Rudy81 Posted February 18, 2019 Share Posted February 18, 2019 There are some old PPSL threads on a La Scala with PPSL and I am wondering if anyone built any PPSL prototypes? I am in the middle of a prototype build for a ported PPSL 15" driver box. Goal is to have a true 2-way setup with my Oris. I'm hoping to be able to run the low end from approximately 20hz-300hz. I would appreciate any tips on such a project if anyone actually built the PPSL ported box. I have tried to contact Les Hudson, who actually sells them but never got a response. PPSL would look something like the box on the right of the picture below. Quote Link to comment Share on other sites More sharing options...
Don Richard Posted February 18, 2019 Share Posted February 18, 2019 DJK, RIP, had written about the PPSL design here and on other audio forums. If you search the archives there are several threads about PPSL bass bins, both here and elsewhere. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted February 18, 2019 Author Share Posted February 18, 2019 34 minutes ago, Don Richard said: DJK, RIP, had written about the PPSL design here and on other audio forums. If you search the archives there are several threads about PPSL bass bins, both here and elsewhere. I have obtained and read most of the available information put out by DJK and Les Hudson. I was hoping someone had actually built one. I guess I'll see how my prototype works once the drivers arrive tomorrow. I chose Dayton DCS380-4 15" drivers for this project. Quote Link to comment Share on other sites More sharing options...
The Dude Posted February 18, 2019 Share Posted February 18, 2019 I know it doesn't help any, but I know DJK did build a set of his. I think it was one of the last things he posted about. Kind of looked like a Belle. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted February 18, 2019 Author Share Posted February 18, 2019 4 minutes ago, The Dude said: I know it doesn't help any, but I know DJK did build a set of his. I think it was one of the last things he posted about. Kind of looked like a Belle. Yes, I have the photo's of his working design. I also have the cut sheet diagrams he posted for a similar build. I am basing my sizing and design on DJK's, but am orienting the slot as did Les Hudson. I'm not sure if the slot orientation matters, but I am trying to keep the slot as small as possible in order to maximize available cabinet volume for the drivers. Both DJK and Les spoke very highly of the quality of bass produced by that design. I have been very curious, so am going to give it a shot. If this doesn't pan out, I might try the Linkwitz Dipole woofer design. 1 Quote Link to comment Share on other sites More sharing options...
The Dude Posted February 19, 2019 Share Posted February 19, 2019 I hope you find a solid plan, I would be curious to see what your thoughts are between the ppsl and the ob. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted February 19, 2019 Author Share Posted February 19, 2019 I really do like the sound of the OB. As we all know. the issue with any OB is that is just can't get below 40 or 50hz very well. At least now with a very specialized driver. Even then, 20hz is out of the question. I have thus far used two RSW-15's to go down to 20hz. But, I would like to be able to build a true 2-way system with my Oris horns. I am hoping this might work. I should have the drivers installed tomorrow afternoon and will take some performance measurements as soon as I can. 1 Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted February 19, 2019 Author Share Posted February 19, 2019 Drivers are in. Rainy and cold here in North Texas. Took a quick measurement outside to see what kind of performance I got on my prototype. Overall not bad, but I am hoping to figure out how to get the response just above 350hz to give me some leeway in my crossover selection.....back to the drawing board. Quote Link to comment Share on other sites More sharing options...
glens Posted February 19, 2019 Share Posted February 19, 2019 Are you sure that's not just an artifact of dividing ~39" by an unfortunate integer with the source and/or mic? Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted February 19, 2019 Author Share Posted February 19, 2019 Right now I'm not sure where the issue lies. I do know that the plenum size affects the response quite a bit. I will try reducing the plenum volume as much as I can and see what effect that has. Quote Link to comment Share on other sites More sharing options...
moray james Posted February 20, 2019 Share Posted February 20, 2019 You can reduce the plenum volume by filling in the corners inside of the plenum at the back. The depth of the plenum sets the resonant frequency so larger woofer means a lower resonance and a narrower bandwidth. Keep the drives as close as is comfortable for you to maneuver inside to bolt them down. You could also contrive in include corner blocks in the front after the drivers are installed. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted February 20, 2019 Author Share Posted February 20, 2019 1 minute ago, moray james said: You can reduce the plenum volume by filling in the corners inside of the plenum at the back. The depth of the plenum sets the resonant frequency so larger woofer means a lower resonance and a narrower bandwidth. Keep the drives as close as is comfortable for you to maneuver inside to bolt them down. You could also contrive in include corner blocks in the front after the drivers are installed. I was hoping you would chime in. You have summarized everything I have been able to gather on the subject. I think I should be able to shave 3/8" on the width of the slot for the final build. I will fill the excess space at the back of the slot tomorrow and try again. I have been contemplating making the back of the slot curved, mirroring the curve of the drivers for the final build, if it materializes. I have not seen any comments on going that route. Any guess as to whether that would be good or bad? Quote Link to comment Share on other sites More sharing options...
moray james Posted February 20, 2019 Share Posted February 20, 2019 a curved compartment will fill in a little more volume than just filling the corners what ever winds up being the most convenient build method for you should be fine.You end up having to be open on one side I thought a squared off compartment would probably be the easiest to work with but what ever idea works for you. Looking forward to your results. ScottL at Audioasylum has built a number of PPSL woofers I have only built three, you might give him a ping. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted February 20, 2019 Author Share Posted February 20, 2019 10 hours ago, moray james said: a curved compartment will fill in a little more volume than just filling the corners what ever winds up being the most convenient build method for you should be fine.You end up having to be open on one side I thought a squared off compartment would probably be the easiest to work with but what ever idea works for you. Looking forward to your results. ScottL at Audioasylum has built a number of PPSL woofers I have only built three, you might give him a ping. Do you still use your builds? What were your overall impressions of the sound relative to a simple ported design? Quote Link to comment Share on other sites More sharing options...
moray james Posted February 20, 2019 Share Posted February 20, 2019 2 hours ago, Rudy81 said: Do you still use your builds? What were your overall impressions of the sound relative to a simple ported design? I built four double driver units in total, I made one in a ripol fashion with the drivers face to face and in the other three the two drivers were nested with the magnet on one tucked into the cone of the other. The first ripol version was for two twelve inch units and was not overly solid, it was simply a proof of concept the other three were solid and built with 3/4" baltic birch, two I built for a friend (he supplied the expensive birch ply) and I made one for myself these were all with dual 12" drivers. The cabinets which I built were designed to be physically as small as possible. I decided that a 15" would be a better minimum driver size than a 12" and I think a 18" would be better than a 15". My friend is very pleases he still uses his mine is on a shelf right now as the amp I had to drive it got sick and I wanted to build larger driver version. I was and am also interested in adding more volume (cabinet) to tune the woofer as Scott did but I don't have the space any longer for subs that large so I am coasting. I liked the sound, it is very natural and you can forget it is there until some low passage happens and reminds you. I think compared to a ported design this method is more realistic sounding than the other subs I have had in the past (vented and T-Line) They were seemingly more impactful but in comparison they were more "one note" sounding. I think that a larger woofer and one with more peak to peak than I used would make up for the slight lack of impact I that experienced but the weight and depth/bass extension is there and the bass is well controlled and articulate. A clean well behaved sound overall. I hope this helps. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted February 20, 2019 Author Share Posted February 20, 2019 It certainly help. I have been in touch with ScottL and he still uses his. He gets his response up to 500hz. Drops off a cliff at 575hz or so. The consensus for the top end is to make the slot as shallow as possible and keep the drivers close together, as you indicated. I am hopeful for this concept since I only need 20hz to 300hz or so. With my Oris horns, that could be a great 2-way solution. I hooked the prototype up in my shop with no xover and was rattling the walls in there. Seemed to have a lot of impactful bass. Headed back to the shop to work on the slot size. When done, I will take another measurement and also take a look at where the box tuning ended up. Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted February 20, 2019 Author Share Posted February 20, 2019 Reduced the slot size as much as possible while still leaving enough room to load the drivers. Clearly, reducing slot depth improves upper range performance. I will have to look at reducing slot size more and getting drivers closer to each other. Only way to do that is to add some sort of loading door for the drivers. Quote Link to comment Share on other sites More sharing options...
zobsky Posted February 21, 2019 Share Posted February 21, 2019 Maybe I missed it but what were your cabinet dimensions and tuning ? Quote Link to comment Share on other sites More sharing options...
Rudy81 Posted February 21, 2019 Author Share Posted February 21, 2019 21 minutes ago, zobsky said: Maybe I missed it but what were your cabinet dimensions and tuning ? Tuning should be around 25hz. Net volume is 8.7 cu. ft. with a total volume of a little over 10 cu. ft. if I recall correctly. From my discussions on the diyAudio forum, I will need to reduce the volume of the slot. This will call for some type of access into the cabinet in order to have access to the drivers in the future. I'm thinking something like the back panel of a Cornwall. Easily removable if necessary. 1 Quote Link to comment Share on other sites More sharing options...
zobsky Posted February 21, 2019 Share Posted February 21, 2019 Probably not an option for your current prototype but have you considered a removable slot manifold sub-assembly? Quote Link to comment Share on other sites More sharing options...
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