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 16th January 2008, 08:47 AM   #1011
diyAudio Member
 
Join Date: Jul 2004
Location: Beveren
tb46: That sounds like an interesting design approach, might get structurally a little complex; resonators seem easier to implement. But, a really interesting AkAbak application.

Upon closer inspection I just noticed I forgot a comp chamber for the rear end of the driver. I'll give it a shot tomorrow.
The structural complexity might not be that bad after all: if my guess is correct that a front comp chamber can be left out, then only a back one would be nessesairly and if the motor assembly can extend into the resonator at the throat, then this back chamber can be as little as the space under the cone when the driver is screwed over a 1/2 sD hole near the mouth.
The resonator and the front chamber could be built into one but I first want to sim the effect of 2 separate ones first. So first I need to get the script working.


You speak of multiple resonators, but how would you implement that? I also considered several res at the throat, but since they all fire into the same throat wouldn't this couple all of them together into one resonant system as opposed to multiple separate ones?
The same could be true to some extent for my res+dual chambers idea, but I think this might be a bit different since comp chambers are not real helmholtz resonators and I see them more as acoustic compliance modificators.

that's it for today, off to work!
__________________
-- If in doubt: overdesign!
  Reply With Quote
Old 16th January 2008, 03:14 PM   #1012
tb46 is offline tb46  United States
diyAudio Member
 
Join Date: Jan 2006
Location: Texas
Default Helmholtz Resonators

Hi,

Cordraconis: I'll try to attach some .jpg's that show some applications of Helmholtz resonators in loudspeakers, and a link to the E. Jakulis paper.

Back to work.
Attached Images
File Type: jpg giuliani nicoletti_voight_helmholtz.jpg (23.8 KB, 1085 views)
__________________
Oliver
  Reply With Quote
Old 16th January 2008, 03:17 PM   #1013
tb46 is offline tb46  United States
diyAudio Member
 
Join Date: Jan 2006
Location: Texas
And the next one, plus the link:
http://baseportal.de/cgi-bin/basepor...&cmd=all&Id=13
Attached Images
File Type: jpg punzo_tqwt_helmholtz.jpg (55.2 KB, 1181 views)
__________________
Oliver
  Reply With Quote
Old 17th January 2008, 09:33 AM   #1014
diyAudio Member
 
Join Date: Jul 2004
Location: Beveren
ah, now I get it. Thanks for the JPG's. I'll have a look at the paper later.

So far I've put the back compression chamber and a corner loading reflector into the script but there isn't much approvement in the SPL plot.

The driver diaphragm displacement from akabak shows a gently sloping curve starting from 400hz till a whopping 2m (!) at 20Hz, which makes me think the driver isn't coupled to the system at all.
However, in the excursion dialog I can see the nodes and the connected components of the system so I'll try to use that to determine where the problems with my script are.

Clearly the learning curve of AkAbak takes longer than about 4 hours of educated cut-and-pasting-and-adjusting from the Help files.
__________________
-- If in doubt: overdesign!
  Reply With Quote
Old 17th January 2008, 01:59 PM   #1015
diyAudio Member
 
Join Date: Jan 2008
You might check in AkAbak that your 1 meter isn't actually 1mm. I just got into it, as well, to model tapped horns that hornresp wont. I was amazed to find displacement of 1 meter as well, especially at just .7 volts in, but if you double click the dark grey box that says(in my case)

"Uin=0.7Vrms"
"--TappedHor, N=2=3, Driver (diaph) 1"

It'll bring up a "Diagram Edit Range" Dialog, and you can see the vertical limits of the graph. My guess is that in your case it will tell you that the upper limit is 1 or 2cm and that the "1m" at the graph's edge stands for 1milli-.

On the subject of AkaBak, can anyone tell me if there is a way to get .5pi or 1pi predictions?

Joseph Decker
  Reply With Quote
Old 18th January 2008, 10:14 AM   #1016
diyAudio Member
 
Join Date: Jul 2004
Location: Beveren
To add reflection (for 1/8th, ... 1/4th ... space ...) you have to define a reflector and put in the keyword reflection at the end horn or the last radiator. See my latest script below.


Getting a good sleep after 4 days finally paid off: I think I figured out the node-system of AkAbak and here is the result. This script looks more like I think it should behave.

-----------------------------------------------------------



Def_Reflector TopCorner
Left=1.0m Top=1.0m Right=1.0m
HAngle=45.0


Def_Driver 'SPH-212'
dD=21,2cm dD1=6,5cm tD1=2,5cm |Cone
fs=30Hz Vas=82L
Qms=2,21 Qes=0,5 Re=6,2ohm fre=8kHz Le=0.6mH




System 'RLDCTH'


Driver Def='SPH-212'
Node=1=0=200=300 |Driver connected to node 200 and 300


Duct 'FrontCompchamber'
Node=200=201 |driven by node 200 (front driver) and it drives/connects to node 201 (open end of resonator)
sD=0,110m2 Len=1cm Vf=20L

Radiator 'AfterFrontCChamber' Def='FrontCompchamber'
Node=201
x=0 y=0 z=0 HAngle=0 VAngle=0


Duct 'Resonator' |80Hz one end closed resonator
Node=0=201 |def "resonator" with node 0 as closed end and connected to node 202
sD=0,110m2
Len=100cm


Waveguide 'Conical Horn'
Node=201=301 |Conical horn between nodes 201 and 301
STh=0,200m2 SMo=0,300m2
Len=350cm Conical


Duct 'BackCompchamber'
Node=300=301 |Driven by back of driver and drives/exits in the conical horn
sD=0,110m2 Len=1cm Vf=20L

Radiator 'AfterBackCompChamber' Def='BackCompchamber'
Node=301
x=0 y=0 z=0 HAngle=0 VAngle=0

Horn 'Endhorn'
Node=301 |Horn driven by node 301 (conical horn+output back comp chamber)
STh=0,300m2 SMo=0,500m2
Len=60cm T=1
x=0 y=0 z=0 HAngle=0 VAngle=0 dEdge=3m Reflection

-----------------------------------------------------------------

The Unity horn script MaVo posted some months ago, was most helpfull to give me the insight.


Now I have to do a direct comparison between HornResp and my script to see if they are similar.

Once again: if someone sees faults or errors in the above script, *please* point them out. Thanks in advance.
__________________
-- If in doubt: overdesign!
  Reply With Quote
Old 18th January 2008, 07:23 PM   #1017
Killjoy is offline Killjoy  United States
diyAudio Member
 
Join Date: Apr 2007
Default Recent Sims

Here are some sims I have beenplaying around with. I have some for the Dayton Quatro 8".

Dayton Quatro 8" in TH ranging in volume from 100 - 150L. Is there any preference for hometheater? I have 2 more sims to come of the same driver. The sims are in order of smallest volume to largest.
Attached Images
File Type: png dayton_quatro_qt-4_8.png (67.0 KB, 903 views)
__________________
Killjoy or is it Chipsahoy
  Reply With Quote
Old 18th January 2008, 07:26 PM   #1018
Killjoy is offline Killjoy  United States
diyAudio Member
 
Join Date: Apr 2007
Default More Sims for Dayton Quatro 8"

Here are the other sims for the Dayton Quatro 8". These have the voltage turned up until the driver reaches x-max.
Attached Images
File Type: png dayton_quatro_qt-4_8 part ii.png (67.9 KB, 880 views)
__________________
Killjoy or is it Chipsahoy
  Reply With Quote
Old 18th January 2008, 07:41 PM   #1019
Killjoy is offline Killjoy  United States
diyAudio Member
 
Join Date: Apr 2007
Default Tang Band Comments

I tried changing the Qes from .3 to .4 on the 8" subwoofer and in the sims using Hornresp it starts looking pretty good. Would it be possible to adjust the Ques by varying the amplifier impedance as stated in this article:

http://sound.westhost.com/articles/cscaling.htm

If so then this driver may look something like this in a 117L TH:
Attached Images
File Type: png tang band w8-740p 8 inch.png (76.2 KB, 856 views)
__________________
Killjoy or is it Chipsahoy
  Reply With Quote
Old 18th January 2008, 07:44 PM   #1020
Killjoy is offline Killjoy  United States
diyAudio Member
 
Join Date: Apr 2007
Default Ciare 15 W2 TH

I'm going crazy with all of these nice looking results. Would this be relatively easy to x-over?

I forgot to change the Rg = 0.10 but I didn't notice much difference in my other sims when I made the change so maybe this is still valid.
Attached Images
File Type: png ciare 15 w2.png (79.4 KB, 749 views)
__________________
Killjoy or is it Chipsahoy
  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



New To Site? Need Help?

All times are GMT. The time now is 05:05 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