My Winter Project - Altec Build

[gdmoore28]

I've posted this same query at the Altec Users forum, but received no interest, so I'm hoping somebody here might have some experience in the direction I want to take with this build. Here we go.

Since I was a teenager I've wanted an Altec A7-based stereo system, but space has never allowed such monsters in my home. That is still the situation, but the dream lives on. I've decided to build my own Altec system with a footprint that will allow me to continue living with my wife in the same space. I've collected the following components so far:

- A Pair of 416-8Z woofers in near perfect condition, one of which has just returned from GPA for a complete recone.

- A pair of 511B horns - one of which is NOS brand new from the box, the other in storage since the 1960s

- One 802D driver (as new) and one 808-8A driver, unused and fresh from the factory box. Both of these will be refitted with new 8-ohm diaphragms from GPA.

The cabinets will be furniture-grade 7 cubic foot pieces with the usual over-bracing, yadda, yadda, designed from computer program and vented. Loosely based on the Altec Model 19. Narrow cabinet width will be compensated by greater height. They will be v-shaped to fit in the corner of the room.

Two questions:

- The horns will be mounted on top of the cabinets simply because I want them to be seen. Should I position the woofers at the top of the cabinets as well in order to keep them as close to the horn mouth as possible?

- My biggest concern is crossover design. I want to take advantage of the recent research done by a number of Altec enthusiasts to smooth the horn driver"s frequency response - especially in the 500 - 5000Hz range. My first inclination was to go with a version of the Zilch-designed Z19 crossover, but he favored changing the horn drivers to another brand. I recently ran across the Hiraga-designed network:
(http://web.archive.org/web/200502060...s/HiragaA5.pdf (http://web.archive.org/web/20050206015233/www.soundpractices.com/images/HiragaA5.pdf)). Complete background article at:http://wajonaudio.webs.com/Voice%20o...%20theatre.pdf (http://wajonaudio.webs.com/Voice%20of%20the%20theatre.pdf). Although Hiraga's crossover is specifically designed for use with the 288 drivers, it seems that the frequency response modifications are identical to those required for smoothing the 802 drivers.

(I'd like to advise in advance that I have no technical training in electronics, so my understanding of electronics is quite rudimental. I can build crossovers from diagrams, but beyond that I'm at loss.)

I'd appreciate any thoughts you guys have on this project, especially the crossover question. Thanks in advance for any help.

GeeDeeEmm

[quindecima]

When I did mine I duplicated the internal volume of the Model 19's instead of duplicating the cabinets ( a lot easier). I did two pair one with the 802-8g and 416-8b and the M19 cross. The other pair I did with the 515B;s and 902-8B's/511B changed to the A's with the N8500-8 cross. I liked the 515B pair a little better but they both were pretty awesome with just a 70W pair of tube monoblocks. If you want to see the horns look up the volume of the M19 and duplicate the bottom with a centered speaker the networks come up all the time on Ebay. Link. : Altec Speaker System (http://www.audioheritage.org/vbulletin/showthread.php?29592-Altec-Speaker-System&p=297118#post297118) WTS M19 components (http://www.audioheritage.org/vbulletin/showthread.php?18814-WTS-M19-components&p=190234#post190234)

[gdmoore28]

When I did mine I duplicated the internal volume of the Model 19's instead of duplicating the cabinets ( a lot easier). I did two pair one with the 802-8g and 416-8b and the M19 cross. The other pair I did with the 515B;s and 902-8B's/511B changed to the A's with the N8500-8 cross. I liked the 515B pair a little better but they both were pretty awesome with just a 70W pair of tube monoblocks. If you want to see the horns look up the volume of the M19 and duplicate the bottom with a centered speaker the networks come up all the time on Ebay. Link. : Altec Speaker System (http://www.audioheritage.org/vbulletin/showthread.php?29592-Altec-Speaker-System&p=297118#post297118) WTS M19 components (http://www.audioheritage.org/vbulletin/showthread.php?18814-WTS-M19-components&p=190234#post190234)

Love the car in your avatar!

Thanks so much for the input. The crossover design is my prime concern. The approach taken by Zilch (albeit with a different brand driver) and by Hiraga, especially, is to tame the Altec driver's renown mid frequency accentuation by designing a shelving network that will level the 500-5000 Hz output (by as much as 12dB attentuation!). I've heard these components (416/802/511b) using the stock Altec networks, and while they sound fine in a large auditorium, the midrange punch is just too much for a smaller room. I've considered simply biamping this system and using a digital RTA to smooth the output, but testimonials from some posters who have taken the RTA route report mixed results. Seems that more satisfactory results are obtained using a more traditional crossover network with the smoothing done there.

Thoughts?

GeeDeeEmm

[Earl K]

A reasonable starting point for your "custom network" would be to mate the LC values detailed in the N809-8A, to the mid-range suppression circuitry of the 30903/4 network .

http://www.audioheritage.org/photopost/data//500/N809-8A_Network.pnghttp://www.audioheritage.org/photopost/data//500/Altec_30904_30923_filter.jpg

I suspect that you can leave out the variable L-Pad ( ie; "RV1" ) detailed within the N809 schematic .

The Zobel components of 30904 ( consisting of C-2 & R-3 ) , should most likely use 18 uF & 7.5 ohm as values ( then they match the 1209-8A zobel values ) .

:)

PS; You'll need to accept that you are now making a custom network without having the necessary knowledge that could enable you to get it right " the first time" . You'll need to commit to employing some trial & error .

As such, you should order a UMIK-1 test mic for $75.00 (https://www.minidsp.com/products/acoustic-measurement/umik-1) , download REW ( Room EQ Wizard ) test software (http://www.roomeqwizard.com/)and then learn how to use them together ( then you can see changes in Frequency response that will happen when altering the LC values of the the suggested networks ) .

[Lee in Montreal]

Interesting project. Before building an expensive quality crossover, perhaps you could experiment in sound shaping with a digital crossover. Then when you are happy with the sound, design an analog equivalent. Or keep using the digital crossover ;-)

[Ed Kreamer]

New Years Greetings Gee Dee Emm,

In 1975 I built something similar except I used 2 416's ( in an 11 foot box, tuned to 25 Hz), 511b and the 802D driver. I used the stock N 501 crossover with the 30904 EQ, like what Earl K is recommending.( I had the good fortune to have the tutelage of the of the Altec commercial sound contractor.) I would recommend you use that circuit as it really tames the midrange and makes it a more accurate reproducer. Altec also used it on their 9846 Monitor speaker, as well as the Barcelona and Santiago

[Earl K]

Should you want to try a lower crossover point, here's the basic schematic ( though polarity of the horn might need to be flipped ) .

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

Flipped polarity would look like the following ;

http://classicaudio.ru/forum/uploads/monthly_05_2011/post-622-1385471289,743.jpg

You'll still need the mid-range suppression circuit. It would be wired in as in the following ;

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=47253

:)

[gdmoore28]

Wow, thanks so much Earl, Lee, and Ed for your valuable input. I'd completely forgotten about the Altec 30903/4 network, even though I have it in my collection of notes. Thanks especially to Earl for taking time not only to respond, but in furnishing the schematics. My copies are far less clear than yours. You guys don't know how much it means to me to get this valuable info.



Thanks again for making my day today. And a most happy new year to you all.

GeeDeeEmm

[Earl K]

Generally, Altecs 416 series of woofers are known to work best ( for extended LF ) within @ 9 cu' cabinets, tuned to @ 30hz .

Also, one wants to build with ( fairly ) closely matched woofers ( to avoid having to make custom crossovers for each side ) .

Since you have a recent recone from GPA, you might want to check it's DCR ( using a multi-meter ) and compare it to that of your unmolested 416-8Z.

Some of GPA's newer recones may represent be a departure from the older spec. of your 416-8Z.

Here's an example of a slightly changed spec; GPA's re-release of the Altec 416-8B . (http://www.greatplainsaudio.com/downloads/416-8B%20Spec%20Sheet.pdf)
- The changes indicated within the TS marameters of this spec sheet would have me not wanting to use "one-of-each" flavor ( but instead one type or the other ) .

:)

[Lee in Montreal]

I was at the Stax museum in Memphis in June. The recording room had a nice pair of A7 (Fame Studio in Muscle Shoals also had a very nice vintage set). But at Stax, the control room had a bigger version of the A7. Much bigger. Perhaps four or five times the volume. Most likely for cleaner bass. They were probably modified (enlarged) A5 cabinets. See picture below.

http://classicaudio.ru/forum/uploads/monthly_11_2013/post-109-1385472169,7543.jpg

Stax control room

http://img.photobucket.com/albums/v668/Lee_Vuong/Sebring%20Spec%20E30/DSC02612_zps0rdgorru.jpg



http://img.photobucket.com/albums/v668/Lee_Vuong/Sebring%20Spec%20E30/DSC02614_zps4vxzqkhs.jpg

http://img.photobucket.com/albums/v668/Lee_Vuong/Sebring%20Spec%20E30/DSC02613_zpsbohntkky.jpg

http://img.photobucket.com/albums/v668/Lee_Vuong/Sebring%20Spec%20E30/DSC02610_zpsgbv4qfs3.jpg

http://img.photobucket.com/albums/v668/Lee_Vuong/Sebring%20Spec%20E30/DSC02608_zpskqyq2xdl.jpg

http://img.photobucket.com/albums/v668/Lee_Vuong/Sebring%20Spec%20E30/DSC02609_zpslg63ziup.jpg

At Fame Studio in Muscle Shoals, Alabama

http://img.photobucket.com/albums/v668/Lee_Vuong/2015%20Mississippi/DSC03715_zpstt90xbyh.jpg

http://img.photobucket.com/albums/v668/Lee_Vuong/2015%20Mississippi/DSC03726_zpssu8daorw.jpg

http://img.photobucket.com/albums/v668/Lee_Vuong/2015%20Mississippi/DSC03707_zpszzlukjcg.jpg

[gdmoore28]

Great, interesting pictures, Lee. I've never seen anything like those huge Stax cabinets. (Does not mean much, I know.) Does anybody have any further knowledge about their origin? Obviously, whoever wrote the placard on them was not a tech head!

I wonder if the guys at Muscle Shoals had any idea what wonderful service they did themselves by decreasing the port volume on the blue cabs by stuffing the horns in there?

Another crossover question, if I may: Eminence offers a two-way crossover (500 or 800Hz) with 18dB attenuation for the horn, and 12dB attenuation on the woofer. (http://www.parts-express.com/eminence-pxb2-500-2-way-speaker-crossover-board-500-hz--290-630) I know that the extra measure of protection for the 802 drivers offered by the 18dB attenuation would be a good thing. Would there be any drawbacks to using this network followed by the Altec attenuation network on the high pass output? This is simply a what-if question. My inclination at this point is to follow Earl's suggestion to combine the 501 with the attenuation network, and just work from scratch rather than patch.

Last point, Earl - I checked the DCR on the two 416s and they were within .1 ohm of each other. Did I luck out?



GeeDeeEmm

[Earl K]

I wouldn't buy the Eminence networks . There's no telling how they will interact with your Altec components .

All-n-all, I believe you are best to buy ( via eBay ) a pair of N501-8a's ( if the lower x-over point is where you want to start ) or N801 or N809's ( for the higher 800hz point ) and then add the mid-range suppression circuitry ( 30903/4 ).

The two models seem to average $100.00 a piece ( judging from past sales ) . If they don't happen to work with your components they can at least be easily tossed back on the Bay to recapture most of your investment.

Making your own is slightly more affordable ( at around $80. to 90. ea ) using components from Parts Express .
- Also, ( fwiw ) the values I posted don't really come with a guaranteed certificate of provenance / though these questions of the accuracy of the LC values, could ( & should ) be researched .
- Here's one older thread that's quite interesting (http://www.audioheritage.org/vbulletin/showthread.php?25254-Help-on-Altec-N501-8b)
- And Another ! (http://www.hostboard.com/forums/f700/144452-n-501-8b-inductors.html)

:)

[Ed Kreamer]

Love the high end crossover Earl! thanks for the link.

[Earl K]

Love the high end crossover Earl! thanks for the link.


You're welcome Ed.

Here a look at Art J's Hi-end crossover ;

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=47259&d=1282790460

:)

[gdmoore28]

You're welcome Ed.

Here a look at Art J's Hi-end crossover ;

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=47259&d=1282790460

:)


Finally, a crossover schematic that even I can understand! And I think I have all those parts on hand already. I'm set now!

GeeDeeEmm

[srm51555]

I wouldn't buy the Eminence networks . There's no telling how they will interact with your Altec components .

All-n-all, I believe you are best to buy ( via eBay ) a pair of N501-8a's ( if the lower x-over point is where you want to start ) or N801 or N809's ( for the higher 800hz point ) and then add the mid-range suppression circuitry ( 30903/4 ).

The two models seem to average $100.00 a piece ( judging from past sales ) . If they don't happen to work with your components they can at least be easily tossed back on the Bay to recapture most of your investment.

Making your own is slightly more affordable ( at around $80. to 90. ea ) using components from Parts Express .
- Also, ( fwiw ) the values I posted don't really come with a guaranteed certificate of provenance / though these questions of the accuracy of the LC values, could ( & should ) be researched .
- Here's one older thread that's quite interesting (http://www.audioheritage.org/vbulletin/showthread.php?25254-Help-on-Altec-N501-8b)
- And Another ! (http://www.hostboard.com/forums/f700/144452-n-501-8b-inductors.html)

:)

+1 on building an 800hz variant with a mid range suppresser. I can't find the post, but I remember Mr. Widget posted a 500hz horn is really a 800-1000hz horn and 800hz is really a 1200hz horn. This is evident when looking at the model 19 crossover's 1200hz. I built a project similar to this about 13 years ago. Good luck

[Mr. Widget]

...but I remember Mr. Widget posted a 500hz horn is really a 800-1000hz horn and 800hz is really a 1200hz horn.Not exactly. What I've concluded from years of experimenting is that when you use a horn more conservatively they tend to sound less honky and horn like. The hard nasal quality that many dislike about horns is significantly reduced if you give yourself an additional octave or two between the horn's cut off frequency and your crossover choice.


Widget

[gdmoore28]

I've heard repeatedly that the 501B sounds much better crossed closer to 800Hz rather than the specified 500Hz. And it only makes sense that the lower frequencies have a pronounced tendency to cause "honking" or "ringing." Fortunately, it looks like the "N501-8B Preliminary" crossover w/midrange attenuation network that Earl posted for me crosses at approximately 580Hz, so that will move me almost 100Hz upward. I have some mounting options in mind that should help with any horn resonance, but considering the relatively low volume levels that this speaker will see (small room), I'm hoping that ringing will not be a problem. An old friend of mine, now passed on, used 501B/802D horns over University S6 bass horns crossed at 500Hz, and I never detected ringing in his system despite nice volume levels in a small room. But, having worked in ProSound for a number of years, I know very well that infamous Altec "honk" when used in auditoriums at mid/hi volume.

GeeDeeEmm

[hsosdrum]

You're welcome Ed.

Here a look at Art J's Hi-end crossover ;

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=47259&d=1282790460

:)

Let's give credit where credit's due: this illustration was originally created by Randall Munroe, of XKCD fame.

[gdmoore28]

I just realized that I've been referring to the 511B horn as a 501B. I've been doing some reading on other sites about restoring and using the Bose 901 speakers (my first honest to goodness quality speaker purchase in 1975), and somehow I mixed the -01 Bose numbers with the Altec -11. I have trouble remembering my own kid's/grandkid's names, so mixing numbers and names is quite routine for me. Sorry for the confusion!

GeeDeeEmm

[Altec Best]

[COLOR=#333333][FONT=Verdana]I've posted this same query at the Altec Users forum, but received no interest, so I'm hoping somebody here might have some experience in the direction I want to take with this build.

GeeDeeEmm[/I]


@Gdmoore, Its not that there was no interest it is because the board was experiencing technical difficulties which of late seems to be the norm.. :o: .Unfortunately ! People weren't able to post at all !:banghead:

I myself wasn't able to view the board for the past couple days.I spoke to the Admin. about it on the phone last night and today the board is back up. Sorry about that !

I think I have a couple spares lying around of the Altec 30904 if you need them ?

http://i653.photobucket.com/albums/uu255/Altec_Best/HPIM3065_zps2e7b0085.jpg~original

[gdmoore28]

@Gdmoore, Its not that there was no interest it is because the board was experiencing technical difficulties which of late seems to be the norm.. :o: .Unfortunately ! People weren't able to post at all !:banghead:

I myself wasn't able to view the board for the past couple days.I spoke to the Admin. about it on the phone last night and today the board is back up. Sorry about that !

I think I have a couple spares lying around of the Altec 30904 if you need them ?

http://i653.photobucket.com/albums/uu255/Altec_Best/HPIM3065_zps2e7b0085.jpg~original


Thanks so much. PM sent.

It dawned on me after I initially posted that there may be a problem with the server. This became evident when I was unable to log on, and even when I managed to access the board it would intermittently go blank and lock down. The same thing was happening on another board that I visit that apparently uses the same server. Nonetheless, folks have been extremely helpful and gone above and beyond to help and to recommend directions I should take. I am humbled and quite thankful to all.

GeeDeeEmm

[Altec Best]

Got it Thanks !

http://i653.photobucket.com/albums/uu255/Altec_Best/HPIM3066_1.jpg~original

[gdmoore28]

Just an update. Altec Best is selling me a couple of 30904 Attenuation/EQ networks. Thanks so much, AB! Today I made a visit to our local antique furniture dealer, and talked to the furniture refinisher about the build I'm working on. He was gracious to show me around the refinishing shop and gave me lots of tips on finishing these cabs with the antique look I want. Best of all, he's offered to sell me some gorgeous mahogany veneer that he has on hand. This veneer looks the way mahogany used to look, very dark and a deep shade of red. It will look beautiful once finished. The only thing that has me concerned is that this veneer is unbacked, raw veneer, and he does report some instances of having it becoming unattached in past repairs. He uses contact cement when veneering and has been doing this his whole life, so I'm in for some research on how to avoid the problems he's encountered. The veneer has been stored for many years in a climate-controlled building, lying flat with other lumber on top. I saw no defects in it at all. Any of you guys have experience in using unbacked veneers?

GeeDeeEmm

[GPM]

Lay out each piece of the veneer in the room it will be applied in long enough to acclimate them to the environment it will be applied in; ditto the plywood if not in the room where it's to be built.

Solvent or latex based contact cement? It must be solvent for un-backed. Also, does he screed it out with a proper veneer scraper and some serious arm pressure or.....? Rollers suck in comparison unless you're a brick mason or similar strength. Consider DIYing a vacuum bag system if veneering panels before assembly.

I've read many veneering [and even more coatings] horror stories on the net, but in nearly all of them folks either don't clean/prepare the surfaces properly and/or use the proper tools, chemicals, etc., i.e. not following the basics of properly doing any kind of finish work. Doesn't hurt to practice some first with cheap un-backed veneer either. ;)

GM

[Earl K]

<<<SNIP>>> Best of all, he's offered to sell me some gorgeous mahogany veneer that he has on hand. This veneer looks the way mahogany used to look, very dark and a deep shade of red. It will look beautiful once finished. The only thing that has me concerned is that this veneer is unbacked, raw veneer, and he does report some instances of having it becoming unattached in past repairs. He uses contact cement when veneering and has been doing this his whole life, so I'm in for some research on how to avoid the problems he's encountered.<<<<SNIP>>>

One can learn a whole lot at this forum ( as well as a couple of others ) by simply implementing the search word veneer ( for a complete LHF site search ) .

I've also seen mentioned that an almost foolproof attachment method appears to be the dried glue ( on both surfaces ) that is reactivated by the use of a hot iron over the veneer ( allowing for easy positioning of the veneer ) .

There has been ( over the last 13 years ) somewhat a bit of a consensus ( reached ) about the best way to veneer ( for both the newb & the even the most experienced ) .

I've also seen mentioned ( somewhere around here ) info on the pitfalls of using non-backed veneer .

If you want to review some of the stellar work of the many who have gone before you, then I'd recommend constructing an Excel spreadsheet ( that includes hot-links within cells for fast access ) to lead one back to interesting posts & threads.
A separate column for the authors is another idea.

:)

[gdmoore28]

The refinisher told me that he uses the dried glue/hot iron method on smaller repairs. I'm not sure what kind of contact cement he uses, but I saw a number of empty Deft cans lying round, so that's probably a clue. Having watched a few videos and read a few how-tos, I'm coming to the conclusion that GM has a good point here - warnings abound about practicing exacting surface prep proceedures, especially in the areas of cleanliness and glue coverage. One video I watched by a pro refinisher likewise stressed ditching the rollers and using only veneer application scrapers as the only sure fire way of assuring complete adhesion. Much more research to do. I've been doing cabinets and even some furniture since I was a teenager, but the only veneering I've done was for finishing end grains on plywood.

GeeDeeEmm