Powerglide Posted December 29, 2020 Posted December 29, 2020 A few months back a friend asked if I could help in restoring a pair of A7’s back to their former glory. A previous owner had decided to strip back the original paint with the intention of clear coating the plywood boxes. He gave it a good go sanding completely back to raw ply but realised the construction methods, although strong, were never going to look that pretty without some extensive veneer work. Unfortunately the project was abandoned and the raw boxes were left exposed to the elements for some years. I don’t have any pics on how they looked pre start, the horn flares were varnished but the rest of the cabinets were rough as a bears arse and we disagreed on the best way to proceed (a box of matches was a suggested option) reluctantly I agreed to patch them up for paint. After a kilo of resin, sanding, filling, blocking, filling, swearing, blocking, they started to sharpen up but there were issues with areas of the ply being drummy. I think heavy sanding of the outer ply layer, the possible use of a chemical stripper and a lengthy period exposed to moisture had caused areas of the plywood bond to fail. After all my filling work I was quite savage digging off the loose ply and reglueing where I could, more filler........ Made a few upgrades to the internals first of all reinforcing the horn flares with a foaming glue that seeps into the joints then expands forming a kind of weld in the corners. I glued and screwed some plywood covers on the rear and back filled the cavities with expanding foam. I made ply stiffening panels for all the internal faces with 35 x 35 Baltic pine battens, glued and screwed from the rear then glued and screwed to the internals. The rear removable panels were in OK shape but we replaced the timber screws with nutserts and countersunk M6 bolts The port panels were replaced to the correct aperture and I moved them back into the enclosure for a neater look when used without the grilles. We applied a two pack high build undercoat to the raw ply which exposed more flaws...... more filler, more sanding, more undercoat, more sanding. Finally ready for a top coat in a two pack Matt matching the original grey. Before we began I was lucky enough to get a listen with some of the components that are going to be used and they definitely had the minerals. Eagerly awaiting an audition with the proper crossovers and a decent amp. I’m sure the owner will carry on this thread once the drivers are installed and he gets the grilles and decals sorted. Should end up something like this 12 2
simo8989 Posted December 29, 2020 Posted December 29, 2020 @missmurphy@tygersmoke hey Phil and Gary, these were Phil's old cabinets fully restored by Powerglide for a good mate of mine, which I didn't have time to restore. They are being fitted with a pair of Higara's Crossovers today made by another good mate. 4 1 1
simo8989 Posted December 29, 2020 Posted December 29, 2020 Hi Powerglide, great to see these fully restored (better than when they were new) another fantastic job by you, love your work. 1
simo8989 Posted December 29, 2020 Posted December 29, 2020 Here's a couple of photos of the A7 cabinets before the restoration. 2
cccrchairman Posted December 29, 2020 Posted December 29, 2020 Congratulations Alan on another fine restoration project and a great post. Good to see another pair of Altecs getting some attention from an experienced craftsman. 3
Mr_Fried Posted December 29, 2020 Posted December 29, 2020 (edited) A massive thanks to Alan for an amazing restoration. These cabinets being original Altec 825's, they were well worth saving. Getting them up into my livingroom was certainly a struggle. There are so many friends and fellow Altec (and begrudginly JBL) enthusiasts from the Sydney area who have helped me out over the past year or so with this project and before I go any further, I just want to say a huge heartfelt thank you for helping to make this childhood dream come true. The hours of conversation, debate, enjoying fine coffee, learning together and helping to man-handle massive speaker systems has been some of the best time spent in recent memory. You guys know who you are and you are all legends. I really must dedicate this however to my dads best mate Brad Sheargold, who is no longer with us. Brad was a big time Altec guy and growing up, I have fond memories going around to his place with Dad and getting literally blown away by his A7 system. Brad was a guy with a point of view and in his favour, it was almost always correct, even if it did take you a while to figure out and catch up. We miss all the angry letters to Electronics Australia and Silicon Chip with corrections and feedback. And we miss the music. This one is for you Brad The plan is to recreate the system that John Scronczer wrote about in La Voice of the Theater Chez Nous https://wajonaudio.webs.com/Voice of the theatre.pdf I have closely followed the best practices in the Jim Dickinson Small Classic VOTT whitepaper: http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=76713&d=1493150408 And will be using the following components: Altec 515B original condition LF drivers Altec 291-16C HF driver, fitted with 16ohm aluminium GPA diaphragms. Very early Altec 1505 Multicell horns Jean Hiraga A5 crossover networks A challenge of any full range speaker system is flat response across the frequency range. The A5/A7 cabinet is designed for thunderous midbass performance and amazing transient response. To this end I have a rather powerful pair of subwoofers from our friend @Aslan, running P.Audio TM12's in beautiful strip-laminated cabinets to take the load off the mains. Tying this all together is a MiniDSP 2x4 HD, soon to be upgraded to a MiniDSP SHD, which acts as the DAC, crossover from main to subs at 50hz and room correction. The A5's will run on a Counterpoint NP-220, with subwoofer duties falling to a pair of bridged QSC MX1500a's, running Multisub Optimiser bass management on the MiniDSP. The previous iteration of this system, running 604-168x's in Stonehenge 3 cabinets helped introduce me to my neighbour (well, the guy 2 houses down) who it turns out, also likes Pink Floyd. I will share some more updates as I assemble the cabinets, install drivers and get everything set up. Until then, have a good one! Christian Edited December 29, 2020 by Mr_Fried 8 1
cccrchairman Posted December 29, 2020 Posted December 29, 2020 Fine post Christian. Congratulations. I have no doubt the cabinets are in very safe and capable hands. +1 on manhandling massive cabinets. It’s 75 stairs down to my place. A test for even the most devout of altec owners. 2 1
MarcAL Posted December 29, 2020 Posted December 29, 2020 Yes, reading all this definitely does bring a tear to one’s eye. Keep up the great work and support guys. 2
Ian McP Posted December 30, 2020 Posted December 30, 2020 Plug Seven Records, Smith St Collingwood 3066 check pic! https://www.facebook.com/plug7pops/photos/5181058238600848 2
Ian McP Posted December 30, 2020 Posted December 30, 2020 speaking of Altec, some tasty vintage Western Electric horns https://resistormag.com/features/western-electric-horn-systems-time-travel-with-tim-gurney/ 2
crtexcnndrm99 Posted December 30, 2020 Posted December 30, 2020 What a resto job on those chipped ply cabs!! Well done, they will sound excellent. Ive always liked the varnished ply appearance similar to the ones at Plug Seven records (but I think it’s a bit late to say that )
rooferben Posted March 23, 2023 Posted March 23, 2023 On 29/12/2020 at 1:02 AM, Powerglide said: A few months back a friend asked if I could help in restoring a pair of A7’s back to their former glory. A previous owner had decided to strip back the original paint with the intention of clear coating the plywood boxes. He gave it a good go sanding completely back to raw ply but realised the construction methods, although strong, were never going to look that pretty without some extensive veneer work. Unfortunately the project was abandoned and the raw boxes were left exposed to the elements for some years. I don’t have any pics on how they looked pre start, the horn flares were varnished but the rest of the cabinets were rough as a bears arse and we disagreed on the best way to proceed (a box of matches was a suggested option) reluctantly I agreed to patch them up for paint. After a kilo of resin, sanding, filling, blocking, filling, swearing, blocking, they started to sharpen up but there were issues with areas of the ply being drummy. I think heavy sanding of the outer ply layer, the possible use of a chemical stripper and a lengthy period exposed to moisture had caused areas of the plywood bond to fail. After all my filling work I was quite savage digging off the loose ply and reglueing where I could, more filler........ Made a few upgrades to the internals first of all reinforcing the horn flares with a foaming glue that seeps into the joints then expands forming a kind of weld in the corners. I glued and screwed some plywood covers on the rear and back filled the cavities with expanding foam. I made ply stiffening panels for all the internal faces with 35 x 35 Baltic pine battens, glued and screwed from the rear then glued and screwed to the internals. The rear removable panels were in OK shape but we replaced the timber screws with nutserts and countersunk M6 bolts The port panels were replaced to the correct aperture and I moved them back into the enclosure for a neater look when used without the grilles. We applied a two pack high build undercoat to the raw ply which exposed more flaws...... more filler, more sanding, more undercoat, more sanding. Finally ready for a top coat in a two pack Matt matching the original grey. Before we began I was lucky enough to get a listen with some of the components that are going to be used and they definitely had the minerals. Eagerly awaiting an audition with the proper crossovers and a decent amp. I’m sure the owner will carry on this thread once the drivers are installed and he gets the grilles and decals sorted. Should end up something like this
rooferben Posted March 24, 2023 Posted March 24, 2023 Could you please share with me how you determined the port design. I am in the process of doing the similar project you have completed. Or just let me know the dimensions you used for the ports. Thanks
Powerglide Posted March 24, 2023 Author Posted March 24, 2023 There are multiple options depending on the model your working to, as I didn't build these from scratch I never measured them. you will find what your looking for here https://greatplainsaudio.com/altec-lansing-library/ 2
simo8989 Posted March 24, 2023 Posted March 24, 2023 2 hours ago, rooferben said: Could you please share with me how you determined the port design. I am in the process of doing the similar project you have completed. Or just let me know the dimensions you used for the ports. Thanks Like Powerglide said there are several options with the port opening please see the link and read up on the A7 / 825 cabinet design and read up on Jean Hiraga plans that he did in reducing the port. https://www.vtaf.com/altec-a7-voice-of-theatre-speakers.html#/ 1
rooferben Posted March 24, 2023 Posted March 24, 2023 Just wanted to thank you all for the links of information that have been provided. They are both a great read and a wealth of information. My build started out with a pair of A-7 500 magnificent cabs with some damage. Flipped the cabs on their bottom to get the woofer off the floor (like A-7). I still have a ways to go but I believe they will turn out nice. 4
Mr_Fried Posted March 25, 2023 Posted March 25, 2023 Hi Mate, welcome to the club! Those cabinets look fantastic. This is a good read and includes a link to the John Stronczer (Bel Canto) Sound Practices article on his A5 journey. Riggle can be a spot pretentious but his modified Hiraga crossover design is brilliant. The crossovers are the secret sauce and will utterly transform your system. https://www.vtaf.com/altec-a7-voice-of-theatre-speakers.html#/ 3
Powerglide Posted March 25, 2023 Author Posted March 25, 2023 (edited) https://www.lansingheritage.org/html/altec/plans/1970s-plans.htm Edited March 25, 2023 by Powerglide 1
rooferben Posted March 27, 2023 Posted March 27, 2023 Thanks Powerglide. I have been reading quite a bit about the A-7 speaker cabinets. The more I read the more excited I get about finishing this project.
rooferben Posted March 27, 2023 Posted March 27, 2023 The insulation in the A-7 cabs are in pretty bad condition. Has anyone ever used Roxul insulation? I have 2”, just wanted anyone’s thoughts.
MarcAL Posted March 27, 2023 Posted March 27, 2023 56 minutes ago, rooferben said: The insulation in the A-7 cabs are in pretty bad condition. Has anyone ever used Roxul insulation? I have 2”, just wanted anyone’s thoughts. For what it is worth ... if it is hazardous to your health and is going to be used in a vented enclosure then don't use it as the fibres will probably become airborne. I used a similar material which was recommended in the original Onken build back in the day and swear by it. If you can source this or something very similar such as 5 to 15mm woollen fibre carpet underlay then use it to start with. Don't glue it in, just staple it. Experiment with one enclosure by adding amounts layer by layer then by speaking inside of the enclosure and see how it sounds. Your ears will tell you when you have reached the correct amount so there is no need for fitting the speaker at this stage. Go by ear first as you really only want to reduce standing waves within the cabinet. If you use too much wadding you will kill your cabinets midrange response and it will sound dead. 15mm was the optimum thickness used in my Onken cabinets however I would expect a similar result in an A7 cabinet. 1
rooferben Posted March 28, 2023 Posted March 28, 2023 There is not really a problem with airborne fibers in my case. My room is very large, 24’x32’. I feel that the Roxul should be ok. Not sure where I would find another product in my area.
MarcAL Posted March 28, 2023 Posted March 28, 2023 6 hours ago, rooferben said: There is not really a problem with airborne fibers in my case. My room is very large, 24’x32’. I feel that the Roxul should be ok. Not sure where I would find another product in my area. Try the 5 to 15mm woollen fibre carpet underlay it can be found easily enough, its not ok, it works! Most of us Altec enthusiasts on this thread are using it and would highly recommend it, you won't be disappointed, trust us. 1
MarcAL Posted March 29, 2023 Posted March 29, 2023 This is the felt that we used in our A7 and Onken cabinets. Pictured 3 X 5mm thick woollen fibre carpet underlay. The same kind of felt that Altec used in their compression driver rear covers. 2
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