sealed vs. ported - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

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 5th May 2005, 06:18 PM   #1
sonu is offline sonu  India
diyAudio Member
 
Join Date: Apr 2004
Location: maharashtra
Default sealed vs. ported

Please help me which could perform better between the two drivers & why (explained) for pro use,

Thiele Para of driver 1- 18" Driver - 8Ohms
FS- 31.38
VAS - 14.44 L
Qes - 0.849
Qms - 9.809
Qts - 0.781
SD - 190 in^3
Inductance - 1mH
Power Handling - 800W

Thiele Para of driver 2 - 18" Driver - 8Ohms
FS - 23.17
VAS - 118.3 L
Qes - 0.408
Qms - 5.538
Qts - 0.380
SD - 170 in^3
Inductance - 2mH
Power Handling - 600W

As simulated in WINISD the first driver shows its best to be used in sealed, but can i use it as ported, if yes what would be the disadvantages of using the driver recommended for sealed, is used as ported enclosure.

The first driver is tested in a 2.8Cu ft sealed enclosure, it has a very good clean tight bass
  Reply With Quote
Old 5th May 2005, 06:35 PM   #2
diyAudio Member
 
Join Date: Jan 2004
Location: Toronto, ON, Canada
A Vas of 14.4L?
  Reply With Quote
Old 5th May 2005, 06:40 PM   #3
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
Resonance Frequency (Fs), Q of the resonance peak (Qts) and Volume of Air Equivalent to the Suspension Compliance (Vas) are the key parameters to how it will sound. Linear Excursion (Xmax), Surface Area (Sd) and power will give you an indication of how loud it will go.

The first drive unit I would guess is cheap as Qts is high. There is no way it will work in a vented box. I am certain that the value you have given for Vas is wrong as it's far too low for that size of drive unit.

The second drive unit can be used in either a vented or sealed box as Qts is about a medium value. I'd choose a vented cabinet as it would get a bit deeper and louder, but the box will be a bit larger and harder to make. Fs is low so bass will be fairly deep. Again though, Vas looks on the low side.

I would recommend measuring the parameters yourself once you get the drive unit as they can differ a bit because of tolerances and you can't always trust how well the manufacturer measured them.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  Reply With Quote
Old 6th May 2005, 09:56 AM   #4
sonu is offline sonu  India
diyAudio Member
 
Join Date: Apr 2004
Location: maharashtra
I HAVE READ THAT ONE SHOULD AT LEAST RUN THE DRIVER FOR HALF AN HOUR TO FREE THE SUSPENSION BEFORE MEASURING THE DRIVER.

The parameters given are tested by me with SW. The magnet design for the first driver is a T yoke design with fem, 1.7T in the gap, how can we get the BL.
  Reply With Quote
Old 6th May 2005, 10:21 AM   #5
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
To break in, half an hour is not enough IMO, a few hours is needed.

I think your method of measurement of calculation of Vas is going wrong somewhere. Both those figures are too low, one massively so.

You can measure Bl by applying an accurately known weight to the cone and measuring how much current is needed to bring the cone back up to the original position, then plugging this data into a formula. I'd concentrate on getting your basic parameters right first though.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  Reply With Quote
Old 6th May 2005, 10:29 AM   #6
sonu is offline sonu  India
diyAudio Member
 
Join Date: Apr 2004
Location: maharashtra
I am testing the driver with a 2.8Cu ft sealed box.
Is there anything you can suggest to as how to know if it is correct.
  Reply With Quote
Old 6th May 2005, 11:14 AM   #7
diyAudio Member
 
ashok's Avatar
 
Join Date: Jun 2002
Location: 3RS
Default Driver 1 .....

Hi Sonu,
What make is that driver No1.
Fs about 31Hz and Qts of 0.78 . Are you sure it is 0.78 .
Where in Mumbai is it available and how much did it cost ?
Thanks,
Ashok.
__________________
AM
  Reply With Quote
Old 7th May 2005, 01:38 PM   #8
sonu is offline sonu  India
diyAudio Member
 
Join Date: Apr 2004
Location: maharashtra
Ashok its made by me, with a T-Yoke and 30mm deep magnet structure to get good Xmax, Coil design- 35mm length and achieved a lower inductance of 1mH, and tested it with 600W, continious load for 2Hours.
I have tested it in my sealed test box of 2.8Cu ft, its performance is ultimate, but i dont know how good is the performance by knowing the thiele para (like in previous message by richie00boy a high value of QTS is not good). IS IT THAT A HIGHER Total Q VALUE IS NOT GOOD, and I thought higher Q is better.
The gap is also very tightly set, and as per my knowledge it's should definately perform in its best.

Can you please help me how to interpret about the design by the thiele para's.
i.e. - What effects the VAS, Qms, Qes,
  Reply With Quote
Old 7th May 2005, 01:57 PM   #9
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
High Qts is bed because it indicates poor inherent damping within the driver. So high Qes is poor electrical damping and high Qms is poor mechanical damping.

You might like to read through the papers by Thiele and Small on my website www.readresearch.co.uk in the 'papers' section.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more.
  Reply With Quote
Old 7th May 2005, 01:57 PM   #10
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Sonu:

You're basically asking for a course in loudspeaker building.

For the engineering minded, the basic parameters and what affects them are explained in the papers by Aussies Richard Small and Neville Thiele-these are the famous Thiele-Small papers from which we get the famous Thiele-Small parameters.

As stated previously, Richie00boy has these papers downloadable for your convenience at his wonderful website:
http://www.readresearch.co.uk/

If you want to know how the Thiele-small parameters work together, an excellent explanation is given by David Weems in his excellent book Designing, Testing and Building Loudspeakers. It is written for the complete novice to get him started, but the explanations are great.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  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
Sealed vs. ported... and what their relationship to BSC is? fjhuerta Multi-Way 0 30th August 2005 04:50 PM
Sealed or ported? mazeroth Subwoofers 13 23rd November 2004 12:44 PM
¿Sealed or Ported? eXn Car Audio 28 11th October 2004 11:05 PM
opinions of T/L box V ported OR sealed busterno1 Multi-Way 13 28th November 2003 08:20 AM
Ported mains / Sealed sub Javaman Multi-Way 3 27th December 2001 09:56 PM


New To Site? Need Help?

All times are GMT. The time now is 06:23 PM.


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