Time Alignment of Speaker Drivers

[RegularStereoGuy]

Is it still a thing?

 

[DVDdoug]

Yes, it's still a thing. Physics hasn't changed much.

Phase alignment is more important than time-alignment (they are related). So depending on crossover design, physical alignment might not be optimal. And a few degrees of phase misalignment probably isn't a big deal.

 

[RegularStereoGuy]

Yes, it's still a thing. Physics hasn't changed much.

Phase alignment is more important than time-alignment (they are related). So depending on crossover design, physical alignment might not be optimal. And a few degrees of phase misalignment probably isn't a big deal.

I ask only because I don't see many speakers out lately with that design (the tweeter set in to align with the centerline of the woofer cross-section).

https://m.media-amazon.com/images/I/81On3TunZAL._AC_.jpg

 

[Bleib]

In some speakers (Guru QM60)

 

[voodooless]

I ask only because I don't see many speakers out lately with that design

You’re probably not looking hard enough. If you check the latest speaker reviews at ASR or from Erin, you’ll find that the vast majority of them has some kind of waveguide.

 

[DWPress]

Many active speakers with DSP now can compensate for delays in software without sacrificing horror story baffle steps on the tweeters like shown above.

 

[Bleib]

horror story baffle steps on the tweeters like shown above.

lol

 

[RegularStereoGuy]

This Genelec is close to what I have in mind, but most Gennys are active:

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcS0EShIaYgb7pyUuBjGmuiuKWaFU0jQLcr0lg&s

I'm looking for passive home stereo speakers with similar alignment.

 

[moonlight rainbow dream]

It depends on crossover topology. With lower order crossover slopes, it is necessary to get good summation.

 

[RexrothPigeon]

This Genelec is close to what I have in mind, but most Gennys are active:

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcS0EShIaYgb7pyUuBjGmuiuKWaFU0jQLcr0lg&s

I'm looking for passive home stereo speakers with similar alignment.

are you looking for a particular visual aesthetic, or is there a sonic problem you're trying to solve for?

 

[RegularStereoGuy]

are you looking for a particular visual aesthetic, or is there a sonic problem you're trying to solve for?

Firstly, my long-term memory is considered among friends and colleagues as "uncanny", whereas my short-term memory is practically non-existent.

So I remember about 20 years ago, I listened to a speaker, somewhere, that was configured as I illustrated, and like that Genelec I linked to. How do I describe the sound other than as very "tight" and "focused".

 

[norman bates]

it can be ?

I had a 10" woof with whizzer run wide open (naturally rolling off above 2khz).
I ran a single cap on the tweeter.

When the tweeter was flush with the front baffle, you could NOT hear a dip when you inverted the phase to the tweeter.
You could easily perceive a dip (inverting the phase) when the tweeter was slid back a few inches..............................

 

[voodooless]

Many active speakers with DSP now can compensate for delays in software without sacrificing horror story baffle steps on the tweeters like shown above.

You can delay passively as well using an all-pass filter, tough it’s rarely used because of it’s component count. You can also just add a waveguide or slant the baffle to improve alignment, no needs for ugly steps. Even the Egyptians figured that out early on

 

[RegularStereoGuy]

it can be ?

I had a 10" woof with whizzer run wide open (naturally rolling off above 2khz).
I ran a single cap on the tweeter.

When the tweeter was flush with the front baffle, you could NOT hear a dip when you inverted the phase to the tweeter.
You could easily perceive a dip (inverting the phase) when the tweeter was slid back a few inches..............................

You mean polarity.

Phase is just the audible effect of manipulating polarity.

 

[voodooless]

You mean polarity.

Phase is just the audible effect of manipulating polarity.

No! Phase is frequency-dependent, whereas polarity is not. While closely related, they are not the same thing.

Regarding the tweeter, you are correct, that is a polarity swap.

 

[multichannel_guy]

lol

His momma said he was very intelligentellyjelly.

 

[NTK]

Is it still a thing?

Unfortunately, the acoustic center of the woofer is not where the dust cap is. It is some distance in front of the driver and is typically outside the loudspeaker enclosure. Therefore, moving the tweeter backward is going the wrong direction if you want to physically "time align" the drivers.
(Picture source: https://www.aes-media.org/sections/uk/meetings/AESUK_lecture_0604.pdf, slide 4)

 

[Arindal]

the acoustic center of the woofer is not where the dust cap is. It is some distance in front of the driver and is typically outside the loudspeaker enclosure.

You are talking about the plane from where the wavefront is virtually emanating in the time domain taking the speed of sound into account, or the virtual center of the presumed omnidirectional spherical wavefront from geometrical point (for polar or directivity calculation)?

Both are not necessarily at the same distance from the listener or microphone.

You can delay passively as well using an all-pass filter, tough it’s rarely used because of it’s component count.

A classic all-pass filter affecting solely the phase/time domain but not the amplitude, is indeed a rare thing in passive crossovers. Not overly useful for mid/high frequency application, and a pretty costly thing to design in the bass region.

But it should be taken into account that the minimum-phase behavior of every analogue filter does induce a group delay or phase distortion not dissimilar to a part of an allpass. That is particularly the case with high-order and/or high-Q low-pass filters, basically shifting the phase of all signals they let pass more or less. Inverted tweeter polarity compared to the midrange leading to perfect summation in amplitude on axis, is an indication of a +180deg phase shift of the lowpass, which is in theory the result of a textbook Butterworth-style lowpass 2nd order.

Geometric time alignment in passive loudspeakers basically makes sense only if all the latter effects are taken into account and confirmed by measurements. Achieving equal distance between drivers and the ears alone, would not solve all the problems.

 

[Looneybomber]

@RegularStereoGuy, in addition to waveguides on a tweeter and various baffle shape manipulations (e.g., SVS Ultra Evolution series) to time align drivers, there are convex woofers/mids. Accuton and Bliesma are two OEMs that come to mind. This Marten Quintet speaker uses drivers from both, I think.

 

[voodooless]

Unfortunately, the acoustic center of the woofer is not where the dust cap is. It is some distance in front of the driver and is typically outside the loudspeaker enclosure. Therefore, moving the tweeter backward is going the wrong direction if you want to physically "time align" the drivers.
(Picture source: https://www.aes-media.org/sections/uk/meetings/AESUK_lecture_0604.pdf, slide 4)

View attachment 502613

That is quite interesting! Never seen that before. But this is not quite what we're after, is it? This mostly shows the point in space at which the waves appear to originate. This is, however, as far as I can understand, separate from the timing aspect of it.