John G Posted January 1, 2009 Report Share Posted January 1, 2009 hi and happy new year!I am building a pair of the older Large Advents. By these I mean the woofers having the masonite rings and the tweeters being mounted diagonally on the plate.Essentially I have a collection of parts and new cabinets so I am hoping to get all the details right so they will sound as good as possible. Questions that come up include:* what to put inside the cabinet? insulation or foam or something else* do you seal both the woofer and tweeter ?? Is a silicone sealer optimal?* wiring: does Red go to the woofer and Yellow to the tweeter? (with black to each)* crossover: do you hot glue it to the rear from the inside?* the crossovers I have do not have the toggle switch but show "The Advent/1" and "Cambridge Massachusetts" as well as an "HH 030249" on them. Do I have the right ones?* how far off of the floor do you guys like to operate these?I bought the cabinets new, in the box years ago and am finally getting around to making use of them. thanks! John - MA Link to comment Share on other sites More sharing options...
Guest JonM Posted January 2, 2009 Report Share Posted January 2, 2009 I have two pairs of original Larger Advents (and am in the process of putting new surrounds on one set and new crossover caps in all of them), so my recommendations are based on what I see in my Advents.Stuffing? Fiberglass is your best choice. Do a search on this site to find out just how much. You'll want to put some cheesecloth between the back of the woofer and the fiberglass to keep the little pieces of the stuff where they belong. (Advent did this.) Fiberglass is better than foam (or polyfill) because the function of the stuffing is actually to keep the instantaneous temperature of the air in the cabinet stable as the backwave of the woofer travels through it - thermodynamically this makes the cabinet "appear" significantly larger to the backwave of the woofer - and fiberglass has finer fibers than polyfill or foam, and hence can absorb and release heat energy into the air in the cabinet faster than the other two. (One pair of my Advents has fiberglass, the other has foam. Advent turned to using foam sometime around 1975, probably to cut costs.)Yes, seal both the woofer and tweeter. Rope caulk (available at any hardware store) works well for the woofer. The tweeters originally had foam sheets for a gasket behind the metal plate. Assuming you don't have those, then a thin strip of rope caulk behind the metal plate will do to seal the tweeter, too. Don't bend the plate when you tighten the screws.Red goes to the woofer (+), yellow to the tweeter (+).The Advent/1 was a successor to the smaller Advent - it used the drivers from the large Advent in a smaller enclosure. I don't know if the crossover frequency is different from the large Advent. I assume a search on this site will turn up more info. Are your cabinets the same dimension as the original larger Advents?Distance from the floor is only one thing to consider in positioning the speaker. You'll also need to think about distance to the side walls and to the wall behind the speaker. I would start with the woofer's center roughly 18-24" off the ground, and then roughly 32" from wall behind and roughly 50" from the center of the woofer to the side walls. (The formula is that one dimension is about 1.6x the previous, to smooth out the room gain you get across as much of the frequency range of the woofer as you can, to reduce bumps and dips in the woofer's in-room response.) Then, you experiment, moving the speaker around and listening for a sound you like in a location you can live with. Let your ear be your guide - formulas only give you a starting point for your experiments.Have fun!JonM Link to comment Share on other sites More sharing options...
John G Posted January 3, 2009 Author Report Share Posted January 3, 2009 hi JonThanks for the wealth of information!! Esp the science behind the insulation filling! Had no idea of the issues at work there...I do have the original foam sheets for the tweeters...The cabinets outside measurements are: 25 1/2 " high by 14" wide by 11 1/2" deep. The front has a 45 degree bevel to it. They came with the holes drilled for the speaker mounting screws and these line up perfectly with the woofer and tweeter I described. The cabinets are some kind of particle board with a wood veneer. I should have added that they came in factory boxes from Advent.I will experiment with the positioning per your suggestions (I have a pair of the later Large Advents I bought in 1978) while I get these built. My hope is to have 4 in the room.There seem to be many possible ways to improve on the crossovers as I look through the posts in this forum... fortunately they seem cheap and easy to try. thanks again! JohnI have two pairs of original Larger Advents (and am in the process of putting new surrounds on one set and new crossover caps in all of them), so my recommendations are based on what I see in my Advents.Stuffing? Fiberglass is your best choice. Do a search on this site to find out just how much. You'll want to put some cheesecloth between the back of the woofer and the fiberglass to keep the little pieces of the stuff where they belong. (Advent did this.) Fiberglass is better than foam (or polyfill) because the function of the stuffing is actually to keep the instantaneous temperature of the air in the cabinet stable as the backwave of the woofer travels through it - thermodynamically this makes the cabinet "appear" significantly larger to the backwave of the woofer - and fiberglass has finer fibers than polyfill or foam, and hence can absorb and release heat energy into the air in the cabinet faster than the other two. (One pair of my Advents has fiberglass, the other has foam. Advent turned to using foam sometime around 1975, probably to cut costs.)Yes, seal both the woofer and tweeter. Rope caulk (available at any hardware store) works well for the woofer. The tweeters originally had foam sheets for a gasket behind the metal plate. Assuming you don't have those, then a thin strip of rope caulk behind the metal plate will do to seal the tweeter, too. Don't bend the plate when you tighten the screws.Red goes to the woofer (+), yellow to the tweeter (+).The Advent/1 was a successor to the smaller Advent - it used the drivers from the large Advent in a smaller enclosure. I don't know if the crossover frequency is different from the large Advent. I assume a search on this site will turn up more info. Are your cabinets the same dimension as the original larger Advents?Distance from the floor is only one thing to consider in positioning the speaker. You'll also need to think about distance to the side walls and to the wall behind the speaker. I would start with the woofer's center roughly 18-24" off the ground, and then roughly 32" from wall behind and roughly 50" from the center of the woofer to the side walls. (The formula is that one dimension is about 1.6x the previous, to smooth out the room gain you get across as much of the frequency range of the woofer as you can, to reduce bumps and dips in the woofer's in-room response.) Then, you experiment, moving the speaker around and listening for a sound you like in a location you can live with. Let your ear be your guide - formulas only give you a starting point for your experiments.Have fun!JonM Link to comment Share on other sites More sharing options...
Pete B Posted January 4, 2009 Report Share Posted January 4, 2009 http://baselaudiolabs.googlepages.com/ADVENT_LA_XO.html Link to comment Share on other sites More sharing options...
JKent Posted January 4, 2009 Report Share Posted January 4, 2009 http://baselaudiolabs.googlepages.com/ADVENT_LA_XO.htmlPete,did you ever determine how much (by weight) fiberglass to use, to replace the foam?Happy New YearKent Link to comment Share on other sites More sharing options...
Carlspeak Posted January 5, 2009 Report Share Posted January 5, 2009 Pete,did you ever determine how much (by weight) fiberglass to use, to replace the foam?Happy New YearKenthttp://www.classicspeakerpages.net/IP.Boar...ic=2895&hl=FWIW, Link to comment Share on other sites More sharing options...
Pete B Posted January 5, 2009 Report Share Posted January 5, 2009 http://www.classicspeakerpages.net/IP.Boar...ic=2895&hl=FWIW,Kent,Here's a picture of an early (1972) LA with the woofer removed, it is alloriginal. As I have stated before, I simply run standard pink housing insulationfrom top to bottom, side to side, layered front to back. I just measured someoriginal stuffing as shown below, it is 6 pieces, each 14" X 12", stacked in 3layers front to back. The stack of 3 measures 8" in depth. One stack of 3 hasa slit half way into the rectangle to allow the wires to pass through.http://baselaudiolabs.googlepages.com/LA_STUFF.JPG Link to comment Share on other sites More sharing options...
John G Posted January 7, 2009 Author Report Share Posted January 7, 2009 When you say "standard" I assume you mean the 3 1/2" thick that people put in walls.Thanks for both the info and picture! Johnquote name='Pete B' date='Jan 5 2009, 11:39 AM' post='76967']Kent,Here's a picture of an early (1972) LA with the woofer removed, it is alloriginal. As I have stated before, I simply run standard pink housing insulationfrom top to bottom, side to side, layered front to back. I just measured someoriginal stuffing as shown below, it is 6 pieces, each 14" X 12", stacked in 3layers front to back. The stack of 3 measures 8" in depth. One stack of 3 hasa slit half way into the rectangle to allow the wires to pass through.http://baselaudiolabs.googlepages.com/LA_STUFF.JPG Link to comment Share on other sites More sharing options...
Pete B Posted January 9, 2009 Report Share Posted January 9, 2009 Hi John,I measured it as 2.7" thick but it did look a bit compressed so it might have started as3.5". I suppose that I should weight it to confirm.When you say "standard" I assume you mean the 3 1/2" thick that people put in walls.Thanks for both the info and picture! Johnquote name='Pete B' date='Jan 5 2009, 11:39 AM' post='76967']Kent,Here's a picture of an early (1972) LA with the woofer removed, it is alloriginal. As I have stated before, I simply run standard pink housing insulationfrom top to bottom, side to side, layered front to back. I just measured someoriginal stuffing as shown below, it is 6 pieces, each 14" X 12", stacked in 3layers front to back. The stack of 3 measures 8" in depth. One stack of 3 hasa slit half way into the rectangle to allow the wires to pass through.http://baselaudiolabs.googlepages.com/LA_STUFF.JPG Link to comment Share on other sites More sharing options...
Pete B Posted January 9, 2009 Report Share Posted January 9, 2009 Hi John,I measured it as 2.7" thick but it did look a bit compressed so it might have started as3.5". I suppose that I should weight it to confirm.Just noticed that no one answered this part of your question. You say your woofersare masonite, and tweeters diagonal, I think you mean with small masonite platesrotated slightly, or the early tweeters. If so, then your drivers are all ealry LA partswhereas your Advent/1 crossover would work for New Large Advents. The wooferinductor is completely wrong, and the tweeter network is first order rather than2nd order. I suggest that you buy or build what we call Rev2 (16/8/3) crossoversshown in Figure 3 here:http://baselaudiolabs.googlepages.com/ADVENT_LA_XO.htmlI don't really like the decrease position on the switch and it can be used for otherpurposes if you are not looking to make them 100% original.Hope you try BSC with them! Link to comment Share on other sites More sharing options...
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