M007 Posted June 5, 2020 Report Share Posted June 5, 2020 Morning. After extensive reading(sans the Loudspeaker Cookbook), I’ve yet to find info regarding being able to put dual subs on the same baffle in a 4th Order BP... I’m designing the enclosure for my 2010 Tundra. It’ll be a blow thru and I only want the port firing thru as I’m in the south and it rains... a lot. My external gross dimensions for the enclosure are: H= 20” W= 48” D= 30.5”(depends on orientation of woofers as I can cut out a baffle if I can go 2 chamber instead of 3.) Seems 7 cubes sealed and 5.5 ported is my sweet spot with regards to my system goals. Subs are (2) JBL W15GTi mkii’s. They’re 10.25” deep, mounted. Therefore I can’t seem to fit them with their magnets facing each other in the ported chamber as it wouldn’t be wide enough. I’d like to have them oriented that way so I can just run the wires thru the port, as well as have superior cooling. They’re only going to get around 750w total, for now, but still. Amp is a JL HD750/1. I’ve modeled the enclosure on winISD to have the response I am looking for. Tuned to 34Hz. Around 12.5 cubes net. My main concern is if I put them on the same baffle, will the bracing be enough to overcome their momentum or will I need to beef up the enclosure? Or is it best just to mount them opposite each other, cones facing, like most do? I’m also open to clamshell style. The bold blue line is the enclosure. I modeled it against my previous ported 12 JBL for reference as well as added another sub or 2 so that I know I can swap something in, just in case the JBL 15’s malfunction. The port size seems questionable but winISD was spot on with my previous box so I figure I’ll just make the port removable as to plan for any potential issues. Thanks for any insight or direction in advance. Also, feel free to hit me with a link if I just can’t search correctly. Google has been acting funny lately, not sure if they changed their algorithm or what. Link to comment Share on other sites More sharing options...
1point21gigawatts Posted June 5, 2020 Report Share Posted June 5, 2020 That’s gonna sound flat and dull. Too much sealed volume in reference to ported volume. “How can we help you?” “And don’t forget to tell them that the customer isn’t always right.” Link to comment Share on other sites More sharing options...
M007 Posted June 6, 2020 Author Report Share Posted June 6, 2020 7 hours ago, 1point21gigawatts said: That’s gonna sound flat and dull. Too much sealed volume in reference to ported volume. Flat as in “not peaky”? I played around with a lot of variations and this seemed to be the best way for me to get the 20-40Hz response I like. Not fond of too much bass/mid bass. Love the low lows. Don’t have a program to model a 6th order. Other than that, should I just say screw it and build a 9 cube single sub ported tuned to 20Hz and be done? I’d only have to cut away around 10% of the rear wall for that and I’d optimize my amp and have a sub left over to put in the home theater... Link to comment Share on other sites More sharing options...
1point21gigawatts Posted June 6, 2020 Report Share Posted June 6, 2020 On a 4th order enclosure you never wanna peak below 40hz or it will take away from your output. 45hz is ideal. The tuning of the potted section is where you will peak at. The port area has to be equal to or around half the total cone area of the subwoofer(s). Make the port closest to a square shape oppose to a rectangle shape as you can. Make the sealed section what the subwoofers recommendation for a sealed enclosure is. Then make the ported section double (2:1 ratio) to triple (3:1 ratio) that size. If you don’t want hard hitting bass (it’ll get low too) then don’t go with a 4th order enclosure. Then tuning of the port on a 4th order enclosure isn’t the same aspect as the tuning on a regular enclosure. The sealed section and ported section work together and hit nice on low notes and higher ones but the peak will be what the port is set to. 45hz is ideal. Going lower in tuning in a 4th order enclosure will not make you hit lower notes better, it will do the complete opposite. Never tune below 40hz and never tune above 50hz when building a 4th order enclosure. 45hz is the best peak frequency and will hit the hardest, so that’s what you want. The low notes will get low and sound nice as long as you don’t go against what I’m telling you and tune that enclosure lower like you’re doing a regular enclosure. You have to keep in mind that since it’s working with a sealed enclosure it will play low notes super nice and the ported section will play higher bass notes super nice. Sealed section focuses on lower frequencies and the ported section focuses on higher frequencies. Before you even start building a 4th order enclosure, you have to make sure the subwoofer(s) are 4th order enclosure friendly. Meaning do they work well in a sealed enclosure basically. Because the sealed section is where the subwoofers are going to be mounted. If inverted with the magnet(s) in the ported section then you have to change the phase or polarity of the subwoofers. Either go to the phase knob or switch in your amp and set it to 180 or if your amp doesn’t have that then wire your subwoofer(s) in reverse, run the wire regular positive to positive and negative to negative out of your amp and wire the negatives on the subwoofer(s) as positives and the positives as negatives to reverse the polarity. Do one or the other. NEVER BOTH. If the subwoofers are mounted regular in the sealed section then you don’t have to change any settings or wiring. My bad I ran off on a rabbit trail. But you need to know that. But back to what I was saying about making sure the subwoofer(s) are 4th order enclosure friendly. Look at the QTS of the subwoofer and make sure it is 0.50 or higher (0.48 would be the absolute lowest I would go) or the subwoofer(s) will not preform well in a 4th order enclosure and you’ll smell them voice coils because the subwoofer(s) will get too hot in a sealed enclosure. That’s always a smell that bassheads do not like. “How can we help you?” “And don’t forget to tell them that the customer isn’t always right.” Link to comment Share on other sites More sharing options...
M007 Posted June 6, 2020 Author Report Share Posted June 6, 2020 4 minutes ago, 1point21gigawatts said: What kind of subwoofer(s) do you plan on using for this build you’re talking about? If I know that then I can point you in the right direction. Thanks for the informative post above this one as well. I ordered the speaker cookbook. Lol. The speakers are: JBL W15GTI MKii’s. JBL even lists their own enclosure specs for a 4th order, and people have said they’re pretty spot on. I just wanted to complicate things, as usual. Lol. Here’s their specs and pic of their enclosure. With ported(12”), I used winISD. Like you said tho, 4th order tunes different. I didn’t realize that. I erroneously assumes lower tune got me more low bass than upper bass so I wouldn’t have to eq it out. Link to comment Share on other sites More sharing options...
1point21gigawatts Posted June 6, 2020 Report Share Posted June 6, 2020 1 hour ago, M007 said: Flat as in “not peaky”? I played around with a lot of variations and this seemed to be the best way for me to get the 20-40Hz response I like. Not fond of too much bass/mid bass. Love the low lows. Don’t have a program to model a 6th order. Other than that, should I just say screw it and build a 9 cube single sub ported tuned to 20Hz and be done? I’d only have to cut away around 10% of the rear wall for that and I’d optimize my amp and have a sub left over to put in the home theater... What kind of subwoofer(s) do you plan on using for this build you’re talking about? If I know that then I can point you in the right direction. “How can we help you?” “And don’t forget to tell them that the customer isn’t always right.” Link to comment Share on other sites More sharing options...
M007 Posted June 6, 2020 Author Report Share Posted June 6, 2020 These are better pics. Link to comment Share on other sites More sharing options...
1point21gigawatts Posted June 6, 2020 Report Share Posted June 6, 2020 Let me tell you a basic 4th order enclosure layout for them subwoofers. Hold up. “How can we help you?” “And don’t forget to tell them that the customer isn’t always right.” Link to comment Share on other sites More sharing options...
1point21gigawatts Posted June 6, 2020 Report Share Posted June 6, 2020 Sealed section-3.29 cubic feet or closest to as you can get. 3 cubic feet is what the subwoofers call for. 0.26 cubic feet is the total displacement of the 2 subwoofers. 0.02-03 is the displacement for bracing. ported section-9 cubic feet or closest to as you can get. Making it a 3:1 ratio. port measurements-10.25”x11” has to be exact port tuning-45hz external port so you don’t have to figure port displacement in the ported section mount the subwoofers regular in the sealed section. Each subwoofer has a displacement of .13. Put a brace in the sealed section in between the subwoofers. The brace will have a displacement of about 0.02-03 cubic feet. No need to brace the ported section because you are not gonna be feeding it enough to need bracing in the ported section. “How can we help you?” “And don’t forget to tell them that the customer isn’t always right.” Link to comment Share on other sites More sharing options...
M007 Posted June 6, 2020 Author Report Share Posted June 6, 2020 8 minutes ago, 1point21gigawatts said: Sealed section-3.29 cubic feet or closest to as you can get. 3 cubic feet is what the subwoofers call for. 0.26 cubic feet is the total displacement of the 2 subwoofers. 0.02-03 is the displacement for bracing. ported section-9 cubic feet or closest to as you can get. Making it a 3:1 ratio. port measurements-10.25”x11” has to be exact port tuning-45hz external port so you don’t have to figure port displacement in the ported section mount the subwoofers regular in the sealed section. Each subwoofer has a displacement of .13. Put a brace in the sealed section in between the subwoofers. The brace will have a displacement of about 0.02-03 cubic feet. No need to brace the ported section because you are not gonna be feeding it enough to need bracing in the ported section. Thanks a lot! So sounds like a 2 chamber design and how long does that port have to be? Link to comment Share on other sites More sharing options...
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