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Old 2nd November 2012, 02:11 PM   #221
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Quote:
Originally Posted by buzzforb View Post
GM,
Been looking at old Altec enclosure materials and saw a couple of options I would like your opinion on.

VOT Corner loaded home cabinet
210
9844
817

The 9844 has very similar Vas to what I modeled in unibox, shoeing about 3 cubic feet per 414. All these could work, but I dont know what to expect fomr the horn loaded versions. The tall 210 could be flipped and the hornincluded in the oen cavity. May be too tall for my listening enviroment.
I look forward to what your 414s spec as the range I have varies from as little as ~2 ft^3 to almost 8 ft^3/driver, though if driven with a ~matching impedance, the small cabs would increase to a similar size for a T/S max flat alignment.

IME with a mono DIY version of the 820 VOT using inexpensive drivers, horn and employing flipped, compression loaded corner 210s for decades, I can't recommend any parallel wall horns for HIFI unless the XO point is well below its eigenmodes BW and even then there's a slightly 'pinched' character to the critical mids due to throat distortion that over time negated some of the 'thrill' for me that such horns can generate.

Still, having had such designs for 4+ decades, I was initially bummed out at being forced into ‘only’ having my old subs you saw until I listened to them with the ~stock 511/802/500 Hz XO, immediately noticing how much more open they sounded; so for me, unless only flea power is available, these old PA expo horns are not an option for HIFI or high SQ HT apps.

With the advent of higher power/lower output impedance, Altec got it right with the circa ’59 832 corner cab, it just took a financial disaster for me to learn it. Once again proving that those who don’t learn from history are doomed to repeat it.

When Rod Stewart commissioned Altec to build him some monitors in the ‘70s, they chose the 832’s layout + super tweeters in a by then unfashionably large cab: Google

Also, as Ed implied, the acoustic center of an 817 or flipped 210 or just about any vertically oriented dual woofer/horn app is the excessively long acoustic ctc spacing, so in a small room and/or ~near-field app there will be audible vertical scaling of music, especially piano and singing where there’s a low male vocal. This can be alleviated somewhat by using electronics to ‘tilt’ the horn’s response to overlap at the LP, but like focusing an array, it affects other aspects of overall performance.

All that said, we all hear the same, yet not so much, so some folks will be ambivalent WRT any audible difference in an A-B comparison, hence I leave it to the reader to decide if they want to gamble with such horn speaker designs.

If only large horns will do, then at least slant one baffle like an 825/828 and preferably both.

GM
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Old 2nd November 2012, 02:28 PM   #222
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Originally Posted by buzzforb View Post
Here is interesting link to 414 performance, mainly highlighting its abilities up top in midbass area.

Don't know that I am taking advantage of the 288, although good extension does possibly allow for slower order xover. have read that most people encourage hig order crossovers, assuming this is for protection of compression driver.
You’re wasting both since the large format drivers are designed for 300-500 Hz XOs and the 414 for ~800-1600 Hz……….

True, but only if you use a large horn, so ctc spacing hampers using 1st order XOs. That said, some folk’s hearing is such that this isn’t an issue, so only one way to know for sure with each individual. Me, it reduces clarity/dynamics to that of a cheap, ‘FR’ driver trying to reproduce large orchestra or similar music.

As a general rule, there’s no such thing as too ‘fast’ an XO slope, but the tonal difference between a point source and horn is such that makes them impractical for HIFI/HT apps except between compression horns or at very low XO points.

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Old 2nd November 2012, 02:34 PM   #223
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NO horns is fine, just looking at what has been done. THanks for the comments. I will have the 414's next week and get them tested. Will also test 416 and le15a's I have.

Sucks, but that means waiting. I hate waiting. Foolish kid, I know.

Here is cad of the 290 with some alterations.
THe fillets are extended slightly to be a mirror or symmetrical image of the side walls. It may mean fancy wood work, but with all the talk about symmetry, I thought I wold give it a try.
The mounting bracket has also been contoured, i.e.poor mans cantenary to accommodate the exit angle of the 288. I also plan to try having the intersections of the side and top of the horn be a rounded so that when it all comes back to the entrance, it will mate well with the driver. Probably stupid when you considered he was using a hand plane to make his versions, but what the hell, this is DIY and I am ignorant.

I decided to go with 290 because the 480 is suggested to cross too high and seems a waste of the ability of the 288 drivers. If this is incorrect thinking, fire away.

I will have the other drawings soon. Kinda lost motivation when i found out the drivers and TS tester was not going to be here. I will work on getting measurement stuff up and running in eager anticipation.
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File Type: jpg 290.jpg (72.5 KB, 170 views)
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Old 2nd November 2012, 03:04 PM   #224
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you lost me completely

I know that you're going to have 4 x 414

same as 2 x some 15 JBL

are you already having - how many - 416x , and in which condition ?
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Old 2nd November 2012, 03:07 PM   #225
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Originally Posted by buzzforb View Post
I know. He said TQWT unless i am using low DF amp and can bring up the Qts with series R, then a MLTL can be used. Unfortunately, that is where the advice stopped.
I said this specific to the 414?

I know I’ve made a general rule statement to this effect, but it’s predicated on the assumption that a ‘small’ vented cab alignment required to have a low vent mach will need a long one, so might as well morph it into an inverse tapered TL or mass loaded one [TQWT or ML-TQWT to me]. The 414’s generally high Vas means this wouldn’t apply to the 414 or any Altec woofer IIRC.

Doesn’t mean the 414 won’t work well in these, just that there’s normally no need unless it’s an acoustically tiny cab tuned to Fs or below such as a Pi Align often is.

As I’ve repeatedly noted WRT old Altecs, the specs tend to vary too much to waste time speculating on what cab alignment to use unless it can be a very large one that has a lot of tuning flexibility. Otherwise, I’m waiting for measured specs of all drivers.

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Old 2nd November 2012, 03:19 PM   #226
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GM,
looking back, i think you made the above statement regarding the 2226h, whiich is out of play. My apologies.

What I have is:
4 - 414's
2- Jbl Le15a
1 - 416z in seemingly good condition. Will hook it up and listen.

If stupid WT3'tester had come, i could have something to start with, but no such luck.
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Old 2nd November 2012, 04:16 PM   #227
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Quote:
The fillets are extended slightly to be a mirror or symmetrical image of the side walls. It may mean fancy wood work, but with all the talk about symmetry, I thought I wold give it a try.
Please clarify: Are you referring to the fins inside the throat? I think of fillets as the concave transition (cove) between one surface into another...in this case the area between the horizontal and vertical surfaces in the horn.
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Old 2nd November 2012, 04:26 PM   #228
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The fins. Fillet is the wrong word.

The fins were centered on radial lines at 19 degree intervals. The outside curve is plotted from one of these radial line. With the outside radial line remaining, and the curve plotted over top of it, youhave part of the curve to the outside of that line and part of it to the inside. If you were to take the interior half and mirror it on the outside of the outer line, you would get a fin. This fin is very similar to what he has included in the drawings, being only slightly longer. I decided to keep this shape rather than use his simply because I liked the idea of symmetrical walls. It would seem that a wave passing along the two dissimilar shaped would be more problematic than that same wave passing across symmetrical walls. I look at it like the two main sides. What would happen to the response if one was different than the other? Completely uninformed opinion, BTW.
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Old 2nd November 2012, 05:42 PM   #229
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My reason for asking:

The fins appear to me to be straight. I think I understand the intent for this from a builder's perspective. However, the outermost fins enter into the throat region where the wavefront is still rapidly expanding and wrapping around a corner. I think more diffraction will be generated by their presence than any good they will do.

I question whether I would want fins at all...just thinkin' out loud...
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Old 2nd November 2012, 06:04 PM   #230
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While I have yet to post the side view of the horn, in the original, you are correct, the fins are limited to the straight section of the horn throat. Mine would extend to the point where the horns begin to open up. My description above pertained to the overhead view of the drawing. From this view, the only difference between mine and his is the length and shape, neither being drastically different. I am unsure of the fins as well. My prototype will be screwed together, so they can be removed. Both ways will be tested. I worked on the guides for the router today. I hope to shape the horns tomorrow.

Edit:
I wonder if the theory is that the wave will expand as it leaves throat, it shape is changing and will encounter the fins at the same time. If not, I agree with you that it would seem to do harm in that it would interact in an uneven way with the wavefront.
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Last edited by buzzforb; 2nd November 2012 at 06:07 PM.
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