From: John R. <ja...@so...> - 2007-07-01 12:30:54
|
On Sun, Jul 01, 2007 at 12:57:22PM +0100, John Rigg wrote: > On Sun, Jul 01, 2007 at 09:30:33AM +0200, Udo van den Heuvel wrote: > > Are the default delays a good starting point for this 'effect'? > > When experimenting with a recording (made outside) in my small room I > > did not get the different parts (high, mid, low) in sync. > > Compensating for delays like this is specific to each individual > speaker system. You'd have to test the impulse response of your speakers > and adjust accordingly. If manufacturers provided impulse plots it would > save a lot of work (but if people realised how bad the impulse responses > of most speakers are they wouldn't buy them ;-)). > > Actually this per-band compensation isn't a complete solution. > It only compensates for differences in the distance from the > speaker drive units to the listener (eg. the centre of a bass driver > is usually further back in the cabinet than the centre of the HF > driver). It can't do anything for group delays, which occur where > there is a slope in the amplitude/frequency response, eg. the LF roll-off > of a bass driver. The steeper the roll-off (and the greater the phase shift) > the greater the group delay. Given that a simple per-band delay can only compensate for differences in driver distance, it could be set up without knowing the impulse response. For example, on a 2-way system, measure how far back the centre of the bass driver is compared with the HF driver. Then calculate the delay that needs to be applied to the HF band: delay (seconds) = difference in distance (m) / speed of sound (343 m/s at sea level) A system sophisticated enough to compensate for group delays (which the BBE system appears to be capable of) can only be set up by measuring the individual system. John |