A history of Time Aligned Loudspeakers

[kimmosto]

I find it very helpful to separate the concept of 'time alignment' from 'phase alignment'.

'Phase alignment' sounds just phase matching, and mechanical 'time alignment' is not actual time alignment without certain XO slopes or linear phase XO because it does not necessarily produce minimum-phase total. Minimum-phase total is the only actual time-aligned because both excess phase and excess group delay are zero.
Troels Gravesen uses mechanical time alignment as stepped baffle in many DIY kits to match phase as wide band as possible to enable easy 2nd order crossover without passive all-pass sections. 2nd order IIR textbook XO produces excess group delay too so it's not "actual" time alignment.

 

[williamr]

I used to own Reference 3a Royal Master speakers. They had a sloped front baffle, but I can't remember if time alignment was the design motivation. I do remember that it had a very minimal cross over and supposedly that was a selling point.

Reference 3a Royal Master Control loudspeaker | Stereophile.com

The match between amplifier and speaker for single-ended operation is critical, which is why John Atkinson suggested I let Wavelength's Gordon Rankin lead when it came to choosing a speaker to partner his special-edition Cardinal amplifiers.

www.stereophile.com

 

[gnarly]

'Phase alignment' sounds just phase matching, and mechanical 'time alignment' is not actual time alignment without certain XO slopes or linear phase XO because it does not necessarily produce minimum-phase total. Minimum-phase total is the only actual time-aligned because both excess phase and excess group delay are zero.
Troels Gravesen uses mechanical time alignment with stepped baffle in many DIY kits to match phase as wide band as possible to enable easy 2nd order crossover without passive all-pass sections. 2nd order IIR textbook XO produces excess group delay too so it's not "actual" time alignment.

Yes, thx.

I see 'phase alignment' as having acoustically complementary phase traces throughout the critical xover summation region.
And as a necessary 'precondition' for time alignment, which then completes phase trace overlay.

And yep again, any IIR textbook XO above first will have group delay that's not 'actually' valid for time alignment.

Whether the acoustically complementary phase traces are minimum phase or linear phase doesn't matter; time alignment should be the same for either. And it will take either geometric offsets or fixed time delays.

My whole reason for bringing this up, is just to try to help folks sort thru marketing claims about time and phase alignment......

 

[Chris A]

Which do you think is more audible? A 0.1ms time [mis-]alignment, or poor vertical directivity?

I know you believe that the choice is obvious...but in my experience I'll usually take the time alignment at tweeter crossover frequencies (usually around 5-7 kHz) in home-sized listening rooms with 3-5m listening distance (~10-16.5 feet) ...if you're looking for timbre matching and subjective listening preference of multiple aperture loudspeakers--like all multiway loudspeakers not having co-axial output.

An example: BMS 4592Nd Coax XO suggestion. It wasn't until I added an additional fractional millisecond HF channel delay on the BMS 4592 HF diaphragm that I could match the timbre of the K-402-MEH with the left/right TAD TD4002 drivers on each side in my array. Vertical directivity effects and lobing didn't come into the picture (subjectively) when adjusting the crossover filter.

YMMV.

Chris

 

[amadeuswus]

Technics “Linear Phase” series
View attachment 533790

That tweeter housing... B&W's inspiration?

 

[gnarly]

I know you believe that the choice is obvious...but in my experience I'll usually take the time alignment at tweeter crossover frequencies (usually around 5-7 kHz) in home-sized listening rooms with 3-5m listening distance (~10-16.5 feet) ...if you're looking for timbre matching and subjective listening preference of multiple aperture loudspeakers--like all multiway loudspeakers not having co-axial output.

This matches my experience too.
I think time alignment becomes more critical with higher frequency's. Like being able to hear timing differences in click tracks...which I believe translates into differences in overall timbre and clarity.
I certainly don't know the timing audibility thresholds, but with my DIYs it has seemed to pay off to focus on time and phase alignment more so than vertical directivity.

 

[analogonly]

Two of the biggest proponents are/were Vandersteen and Thiel.

One of his current offerings:

Vandersteen Audio High End Speakers | Vandersteen Audio

Vandersteen Audio High End Speakers

www.vandersteen.com

No longer available new:

Thiel CS3.7 loudspeaker | Stereophile.com

One might argue that Thiel Audio's 3-series loudspeakers are the audio equivalents of BMW's 3-series sports cars: relatively affordable, but 100% about performance. Thiel has made bigger, more expensive loudspeakers than the 3s, as well as smaller, less expensive models—but the iconic Thiels are...

www.stereophile.com

 

[jkasch]

That tweeter housing... B&W's inspiration?

Don’t know. I really wanted a pair back then, but never got to hear them. Reviews were positive and i thought they looked cool.

 

[amadeuswus]

Don’t know. I really wanted a pair back then, but never got to hear them. Reviews were positive and i thought they looked cool.

The Technics SB-4500 was my first pair of speakers. Not as cool looking as the upscale model in your post. I can't swear to it after almost 50 years, but it may have had a small foam pad on the "shelf" to absorb early tweeter reflections.

 

[test1223]

Acapella - Sarastro Referenz
about 1993
Like almost all Acapella stuff very good and very expensive.

image from https://www.lite-magazin.de/

 

[robh36062]

I like the Urie coaxes. Used a delay in the crossover.

Rob

 

[Waveform Fidelity]

I find it very helpful to separate the concept of 'time alignment' from 'phase alignment'.

Time alignment is having the distances from drivers' acoustic centers, to be the same to a listening position / tuning spot.
Either accomplished geometrically via drivers' locations, or electrically with constant time delays.
So whenever I see a stepped or sloping baffle arrangement, I know the speaker designer was working towards achieving time alignment.
Generally, I tend to assume any designer interested in achieving time alignment was also interested in achieving phase alignment.

They are not the same thing. Many designs tout phase alignment (especially two and perhaps simple three ways) without any real concern for time alignment. They often use 'pseudo time', aka group delay between driver sections to achieve 'pseudo time alignment'. The difficulty of making fixed delays with passive circuity is the root of the use of pseudo delay.

Not trying to overcomplicate the thread....just trying to highlight that when discussing time aligned speakers, crossovers alone don't achieve it.
It takes either geometric delays, or fixed electronic delays mimicking geometric delays.

Yes, I too had in mind when I started the thread - strictly time aligned.

 

[Waveform Fidelity]

Yes, I too had in mind when I started the thread - strictly time aligned.

But if your believe (I do) Richard Heyser its hard to achieve because the acoustic centers move around with frequency. As a tennager we saw those Leak speakers arrive in the local HiFi shops. It was the newest thing.

 

[Waveform Fidelity]

And even KEF were doing it

 

[Doenerkunde]

Some time aligned loudspeakers from Germany:

Speaker Heaven Network 6, 1994, designed by Michael Schönhut

Speaker Heaven Network 3, 1995, designed by Michael Schönhut

Pirate Audio PAK5, designed by Michael Schönhut

Several speakers by Myro Audio, designed by Michael Weidlich

Michael Weidlich Audio Trilogy Model 1

Förster Audio FA 5.3

 

[respice finem]

Michael Weidlich Audio Trilogy Model 1

View attachment 533856

Inspired by Star Wars? (Darth Vader)

 

[ernestcarl]

Not too long ago there was a thread about the new Wilson "flagship" speakers:

New Wilson Audio flagship speakers

New Wilson Audio Autobiography flagship speakers Price: US$788,000 per pair Video with some details :

www.audiosciencereview.com

I think if I were back to my kid days (and enjoying watching transformers) I'd certainly think these speakers looked kind of pretty cool/awesome.

It would not fit modern aesthetics and the practical reality (and economy) of most modestly sized homes, however.

 

[MFA]

Not too long ago there was a thread about the new Wilson "flagship" speakers:

New Wilson Audio flagship speakers

New Wilson Audio Autobiography flagship speakers Price: US$788,000 per pair Video with some details :

www.audiosciencereview.com

I think if I were back to my kid days (and enjoying watching transformers) I'd certainly think these speakers looked kind of pretty cool/awesome.

It would not fit modern aesthetics and the practical reality (and economy) of most modestly sized homes, however.

No Wilson speakers are time aligned

 

[Torin Krell]

E. M. Long engaged in significant research in time alignment which resulted in the refinement of the Altec 604 driver as used in several Urie studio monitors. He was also an early proponent of nearfield monitoring - with the MDM-4 as one of the best example of those efforts.

 

[Snarfie]

Vandersteen Seven Mk II