First, the attachment in 19 is a little off. I pulled in a table of data from Parts Express but when I went to one of the drivers, that driver page was different than the table. The updated table is below.
There really is no specific goal, just designing the smallest taper T-line that has a f3 of 40 hz. There are two speakers on the table (bright green in the 2nd column) that I think will meet the 40 hz with some circuitry. And not a lot of volume either - from 250 cu in (about 4 liters) line volume to 640 cu in (about 11 liters.) That will make a pretty small box. See the past posts on how it might be done.
scott
There really is no specific goal, just designing the smallest taper T-line that has a f3 of 40 hz. There are two speakers on the table (bright green in the 2nd column) that I think will meet the 40 hz with some circuitry. And not a lot of volume either - from 250 cu in (about 4 liters) line volume to 640 cu in (about 11 liters.) That will make a pretty small box. See the past posts on how it might be done.
scott
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Yes, that will work and I have built several of them but I think a transmission line system will produce a better "music" sound so I would like to focus on a T-line with experts on this forum - Maybe we can come up with a very innovated compact solution. I have put forward some of those possible solutions in the previous posts but I'm sure, no I'm positive that there will be better ones if we put our heads together.
I'm working on developing the concept for an adjustable testing T-line system - maybe it will be ready this weekend
scott
I'm working on developing the concept for an adjustable testing T-line system - maybe it will be ready this weekend
scott
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Great! They do it with a 6.5" driver. I knew it was possible to get under 40 with a T-Line that is less than 1200 cu in. I think we can do it less than that with a 3 to 4" driver because the line volume will be less with a smaller driver. The difference is the SPL and since we are going for near field, than that isn't going to hold us back.
Their smaller one about (700 cu in) has a 5.5" driver, with a line length of 66" for a 46hz.
But we should be able to do it even smaller with a more complicated innovative DIY design that commercially would not make sense.
Ideas??
scott
Their smaller one about (700 cu in) has a 5.5" driver, with a line length of 66" for a 46hz.
But we should be able to do it even smaller with a more complicated innovative DIY design that commercially would not make sense.
Ideas??
scott
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Not exactly small.
Dimensions:H 410mm 16.1” x W 192mm 7.6” x D 373mm 14.7” - Incl. binding posts (+9mm grille)
(ie 1800 in^3)
dave
Yes, not as small as I would want it but the size also depends on the size of the driver (among other things.) I think with a 3 or 4" driver it will be much smaller. Their 5.5 inch driver enclosure has an internal vol of around 700 vs the internal vol of about 1300 for the one above. That seems to have a trend so maybe a 4" internal volume for a near field tapered enclosure might get to 500 or so.
scott
scott
Maybe not because I used your formula in post 15, then looked up many parts express 3 and 4 inch drivers (result in post 22) and found one full range one that got down to 39 with several others around 45. I have a TB w3-2108 3" that has a fs of 45 so that will definitely work but it is not full range -
Do you think it is possible to hit 40? Remember, spl not an issue because of near field.
Do you think it is possible to hit 40? Remember, spl not an issue because of near field.
https://www.parts-express.com/pedocs/specs/264-953s.pdf
Used it sealed with an LT to bring the bass lower?
Used it sealed with an LT to bring the bass lower?
We looked at a lot of small drivers when we were working on the TL/stand/helper woofer for the uFonken — we wanted very good bass performance. We ended up using the Peerless 830870. Sims show an anechoic F10 of ~42 Hz and a response shape well suited to roon gain. In a small room you probably could hit 40 but i wouldn’t call it small.
Playing these at diyFEST people were very impressed with their bass performance.
dave
Playing these at diyFEST people were very impressed with their bass performance.
dave
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OK, that is good to know that formula might be too optimistic. However, I have read that a properly designed T-line has the possibility of reaching a 1/2 to a full octave lower than the Fs. If that is so, this goal might be able to be reached since a few of those 3 and 4 inchers in post 22, have a 55 to 65 fs and that fits into that 40 hz goal.
This thread is getting some attention so at the risk of being redundant, let me summarize the end goal:
In a past post (#15) there is an attachment of several drivers that come close to meeting the driver goal.
What do you’ll say experts, lets give it a shot. It is a challenge, it has a low cost attached to it, and it will be innovative. All we need to do is to have a robust discussion of which driver we want to use, how to design the enclosure to be efficient, and then build a few to test. If we stick to a $25 driver and a small prototype enclosure (maybe a pipe, foamcore, foam, or ??) than it will be fast, fun and inexpensive.
If you want to go down this path, sign on and after we get a group, we will start the discussion.
This thread is getting some attention so at the risk of being redundant, let me summarize the end goal:
- Pulling together a bunch of transmission line experts to design and build the smallest portable, tapered T-line (ML-Tqwt) that has a F3 of 40hz with a 3 or 4” driver costing under $25 in a near field environment using innovative ideas that would not be financially feasible for a commercial company to do, like making the T-Line a spiral, or helicoid, using a 3d printer enclosure or ???? Ideas welcomed.
- Use an onboard BSC/EQ/bass limit circuit going into an onboard amp therefore eliminating any passive components.
In a past post (#15) there is an attachment of several drivers that come close to meeting the driver goal.
What do you’ll say experts, lets give it a shot. It is a challenge, it has a low cost attached to it, and it will be innovative. All we need to do is to have a robust discussion of which driver we want to use, how to design the enclosure to be efficient, and then build a few to test. If we stick to a $25 driver and a small prototype enclosure (maybe a pipe, foamcore, foam, or ??) than it will be fast, fun and inexpensive.
If you want to go down this path, sign on and after we get a group, we will start the discussion.
To Planet10,
Thanks for all your responses. I have an idea of building an adjustable transmission line that will allow for fast changing of the line length, the volume, the taper and the drivers so different variations can be tested. I don't want to post it if you don't think it is feasible. Is there a way I can send it to you?
thanks
scott
Thanks for all your responses. I have an idea of building an adjustable transmission line that will allow for fast changing of the line length, the volume, the taper and the drivers so different variations can be tested. I don't want to post it if you don't think it is feasible. Is there a way I can send it to you?
thanks
scott
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