those, thanks! > Rupert Kind regards Peter Larsen |