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The Nautaloss II Fullrange Tops

6458 Views 12 Replies 5 Participants Last post by  pacogun
I started this thread over in diyaudio.com but thought folks over here may have an interest in it too. It started off on a whim with me asking myself does the namesake speaker from B&W really sound nice because the spiral absorbs the back wave? Why not try it out on a smaller, cheaper scale and see? Normally, I model and simulate a speaker pretty thoroughly before committing to a build (even though it is in foam core - so no worries if it doesn't work out). I started by thinking of the max physical envelope I wanted this to occupy, hand drew a spiral that was 3 ft long (I did calculate this to makes sure that the 1/2-wave TL resonant freq was about 300 Hz). I basically have a driver that I use for almost all my speaker projects - the Vifa TC9FD - a wonderful sounding 3.5 inch paper cone full range high Qts driver that I have successfully used in a straight TL, MLTL, BLH (scoop, cornu, and BIB), and now a sealed TL. I first started with a single driver to see how it sounds. That was hugely successful so I went for 2 drivers to boost efficiency and max SPL. The back spiral effectively absorbs any backwave like an acoustic black hole. In single driver mode, the response was flat +/- 3dB from 150 Hz to 18 kHz and the imaging, soundstage, and clarity were just amazing. It needs to be paired with a woofer/subwoofer to round out the bottom end (that is the topic of the Nautaloss Sub - in the sealed subwoofer forum: http://www.hometheatershack.com/forums/sealed-subwoofer-build-projects/72373-nautaloss-sub.html). But the vocals range, all the way to cymbals, high hats, bells are all sparkling clear. I don't want to repeat everything here so if you need more details please go to: http://www.diyaudio.com/forums/full-range/247598-nautaloss-ref-monitor.html

Here are photos of the finished dual driver speaker front and back. The overall dimensions are 13 in front (due to back tilt), 5-3/16 wide, 9 in deep:

Here is the SPL vs frequency.

Here is the Distortion, with THD typically below -50dB! This is measured at typical volume of about 87 dB at the listening position.

And here is the Impulse Response - very clean and tight - plucked strings, bongo drums, guitar, etc all sound very realistic and articulate.

When I started building these, they were meant as "Reference Monitors" as I needed a set of speakers to compare the sound to my other speaker builds and I wanted something that was clean and flat in response. I think I achieved it, but then I realized that the size, and low cost makes them perfect for HT installations where you want crisp, neutral, articulate sound without spending a lot. The fact that they are made of foam core has advantages of light weight for wall mounting or suspension from the ceiling.


If you are interested in how to make speakers out of foam core, check this out: http://www.diyaudio.com/forums/full-range/223313-foam-core-board-speaker-enclosures.html
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Very cool - do you have any photos of the build process or of the inside?
Here are some photos of the inside.

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Final In-Room Response with Nautaloss II & Subs - Reference Quality!

Here is the final in room response at listening position after the REW via miniDSP is applied (-48 dB/oct high pass at 35 Hz and -24 dB/oct low pass at 200 Hz on the subs; 150 Hz -24 dB/oct high pass on the tops; used REW to smooth sub response). I am using the Nautaloss Sub in addition to two diy MLTL's as subs (built using the same 6.5 in polycone PE buyout driver as the Nautaloss sub). The amp for subs was Yamaha RX360 class A/B, amp for tops is home-built TPA3116D2.

SPL vs Freq shows that at an average SPL of 96 dB (about 9 dB louder than how I actually listen to music), the -3 dB response range is 42 Hz to 18 kHz.:

Distortion vs Freq is excellent now showing between -30 dB to -40 dB from 40 Hz on up. Note that at actual listening levels of 87 dB, the THD will be even less and will match the -50 dB figure I previously obtained:

Impulse Response shows a pretty tight response with a single ring that subsides after 200 microseconds:

All in all, a very nice performance for any speaker, I won't even qualify it with budget drivers or foam core construction. What is interesting is after all this, what matters is how does it sound? Well, I was shocked and blown away is all I can say. Once you have a set of speakers dialed in with a response curve that is this flat and extends pretty much over the normal range of music program and you put some music on, you are struck by how great it sounds. The sound resembles what I would hear through my studio monitor headphones but without the feeling of having the sound image between my ears. Instead, a real sound stage with depth and spatial extent to the sides, back, and a sense of the sound textures that were meant to be heard by the sound engineer. The articulation in the bass is very nice and it renders piano, drums, and other percussion instruments with realism. The smoothness of the vocal range is just amazing. Very happy with the setup. :D

The setup resembles this photo but with the Nautaloss I tops replaced by the II's.

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If you have an account on diyaudio.com you can check out a sound clip of the Nautaloss II and subs running through the miniDSP. I would upload here but the 263k limit prevents me from doing so.

xrk971, Nice job & good experience! But(I'm sorry) what kind of material did you use to make shaped details ?
I use foam core boards - paper faced foam boards used for posters and presentations. Most of what I build comes from dollar store an is 20 x 30 in x 0.1875 thick. You can get stiffer higher quality boards made by Elmer's for $3.50 to $6 ea at art stores (and sometimes supermarkets). Nice stuff but more difficult to cut and costs more. The dollar store stuff works well with hot melt glue. Check out the Foam Core speaker thread in diyAudio to get tips on how to make speakers with it. To make curves you score thin cuts on concave side and use a roller to prebend it. Then hot melt in sections to tack on. Final cap operation use PVA glue. The best part about using foam core for speakers is it is very clean and you don't need a workshop. I work on a carpeted floor which is perfect for cutting foam with a razor. All the tools you need are an xacto, a hot melt glue gun, a straight edge, a pencil, and a bottle of PVA.
Stiff enough for what? You can't sit in it like an mdf speaker. Of course it isn't stiff like wood or mdf. But on a per weight basis, it may be stiffer. However, it is stiff enough to allow rapid construction of speaker enclosures that sound great. Just look at the measurements and testimonials of folks who have tried it. It is important to have bracing to keep the walls from excessively vibrating. Many folks did not think it could be used for a sub woofer where higher pressures are involved. That turned out not to be the case if you look at the Nautaloss sub thread. This design in particular has a spiral coil which helps to serve as inherent bracing. How many 30 x 20 x 7 in sub woofer enclosures that hit 115 dB do you know that weigh 2 lbs without the drivers? Anyhow, the construction is so easy and the cost so cheap that you should give it a try and listen for yourself. Nothing much to lose but your time to build.

Here are all the speakers I have built from foam core:
xrk971 Can I say your build is remarkable, and brilliant, I can't believe it measures so well for so little dollars, its got me thinking about future builds now. but I wonder if a more rigid material(s) would actually degrade the sound??
Awesome speakers! Well done.
But, most of all, I amaze with the freq response. How come foam core enclosure able to produce such freq response. Most speaker builders aim to build rigid and solid enclosures. This is a mind opener. Well done!
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