It's all hogwash as far as I'm concerned but then again I'm old school - 70's
and yes, I believe the room and it's dimensions affect speaker sound quality too.
One area? Yes, simplicity. This could be subdivided into other areas, is that ok?
Minimum number of drivers and hence xover points. Time-alignment
. Sealed box. Baffle Step Correction. I wonder why no manufacturers have thought of these things before 
Yes, I understand your point. I deliberately dumbed it down hoping that people would then follow my explanation further.
Let us not forget that many here are not experts in this field. Time aligning the woofer and the tweeter is confusing enough. Bringing FIR filters into this will make it worse. My intention is to help explain what is the meaning of Time-aligning the tweeter and the woofer in the traditional sense.
If I had said this from the beginning, Phase alignment is not Time alignment and aligning acoustic center of drivers doesn't mean the two drivers are time aligned, it will create even more confusion. That contradict what I said right at the beginning about phase alignment but it's true. So, bear with me, one step at a time.
Nope. Time alignment is about the arrival time of the tweeter and the woofer. If they coincide exactly, the two drivers are time-aligned.
Whether the voice coils are aligned, tilting baffle using step are all methods. If you use a step and yet sounds from the tweeter and woofer don't reach you at the same time, the drivers are not time aligned.
No, it's about time-aligning the woofer and tweeter. It means sounds from the woofer and tweeter reach you at the same time. If they do, the phase of the two drivers at the crossover frequency will be in-phase.
A text from Bob MacCarthy I found to be quite informative about time and phase alignement: Time & Phase Alignment - ProSoundWeb
I believe you are refering to this:
"Loudspeaker time-alignment usually simply referred to as "time-alignment or Time-Align" is a term applied to loudspeaker systems which use multiple drivers (like woofer, mid-range and tweeter) to cover the entire audio range. It is the technique of delaying the sound emanating from one or more drivers (greater than 2-way) to correct the transient response, improve accuracy and, in non-coaxial drivers, improve the directivity or lobe tilting at the crossover frequencies."
In a broad sense, yes. My thread is specifically about time alignment of woofer and tweeter in a 2-way speaker. When are they deemed time aligned and later how to do it so that everyone here can try it for themselves.
I do apologise, for some reason I thought you were referring to what can occur at the crossover frequency
This thread can benefit from some virtually "perfect" examples in graph form.
Simply showing what happens with a certain crossover topology and how it sums together. As different order crossover slopes do change this game even more. Making it even more complicated to follow for a lot of people.
Simply showing what happens with a certain crossover topology and how it sums together. As different order crossover slopes do change this game even more. Making it even more complicated to follow for a lot of people.
Yes, pictures are good. It's ironic that the use of words can easily make simple things complicated........easily
No, no, please don't apologize. I just want to help members understand what is the meaning of time-alignment in a 2-way speaker.
Actually, what I said earlier is inflammatory to experts. They are completely wrong, especially the part that says Phase alignment is Time alignment. It is NOT. It is the other way round. When the woofer and tweeter are time-aligned, the phase at the crossover frequency is aligned.
Yes, I'll come to that later. Have to drive my wife now to the doctor for her annual checkup. It's no fun going out in this temperature. it was -10F yesterday.
This is not correct. Correct time alignment does not mean phase alignment has also occurred. Any phase relationship between drivers can exist when time aligned.....for instance, time align and then swap polarity of one driver...still time aligned.
FWIW, here's my simplified take on time alignment, phase alignment, and to risk some more advanced discussion...linear phase alignment.
First comes time alignment...as several have noted, it is simply having sound from different acoustic centers reach a designated listening/measuring point at the same time. Can be done via geometric driver positioning or pure time delay(s). It's just a little exercise in triangulation to a particular point.
That achieved, next comes phase alignment. It is having the phase traces of overlapping drivers lay on top of each other through the region of acoustic summation. The traces don't have to be flat, they just have to have the same slope/shape and lay on top of each other. This is accomplished by considerable experience with crossover design, and measuring expertise.
Phase alignment does not mean all frequencies arrive at the listening position in phase. It means that on a frequency-by-frequency basis, any particular frequency coming from two drivers arrive in phase.
IOW, phase alignment does not mean 100Hz necessarily arrives in phase with 10kHz.
If it did, that would denote the last step, linear phase. This is where all frequencies arrive together in phase. (and of course in time too, first step)
It's accomplished with linear phase crossovers and the phase correction of drivers' natural acoustic roll-off, using FIR.
If all this has made sense, let me pose a question that finally led me to see 'what I believe is the light behind all this....'
What does it mean for all frequencies to arrive in time and in phase together?
What part of the waveform are we talking about arriving together?
Hope this helps
IOW, phase alignment does not mean 100Hz necessarily arrives in phase with 10kHz.
If it did, that would denote the last step, linear phase. This is where all frequencies arrive together in phase. (and of course in time too, first step)
It's accomplished with linear phase crossovers and the phase correction of drivers' natural acoustic roll-off, using FIR.
Hope this helps
Mark, thanks for your input. I understand what you're saying but I think it's better to leave out linear phase for the time being. That's more advanced than aligning the tweeter with the woofer.
That's what I mean by time alignment and phase alignment. When you flip one phase, you'll get cancellation. It doesn't mean they are time-aligned, just phase aligned. You still need to determine that the two sounds arrive at the mic at the same time.
Bear with me for a while longer. I will show with measurements how I time align my woofer and the tweeter.
My next post is heresy to some.
Aligning Acoustic Centers of drivers is NOT Time-Alignment
There is this believe that when you align the acoustic centers of the woofer and the tweeter, the speaker is then time-aligned.
So, one happily uses a step, tilt the baffle, dial in the delay electronically or whatever to align the acoustic centers and there you have it, a time-aligned speaker. The speaker is NOT time-aligned.
Why?
To find the acoustic centers, you measure the time difference between the drivers arriving at the mic. So far, so good. But you do this with the source directly connected to the drivers.
When you install your crossovers, there will be phase shifts. So, to determine the true arrival of sounds from the tweeter and the woofer, measurements must be taken with the crossovers installed. In other words, you need to take one of the tweeter with the high pass network, then the woofer with the low pass network. If the two signals arrive at the mic exactly, then they are time aligned.
Sorry, I have to leave for a while. I'll be back after lunch with graphs to show what I mean.
There is this believe that when you align the acoustic centers of the woofer and the tweeter, the speaker is then time-aligned.
So, one happily uses a step, tilt the baffle, dial in the delay electronically or whatever to align the acoustic centers and there you have it, a time-aligned speaker. The speaker is NOT time-aligned.
Why?
To find the acoustic centers, you measure the time difference between the drivers arriving at the mic. So far, so good. But you do this with the source directly connected to the drivers.
When you install your crossovers, there will be phase shifts. So, to determine the true arrival of sounds from the tweeter and the woofer, measurements must be taken with the crossovers installed. In other words, you need to take one of the tweeter with the high pass network, then the woofer with the low pass network. If the two signals arrive at the mic exactly, then they are time aligned.
Sorry, I have to leave for a while. I'll be back after lunch with graphs to show what I mean.
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