Inspired by xrk971 https://www.diyaudio.com/forums/full-range/247598-nautaloss-ref-monitor-68.html, I'm thinking of building the midbass section in my 4-way active sytem along those lines. The section uses twin 10" midbasses, so the box will be rather large (about 30" deep) and the effort significant so this is to ask for feedback: am I over complicating things? Is this a good idea?
The section will play 60 to 400 Hz approx. It would be a spiral sealed transmission line. It would need to be about 3 feet long and, given the dimensions I can afford to use for the box, the spiral would have about 1 to 2 rounds. The main goal is to absorb the backwave in the TL. From initial calcs the inside volume would be rather large leading to a Qtc in the 0.4 to 0.5 range.
I haven't seen other designs following this concept beyond the Nautaloss, which dates from Dec-13 so more than enough time for knowledgeable guys to pursue a good idea, so I'm wondering what it is I'm missing.
Looking forward for your feedback!
The section will play 60 to 400 Hz approx. It would be a spiral sealed transmission line. It would need to be about 3 feet long and, given the dimensions I can afford to use for the box, the spiral would have about 1 to 2 rounds. The main goal is to absorb the backwave in the TL. From initial calcs the inside volume would be rather large leading to a Qtc in the 0.4 to 0.5 range.
I haven't seen other designs following this concept beyond the Nautaloss, which dates from Dec-13 so more than enough time for knowledgeable guys to pursue a good idea, so I'm wondering what it is I'm missing.
Looking forward for your feedback!
I've been using a similar tapered tube for midrange for years. Because I can't have a tube sticking out the rear, I typically fold it into an inverted J shape and approximated the exponential taper in straight sections. Works well.
Depending upon the size of the box and available dimensions a folded rectangular section could be made. Not sure if making the spiral taper would make much difference once lined and stuffed. But if you're feeling masochistic...
Could I please make a request? Instead of posting thread pages in links, click on the post number in the top RH corner and post that, so that no matter how many posts/page users have set, we can all see what you're linking to. I see the last page, #17 for me.
Depending upon the size of the box and available dimensions a folded rectangular section could be made. Not sure if making the spiral taper would make much difference once lined and stuffed. But if you're feeling masochistic...
Could I please make a request? Instead of posting thread pages in links, click on the post number in the top RH corner and post that, so that no matter how many posts/page users have set, we can all see what you're linking to. I see the last page, #17 for me.
Thank you. I wasn't aware the exact post could be referred to. Great!
Yes, rectangular cross section spiral is what I had in mind.
Any reason why you don't use it on the midbass?
I generally don't have the space as I seldom use small drivers for midbass; a 15" is the average.
Here's a drafted design, for feedback
Work has been super busy and I suspended this but I'm now back on it.
Attached is a schematic of what I'm thinking. BTW, how do I attach an image inside the post? The "Insert image" button above asks for a URL, but my image is a jpg in my hard drive...
Anyway, the midbass is sealed, with two 10" drives. Each drive with a tapered tube of rectangular section. Is not drawn, but the tapered tube tapers in height and towards the external wall of the box, so one tube starts in the bottom and tapers towards the top of the box, while the other starts at the top and tapers towards the bottom. The line will be stuffed, likely with fiberglass, with varying density getting denser towards the end of the line.
The box housing the tapered tubes will have MDF walls (or plywood), and the inside would be translaminated particle board where I'll carve out the tapered tubes.
Externally, I want to have a wide front panel and rounded edges, tapering to a narrower back panel (aesthetics), so the space on the sides in between the rectangular box housing the tapered tubes and the outside shell would be filled with sand.
The most important question for me: will this line, 93cm long, work well in absorbing the back wave for these midbasses playing 60 to 400Hz?
Work has been super busy and I suspended this but I'm now back on it.
Attached is a schematic of what I'm thinking. BTW, how do I attach an image inside the post? The "Insert image" button above asks for a URL, but my image is a jpg in my hard drive...
Anyway, the midbass is sealed, with two 10" drives. Each drive with a tapered tube of rectangular section. Is not drawn, but the tapered tube tapers in height and towards the external wall of the box, so one tube starts in the bottom and tapers towards the top of the box, while the other starts at the top and tapers towards the bottom. The line will be stuffed, likely with fiberglass, with varying density getting denser towards the end of the line.
The box housing the tapered tubes will have MDF walls (or plywood), and the inside would be translaminated particle board where I'll carve out the tapered tubes.
Externally, I want to have a wide front panel and rounded edges, tapering to a narrower back panel (aesthetics), so the space on the sides in between the rectangular box housing the tapered tubes and the outside shell would be filled with sand.
The most important question for me: will this line, 93cm long, work well in absorbing the back wave for these midbasses playing 60 to 400Hz?
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