About 9-10 years ago I build a 2-way T-line speaker set. They are a quite bad design, but I did put a lot of effort into building a nice looking, stiff and heavy box.
I did some calculations for the bass-mid driver and if I had a bass reflex with the same volume of box, the result should be really quite good.
There are a few things I am wondering about and would like your thoughts on.
1. If I simply close the end of the T-line, and put a vent there instead, will the enclosure behave like a bass reflex? Or will it behave differently. The cross section of the T-line is about 250cm2, which is much much bigger than any vent cross section. The total volume of the box is about 90 litres.
2. Would the placement of the vent matter? It will be most easy for me to add it to the new piece of wood I will close the end of the T-line with, but I could make a hole in another section if that would be a better choice.
3. For the ideal tuning of the box, the first harmonic of my vent will be at around 1kHz, while the crossover is a 4th order butterworth at 1.5kHz. I can't really find what happens if I were to implement that design. I assume it is not great, but I would like to confirm that before I make the bass extension (slightly) worse by tuning the box a little higher with a shorter port. I am already minimizing the diameter of the port while keeping air speed in check at the maximum volume level I intend to actually use.
Thanks for your input.
I did some calculations for the bass-mid driver and if I had a bass reflex with the same volume of box, the result should be really quite good.
There are a few things I am wondering about and would like your thoughts on.
1. If I simply close the end of the T-line, and put a vent there instead, will the enclosure behave like a bass reflex? Or will it behave differently. The cross section of the T-line is about 250cm2, which is much much bigger than any vent cross section. The total volume of the box is about 90 litres.
2. Would the placement of the vent matter? It will be most easy for me to add it to the new piece of wood I will close the end of the T-line with, but I could make a hole in another section if that would be a better choice.
3. For the ideal tuning of the box, the first harmonic of my vent will be at around 1kHz, while the crossover is a 4th order butterworth at 1.5kHz. I can't really find what happens if I were to implement that design. I assume it is not great, but I would like to confirm that before I make the bass extension (slightly) worse by tuning the box a little higher with a shorter port. I am already minimizing the diameter of the port while keeping air speed in check at the maximum volume level I intend to actually use.
Thanks for your input.
Considering I made the huge mistake of not saving my work, I don't have any exact drawings. This is the approximate internal shape. Outside WxDxH 310x400x2300mm
The bass-mid driver is the SB23NACS45-4 ( https://www.speakerland.nl/files/8in-sb23nacs45-4.pdf )
I can't find the exact model of the tweeter, but I don't intend on modifying that anyway.
My current intention is putting the seal and vent where I marked it in yellow, as then it is out of sight and doesn't impact the look of the speaker at all.
I forgot to mention that I matched the length of the T-line with the Fs of the driver (27Hz) so it is about 3170mm.
And maybe the quite bad is a bit of an understatement. I'm well aware it's not anything like how a proper TL should be designed.
If I take out the driver I could add some holes in the internal walls with a hole saw, could that turn the response to change to a bass reflex, or does anyone have any suggestions to salvage this?
(Other than just building an entire new box)
And maybe the quite bad is a bit of an understatement. I'm well aware it's not anything like how a proper TL should be designed.
If I take out the driver I could add some holes in the internal walls with a hole saw, could that turn the response to change to a bass reflex, or does anyone have any suggestions to salvage this?
(Other than just building an entire new box)
Might be easier just to start over, with your existing drivers in a BR enclosure.
jeff
jeff
Choosing a line's 1/4-wavelength resonant frequency based on a driver's Fs also depends on the driver's Qts for a maximally flat overall response shape. If Qts is equal or close to 0.40, then its Fs is what would be appropriate. If, however, Qts is more than a bit lower than 0.40, then you would need a higher tuning frequency, and if Qts is more than a bit higher than 0.40, then you need a lower tuning frequency.
Paul
Yeah, I'm a little affraid that might be the case.
@pkitt, thx for the advise, but I think I'll stay away from T-lines for now. Maybe if I have some succes with less complex designs, I might try again.
If you like the product you have, rather than start over, just cut the back off/out. Then use a hole saw to swiss cheese the dividers that made up the line. They'll end up as braces, and you'll only have to make a new rear panel. If you leave a bit when you cutout the back, you'd also have a lip to make your new back removable.
@Bisdriver, that is a great idea. Finishing a box this size to look nice enough for a living room is a bit of work, so I would rather not do that again.
Im not sure about making the back removable, as than I need some type of gasket to seal it against the lip. Need to think on that if it would be worth the effort.
I hope I wil never have to open the box again after such a large remodeling.
Im not sure about making the back removable, as than I need some type of gasket to seal it against the lip. Need to think on that if it would be worth the effort.
I hope I wil never have to open the box again after such a large remodeling.
There's tons of "speaker sealing tape" on amazon. It's just really thin weather striping foam. Easy gasket.
Or use something like "Blu Tack" which you can also get in black.
Or use something like "Blu Tack" which you can also get in black.