Home Theater Forum and Systems banner

1 - 18 of 18 Posts

·
Registered
Joined
·
171 Posts
Discussion Starter #1
Has anybody tried to time aligning their drivers by offsetting them in a horizontal direction?
I read somwhere that this may result a better phase response at crossover frequency. No need to reverse polarity with tweeters and mids.
 

·
Registered
Joined
·
169 Posts
of course! Drivers should be better aligned!
You may do that in 3 ways:
1a: offsetting drivers by changing the shape of front panel,
1b: by tilting the speaker's front panel;
2: electronical way (like dynaudio) by using lattice LC networks.
 

·
Registered
Joined
·
171 Posts
Discussion Starter #3
Do you know how far a mid range driver should be recessed when crossed to a woofer at 300 Hz to be in phase and time aligned? I plan on building a u frame bass section with a mid/ high freq OB top section , all time aligned hopefully.
 

·
Registered
Joined
·
169 Posts
oh, it, simple. The idea is that the voice coils* of your drivers should be at the same distance from the listener.
_____________________________________
*better to use acoustical centers of drivers, but much easier to use the point where the coil fits to the diffusor. After that you make a crossover without time-shift correction.

The frequency does not matters here. But your filter does.

But if you know your Phase Shifts of x-over in degrees - it's very simple to count it in millimeters and use this number. You ll correct the distance from listener to your drivers according to the counted value. Use your Bass Driver as a zero point.
 

·
Registered
Joined
·
169 Posts
at the 300 hz wavelength is 1.13 meters. time of the 1 period (180 deg) is 0.00332 sec

Calculated at the sheet of paper for your frequency: approx. 6.2 mm (0.00001844 sec) per degree of your crossover phase shift at 300 Hz

but if you need the 180 deg. compensation - you should only invert polarity of MF driver.
 

·
Registered
Joined
·
169 Posts
Also, the important thing - is not to correct "ideal total-system phase". It's impossible. Time correction - is powerful instrument to minimize a time & phase shifts between drivers in your speaker system. You also could & should minimize the "group delay" parameter.
 

·
Registered
Joined
·
171 Posts
Discussion Starter #7
Thanks yad for those calculations. all I gotta do now is design a crossover roughly then find out somehow, how many degrees of phase shift result in mid driver section. Do you know any good sources for this kind of info. please?
 

·
Registered
Joined
·
169 Posts
OK. You may put the picture of your circuit here. I 'll help you with it. It will be an interesting example.
 

·
Registered
Joined
·
171 Posts
Discussion Starter #10
Wow Thanks for your willing enthusiasm. Alas I am nowhere near up to this yet. merely at stage of locating info i will need to use. I don't yet have all drivers. Will have to do some basic measurements before I even decide on definate xo frequencies.
reckon I won't start untill near Christmas.:sad:
 

·
Registered
Joined
·
169 Posts
May be you can tell models ? I could look for their specifications in my database.:blink:

What measurement tools or soft do you use ?
 

·
Registered
Joined
·
47 Posts
Without wanting appear naive and showing my ignorance in this subject
So let me try to fathom this
If sound travels at 750 miles an hour or 1100 meters per second how do you hear the relative distance of placement of the drivers?
Or is it too says that the orchestra is set up so that the instruments with the lowest pitch are relative in distance too the highest!
I am sure there must be a reason for time alignment
Would someone be so kind as to elaborate on this issue?
cheers speedie:coocoo:
 

·
Registered
Joined
·
704 Posts
Without wanting appear naive and showing my ignorance in this subject
So let me try to fathom this
If sound travels at 750 miles an hour or 1100 meters per second how do you hear the relative distance of placement of the drivers?
Or is it too says that the orchestra is set up so that the instruments with the lowest pitch are relative in distance too the highest!
I am sure there must be a reason for time alignment
Would someone be so kind as to elaborate on this issue?
cheers speedie:coocoo:
It has nothing to do with the speed of sound (all frequencies travel through air at the same speed) and everything to do with phase cancellations due to different wavelengths causing signal peaks to occur at different times at a given distance from the driver. Here's a good description.
 

·
Registered
Joined
·
47 Posts
Thanks for the link on time, distance, phase alignment it is a good read and as usual very concise
As was pointed out in some situations there is an audible difference and in others none
So do we have our ears trained well enough to discern what we are hearing or are we more absorbed with the music that we are listening too!
As is with all information it is only relative to the information going into the formulas that create the answer that is variable
I.e. distance from noise source, angle of perception, mood,
As a diyer I have limited access to most of the equipment that would have been used to undertake the research for the article so I must rely on what other individuals put up for science
Picture this we are going at 200mph we know it is fast but relative to what?
Thanks for your advice and guidance and I don’t mean to offend any one
Cheers speedie
 

·
Registered
Joined
·
171 Posts
Discussion Starter #17
Hi speedie
I have had ago at diy speakers previously, including cross over design (or lack of it). The speakers in question were not very intelligable with speach. I put this down to a terrible phase response between drivers. It was very noticable when compared to my VAF research center channel which i know has a straight and flat phase response.
 

·
Registered
Joined
·
47 Posts
Hay Jason haven’t heard back from any of the guys re alignment so can only guess that it is a moot point
When you first posted I thought that you where after advice on alignment of main speakers i.e. bookshelf or towers but it seems that maybe it was for your centre channel which is usually used for dialogue so i can see where it may? be critical (even though most of the centre speakers that i see are on the same plan with driver mounting)
Yad had put up a diagram for positioning of drivers but I think that it was for mains, also from that read in the post it was mentioned that positioning of drivers was not as critical as is phasing through crossover design and other criteria
I do hope that your endeavor to build your system goes well
Cheers speedie
:sn:
 
1 - 18 of 18 Posts
Top