Resonance Circuits and Resonance Systems

[Belfior]

I'm not sure what you mean by "looped coil" or "large cap" here. You can use any number of on-line calculators to determine resonant frequency,
inductor and capacitor values. My favourite one is here:
http://www.1728.org/resfreq.htm

looped coil is just connected to itself. What I was thinking was to compensate the number of turns with a large capacitor. Not sure what the ratio of inductance and capacitance will do, but I will find out!

I'm not sure what you mean by "feeding back" here.

I meant the secondary having a feedback to the system like it does in the slayer exciter. If the secondary is looped with a capacitor it still acts as an antenna and I could maybe use a looped coil with your style of antenna feedback?

But I have to warn you: You will find it very difficult to get consistent and satisfactory results using a loose, sloppy layout with lots of
clipleads, and the problems will get worse with higher frequencies.

Yeah I just use the clipleads when I try out something and then solder afterwards. Just got some bread boards that could help me keeping the connections shorter

One other thing: When posting pictures to the forum, please PLEASE try to keep the horizontal width small enough so the pix don't run
off the page to the right. 800 pixels wide is good enough for most purposes; rarely you may need to use up to 1024 pixels wide. If you
need to show some detail at high magnification, crop it out of the larger picture and post the cropped detail at no more than 1024 pixels wide.

Yeah can't find any buttons on this thread anymore. Going to delete the pic

[Magluvin]

My studies in resonance has taken a turn toward resonance of sound.

Ive been working in car audio for many years. All this resonance talk with circuits and such has brought me to the conclusion that I have been working with resonance for a longer time than I realize, and Im recognizing its importance to all this and I want to figure out how we can relate the audio resonance to circuits and such.

To start here, Im going to show how Im going to use resonance to outdo my friend in a DB Drag sound competition using the same equipment. 6 12in Pioneer Champ pro subs, and 3 pioneer digital(class D is what they imply) run at 1ohm 2 subs per amp. So my friend is copying my specs for my sub box. That got me a bit as why cant he go with his own design, anyway...  So Im not telling him of my new plans. 

Originally I was going with 3cu ft at 25hz tuned with a 4in port 15in long for each sub. total of 18 cu ft internal. This would have the characteristics of the Lt Blue trace in the multiple trace graph below.

So my new weapon is the dual chamber reflex enclosure. The Lt Blue trace is tuned at 25hz, and the new dual chamber reflex is shown with the characteristics of the pink trace(emulated with a 6th order bandpass option except the DCR will not have upper cutoff like shown here. Ive made a corrected graph for that below the multi trace graph) in which my new design has resonance at 25hz and 50hz.  In car response increases below 80hz up to 12db down to 20hz, So the hump at 50hz should be close to flat down to 25hz.

In the multi trace graph I show multiple possibilities for different boxes for the sub.

Yellow trace -  Infinite baffle. Basically largest sealed box possible. I made it 50cuft as going larger doesnt make much difference for this explanation.
Green trace - Recommended sealed box at 1.25cu ft
Orange trace - Recommended ported(vented) tuned enclosure at 1.5cuft tuned at 38hz(of which is loud but I like a lot of lower extension bottom end)
Lt Blue trace - My version of ported enclosure at 3cuft tuned to 25hz.  Huge gain in the low end. Have built a test box and it rocks.
Pink trace - 6th order bandpass enclosure where speaker is enclosed in between 2 boxes each tuned to 25hz and 50hz respectively. Notice the gain at 25hz and on up to 50hz. Im in the belief that the gain at 25hz is due to the combination of the 50hz tuning together, as in they help eachother as seen in the gain at 50hz also.
Purple trace - This is a 6th order with 35hz and 38hz tuning. Combined there is a monstrous gain in that area of freq.

So with the various implementations great amounts of efficiency can be had vs just a sealed enclosure or infinite baffle where the speaker output is all on its own trying to get the job done.

So the second graph shows the difference between my friends box in the green trace and my new design in purple. I will be louder all the way around by just reconfiguring my box still using 3cuft total for each sub. The box chart below shows the various speaker box types out there. My design is based on Weems dual chamber reflex shown in the box selections below. Im interested in the Fostex but there are not any design parameters out there as it is a proprietary design by Fostex. It would have to be experimented with to gain knowledge on how to calculate.

In the Db Drag competition the upper limit of freq is now below 60hz, used to be 100hz. Guys used to tune to 90 and only play 90hz to see who was louder. They were getting above 180db and it certainly wasnt music. So you can see the gain I will have over my friend at 50hz come Spring Break Nationals.

So what does this all have to do with this thread?  The combination of 2 freq even at a distance of 25hz to 50hz shows an overall gain. And the high peak trace at 35 and 38hz should be of interest. If we can apply this to electronic resonance it may be promising. It makes me think of the TPU supposedly using 3 tuned freq. Maybe it is simpler than we think.

Mags

[Magluvin]

My initial thinking would be to have a drive coil between 2 lc coils. What Im trying to comprehend is how do we associate the output of the speaker box to a load in the electronic version. The speaker boxes load is moving air. So how do we look at loads with the electronic version in a comparative way? Like if we close of the speaker output by putting a solid cover over the speaker cone and cover the port outputs would, to me, act like a short circuit load of the electronic version thus having a not so positive output goal. On the other end, if the speaker box were in a vacuum there would be no output as if there were no load in the lc circuit. So loads for lc circuits most likely need a happy medium and a load matched for each variation.

Just thoughts

Mags

[Magluvin]

The formulation for the Weems DCR is to calculate a vented box while calculating it for 2 ports at the low freq you want, to get the length of the ports, then cut all 3 ports to that length then divide the box into 2 thirds for the speaker side and 1 third for the other ported side. You have to calculate the volume that the ports take up along with the speakers displacement and add that to the total internal volume to be precise. This box will ring at the low freq(my box at 25hz) and it will ring at the next octave up( my box would be 50hz)

Built 2 of them before. Got the info from a book by David Weems on speaker enclosures.

The Fostex enclosure by example seems to have the smaller partition of the enclosure on the speaker side and not necessarily divides in thirds. The box chart above does not show this but I have seen many examples.

Im thinking that the smaller speaker chamber is tuned to the upper freq with the port in between the partitions and the outgoing port is tuned to the lower freq objective calculating the enclosure as a whole.  The Weems design, both ports are active at the lower freq as if the partition were not there, as shown by the calculations of 2 ports to get the low freq tuning. Im still pondering how the 50hz ringing is accomplished. Had not studied that with the other 2 boxes I made.
Will do on this new setup.  But the Fostex Im guessing that the small side with the internal port between the chambers rings at the uper freq and the lower port outputs the upper freq anyway, like how the 2 tuned freq help each other in the DCR trace.

Below is a more accurate depiction of a Fostex design compared to what Ive seen of the real thing others have done including Fostex.

Just getting deep into all this and I hope it helps with things we are trying to accomplish here.

Mags

[Magluvin]

One more thing

A ported enclosure tuned to say 25hz, the speaker is moving very little at the tuned freq. The speaker and the output of the port are in phase. So the speaker and the port are pushing out at the same time and the port has the most output at that freq. As we go lower in freq the port output goes out of phase and eventually the output of the port is 180deg out of phase where there is no output, just big speaker cone throw and port noise as they cancel audible program output. Using a subsonic filter on vented enclosures is popular to cut out the low freq that are below the tuning freq to avoid wasting precious power on output we cant hear.

So with the Fostex enclosure, the small chamber say if tuned to 50hz, once the freq goes below 50hz, the internal port starts going out of phase and once it gets down say an octave and below, the internal port becomes invisible to the speaker and the box acts like the internal port and partition do not exist when it comes to freq dependence and the box acts like 1 large vented enclosure tuned to the lower output port freq tuned to the box as a whole enclosure. This is the theory I have figured with the knowledge of studying the Weems design. The Weems design at the lower tuned freq also acts as if the internal partition and port do not exist.

Im just learning a lot about resonance in a fun way here. I hope it adds up to something we can use here.

Mags