Altec Lansing ID? 802D, 803B

[Johnny_Law]

I stumbled across a pair of these today, and am not sure what to make of them. They are in DIY cabinets around 2 feet wide, 1.5 feet deep, and 3 feet tall. They sound great but a little thin ... not much body to the sound. (Of course, this is coming directly from listening to my L250s.) Then again I had to guess when re-wiring them - I didn't realize nothing was marked - and maybe I wired something backwards.

The compression drivers are 802D. The woofers are 803B. I am not sure which horns they are. The crossovers have no markings on them (just black boxes) and are mounted on boards on the back plate with two 3.7mH (I think 3.7, I should have taken a pic) inductors mounted one on each side.

Is this a particular kit? Is there any way I can identify the crossover? Would love any help. Ideally I will restore the crossover once I figure out what it is. I'd also like to see if I can find correct enclosures.

Here's a picture of the drivers:

https://imgur.com/ko1pLtIl.jpg

Thanks,
Ryan

[sguttag]

The horn is likely an 811, but could be a 511 (the difference is in the length/mouth size) to allow a lower crossover). These are the components of an A7. Altec marks their drivers of that vintage on the terminals themselves. Look on the tops of the input terminals and you'll see an engraved "1" and "2". "1" goes to the common terminal on an Altec crossover (like the N800D).

[gdmoore28]

The 511 horns measure 24" wide. If they are smaller than that they are 811s.

Looks like the cabs are approximately 7.5 cu. ft., so the size is OK. The question, of course, is whether the vent is appropriately sized. What do they measure?

If the 803s are working OK, the only thing that would make them sound "thin" (outside of the vent) is an incorrectly wired crossover or a horn imbalance.

It's impossible to say anything about the crossover (how about a pic?) because we don't know the inductor values or the wiring schematic on it. Maybe you could draw us a simple schematic of what you have. Do they look factory or home made?

All you need to get these running and sounding good is a two-way 12dB/octave, 800Hz crossover (very easy to build) with an Altec 30923 horn eq/attenuation network (again, very easy and cheap to build) topped off with an L-pad to set the driver balance. The L-pad is essential because the 802D horn drivers are waaaay more efficient than the 803 woofer and needs to be attenuated. The Altec 30923 eq circuit will dramatically cut the "in your face" midrange frequencies and move your combo much closer to hifi standards.

Let us know if you need more help. You have the potential of a nice sounding system.

GeeDeeEmm

[Johnny_Law]

Thanks so much. I'd love some more help figuring out the crossovers and deciding if it'd improve the sound to find some A7 cabinets. The horn is 18.5" wide, edge to edge from the back. Must be 811s. I can't find any markings on it. The cabinet vent is 2 1/4" tall x 13" wide.

(I reversed the horn connections - now they should be in phase with the woofers, and that midrange appears to have been thickened up.)

I took a bunch of pictures. The crossovers look DIY. Not sure what's in the black boxes. I can disassemble more to figure out how the 3.7mH inductors are wired. They do NOT have L-pads for tweeter control. I sure would like them ... the high frequencies are much more forward than the low. But my god these are sensitive. Normal listening levels hardly even tickle the MC7300's meters.

First, a better picture of the drivers and horn:

https://imgur.com/fbMW7jSl.jpg

https://imgur.com/6jfiojPl.jpg

https://imgur.com/xbPP8jhl.jpg

Here's the crossover (no there's no writing or anything on the top of the black box):

https://imgur.com/CyHhsPIl.jpg

https://imgur.com/PD2qJcyl.jpg

Here's my best guess at wiring:

https://imgur.com/Xn88sXFl.jpg

And here they are in my little listening space (faceless pre-amp is a McIntosh C32, amp is an MC7300; the Dynakit ST-70 and CJ MV-45 aren't connected):

https://imgur.com/rgNJL1rl.jpg

[Johnny_Law]

My plan is to see if I can dig into those black crossover boxes and see what's inside. Hopefully they aren't filled with tar. Knock on wood.

I'd love any thoughts on the benefits of A7 VOT cabinets for the woofers. Surely they must be better than these DIY cabs? And if I were to run the VOT cabs, should I keep the 511 horns or run 811s? Would love opinions here.

[Earl K]

My plan is to see if I can dig into those black crossover boxes and see what's inside. Hopefully they aren't filled with tar. Knock on wood.

I'd love any thoughts on the benefits of A7 VOT cabinets for the woofers. Surely they must be better than these DIY cabs? And if I were to run the VOT cabs, should I keep the 511 horns or run 811s? Would love opinions here.


Thoughts?

I think you may be confusing the massive size of the horn loaded A7 type enclosure with a ( wished for ) sensitivity increase of the bass frequencies.

The A7 horn only increases the midrange output resulting in an imbalance between bass frequencies and mid-range frequencies ( the horn gain is above 150hz ).

For home listening, stick with a straight-up bass reflex cabinet ( just like you have ).


:)

[Johnny_Law]

Thoughts?

I think you may be confusing the massive size of the horn loaded A7 type enclosure with a ( wished for ) sensitivity increase of the bass frequencies.

The A7 horn only increases the midrange output resulting in an imbalance between bass frequencies and mid-range frequencies ( the horn gain is above 150hz ).

For home listening, stick with a straight-up bass reflex cabinet ( just like you have ).


:)

Yes, I was hoping that the design of the A7 type enclosure might increase the sensitivity of the bass frequencies, and also was wondering whether it was designed to work with the woofer more effectively than the simple bass-reflex cabinet. I am a total ignoramus when it comes to cabinet design - I wasn't sure if the A7 horn-loaded enclosure would work better with the 803B's physical parameters, but I figured it might, since it was designed to work together in the VOT setup? If the A7 horn-loaded cabinet would or could result in a lower reach and a flatter curve, or any other improvements over the bass reflex cab, then I'd go looking for a pair!

But since the horn gain ("natural resonance"? like I said, ignoramus here) is over 150Hz, that doesn't seem to offer the improvement to accomplish the bass extension goal. However, could it accomplish the other goal, more ideally matching the woofer everywhere else? I suspect there must have been reasons to use that horn-loaded cabinet instead of simple bass-reflex cabs for the VOT system?

Thanks!

[Earl K]

GDM has a nice build thread over at AudioKarma for his speakers .

I suggest you read his Altec 606 Inspired Build Thread (http://audiokarma.org/forums/index.php?threads/altec-606-inspired-build-using-a-7-components.766911/) for some ideas.

Here's a pic that illustrates the mid-range gain achieved from the A7's horn.

http://www.audioheritage.org/photopost/data//500/medium/515g_828.jpg

A 416 or 803 will be similar to the above, though the boost will be a 1-2 db less .

:)

[Johnny_Law]

GDM has a nice build thread over at AudioKarma for his speakers .

I suggest you read his Altec 606 Inspired Build Thread (http://audiokarma.org/forums/index.php?threads/altec-606-inspired-build-using-a-7-components.766911/) for some ideas.

Here's a pic that illustrate the mid-range gain achieved from the A7's horn.

A 416 or 803 will be similar to the above, though the boost will be a 1-2 db less .

:)

Wow, thanks! Perfect. Will read.

[gdmoore28]

Thanks for the reference to my build thread, Earl!


Just as Earl said, you are in a much better position for bass response with your current (and very beautiful!) cabs than you would be with A7s - and the graph vividly shows why. Altec needed the A7-style cabs to take advantage of the increased low-midrange accentuation because of the intended use behind movie screens and as ProSound speakers. Great midrange means great projection and intelligibility. Bass response equivalent to what we expect today was not a priority then because there simply was not a lot of bass content in movie soundtracks or on most soundstages.

I hope we've dissuaded you from the A7 route. Yep, they look great and are highly impressive - but you have what you need.

Your vent size is just under 30 sq. inches in a 7.5 cu. ft. (roughly) cabinet. And, what do you know?, that is almost exactly the port size recommended for the 803A woofer. But your woofers are 803Bs. Altec recommends a 20 sq. inch vent for the 803B - if I'm reading their chart correctly. (And remember, these numbers are ball-park figures. Using one of the free on-line calculators will be a much better [read: essential] resource.)

http://www.lansingheritage.org/images/altec/plans/1960's-lf-design/page03.jpg

The crossover: I cannot tell what has been done there. The box is almost certainly factory of some sort (does it not have an L-pad control on it?), but the external inductors have me puzzled. Since we now know that you have 811B horns, your crossover needs to provide an 800Hz (minimum) 12dB/octave crossover. And I'm assuming that your 803B and 802Ds are still 16ohm impedance? A linkwitz/Riley design at that frequency and that impedance would require roughly 6mH inductors. I wonder if somebody has converted an 8 ohm crossover to accommodate 16 ohm drivers by augmenting the in-box inductors with the 3.7mH inductors? Of course, the caps would have required adjusting, too.

I'm just thinking out loud and probably way off base --- Help me, Earl!!!!!!

At this point we just have to know exactly what you have in that crossover. Once you've broken it open, give us a rough, hand-drawn schematic and we can go from there.

Oh, and I'll bet once you lower the volume of the horn, the bass response is going to jump. If that horn is running wide open, it's "masking" the bass response by coming up to volume long before the woofer does.

GeeDeeEmm

[Johnny_Law]

Gee Dee Em thank you! That chart is fantastic. Given the thickness of the wood and the internal sound deadening material, I think the internal volume is probably closer to or a little under 7 cubic feet. If I'm looking at the chart correctly, I am not even sure there's any possible port size for the 803B in that volume! It looks like the minimum volume for the 25Hz-resonant 803B is a hair over 8 cubic feet ... or I'm looking at it wrong?

Weekend project is pulling a crossover apart and asking it to reveal its secrets. In the meantime I've turned down the 1500Hz adjustment on my pre-amp and it's evened out a bit. But still, the 802Ds are much stronger than the 803Bs. I'm really looking forward to sorting it out and getting a potentiometer in here.

[gdmoore28]

Can't wait to see what you find with that crossover.

Even if you are at closer to 7 cu. ft. volume, the vent can be adjusted to work well with that cab. For example, my cabs are 6 cu. ft., and with a 14" wide X 1.5" tall X 3" deep vent, I ended up with a cab tuning of 37Hz and an F3 of 42Hz. I listen to pop/rock/jazz music and I can assure you that there is no lack solid bass response. Your slightly larger box will do even better. And it would be easy to bump them up to 8 cu. ft. by simply building some risers onto the bottom of them - which you will likely want to do, anyway. So good/good.

The key will be using one of the free online box design to get the vent right.

GeeDeeEmm

[Johnny_Law]

I'm suspecting the crossovers were a DIY N501-8A attempt (which seems odd if the horns are 811s, maybe a mistake by the DIY'er). The black box appears impenetrable ...

https://imgur.com/j4ceaojh.jpg

https://imgur.com/o14yaWch.jpg

Each has two 3.7MH inductors and an unmarked black box. The black box has screw terminals for the speaker inputs, inductors, and driver output. I am suspecting that the black box houses two 28uF capacitors, based on some N501-8A diagrams I've dug up (thanks Earl! (http://www.audioheritage.org/vbulletin/showthread.php?37735-My-Winter-Project-Altec-Build&p=385010&viewfull=1#post385010)):

http://images109.fotki.com/v779/photos/6/111916/12628482/AltecN5018a-vi.jpg

Two things might explain why the HF is so forward: (1) lack of a potentiometer and (2) the probable decay and ESR of the caps in the black box.

What's the path forward?

Option 1, stick with N501-8A crossovers since I already have the inductors, order four 28uF caps and a couple pots? The problem is, I don't know what pots are appropriate.

I found a post by Zilch recommending 16ohm pots: http://www.audioheritage.org/vbulletin/showthread.php?24116-Altec-Crossovers&p=243427&viewfull=1#post243427.

Option 2, ditch all this and find or build 800Hz crossovers to match the 811 horns ... like the N-800K (http://www.vallieur.de/Grafiken/Boxen/Scans/Altec%20N800-8K.jpg).

I guess first, if that black box is recognizable to anyone, how do I get inside it?

[Johnny_Law]

After spending the morning doing some more research, it appears that there are a variety of options for an 800Hz crossover.

I could take the Heathkit AS-101 (http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=58542&stc=1&d=1364842180) route, or a couple others (http://www.audioheritage.org/vbulletin/showthread.php?34269-Help-with-Heathkit-AS-101) like N809-8A or N-800K.

I could take the Zilch-endorsed N800-F route (http://www.audioheritage.org/vbulletin/showthread.php?24116-Altec-Crossovers/page2) (original equipment in Valencia 846a?).

However I have decided to build from scratch a pair of N800D networks since they are the original networks for the A7-800, in which the 811B / 802D / 803B were used according to this sheet (http://lansingheritage.org/images/altec/catalogs/1963-pro/page08.jpg).

The N800D schematic:

http://digilander.libero.it/steveviso/audiogarage/N800schema.jpg

However, instead of the various attenuated input terminals, I will replace them with an 8 ohm L-pad. So I will be placing an order from Parts Express for:

4 x 3mH air core inductors
4 x 10mF Audyn capacitors
4 x 0.47mF Audyn capacitors
2 x 15ohm non-inductive resistors
2 x 8ohm 50 watt L-Pads
2 x speaker terminals w/ 5-way binding posts

Looking forward to getting everything together and finally hearing what these are capable of! :bouncy:

[Johnny_Law]

Setback, the Parts-Express Dayton L-pads won't work. I thought it was a constant 8-ohms from pin 1 to pin 3, with pin 2 sweeping between them. If that were the case, I could connect pin 1 to my 15ohm resistor, pin 3 to my 2nd inductor / capacitor, and pin 2 to HF+. But that is NOT how these are wired. :banghead:

84685

I would love any suggestions as to a pot that WILL work?

EDIT: Or, anyone who runs an N800-D network with A7 components, which setting do you prefer? I could simply hardwire it with no adjustment for now.

[Earl K]

Why not use a 16 ohm variable Lpad for attenuation ?( for instance one from Parts Express found in the clickable picture link )
- Use in place of all fixed value resistors ( between crossover components and the 802 driver ).

https://www.parts-express.com/data/default/images/catalog/55/260-254_ALT_0.jpg (https://www.parts-express.com/speaker-l-pad-attenuator-50w-mono-3-8-shaft-16-ohm--260-254)

:)

BTW, the N800-D network only offers 4- or 5db maximum of horn attenuation > which typically isn't enough for home listening ( when mated with a 416 type woofer ).

One wants a network that offers more than that . Something like a max. of 8db or 10db of attenuation is more useful .

[Johnny_Law]

Why not use a 16 ohm variable Lpad for attenuation ?( for instance one from Parts Express found in the clickable picture link )
- Use in place of all fixed value resistors ( between crossover components and the 802 driver ).

https://www.parts-express.com/data/default/images/catalog/55/260-254_ALT_0.jpg (https://www.parts-express.com/speaker-l-pad-attenuator-50w-mono-3-8-shaft-16-ohm--260-254)

:)

BTW, the N800-D network only offers 4- or 5db maximum of horn attenuation > which typically isn't enough for home listening ( when mated with a 416 type woofer ).

One wants a network that offers more than that . Something like a max. of 8db or 10db of attenuation is more useful .

Thank you!

I guess I never took a moment to appreciate that the N800-D is simply a 2nd order Butterworth with HF attenuation. That being the case I suppose I could use the pots I got after all, in series with the 15 ohm resistors for extra attenuation. If the horn's still too hot I can always increase the attenuation.

Quick note, I think it's been covered before on here, but FYI running 2nd order Butterworth calculations on the N800D components (C1, C2 are 10.5uF; L1, L2 are 3mH) with these drivers (802D, 803B are both 16ohm drivers), we get an actual crossover around 900Hz with an almost 3dB spike (!):

https://speakerwizard.co.uk/calcs/Crossover_Calc_v2.php

84687

(Also, not that it matters, but another smoking gun that Altec intended these A7-800 components to be used with the N800D, page 12 of the 1954 catalog http://lansingheritage.org/images/altec/catalogs/1954-home/Page12.jpg and page 10 of the 1964 catalog: http://www.cieri.net/Documenti/Cataloghi/Altri%20marchi/Altec%20-%20Catalog%201964.pdf)

[Johnny_Law]

So here's how I'll incorporate the resistor and pot into the 2nd order Butterworth that is the N800D. Top is the network w/o attenuation, bottom is the network w/ the resistor and the pot wired in. (Obv the line I drew btw pins 2 and 3 of the pot isn't supposed to be there ...) This just might work after all.

Unless ... am I still misunderstanding the pot? Does the resistance designation on these refer to the impedance instead of the resistance across it? In other words, should I use a 16ohm pot here and not the 8ohm pot because the 802B is a 16ohm driver?

Edit: Yes this does appear to be how these things work. From PE (https://www.parts-express.com/parts-express-speaker-l-pad-attenuator-100w-mono-3-8-shaft-16-ohm--260-261), "L-pads adjust the relative volume of drivers connected to them by placing added resistance in series and parallel, keeping impedance at a constant 16 ohm load." Well, I will see if I can exchange my 8ohm ones for those 16ohm ones you linked to above Earl. Thanks again for steering me in the right direction.

... a quick thought, wouldn't I not want a constant 16 ohm load? The 802D like any driver will have non-constant impedance as a function of frequency ...

So just ignore R below and pretend that's the 16ohm pot, and ta-da, that's how I'll build these N800D clones.

84688

[Earl K]

When designing crossovers it's generally advisable to use ( create ) a constant impedance ( if at all possible ) .

The variable Lpad will give you that.

The older Altec diaphragms ( ie; 20275 type ) are actually more like 12 ohms, therefore I think you're better off keeping the 8 ohm Lpads and adding a 4 ohm resistor between the Cap/Coil arrangement and the variable Lpad ( like in your picture ).

:)

[Johnny_Law]

When designing crossovers it's generally advisable to use ( create ) a constant impedance ( if at all possible ) .

The variable Lpad will give you that.

The older Altec diaphragms ( ie; 20275 type ) are actually more like 12 ohms, therefore I think you're better off keeping the 8 ohm Lpads and adding a 4 ohm resistor between the Cap/Coil arrangement and the variable Lpad ( like in your picture ).

:)

Understood, thanks! :bouncy:

[Earl K]

Another ( so-called ) 800hz option is to use the N800F network ( it's quite applicable for those older components of yours ).

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=24113&stc=1&d=1175580320


The small 4uF cap used in the N800F provides quite a lot of midrange attenuation ( below say about 3.5K ) > cutting down the midrange "shout" of the horn/driver combo .

:)

[Johnny_Law]

Getting there.

85064

[Johnny_Law]

A few more wires ...

85074

Installing the pots in the terminal cups ...

85075

85076

Mounting to the back panel ...

85077

Move over, L200Bs ...

85078

[Johnny_Law]

WOW! They sound AMAZING! :bouncy: Detail, imaging, unreal. Bass is fantastic. SO happy with them! :applaud:

85072

(I wired them in phase w/ + going to "1" for both since they are mounted with the woofer flush with the horn per the following.)

85073

[Earl K]

Nice !

It's cool that you are finally enjoying these ( since you started this journey back in early 2918 ).

Good show on your persistence.


:)

[Johnny_Law]

Thanks so much for sticking with me the whole way through!