Altec Lansing

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#1,023
I was afraid of the foam and went old school. Bitumen and sand. No fun, but very effective.

The 515 always caught my fancy, but I can't say the 416 are a slouch. They went as high as I needed without breakup and allowed me to play down into the mid to low 30s. Can't complain. And FWIW, the 360L Onken is loaded with the 416.

The 805 should be fine. I had the big 803 horns and liked them, but the 1005s were better suited for Hi-Fi. My fav is still the 1505, if you can afford them. Cal has a pair of 1803s, but I've not heard them. Someday, eh Cal?
 
#1,024
"I then bought a case of Great Stuff 'gaps & cracks' foam filler when it was on sale at the local big box hardware store."

Use a flat paint stiring stick and massage a thin layer of the foam into the back side of the horn. This gives a base for the top layer to adhere to.

Run a 3/8" bead of foam on top of this, then run another 3/8" bead touching the first bead. Repeat until one surface is filled. The foam will expand to about a 2" thickness as it cures. Rotate the horn 90° and repeat. Repeat. Repeat.Trim excess cured foam with a steak knife.

This de-rings the horn and adds rigidity.

I have done this on large 30" x 20" midbass horns made from 5/16" FG, and the thin EV HP640 HF horns.

A shot of the horn stacks (front-side only, sorry).

http://i56.photobucket.com/albums/g196/dkleitsch/CoePA-2009.jpg
 
#1,026
OK, then all things considered, my choice would be the GPA 515B tuned to Fs if still available and within budget, otherwise their 515-8G tuned to Fs and for either, add an EQ'd [tapped] TL or simple sealed sub system with a 50-60 Hz/4th XO for any music with <42 Hz useful output such DSOTM, organ or similar.

Note that like most audio systems, some form of EQ is usually required to make it tonally flat, so considering the 2A3, it ideally needs built-in variable DF bass, treble tone controls.

GM
 
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#1,027
515-8G ?

GM said:
OK, then all things considered, my choice would be the GPA 515B tuned to Fs if still available and within budget, otherwise their 515-8G tuned to Fs and for either, add an EQ'd [tapped] TL or simple sealed sub system with a 50-60 Hz/4th XO for any music with <42 Hz useful output such DSOTM, organ or similar.

Note that like most audio systems, some form of EQ is usually required to make it tonally flat, so considering the 2A3, it ideally needs built-in variable DF bass, treble tone controls.

GM
Click to expand...

One thing I have never quite understood, about the 515-8G, is that it is labeled a bass horn driver (or some such similar expression) and yet, it is supposedly the Altec of choice, if one wants to get really high up into the mid range. It's spec sheet even lists usable response to 3,000Hz. What gives,
if you don't mind me asking ?
 
#1,028
The 'G' is a modern version of the original 515 bass horn driver that was/is optimized for the large 'A' series cinema reflex [mid]bass horns, which of course used the large multi-cell HF horns where each cell is primarily a HF horn and since there's such a large physical gap between the two, there's a need to fill in a goodly portion of the XO's overlapping BW for folks in the ~ first 1/3 of the audience and optimized as much as practical at the 2/3 screen/audience distance.

Ditto cinema, music/whatever stage mounted smaller horn systems in small venues as it's all just a matter of scale.

Another reason is that to keep XOs as simple as practical and knowing that textbook XOs required a ~flat response for several octaves on both sides of the XO point and that XO points had to be 'gapped' to help deal with the HF horn's acoustic offset, making ultra wide BW woofers with a benign, controlled roll-off was their only option.

GM
 
#1,029
Scott L said:
One thing I have never quite understood, about the 515-8G, is that it is labeled a bass horn driver (or some such similar expression) and yet, it is supposedly the Altec of choice, if one wants to get really high up into the mid range. It's spec sheet even lists usable response to 3,000Hz. What gives,

if you don't mind me asking ?
Click to expand...


Read more about 515 cs 416 here:
http://www.hostboard.com/forums/f700/112886-416s-vs-515s.html

This matches my experience: "I have auditioned many ~15" drivers over the decades and none matched the 515's clarity, so while the 416 series is more tonally balanced right out of the box due to its higher Qts, the 515 series can be EQ'd via some form of series R or using a current driven amp so that I can 'have my cake and eat it too', so to speak."
 
#1,030
Thanks to both GM and Croweproductions

Thanks to both of you for your very valued input. In view of my recent experiences with wild deviations in specs of the 416's I have, I will opt to go
with the 515-8G's if I decide to re-visit an "all out assault" build of a VOTT
as the large slice of midrange in my 4 way system.
 
#1,031
GM said:
The 'G' is a modern version of the original 515 bass horn driver that was/is optimized for the large 'A' series cinema reflex [mid]bass horns, which of course used the large multi-cell HF horns where each cell is primarily a HF horn and since there's such a large physical gap between the two, there's a need to fill in a goodly portion of the XO's overlapping BW for folks in the ~ first 1/3 of the audience and optimized as much as practical at the 2/3 screen/audience distance.

Ditto cinema, music/whatever stage mounted smaller horn systems in small venues as it's all just a matter of scale.

Another reason is that to keep XOs as simple as practical and knowing that textbook XOs required a ~flat response for several octaves on both sides of the XO point and that XO points had to be 'gapped' to help deal with the HF horn's acoustic offset, making ultra wide BW woofers with a benign, controlled roll-off was their only option.

GM
Click to expand...

Nice historical tid-bit on the 515, GM. Much appreciated!

Would I be completely nuts to run a 515 (16 ohms) in parallel with a 416 (16 ohms)? Separate boxes, of course. Since GPA uses the same cone, surround, and spider for both, I imagine they'd harmonize successfully.
 
#1,034
BTW, I didn't mean to stomp on Crowe's preference for the ONKEN over the Altec box, I understand what he means. For me it was a very tough choice. Ultimately I found the highly modified 828 more natural than the big Onken. But not the stock Altec box.

The 360L Onkens I knew and loved were made with an extremely dense, 25mm marine plywood (Nantex). And the double walled sides and thick baffle of the Onken give it a natural advantage or many boxes

The Altec bass box could be made of about anything, there were so many jobbed out. I was very lucky to get a pair made from high quality 3/4 ply, but even that needed bracing and doubling. In the pair we did in Paris, there was a lot of bracing and added thickness with 25mm Nantex. It became a different box. The "box talk" was gone, much like the Onken. Porting and controlling the flairs is also very important, as many people here can attest.

Both great boxes, and when built with the same materials should sound more alike that different.
 
#1,035
djk said:
You could do it in a .5 way system, roll the HF off on the 416, run the bass to both.
Click to expand...

That's pretty much what I was thinking. Although both drivers are connected in parallel, the 416 would have a tapped lowpass inductor of its own (and an adjustable inductor-shunt resistor). The degree of overlap between the drivers (and response shaping) can be adjusted for the room, and independently for the Left and Right channels.

There's also no point in having similar enclosures for the 416 and 515, since they have different T/S parameters and the lower driver (416) is much closer to the floor and is acoustically coupled to the floor image. The degree of LF "room lift" is very position-dependent and a reason for providing a range of mid and upper-bass adjustment between the two drivers.

Arrival times would be adjusted to be synchronous from the two drivers, which I think would address the perception of "blurry bass" that's commonly encountered in two-bass-driver loudspeakers.
 
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#1,036
Another reason is that to keep XOs as simple as practical and knowing that textbook XOs required a ~flat response for several octaves on both sides of the XO point and that XO points had to be 'gapped' to help deal with the HF horn's acoustic offset, making ultra wide BW woofers with a benign, controlled roll-off was their only option.

GM
Click to expand...

Too bad the Altec horns don't act like that. Many are not so great anywhere near at their rated LF cutoff!

Of course, if you factor in a gradual LP rolloff down to that specified f, you would be better off...but Altec themselves didn't do that.

And I am not so sure about the woofers either. 3kc from a 515?
 
#1,037
I might mock up a dual baffle on my onken to test this 515+416 theory. Best of both worlds, and 3db gain in efficiency. Do you think i could get away with a first order on the 416 at around the natural roll off at 300hz? Port blocking would need to be tested to effectively lower the tuning freq with the 2 drivers.
 
#1,038
Touching upon a myriad of design problems

Several concepts here; I have been trying to work these out as well:

"Blurry bass" (?) One can eliminate this possibility with a ppsl application.
The few times I have tried substituting a 416-8B in place of my ppsl Eminence Definimax, there was no comparison. The ppsl mopped up the floor against
the 416 with respect to dynamic impact. However, there was something to be said for the Altec "sustain" quality. By that I mean, on sustained bass notes
the Altec had a tonal quality that was quite nice. How to have both ?

Moving on to the 515-8G. I believe this unit would be indeed best served up
in a horn loaded configuration. But I do mean only for mid-bass use. I also believe that if you are going to use a compression driver/horn combination for
the pure midrange, the overall sound quality would mesh better with a horn loaded lower mid/upper bass. Cut from the same cloth, so to speak. Next, there's the consideration of where to cross, and what slope(?) The extended response of the 515-8G comes in mighty handy if one wants to follow the linear overlap rule, such that a (for instance) proper 18 db/butterworth can do it's job particularly near around the [probably] preferred 700ish Hz range that a compression driver/ horn combination would be comfortable with.

Descending down to the lows again, my question would be, are your 416-8B's all matched with respect to their T/S specs ? You would be lucky if you had a pair that matched ! Now, how many more times being lucky would it take to have a set of 4 drivers that all matched within a reasonable percentage ?

If you did, then the cat's meow would be a push-pull slot loaded beast using
a pair of 416's per enclosure, vented, of course. Crossed at somewhere in the 100-150Hz range depending upon how large of a VOTT type horn one could live with for the 515-8G.

It's my strong opinion, and personal listening experience that only with a large scale system like this could you be so emotionally involved and engaged with the music that there is no going back. To hear the original venue, including hall size/spatial clues is what allows this to happen.

Happy listening !
 
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