Introduction: Modified TQWT Speaker
I started this speaker set about a year ago and only managed to finish it a couple weeks ago (working on my hobby over weekends does take time...)
The idea was to use make a 2-way, TQWT speaker enclosure with a Fr of 42Hz. crossover would have been at 2200Hz. I started with a 5" Mission mid range driver and a Dayton Audio DC28F-8 1-1/8" Silk Dome Tweeter.
The baffle I made by glueing 2x 16mm thick MDF boards together. Routed the holes for the speakers and started building the box. The inner "channel" I calculated using a online calculator and everything was sorted...
Step 1: The Tube
The tube was calculated to 1,94m for the 42Hz. The mission driver in theory was supposed to be able to extend to this frequency from the ts parameters I measured. Up until this stage I was expecting a lot of great sound from this speaker. I rounded the corners with a chunk of MDF I made by glue'ing pieces together and finished off on the big belt sander. That came out pretty well. The rounding of the corners firstly stops "standing waves" and secondly helps smooth air flow in the tube.
I fitted a driver, sealed off the tweeter hole and fitted a side panel so I could listen to the Mission driver. I was dissapointed. Not happy with the bass at ALL - rookie mistake. So the problem was the mission driver could barely go to 65Hz nevermind 42Hz. I needed another solution.
Step 2: 2-way Becomes a 3-way
I had a pair of older 8" drivers in a cupboard gathering dust. So the solution was to add the 8" drivers to the side panel. I routed a 8" hole, removed a part of the tube and stuffed it all with pillow filler and some bumpy foam I had. Where the driver is situated, the tube becomes larger to the top but gets narrower to the bottom. Later on I even reduced the last bit of the tube to only 15mm. This helped with the punchiness of the bass but later more on that.
I also added a small piece of railway sleeper to the bottom of the enclosure just to have something to extra to look at
I also added 4x neodymium magnets to the front baffles so I could have speaker grills magnetically coupled to the enclosure and not have any mounting holes for grill pegs.
I eventually finished the enclosure and started on the cross-over. This took time to get right. I tuned the cross-over to 2300Hz for tweeter to mid and the mid to bass at 300Hz. And when measured the low bass came to 32Hz!!! NOW I was happy with the sound.
Step 3: Veneer and Finishing
I used real wood veneer for the finish. American Walnut was my choice and it came out really good. This was my first time I worked with veneers. I did have issues to start with and here's a couple of pointers from what I have learned.
- Try not to veneer after you built the enclosure, you cannot clamp in the middle of the enclosure properly and will have a wavy result.
- Ensure you can clamp in the middle of the veneer....
- DO NOT sand it with a machine that will remove material very quickly like a rotating orbital sander (rookie...). Hand sanding is the way and then also use a fine grit paper...
I built the speaker grill out of 5mm Perspex (plexi glass) and covered with grill cloth and a filter media (fitted between the cloth and perspex) to soften the edges on the perspex. Magnets fitted and I was nearly done.
All that was left was the painting with a polyurethane varnish. And as you can see, that came out very well
Step 4: Setting Up
Finally, everything fitted. The speakers came out very nicely. After spending many hours on them I am happy with how they turned out.
The setup has to be with the bass drivers facing away from each other else the bass gets cancelled out when facing each other.
They measure 200m wide, 500mm deep and 450mm high. The bass goes to 32Hz and the change over between the drivers cannot be heard. It is difficult to describe the sound but I will attempt it...
It has big presence, they were built for main speakers in my setup which I use for both music and movies. In movie mode they do not get fed much base the sub takes care of that. In music they take over completely. The bass has punch but is not over powering, the mids sound full and the highs are clear as a bell even at higher volume. At excessive volume, they shine
I am happy to have built these, they look good and sound great. I even have wife approval of them :)
Participated in the
Audio Challenge 2020