Can you post a waterfall of the setup with near field subs? Measured at 85db or higher with long enough impulse.
^
You're late to the party
See http://www.diyaudio.com/forums/subw...all-subs-geddes-approach-165.html#post3662887
You can see the room do its thing some 20dB or more below the direct signal.
You're late to the party
See http://www.diyaudio.com/forums/subw...all-subs-geddes-approach-165.html#post3662887You can see the room do its thing some 20dB or more below the direct signal.
Markus,
1)Arrival time of the loudspeaker at the preferred listening position.
My preferred listening position would be equidistant from the left and right main speakers.
2)After the arrival time of the various loudspeakers to be time aligned is determined, the loudspeakers are delayed to equal the "time of flight" of the loudspeaker with the longest arrival time, with any filters to be employed also in circuit. Proper polarity must be then be determined (proper polarity will result in gain in level from multiple speakers, reversed polarity will drop in level).
3) Phase and frequency response are measured, they will be smoothest when time alignment (and equalization, and acoustic crossover) is correct. Reversing polarity of a sub will result in a dip in response at the acoustic crossover point.
Art
So we have three different multiple sub approaches (Art, Markus and I). We all think that ours sounds great (Markus even claims his sounds best although he hasn't heard any of the others.) And the one thing that we all look for is a smooth LF response. Seems to me that smoothness must be far and away the most important or we would not have all come to this same conclusion. Could it be that all the rest (phase, delay, etc.) for which all of our setups would differ, is pretty much irrelevant?
We do? I would favor a DBA or a near field sub. If that's not feasible then I think Welti's SFM is the most reasonable approach.
I'm not sure how you do your optimization these days. I believe your approach changed over time?
He did, that's why he thinks that near field sounds so good.
I agree when we talk about frequencies below 80Hz. But, I consider low modal ringing as important as smooth frequency response within the listening area.
This is exactly what I have found. My subs have no delay whatsoever, and I did experiment with the feature on my DCX.
Best,
Anand.
Smoothness. That's the point to using multiple subs isn't it - to create more modes so as to approximate the sensation of infinite modes?
Or, if I understand correctly, in Markus's case, as he expresses it, to mask the room's scarcity of modes by replacing the room's modal behaviour with that of the recording's space?
Do not the two approaches amount to the same thing? As the room approaches having subjectively infinite modes do we not hear the modal behaviour of the recording's space?
Or, if I understand correctly, in Markus's case, as he expresses it, to mask the room's scarcity of modes by replacing the room's modal behaviour with that of the recording's space?
Do not the two approaches amount to the same thing? As the room approaches having subjectively infinite modes do we not hear the modal behaviour of the recording's space?
I was going to agree with you but then second thoughts tell me to think about it - I'm not sure. My doubts have something to do with masking.
If you had read my book then you would know that I have always said that good damping at LFs is critical. I said this long before I ever talked about multiple subs, so low modal decay is nothing new to me. Once you have that then I'd say that any approach that has a smooth frequency response is going to be about the same, delay won't matter.
You have a room that you have to live with unchanged, so near field subs is just about your only choice, but lets not pretend that it is superior to all others, just because you can't do any of them.
I'm aware that you have lots of low frequency damping in your room. And it's crucial. You tend to forget to mention that fact when you talk about multiple subs. People think they are getting one (smooth frequency response) with the other (low ringing). This is not the case with multiple subs. The only exception is a DBA.
Well I've already said that DBA would be my first choice - it's somewhere in my book
In my room near field sub is superior to all other practical choices and the result speaks for itself. I've posted data. I've seen a lot of data, even from dedicated spaces that perform worse - much worse. I'd like to see some data from your room too.
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Originally Posted by weltersys
1)Arrival time of the loudspeaker at the preferred listening position.
My preferred listening position would be equidistant from the left and right main speakers.
2)After the arrival time of the various loudspeakers to be time aligned is determined, the loudspeakers are delayed to equal the "time of flight" of the loudspeaker with the longest arrival time, with any filters to be employed also in circuit. Proper polarity must be then be determined (proper polarity will result in gain in level from multiple speakers, reversed polarity will drop in level).
3) Phase and frequency response are measured, they will be smoothest when time alignment (and equalization, and acoustic crossover) is correct. Reversing polarity of a sub will result in a dip in response at the acoustic crossover point.
I should point out that the charts I posted of my home system are of a single dual 12" sealed bandpass sub placed slightly off center between the sealed L/R main speakers. Since the response is smooth (enough) I have never felt any compelling need for multiple subs.
I don't use any delay on that system, or my shop system, which uses four subs and 8 L/R speakers, or my control room system which has a single sub and L/R monitors, or my kitchen and patio systems which also have a single subs and L/R speakers.
The patio system would benefit from delaying the tops to the tapped horn sub, but the path length of the horn puts it about one wavelength behind at the acoustic crossover, so it still (roughly) "lines up" in phase response and the frequency response is OK.
I use delay to align the lows, mids and highs on the sound reinforcement systems used for concerts.
Art
1)Arrival time of the loudspeaker at the preferred listening position.
My preferred listening position would be equidistant from the left and right main speakers.
2)After the arrival time of the various loudspeakers to be time aligned is determined, the loudspeakers are delayed to equal the "time of flight" of the loudspeaker with the longest arrival time, with any filters to be employed also in circuit. Proper polarity must be then be determined (proper polarity will result in gain in level from multiple speakers, reversed polarity will drop in level).
3) Phase and frequency response are measured, they will be smoothest when time alignment (and equalization, and acoustic crossover) is correct. Reversing polarity of a sub will result in a dip in response at the acoustic crossover point.
Yes, without step 1 it would be impossible to time align anything.
I should point out that the charts I posted of my home system are of a single dual 12" sealed bandpass sub placed slightly off center between the sealed L/R main speakers. Since the response is smooth (enough) I have never felt any compelling need for multiple subs.
I don't use any delay on that system, or my shop system, which uses four subs and 8 L/R speakers, or my control room system which has a single sub and L/R monitors, or my kitchen and patio systems which also have a single subs and L/R speakers.
The patio system would benefit from delaying the tops to the tapped horn sub, but the path length of the horn puts it about one wavelength behind at the acoustic crossover, so it still (roughly) "lines up" in phase response and the frequency response is OK.
I use delay to align the lows, mids and highs on the sound reinforcement systems used for concerts.
Art
So, with this new-found element of personal disclosure appearing in this thread, it turns out there isn't much for good folks to argue about.
Depending on all kinds of factors, you might benefit from alignment or you migh not be remotely able to achieve any kind of alignment or you might not need alignment or some combination of those depending on the room, damping, symmetry, speaker location, and direct or dipole, and who knows what more.
Based on reading posts, it looks to me like alignment can help at times and alignment can't help at times. Both points of view are right.
Ben
Depending on all kinds of factors, you might benefit from alignment or you migh not be remotely able to achieve any kind of alignment or you might not need alignment or some combination of those depending on the room, damping, symmetry, speaker location, and direct or dipole, and who knows what more.
Based on reading posts, it looks to me like alignment can help at times and alignment can't help at times. Both points of view are right.
Ben
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