Ask an Acoustic Engineer (me)

[BigAl205]

A strobe light and film camera with a synced shutter speed would catch the driver in a stand-still position, since it catches all light at once. A digital camera would catch it at a distorted angle due to the way it scans the image one line at a time.

[Kb86]

Question pls. Mine is 3 ways front.
Question 1:
Which methos is better approach? and why?


Question 2: when doing all of that matching and summing, do i use spatial measurements or headrest fix measurements?


Method1:
-Tune individual channel to match target curve
- sum whole Left channel to match target curve. See sum at xover point and adjust TA for Left speakers. Link delay for whole left speakers, that TA now fix. after this consider whole left drivers is one Left Speaker.
- sum whole Right channel, same process with Left. now is whole Right speaker

• Sum 3 ways Left speaker and 3 ways Right speaker

adjust TA thus dip could be move to less noticeable higher frequency above 1000hz


method 2

• Tune individual channel to match target curve
• sum L&R tweeters, adjust TA, EQ Tweeter pair to target curve
• sum paired midranges
• sum paired woofers
• now consider that 3 pairs are center 3 ways speaker
• adjust TA between those 3 pairs to sum better at xover.

Thank you.

[Jdunk54nl]

Question pls. Mine is 3 ways front.
Question 1:
Which methos is better approach? and why?


Question 2: when doing all of that matching and summing, do i use spatial measurements or headrest fix measurements?


Method1:
-Tune individual channel to match target curve
- sum whole Left channel to match target curve. See sum at xover point and adjust TA for Left speakers. Link delay for whole left speakers, that TA now fix. after this consider whole left drivers is one Left Speaker.
- sum whole Right channel, same process with Left. now is whole Right speaker

• Sum 3 ways Left speaker and 3 ways Right speaker

adjust TA thus dip could be move to less noticeable higher frequency above 1000hz


method 2

• Tune individual channel to match target curve
• sum L&R tweeters, adjust TA, EQ Tweeter pair to target curve
• sum paired midranges
• sum paired woofers
• now consider that 3 pairs are center 3 ways speaker
• adjust TA between those 3 pairs to sum better at xover.

Thank you.

As far as method, try and see which one produces better results for you! I always check all speaker pairs that will be interacting so kind of do both of what you are talking about.

for measurements, eq needs spatial, time needs single point in space. You can’t time set time for more than a single spot, well you could set for multiple spots to have the best possible, but that means no spot is perfect and it would be a compromise. But that would be for multiple seats, not one seat. One seat one spot for time, but spatial around the head area for eq.

[Kb86]

As far as method, try and see which one produces better results for you! I always check all speaker pairs that will be interacting so kind of do both of what you are talking about.

for measurements, eq needs spatial, time needs single point in space. You can’t time set time for more than a single spot, well you could set for multiple spots to have the best possible, but that means no spot is perfect and it would be a compromise. But that would be for multiple seats, not one seat. One seat one spot for time, but spatial around the head area for eq.

For example, if i do TA for Left Tweeter with Left Midrange. I will use single point in Left ear. Run RTA to see summing at that crossover point. Correct? Right speakers TA use right ear position?

Or all use mid headrest for check summing?

[Jdunk54nl]

For example, if i do TA for Left Tweeter with Left Midrange. I will use single point in Left ear. Run RTA to see summing at that crossover point. Correct? Right speakers TA use right ear position?

Or all use mid headrest for check summing?

all time needs to use same location, so middle or slightly left of middle is what I personally use. I always find if I use middle, everything is off to the left so if I place the mic basically where my left ear is, this fixed that issue. I believe it has to do with side window reflections causing extra energy on the left ear since it is close to that window and right ear is not.

[Kb86]

Golden advice. Thank you.

[Grinder]

What if any any factual basis might there be for the manufacturer to make the following statement?

.... "By placing subwoofers of this quality in enclosures not much larger than the shipping cartons they come in (as small as .2 cubic feet for the 8” and .45 cubic feet for the 10”) the effective resonance point is raised and the subwoofer performs as if it were in an enclosure many times its size." ....

https://www.cdtaudio.com/sep_compone.../qes820dvc.php

[Justin Zazzi]

What if any any factual basis might there be for the manufacturer to make the following statement?

.... "By placing subwoofers of this quality in enclosures not much larger than the shipping cartons they come in (as small as .2 cubic feet for the 8” and .45 cubic feet for the 10”) the effective resonance point is raised and the subwoofer performs as if it were in an enclosure many times its size." ....

https://www.cdtaudio.com/sep_compone.../qes820dvc.php

Half of that statement contradicts the other half.

The statement (and others like it on that page) could be more truthful if expanded slightly such as "... performs as if it were an older generation subwoofer in a much larger enclosure".

[Kb86]

https://youtu.be/flj5XmyrLyI

This is mosconi Cto explain how to use all pass filter.

i can not understand why at 15:00 he could find the exact frequency 3500hz to do 1st order apf. Could anyone explain for me pls?.

i only know how to see phase relate using RTA (skizer guide). Dont know how to measure phase.
my right midrange and right tweeter does not sum well at xover zone (2460hz), it does not complete cancellation but sum 0db gain. What does it indicate? What frequency should i attempt to try all pass filter? Thank you.

[Kb86]

My question abit confuse.
Here is simplified version:

Using RTA to verify phase and apply all pass filter:
- If there is a big dip when sum, it indicates that there is nearly 180 degree out of phase at that point. 2nd order could be apply at that point.

question:
If there is no big summing dip, but 0db gain at summing point, mean it is around 120 degree out of phase, correct?
1st order should be apply.
Question: how to find exact frequency to apply 1st order apf? using RTA only, as i dont know how to measure phase.

Thank you.