What To Do With 416-8Z Woofers

[dc270]

Anybody have box plans drawn up for these woofers. I know they came from Valencias, would be curious to know how high you can cross them over at. I got them for $200 hope I was not skunked!

I do have plans for an updated Model 19 design. Once I know the high end then I can better plan on what to do with them. I do not have any 511 horns to match them- hope I can use them higher than 500 hz if not them I'll just have to get creative......

Thanks for your thought here.
DC

[Old Guy]

800 is fine...I have seen 1200 but I would prefer 800 personally..your mileage may vary...

[GM]

1200 Hz/2nd order is about it, so the M19's XO is a good choice if its horn system and basic box dims are used, which is a good choice for near wall locations and tune the vents in-room for best blend.

By 'updated', so you mean Marty's single box version of it or.........?

GM

[dc270]

1200 Hz/2nd order is about it, so the M19's XO is a good choice if its horn system and basic box dims are used, which is a good choice for near wall locations and tune the vents in-room for best blend.

By 'updated', so you mean Marty's single box version of it or.........?

GM

Thanks for the reply so far- I have not found any specs on this driver to best guess the roll off characteristics so I was asking here. I knew what the specs were as Altec used them in their designs and was hoping I could stretch them out to 1.4~1.6k and use them in an "ecomowave" design. I have built the econowave design in 10" & 12" types with good success and now am wanting to push it into a 15" IF possible! Dinding that speacial driver horn combination in a waveguide design is my challenge.

I really like the sonics from the Altec woofer, as my Model 19's 416-B's really excell there. If this is possible in a wave guide I would like to possibly attempt it. The JBL LE 14 is a very good driver for a waveguide project, but I wanted something more mainstream in a near typical 15". If it is mot reasonable to wave guide a 15" them I am happy with a typical 811 horn & B&C DE250 config. Perhaps if I slope the driver with a 18 db/oct @ 1.4 it would fall into place.....

Thanks again for the suggestion/ reply
DC

[GM]

You're welcome!

Well, it has more BW, but it's all break-up modes scattered around the diaphragm/dust cap, so no way to match it except in average SPL on axis. It's fine for adding a bit of 'fill' through the XO BW, but it wouldn't be something I'd want to listen to with an XO this close to our most acute hearing BW centered around 2 kHz plus WGs typically need to be toe'd in and off axis response of a 15" this high up leaves a lot to be desired.

You can of course mate a WG to a 15", it just needs to be a lot larger than the 'Econowave' to go lower to match up off axis, so a good rule-of-thumb is its acoustic mouth area should match the driver's acoustic piston area and be at least 1 WL long at the XO point or ~ the physical mouth area and length of a 511 (imagine that ).

GM

[dc270]

I think I understand your acoustic physics explanation regarding the area and not so much the bandwidth. I have bever used the 511 lens, only the 811 briefly, but I am game for most anything. I honestly love the sound of these Alnico Altecs and would like to use/ compliment them in the best ways possible.

Thanks again GM
DC

[GM]

You're welcome!

I mean it has more HF extension out to around 3 kHz, it's just not high SQ enough for using a higher XO point regardless of how steep the slope is IMO if blending to a horn that's not acoustically large enough to cover all the way down to the driver's HF mass corner (2*Fs/Qts) if it's mounted on a flat baffle. As you begin folding the baffle up into a horn, then higher XO points with smaller horns become acceptable if the LF driver's break-up modes BW is fairly smooth, but for good performance at no time should the HF horn's physical mouth area be < the larger horn's throat area.

From this we see that for a 15" driver to blend well to an acoustically small 1.4 - 1.6 kHz horn requires a fairly high CR which in turn requires it to have a phase plug.

So, you can tax your patience and use the 'Econowave' as an HF throat adapter to DIY an acoustically large enough horn and add a matching wall angle short horn to control the directivity of the woofer's break-up modes BW (basically a ~4.25" deep round over with a 90 deg. inclusive initial wall angle for 1.6 kHz). Someone use to market heavy plastic ones, but don't recall who or whether they're still available.

Unfortunately, the horn's acoustic centers will be so far apart through the XO BW that a fairly long listening distance will be required for it to sound as one even if it's designed to tilt the horn's response down and why IMO such designs shouldn't be considered in a typical HIFI/HT app. I mean would you consider DIYing or buying a simple cone/dome box speaker with this high an XO point if its driver spacing was this far apart? I'm thinking not if for no other reason than it doesn't look 'right'.

GM

[dc270]

I understand what you are now saying about using a wave guide with this LF driver- it was educational-thank you!

OK let me move on to another thought. I like the sound of the 811 horn and there are a plethora of good drivers out there to use with them. Most seem to have the biggest pronlem with the last octave between 10~20khz. I am looking at the B&C De250 and the GPA 902 drivers to fit the 811 lens. Any other reccomendations or thoughts?

Thanks again
DC

[GM]

An Altec driver's top octave BW is all done by the time it reaches the driver/horn mounting interface, so the attached horn's vibrating air mass 'plug' will only damp it down (roll it off with increasing frequency) with attenuation increasing with increasing horn size and control the directivity of what's left, so all else equal, an 811 will have less HF roll off than a 511 and no doubt (at least to me) one reason why the early cinema horns were dumped in favor of a multi-cell that can only damp the individual HF horns at the mouth where their summed acoustic efficiency is high instead of being hammered down at a single throat. WE's various folded horns no doubt had some extra frictional losses, but I find it hard to believe it was significant enough to appreciably account for their ~flat BW jumping from ~5 kHz to the multi-cell's ~12 kHz, obviating the need for the former's tweeter horn.

Anyway, from this we see that installing a driver that doesn't have an appropriately matching terminus to the horn's throat geometry will in theory totally screw up its top octave reproduction if it's not already beaming like a laser when it enters the horn (not good), so without careful measurements of other brand drivers on the Altec horn of choice I can't recommend any but Altec.

Since the later 1" drivers beginning with the 802-8G were optimized for increased HF response at the expense of LF gain BW, I leave it to the individual to decide which way to go, though for Altec horns with > 1 kHz XOs, the later 1" drivers are the 'no-brainer' choice IMO.

GM

[dc270]

I got thee woofe/rs in and did some measurments on them with a WT3;

RE-7.127/ 6.838
FS- 22.21/ 25.57
QT- .288/ .291
QM- 4.763/ 4.835
QE- .3058/ .3105
LE 1.3/ 1.334
VAS- 33.3/ 34.53
MMS- 56.1/ 40.8

If rebuilt am I to assume that the "Q's" would be much closer to spec? As is looks now these would be better suited for a seal box design.

I plugged these numbers into Bass Box Pro and a sealed design around 3.63 cu/ft gets me close to .707, f3 is rather poor at 63 hz. Any thoughts here?

DC