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In Reply to: Re: Very interesting post Sir. Thank you posted by Zene on May 21, 2006 at 04:43:23:
To reiterate:
Ideally you want all vc's in the same vertical plane!!!
If this is not possible it is better to have the higher range vc's further away from the listener then the lower range coils as opposed to the other (more usual) way around.Its usually coaxial drivers where you can't physically align the vc's but all coaxials I know that are worth owning (Tannoy and... err, Tannoy and well Altec, may be) have the tweeter coil further back and here the very real advantage of having a point source (lack of comb filtering for instance) far outweighs the mostly theoretical disadvantage of slightly imperfect vertical alignment. And the dis advantage is mostly theoretical since the only time-related connection between a fundamental and its harmonics is that harmonics are never produced before the fundamental and usually after. Think of a plucked string: It swings at its resonant frequency (fundamental) until the vibration reaches the end of the string and gets reflected back by its termination (saddle and bridge if its a guitar) when these reflections start to interfere with the original vibration harmonics are produced.
So the time when the earliest harmonics appear depends on the string length.For Tannoys the physical delay between woofer and tweeter is about 2ms which is too short to be noticed. (Don't know about other coaxials; measure the distance and work out how long sound takes to travel it, if you can be bothered)
It is also too short to be fixed with anything other then a digital delay which would require an unecessary step of conversion and all its problems if, like me, you still use analog sources. There is the passive all-pass Tannoy used on some speakers but it creates more problems then it solves.
Ever noticed that it is only owners of regular speakers who point out the alignement thing?
My guess is that they are just trying to defend their choice of an inherently inferior and substantially cheaper design. Never heard a Tannoy owner complain...Not quite sure about your last two questions, Zene.
But I am adding supertweeters and two subwoofers to my Tannoys. I will make sure that the subwoofer coils are aligned with the Tannoy LF coil ( I am building the subs myself) and
I will recess the supertweeters in a waveguide so the ribbon ( I like ribbon tweets) is aligned with the HF coil. If neither were possible I'd make sure the subwoofer coil is slightly in front of the Tannoy coil and the supertweet slightly behind.
The waveguide also helps controlling HF dispersion to something closer to the Tannoy tweeters 90deg. but delving deeper into this would be a completely different thread...Of course for passive xovers all bets are off due to the unavoidable phase shift introduced by them. Although there is at least one very clever design which uses this fault to its own advantage and that is Tannoy. Tannoy drivers with AlNiCo magnets (up to HPDs) have their tweeter coil a quarter wavelength (at xover frq.) behind the woofer and with cunning choice of slopes this results in an in-phase output! But this too is not in time as the tweeter is delayed by exactly one cycle.
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Follow Ups
- Re: Very interesting post Sir. Thank you - b.l.zeebub 15:40:09 05/21/06 (2)
- Re: Very interesting post Sir. Thank you - Zene 18:25:28 05/21/06 (1)
- Re: Very interesting post Sir. Thank you - b.l.zeebub 03:20:50 05/22/06 (0)
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