Controlling Excursion |
Post Reply |
Author | |
tommysb
Registered User Joined: 24 April 2006 Location: Finland Status: Offline Points: 1036 |
Post Options
Thanks(0)
Posted: 24 August 2008 at 5:56pm |
When messing around with HornResp etc, I seem to be able to get a nice 1w/1m response out of certain designs, however, when you look at what happens putting a few hundred watts through them, I end up with high excursions at LF. Obviously reducing the rear chamber size can help control this, but what other ways are there to control high excursions, or what parameters in a driver can help prevent this?
|
|
Elliot Thompson
Old Croc Joined: 02 April 2004 Location: United States Status: Offline Points: 5172 |
Post Options
Thanks(0)
|
You can use a step slope to reduce the frequencies below the horns cut off. Best Regards, |
|
Elliot Thompson
|
|
tommysb
Registered User Joined: 24 April 2006 Location: Finland Status: Offline Points: 1036 |
Post Options
Thanks(0)
|
Do you mean on the x-over?
Tom |
|
Deadbeat
Old Croc Joined: 12 March 2008 Location: Singularity Status: Offline Points: 3167 |
Post Options
Thanks(0)
|
Here's a small excerpt from the diyaudio wiki:
If you use a high pass filter with an fc @ F3, the excursion will decrease approx 30% at that point. If you use a 2nd order high pass, then half an octave below fc the excursion will be reduced by at least half. After such a high pass filter is used, the excursion limited power will increase so that the power handling will be limited by excursion at fc. The actual power handling will be typically 140% of the excursion limited power hanlding at the F3 point without the filter. |
|
Away on extended leave.
|
|
tommysb
Registered User Joined: 24 April 2006 Location: Finland Status: Offline Points: 1036 |
Post Options
Thanks(0)
|
Interestingly...The predicted excursions for the 'same' model in Akabak and HornResp are quite different
|
|
David McBean
Registered User Joined: 11 January 2008 Status: Offline Points: 54 |
Post Options
Thanks(0)
|
Hi tommysb,
If you are seeing differences then it can only be because the models you are comparing are not the same :-). Hornresp and AkAbak diaphragm displacement predictions are normally identical.
Kind regards,
David
|
|
tommysb
Registered User Joined: 24 April 2006 Location: Finland Status: Offline Points: 1036 |
Post Options
Thanks(0)
|
Thanks David, I'll look into that :) - I think it's to do with front chamber approximations
|
|
AndyWave
Registered User Joined: 30 March 2008 Location: Finland Status: Offline Points: 380 |
Post Options
Thanks(0)
|
Hi
Look at driver cms value. Stiffer suspension will help when X linear starts to run out. I allways try to use driver (and enclosure design) which can take full RMS(or AES) power without exceeding X lin. Usually you can't destroy drivers in such design (except with insane power). I've also found out that different cabs like different slopes on filters. As I'm after a clear kick I allways try different filter types when doing my own presets. Many times the filter/cab combination sounds best with least phase jerks. Andy |
|
minaximal
Old Croc Joined: 26 September 2004 Location: United Kingdom Status: Offline Points: 1780 |
Post Options
Thanks(0)
|
dont forget fourth order 24db LR is effectively two 180deg filters and therefore 360deg (in phase again) and -6db at xo point, unlike others being -3db at xo.
|
|
AndyWave
Registered User Joined: 30 March 2008 Location: Finland Status: Offline Points: 380 |
Post Options
Thanks(0)
|
I should be more spesific. While I know phase rotation to be 90deg/6dBoct., the filter slopes and group delays are looking different on each filter type. For example compare chebychev and bessel types (them being the useful extremes). Both of them should be the same dB/oct.
I wanted to say that I listen how loudspeaker/filter combination sounds, like in active 3-way system, listen only mids and try different slopes or orders on highpass or lowpass. You could make ruler flat system with horrible sound? Yes? No? I think impulse response is equally important. LR filters are cascaded 2nd order butterworths, mkay. You could even ask from mrHat mkay. Suddenly there was room for fine tuning. I smell bit OT here. Andy |
|
_djk_
Old Croc Joined: 23 November 2004 Location: United States Status: Offline Points: 6002 |
Post Options
Thanks(0)
|
"Obviously reducing the rear chamber size can help control this, but what other ways are there to control high excursions, or what parameters in a driver can help prevent this? "
In order to produce sond, the driver diaphragm must move.
To produce the same sound level an octave lower, a given driver must move 4X as far (assuming the design is driven within its pass-band).
Driven below its design pass-band, the excursion increases rapidly (that's why we use a high-pass filter).
Resonant loading (tuned chambers, etc) reduce excursion at that frequency only, the same genaral 4X rule applies.
If you want loud sound, you must have a large excursion, if you want deep frequency, it must excurd even more (4X for one octave).
There is no such thing as a free lunch!
|
|
djk
|
|
Post Reply | |
Tweet |
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |