Two-chamber sealed enclosure - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 13th June 2012, 07:10 PM   #1
diyAudio Member
 
Join Date: Jun 2012
Default Two-chamber sealed enclosure

Hello

I have an inexpensive 10" woofer which I am planning to use as a subwoofer for some increased low frequency extension. I measured and calculated the Thiele/Small parameters for the 10" woofer and it seems like it could perform fairly well in a 32 liter/1.13 cu.ft. sealed enclosure.

I enclosed a WinISD .wdr file for this woofer, but here are the main parameters.
Qms = 3.4
Qes = 0.538
Qts = 0.465
Fs = 30.4 Hz
Vas = 48.3 L

Fs / Qes = EBP
30.4 / 0.538 = 56.5

The other two pictures show a loudspeaker enclosure principle which utilizes two sealed chambers which are connected to each other via a "resistive" port. Does this kind of alignment have certain advantages when compared to a regular sealed enclosure?

I would be interested if somebody has more information or experience regarding this type of speaker enclosure.

Best regards
Attached Images
File Type: jpg aperiodic.jpg (52.8 KB, 247 views)
File Type: jpg schedorf11id.jpg (61.6 KB, 232 views)
Attached Files
File Type: zip 10-woofer-parameters.zip (731 Bytes, 10 views)
  Reply With Quote
Old 14th June 2012, 11:31 AM   #2
MaVo is offline MaVo  Germany
diyAudio Member
 
Join Date: Jan 2006
Since it doesnt utilize the backwave, like TH or BR do, and doesnt add resonance to the frontwave, like FLH or BP do, it will behave exactly like a sealed enclosure of similar size. if you want to know exactly, get AKABAK and simulate it.
If you want to get the most out of your driver and dont mind investing some time, get hornresp and see what you can do beyond sealed enclosures.
  Reply With Quote
Old 14th June 2012, 02:08 PM   #3
diyAudio Member
 
Join Date: Jun 2012
Thanks for your reply and suggestion.

I'm not at all familiar with horn loudspeaker design, but it's my understanding that large volume may be needed for a well-functioning horn bass enclosure. But unfortunately I cannot allow for much larger than 40 liters of volume for this bass speaker as I would prefer it to be quite compact.

I attached two pictures of this 10" woofer. Its maximum excursion is approximately 8 mm (one-way), I measured it with a micrometer.
Attached Images
File Type: jpg IMGP1899.JPG (53.8 KB, 183 views)
File Type: jpg IMGP1897.JPG (51.5 KB, 179 views)
  Reply With Quote
Old 14th June 2012, 02:42 PM   #4
bjorno is offline bjorno  Sweden
diyAudio Member
 
Join Date: Mar 2005
Location: Jacobsmountain
Send a message via MSN to bjorno
Hi,

There is more to this type of box:

I need to lowering Qms of the driver, using Resistive braking - one coil shorted


Enclosure for high Q driver


b

PS: IMO: If the box would have a smaller volume,this approach should give a good result but then it may no more qualify for a 'Sub'.
Attached Images
File Type: jpg Two-chamber sealed enclosure..JPG (302.8 KB, 177 views)
File Type: jpg Two-chamber closed-box.JPG (372.3 KB, 41 views)
File Type: jpg Two-chamber closed-box.Cont.JPG (526.8 KB, 44 views)
  Reply With Quote
Old 14th June 2012, 03:04 PM   #5
MaVo is offline MaVo  Germany
diyAudio Member
 
Join Date: Jan 2006
a bassreflex could maybe fit in these 40 liters. it adds alot of low frequency output compared to a closed box, but makes a highpass or rumble filter necessary to avoid overexcursion. bandpass is also an option compared to closed box, used for limiting the high frequency output, which can lower distortion and localisability (is that a word?). if you combine both, you get a 6th order bandpass, which adds the most output. hornresp can sim those too.

btw, cool stuff, bjorno
  Reply With Quote
Old 14th June 2012, 04:15 PM   #6
bjorno is offline bjorno  Sweden
diyAudio Member
 
Join Date: Mar 2005
Location: Jacobsmountain
Send a message via MSN to bjorno
Quote:
Originally Posted by MaVo View Post
a bassreflex could maybe fit in these 40 liters. it adds alot of low frequency output compared to a closed box, but makes a highpass or rumble filter necessary to avoid overexcursion. bandpass is also an option compared to closed box, used for limiting the high frequency output, which can lower distortion and localisability (is that a word?). if you combine both, you get a 6th order bandpass, which adds the most output. hornresp can sim those too.

btw, cool stuff, bjorno
Hi, I too was thinking about suggestion a BP-box to lower the 'localizability ' but I would first pick a simple 4:th order considering the Driver T/S and the OP requirement of a small box.. but usually I prefer(post) examples of the more build challenging T-TQWT types always somewhat larger in volume but not necessarily in the required floor footprint.

b
Attached Images
File Type: jpg Mint-10inch_T-TQWT.JPG (686.2 KB, 47 views)
  Reply With Quote
Old 14th June 2012, 05:43 PM   #7
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
What you have posted are pictures of the Dynaco A50 & A35 -- these are generally classed as aperiodic. The patent is new to me, thanx. That it is of the vinatge that it is is interesting.

Naim does some enclosures like this, explaining that at high frequencies the small box is "seen" by the driver, at lower frequencies the 2nd chamber comes into play.

http://www.t-linespeakers.org/classics/dynaco.html

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 14th June 2012, 08:01 PM   #8
diyAudio Member
 
Join Date: Jun 2012
Quote:
Originally Posted by bjorno View Post
Hi,

There is more to this type of box:

I need to lowering Qms of the driver, using Resistive braking - one coil shorted


Enclosure for high Q driver


b

PS: IMO: If the box would have a smaller volume,this approach should give a good result but then it may no more qualify for a 'Sub'.
Hello

Thank you for your simulated data!

If I understand the graphs on your third attachment correctly, it wouldn't be of much use to place this woofer into a two-chamber enclosure of this size.

Nevertheless, it's interesting to notice that the figure 6-4 in your first attachment does show some increased low frequency extension. As the text says:
...The parallel mass and resistance not only reduces the peak by about the same magnitude, it significantly lowers the cutoff frequency. In this respect, it is a definitive improvement on the single-cavity system with acoustic damping of the driver...
I'm not very fluent with the technical terminology. Does "parallel mass and resistance" in this paper mean that the two cavities are connected with some kind of "lossy resonant device" (such as a slightly resistive bass reflex tube)? Or did I get totally off track?

Now it looks like I should go with a regular sealed enclosure with this woofer. But as MaVo suggested, I will consider adding a bass reflex tube into it.

Once again; thanks for replies
  Reply With Quote
Old 15th June 2012, 05:03 PM   #9
bjorno is offline bjorno  Sweden
diyAudio Member
 
Join Date: Mar 2005
Location: Jacobsmountain
Send a message via MSN to bjorno
Quote:
Originally Posted by d1030180 View Post
..If I understand the graphs on your third attachment correctly, it wouldn't be of much use to place this woofer into a two-chamber enclosure of this size.
Right,...It depends on the observation of your driver data where Qts= 0.465 that in a 32 L box would return a Qtc of ~0.73 and if ported the optimal volume is about 80L + your earlier request that it should be a 2-chamber closed design:
I calculated a Qtc for a 16L chamber (Closed box/2) would be ~0.93.

The enclosure volume you favor is in conflict with the picture you posted : Planet10 remarks are good, the shown drawing depicts aperiodic Dynaco A50 & A35 designs and are totally different in operation compared to what you proposed as the enclosure volumes are terminated with an aperiodic port(s). My simulations didn't take this fact into consideration at all as this was not requested.

At any case your pick of volume would not work well in a Dynaco style unless you increase the internal enclosure volume.

Quote:
Nevertheless, it's interesting to notice that the figure 6-4 in your first attachment does show some increased low frequency extension. As the text says:
...The parallel mass and resistance not only reduces the peak by about the same magnitude, it significantly lowers the cutoff frequency. In this respect, it is a definitive improvement on the single-cavity system with acoustic damping of the driver...
Here,I guess you missed the last part of your quoted sentence: ' with acoustic damping of the driver' as this refers only to the * marked part of 'Small' :
Two-chamber sealed enclosure..JPG picture that is only supported by Small himself via a private mail conversation ,never officially published before but here.

Quote:
I'm not very fluent with the technical terminology. Does "parallel mass and resistance" in this paper mean that the two cavities are connected with some kind of "lossy resonant device" (such as a slightly resistive bass reflex tube)? Or did I get totally off track?
No, The parallel mass and resistance Small mentioned is a superior method compared to any of the two camber methods, closed or ported: aperiodic or not, and is congruent with what Ive earlier have posted here:

I need to lowering Qms of the driver, using Resistive braking - one coil shorted

Picture:
I need to lowering Qms of the driver, using Resistive braking - one coil shorted

The in the submitted encircled components are the "parallel mass and resistance", not earlier shown in the posting to your thread.

So this is a separate method(Small referred to) that can be applied to most speaker drivers in order to change the Qts of a driver to better fit a too small enclosure.

The only penalty to pay is a lover driver efficiency/ sensitivity.
In my simulation,in your thread, I placed with density # 1 two layers of damping material near the rear of the driver in order to load the cone similar to the "parallel mass and resistance" method.

This way was only IMO useful to a small degree as the 'MJK' 'yellow' plot color shows.

You can lower the Qtc=~0.732 down a bit,but paying with a resulting small rippled response.

Quote:
Now it looks like I should go with a regular sealed enclosure with this woofer. But as MaVo suggested, I will consider adding a bass reflex tube into it.
Yes and Yes I would too choose MaVo's suggestion, i.e. If using an enclosure volume >= 40 L.
Then all the mentioned methods could be applied with a great success including a low cut-off FR : Planet 19's Mavo's and any of Smalls would work fine.
Otherwise, you have to fight with severe diminishing returns = a suboptimal sub(mid-bass) if when using your suggested too small enclosure volume.

b
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
offset driver with coupling chamber/throat chamber: possible with MJK mathcad models? gafhenderson Full Range 0 30th March 2012 11:35 PM
3 chamber dual band pass enclosure! help ! abhihemu Subwoofers 10 19th January 2012 09:24 AM
Driver and enclosure for 4 watt amp, 12x12 room, moderate volume chamber music? zenga123 Full Range 55 16th December 2010 02:06 PM
How to model a dual chamber ported(Weems) enclosure in WinISD? Please help >> beady Subwoofers 4 5th August 2004 09:14 PM
article about double chamber speaker enclosure PTSOUNDLAB Multi-Way 41 23rd April 2004 02:54 AM


New To Site? Need Help?

All times are GMT. The time now is 08:26 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2