View Full Version : Speaker design and time alignment
Covenant
30-03-2009, 10:09
One aspect of speaker design which does not often get discussed is time alignment. I am talking here about ensuring that the sound from each driver reaches your ears at the same time.
Some manufacturers consider it important others seem to ignore it and I wonder where it figures in DIY design if at all.
The few speakers incorporating this principle that I have listened to, including my own, exhibit very good imaging and soundstaging properties.
Have I got this completely wrong and other manufacturers take account of it in the crossover design?
Ali Tait
30-03-2009, 11:09
Not an issue if you use a fullrange driver! :lolsign:
I've an old pair of Technics SB-7000's that are a time aligned design,and yes,there is something to be said about it.Good soundstaging and imaging as you say.Unfortunately they sound very boomy and coloured next to my statics and MLTL Fostex full-rangers.
Covenant
30-03-2009, 15:22
I am sure its one of those hi-fi subjects that has gone out of favour and will become a big issue in the future.
It seems to make sense to me-I am suprised that more manufacturers dont design with time alignment at the top of their agenda.
Where's Jim Goulding when you need him? He'll have a useful perspective on this I know.
Steve Toy
31-03-2009, 17:31
Speaker brands renowned for good time alignment properties include Focal, Avalon (they also encorporate foam in the grills that deal with diffraction), Peak Consult and Gamut amongst others.
And then I found these http://www.acoustic-energy.co.uk/Product_range/Linear_series/Linear_three.asp
Covenant
31-03-2009, 18:22
Where's Jim Goulding when you need him? He'll have a useful perspective on this I know.
Jim Goulding is the diffraction guy isnt he? No I dont think time alignment is the same thing. His products help prevent sound diffusing so it arrives at your ears 'concentrated'. You can get some of this effect by cupping your hands around the back of yours ears so that your thumbs touch your ear lobes.
In a time alignment design the crossover ensures the drivers are in phase and the positioning of the drivers maximizes the phase coherence at the listening position. Most speakers mounted on a flat baffle dont achieve this.
I suppose it must be quite complex to design but no doubt someone will be along with a nifty compuer programme to prove me wrong.
Steve Toy
31-03-2009, 20:56
Sloping baffles and/or time alignment through the crossovers are two methods of ensuring speaker phase coherence.
The Hecos Celan 700s I use seem to time and image rather well despite the marketing blurb not making any noises about time alignment. I guess that as with everything else, you just have to listen....
Ammonite Audio
01-04-2009, 13:14
I had a demonstration of correct and incorrect time alignment using Focal Grande Utopias recently (not that I was buying!). The Grandes have a crank handle arrangement that changes the angle of the upper elements. The difference was rather marked, and I have to admit to being surprised, not having previously taken time alignment seriously. Definitely food for thought.
StanleyB
01-04-2009, 13:28
Some of the old B&W speakers had the front design of their cabinet time aligned.
Jim Goulding is the diffraction guy isnt he? No I dont think time alignment is the same thing. His products help prevent sound diffusing so it arrives at your ears 'concentrated'. You can get some of this effect by cupping your hands around the back of yours ears so that your thumbs touch your ear lobes.
In a time alignment design the crossover ensures the drivers are in phase and the positioning of the drivers maximizes the phase coherence at the listening position. Most speakers mounted on a flat baffle dont achieve this.
I suppose it must be quite complex to design but no doubt someone will be along with a nifty computer programme to prove me wrong.
I take your point, but isn't timing - or the preservation of it (admittedly of secondary reflections) - part of diffraction? I'm sure Jim would have some interesting input on the subject.
My Fave speakers are Royds, which use a modified 1st order crossover; Joe Ackroyd had this timing in mind as he developed his range. Below is a copy of some literature I have on his Revelation range - The last Royds to be produced. This, as well as much info on Royds, can be found on a new site put up by Arfa here (http://www.roydaudio.com/).
"The aim of hi-fi is to reproduce sound as accurately as possible. This means that it must reproduce the correct musical note, at the correct time, for the correct length of time, and as near as is practical at the correct volume. Of course, “correct” means that sound which was on the original recording.
In order to do this, loudspeakers must be critically damped at all frequencies, and have the least possible phase distortion. Phase distortion is a time delay dependent on frequency: the lower the note or frequency, the longer the time delay for the same phase shift.
The Royd Revelation Range is a considerable step forward, compared with any other type of design.
The use of compound reflex bass loading in these loudspeakers reduces the phase shift compared with standard reflex bass loading by more than 75%, and is 3 times less than a closed box or acoustic suspension type cabinet. A transmission line cabinet has more bass distortion than a closed box, because it adds a further 180° phase shift to that produced by a closed box. Compound reflex bass loading also ensures that all bass frequencies are critically damped and that the Revelation range of loudspeakers reproduce frequencies down to 20Hz in the listening room.
The Royd Revelation Range employs first order crossovers. This type of crossover produces the least possible phase distortion, and introduces no other distortions or resonances.
All models perform at their best with high quality amplification."
hifi_dave
01-04-2009, 21:37
Don't forget the Grandaddy of 'time aligned' speakers - the Tannoy Dual Concentric.
Magna Audio
03-04-2009, 09:36
As a 15" Tannoy convert I agree with that.
But it's not only alignment they do so well it is percussion, piano and well every thing else too to my ears. Even my old pair saw off the £3000 ProAc D25's with consumate ease for me.
Plenty of 15" Tannoy DIY going on - I'm planning rectangular GRF ~200L cabs myself as the 70's and 80's and indeed some of the earlier simple box designs don't do the drivers full justice.
hifi_dave
03-04-2009, 10:01
Totally agree. To my ears 'real' DC's do just about everything right except fit unobtrusively in the average British room.If you're an enthusiast, that is of little concern though.
I have a pair of immaculate LGM's with 12 inch drivers (amongst others) and they are 'in yer face' with little bass. What there is, is clean and dynamic but no warmth or extension. I guess they need larger cabinets but what do I go for and how can someone whose cabinet making skills are close to zero, make a decent job. :scratch:
Actually, I'm going to ask this question in 'The Drawing Board' as that is a more appropriate place I guess.
jimdgoulding
16-04-2009, 14:30
Most assuredly, time alignment of drivers in multiple driver systems is important to a cohesive presentation of information. Some speaker manufacturers attempt to address this in their crossovers while others physically stagger/align the voice coils of their drivers so information produced by each arrives simultaneously as has been mentioned. Most, however, ignore this, presumably for economic and/or cosmetic reasons.
What diffractionbegone baffle pads do is to simply preserve the first arrival of waveforms in any case from the physical reradiation and contamination to them by reflection off cabinet surfaces and edges. Regards this, some manufacturers off set their tweeters from center so this arrives spread out over time making it less audibly invasive while others make their cabinet edges non parallel for the same reason or take their tweeters out of the box altogether. Diffractionbegone mimmicks the latter by absorbing the secondary radiation. It's all the same to waveform behavior. In any and every case, it is worthwhile to get and maintain transient and first arrival info right.
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