Digital time-correction of multiway dipole?

[Audiodidakt]

Hi

Is it possible to digital time-align a multiway dipole in both the front and back-direction?

I.e. if one time-align the speakers for the front output of the elements, will they then also be time-aligned for the back output?

(I presume the answer is no...)

Br Gisle

[natehansen66]

You presume right! At least to my way of thinking.......
John K has an excellent explanation here: Dipole-offset
Been a while since I read it, but if I remember right he considers the baffle to be the acoustic center. This is something I've been wondering about lately, as I have 4-way dipoles, with 3 drivers suspended 'naked', and the woofer in a shallow u-frame. When measuring and setting xo's and looking at phase alignment, having the drivers in line where the baffle would be does not result in time alignment, in the forward or backward planes. I can adjust the drivers offset on Z and get good alignment to the front, but the rear goes to hell..........

What's more important, good time/phase alignment to the front, or equal response front and rear?

[Rudolf]

I have tried to explain my view on the best time alignment here. Don't forget to follow that discussion down the page.

In general I would put emphasis on the direct response (front output), but try to keep the back output free from VERY deep notches.

Rudolf

[john k...]

Originally Posted by natehansen66

You presume right! At least to my way of thinking.......
John K has an excellent explanation here: Dipole-offset
Been a while since I read it, but if I remember right he considers the baffle to be the acoustic center. This is something I've been wondering about lately, as I have 4-way dipoles, with 3 drivers suspended 'naked', and the woofer in a shallow u-frame. When measuring and setting xo's and looking at phase alignment, having the drivers in line where the baffle would be does not result in time alignment, in the forward or backward planes. I can adjust the drivers offset on Z and get good alignment to the front, but the rear goes to hell..........

What's more important, good time/phase alignment to the front, or equal response front and rear?

I only used the baffle as a reference for the example. The point is that the only way to correctly align a dipole from both front and rear is by aligning the AC's of the sources. You can not do it by introducing delays. However, that assumes another issue. Namely that the AC for the front radiation of the source is at the same point as the rear. That may be true for ideal dipole sources, but it is not generally true.

[bzfcocon]

On thing that further complicates things is the front/back symmetry of the radiation of different drivers.
This will give you headaches in the crossover regardless how well ACs are physically aligned unless you use "true" dipole drivers (planars) and/or sufficient ways(probably 4 way at least), otherwise what will look like a very linear response in the front might be total mess in the back due to different roll-offs, etc.

I think in the end it's all about a reasonable compromise.

[Audiodidakt]

Thanks for all the answers!

I will try keep/obtain timecorrection through physical alignment

Br Gisle

[natehansen66]

Thanks for the link Rudolf, I had forgotten about that thread over there...........and now I need to revisit my driver spacing this weekend!

Audiodidakt - what's the configuration of your speakers, drivers, baffle, etc.....

[natehansen66]

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[Audiodidakt]

Currently I have no set-up; only spare parts... :-) Those are:

Mundorf AMT2510 (?) tweeter - will be hanging without baffel
Scan-Speak Illuminator 18 med - will be hanging without baffel
Precision Device PD15something - will be in baffel, probably in a cardioid-config.

I have AE TD15M comming in, taking the PD's place.

From about 125 Hz and below I am currently searching for the "best" option. It might be a solution with 4 woofers in a "multi-sub" config.

XO through MiniDSP

Br Gisle

[Breslaan]

Originally Posted by Audiodidakt

From about 125 Hz and below I am currently searching for the "best" option. It might be a solution with 4 woofers in a "multi-sub" config.

You can use pretty much any decent woofers down there. Wavecor has nice 10"s, 12" and up any modern low frequency dedicated PA woofer can be used e.g. BMS 12S330 for a 12" or PD.1550 for a 15" and many others if you don't plan to use AE's.