Mr. Potatoehead Open Baffle - diyAudio
Go Back   Home > Forums > Loudspeakers > Full Range
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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 April 2016, 04:15 PM   #1
diyAudio Member
 
mr2racer's Avatar
 
Join Date: Jul 2009
Default Mr. Potatoehead Open Baffle

Hey Anyone,

This thread is for an easy, inexpensive open baffle design. That has NO scientific mathematical model. I want to assemble it from some parts I already have and one I need to buy. It is an open baffle mini speaker. The woofer is a Tymphany LAT 250 bass driver. The upper frequencies will be handled by a Vifa TC9FD 3 1/2" full range driver. The Vifa will be mounted on a trapezoidal baffle like the one pictured. (Just because it looks cool.) The crossover will be a Parts Express subwoofer crossover. Its an 8 ohm crossover at 150hz. (I would probably upgrade the caps in the crossover.) The LAT has two 4 ohm voice coils on either end of the assembly. I intend to run the LAT voice coils in series out of phase with each other. One pushes the other pulls. OR pad the woofer to match the low efficiency of the full range and raise its impedance.

Any thoughts?
Attached Images
File Type: jpg Mr. Potatoehead Open Baffle.JPG (50.2 KB, 859 views)
__________________
Artificial intelligence is no match for natural stupidity- Red Green

Last edited by mr2racer; 17th April 2016 at 04:28 PM.
  Reply With Quote
Old 17th April 2016, 09:10 PM   #2
diyAudio Member
 
Godzilla's Avatar
 
Join Date: Nov 2005
Location: New York
I think it will work good enough.
__________________
Vive la musique!
My blog: https://speakerprojects.wordpress.com
  Reply With Quote
Old 17th April 2016, 10:24 PM   #3
diyAudio Member
 
Join Date: Mar 2007
Location: California
Cool looking or not, this speaker design (as stated) has a serious flaw. Because of the response from the open baffle, the higher frequencies will be something like 6+dB louder than the upper bass with a peak around 1kHz and then a roll off below that at 6dB/oct. This assumes that the driver has infinite low extension, so any droop from the driver itself needs to be added on top of the baffle response.

Adding the woofer below 150 Hz won't really make up for the response hole that you will have between 200Hz and 800Hz (about 3 octaves). Unless you can cut the peak at 1kHz and correct for the drooping response of the OB you will not get very accurate sound from this speaker. This can certainly be done, but you will need more circuitry than the crossover that you mentioned.

I simulated the response you will get if the TC9 is mounted in the baffle shape you pictured and attached it for reference.
Attached Images
File Type: png small_OB_response.PNG (38.3 KB, 780 views)
__________________
Visit my Audio Web Page <<--CLICK TO LEARN MORE-->> Get my LADSPA plugins
  Reply With Quote
Old 18th April 2016, 12:24 AM   #4
diyAudio Member
 
mr2racer's Avatar
 
Join Date: Jul 2009
So what would be a better baffle design? I would need a neutral baffle yes?
__________________
Artificial intelligence is no match for natural stupidity- Red Green

Last edited by mr2racer; 18th April 2016 at 12:31 AM.
  Reply With Quote
Old 18th April 2016, 12:47 AM   #5
diyAudio Member
 
Join Date: Mar 2007
Location: California
Quote:
Originally Posted by mr2racer View Post
So what would be a better baffle design?
There is a relationship between the baffle response and the largest dimension (width/height) of an open baffle that controls where the "peak" in the response is located and where the response starts to fall off (below the peak). Larger baffles move the peak lower and smaller ones move it higher. When smaller drivers are put on larger baffles the first peak can become a series of two or more peaks (with troughs in between) that have decreasing amplitude as the frequency increases. You can read more about this topic here. A related phenomenon happens for closed/ported boxes and is called the "baffle step".

Basically, there isn't much that can be done about this - it's due to the physics of the open baffle front and rear wave interacting with each other. You have to work with what you get and plan the crossover, and use other drivers in the system, to get a flat response. This is why open baffle systems often use more drivers that you can get away with using a closed box or even a TL type system. As a result, the crossover is also more complicated.

For some examples of OB systems that sound good, you can check out Manzanita Audio Solutions. In one system, the designer uses a full range driver (think TC9) and a couple of larger high Q woofers in a larger floor standing open baffle. A very large inductor is used to compensate for the open baffle roll off, and a custom passive networks takes care of the rest. This can sound great, so if you can pick up four inexpensive higher Q woofers like these you might be able to try it yourself. If that design is too large, there is a smaller CV version with only one woofer that has less bass capability. You will need a pretty good woofer for the CV version (I have a hunch that the Peerless 12" SLS is used) - there is only one woofer and the baffle is much smaller, so the bass response is quite far down in SPL compared to 1kHz and above. All of these systems are rather low sensitivity so power on the order of 100W is a good idea.
__________________
Visit my Audio Web Page <<--CLICK TO LEARN MORE-->> Get my LADSPA plugins

Last edited by CharlieLaub; 18th April 2016 at 12:50 AM.
  Reply With Quote
Old 18th April 2016, 05:55 PM   #6
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Maybe you should not go open baffle but out a sealed back like the Nautaloss that the above trapezoid was used in. That will give you the following measured response for the TC9FD:
Click the image to open in full size.

More info here: An Objective Comparison of 3in - 4in Class Full Range Drivers

The OB doesn't buy you anything but loss of bass efficiency and extra complexity of having to deal with that OB response that CharlieLaub simulated.

Put it in a trapezoid backed with a Nautaloss "infinite baffle" and you get almost monitor flat response. There is a rise around 2.5kHz that is baffle related but some people like this enhanced "presence".

I would suggest a higher XO around 400Hz to 500Hz. High pass the TC9 to relieve it from too much cone excursion.

You can also get 6 of the $5 polycone woofers from PE and make a SLOB - it sounds very nice and reaches quite low (40hz if I recall).

Here is the measured SLOB response but I had active filters applied.

Cheap and FAST OB, Literally

Click the image to open in full size.
Click the image to open in full size.
Here is a TC9 and SLOB:

Last edited by xrk971; 18th April 2016 at 06:04 PM.
  Reply With Quote
Old 20th April 2016, 01:46 AM   #7
diyAudio Member
 
mr2racer's Avatar
 
Join Date: Jul 2009
Anyone know where I can get the plans for the Nautaloss?
__________________
Artificial intelligence is no match for natural stupidity- Red Green
  Reply With Quote
Old 20th April 2016, 02:13 AM   #8
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Metro DC area
Nautaloss thread. Just a spiral sealed TL. Match the volume to about 1/2 Vas to 1 Vas of driver to give it enough breathing room for bass generation. If you will be using it as mid and higher with very low excursion, smaller volumes work. Similar to Nautaloss is Dagger sealed TL. Just straightened out 3 sided pyramid. No parallel surfaces.

Nautaloss:

The Nautaloss Ref Monitor

Dagger:

FAST with TL?
  Reply With Quote
Old 20th April 2016, 07:33 PM   #9
diyAudio Member
 
Join Date: Mar 2007
Location: California
Quote:
Originally Posted by xrk971 View Post
The OB doesn't buy you anything but loss of bass efficiency and extra complexity of having to deal with that OB response that CharlieLaub simulated.
This is not really accurate. If the only thing you got out of an OB system was less bass output and more frequency response irregularities no one would be building them.

Some of the benefits of an OB are: a completely different radiation pattern compared to boxed speakers, a relative lack of panel resonances, a different way to interact with the room and a different way that the room modes are excited, and the possibility for very smooth off-axis response that has a very similar energy content compared to the on-axis response. The last effect listed means that the sound energy that is returned to the listener after interacting with the room will be much like the direct sound, just delayed. The result can be an exceedingly spacious sound stage, and one that remains the same over a wide listening area, if the OB is done right.
__________________
Visit my Audio Web Page <<--CLICK TO LEARN MORE-->> Get my LADSPA plugins
  Reply With Quote
Old 20th April 2016, 07:53 PM   #10
chrisb is offline chrisb  Canada
diyAudio Member
 
Join Date: Aug 2002
Location: victoria BC
On their attributes aside OBs definitely have their own issues, both in terms of achieving anything approaching full bandwidth reproduction, and also in fitting into the type of spaces that many of us have available. I know I sound like a broken record on the subject, but even those of us with decent enough sized rooms, not all are able to dedicate them to classes of speakers with heavy demands on "real estate" and or acoustic treatment.
__________________
... so, not as easy at it sounds, this letting go thing
  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
Open baffle or no baffle for nearfield full range monitors? mdevelde Full Range 19 18th November 2016 05:26 PM
Does open baffle suffer from baffle step? 454Casull Multi-Way 15 19th May 2012 04:12 PM
Upwards aligned open baffle? ( pop box meets open baffle ) OllBoll Full Range 3 28th March 2011 02:00 AM
what effect does baffle have on open-baffle system? kappa546 Multi-Way 6 24th January 2006 11:21 PM
Australians- what solid timbers for baffle? (open baffle loudspeaker) tktran Multi-Way 13 30th November 2004 12:09 AM


New To Site? Need Help?

All times are GMT. The time now is 01:52 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2016 DragonByte Technologies Ltd.
Copyright 1999-2016 diyAudio

Content Relevant URLs by vBSEO 3.3.2
Wiki