2" tapped or folded horn?

bnbgn

Member
2010-10-16 8:20 pm
This may be a silly question... but i'm really curious about this...
If one were going to get a 2" subwoofer to go down to it's absolute lowest... what would be the enclosure of choice? here's my speaker. http://www.amazon.com/Tang-Band-W2-1767S-Neodymium-Woofer/dp/B002HT8DHO/ref=pd_sim_sbs_e_5

it's rated to go down to 110 hz. If I build a halfwave folded horn for, say 40hz, so 1/2*28.1332 ~ 14'... will this configuration produce audible sound down to 40 hz? how about a quarter wave?, or is it just physically impossibly to get a 2" driver to resonate anything lower than 110 hz? If I knew it would work with 7' of horn i'd be happy...

I'm probably going about this wrong, because the way i understand it the surface size of your driver dictates your wavelength of interest... so if it's 110 hz.. i'm best going with a 1/2 of that? so 10.2303/2 or ~5 feet?

My second question is will a tapped horn or standard folded horn perform best for attempting to coax these low low's from such a small driver? If i knew how to run hornresp i'd try and plug the #'s in.

Thanks... just trying to generate some ideas..

bnbgnoise
 
You can bring this 2" 'monster' down to 40 Hz, though as a rule of thumb diving 2 times below Fs is the maximum. For a fixed enclosure volume going lower means less maximum output based upon excursion limits.

Reading this should give you the basic skills needed to design your horn: Guide to WinISD Pro and Hornresp - Speakerplans.com Forums - Page 1

Compression ratio could probably be between 1 to 6 or there abouts for starters.

Regards Johan
 

jbell

Member
2003-04-02 4:34 am
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I guessed on Sd and Le, but here's a start...

Would be a fun little project made out of 1/8" bb ply as a computer sub sat in the corner of a room.
 

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bnbgn

Member
2010-10-16 8:20 pm
@Jbell thank you thank you! You feel my concept!? small, LOW. Thank you though, i will save that capture of those #'s as i know it will be usefull reference as I look into this. So you did, or didn't render the output for the horn resp... were you able to make any scene of the #'s as far as freq resp? Might I ask what the Sd and Le represent?
 

bnbgn

Member
2010-10-16 8:20 pm
@rademakers Thank you Johan! Good to know it should be able to reach that low... I'll be more inclined to design it to have lower natural responses with a little less overall volume as I really want to see some mini-sub sub action. Thanks again!
 

jbell

Member
2003-04-02 4:34 am
.
@Jbell thank you thank you! You feel my concept!? small, LOW. Thank you though, i will save that capture of those #'s as i know it will be usefull reference as I look into this. So you did, or didn't render the output for the horn resp... were you able to make any scene of the #'s as far as freq resp? Might I ask what the Sd and Le represent?

I was kinda 'trying' to get you interested in downloading hornresp, entering the numbers and starting to play with it.

Sd is the area of the driver cone. 19cm2 is a full 2" and I know that with the surround, that that is optimistic. It's probably about 16cm2 at most. Le is the inductance of the driver coil, and is not specified, so I just guessed. There are great tutorials out there, and the online help for hornresp is good as well. David has done a HUGE service to anyone who wants to design/build.... the least I can do is encourage someone to pick it up, see how easy it is, and get a good idea of what is and isn't possible. My post was meant as a starting place.... not the end answer on what is possible with this driver.
 

bnbgn

Member
2010-10-16 8:20 pm
That's awesome.. thank you for the starting #'s... that's a huge step forward... i've really wanted to learn horn resp... They should make a pictorial guide... or I should... (in a year when i figure it out) so it's easier to decypher... visual representations help me in understanding things alot better.

Thank you again!
 

jbell

Member
2003-04-02 4:34 am
.
That's awesome.. thank you for the starting #'s... that's a huge step forward... i've really wanted to learn horn resp... They should make a pictorial guide... or I should... (in a year when i figure it out) so it's easier to decypher... visual representations help me in understanding things alot better.

Thank you again!

nah... you should be up and running in less than an hour, not a year.... Here's a great hornresp tutorial by my friend mike... Simple Tapped Horn Tutorial using Hornresp - AVS Forum

And just as a teaser, to get you really interested in doing hornresp for your self. Here's the 10 watt output of your mighty little sub in a corner, 1 meter away. (typical for computer sub)

Now this keeps your driver under it's xmax rating from 60hz on up... You have said you wanted lower... time to play with hornresp and figure out how to make that happen.
 

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bnbgn

Member
2010-10-16 8:20 pm
Dang, Dude, Thank you... That is amazing software. very beutiful rendering of freq response, it's giving me hope! Now that I have my driver selected my cabinet parameters are the next step so there's no avoiding it now... what a cool tool.

If only I wern't being kicked out today I could clear the desk off and delve into it. So close, yet so far. Why my life plans change every day, i don't know, luckily I can continue research and design of my sub projects online. I should probably switch over to online flash-based cad design software too at this point and just live on the cloud.

Thank you so much jbell and others, bouncing ideas of experts is something i couldn't be more thankful to do!
 

18Hurts

Member
2010-11-21 11:20 pm
Hey bnb,

I'll trade you a Bose AM-5 "bass module" for your 2" tapped horn. If you can get 2 octaves below Fs, it will go lower than the AM-5.

All kidding aside (although if you want to trade, I'll do it!) great to see a project rolling to make a mini-TH. I might make one to practice on a $20 driver and a half sheet of wood before tackling a dual 12" TH.
 

bnbgn

Member
2010-10-16 8:20 pm
18 hurts--- nice name

but yes, you're right, that's quite the challenge to propose, knowing i have all the time, paper, CAD ambition and software i need, and little if any of the funding and technical background/experience it would take, but how could I back down?

Seriously though, thank you, tapped horn's seem to be the next "transmission line" for subdesign, so i'm more than interested in tackling the mini project. Right, i keep working afordability into the equation and ended up at the smallest round subwoofer that seemed legit, and so here I am, and honestly i'm more excited about the prospect now that it's taking it's dwarfed shape.
I've also given up on MDF... mainly because there's still alot of assembly required, which by all means was one of the original reason I got interested in big cabinet building, but at this scale, super mini scale, i'm feeling the rapid prototype ABS laser molded plastic vibe.

The deal sounds good though, if my predictions are correct, I could then take the driver from the AM-5 which i'm guessing is 5", and have a scaled up version of the TH 3d printed, and then trade up from there... hopefully to a 8" or 12", where I could start with the lazer cut MDF designs.

Horn-resping this out, and figureing out how much "compression" or whatever the initial size of the horn should be is my next step so i know the horn params... then teaming up with a 3d modeling buddy to fold it up in 3d and make it nice and pretty like will be my long, possibly projecting ending middle step. From there it should be a few dollars and a quick attaching of the sub to the plastic till anything is heard. I'll probably design the active peripherals, or at least plan for them (to hide them within) and add space for a transistor and a little panel, though that's more to allow it to go to "production" without significant or un-forseen redesign, i don't really have any talent in electrical eng.

Would love to see a mini-mini...

thanks 18. ps. i couldn't figure out what a fs was

@jbell thank you, your friend's horn resp guide is beautiful and very illustrated, it cleared up alot of confusion. just what i was looking for! thx again
 
Cool project, I'm all in favour of compact designs, it presents a challange beyond just achiving a resonable result in specs.

Regarding the link jbell psoted above, it's waaay to big for a 6,5" :) here's another way of folding when the space is limited :

http://www.diyaudio.com/forums/subwoofers/164199-th-micro-6-5-tapped-horn.html

But this design is far more of a size compromise in comparison.
 
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bnbgn

Member
2010-10-16 8:20 pm
marntinsson- you're saying that that first picture is too large a horn for the specified driver? My original approach was the tripple folded TH similar to the jbell pic... i like the inverted folded sort of approach in the diagram of your link. I can imagine I'm going to be building a long super super skinney five foot folded horn. I'm stalling on horn resp. till i get to a PC, but i kind of understand what to do next...

jbell thanks man for the immense help! Hope to talk to you guys soon...
 

18Hurts

Member
2010-11-21 11:20 pm
bnb,

I was looking at the Aurasound 4" aluminum woofer that has a Fs of 57 Hz and Xmax of 5.45 mm--that little thing would get you well into the 30s and costs $13.
I'm looking for a 5" with an Fs of 32 Hz and can't find one.

https://www.madisound.com/store/product_info.php?cPath=45_228_253&products_id=8996

Regular price is $31.50 so the $13.00 price would be cheaper than the 2" TB and should (could?) give you all the low end you need for music at your computer.
 
If you want to go lower you have to up the size. littlemike's starts fading in the 20s, yours in the 40s.

Absolutly true soho54, littlemike´s design is indeed very impressive, my design does not even come close in sub preformance, there's the compromise.

I would really like to build littlemike´s design someday, a true sub TH is very tempting and it is resonable in size aswell, my SPL requirements are modest and I'm sure I would be happy with it, it sure would be fun to have a real sub for once.

More compact TH's, this is a very intresting segment.