Hello, I hope some of you out there know DSP crossovers for PA purposes that allow not only active x-over, EQ, delay, peak and RMS limiters, but advanced features such as excursion limiting and / or automatically raising a protective ("subsonic") high pass filter frequency depending on level, to avoid excessive excursion. Sort of a smart limiter that allows to maximize a woofer's (low distortion) output sacrificing some of its lowest frequency output where it can't reproduce the wanted SPL.
What can you recommend?
What can you recommend?
I haven't used it but the Linea Research ASC48 offers these features or you could use a something by Symetrix/QSC/Biamp that allows side chain limiting to do the excursion limiting. https://www.diyaudio.com/community/...or-excursion-and-excursion-measurment.375676/
Thank you, kipman725! The Linea Research ASC48 really seems to do everything I was looking for. I just wonder how I should set up the Xmax limiter for a particular driver / enclosure. Do you have any idea, or another link?
hmm measure the impedance of the enclosure and replicate in hornresp (sealed/vented with known driver). More complicated alignments I'm not sure as making a model would require a lot more measurments.
Can you maybe answer another question, or give me your opinion about it.
PA driver manufacturers generally specify Xmax, some also Xlin and Xdam.
Xlin is usually defined as (voice coil length - air gap height) / 2, at least in HiFi circles. PA manufacturers instead typically specify an Xmax value where many add 1/3 or so of the voice coil length, although it is clear that the voice coil driving force reduces from the point where it doesn't fill the whole air gap anymore, leading to nonlinear distortion.
For instance, for its 10MC700Nd, Beyma specifies an Xmax of 7mm, whereby they define this as
(Lvc - Hag)/2 + (Hag/3,5), where Lvc is the voice coil length and Hag is the air gap height. So this already allows 3mm more than Xlin, which they don't list as such, but can be calculated from the listed Lvc and Hag to be only 4mm.
So these 7mm already "allow" excursion well beyond the more conservative Xlin. Is it advisable to use this excursion range at all, if you want your speaker to work with low distortion?
On top of that, Beyma's data sheet even specifies an Xdam value of 48mm p-p, or 24mm in each direction.
How much of this apparently huge headroom is of practical use?
PA driver manufacturers generally specify Xmax, some also Xlin and Xdam.
Xlin is usually defined as (voice coil length - air gap height) / 2, at least in HiFi circles. PA manufacturers instead typically specify an Xmax value where many add 1/3 or so of the voice coil length, although it is clear that the voice coil driving force reduces from the point where it doesn't fill the whole air gap anymore, leading to nonlinear distortion.
For instance, for its 10MC700Nd, Beyma specifies an Xmax of 7mm, whereby they define this as
(Lvc - Hag)/2 + (Hag/3,5), where Lvc is the voice coil length and Hag is the air gap height. So this already allows 3mm more than Xlin, which they don't list as such, but can be calculated from the listed Lvc and Hag to be only 4mm.
So these 7mm already "allow" excursion well beyond the more conservative Xlin. Is it advisable to use this excursion range at all, if you want your speaker to work with low distortion?
On top of that, Beyma's data sheet even specifies an Xdam value of 48mm p-p, or 24mm in each direction.
How much of this apparently huge headroom is of practical use?
Beyond xmax isn't very useful at the frequencies where xmax would be exceeded as the sound is compressed. This is a graph of the relative change in response of one of my subwoofers under high voltage sweeps:
Ignore beyond 50Hz as you start to see the amp misbehave. The box is tuned to ~30Hz and you can see the compression maximum below 50Hz corresponds to the maximum excursion of the driver ~40Hz. At this frequency the box will simply not get appreciably louder so there is no point putting more power in. Outside of this the box can get louder but the frequency response will be altered. My opinion is that unless your trying to get extra bass extension using side chain limiting or amplitude dependent high pass filtering the best solution is using a combination of high pass filter and look ahead peak limiting to avoid over excursion.
Ignore beyond 50Hz as you start to see the amp misbehave. The box is tuned to ~30Hz and you can see the compression maximum below 50Hz corresponds to the maximum excursion of the driver ~40Hz. At this frequency the box will simply not get appreciably louder so there is no point putting more power in. Outside of this the box can get louder but the frequency response will be altered. My opinion is that unless your trying to get extra bass extension using side chain limiting or amplitude dependent high pass filtering the best solution is using a combination of high pass filter and look ahead peak limiting to avoid over excursion.