FR Driver for 2 lit. aluminium tube (BR)?

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den_hr

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Joined 2009
hana-lab.com
Hi all,

Having finished my "Frankenized" Martello speakers, and hearing that they actually sound quite nice (despite having used Visaton FRS8 instead of Fountek FR88EX), I'm thinking of embarking on a new project, with quite a different design: I'd like to make a pair of speakers out of aluminium tube (120mm diameter, 5mm tube thickness, so inside diameter is 110mm), with length approx. 25cm max. - so about 2 liters total inner volume.

It will be a bass reflex design, the "tube" will be horizontal, most likely with the BR port and tube in the back - something like these:
"Boxer" speaker

These will be used as desktop speakers.... without a subwoofer...

So, I'm looking for a suitable 3" driver (not sure if 3.5" will fit, depending on the overall basket mounting diameter), with at least some bass.

The Visatons (FR8S) I've used for the "Martello" build are relatively OK, but I'd like something a bit better looking - those FRS8 are rather bland-looking, if not downright ugly :)

So, any recommendations for a driver for such an enclosure? Of course, I'd like to keep the cost down, so the cheaper, the better :)

I've been thinking about Hi-Vi BS3 - or I might bite the bullet and buy the Founteks FR88EX (although something a bit cheaper would be better- FR88EX in EU is about €40, while HiVi B3S is half that price). Forgot to add, I'm in Europe (Croatia), so US-made drivers are sometimes difficult to find.

Any suggestions regarding the design of such speaker (internal bracing, bass reflex port tube design and placement, damping, etc.) are also more than welcome - I'm only a humble beginner as regards speaker building :)

TIA,

Denis
 
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den_hr

Member
Joined 2009
hana-lab.com
Thanks for the suggestions so far...

Dave, I know that FF85WK is a nice driver, and would probably be OK for my purpose, but it's a bit too expensive for my project - about €67 in Europe (about $75?) - and I'm trying to keep the cost down.

I think I might go with Aura NS3 - Dayton ND91 would be even better, but only available at Intertechnik in Germany, AFAIK, at somewhat expensive shipping costs... :(

So, I'll most likely go with Auras, and see what happens.

Any suggestions for BR tube dimensions and internal bracing for the aluminium tube enclosure as described?

Thanks,

Denis
 
J

Jerms

Member
Joined 2015
den_hr said:
Thanks for the suggestions so far...

Dave, I know that FF85WK is a nice driver, and would probably be OK for my purpose, but it's a bit too expensive for my project - about €67 in Europe (about $75?) - and I'm trying to keep the cost down.

I think I might go with Aura NS3 - Dayton ND91 would be even better, but only available at Intertechnik in Germany, AFAIK, at somewhat expensive shipping costs... :(

So, I'll most likely go with Auras, and see what happens.

Any suggestions for BR tube dimensions and internal bracing for the aluminium tube enclosure as described?

Thanks,

Denis
Click to expand...

Only thing I'd add is the Aura's can lack HF. Would seem to be true of the Daytons too.
 
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den_hr

Member
Joined 2009
hana-lab.com
Jerms said:
Only thing I'd add is the Aura's can lack HF. Would seem to be true of the Daytons too.
Click to expand...

Ah, most of us old farts can't hear anything above 13KHz anyway :)
I know I can't :D

These speakers won't be for teenagers, so that shouldn't be that much of a problem. I'm aware that adding a tweeter (any tweeter) would improve almost any FR driver, but I'm constrained by the enclosure shape and type, and absolutely must retain the clean design lines (no external tweeters sticking out, either). So, it must be a single FR driver - and I'm willing to sacrifice some HF for a better bass response.

I'm aware that this will be a compromise, and I don't expect a high-end hifi speaker. But, with the results I got from my humble FR beginnings (see the Martellos linked in my first post), I am 100% positive that I can make a pair of FR speakers (even with relatively cheap drivers, like the Visatons) that will sound better than any shop-bought "office" PC speakers (as regards the quality of the sound, not the bass... I don't plan on using a subwoofer).
 
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den_hr

Member
Joined 2009
hana-lab.com
Jerms said:
Going by Paul Carmody's Sprite, 4L-4.5L for 60-65hz tuning. Can get 55hz or lower with a 6L enclosure.

Do a DCR with 2 tubes and 3 ports?
Click to expand...

I'm afraid not - I'm limited by volume and size. The enclosures will be aluminium tubes, to fit my other designs - see attached photos (speaker "tubes" will be placed horizontally, like in the first photo, slightly angled upwards).
My servers and Class D amplifiers (shown in the photos) are in round aluminium enclosures, and I want to make some unusual speakers which will fit the general design (round aluminium tube with wood details). If I increase the tube diameter from 12cm to something bigger, the speakers will look very unsightly ("stubby" and too big, I guess...).

So far, I've arrived at 12cm diameter aluminium tube (my server + amp enclosures have 15cm diameter), with approx. length of 22-25 cm (max) - which gives about 2 - 2.1 liters internal volume, so that's what I have to work with. The speaker "tube" in the photos is 12cm diameter, 25cm length - and I wish I could make it even a bit shorter... like 20cm max.
 

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J

Jerms

Member
Joined 2015
For the ND91s, I modelled in WinISD, the enclosures were small compared to the ND90s or Aura NS3s.
ND91-4 was say 1.4L for around 70hz tuning.
ND91-8 was say 2.5L for around 60hz tuning.

They don't seem to drop as low as the Auras but require much less volume.
Fountek FE87 modelled OK but needed more volume and has much less linear XMAX.
 
D

den_hr

Member
Joined 2009
hana-lab.com
Ah, I finally found the reference to 1.5 liters - and it comes from Dave :)

http://www.diyaudio.com/forums/full-range/224610-ns3-pc-speakers.html#post3262867

Dave: "My NS3 were in about a 1.5 litre box, they worked fine."

Hmm, I think I might just try that: 1,5 litre sealed enclosure, and see what happens :)
(It means I could make my "pipe speaker" shorter, which is a big plus...)

Now, to order the drivers :)
 
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