Mikerodrig27 Posted November 2, 2020 Share Posted November 2, 2020 (edited) I just bought a pair of Forte II speakers. All of the drivers except for one passive radiator are in great shape. I found a recone kit that will solve that problem. I wanted to see if anyone had suggestions on modifying the dimensions on the cabs etc. I was thinking of adding an extra 1/2" of depth so that i can add bracing to the inside and not take up too much volume. Then I thought, would adding 2" of volume make the speaker sound better? Let me know if any of you have successfully modified the specs of the cabinets. I will be reusing the front baffles but that is it. I may be able to salvage the rears but I don't think they are critical. I will likely wrap these in walnut veneer like the originals. Other thoughts are Mahogany which is cheaper and more spectacular looking. image uploader Edited November 2, 2020 by Mikerodrig27 Quote Link to comment Share on other sites More sharing options...
BTCurp Posted November 2, 2020 Share Posted November 2, 2020 Unless you know how to model your changes with software, I would never change the stuffing of a sealed enclosure, port length of a ported/vented enclosure, weights on a passive radiator or change the volume of any enclosure. This has a direct impact on frequency response and power handling. I rebuilt some KG 5.5's, completely new cabinets with new dimensions (taller and more slender for a sleeker look rather than short and fat), I added battens (braces in the corners) and 1" dowels all over, left to right, front to back, but I calculated the volume for all of those and my final cabinet volume with everything installed and assembled is within .01 ft^3 of the original enclosure. I changed the port to a nice flared port but that required its own calculation as well. Good luck! 1 Quote Link to comment Share on other sites More sharing options...
Alexander Posted November 2, 2020 Share Posted November 2, 2020 If a little is good more rarely is better. Be careful with this bracing stuff – it can get out of hand real fast doing more harm than good. Smaller well placed braces can help a lot more than a bunch of randomly placed pieces of wood inside the cabs. 1 Quote Link to comment Share on other sites More sharing options...
tlarwa Posted November 2, 2020 Share Posted November 2, 2020 I modded a pair of Forte IIs a while ago ... great project, and the speakers sounded really good. Link here ... might give you some ideas. 1 Quote Link to comment Share on other sites More sharing options...
Alexander Posted November 2, 2020 Share Posted November 2, 2020 3 hours ago, tlarwa said: I modded a pair of Forte IIs a while ago ... great project, and the speakers sounded really good. Link here ... might give you some ideas. Curios if the 3.5% volume displacement was based off the total cubic volume of an empty cab or with the volume of the installed drivers factored in? 1 Quote Link to comment Share on other sites More sharing options...
OO1 Posted November 2, 2020 Share Posted November 2, 2020 9 hours ago, Mikerodrig27 said: I was thinking of adding an extra 1/2" of depth so that i can add bracing to the inside and not take up too much volume. Then I thought, would adding 2" of volume make the speaker sound better? image uploader the Forte III is also deeper by 3/4 of an inch ---a full 13 inches ---so there should not be any problem - 1 Quote Link to comment Share on other sites More sharing options...
Mikerodrig27 Posted November 3, 2020 Author Share Posted November 3, 2020 Thanks for the responses. I may try building one a little larger to see what it sounds like. I eventually want to get a MiniDSP mic or something similar to measure results. From what I have seen with DIY speaker kits, enlarging the cabinet, switching from ported to bass reflex doesn't require crossover changes. This is with fairly high end speakers as well. I am going to start doing some research tomorrow night (tonight I am finishing up a rebuild of a Marantz 2215b). From my brief time reading about it, the passive radiator (PR) acts as a port essentially. If I enlarge the volume in the cabinet, I need to add a little more weight to the PR in order to tune it down so that the woofer doesn't put out too much bass. I guess the only question is, will the woofer work well in a larger lower tuned cabinet. Dampening I am not concerned with. I can add and remove that easily. I will have some bracing in the new cabinets. The dampening would be to just cut down on reflections in the cabinet. There is a lot of dialogue that comes from the woofer... At least in my Forte I's (another set that I have) that I have spent some time messing with. Quote Link to comment Share on other sites More sharing options...
Alexander Posted November 3, 2020 Share Posted November 3, 2020 Be careful with adding weight to passives, tried that trick on a pair of forte IIs against the advice of @BEC a few years back. I ended up having to re-cone them after they were so badly torn up. I believe it was ~ 2-2.5oz added IIRC. 1 Quote Link to comment Share on other sites More sharing options...
tlarwa Posted November 3, 2020 Share Posted November 3, 2020 21 hours ago, Alexander said: Curios if the 3.5% volume displacement was based off the total cubic volume of an empty cab or with the volume of the installed drivers factored in? This goes back a ways, but I believe it was based off the internal volume of the empty cabinet, sans drivers. 1 Quote Link to comment Share on other sites More sharing options...
OO1 Posted November 3, 2020 Share Posted November 3, 2020 4 hours ago, Mikerodrig27 said: If I enlarge the volume in the cabinet, I need to add a little more weight to the PR in order to tune it down so that the woofer doesn't put out too much bass. I guess the only question is, will the woofer work well in a larger lower tuned cabinet. nope , the Forte III uses the same PR and it is already a deeper cab , so all should be ok with the woofer - if you sense any issues , just line the rear panel with acoustic foam of 1/2 to 3/4 inch thick -simple - 1 Quote Link to comment Share on other sites More sharing options...
Mikerodrig27 Posted November 4, 2020 Author Share Posted November 4, 2020 11 hours ago, Alexander said: Be careful with adding weight to passives, tried that trick on a pair of forte IIs against the advice of @BEC a few years back. I ended up having to re-cone them after they were so badly torn up. I believe it was ~ 2-2.5oz added IIRC. I need to recone one passive radiator. It is all beat up from the Previous owner. I am leaning towards not messing around with the weight. I think the 15" driver is fragile. Messing with the broken one a little bit it seems to be a rather thin material that rips easily. 10 hours ago, RandyH000 said: nope , the Forte III uses the same PR and it is already a deeper cab , so all should be ok with the woofer - if you sense any issues , just line the rear panel with acoustic foam of 1/2 to 3/4 inch thick -simple - Awesome. I never liked the tall skinny look of the Forte's. This will help mitigate that. Between the extra depth for the bracing that I am going to add and the 3/4" of depth it should help mitigate that. Using tlarwa's spec of the bracing taking up 3.5% of the space, that would ad a depth of roughly 1/2". That combined with the 3/4" will equal 1 1/4" of extra depth. I agree that I can just fill the space if I don't like the sound for some reason. Thanks for all of the responses! Quote Link to comment Share on other sites More sharing options...
OO1 Posted November 4, 2020 Share Posted November 4, 2020 49 minutes ago, Mikerodrig27 said: Thanks for all of the responses! much obliged - Quote Link to comment Share on other sites More sharing options...
Mikerodrig27 Posted November 29, 2020 Author Share Posted November 29, 2020 A few teaser shots on what I hope is progress Quote Link to comment Share on other sites More sharing options...
Mikerodrig27 Posted November 29, 2020 Author Share Posted November 29, 2020 Surprisingly, my biggest obstical has been learning how to do nearfield testing with a calibrated mic that I bought (UMM-6). My latest knowledge is that you measure the woofer, the port and depending on how high in frequency your test goes, mid and tweeter. All nearfield. Once I figure out the tuning frequency, I am going to order a precision port: https://www.parts-express.com/precision-port-4-flared-speaker-cabinet-port-tube-kit--268-352 I have a pair of Forte I's that I am comparing them to. As of right now, I can say the new cabinets, dampening produce way cleaner bass. I have hope! Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.