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Old 15th February 2013, 08:17 PM   #31
steve71 is offline steve71  Australia
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Originally Posted by j.michael droke View Post
Hi there S: The Altec A7 used a bass horn attached to the 15-inch driver with an 8-inch slot, and was produced to be used with either 800 or 500 cross 0ver to a compression loaded aluinum horn. The plans are available by googling-up Altec A7 VOT, look down the page aways for the dimension drawing. ...regards, Mchael...PS, I built one in 1960's.
I've contemplated the A7 before, but it's only a horn down to 200hz or so and then a bass reflex after that.
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Old 15th February 2013, 08:23 PM   #32
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Originally Posted by steve71 View Post
My ideas for these speakers are not set in stone. I would like to use a lot of what I have laying about, but apart from that I'm going to do what you guys suggest. If I question something, it's not because I think I'm right and you're wrong, I'm just trying to understand and learn.

I'm lucky enough to have a pretty big budget with this project, but that doesn't not automatically make me knowledgeable, or grantee a great out come.

I'm going to be building 6 or 7 of these speakers, so I want to get it right.
If I were planning to build a horn system for home theater use, it would be along the lines of DSL's Synergy type horn, allowing for a virtual single point source from multiple drivers, and constant uniform directivity from as low as 200 Hz on up.

The Synergy approach avoids the reflection problems of multiple separate horns, and could be done two, three, or four way, though I'd go two or three way with subwoofers. Even if you plan on 7 top speakers, you probably won't need more than 3 subs.

Construction would be far easier, overall size smaller, and sound would be coherent at any distance, unlike multiple stacked horns which need some distance to integrate.

As far as far as crossovers with two horns of vastly different path lengths, forget about using passive crossovers if you actually want to time align the two, not to mention that low crossover point passive crossover part expense can be more than DSP and amp cost.
If you don't want to go active all the way, the place to go passive would be between mid and high drivers.

Art
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Old 15th February 2013, 08:26 PM   #33
steve71 is offline steve71  Australia
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Originally Posted by Kindhornman View Post
The Altec A7 was the original Voice of the Theater and for its time was a good design. We have come a long way from just trying to reproduce a simple movie track from behind a screen. Yes they were good for what they were, we wouldn't have gotten where we are today without them. But I don't think you are going to see to many A7 enclosures with a single 311 horn on the top used for high end music reproduction these days. The low frequency output of the ported horn enclosure wasn't really a great design as the port output could not really keep up with the horn gain on the 15" bass speaker. That is why they also had the A2 with a much larger enclosure and two 15" speakers.

As for a folded horn going up to 200 hz that should be an easy thing to accomplish. A three way horn system with a cone driven mid-range is going to sound much more musical and the vocal range will be much better than you will get using the compression driver down that low. This is what we all remember as the horn sound, there wasn't much you could do to get rid of that shout from the horn in the lower frequency range. I'm not one for conic horns myself, but that is more of an individual thing. I don't think that in a home system that the so called constant directivity is really that much of an issue. I will stay with exponential or hyperbolic expansions myself.
I just went with a conical horn last time, due to ease of construction. Constant directivity is not a bad thing with though with my big space (28x38ft) that will have people sitting in various position for movies. But

I'm really liking the idea of a horn to cover 200-600hz, but my x-over only supports a three way design and I already have three drivers. I would have to make one of the x-overs passive if I added another horn.
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Old 15th February 2013, 08:41 PM   #34
steve71 is offline steve71  Australia
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Originally Posted by weltersys View Post
If I were planning to build a horn system for home theater use, it would be along the lines of DSL's Synergy type horn, allowing for a virtual single point source from multiple drivers, and constant uniform directivity from as low as 200 Hz on up.

The Synergy approach avoids the reflection problems of multiple separate horns, and could be done two, three, or four way, though I'd go two or three way with subwoofers. Even if you plan on 7 top speakers, you probably won't need more than 3 subs.

Construction would be far easier, overall size smaller, and sound would be coherent at any distance, unlike multiple stacked horns which need some distance to integrate.

As far as far as crossovers with two horns of vastly different path lengths, forget about using passive crossovers if you actually want to time align the two, not to mention that low crossover point passive crossover part expense can be more than DSP and amp cost.
If you don't want to go active all the way, the place to go passive would be between mid and high drivers.

Art
The Synergy horn solves a lot of problems and is a brilliant design, I agree. I've read a couple of builds, but didn't see anyone who had nailed the design - if you're aware of a build that I could copy that would be great. I just don't have the time or knowledge to blaze that trail.

I could go passive between the Gauss 1502 and the 288/1003. IIRC I'm crossing around 5Khz.
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Old 15th February 2013, 08:44 PM   #35
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Steve,
The real question is whether you really need to use horns on the bottom end. Yes they are punchy but unless they are really large you aren't going to get down into the lower octaves with them anyway. I have some double 18" bass horns that I sell to guys for PA use. They are rather large and to get down low it takes multiple units stacked. They will knock you on your behind but they are just too big for indoors if you are trying to get down to a fundamental of 20 to 30hz. Even a 75hz mouth cutoff size is rather large. I have smaller horns that I use for home use. I use a small horn with a 1" driver for the top end from about 1600 hz on up and a small horn with a 6 1/2" and a cutoff of about 600hz. Below that I use a direct radiator and that is real easy these days. Seven of those units in a room the size you are talking about would have an SPL level high enough to drive everyone screaming from the room. Look at my avatar and you will see those units with a third small horn that was used from 10Khz on up just cause I wanted better top end than I could get from even a 1" compression driver. I used TAD drivers and the sound was more than sweet. The bass was covered by a down firing 10" in those enclosures.

Steven
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Old 15th February 2013, 09:03 PM   #36
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Quote:
Originally Posted by steve71 View Post
I've contemplated the A7 before, but it's only a horn down to 200hz or so and then a bass reflex after that.
Hi there S: If the A7 dosen't grab you, how abou the pair of A4's for sale on the bay now (84-inches tall), and the price is right too. ....regards, Michael
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Old 15th February 2013, 09:28 PM   #37
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Originally Posted by steve71 View Post
The Synergy horn solves a lot of problems and is a brilliant design, I agree. I've read a couple of builds, but didn't see anyone who had nailed the design - if you're aware of a build that I could copy that would be great. I just don't have the time or knowledge to blaze that trail.
William has good information on his Unity horns here:
William Cowan's Homepage

I would think copying what he did would be far easier than the trail you would blaze using the multicells etc.

At any rate, by far the most difficult part is getting the crossover right, with DSP and some measuring that becomes much easier than the passive approach which has buried most of the Unity/Synergy builds- seemingly small changes in drivers require completely different passive crossover components to sum properly.
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Old 15th February 2013, 10:22 PM   #38
Pano is offline Pano  United States
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Originally Posted by steve71 View Post
I had always thought that I could cross lower since the 1003 was a 300hz horn and a was using a steep x-over slope and this was for home use.
1003 is a legit 300Hz horn. I have the 803 and the 1005 and they are not cheating. But just because the will play low, doesn't mean you should play low. Certainly the 288 doesn't work well that low without a steep crossover. Let your ears be the judge, if you can keep the driver out of distortion with a steep digital crossover and you like the sound of it, go for it. For me it worked better up high for a variety of reasons.
If you are using the 515 woofer, you have plenty of room to cross high, as they are very clean way on up. I use the 416-8A which is similar.

Quote:
Originally Posted by Kindhornman View Post
But I don't think you are going to see to many A7 enclosures with a single 311 horn on the top used for high end music reproduction these days.
I'm looking at a pair with 1005 horns on the top right now. I use it for high end music reproduction at home every day. Yes, it's been modified, but it's still quite recognizable. 416-8A woofers, 288-K mids on 1005 horns, Fane bullet tweeters. Everyone who has listened has been amazed, many were inspired. With a 1505 horn it is still my favorite speaker of all time.
Does it go as high as some? No.
Does it go as low as some? No
Does it have the crazy, tiny detail of some? No.
Does it sound more like real people playing real instruments and real voices than anything else I've heard? Yes!
And that's what important to me.
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Old 16th February 2013, 12:47 AM   #39
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Ok. Here's my experience.

The polar response of the multi-cells all looks the same... they are based on a truncated horn. That works because they are paralleled and acoustically coupled so they are able go down to the mouth size and expansion frequency. In the case of the 1003 they go legit to <300Hz. That is IF you have the proper driver.

The polar response looks like the response of a single section above some freq where the mutual coupling is working. This works out to be in the case of the 10 cell 1003 ten narrowing sources, somewhat like you would get with an array of 10 side by side drivers. Obviously at freqs closer to the LF cutoff it looks somewhat omindirectional.

I've either seen this or imagined it, but I think I have seen it.

I run 1003s or 203s all the way down. However in my experience almost *all* compression drivers are unhappy trying to do this. The WE555 is an exception, as it was designed to reach to 75Hz. So for the rest of you mere mortals, running this low may or may not be terribly successful. Most compression drivers are designed for max SPL and therefore a higher xover frequency.

These horns have been measured *flat* up to 14kHz. But that is ONLY on axis, per cell. Flat wide, up to 10kHz.

The problem is mating any horn with a tweeter or super tweeter, be it a horn or not. Physical position and phase don't work to advantage. Delay is called for, but it tends to mess up the sound of the main horn that one went to all the trouble to get.

The A7 is not a good speaker for home use, unless it is highly modified. Even then I needed to use a super high slope LP to keep the rise of the partial midrange horn from raising the response of the woofer to high above the bass freqs. They were designed for max SPL and intelligibility in PA/SR use before there were big SS amps, and high power voice coils, neo and big ferrite magnets, FEM modeling.

An advantage of the A7 is that the horn loaded bin puts the acoustic center *back* far enough to make it possible to line up with a 1003. The 1003 *must* be forward of flush front mounting for that to work. This is
important.

I wouldn't suggest anyone use an A7 at home without heavy, major mods.

I prefer to keep the maximum range possible in a *single* driver. Thus my use of 203s from <300Hz. to rolloff. I also like full range ESLs. Preserve the sonic character of the midrange and as wide as you can + & - seems to be the philosophy that works best for me.

Now here's heresy. In the form of free advice.

Imo, these multicells don't image worth a darn in their usual horizontal configuration. They do give coverage, which is what they were designed to do. Perhaps in a very *large* room, like a barn sized LR, or in a room with extremely absorptive walls, that being equivalent to being outside, they would image ok set up horizontally.

What I have done with real success, in normal size rooms, is to configure the multicells vertically! And I toe the horns so that the on axis angle is not straight ahead, but aimed slightly in front of the listening position. This will give excellent coverage at the listening area, from the width of the speakers inward. Best in the center, but it always is so.

If you have a low ceiling, you have to either put absorption for HF on it, or else (much simpler) roll off the upward firing cells at some frequency - somewhere between 3-7kHz is about right. Otherwise the image "sticks" upward. How to? Some cotton balls loosely placed down the throat does the trick. How many? Measure the freq response close in.

If you have a live hard floor, best put a rug or carpet down.

Works like a champ.

Almost anything else sounds dead and compressed by comparison.

Word to the wise, down in Oz, Steve71, seek yee Martin Seddon of Azura Horns! Wish I could go and say hello myself...
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Last edited by bear; 16th February 2013 at 12:50 AM.
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Old 16th February 2013, 04:04 PM   #40
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Originally Posted by Kindhornman View Post
The Altec A7 was the original Voice of the Theater and for its time was a good design.
Still good if you recognize it's faults ahead of time. There just something so nice about what that box does to a woofer. Any PA type woofer with a Qts of less than .5 just seems to shine. Magical box. Accurate? Hell no, but neither are some of those funny stories my Father used to tell.

The A7 wasn't exactly original. It came from the A5 ilk, possibly because it would be handy to mount the horn on top for that proud and majestic look or for a more compact system, turn the box over and put the horn inside. They lost the multicell and opted for the cast horn, again presumably because they travelled better and were easier to mount inside the box with that nice thick flange.
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