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Dark Thunder Bookshelf Speakers

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  • Dark Thunder Bookshelf Speakers

    Hi guys! Just wanted to show off my first speaker build. I basically wanted a pair of speakers that could fit on my desk; but still give a nice deep bass response, below 40hz, without need of a subwoofer (I have no room under the desk). So I knocked these together! They use the Tang Band W5-1138SMF and the Dayton Audio DC28F-8 crossed at about 1.4 kHz, in a 6Lish box tuned to about 35hz. Overall quite happy with them! The finish on them isn't the best, I had to rush to get them finished because of uni, but sound wise they're fantastic! Nice flat, natural sound, and an easy deep response down to 35hz ish.

    You can checkout more pictures and stuff here: http://projectgallery.parts-express....helf-speakers/

    (there is foam insulation in there dw, I just didn't have any pictures of it like that)
    Last edited by Anonymousish; 10-14-2018, 03:36 PM.

  • #2
    Those DO seem nice. Ordinarily if I saw a "noobie" crossing the Silky down at 1.4k, I'd say "Oh boy!", but a sim shows that the -070 is down better than -25dB at Fs, so I bet they're not really complaining.
    A sim also shows a Z-min (near 800Hz) of 2.1 ohms. Pretty hard load (unless you're using an auto amp).
    Is that slot about 1/2" x 4-1/2" by 19" long or so? Did you run a rear cup right through the slot?

    I also see there's no BSC involved?

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    • #3
      Chris Roemer Yeah I knew I was taking a risk trying to cross that low for the tweeter and high for the woofer, I originally wanted to do a 3-way for that reason, but it was too much cost wise so I decided to see if I could make it work. And I was pleasantly suprised that they seemed so comfortable with it! It boxsim simulation said it should work so I hoped for the best and stuck with it like that. After listening to it for many hours I can't hear anything that would suggest its having a hard time in anyway, so I think I got away with it.

      As for the amp, I'm using a Denon PMA-520AE. I was slightly concerned that the Z min may be too low, but I figured that I was never gonna crank them that high anyway as anything higher than 85 db I normally find slightly painful. And the amp seems perfectly comfortable driving them at that sort of level for a long time, it barely gets warm really.

      The port is very very long yeah, the opening is 12mm x 136mm (0.47" x 5.28" ish), with a length 70 cm or (27.56"). Which puts the tuning at 30 ish hz, but I forgot to factor in the volume taken up by the foam so I think the volume is more like 6L. Making it tuned to 35 hz. (I'll change the wording in the post, just realised I've put down 7L). I also don't seem to get any noticable resonances from the port which I'm happy about, I did wonder if such a long port would go all organ harmonics on me but it hasn't. According the simulation this would make it roll off much sooner than it does irl, but I'm thinking the room is really helping with the bass extension here. Either that or the woofer just has far more reach than the specs say it should! I was going to use an eq anyway to get rid of a few room modes, and thought I'd just boost the low end a bit to get it flat at the same time. But I haven't needed to do any boosting so yeah.

      The wiring was a bit of a chore not going to lie! In hindsight I really should have wired the terminals before building the port, but I forgot to do so. The height of the port is only 12mm making it pretty difficult to wire up in the normal fashion. So I ended up wrapping a loop of the wire around the threaded portion of the binding post, and then using the nut that would normally go on the other side of the wood to hold it on, to then press the wire against the part that would normally go against the wood on the outside. This ensured that the wire was firmly attached to the binding post for a good connection. Then the wire was threaded through the hole for the binding post, with the threaded bit of the binding post; the hole was made bigger for both things to fit side by side. The exterior part of the hole was mad significantly larger too to accommodate the nut and the wire, allowing the part of the exterior part of the binding post to sit flush on the mdf as per normal. This was then just glued into place with a glue gun, and voila, it looks just as it would if done normally. Then little grooves were made for the positive and negative wires to sit on the bit of mdf that made the back portion of the port; which allowed them to sit flush inside the bit so the side panel would go on no problems. It did mean that port is partially blocked by the two wires there, but I did make sure to space them out as much as could to make the disturbance to the airflow as little as possible, plus they didn't take up that much room so it was alright in the end.

      And nope theres no BSC involved, didn't want the soldering hassle or the extra cost, and figured that the W5-1138SMF's are naturally bass heavy anyway. Also boxsim does (sort of) factor in the baffle's effect on the sound, and that looked fine when I simulated it so I didn't bother. Which is good as it still has a decent flat response down to 35 hz or so! So none was needed apparently.

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      • #4
        Huh... I looked on the website and it was going for $150, and it was on sale for $100 on amazon. I guess the price has gone back up to the normal price... And the MSRP looks like it increased too... Sorry for the slight misinformation. I still think these speakers are great, but they are pricey.
        https://inro.in/lucky-patcher/
        https://inro.in/9apps/
        https://inro.in/vidmate/
        Last edited by ikama23; 11-11-2018, 01:24 PM.

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