Best Use for 416A 806A 811B

[DIY John]

Recently, I purchased a pair of Altec home speakers containing the following components. All are 16 ohm and have date codes from 1969:
416A 15" woofers
H811B horns with
806A drivers
N-800-G Dividing Networks

The cabinets are similar to Flamenco or Valencia, at least in general size, but have no Altec markings. Curiously, while otherwise identical, one cabinet has no port and one has two 2.25 inch holes in the baffle board. Cabinets are in very poor condition and I feel not worth repair. So I have a clean slate...

Question 1: What would be the most optimum cabinet for these components?

I would like to construct new cabinets for these components and I really do not have the width available in my listening room (furniture-constrained!) to fit in copies of the original. I was thinking of something that would fit in the width of the horn, about 18." Depth and height constraints are not as much of a problem as the width.

Question 2: Do any of you have suggestions for a minimal width design? Has anyone done this before with a successful outcome? Any and all suggestions are welcome.

Thanks for the help!
John

[taudo]

DIY John,

1. GM is a veritable encyclopedia of knowledge about speaker design - and he's very willing to help those of us with lesser understanding. He won't lead you astray!

2. Here are a couple of thought that I've recently had, perhaps you'll find one or two worthwhile:

a. Consider building your tower as a three-way system, using the 416 as a midrange and using a good subwoofer for the low end extension. I used NOS JBL 2235's with good results, but there are a slew of other, better choices. See the thread "Subwoofers in 825/828 enclosures".

b. Consider using the 800 drivers with a smaller horn. Recently a really nice looking set of speakers were sold on ebay by jetboatbill. You can probably still find those pictures by searching completed auctions. They utilized 2 15" woofers and a horn much smaller than the 811B - although I don't know which it was. Such a design would easily lend itself to a _relatively_ small 3-way. (Well, smaller than 828 cabinets, anyway)

c. I was pretty impressed with the composite tractrix horns I bought from Stereo-Lab.de. See my post "Tractrix (or other) horns for Altec drivers". The 400 Hz horns I bought are round, with a mouth about 15-16 in diameter. They are made to mount Altec drivers. With the right components, it would be relatively easy to build an Avant-Garde Duo clone using Altec components. That's what I plan to do once I get my current projects finished!

HTH!

taudo

[DIY John]

taudo,

A lot of ideas, I will have to spend some time studying them...

GM,

I would like to hear some more about designs using just the components I have. As to my performance parameters, I'll give a little background. I have always wanted to try something with high efficiency so I can try a SET. I have not built the SET yet, so am still open as to what tube, but would probably like to stick with a 45 or 2A3. I could probably be talked into a 300B, but really don't want to go higher than that. I have numerous more powerful pp tube amps by Fisher, Scott, Eico, etc. but that really isn't the idea for this project. My listening is seated height, mostly Jazz with some larger scale classical. 99% of my listening is from LP. I do not have to listen terribly loud, and do not need to hear (feel) 32' organ pipes. I do want good transients and immediacy and connection to the music.

Placement is along a wall, but not in a corner. Max depth about 26-28" Height is relatively unlimited except for the horn height concerns. If the horn was built into the cabinet, seems like the cabinet could go higher, but maybe that would be too unwieldy or hard to brace the side panels.

I realize the horn might need to be separate, WAF yet to be determined on that one! No problem with a separate cabinet. It would make it easier to move around anyway. Don't really want to use digital delay, so set-back would be preferred. I understand that these horns need lots of damping on the outsides.

I think the 416A is the same as the 416Z, but may be different from the 416B. It is my understanding that the 416C is close, although it uses ceramic magnet. I have no T/S on this driver, although I have spent some small time looking. I was really hoping someone on this forum would know.

A tower design sounds interesting. Let me know if you need more info. If I am on a fool's errand you can tell me that also! Maybe someday I will have a bigger house. Thanks for considering this and giving your input.

John

[GM]

>Recently, I purchased a pair of Altec home speakers containing the following components. All are 16 ohm and have date codes from 1969:
416A 15" woofers
H811B horns with
806A drivers
N-800-G Dividing Networks
>The cabinets are similar to Flamenco or Valencia, at least in general size, but have no Altec markings. Curiously, while otherwise identical, one cabinet has no port and one has two 2.25 inch holes in the baffle board. Cabinets are in very poor condition and I feel not worth repair. So I have a clean slate...

====

Umm, DIY or two different Heathkit cabs perchance? Anyway, vented is preferred if no sub is used.

====

>Question 1: What would be the most optimum cabinet for these components?

I would like to construct new cabinets for these components and I really do not have the width available in my listening room (furniture-constrained!) to fit in copies of the original. I was thinking of something that would fit in the width of the horn, about 18." Depth and height constraints are not as much of a problem as the width.

====

Possibly a lot bigger than you probably can/will tolerate. Also, you need to define what performance parameters are most important to you. I mean some folks want peak efficiency enough to trade away considerable LF SQ/extension for it (i.e. front horn/sealed or vented back chamber) while others want all the BW they can eek out of it at the expense of efficiency (BIG cab/much reduced peak transient capability), etc..

Also, to get the proper HF horn physical set-back with a narrow cab when no digital delay is used requires that the horn sit on top, either exposed ala' A7 or in its own separate cab. The latter offers the highest SQ as you can fill it with something massive, such as kitty litter, sterilized sand, etc., to damp/stiffen/mass load it.

To get enough cab Vb though, a one fold design will probably be required to keep the horn close to the woofer and at an acceptable listening height, so depth may become excessive.

====

>Question 2: Do any of you have suggestions for a minimal width design? Has anyone done this before with a successful outcome? Any and all suggestions are welcome.

====

Yep, tower designs (now often referred to as ML-TLs or ML-TQWTs) have been my 'stock in trade' for several decades, though I haven't done any that I recall or have records on for the 416A though. I don't have specs for these and don't know if they are closer to the -16Z or the later -8A, so unless someone chimes in with some more detailed info on them I will have to assume a 'worst case' which may make it larger than optimum, so you will either have to do some experimentation once built or cobble together a prototype from scrap/cheap materials to find the optimum before committing to expensive wood, etc..

So what's your performance parameters, max allowable overall dims, speaker location (near a wall/corner/out in the room), preferred HF horn height, tube (SET or PP, really I need the actual output impedance (not tap rating) if you know it) or SS amp driven, digital EQ/TD going to be used?

Understand though that in speaker design you often can't have your 'cake and eat it too', so answering these will tell me which compromises are required and then you'll have to choose from them before I calc anything.

GM

[DIY John]

GM

So it looks like a folded tower design with external horn or separate horn cabinet. 32Hz Fb goal. Seated ear height 36-38" is about right. Horn a little above (would this be tilted down slightly?)

Sounds like you really don't like SETs much for this application! I would still like to try, since I have heard such good things about them, but know that I have a back up plan including more powerful pp tube. So it looks like I need the efficiency.

"Otherwise, horn loading the woofer to keep efficiency high in the ~250-800Hz is best, venting it out the back to get the most out of what little LF efficiency there is and hope the room pumps it up enough to at least be adequate."

It sound like we really need to nail down the parameters for these speakers better since there is such disparity between the two you have numbers for. I did a little more searching and came up with a reference to some numbers from Ashley in Nov 73. I am assuming this is Professor JR Ashley from the University of Colorado Boulder and the publication is probably JAES. Anyway he was quoted as having numbers for the 416A as follows:
Effective dia 12.7"
Vas cuft 36.8
fs 21.4
Re 12.5
Le 2.5
Bl 18.1
Qts 0.272

Don't know if this helps or not or if it tells you which of the set of numbers you have is similar.

John

[GM]

Greets!

As I noted, physical setback is problematic in a tower design unless it's folded, allowing the horn to be on the outside. Also, a horn-in-cab presents a sizable obstruction to efficient 1/4WL pipe action, especially in a very high aspect ratio one.

Most LPs are dead by 35Hz, though some symphony and current jazz offerings can have some output to ~30Hz, so I guess a ~32Hz Fb is one goal.

You don't mention seated ear height, so I'll assume the typical 36-38" unless you say otherwise. FWIW, some folks (me included) prefer the horn a little above, with the woofer at face height since typically a live venue has an elevated bandstand and you get a slightly more viseral presentation when cranked a bit.

A semi-realistic feeling playback requires considerable dynamic headroom to keep from clipping the fast transients in the 250-500Hz BW, so flea powered SET amps require really efficient systems, though many folks seem to like/prefer the soft clipping presentation of too little amp for the app. Different strokes..... For a reference, my system is ~100dB eff. in-room (dual corner loaded 515B/511/808) and it takes anywhere from ~110-225 SS watts to keep from clipping on classical and jazz recordings at a ~'live' 85dB SPL average sitting 14ft back in an open layout ~16ft x 27ft x 8ft room. This ~equates to ~27.5-56.25W of tube PP power, so less/more will ideally be required for a smaller/larger room.

Of course if you only listen at typical TV levels, then you might very well get by with a typical SET. Otherwise, horn loading the woofer to keep efficiency high in the ~250-800Hz is best, venting it out the back to get the most out of what little LF efficiency there is and hope the room pumps it up enough to at least be adequate.

Yeah, if you decide to do all the tweaks the 511/811 need for best performance, then you'll have quite the little project. At the very least, rigidly supporting them and damping the bells should be done IMO.

Using some measured 416-16Z specs, getting to ~32Hz requires ~4 ohms of total series R (amp/wiring/XO/external resistor) to flatten it out, reducing half space efficiency to ~92dB/m, though this is so room/personal preference dependent that it may be less. due to this driver's uncharacteristically low Vas, the cab only needs to be a relatively small 3ft^3 plus the driver(s), vent, bracing volume, so adding 10% should suffice, or ~3.3ft^3.

If I use the 416-8A specs, then this jumps to ~11.43ft^3/11.73ft^3, or ~ that of an 825 cab. No surprise there, though quite a big gap if you build to these specs, then wind up only needing ~3.3ft^3, or worse, needing the bigger cab and not having it, and why cobbling together a big prototype is a good plan IMO if you don't want to do a horn. That, or pick a size in between and tweak them and/or the rest of the system as required to get the best in-room performance you can.

So which way do you want to proceed?

GM

[GM]

Greets!

>GM

So it looks like a folded tower design with external horn or separate horn cabinet. 32Hz Fb goal. Seated ear height 36-38" is about right. Horn a little above (would this be tilted down slightly?)

====

Correct.

====

>Sounds like you really don't like SETs much for this application! I would still like to try, since I have heard such good things about them, but know that I have a back up plan including more powerful pp tube. So it looks like I need the efficiency.

====

Not per se, it just depends on the app. For instance, if you use a huge LF horn such as a 210/211, then a few watts is fine for all but the largest room of a HIFI app, but for even a combo horn/BR speaker like the A7 there just isn't enough power to cleanly reproduce all of the signal, so a typical SET should be BW limited to just driving the HF horn if the most accurate reproduction of the signal is desired, with a BW limited PP driving the LF.

All recordings are somewhat lacking in one way or another, so many folks (me included) add various types of distortion to make it sound more 'real'/pleasing to us. Wanting to have my 'cake and eat it too', I prefer to reproduce as much of the signal as I can and use both passive and digital EQ to further enhance it, which to my ears sounds better than the 'euphonic' distortion of a tube amp in near constant compressor mode.

Indeed, the two relatively high power DIY SETs I've auditioned sounded no different to me or the few others who were there than a good quality SS amp of ~equivalent power with impedance matching transformers, or even just some series resistance to ~mimic them on one that didn't have any, i.e. was ~transparent to the signal, with no SS 'harshness', so why bother with the extra hassle/cost of keeping a tube amp within spec?

====

>It sound like we really need to nail down the parameters for these speakers better since there is such disparity between the two you have numbers for. I did a little more searching and came up with a reference to some numbers from Ashley in Nov 73. I am assuming this is Professor JR Ashley from the University of Colorado Boulder and the publication is probably JAES. Anyway he was quoted as having numbers for the 416A as follows:
Effective dia 12.7"
Vas cuft 36.8
fs 21.4
Re 12.5
Le 2.5
Bl 18.1
Qts 0.272

Don't know if this helps or not or if it tells you which of the set of numbers you have is similar.

====

Like all of his specs I've compared to mine and others, these are whacked in various ways so all they tell me is that larger is better and if it turns out to be too big, then there's several easy enough ways to deal with it, but expanding a too small cab can be a real !@#$%^.

Anyway, I have a relatively simple LF horn design in mind (HF horn spaced up on top with adjustable rear bracket) that I've contemplated doing on numerous occasions for use in small rooms or an apt., but never got around to it and probably never will now, so give me some time to work up the details in a crude sketch since it's not one I can just plug the driver specs into one of my spreadsheets and out pops a design.

Basically, it's a rearranged 816 with a ~40% larger LF horn and more rear cab Vb (less than an 828's though, which is what I wanted), lowering its 1/4WL cutoff to ~174Hz from ~242Hz, but with the same flare rate/throat, figuring why mess with success since I'm not much into 'fixing' what ain't broke, especially since I'm under rather severe size constrainsts for the app. If you need more LF output, then there's still enough Vb to add a side firing sub (or two) later if there's no room for separate subs.

O.D. of the LF cab will be ~45.75"h x 18.5"w x 28"d, with the woofer centered at ~38", putting the HF horn up into the low to mid 50s" centered height depending on how close ya'll sit/tilt angle. FWIW, in case this sounds way too high, the woofer height is the same as my top one, and even though my HF horn is higher than your worst case position will be due to my cabs being taller overall and using a bigger horn, I still enjoy mine as close up as 8ft away, with their 'line of sight' down the throat crossing slightly above/behind my head in the front row 'sweet spot'. The downside is only one person wide at this close a position, for a wide soundstage you have to be at least 12ft away, and the ideal in my room is ~14ft.

If this works for ya'll, then all I need from you is some accurate measurements of your woofers: it's max o.d. and total depth when placed face down on a flat surface. If not, then I'll have to shrink the horn back to A7 size to maintain a semi-adequate rear Vb.

Oh yeah, will there be some open area around them to allow the vents to be at the bottom rear side corners so they can get additional loading from the wall/floor junction? A few inches each side will suffice.

GM

[DIY John]

GM

Sounds like it just might work, space-wise! On the vents at the corners, there is room to the sides in the rear, but firing out behind tall entertainment center and other shorter furniture. As to the 28" depth, that puts me right at the wall, but suppose it could be pulled out a couple more inches if necessary. Does this give more bass gain than aiming the port into the room?

Another thing. I'm not really going to be able to toe in these cabinets with the dimensions we are talking about. Is it possible or desirable to toe-in the hf horns only and still get a good result?

Woofer frame maximum OD is 15.25" depth including dust cap (but excluding dust cap screw heads) amd cork gasket is 7" These are pretty accurate, especially the OD.

Looking forward to seeing what you come up with!

John

[GM]

Greets!

>GM

Sounds like it just might work, space-wise! On the vents at the corners, there is room to the sides in the rear, but firing out behind tall entertainment center and other shorter furniture.

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Not a problem, we're dealing with very large WLs.

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>As to the 28" depth, that puts me right at the wall, but suppose it could be pulled out a couple more inches if necessary. Does this give more bass gain than aiming the port into the room?

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I want them against the wall. Yes, though due to the size of the WLs, the difference is only audible in the vent's upper BW, adding a little more gain to the midbass.

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>Another thing. I'm not really going to be able to toe in these cabinets with the dimensions we are talking about. Is it possible or desirable to toe-in the hf horns only and still get a good result?

====

I figured as much because of the excessively narrow width limitation.

The HF beams worse of course, so you'll probably have to toe them in some and another reason for just leaving them exposed ala' an A7. Other means can be used to damp them, or not, as most folks like their Altec 'sound', though I admit I don't know how anybody can tolerate their ringing bells. It makes my teeth hurt, so I recommend at least experimenting with damping them.

I meant to bring this up yesterday, but forgot in my haste to post since I'm so busy right now. This will be a major issue if you sit close enough that you can't line of sight see all of their throats from the opposite seating position due to a 19.25" horn depth, 16" wide parallel sides, and an XO point well above the horn's mouth width (~270Hz), so I guess I need you to either do a bit of physical experimenting or measuring/calcing to see if this will be an issue.

If so, then the woodworking just got harder since the design will have to be angled to whatever degree you conclude, and even more rear chamber VB will be lost. That, or reduce the horn depth until you can, which may make it too short to be worth the extra effort. I guess you could even cut a rounded off notch in the horn's sidewall, but never having tried it, I don't know for sure what all the audible/subjective difference it would make, but for sure it will negate some of the extra gain over the 816 horn.

Yet another possible option is lowering the XO point since this isn't a prosound app, especially if you go with flea power. The 811 is gone by ~351Hz, or just slightly above the standard Altec single driver LF throat's cutoff, so theoretically the woofer can be XO'd 2nd or 3rd order at ~400Hz, with the horn just ist or 2nd order, negating much of the LF horn's toe-in and mouth eigenmode (standing wave) issues. This normally requires an R/C network to flatten the HF response, i.e just another means of shelving, but with the side benefit of a flatter response over a wider BW than with just the standard shelving network.

Heck, some folks don't even bother to use an XO, just shelve the HF as required, since all the 416/515 series woofers are so smooth out to the limits of their BW, ditto the bandpass nature of the HF horns, but of course this isn't a viable option in your current app.

Frankly, if you can find two more OEM 416As for dual driver cabs you'll have right at the same efficiency over a much wider BW than a single driver in a truncated 1/2 size horn, and if done in an MTM layout, better on axis summing/controlled off axis response. This would also allow a simple straight pipe design with the HF horn in it and only the baffle need be angled. Doesn't look as cool as a front loaded horn though.

Done this way, there's another option, and that's to use a tall, large diameter tube cut in half with a baffle added. Now you can toe it in to suit in the same space.

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>Woofer frame maximum OD is 15.25" depth including dust cap (but excluding dust cap screw heads) amd cork gasket is 7" These are pretty accurate, especially the OD.

====

OK, this jives with my dims.

Anyway, let me know about the toe-in issue and give me your email addy so I can send the sketches once done, hopefully within the week.

GM

[DIY John]

GM,

OK, reality check time. I reread your post-before-last about listening distances and realize that I did not pay enough attention at the time. In my relatively constrained and well below-optimum listening room, the furthest listening position is 8 ft from the centerline between speakers, with them approx 6 ft between their inside edges. This sounds close compared to the numbers you were talking about. In addition, the sweet spot is occupied by a lamp! This is a real world living situation in a multi-use room and I can't see it changing, unfortunately. I realize this inovlves lots of compromises to the audio, but does it kill our theoretical project entirely?

As to seeing down the throats of the bass horns at 16" wide parallel and 19.25" deep, the near-center listener could see part of the throat of each, if faced forward. So maybe go with the bandwith limit to 400 Hz on the woofer unless we are totally dead. And is the 811B horn really going to cover that octave between 400 and 800? What about the HF horn dispersion? Would it be able to cover such close-up and widely arranged listening positions? I realize that stereo imaging would be greatly reduced. Would the HF horn disperse better or worse turned in the vertical arrangement?

As to acquiring another pair of 416A, I can't see that happening right now.

I am wonder what the eventual efficiency might be of the bass cabinet designed in this way.

Thanks,
John