Critically Damped (Q=0.5) Subwoofer - Page 2 - 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 18th November 2003, 02:17 AM   #11
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Quote:
Originally posted by tktran

How can this be detrimental to sound quality? I had always thought that a subsonic filter is a "good thing"
Tktran:

It is a principle of audiophiles that the less processing you put in the circuit, the truer it is to the original signal, therefore better.

A subsonic filter probably introduces phase distortions, etc,. so an audiophile might leave it out.

The funny thing is, the subsonic filter might be more useful to many audiophiles than to AV fans! That is because many audiophiles still play vinyl records. If there is a warp in the record, the subsonic energy can be huge. DVD's and such have not such outrageous subsonic output.

As in all things, you use your judgement. A subsonic filer would likely be left off by audiophiles unless they play vinyl.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 19th November 2003, 12:00 AM   #12
diyAudio Member
 
mikee12345's Avatar
 
Join Date: Nov 2002
Location: NZ
So u limit the response with Qtc=0.5,then EQ it back....seems self defeating excursion wise.


i dont enjoy EQing sealed boxes. for that reason.

why not DAMP the woofer with a port,then u wont need EQ ,its damped already

Sure the Qtc=0.5 box with EQ may sound better,but has limited SPL

  Reply With Quote
Old 19th November 2003, 01:53 AM   #13
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Quote:
Originally posted by mikee12345


why not DAMP the woofer with a port,then u wont need EQ ,its damped already
Mikee:

I personally favor the ported box/passuve radiator. Nevertheless, the closed box aficionados have a satisfactory answer to your question.

At or near resonance, the closed box has much cleaner step response than the bass reflex. If you survey the step response in the thread I gave you before, you should know that that the cleanest ported box's ressponse is worse than a sealed box with a Qtc of 1.3. The "classic" bass reflex, where Vas=Vb, and Fb=Fs=F3, has step response worse than a closed box with a Qtc of 1.6.
Click the image to open in full size.

The whole idea of the article is to give the builder a subwoofer with bass that is under control without the use of an expensive servo mechanism. Either the parameters of the Peerless changed or something happened, because he ended up giving a box with a Qtc or 0.4 instead of 0.5. But even with that fact, the subwoofer he outlines will give extremely clear, controlled bass. There is not that much difference between a subwoofer with a Qtc=0.4, or Qtc=0.5.

A ported or passive radiator will give more bass output. Just not as clean.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 19th November 2003, 03:04 AM   #14
tktran is offline tktran  Australia
Account Disabled
 
Join Date: Mar 2003
Location: Perth
I received an email from Joe, stating that it's important that I understand that it's not suitable for home theatre. He even uses two in his music room.

Thanks Kelticwizard, I am rethinking my subwoofer choice, simply because I'd like a bit of flexbility.

A sub to fill out the bottom end with classical music, thump with club/techno music and rumble with the best of 'em when it comes to blockbuster action movies.

I also have two rooms, a HT room 4 x 5m and I'd like to try it in the family room, 6 x 8m and opens out into the kitchen (L shaped)

So I will start with the Shiva... and build the 54L box according to Adire's plans.

Then if I feel I need more grunt I can also try their ported designs.

Will be using the same amp specified by Joe:

http://www1.jaycar.com.au/productVie...Max=&SUBCATID=

Would the shiva benefit with the peaky 30Hz boost?

http://members.ozemail.com.au/~joera..._technical.htm
  Reply With Quote
Old 19th November 2003, 03:34 AM   #15
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Or else you can use the Peerless, put a 4" diameter port with a screwable end cap-available at any home improvement store-and make yourself a convertible sub. Sealed for music, ported for home theater.

The closable port will be 33" long. box volume will be 50 liters, including the port.

You can do it.

Here is the simulation, woofer driven at 28 volts, (196 watts into 4 ohms)

The red line, lower, is the half space response vented.
The red line, upper, is the vented reponse with room.

The white line, lower, is the sealed response inhalf space.
The whitle line, upper, is the sealed response with room

Quite an improvement, don't you agree?

Nothing wrong with the Shiva, just showing you options.
Attached Images
File Type: gif peerless 830500 convertible.gif (27.8 KB, 547 views)
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 19th November 2003, 03:48 AM   #16
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Incidentally, the Shiva in a 50 liter box will have a final Qtc of 0.78. Here is the chart and you can see how that compares to a Qtc of 0.5. It won't be hard to extrapolate between 0.7 and 1.0.
Attached Images
File Type: gif response shapes qtc.gif (5.4 KB, 431 views)
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 19th November 2003, 03:59 AM   #17
tktran is offline tktran  Australia
Account Disabled
 
Join Date: Mar 2003
Location: Perth
Wow a 33" port? How will that fit into a 50L box???
  Reply With Quote
Old 19th November 2003, 04:10 AM   #18
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Incidentally, over in Australia, I don't know how much the Shiva costs compared to the US.

There is an alternative.

Eminence makes the LAB 12, which has a bigger magnet but otherwise has Thiele-Small specs almost identical to the Shiva. It also has a much larger magnet, and a single 6 ohm voice coil. Oh yes, the Lab 12 has a cast frame where the shiva has a stamped frame. However, I have always felt that a well-designed stamped frame is just a sgood as a cast one. Nevertheless, most believe a cast frame is an upgrade over a stamped frame.

Here in America, the LAB 12costs about $50 more than the Shiva. However, I don't know what the price is over in Australia. Eminence has a destributo in Australia, and Eminence tends to charge the same proce for their speakers worldwide. So the LAB 12, in Australia, might end up being cheaper than the Shiva.

Here is the Eminence page for the LAB 12:
http://www.eminence.com/eminence/pag...ab12/lab12.htm

Here is your Australian distributor:
http://www.eminence.com/eminence/pag...nquiry/aus.htm


Again, just an option to consider.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 19th November 2003, 04:12 AM   #19
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Quote:
Originally posted by tktran
Wow a 33" port? How will that fit into a 50L box???
PVC elbows, available at any home improvement store.

It's longer than I'd like, but it's possible.

Actually, a 33 inch port might have a quarter-wave resonance at 102 Hz. Maybe that isn't such a great idea.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 19th November 2003, 04:22 AM   #20
tktran is offline tktran  Australia
Account Disabled
 
Join Date: Mar 2003
Location: Perth
The Shiva currently costs AU$300, the equivalent of USD$210 from the sole Australian distributor.

The 830500 costs this same price from Australia's official Peerless distributor, or about 190 USD elsewhere.(Peerless / Vifa/ Scanspeak are easier to find)

Thanks for the tip- I'll investigate the Lab12 in Oz.

Bob Stout's Loudspeaker Selection Guide quotes the 830500 as only really being suitable for PR box, so the Critical Q subwoofer had me interested, as does Linkwitz's Thor subwoofer.

Incidentally he also measured the Shiva (Mk1/2?), and if i read between the lines correctly, implies that it's not as good as the 830500. As least for his application (dipole bass)
  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
Do Old Timers listen more critically? Shaun Everything Else 5 8th April 2008 11:43 AM
CD Player: DIY Foam Damped Spring Feet $8.00 x-pogo Digital Source 0 7th January 2008 07:17 PM
Damped (lossy) BR ports Pjotr Multi-Way 36 13th September 2006 06:44 PM
Somebody damped that discussion over here Fred Dieckmann Everything Else 17 23rd July 2003 10:01 PM


New To Site? Need Help?

All times are GMT. The time now is 11:53 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