[HAL]

Or you can use time delay in a DSP crossover to align drivers and sub cabinets to main speakers. 

I did this at LSAF2023 in the HAL room with the Magnetar II speakers and servo subs.  They were time aligned between the planars and servo subs and imaged very well.  Not so much with phase offset when they are located longer distances away.

If you go to any music venue with main and subs for live sound or reproduction, they use time delays to integrate the different speaker systems. 

[Hobbsmeerkat]

I think what Trader is trying to do is shift the internal baffle forward so that the voice coil of the woofer is at the center of the H-Frame subs, rather than the cone.

[HAL]

That is what I see and that changes the OB H-Frame response characteristics.  Does not sound like a good idea.

Easier to leave the H-Frame as designed and then adjust the time delay for alignment.  If the servo amp works as designed, then the phase delay filter is a linear phase filter design and changes the time offset.  How that works in the analog domain is unusual.

[NoahH]

This raises something weird I have wondered:

So many folks actually have their subs closer to their seating than the mains?

It has always seemed that the mains need the delay in most situations, not the subs, making the phase setting on the subs questionable.

[nlitworld]

This raises something weird I have wondered:

So many folks actually have their subs closer to their seating than the mains?

It has always seemed that the mains need the delay in most situations, not the subs, making the phase setting on the subs questionable.

While I do not have GR servo subs, I had this same issue where the mains needed delay compared to subs. I have my subs inputs are wired out of phase and use the phase adjustment as a from 180° backwards to 0 adjustment rather than a from 0° up to 180.

[TRADERXFAN]

Hey guys this is not about time delay to mains...

It is about the output response of the dipole itself, its shelving frequency and everything related to the depth of the baffle on an H frame ... I am just dropping it as I know what I need to know now...

The D distance shapes the frequency response due to cancellations.

[But for those trying to understand my point.. why not put the baffle on the front like a regular box and leave the back open?... because that would change how it works, right?
So that distance for the front wave and rear wave cancellation shapes the response output spl at specific frequencies... and thats why it think you want to try and get it even. It is about ms of time and symmetry. 
The 3 inch difference on the 7 inch "L" seems significant to me. But maybe hard to tell what it chnages wihtout outdoor measurements in a lot of areas]

Thanks folks

Tony

[mlundy57]

Tony,

As I understand it, there are two issues concerning the depth of the wells: 1) the deeper the wells, the lower the bass output will be, and 2) the deeper the wells, the lower the frequency will be where cabinet resonances begin.

Another way of looking at it is the higher the crossover point, the shallower the wells need to be.

f the depth of the wells are the same, the frequency where cabinet resonances begin, and therefore the highest possible crossover point, will be the same for both wells. If the depth of the wells are different, the deepest well will determine where cabinet resonances begin and will therefore dictate the highest crossover point.

[TRADERXFAN]

It is much more complex than that...
https://www.linkwitzlab.com/models.htm#A

If D  = 14"
There is a frequency where the dipole  is equal to a monopole... F =0.17*v/D = 163 hz
There is a frequency where the dipole has double the output to the monopole... f = 0.5*v/D = 80 hz
There is a null  to the sides when they are evenly spaced = 0 output...
And there is a predicted  resonance you want to stay out of range for the h-frame... F = 0.25*v/L =482 hz

Moving the driver/baffle forwards and backwards changes the shape because it changes where the backwave meets the front wave causing these doubling and cancellations... and different wavelengths relative to the total output...

So by shifting this up or back you would change the shape (see polar plots below, and how different freq have different shapes) of the response... not necessarily a bad thing...









But there is a shelving filter to offset the output dropoff 6db/octave [-assuming Brian of Rythmik designed that using the 14" original design]

If you want to boost the output on the low end... then use 24 inches D depth gives you...

There is a frequency where the dipole  is equal to a monopole... F =0.17*v/D = 95 hz
There is a frequency where the dipole has double the output to the monopole... f = 0.5*v/D = 46 hz
There is a null  to the sides when they are evenly spaced = 0 output...
And there is a predicted  resonance you want to stay out of range for the h-frame... 281hz

etc...

But the shelving filter wont match this design... so you have to re-equalize it or soemthing....

Actually just noticed linkwitz did show some math for how the response changes when it is moved forward... [note he points to the center of the driver for this]
https://www.linkwitzlab.com/frontiers.htm#L
There is a change more toward cardiod as you shift/asymmetry in the D length...
the nulls shift etc as well... I consider significant differences.  Different doesnt mean bad. If it sounds good it sounds good. Just trying to keep the H frame shape here, personally.

-Tony

[Tyson]

When the subs were originally developed, if memory serves, Danny tried out several variations to see how it would play out in the real world and the H-Frame with centered drivers gave the most even response and best sound quality.

[mlundy57]

You’ve eclipsed my over simplified understanding of the engineering involved.

[Danny Richie]

When the subs were originally developed, if memory serves, Danny tried out several variations to see how it would play out in the real world and the H-Frame with centered drivers gave the most even response and best sound quality.

Correct.

Another thing to keep in mind is that a 3" difference is offset is pretty menial when considering a 20 Hz note is 56 feet long and a 40Hz note is 28 feet long.

The other more significant problem in pushing the driver location to the front is that the U shaped baffle now has some really large panel areas on each side that sees a lot of pressure and requires a lot of bracing and or really thick sides to minimize coloration.