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Where to mount the horns


The Dude

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Hopefully Cask sees this as he seems to know quite a bit on time alignment. But while I wait for the rest of the parts to finish the projects I am starting to reconstruct my top hats. The idea came when I read some post on time alignment or physically aligning your drivers. So I thought I would pull the tweeter out, make a stand for it and align the driver with the mid driver. I have three pictures(disregard the tweeter in there as it will now be on top). But if you can see from one the Altec sticks out past the bass bin, in another the front of the Altec is flush with the front of the bass bin, and the last one is the P. Audio PH4525 that is flush with the bass bin. I didn't know if the stock K400 was back a little and if so should I do this with these horns(and how far back was it). I know there probably is some engineering involved on deciding which is best. But any good educated guess it out there.

Thanks

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I know there probably is some engineering involved on deciding which is best. But any good educated guess it out there.

It's been my experience that the most important drivers to align are the midrange and tweeter. If you listen with the horns pointed right at your listening position on centerline between the speakers, when you get the tweeter aligned on top of the midrange, you should experience a very large widening and deepening of the soundstage. I'd make sure that there aren't any close-by objects to your speaker (no closer than 2-3 feet) and your listening position, i.e., coffee table, etc. You might even tack up some tapestries or comforters on the side walls or place them over any equipment racks between the speakers if they are less than 3 feet away from the midrange horn mouths, then do the adjustments.

The starting point probably is the joint between the driver and the horn for both the tweeter and the midrange - that is what you can use to visually align as a starting point. If you adjust in 1/4 inch increments forward and backward on each speaker (left and right). It will just come into focus, and the timbre of the speaker will actually change a bit to sound more natural.

Once you find the sweet spot for the midrange vs. tweeter, you can position the combined units on top of your bass bins. This adjustment is about 10x less sensitive than the midrange-tweeter alignment. In fact if you align the joint between the midrange horn and driver with the dust cap on the bass bin woofers, you will probably be very close to being aligned, or moving the midrange forward very slightly. The timbre of the speakers for guitars and male voices will shift to a more natural sound.

I'd try to make the adjustments on stereo at the same time. If you run into problems, you can go with mono and one speaker, then transfer the alginments to the other speaker when you think that you have it algined, then listen in stereo.

Hope some of this helps.

Did I answer your question(s)?

Chris

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Yes that helps a lot, and answers my questions. I have just finished rebuilding the tophat on one to these specifications, I will finish the other and start listening. After that I will take some more pics of the setup to see if there is anything else I can do.

Thanks again for you help.

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Yes that helps a lot, and answers my questions. I have just finished rebuilding the tophat on one to these specifications, I will finish the other and start listening. After that I will take some more pics of the setup to see if there is anything else I can do.

Thanks again for you help.

Did you listen to one and make adjustments to get it dialed in?

This is one this that Chris and I actually agree on [;)], and it made a HUGE difference in the soundstage and clarity on my LaScalas.

Bruce

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Mechanical time-alignment is absolutely the way to go. Unlike cables, processors and the like, it's free too. If you could see a phase response plot before and after you'd be amazed especially since phase anomalies cannot be fixed by eq. Phase alignment (achieved through time alignment) is the most overlooked specification in all of audio.

As for your low end alignment, it gets a little more complicated as inference studies have shown that different frequencies emanate from different parts of the speaker cone. Since the cone is flared there is no absolute sweet spot unlike a compression driver. However, the HF tends towards the center so aligning to where the voice coil meets the dust cover is probably about correct since that's the frequency range in which the 2 drivers will be interacting.

Which I guess is a long winded way of saying "what cask05" said!

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I actually dug these up on the web as my rig is somewhere between here and the next show but I think they illustrate why what you're doing works so well.

First up is a non-time aligned LF to HF. Notice that although the frequency response is fairly flat according to the measurement mic (top trace) but the phase response has a huge shift where it literally wraps around 180 degrees (bottom trace). Can you hear that? You betcha and it don't sound good! And where is that shift? Looks about 1KHz to me, which is precisely the crossover point in this box.

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Here's the same system with electronic time alignment applied to the LF driver (which is course is the same thing as a mechanical time alignment in practice). Notice how the phase now tracks in a nice linear curve through the whole response curve? Not a perfect straight line but altogether much more pleasant to the ears.

Posted Image

Now at no time is the crossover set incorrectly it just cannot adress the phase response.

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I never knew what you meant when you talked about sound stage, until I looked it up. I all ways referred to this as how pronounced the music can be or the detail. I don't know if I have experienced enough great sound stage but after listening to fm for a while I thought to my self how better everything sounded. So I was going play some vinyl until I found out my table wires were coming apart at the rcas. So I started that project.. but at least I have a better system to listen to/

Thanks for your help, next we need to tackle some room treatments to deal with these plywood walls and open ceilings. Pictures to come tomorrow I am tired after 4-6 of using every tool in my garage to rebuild these top hats.

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