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Old 8th July 2014, 07:34 PM   #1
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Default tapered tube FR enclosure (Nautilus)

hello,

i was thinking about this enclosure for 6" fullranger:

"straight Nautilus"

straight tapered tube about 60" long.
driver mounted on wide end, 1" opening on other.

but prior to me making it:
has anyone tried this and how does this box model?
like a transmission line?

thanks,
herman
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Old 8th July 2014, 07:51 PM   #2
IG81 is offline IG81  Canada
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There was a thread some time back about a foam-core build called "Nautaloss".

Yes, it will model as a transmission line. If the terminus is closed, it will be a -wavelength resonator. These are usually stuffed the whole length in order to absorb the back wave. It should perform roughly like a sealed enclosure, possibly cleaner midrange, never heard one though. If you have the terminus open, it will be a -wavelength resonator, probably not what you want here and is a whole different design approach. If you have to leave the terminus open, use progressively denser stuffing down the line and stuff the opening as well. Probably best to use a driver with low-ish Fs (<60Hz )and medium Qts (0.45-0.7).
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Old 8th July 2014, 09:03 PM   #3
xrk971 is online now xrk971  United States
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Yes, there is the uncoiled Nautaloss or 'dagger' sealed TL. It is very easy to make with 5 pieces of wood and stuffed progressively. It behaves like an infinite baffle. You are far better off to coil it up into a spiral to save space and it is not hard to make with foam core. It is one of the best sounding speakers I have built - very neutral flat response. Use the Vifa TC9FD driver - doesn't get much smoother response wise or lower in distortion even though priced very low.
The Nautaloss Ref Monitor

Here is what it is capable of:
Click the image to open in full size.

Needs a sub woofer though as sealed alignments don't go much below 150 Hz. In the same thread there is also a Nautaloss subwoofer.
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Old 8th July 2014, 10:54 PM   #4
GM is offline GM  United States
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Or start with a > 1.0 Qt driver.........

GM
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Old 9th July 2014, 12:34 PM   #5
IG81 is offline IG81  Canada
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Quote:
Originally Posted by GM View Post
Or start with a > 1.0 Qt driver.........

GM
I do have a pair of pro 6.5" midbass with higher than expected Kms/Fs/Qts, the latter two coming in ~25Hz and 0.35 too high respectively at ~86Hz and ~0.9. :/ Such an enclosure might be saner than a whole bunch of vented atrocities I've gone nuts trying to simulate with decent results anyway. I'd likely lose the fairly solid ~60Hz extension I was going for with the factory data.

Them big'ol Isophon 8"x12" coax I got might be neat in there with Fs~60Hz and Qt~0.9.
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Old 9th July 2014, 01:01 PM   #6
GM is offline GM  United States
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Brand, model? Prosound drivers usually adhere to a much lower Fs shift than consumer products, so that once exercised at high power will be 'close enough' to advertised. Maybe yours just need to be stuck in small sealed cabs and 'lit up' with an electric guitar.

GM
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Old 9th July 2014, 02:09 PM   #7
IG81 is offline IG81  Canada
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Quote:
Originally Posted by GM View Post
Brand, model? Prosound drivers usually adhere to a much lower Fs shift than consumer products, so that once exercised at high power will be 'close enough' to advertised. Maybe yours just need to be stuck in small sealed cabs and 'lit up' with an electric guitar.

GM
Faital 6FE100. I had a thread over in multi-way where I initially had a few measurement issues. After sorting these out, it basically seems Cms is about half what it should be and the rest of the data naturally follows suit.

Factory data:

Click the image to open in full size.

2008 Voice Coil / Vance Dickason data:

Click the image to open in full size.

Click the image to open in full size.

Data I measured: (~2V drive level)

Fs = 86.19 Hz
Re = 5.60 ohms[dc]
Le = 251.23 uH
Qt = 0.92
Qes = 1.00
Qms = 11.00
Mms = 14.39 grams
Rms = 0.707299 kg/s
Cms = 0.000239 m/N
Vas = 6.86 liters
Sd= 142.93 cm^2
Bl = 6.585896 Tm
ETA = 0.42 %
Lp(2.83V/1m) = 89.84 dB

Added Mass Method:
Added mass = 37.00 grams
Diameter= 13.49 cm

I pushed some ~20Hz-30Hz sine at ~12V into them for a few hours with zero measured change after the motor had cooled.

The upside to that low Cms is high excursion-limited power handling. I don't see how Fs could be lower if I measured at higher excursion since the suspension only gets stiffer and things would start to be non-linear anyway. Not sure I'll ever drive them hard enough in everyday use to loosen it up too. Maybe I'll give'em some more time on the "burner" and hope for the best.

I got some half-decent simulated results with rather large stuffed TL's, bu the aim was <30L and fair 50Hz-60Hz extension with this project. I'm thinking ~20L sealed or lossy spiral with their backs to a wall, give up the bass and be done with it. Should be decent enough for shop speakers.
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Old 9th July 2014, 03:10 PM   #8
IG81 is offline IG81  Canada
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noviygera,

Did you have a specific driver in mind?

GM,

The lossy spiral looks fair enough as far as I can simulate this in HR, but I just remembered my best result so far from a few days ago. It's a 48" long ~40L ML-Voigt (expanding pipe) with driver tap ~42% (20") and a ton of stuffing in the whole length. Damps the Z nicely to ~ a single (upper) low-magnitude peak, gives a much reduced ~100Hz hump and gets fair extension. I have no practical experience with such a combo though, can only sim and guess how it'd turn out.
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Old 9th July 2014, 05:18 PM   #9
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Default 6.5 inch l.cao

L.cao f6:
image.jpg


Not planning on spiral. Just a tapered tube or long pyramid (four sides plywood).
60 inches long transmission line, so the tapered end is open. Is it too short?
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Old 9th July 2014, 06:30 PM   #10
IG81 is offline IG81  Canada
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With the above specs, 45" long, going from 8"x8" tapering down to 2"x2" and fully stuffed with ~250g of polyfill looks good in simulation. Net volume is ~19L if I use a Conical flare, close to what you'd get with a pyramid-style build, or ~24L if I use a Parabolic flare, what you'd get if you built a "wedge" with two parallel sides, the other two with a linear taper. You'd have to make the open-end 8" x 0.5" in this case.

This is not the same thing as a Nautilus at this point, as the terminus should be closed and the rear-wave internally absorbed.
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