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Old 7th February 2015, 02:46 PM   #1
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Default Fostex FE83 - Nagaoka F-81 or not

A few months ago, I found an old box in my basement, Among other bits, it contained a pair of Fostex FE83 that I used in my car 20 years ago.
I haven't owned or built speakers since then, I prefer headphones. But still, these "good ol'" FE's are now waiting for a cause. I had thought to build some little desktop speakers, but then...

I searched the internet for cabinet proposals, and soon found the Nagaoka F-81 (and also the Blumenstein Naga). The "slim look" is amazing, the concept looks interesting, but I couldn't really figure out how this design would perform.

I reverse-engineered the dimensions according to information and pictures I found on the internet, and then did some simple calculations:
Considering this design as a wavelength resonator, calculations lead to "120 Hz". Considering it as a Helmholtz resonator, calculations lead to "120 Hz". It is said that "technology advances from the primitive, to the complicated, to the simple", and The F-81 design seems quite simple to me.

Later-on, I bought AJHorn, here's the simulation results. But still, I don't know if this concept is worth considering a build.
Back then, I had highpassed these drivers at 150 or 200 Hz. It would be interesting to hear them all the way low, but my experience says that all I could expect is noise, not sound.

r

Attached Images
File Type: jpg FE83 - Nagaoka F-81.jpg (308.1 KB, 224 views)

Last edited by rasputin1; 8th February 2015 at 10:14 PM.
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Old 7th February 2015, 04:17 PM   #2
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I did not only evaluate the Nagaoka design. Here's a few desktop speaker and horn designs...

r

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File Type: jpg konzepte.jpg (158.4 KB, 214 views)
File Type: jpg konzepte_horn.jpg (187.2 KB, 212 views)
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Old 7th February 2015, 04:38 PM   #3
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I was kinda bored when I tried to redesign the B&W Nautilus shape for the FE83. I 3D-printed a 1/3 scale model of that FE83 Nautilus, to judge the design's aesthetics.

I wonder how this would work as a desktop speaker, powered through one of those modern DSP modules.
(I found that the FE83 is not really suited, found a different driver that would fit perfectly, then found out about the "Nautaloss", so this will be a separate project soon.)

r

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File Type: jpg IMG_3203.jpg (974.9 KB, 212 views)
File Type: jpg nautilus3.jpg (186.6 KB, 197 views)
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Old 7th February 2015, 04:42 PM   #4
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I had also considered to combine the FE83s with some woofers, i.e. build some d'Appolito floor speakers with Alpair CHP70. But then, it would feel like wasting the Alpairs....

r
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Old 7th February 2015, 05:00 PM   #5
Greg B is offline Greg B  United States
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The phase null at 100hz would make me cautious about this design.

I suspect a basic one fold ML-TQWT would be superior, or a Metronome if you like the slim look. About 1m tall or so would be in the ball park I think.

I had a pair of these years ago. They're really pretty pleasant in the simple reflex enclosure. (~7 liters or so IIRC, I may still have the old sheet somewhere) The frequency balance is just a little warm, which subjectively makes up for the modest bass extension.

There was also a DCR enclosure IIRC. I've not heard that, but it's worth considering.

And don't forget the Buschhorn....
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Old 7th February 2015, 05:25 PM   #6
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The frequency would improve with damping (not considered in the simulation), changing the distance of vent opening to speaker (currently ~1 ft), or moving the driver to a different position (which would mean mving away from the original design, even when it would not be visible from the outside).

Yes, I have considered building 6 liter vented cabinets, or the Fostex double bass-reflex design. But then, these would be too large to serve as desktop speakers, and not large enough for floor speakers.

Somehow, I can't get this Nakaoka design out of my head. It contains the old-fashioned "simplicity" that I am looking for.
I'd be happy to know whether it can be considered an "outdated approach", meaning that any "normal" closed/vented cabinet would sound a lot better, or if it's worth to use/evaluate it for a 2015 build. My experience is that this driver does not really like frequencies below 150-200 Hz, simulations with AJHorn hint for an even higher highpass frequency.

r
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File Type: jpg FE83_Full_Power_Highpass_comparison.jpg (256.7 KB, 53 views)
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Old 7th February 2015, 05:40 PM   #7
Greg B is offline Greg B  United States
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Well I still think you'd get better performance with a TQWT, but if you've got a hankering for the Nagaoka horn, perhaps you should just build one and see how you like it. Sometimes enclosures that don't look so great on 'paper' sound really good in reality.

It's been some time, but I'm pretty sure the small reflex was pretty solid down to Fs. This driver is certainly capable of performance below 150-200Hz.
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Old 7th February 2015, 07:18 PM   #8
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Quote:
Originally Posted by rasputin1 View Post
I had also considered to combine the FE83s with some woofers, i.e. build some d'Appolito floor speakers with Alpair CHP70. But then, it would feel like wasting the Alpairs....
The CHP70.2 is not an Alpair. They have a shelved down top end and decent bass, so they are a good candidate for a FAST.

An example of CHP used as midbass. Reiver Acoustic | Multiway | Jenna

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Old 8th February 2015, 03:59 AM   #9
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by rasputin1 View Post
I was kinda bored when I tried to redesign the B&W Nautilus shape for the FE83. I 3D-printed a 1/3 scale model of that FE83 Nautilus, to judge the design's aesthetics.

I wonder how this would work as a desktop speaker, powered through one of those modern DSP modules.
(I found that the FE83 is not really suited, found a different driver that would fit perfectly, then found out about the "Nautaloss", so this will be a separate project soon.)

r

The spiral sealed transmission line can sound very good. It is not a critical design - other than try to approximately match a volume to Vas. You might like this thread:
The Nautaloss Ref Monitor

FE83 should work well in a FC spiral Nautaloss.
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Old 8th February 2015, 02:56 PM   #10
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I have made a drawing of the Nagaoka F-81, otherwise this topic would not be complete.

I did some more simulations, firstofall, try to find a better position of the driver. Then I compared it to other potential cabinet designs.

To me, it seems that the F-81 design is trying to achieve something that the driver cannot really deliver. Compared to a sealed box of the same volume, it seems that all the F-81 design adds is "subsonic noise" (25-50 Hz)... ???

Quote:
Originally Posted by Greg B View Post
I suspect a basic one fold ML-TQWT would be superior [...]
And don't forget the Buschhorn....
I had designed one such ML-TQWT (see the picture above with the 4 different cabinets), based on some online calculator's results, and "tweaked" in CAD and AJHorn. I cannot really imagine how they would sound, I guess quite similar to a TL?

AJHorn cannot really simulate these, therefor I have used 3 approaches: Simulated as TQWT, as a TL, and as a "normal" vented box. I guess the real sound is pretty much a mix of vented/TL sim... ???

I had reverse-engineered the Buschhorn, too, but didn't like it much. If I were to build a horn cabinet, it would be one of the designs I had shown above. These are real 100 Hz horns, according to the classic math. Might be fun to build one.

Quote:
Originally Posted by planet10 View Post
The CHP70.2 is not an Alpair. They have a shelved down top end and decent bass, so they are a good candidate for a FAST.
My mistake, thank You for correcting. I fear I would be "wasting" a lot of the CHPs potential if I used them as a woofer only... anyway, I think I'll go without a woofer for these FE83.

Quote:
Originally Posted by xrk971 View Post
The spiral sealed transmission line can sound very good. It is not a critical design - other than try to approximately match a volume to Vas. You might like this thread:
The Nautaloss Ref Monitor
Actually, it all started with the "speaker cover plate" that extends over the inverted suspension ring, just like on the "Minuskull". I remembered the Nautilus, and saw that it would fit perfectly with my "cover plate"..

When I designed it, I had no particular cabinet style in mind. I thought to leave the "internal wall" away and use it as a normal (but beautiful) vented box, if I added two ports (one on each side) to the center of the spiral. Then I thought it might work as a TL somehow, if I used the "internal wall".

But then I found the Nautaloss thread, and I love it. I want to do a Nautaloss sooner or later, but I do not want to use the FE83 there. My target would be to develop a cabinet that anyone can download and 3D-print. I'll start as soon as I'm finished with the FE83 activities.



Coming back to the FE83: I will build the F-81 even when I am not really convinced. I will also build the Fostex double-bassreflex cabinet, because I am curious. Greg B convinced me to try the ML-TQWT design, and actually it would be the only design that fits my initial "desktop speaker" wish.

When I found my dear ol' Fe83, I was so happy that I bought a pair of FE83En, just in case . Therefor, I could swap drivers and cabinets and compare.
I have seen that there's digital amplifiers that offer switches for two different sets of speakers (i.e, Dynavox AMP-S), so I might go for one of these... ???

r
Attached Images
File Type: jpg Nagaoka F-81.jpg (122.9 KB, 93 views)
File Type: jpg FE83 - Nagaoka etc.jpg (363.1 KB, 87 views)
File Type: jpg FE83 - ML-TQWT.jpg (335.5 KB, 30 views)
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