816 advice please

[bowtie427ss]

if you put your hand on the cab, it feels like its going to expload.

That's "lost" energy that went into the speaker system as an electrical signal from the amplifier, but isn't exiting as sound pressure. This is where the 825/828 benefits significantly from sturdy internal bracing. What you're feeling with your hand is input power being lost in the form of kinetic energy and heat, in a perfect world you should be feeling that energy on your chest and pant legs 20 or 30 feet out in front.

Just my .02.........................

[GM]

Since both 828s and 816s share the same horn flares, but have different CSAs due to differing "flat" sides (parallel vs non), either one or both may not be "true" expos.

Still, it stands to reason that a radius could be exponential, depending on the radius' dimensions and the flare rate.

Right, over short distances it can be closely approximated with just a constant radius or even a series of straight sections, though working out the optimum bend points requires a bit more horn design knowledge, so the 825/828 are half size ~55 Hz exponential (flare factor ('T', aka 'M') = 1)/~110 Hz actual, IOW it's a section sliced out of a larger, longer expo horn. Since the 816 has the same throat area, axial length and side wall radius terminating into a smaller mouth it will have a T = < 1 or moving towards hyperbolic (T = 0.5), so we tend to call any flare between the two a hypex, then define it by its flare factor T (M).

I've never bothered to work out any of the parallel wall horn's flare factors or seen them published, so all I can say about the lot is that I highly recommend going to the extra effort of cloning an 825/828 horn for HIFI/HT apps due to its much smoother response, especially when wings are used, and adding its slanted bottom plate to the dual driver designs. Note that if wings are used in the home that bass traps are normally required behind them due to the cavity resonances that occur in a typical room.

GM

[whitebroncoii]

The early 515 and 416 are very similar and can be successfully used in direct-radiator cabs or horn cabs. The post-515E models of the 515 are specifically tailored for horn cabs. Very large motor and very light moving mass.

The 3156 is a direct-radiator woofer. Although this type of woofer can be installed in horn cabs and it handles lots of power, it can suffer from artifacts. There can be a distinct "coffee can" sound in some rooms. I would not run the crossover above 800Hz.

There are a dozen or more 816s loaded with 3156 woofers in the Lazy E arena (Guthrie, OK) and they seem to do all right in this large space.

[Audio_by_Goodwill]

forgot to add..my 816's are loaded with 418-8h mi speakers

That's a driver I don't hear much about..... what was it's position in the Altec Line-up.... or asked in another way, why did Altec need the 418, when it had the 421?

[LICORNE]

The A-6 could be a good choice. There's a theater up here ;1446 seats, with 5 A-6.
35mm and 70 mm projectors.

http://www.altecpro.com/pdfs/vintage...r%20System.pdf



Air conditioned projection booth, equipped with two 35 mm / 70 mm projectors (Century with laser reading system - reverse scanning) Avec
Size of projection screen
Height: 6.25 m (20' 6")
Width: 12.80 m (46' 0")

Installed with motorized winch on line set # 18
Speakers Altec A6 (5).
Surround speakers Bose 402 (24)
Amplification: Dolby sound system CP 200

[bfish]

...why did Altec need the 418, when it had the 421?

421s are best in LF apps, bass guitar, synth, etc. 418s are more of a full range, not as good in the 2nd octave as 421s, but better up higher. 421s were ferrite, 418s (and OEM 422s) were all AlNiCo. As long as you have the box for them, 418s will do everything a 417 does and then some.

[bfish]

... Thirdly, I suspect you felt there were fish to be caught, and time was wasting :-)

Bullseye! Only back then they wore skirts.

(Although there was some similarity if you didn't wash your hands...)

[kieran casey]

Many thanks for the response,
I'm hoping I can get 515s for the project and avoid having to fix the magnetic field by adding another magnet to the 3516s. Though I believe that this would actually improve their sound.
It turns out that my repairman actually visited GPA and met the folks there and talks very warmly about it all.
Kieran

[Audio_by_Goodwill]

421s are best in LF apps, bass guitar, synth, etc. 418s are more of a full range, not as good in the 2nd octave as 421s, but better up higher. 421s were ferrite, 418s (and OEM 422s) were all AlNiCo. As long as you have the box for them, 418s will do everything a 417 does and then some.

Ok, that makes sense....... does the 421 have a 12" analog?

[bfish]

Nope. The bottom end likes big.

There was a 15" OEM ~equal though, the 423.