Horn Alignment

[Charles Chance]

I've seen several discussions in the past concerning front-to-rear alignment of 511 horns/drivers, but I don't remember seeing any discussion of alignment of large format horns/drivers on A7 cabinet. It looks as though if I align voice coils, the large horns and sleds will be ready to topple off the top. Should I reverse polarity? Anybody have experience with this? I have no access to analysis equipment so I only hope to get close. Are there any rules-of-thumb, wives tales, or folklore that would help.

[Cal Weldon]

Hi Charles,

Is there a way you could mount the large horn to a platform of some kind and mount that to the cabinet, with it hanging over a bit? You would get your alignment but would that look OK to you? Why not mount it to a temporary platform and move it back and forth to see how much difference you notice and make your own judgement. If you look at my big system under the heading in this forum "Trying again for the link" you'll notice the coils from the upper woofers are not in line with the big woofers, but I'm not too worried about it because they are higher in the air and therefore further from my ear than the larger woofers so...does that mean that in fact they are in alignment or at least close to it?

As you said there is much discussion with ths topic.

Cheers
Cal

[djnagle]

Cal, I will be using a Rane active crossover in my biamped system. Can I aliegn the drivers electronically with the Rane?

[Cal Weldon]

Hi Igor,
Does your unit have a time delay circuit?
Cal

[thevott]

How long is a wavelength at 500 Hz?

[djnagle]

Here is the link to the same rane I have. I assume the time delay in the picture is what you are asking about.ebay sale

[Altec19]

Greetings All,

Here is an excellent site and article regarding phasing:

http://www.soundpractices.com/images/phase.pdf

Later . . .

[joyspring]

Hi all,

The Rane AC22 has an all-pass filter in the low pass section to provide up to 2mS of delay.

BTW, the Rane AC22/23 are EXCELLENT units

Calculating wavelength (a little high school physics):

Assuming speed of sound is 343.8 metres/sec (at sea level)...

wavelength = velocity (speed of sound)/frequency

= ( (metres/sec) / (cycles/sec) )

= (343.8 M/S) / 500hz

= 0.687 M (or 27 inches)

The Rane AC22's delay can easily compensate for the length of a 511.

BobR

BobR

[Cal Weldon]

I'm sorry but I can't see a time delay circuit on those buttons and I may be getting a bit over my head here. My experience with active crossovers is very limited.
In order the falsify the coil alignment don't you have to delay the sound to one of the drivers? In this case it would be the woofer as the tweeter is hanging out the back of it. The speed of sound at around 330 m/s means that at a difference of 5 cm the time delay should be 0.0001515/sec.
Am I in the right neighbourhood here?
Cal

[joyspring]

Charles,

If you're using a stock Altec crossover, aligning voice coils is a pretty good starting point. Move the HF section back-and-forth until you get so near a flat response at crossover as possible.

Nearly all Altec passive crossovers (N-500, N-800, etc.) are plain 2-pole Butterworth affairs and have two attributes that you ought to consider: (1) LF and HF outputs are 180 deg. out-of-phase, and (2) they will never sum flat (to a flat frequency response, that is). As I mentioned in a previous post, stock Altec passive crossovers were very primitive and pretty awful...

Igor has perhaps the best solution: bi-amplification using an active crossover with an LF delay. What's more, you may use a crossover with Linkwitz-Riley filters that have excellent phase and transient behaviour and that DO SUM FLAT. Try that with a single-pole or Bessel filter...

BobR