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Old 22nd December 2013, 04:40 PM   #51
xrk971 is offline xrk971  United States
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Quote:
Anyone know from memory if B&W specifically patented the spiral chamber absorption technique?
The closest thing I could find was B&W's disc-shaped radial spiral back absorber: US7201252 B2 (2007)

https://docs.google.com/viewer?url=p.../US7201252.pdf

Click the image to open in full size.

Nothing for the 'Nautilus' proper - for the spiral axis to be perpendicular to the driver cone axis. In fact, the claims (1) and (2) are very specific about the spiral is transverse to the speaker axis.

Quote:
Claims: 1. A loudspeaker system comprising a loudspeaker drive unit having a front and a rear, said drive unit including a sound-producing diaphragm having front and rear faces, and a rear sound absorption system located on the rear of said loudspeaker drive unit on a sound path running rearwardly from the rear face of said diaphragm to the said rear sound absorption system, said rear sound absorption unit comprising a multiplicity of sound-absorbing tubes, operative to create acoustic loss, running in a spiral configuration.
2. A loudspeaker system as claimed in claim 1, wherein the tubes run in a spiral configuration transverse to the axis of said loudspeaker drive unit.
Which leads me to believe that there either exists a patent by someone else or it is obvious to one skilled in the art of speaker building that they could not claim it. But I could not find this other patent, so I am guessing that the Nautilus shaped 'snail' spiral and its orientation to a driver cone is (obvious) and in the public domain.

Please correct me if I am wrong about this...

Last edited by xrk971; 22nd December 2013 at 04:44 PM.
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Old 22nd December 2013, 07:37 PM   #52
xrk971 is offline xrk971  United States
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Default Bass Nautaloss with Dual 6.5in Drivers - build #5 - Finished!

After the baffle was glued in place, I installed the terminal cup and wiring, then started to add stuffing. The stuffing is dense at the closed end and progressively gets looser as I go towards the drivers, stopping at about 80% of the way. I heard that the spiral effectively absorbs the back wave with a minimal of stuffing near the drivers - which helps to keep the sound more 'open'. Don't know if that is true or not but if I need to add more it can be done thru driver cutouts. Finally, I capped it off with a sheet of black paper-faced foam core (it was flatter than the white stuff which has waviness to it) and will give it a more interesting look. I used a combination of PVA (95%) and small strategically placed spots of hot melt glue to tack the top in place while it dries. Then I stacked all the heavy objects I could find on top to clamp it and let dry overnight.

I got impatient and installed the drivers and who says you can't listen to speakers at low volume while the glue dries?

It sounds pretty good. I think these are bass/mid bass units rather than a true sub as I don't think that as a sealed cabinet it will go much below 60 Hz. However, I plan to bi-amp and use active XO/EQ in the future so using maybe some EQ to boost the bottom end may work well as there is not an xmax issue down there in a sealed cabinet.

So next will be some measurements and the moment of truth...


So far, I have 5 hrs into this speaker and $15 worth of parts/materials.
Attached Images
File Type: png Bass-Nautaloss-6p5-photo-05.png (525.8 KB, 733 views)
File Type: png Bass-Nautaloss-6p5-photo-07.png (480.2 KB, 670 views)

Last edited by xrk971; 22nd December 2013 at 07:39 PM.
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Old 22nd December 2013, 07:56 PM   #53
gpapag is offline gpapag  Greece
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Work of Art !!!
Hats off to you xrk971

George
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["Second Law is a bitch." - SY] ["The Road To Heaven:Specify the performance & accept the design. The Road To Hell:Specify the design & accept the performance"-Bruno Putzeys]
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Old 22nd December 2013, 08:33 PM   #54
xrk971 is offline xrk971  United States
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Default Bass Nautaloss - Measurements and Sound Clip

OK, call me impatient and had to get some measurements while the glue is drying.

Before I installed the driver into the box, I had mounted it on a 24 in x 36 in open baffle and measured its response at about 36 in above the floor.

The drivers were wired series in this box so the nominal impedance is 8 ohms, the sensitivity (with voltage) dropped but the amount of xmax was reduced allowing for the speaker to play overall louder and with reduced distortion.

The measurement was with the mic 12 in away, centered between the two drivers and 4 in off the floor. Obviously there will be some floor enhancement and we do not expect any baffle step loss. Blue is Nautaloss Bass, and red is same driver in an open baffle (OB).

Click the image to open in full size.

The measurement looks very good - almost identical to the open baffle measurement with the exception of the enhanced bass loading due to the floor (or reduced highs however you want to look at it). The response confirms that the Nautaloss behaves as if it is an open baffle or infinte back chamber as there are no reflections. The measured -3dB point was 52 Hz - same as the driver's fs provided by the manufacturer. This is actually sufficient bass for me to use this as the helper woofer for the Nautaloss tops which will be high passed at about 300 Hz. Sensitivity should be commensurate with the Vifa (85 dB vs 88 dB for woofer).

The THD also looks quite good - and this is playing at typical listening levels with amp volume knob at usual 1030 o'clock position.

My gripe is that this cheap woofer has a terrible suspension damping and flaps all over the place - as exhibited by the ringing in the impulse response. But its decays rather quickly (< 1 ms) so should not be too perceptible. But hey, what do you expect from a $4.88 driver

Overall, I have to say that this performance is quite astonishing for the price and time invested. I think upgrading to a better 6.5 in woofer may be in the works. However, this cabinet design has proven itself to act as if it is a sonic black hole for the back radiation.

In case you are wondering what it sounds like, here is a short clip recorded with the same measurement mic in mono.
Attached Images
File Type: png Nautaloss-Bass-Meas-photo.png (564.7 KB, 819 views)
File Type: png Nautaloss-Bass-Meas-with-OB.png (59.9 KB, 756 views)
Attached Files
File Type: zip Bass-Nautaloss-Clip-1.zip (910.0 KB, 39 views)

Last edited by xrk971; 22nd December 2013 at 08:36 PM.
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Old 22nd December 2013, 08:34 PM   #55
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by gpapag View Post
Work of Art !!!
Hats off to you xrk971

George
Thanks, George.
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Old 23rd December 2013, 12:09 AM   #56
xrk971 is offline xrk971  United States
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Default Nautilus freq response

I looked for the Nautilus 801 freq response and it is not as flat as I thought it should be. I guess this is to be expected for a multiway speaker. I believe it is a fully active 3 way system.

Click the image to open in full size.

Click the image to open in full size.

Last edited by xrk971; 23rd December 2013 at 12:11 AM.
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Old 23rd December 2013, 03:08 AM   #57
xrk971 is offline xrk971  United States
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Default Bass Nautaloss with Quad Driver Push-Pull

I had a crazy idea to add two more drivers in a face-to-face push-pull configuration in hopes of reducing THD and increasing efficiency. The drivers are now wired in parallel-serial for a nominal 4 ohm load.

I did not expect it to work this well though: I got a 10 dB boost in the bass efficiency (nominal single driver efficiency was 88 dB, I suppose that means it is now 98dB?? ), the THD dropped by 5 dB, and most importantly, the impulse response stopped flapping and is now much, much tighter.

The quad driver P-P config is green, the two driver version is blue, and the OB reference is red.

Click the image to open in full size.

Just to reduce the cluttered graph, here is the quad driver P-P all by itself:

Click the image to open in full size.

I am happy with this outcome
Attached Images
File Type: png Nautaloss-Bass-Quad-Driver-PP.png (593.3 KB, 186 views)
File Type: png Nautaloss-Bass-Meas-with-OB-PP-Quad-Driver.png (60.4 KB, 930 views)
File Type: png Nautaloss-Bass-Meas-PP-Quad-Driver-only.png (43.8 KB, 1512 views)

Last edited by xrk971; 23rd December 2013 at 03:13 AM.
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Old 23rd December 2013, 11:48 AM   #58
xrk971 is offline xrk971  United States
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Default Photos of Completed Nautaloss System

I have the Nautaloss bass speaker running through a mixer to combine left/right channels. The Nautaloss tops are driven by my diy TPA3116D2 amp, the Nautaloss bass is driven by the Yamaha RX360. I still don't have a crossover and running both speakers fullrange - yet it sounds amazingly good. The bass is very clean and fast now. The 50 Hz extension is just the right amount of reach for now.
Attached Images
File Type: png Nautaloss-Bass-Quad-Driver-PP-Final-Photo.png (518.3 KB, 1586 views)
File Type: jpg Nautaloss-Bass-Quad-Driver-PP-System-Photo.jpg (166.5 KB, 326 views)

Last edited by xrk971; 23rd December 2013 at 11:56 AM.
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Old 23rd December 2013, 01:37 PM   #59
sippy is online now sippy  United Kingdom
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They look far more interesting that a conventional box system.
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Old 23rd December 2013, 03:15 PM   #60
xrk971 is offline xrk971  United States
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Default Rear view

Nautaloss bass quad driver push-pull, rear view showing detail of legs and terminal cup.
Attached Images
File Type: png Nautaloss-Bass-Quad-Rear-View-Photo.png (402.9 KB, 306 views)
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