6" and below that moves the most air regardless of quality - 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 19th November 2012, 07:50 AM   #1
diyAudio Member
 
Join Date: Nov 2012
Default 6" and below that moves the most air regardless of quality

So this is probably a bit of an usual setup, as it's not meant for sound quality. I'm trying to make a model that sinusoidally sucks/blows out of a slot for an experiment.

Basically what I'm after is a 6" (or below, smaller the model is, the less air I need to displace..) subwoofer that has a large excursion (and capable of low freq, below 20Hz). I'll just be putting a sinusoidal voltage through the woofer at various (manually controlled with a signal generator) frequencies and amplitudes to get a desired (sinusoidal) velocity output. So i'm not concerned about how the woofer will react to rapidly changing frequency inputs etc.

Does anyone have any suggestions as to what woofers would be up to the task? The best woofer that I've found so far with the largest excursion is this ScanSpeak (here). It's got a max mechanical excursion of +-13mm - so theoretically capable of displacing 240cm^3 of air (Effective piston area of 92 cm^2).
Am I correct to assume that I could make any woofer beat at a low frequency provided I input a high enough voltage (without the whole thing burning out of course) at the low frequency?

Any help would be greatly appreciated!
Cheers.
  Reply With Quote
Old 19th November 2012, 09:19 AM   #2
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
I am not sure what you are trying to accomplish but I had cooked one of my 8" subs on a free air excursion test.
The Optimus PRO-CSW800 has very similar specs,

http://www.manualslib.com/manual/137...?page=3#manual

I was able to observe its actions at 10hz or so for a very short time, only a few seconds and I burned the voice coil before I could get to the volume control to turn it down and let it cool off!!!
I think I was using my Ashley FTX-2000 if there is any question of how much power I was driving it with.

That is a very expensive driver to be pushing like that.

I do not know how much voltage I was applying as I didn't have my scope hooked up at the time.
But it was doing every bit of its possible excursion and was making very little mechanical noise.
Sadly there was just not enough air movement to keep the voice coil cool enough and too keep it from burning up.
Luckily I was only out about $15 only they can't be found any more.
I had 8 of them and now I have 7.

This driver from MCM is similar to the 8's that I have,

MCM Audio Select 8'' High Excursion Woofer - 120W RMS 4ohm | 55-2421 (552421) | MCM Audio Select

MTX had a driver with the exact specs of my Optimus driver but I don't remember the model number at the moment,But sadly it has been discontinued as well.

I am sure there are many other cheaper drivers that you could use for such an abusive tests.

Unfortunately subs with those types of specs are very expensive in the 5" to 6" diameter range.
I know as I have been doing some searching myself for one that size.

I would hope that the Scanspeak has an extremely low THD for that kind of money.
Even if it did I still couldn't justify the cost for a small driver like that.
When it comes to SPL's and low frequency's, Displacement is the main thing that rules.
For the same SPL's at an octave lower the drivers excursion must increase by a factor of four.

Here is an online calculator that I hope you will find useful,

http://www.baudline.com/erik/bass/xmaxer.html


FWIW

jer

Last edited by geraldfryjr; 19th November 2012 at 09:43 AM.
  Reply With Quote
Old 19th November 2012, 11:03 AM   #3
NEO Dan is offline NEO Dan  United States
diyAudio Member
 
NEO Dan's Avatar
 
Join Date: Jun 2008
Location: N.E. Ohio
DIYCable.com : Intro Home Exodus Anarchy
__________________
Regards,
Dan
  Reply With Quote
Old 19th November 2012, 03:03 PM   #4
diyAudio Member
 
Join Date: Jan 2008
Quote:
Originally Posted by AUSBMX View Post
Am I correct to assume that I could make any woofer beat at a low frequency provided I input a high enough voltage (without the whole thing burning out of course) at the low frequency?
Blowing air out of a slot is pretty easy, I have seen "rooster tails" of sawdust blow six feet across the room using a Lab 12 with about 400 watts of sine wave below Fb. A paper ball will blow much further .

One thing to factor in is the AES figures used for most speaker rating now use a compressed pink noise source with -6dB crest factor.
Sine waves have a -3dB crest factor, so if you plan on long term usage, you need to use at most -3 dB (half) the AES power figure.

Depending on power compression and cooling (a back vented coil cools more at low frequency, longer "fan") you may be able to increase level over half the AES figure, but the only way to find out how much is too much is to slowly increase level until the coil burns.

Usually, the adhesives start to stink badly before the coil goes...

Art
  Reply With Quote
Old 19th November 2012, 07:09 PM   #5
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

Why is the size of the model related to the slot size ?

Have you modelled turbulence to see if your air flows are realistic ?

rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
  Reply With Quote
Old 20th November 2012, 04:18 PM   #6
diyAudio Member
 
Join Date: Jan 2011
The tang band 6.5's have a lot of excursion and a large rubber surround.

Cheap Tang Band mini Horns are back!
  Reply With Quote
Old 20th November 2012, 04:41 PM   #7
diyAudio Member
 
Shadydave's Avatar
 
Join Date: Jun 2012
Location: Appalachia, in the middle of nowhere.
AUSBMX,
If you do this, you should use a momentary push button switch to connect the speaker.
That way you will be aware of how long you have the speaker on the verge of frying.
It only takes a short time at low frequencies to burn the voice coil.

Dave
__________________
<---My Transmission Lines from a prior life...Top one Tweeter...Bottom one definitely a Sub
..In space, you can't hear my sub
  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
Air velocity 2 vent diamet 4" v length 10.1" joojoo1234 Subwoofers 20 8th November 2011 03:16 AM
Poor air quality... CBS240 The Lounge 13 5th December 2010 02:37 PM
EICO 666 meter needle moves too fast/pegs too hard...help? jasonguitar Tubes / Valves 3 15th September 2010 01:58 AM
Can anyone suggest the "best" 300B SE sound quality schematic for a beginner like me? calico88 Tubes / Valves 42 18th July 2006 02:33 PM
Free air 6" to 7" woofer Radik Multi-Way 3 1st January 2003 11:25 AM


New To Site? Need Help?

All times are GMT. The time now is 04:51 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