Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Cardioid Bass
Cardioid Bass
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 9th May 2008, 06:13 PM   #251
john k... is offline john k...  United States
diyAudio Member
 
john k...'s Avatar
 
Join Date: Aug 2004
Location: US
Hi Earl,

I did find a minor bug, but no big deal. The notch at 17 Hz for the monopolewas bugging me. Didn't make sense. The bug fix gets that out and corrects the dipole result as well. As I said I, I just threw this together. I can accept coding errors. They will get fixed.

A this point I don't have damping, and you are correct, it is a major concern. The first reference does show how to allow for nonzero admittance of the surfaces but I haven't worked through the details yet. I do have a FEM code that considers damping but I didn't write it and unfortunately it doesn't allow me to set up a cardioid source, not to mention that the procedure is very slow. I'm still working with the developer so hopefully at some time I can convince him to do cardioid. I'll keep pluging away. Something to do on a rainy day.
__________________
John k.... Music and Design NaO dsp Dipole Loudspeakers.
  Reply With Quote
Old 9th May 2008, 06:45 PM   #252
gedlee is offline gedlee  United States
diyAudio Member
 
gedlee's Avatar
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally posted by john k...
Hi Earl,
A this point I don't have damping, and you are correct, it is a major concern. The first reference does show how to allow for nonzero admittance of the surfaces but I haven't worked through the details yet. I do have a FEM code that considers damping but I didn't write it and unfortunately it doesn't allow me to set up a cardioid source, not to mention that the procedure is very slow. I'm still working with the developer so hopefully at some time I can convince him to do cardioid. I'll keep pluging away. Something to do on a rainy day.

You won't find the discussion in Morse and Ingard very illucidating.

Basically what is usually done is to ASSUME that the eigenmodes don't change. This is a reasonable assumption for light damping, but fails for large damping. Basically whet happens in the physics is that the modes share energy. In other words the energy in one mode leaks into adjacent modes through the damping. Tis is why damping at LF is such a good thing.

Then assume that only the Eigenvalue chnges, it becomes complex. The denominator has the eigenvalues squared. So expand the complex eigen values into real and imaginary parts. Discard the terms in the imaginary parts squared as these are small. The remaining complex term will have a real part times the damping value (the imaginary part). If you leave this like this you will find a strange thing happens because the damping will rise with frequency and the room will flatten way out at higher frequencies. I end up with

(i * kn * pi *c - eta)^2 for the denominator eigenvalue squared, where eta is the damping, assumed small, usually about 20 in english units. This works pretty well. Any other approach that I have tried yields very strange results.
__________________
Earl Geddes Gedlee Website
  Reply With Quote
Old 10th May 2008, 07:45 AM   #253
Graham Maynard is offline Graham Maynard  United Kingdom
R.I.P.
 
Graham Maynard's Avatar
 
Join Date: Dec 2003
Location: UK
Comments made here by Lynn Olson would also relate to EQed dipole+monopole 'systems' generated cardioid bass.

http://www.diyaudio.com/forums/showt...2&goto=newpost


Cheers .......... Graham.
  Reply With Quote
Old 10th May 2008, 11:05 AM   #254
john k... is offline john k...  United States
diyAudio Member
 
john k...'s Avatar
 
Join Date: Aug 2004
Location: US
Quote:
Originally posted by gedlee



You won't find the discussion in Morse and Ingard very illucidating.

Maybe I am missing something but they seem to present a very straight forward discussion for the corrections to the eigenfunctions and eigenvalues for small admittance. So if I assume that the wall admittance is small but real, then energy is lost to the wall and that should provid the damping, no? As you note, the eigenfunctions don't change much for small admittance so initially I will not alter them. It becomes a matter of how the eigenvalues in the denominator change.
__________________
John k.... Music and Design NaO dsp Dipole Loudspeakers.
  Reply With Quote
Old 10th May 2008, 05:10 PM   #255
gedlee is offline gedlee  United States
diyAudio Member
 
gedlee's Avatar
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally posted by john k...


Maybe I am missing something but they seem to present a very straight forward discussion for the corrections to the eigenfunctions and eigenvalues for small admittance. So if I assume that the wall admittance is small but real, then energy is lost to the wall and that should provid the damping, no? As you note, the eigenfunctions don't change much for small admittance so initially I will not alter them. It becomes a matter of how the eigenvalues in the denominator change.

Quite correct and my last post on this was wrong. (Sorry about that.) That was an earlier attempt. If you look at the equation you can see that I just use a complex eigenvalue with mode independent damping. M&I use mode dependent damping, which is more accurate if the damping is only on one wall, but if the damping is well distributed, as I always try and do, then a mode independant form is completely accurate. ALL OF THIS ASSUMES small damping which is the real problem.
__________________
Earl Geddes Gedlee Website
  Reply With Quote
Old 13th May 2008, 02:19 PM   #256
john k... is offline john k...  United States
diyAudio Member
 
john k...'s Avatar
 
Join Date: Aug 2004
Location: US
Well, I have modified my room mode analysis to include frequency dependent “real” admittance (conductance) and "tune" the admittance model using FEM simulations from SoundEasy. The agreement between SE for monopoles and dipoles is very good. I then redid the calculations for the monopole, dipole and cardioid I had previously posted.

http://www.musicanddesign.com/roomgain2A.html


While there are differences, I think I have to pretty much agree with Earl that at low frequency there is little differences between sources (except below the room fundamental) unless they are placed in very critical (not necessarily good) positions. The dips you see in the 30 to 40Hz region, which are common to all source types, have more to do with the listener position than source position, type, or orientation. The null is basically a result of the listener being center left to right in the room. Being centered there is little SPL generated at the listening from the first mode in the side to side direction which is at 34.4 Hz since this position is a pressure node for that mode, and all odd numbered nodes in the side to side direction. Looking at the plot at the lower right, where the listener is off center, you can see that region begins to fill in for all sources. But remember, this is for a dipole and cardioid source orientated at an angle to the walls. If the dipoe and cardioid are orientated with the axis parallel to a side wall the dipole wil sill have the deep null when the listened moves to the left or right of center. The cardioid will behave much like a monopole and the null will fill in.
__________________
John k.... Music and Design NaO dsp Dipole Loudspeakers.
  Reply With Quote
Old 13th May 2008, 03:23 PM   #257
gedlee is offline gedlee  United States
diyAudio Member
 
gedlee's Avatar
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally posted by john k...

While there are differences, I think I have to pretty much agree with Earl that at low frequency there is little differences between sources (except below the room fundamental) unless they are placed in very critical (not necessarily good) positions.

John

Timely. I just finished my analysis which took a lot into consideration. I used four source positions and seven almost random) listener positions (all near the room center, basically any of these locations is a likely listener). I normalized all sources to have a flat average response at the listener positions (basically they all have flat power response into the room). This is the most logical thing to do since all sources are then on an equal footing - all are EQ'd to flat power.

After all this data I conclude that no source is statistically any different than any other. Basically, the room dominates the problem and the source type makes no real difference. We appear to completely agree on this point .

Of course the cardiod and dipole require a lot more power at the low end to achieve a flat room sound power, which is not an insignificant factor.

I will post my paper shortly, which I am going to write up and send to JAES.

I expect that this will shake up some people .

Its good to have collaborations from two people who initially disagreed. Good work.

(Although, I would like to point out that our analysis differ substantially in detail. And close inspection of yours will find that your figures 3 and 5 should be very similar and they are completely different. I don't find this much change with such a small movement of the source and receiver.)
__________________
Earl Geddes Gedlee Website
  Reply With Quote
Old 13th May 2008, 04:47 PM   #258
john k... is offline john k...  United States
diyAudio Member
 
john k...'s Avatar
 
Join Date: Aug 2004
Location: US
Quote:
Originally posted by gedlee



Its good to have collaborations from two people who initially disagreed. Good work.

(Although, I would like to point out that our analysis differ substantially in detail. And close inspection of yours will find that your figures 3 and 5 should be very similar and they are completely different. I don't find this much change with such a small movement of the source and receiver.)
Well, I would say we agree on most of the issues. I'll still say that directivity matters, but at the same time, it only matters if you happen to be so unlucky as to place a monopole woofer exactly at a pressure node or a dipole exactly at a velocity node. There the cardioid has an advantage, but as you note it is countered by the added complexity of eq for the gradient roll of and the need for more power.

I am also putting a page up on the effects of orientation which show that a dipole doesn't excite modes orthogonal to its axis. Certainly the differences between cardioids and monopoles are less significant that those of a dipole. But I think the idea that a dipole is better because it excites fewer modes is just incorrect. If the dipole is positioned so as to excite fewer modes then the end result can only be dips in the response at those modes that can not be corrected by equalization. The only thing left is what happens below the room fundamental.

I am glad I got involved in this thread. I have previously based my opinions on what I have read by other researchers. I never bothered to take a deeper look into this myself until getting into this thread. I had made some assessment using the SoundEasy FEM analysis but I really had to look at the math to see what is going on.

All in all I still think, for those who love dipole midrange the NaO Mini is spot on. It has the advantage of dipole mids which morph to cardioid in the 100 Hz region and then to monopole at low frequency when set up as designed. Still, since the woofers a in separate, self powered enclosures, they can be positioned in any manner the listener prefers to optimize the low frequency response if the design configuration doesn't work out for them. The flexibility of detached woofers is really what it is all about.

As for the differences you site with figure 3 and 5, all I can say is that is what comes out of the analysis and in view of the conformation I made with the SoundEasy FEM code I don’t know how to respond. I’ll try to make a direct comparison with Se for those cases and see.
__________________
John k.... Music and Design NaO dsp Dipole Loudspeakers.
  Reply With Quote
Old 13th May 2008, 05:08 PM   #259
augerpro is offline augerpro  United States
diyAudio Member
 
Join Date: Aug 2006
I hate to oversimplify this-just trying to wrap my brain around it- but are you two in agreement that for bass there is no advantage to any of these forms assuming you didn't just happen to place in the worst possible place? How about if you were running a woofer up around 200-300hz, any advantage to cardioid over monopole considering front wall reflections? From power response and polar response perspective are these forms still about equal-considering they are running up to 200-300hz? I should mention I ask these questions in the context of a 3 way design where the mid (and possibly tweeter) are dipole.
__________________
~Brandon
DriverVault Soma Sonus
  Reply With Quote
Old 13th May 2008, 05:45 PM   #260
gedlee is offline gedlee  United States
diyAudio Member
 
gedlee's Avatar
 
Join Date: Dec 2004
Location: Novi, Michigan
Quote:
Originally posted by augerpro
I hate to oversimplify this-just trying to wrap my brain around it- but are you two in agreement that for bass there is no advantage to any of these forms assuming you didn't just happen to place in the worst possible place? How about if you were running a woofer up around 200-300hz, any advantage to cardioid over monopole considering front wall reflections? From power response and polar response perspective are these forms still about equal-considering they are running up to 200-300hz? I should mention I ask these questions in the context of a 3 way design where the mid (and possibly tweeter) are dipole.

Our discussion has been about LF - below about 150 Hz. You are correct, in general, for typical locations of sources and listeners it makes no difference the source type - except for the need to EQ dipoles and cardiods. Your not likely to get much agreement on the frequency range that you mention.

I would tend to say that there would be some advantage to directivity in this frequency range, however, I have found that unworkable in practice. Of more importance to me is narrow controlled directivity above 1 kHz and a match of directivity at the crossover. The need for directivity control below 1 kHz IMO becomes ever less and less important. Its certainly not a bad thing so long as nothing important is given up to achieve it. I just haven't found it to be practical (read cost effective) to do that.
__________________
Earl Geddes Gedlee Website
  Reply With Quote

Reply


Cardioid BassHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Adventures in cardioid MBK Multi-Way 123 2nd January 2017 03:53 AM
any electric bass players? im building a bass guitar cab KOA Instruments and Amps 27 30th April 2007 03:49 PM
cardioid design? Nappylady Multi-Way 6 24th January 2004 09:07 AM
For all Bass Junkies out there (Behringer Bass processor usage report) VEC7OR Digital Line Level 5 27th October 2003 09:18 AM


New To Site? Need Help?

All times are GMT. The time now is 10:36 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki