design - proof of concept : i think i've gone insane - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 14 Old 05-31-2013, 04:45 PM - Thread Starter
Newbie
 
Kitame Sume's Avatar
 
Join Date: May 2013
Posts: 7
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
before you guys start anything disturbing understand that i hardly know my stuff, although i'm interested to learn.

i've been reading about sealed and inf-baffle, if i understood correctly sealed has the smallest box and is the easiest to design though often having a roll-off on the lower frequencies, with inf-baffle having the flattest response curve although requires one of the more complex to design.

so i thought of it, why not try mimicking the effects of inf-baffle while maintaining the compactness of a sealed box?


as one might expect, i've gone insane. i can already hear comments "wtf is this?" "pure waste of money" and other disturbing comments hahaha.
but please relax i'm only gathering opinions and proof of concept.

as for the design, first i thought of having only two set of drivers facing each other, but it hit me that it'll stupidly vibrate and cause distortions. so i had separated it to three drivers with the two facing each other for them to cancel out, neat.
as for the concept, as you see the whole box is sealed, with chambers of their own, but whats these color coding. well as it looks, the gray area in the middle is a neutral zone where pressure should stay constant because of the other two drivers, the red zone though would be the main damping chamber to damp excess pressure off the gray area.
ignore the yellow stuff at the back since those are just dampeners, foam maybe just to damp reverberations from the main driver.

with this design, it should be probable to create a neutral pressure in the gray area ideally staying that way for all frequency curve, mimicking an infinite baffle. although excessive pressure on the red zone may as well destroy the inner drivers but lets ignore that for now.
for this design to have an ideal outcome, the displacement of the main driver should have proportional amount with the two inner drivers of 1:1, tuning it should be easy though but what about having the inner driver performing more?

having a ratio of 1:(N>1) would result into this:

the blue is the main driver, while the red is the inner drivers. as you can see theres an area where the displacement aids the main driver in a good way, during minimal excursion of the drivers theres no perceived effects, but higher excursion level would gain benefits.
this could be seen as a higher response rate on higher output or lower frequencies, maybe even both.

PS: excuse the crude drawings, heh.
Kitame Sume is offline  
Sponsored Links
Advertisement
 
post #2 of 14 Old 05-31-2013, 04:58 PM
Advanced Member
 
cookieattk's Avatar
 
Join Date: Jun 2011
Posts: 567
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 29 Post(s)
Liked: 59
no
cookieattk is online now  
post #3 of 14 Old 05-31-2013, 05:01 PM - Thread Starter
Newbie
 
Kitame Sume's Avatar
 
Join Date: May 2013
Posts: 7
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
which no? "no, you didnt go insane" or "no, thats a really stupid idea".
Kitame Sume is offline  
post #4 of 14 Old 05-31-2013, 05:53 PM
Advanced Member
 
filtor1's Avatar
 
Join Date: Feb 2008
Location: Florida
Posts: 954
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Liked: 28
No you are not insane. And no it is not a stupid idea. Your idea will not work the way you are proposing. Are you familiar with Hoffman's Iron Law? Start there. Also look up and read through the many dual opposed builds here. I think you may find them interesting. You can find the majority of the in them here :

http://www.avsforum.com/t/1104368/master-index-of-diy-subwoofer-projects

And some light reading for someone looking to learn and gather what works and what doesn't:

http://www.avsforum.com/t/1443078/new-to-diy-faqs-in-here

Keep your curious nature when approaching a new idea. Then read as much as you can.
filtor1 is offline  
post #5 of 14 Old 05-31-2013, 07:31 PM - Thread Starter
Newbie
 
Kitame Sume's Avatar
 
Join Date: May 2013
Posts: 7
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
well yeah, if i wasn't curious why bother asking XD
i think i've read hoffman's iron law somewhere though yeah it kinda rings a bell.

as for the concept i had in mind, it came from air displacement using pressure pumps, but using axial or piston pumps would be counter productive since they can't keep up so why not use speaker drivers(aka diaphragm pumps)?
theoretically speaking having the inner driver displace air into the red chamber during the main driver's backward stroke should provide a pseudo effect of as if the room is bigger, while displacing air towards the gray chamber during the forward stroke that mitigates the negative pressure created by the main driver.
[perfect 1:1 displacement ratio]


[1:(N>1) displacement ratio]


gray = neutral pressure
orange = negative pressure
red = positive pressure

efficiency aside, it is presumable that i have to at least up the power output of the inner driver to reach 1:1 displacement ratio over the main driver due to the inner driver needing to compress air, the problem is though can it keep up?
possibly i'd need more that twice the total power input to achieve the same power output as a perfect inf-baffle just to replicate it on a tiny sealed box.

PS: at the moment i'm looking at the DIY Gallery for ideas for it's look, SONO too big =x
edit: oh and do you guys measure in peak watts or rms watts?
Kitame Sume is offline  
post #6 of 14 Old 05-31-2013, 07:41 PM
AVS Special Member
 
Bill Fitzmaurice's Avatar
 
Join Date: Nov 2009
Location: New Hampshire
Posts: 9,925
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 1533
Quote:
Originally Posted by Kitame Sume View Post

if i understood correctly sealed has the smallest box and is the easiest to design though often having a roll-off on the lower frequencies, with inf-baffle having the flattest response curve although requires one of the more complex to design..
Sealed and infinite baffle are the same thing. The term 'infinite baffle' has been hi-jacked to apply to drivers mounted with the front wave facing into the listening room and the rear wave facing into another room, basement or attic, but the definition remains an enclosure where the front and rear waves don't meet. As for what you've pictured, it appears to be isobaric, which is nothing new or special.

Bill Fitzmaurice Loudspeaker Design

The Laws of Physics aren't swayed by opinion.
Bill Fitzmaurice is online now  
post #7 of 14 Old 05-31-2013, 07:42 PM
AVS Special Member
 
Jay1's Avatar
 
Join Date: Aug 2002
Location: AZ
Posts: 3,981
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Liked: 102
Jay1 is offline  
post #8 of 14 Old 05-31-2013, 07:48 PM - Thread Starter
Newbie
 
Kitame Sume's Avatar
 
Join Date: May 2013
Posts: 7
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
that, indeed, now theres a real concept(which means i ain't insane XD).
now the question is though, does it still work with today's drivers?

edit: speaking of which, what would happen if i drive the inner driver with more power than the outer driver?
Kitame Sume is offline  
post #9 of 14 Old 05-31-2013, 07:57 PM
AVS Special Member
 
Bill Fitzmaurice's Avatar
 
Join Date: Nov 2009
Location: New Hampshire
Posts: 9,925
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 1533
Quote:
Originally Posted by Kitame Sume View Post

that, indeed, now theres a real concept(which means i ain't insane XD).
now the question is though, does it still work with today's drivers?
It does, but since modern drivers have Vas values that run on average less than half that of drivers 40 years ago when isobaric was semi-popular there's really no point in doing them anymore.

Bill Fitzmaurice Loudspeaker Design

The Laws of Physics aren't swayed by opinion.
Bill Fitzmaurice is online now  
post #10 of 14 Old 05-31-2013, 08:04 PM - Thread Starter
Newbie
 
Kitame Sume's Avatar
 
Join Date: May 2013
Posts: 7
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
true, yet i'm space deprived (think bathroom) so having a large woofer would be quite iffy.
although having frequency response time reach sub 20hz would be neat, i've heard only inf-baffle or well-made vented reaches those frequencies, sucks to say i've heard of vented and loathe their inaccuracy.

edit: ohh but unless theres a 15" that can reach at least 22Hz & 80SPL(peak) :O with a volume of 480cubic feet.
Kitame Sume is offline  
post #11 of 14 Old 05-31-2013, 08:24 PM
AVS Special Member
 
Bill Fitzmaurice's Avatar
 
Join Date: Nov 2009
Location: New Hampshire
Posts: 9,925
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 1533
Quote:
Originally Posted by Kitame Sume View Post

sucks to say i've heard of vented and loathe their inaccuracy..
Vented cabs are no less accurate than sealed. If you heard one that was inaccurate it's because it was a poor design or it wasn't properly set up.

Bill Fitzmaurice Loudspeaker Design

The Laws of Physics aren't swayed by opinion.
Bill Fitzmaurice is online now  
post #12 of 14 Old 05-31-2013, 08:32 PM - Thread Starter
Newbie
 
Kitame Sume's Avatar
 
Join Date: May 2013
Posts: 7
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
possible.
although designing a compact vented would be much more complicated than a normal sealed, no?

speaking of designing, i wonder if i could use those cheapo 20$ 12" for dummy speakers just to test out box designs, swap the speakers with a better one later, lol.
Kitame Sume is offline  
post #13 of 14 Old 05-31-2013, 08:39 PM
Advanced Member
 
filtor1's Avatar
 
Join Date: Feb 2008
Location: Florida
Posts: 954
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 8 Post(s)
Liked: 28
What about disguising a piece of furniture?

http://www.billfitzmaurice.com/TT.html

Or if you have a long wall under the tv or even behind a couch you can try something like this.

http://www.avsforum.com/t/1404092/wanted-big-bass-big-room-open-to-an-even-bigger-room-with-lots-of-windows

Some end tables. You can shrink these down to suit your size requirements and driver selection.

http://www.avsforum.com/t/1018171/18-easy-button-end-tables-24-x-21-x-36-hwd

If you have the budget. A couple sealed 5400 end tables. The opposite of efficient though.

http://www.avsforum.com/t/935522/ebony-and-ivory-dual-18-lms-5400-endtables-completed

The first two are super efficient relative to the second two. Just throwing idea out there for you. None of these may fit your desired direction. I hope it helps a little in the process of ideas though.
filtor1 is offline  
post #14 of 14 Old 05-31-2013, 08:55 PM - Thread Starter
Newbie
 
Kitame Sume's Avatar
 
Join Date: May 2013
Posts: 7
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
well first off, everything is concrete here biggrin.gif
i pretty much have no space left other than replacing the TV table, although its doable it isn't much room, pretty much can only fit two 18" i guess, its not much more than a feet deep too(flat screen TVs pfft).
to be exact the measurement is WDH 40"-14"-28", enough for a set of two 18", sealed bookshelves can fit beside the TV so mids and highs aren't a problem.
target peak SPL is 80dB with the target average loudness being 60dB, i'm only after the kicks for those 80dB peak.

what would happen if i seriously put these subs on such a cramped box o.o i'm assuming roll-off frequency would be quite high.
edit: speaking of which, 12" should be plenty, although i haven't gone window shopping for available subs but most likely it'll be a limited choice, i rarely see 10"~12", mostly theres only 15"~20" subs available :P i don't even recognize some of the brands.

i have no plans on building one yet, i'm only collecting data of which would be the best case scenario, meh. budget estimates though... hmm... i guess around 500-800$ should be good enough.

edit2: another question, 4way or 3way? keep in mind that design+tweak hassle = not my cup of tea.
if its a 3way 15"(15-100) + 6"(100-10K) + tweet(10K-24K). or if its a 4way 15"(15-60) + 8"(60-2K) + 4"(2K-15K) + tweeter(15K-24K).

edit3: http://www.avsforum.com/t/1116596/sealed-audiopulse-axis-15-build-thread
this one is interesting, so they can be built that small.
Kitame Sume is offline  
Reply DIY Speakers and Subs

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off