Unconventional subwoofer design - 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 17th December 2003, 03:54 PM   #11
BAM is offline BAM
diyAudio Member
 
Join Date: Sep 2001
Location: Carmel, IN; West Lafayette, IN
Send a message via AIM to BAM
The whole deal with this particular thing is that when you try and use larger woofers, like 8" or 10" or 12", you wind up with a refrigerator-sized box. I want to try and fit this at least into the space of a large suitcase. It will be powered with 150 watts. The woofers on their own each have a power handling of 150 watts and an impedance of 8 ohms. Used in parallel, they should suck the entire 150 watts from the amplifier. The woofers also have decent sensitivity, though (88dB 1w/1m). This will all add out to 91dB 1w/1m. I am actually now thinking of building some MTM satellites for it with some 12-ohm 4" things I have laying around.

One question about the readings you got with Isaac's subwoofer simulator. Does that mean that my 6.5" woofers in this box will actually be able to reach down below their Fs to the 20Hz F3 that it is predicting? I might model up one for myself and change it to see that the lowest frequency it tries to do is 35Hz and extend its possible range up to 200Hz.
  Reply With Quote
Old 17th December 2003, 09:27 PM   #12
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Quote:
Originally posted by BAM

One question about the readings you got with Isaac's subwoofer simulator. Does that mean that my 6.5" woofers in this box will actually be able to reach down below their Fs to the 20Hz F3 that it is predicting? I might model up one for myself and change it to see that the lowest frequency it tries to do is 35Hz and extend its possible range up to 200Hz.
Well, the 1 Watt curve will be -3 dB down at 19 Hz or so. BUT at 19 Hz, the cone excursion for your 6.5" is 23mm!

Actually, TC Sounds makes a 6.5" that will be linear at 23 mm. Only trouble is, they mostly sell Original Equipment Manufacturers, so you have to locate which manufacturer uses it. I hear Styke sells ome of TC Sounds speakers, so you might look there as well.

Assuming a normal excursion of ±6mm or so, plus a little added for nonlinear travel, you still fall far short. Even if you double it for 2 woofers.



If you don't mind my saying so, I don't think being able to put out 101 dB at 19 Hz is such a great idea. You will need more SPL than that to make going down that low worthwhile, even with room gain. I would definitely move the F3 upward for greater sensitivity, greater output and less cone excursion.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 17th December 2003, 09:33 PM   #13
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
A couple of questions.

First, what would you call the size of a large suitcase-2 or 2.5 cu ft?

Second, are we still on the idea of using two 6.5 inchers? Because two 6.5 inchers will have about the same deal as one 10 incher, and the 10 incher will likely have greater excursion.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 17th December 2003, 09:44 PM   #14
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Oops! TC sounds no longer makes the 6.5"

They do make an 8" though. Small Vas for it's Fs of 29 Hz. It looks interesting if you are into making a sub that will fit into even a small suitcase.

Check out the woofer:
http://www.tcsounds.com/Images/8tc2_2574.pdf

Check out TC Sounds:
http://www.tcsounds.com/

AS far as getting your hands on one-that might take some doing. You might want to make that a separate thread.


PS: that peerless 6.5" does NOT have a shorting ring or extended pole piece. That means it might hit high distortion as it nears resonance, as non-symmetrical magnetic field speakers do as they near resonance. This might mean trouble, since this box has three resonance points, not just one.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 18th December 2003, 01:31 AM   #15
BAM is offline BAM
diyAudio Member
 
Join Date: Sep 2001
Location: Carmel, IN; West Lafayette, IN
Send a message via AIM to BAM
The single 10-incher will give me a refrigerator in my room, while the 6.5's will not. Something about the moving mass of the cones or some other characteristic specific to smaller drivers, I think. I am trying to get this to fit under an end table that my parents have. Bose seems to get away well with the most plain-vanilla 5.25" drivers I have yet seen, so I think that the Peerless 6.5" drivers will give me what I am looking for. They seem to model out into reasonable box sizes. I am setting my size limits at about 3 feet (36") deep, 20" high, and 12" wide. If I can realize an enclosure smaller than that, with single 3" ports connecting the chambers, then I will. Lowest frequency I am trying to reach with these drivers is 35 Hz. I am building this for the heck of it, and I am going to build some satellites for it with some drivers that have been sitting under my bed back at home (I am at college) seemingly forever waiting for a use. Into the back of the 8th-order box I will be building in my 150-watt subwoofer plate amp, for a powered apparatus. The third port to the outside will be a flared Precision Port kit. There's my agenda. As far as driver distortion, I am expecting that any of that will be contained within the acoustic chambers, for the kind of distortion-killing effect that Bose touts so highly. You will notice I am not trying to get that low. When I want that kind of low bass, I will listen to my vented 500W AV12-equipped subwoofer, which I am predicting to have a possible F3 of 16 Hz with three 3" flared ports.
  Reply With Quote
Old 18th December 2003, 04:38 AM   #16
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
BAM:

Two things:

A) I know you are aware of the other thread on this subject.
High Excursion 8 Inch Woofer. Is Their Such A Beast?

I just wanted to reiterate about the symmetrical magnetic field. It is not just a case of high distortion-the voice coil actually displaces from moving back and forth from the centerpoint to going all the way to the end of it's travel. This shears off half the waveform in a ported box. The eighth order bandpass consists of 3 ported chambers. Draw your own conclusions.

B) Your dimensions for this box, (36" X 20" X 12"), with one inch building material, translate into 3.5 Ft³. That is one large enclosure. Are you sure you want to go thru all this trouble with the eighth order bandpass sub?

A vented Shiva or even a sealed one-should give you all you need down to 35 Hz. You can parallel two vented Peerless 10" CSX or CCC and get down to 35 Hz, with an efficiency of 91 dB and major excursion output.

It is your project and if you want it in the form of two 6.5's in an 8th Order Bandpass, that is great. Just thought I would let you know that there are a lot of less complicated alternatives out there.
__________________
"A friend will help you move. A really good friend will help you move a body."
-Anonymous
  Reply With Quote
Old 19th December 2003, 08:38 PM   #17
BAM is offline BAM
diyAudio Member
 
Join Date: Sep 2001
Location: Carmel, IN; West Lafayette, IN
Send a message via AIM to BAM
I know there are a lot less complicated ways of getting bass, and probably better bass at that. But I have never seen a DIY-built 8th-order bandpass subwoofer, and I want there to be at least one existing DIY 8-O bandpass design. Just like there is an existing design that uses Wave Cannon theory, I want to build at least one 8th-order bandpass. That is my whole motivation for this project. Otherwise I would have just built some sort of sealed 10" woofer. My whole aim in this, though, is to make sure that my 150-watt plate amplifier dies not sit idle.

I am actually putting this project on hold until the summer, I think. I want to make some money and perhaps use those new Elemental Designs midbasses that they are coming out with. They are 6.5" paper cones with 13mm one-way Xmax. they use foam surrounds, though, so that is bad. Perhaps I will try the Adire Extremis midbasses, if they are in a decent price range.
  Reply With Quote
Old 19th December 2003, 09:10 PM   #18
f4ier is offline f4ier  Australia
diyAudio Member
 
f4ier's Avatar
 
Join Date: Sep 2001
Location: Sydney
I built an 8th-order box, long before I knew enough for SubSim's conception. It used a cheap chinese-made 8" woofer. This was in the early 90s, so I can't remember the tuning frequencies, and surely the driver unit wasn't a match for the enclosure.

This type of enclosure does require a capable woofer. The one I made had a glass panel so I could see the cone excurssion. The cone movement is so small that the voice-coil vent is almost useless. The driver easily runs into thermal overload rather than mechanical overload.

A 30Hz signal at 100Wrms was just too much that it fried the coils within seconds. I could smell and see the smoke vibrating in and out of the main vent. It was loud while it lasted, kinda cool actually

The fun of construction and hearing the unconventional design was all I wanted out of the whole thing


Cheers,
Isaac
__________________
Crossover/Subwoofer Simulator
  Reply With Quote
Old 20th December 2003, 03:31 AM   #19
diyAudio Member
 
paulspencer's Avatar
 
Join Date: Sep 2003
Location: Melbourne, Australia
Bam,

There is nothing wrong with foam at all from a performance point of view. In many ways it is ideal, I think it is actually better than rubber. Adire discuss in their whitepaper on the Shiva the reason for using foam surround. The only issue is longeivity in some areas. My parents have a pair of old boom boxes that are 20 years old and now they are starting to fall apart. But I have seen the same thing with rubber surrounds as well. In 20 years time you probably will have passed it on anyway. Most here have a much quicker turnover of their speakers than that!!!

regards,
Paul
  Reply With Quote
Old 28th December 2003, 04:52 PM   #20
Wizard of Kelts
diyAudio Moderator
 
Join Date: Sep 2001
Location: Connecticut, The Nutmeg State
Quote:
Originally posted by f4ier
I built an 8th-order box, long before I knew enough for SubSim's conception. It used a cheap chinese-made 8" woofer.

This type of enclosure does require a capable woofer. The one I made had a glass panel so I could see the cone excurssion. The cone movement is so small that the voice-coil vent is almost useless. The driver easily runs into thermal overload rather than mechanical overload.

A 30Hz signal at 100Wrms was just too much that it fried the coils within seconds. I could smell and see the smoke vibrating in and out of the main vent. It was loud while it lasted, kinda cool actually

Cheers,
Isaac
In that case, I would point out that the Eminence LAB 12 was designed for horn enclosures, where cone excursion is suppressed as well. Therefore, it would appear to be a good match for this type of enclosure as well.

Although it does not fit the size or price goals for this project, I thought I would just throw this in just in case you decide to build one of these with a bigger budget.
__________________
"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
Help in subwoofer design. pmkierst Subwoofers 25 2nd February 2009 07:50 PM
DIY unconventional speaker stands monstertrucker Multi-Way 9 27th September 2008 03:04 AM
12'' Subwoofer box design marinbnm Subwoofers 4 14th November 2007 08:44 PM
Subwoofer crossover / subwoofer module design derMichi Subwoofers 4 20th April 2006 10:31 AM
Unconventional & inexpensive bracing techniques morbo Subwoofers 26 2nd September 2005 09:21 PM


New To Site? Need Help?

All times are GMT. The time now is 08:29 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