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Slot port Tang Band w8-740p subwoofer advice/suggestions

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  • Slot port Tang Band w8-740p subwoofer advice/suggestions

    I've searched and read just about everything I can find from a google search regarding this subwoofer and DIY builds with it. I built a sealed subwoofer with it a year ago and used the yung 200watt amp from PE. It was in a small room. I liked it, but I know that isn't the best/loudest/optimum setup to get the most out of this sub. The amp stopped working after a lightning storm last summer so I just forgot about it for a while.

    Ok so a month ago I received a gift card from my job and decided to buy the Dayton 250 watt plate amp. I have been obsessively researching a slotted port design for this sub. I am trying to decide whether I want to tune to 25, 30, or 35 hz. So far I've used winisd and online calculators to design a box tuned for 25hz and 35hz. I figured it was time to ask for advice, comments, and/or suggestions from people that know much more than me. I live in a studio-ish apt and this will be in my kitchen/living room combo. The room is rectangle about ~15X12. I have a custom ported sub with a 6.5 tang and 70 watt amp and it's ok for music, but I want more. Maybe I will double up with the new one OR move the 6.5 to my bedroom and let the new 8 inch tang perform alone in my living room. I have no room constraints as far as size, and I can thump it loud very often. It's a dream come true bachelor pad, ha.

    Ok so I want this sub to perform for music and movies. 80% music. That is what initially led me to only considering a 35hz tune. It is nice that it's a bit smaller, but then I started thinking about no size constraints and using it for movies too. Hence considering 25hz or 30hz. The dayton amp has a high pass crossover at 20hz and I've considered that in winisd (cuts down on excursion and port velocity). So I'll attach the transfer function graph, the port velocity graph, and cone excursion graph. I will design the port roughly 1 inch high, and between 9 and 10.5 inches wide (for the 35 and 25hz tune respectively). The port will use the walls and bottom, then fold about 3 times before opening to the main cabin. I've found examples of success with this design online on various forums with this amp in fact. Given everything I've said and the graphs, what do you all think? I want to enjoy the occasional action movie scenes, but am most interested in music, hip hop, reggae, EDM, some of the lowest music, I guess. Oh the volume for the 35hz tune is .577 ft^3 and for the 25hz tune is 1.11 ft^3. I can make either design work, but as you can see the box nearly doubles in size for the 25hz. Is a 30hz design a decent compromise? Can this 8 inch driver even do 25hz well? I just can't assess this given my state of knowledge. If you request more information let me know. Thanks for reading.
    Transfer function (purple 25hz, green 35hz) Max port velocity for 250watts (RMS for amp) purple 25hz, green 35hz. Cone excursion purple 25hz, green 35hz

  • #2
    Here's the (a) problem - Mr. Zarbo had one of those woofers and (IINM) his measurements weren't very close to TB's AT ALL.
    TB's Qts, Fs, Vas:
    tb: 0.30, 28, 0.81cf
    tz: 0.32, 35, 0.30 <-THIS could change everything

    Unless you can DATS your actual driver, I'd go w/something more like 0.25cf tuned to 40Hz. This is on the small side (but still usable) for one set of parms, yet still usable (but on the large side) with the other set. Wouldn't expect much lower than 40 out of it w/out room gain.

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    • #3
      I am surprised to hear this. Many people have built DIY subs with this driver through the years and I haven't read any accounts of the TS parameters being so "off". Thanks for pointing this out to me. Is it well known among the knowledgeable DIY crowd that TB's TS parameters are off by so much? Pardon my ignorance, but why do you say that 40hz is as low as i should shoot for? Do you think the driver just can't go much lower? Is that the size that will give the flattest response for that tuning frequency? Lets just say that hypothetically the TS parameters that TB states are correct...... and I want to try for 35 OR 25 hz, what do you think of my box designs as far as what you see in the graphs and/or my idea for the slot port with those dimensions? In addition to advice and/or suggestions on what I'm trying to do, I'm also trying to gain some knowledge here, and you seem quite knowledgeable. Thanks for your response, I appreciate it.

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      • #4
        Using TB's parms - 0.30 Qts, 0.81cf Vas; 0.70cf looks good tuned to 33Hz w/a 1"x10.5" slot that's 3 feet long. F3 = 30Hz.
        OTOH, if the Vas is 0.30cf, then that same box still (technically) has an F3 of 30, but w/over 3dB of "ripple" (run your own sim).
        It might SOUND like its F3 was more like 50-60Hz. If you low pass THAT sub @ 50, it ends up w/a very narrow spike right at Fb (33) which would sound pretty much like "one-note-bass".

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        • #5
          Suggest you read this thread.

          Project #2: The 'Tenacious Bass 6' and 'Tenacious Bass 8' Subwoofers - Techtalk Speaker Building, Audio, Video Discussion Forum

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          • #6
            I've done a little more exploring via google/forums etc. While I realize the tenacious guy abandoned his slotted design, and I get that it is challenging to design, that the TS parameters *may be wrong, etc. But I'm feeling challenged and inspired to make a slotted design work with this driver. I wish the tenacious guy would've given his measurements (box, port), so I can play with things a bit and get at least a quantitative frame of reference for his subjectively described problems. As it is, I designed a 0.836 ft^3 box. A 1 X 10.5 X 41 inch port. Three folds from the bottom, using the sides and back. It will be external dimensions 18h X 12w X 14d. I have the dayton 250 watt plate amp, and it has a high pass at 20hz, which reduces max port velocity at max excursion at a little over 20 m/s. I have the box tuned to 28. I hear that winisd will make a slotted port slightly longer than needed for a given tune (when you use the walls as the port) so idk maybe it will be tuned to 27. If it's 26 or 29, I won't be able to discern anyway, I don't think. It wasn't terribly expensive for the supplies to build this box, so we'll just see how it turns out. Any feedback is welcomed and appreciated, even if you'll say it's a waste of time. Just be nice Cheers.

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            • #7
              The "Tenacious guy" is Tom Zarbo, I'm pretty sure he would help you if you asked.

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              • #8
                I just tried to write him a message, doesn't seem like I'm able to contact members via personal message, idk. I have a message to give him, questions to ask, etc. do you have any insight about how I can message people? Maybe I'm not seasoned enough? haha. I really like his PR designs, but like I said I'm feeling challenged and inspired to make this work. Thanks for your reply.

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                • #9
                  You SHOULD be able to go to "Messages" (screen top) and "Send New Message" - send to "tomzarbo"

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                  • #10
                    Hey DIYaudio,
                    welcome to the forum. I'll be happy to answer any questions I can. Let me try to pm you now, maybe that will work. I'm in the middle of trying to put a crossover together for another project, so it may take a little bit for me to get to my main computer to really offer any real help.
                    TomZ
                    *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
                    *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

                    *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

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                    • #11
                      Thanks Chris. Tom..... I'm happy you wrote me! My attempt last night failed but I saved what I wanted to write you. I didn't mean disrespect by calling you the "tenacious guy," it was an easy reference since I didn't remember your name from your post. I read through your entire post about the tenacious subs, impressive builds. I'm very curious to hear what you have to say about the slotted design you tried. I have the wood for the project but can't cut it for 2 weeks, so I have time to wait and figure out a final design, if it will change from what I have now. Here is my message from last night:

                      "Hi Tom. I am trying to build a slotted port design for the tang band w8-740p. I wrote a forum post and someone sent me the link of your 8 and 6 designs. I am very curious about your slot port and box dimensions. I am stubborn and trying to make it work. I have a design that I discuss above (few threads ago). Comments or suggestions you have would be greatly appreciated. Your subs are great, I have respect for your work, I just just don't want to go the PR route.....yet. I think I can get this to work for my preferred volume level (not max or close to it) and a little bit of planning. My current design has a max port velocity of 20 m/s at my tuning (28hz) @ 250 watts (dayton 250). It's actually a challenge to me to get this sub to work, so I really want to try. It's such a great sub, I want to see one slotted ported design work, or at least come close, ha"

                      Yeah any advice or suggestions you have will be greatly appreciated. In particular your port and box dimensions would be priceless for me at this point. Cheers!

                      Comment


                      • #12
                        I see I generated little enthusiasm with this, haha. After feedback I decided to go with a 1.5 X 10.5 X 43 inch slotted port and a 0.836 ft^3 cabin design tuned to 31hz. In winisd the max port velocity is 18 m/s. The transient function has a small hump at tuning but nothing insane that I feel will be hard to listen to for what I want. I have a 20hz high pass on my amp, so that helps. I'm gonna flare the port on the opening on both ends. I'm 80% music, 20% movies in a small room where I can play a high volume. I'll report back on how it turned out. Cheers!

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                        • #13
                          I made the subwoofer last weekend. I used .75 mdf. The outside dimensions were 18.75H X 12W X 14D (in). I tuned the slot port to 31hz, and the length was 41 inches, with a cross section of 1.25in X 10.5. The main speaker cabin was 0.836 ft^3. Here are some thoughts on the final product. There is no chuffing at any volume with any music/movies I've tested it with. The max port velocity was modeled at around 18 m/s with the 20hz high pass that is a inherent part of the dayton audio 250 watt amp from parts express. When I put my hand over the slot I can feel a little bit of air movement, but not much. Maybe I designed it too paranoid of chuffing based on all my research online, idk. I also rounded the bends of my slots with sandpaper, first course then finer. I also sanded the slot panes too. I wanted to reduce friction as much as possible without a huge amount of work. The size of the box is quite large for only housing an 8 inch woofer, but that isnt too much of a bother for me. I made the dimensions so that if I get bored with the tang 8 I can throw in a ten inch sub that might coincidentally model well with this box in winisd. The sound...... well it exceeded my expectations. It shakes the room. The room is quite small, so that probably helps. I'm extremely happy with it and consider this a success. I'll probably post this in the project gallery because I feel it will help some people that want to do a ported design with this driver. It sounds wonderful with the wide range of music I listen to. Subjective description I guess. I'll attach a few photos. I haven't finished the outside. I'll plug the countersunk holes with a mixture of glue and saw dust. Sand well, then spray paint a few times. Still deciding between gloss, semi, satin, etc. Not such a big fan of anything but black for subs. Fun project. Powerful room shaking sub, zero chuffing, fairly large box for an 8, not as one-note-wondery as I thought. So I'm very happy with it and will likely keep it around for quite while before I get the itch for something else. Now I'm trying to decide what mains I want to pair with it since my audioengine A2+ don't seem to compliment such a big sound. I'm considering the Edifier R2000DB's. Any advice on a not too expensive pair of bookshelves to go with this would be welcomed. Thanks for reading.
                          Last edited by DIYaudio; 02-23-2019, 04:14 PM.

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                          • #14
                            Nice Job!
                            Three comments:
                            (1) Do you have a router and circle jig so that you could flush mount the driver? It won't matter for sound but looks nicer
                            (2) You might want to add a window brace or just a dowel brace in the middle.
                            (3) You will have a difficult time hiding the seams of the MDF. You can sand it down to 600 grit smooth, prime, and have 8 coats of paint, and they will still be there. There are several threads here and other forums on ways to hide the seams. One sure way is to use some kind of texture (textured paint or duratex) but you can try wood-glue coat or other methods.

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                            • #15
                              Don't have a router or circle jig, that would look nice, will consider that. Do you think a brace would change things? The speaker cabinet is so small and my cuts were nearly perfect and I used 2 inch screws every few inches. I thought maybe I could get away with not using one. Thanks for the info on the seams of the mdf. I'll check them all out. The cuts were so good and I'm so happy with the build, it would be nice to have it seamless. Thanks a lot I appreciate it. This thing slams way better than I expected, great driver.

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