I seem to remember a method of manipulating high spl woofers to extend the f3 at the expense of some sensitivity. I would like to get f3 in the 40's with my Delta Pro 12a.
Can anyone expound on this idea?
David
Can anyone expound on this idea?
David
It may have been added mass.. however that might not be my first choice if I were to do the same.
Can I ask the context in which you are using them? Sealed/ported, cabinet volume, DSP/passive etc...?
Added mass may work well with high excursion HIFI drivers. PA driver usually don't fall in that category. 4.6 mm is not much excursion. Better use a strong amp and a DSP. For civilised SPL that should work. If not, in a vented, large cabinet it should be able to reach the desired f3.
I only know to increase max flat box size till the max flat tuning is shifted downward to 'x' Hz.
T/S max flat alignment:
Vented net volume (Vb) (L) = 20*Vas*Qts'^3.3
(Ft^3 = (Vb)/~28.31685)
Vented box tuning (Fb) (Hz) = 0.42*Fs*Qts'^-0.96
F3 (Hz) = Fs*0.28*Qts'^-1.4
Tune to the ported f9.
Run a high pass active filter with a q of 2 with the pole at said f9.
It adds 6db of boost right at tuning, where the driver isn't moving.
And it works as a subsonic filter below tuning so it doesn't unload.
It can sound more dynamic and will go louder when relieved of these lower frequencies.
You can find more searching for "6th order" by DJK over on audioasylum.com, the high efficiency forum.
I've built 3 subwoofer this way, double 12's, double 18's, then quad 12's, all tuned to 27hz.
I've lucked into something similar.
I have a jbl 2206 2-way now, with fs of 50hz and Qts .312.
It is ported to 50hz. My receivers bass knob is ported at 50hz. Works well.
Run a high pass active filter with a q of 2 with the pole at said f9.
It adds 6db of boost right at tuning, where the driver isn't moving.
And it works as a subsonic filter below tuning so it doesn't unload.
It can sound more dynamic and will go louder when relieved of these lower frequencies.
You can find more searching for "6th order" by DJK over on audioasylum.com, the high efficiency forum.
I've built 3 subwoofer this way, double 12's, double 18's, then quad 12's, all tuned to 27hz.
I've lucked into something similar.
I have a jbl 2206 2-way now, with fs of 50hz and Qts .312.
It is ported to 50hz. My receivers bass knob is ported at 50hz. Works well.
Exactly. Circuit is dead simple, only use a good op amp and enough supply voltage.
Some great suggestions guys. It'll need to be ported and I think the above quote may have been what I saw yrs ago. Hoping to run passive but i do have an option for active.
No higher math skills, but need to rearrange this formula to find it: F3 (Hz) = Fs*0.28*Qts'^-1.4
And you lose sensitivity when you add resistance in series. However, the Z is increasing on that driver. I think it would would make the freq response droop more going from 1khz down to 50hz............
Anyone, am I wrong here ?
Anyone, am I wrong here ?
No and one reason why I ~defacto added impedance compensation with the other to use 1st order XOs.
For HIFI/HT apps I never want to give away any efficiency unless have no choice, hence my increasing box size suggestion.
yea.
1st orders can be trcky.
I look for copper capped woofers for their flat impedence.
Tweeter's resonance, I suppose notching that down would make it work ?
But we are off track...............
1st orders can be trcky.
I look for copper capped woofers for their flat impedence.
Tweeter's resonance, I suppose notching that down would make it work ?
But we are off track...............
I've done it with a passive x-over and a sealed woofer. If the woofers is crossed very low to a mid, you might could do it.
This has been 'bugging' me all night because I knew I was forgetting something obvious, i.e. I know we need to double box size/octave, so if Qts = ~0.38, then it too ~doubles = ~0.66 and the calculator to find added resistance* = ~5.4 ohms, but in a typical optimal box alignment scenario, no amount of added resistance will work.
As for higher math skills, also remembered I've used this math solver program, though they no longer show all the steps for free
* math
Attachments
Fun thing is I went the same way more than three decades ago on a system with 2x10". Started with coins (...) attached to the dust cap, that gave me either 10 or 20g more cone mass and lowered f3 down to just above 30Hz (measurements didn't survive the years). In the completed system I exchanged that for an active solution with the Q=2 (1,93 actually) cutoff filter at 25Hz and retuned reflex alignment. The electronic parts costed me about what I had attached to the cone before, but the result was 100 percent better. Plus I had a very effective low frequency protection, the woofers never suffered the various house parties they had to withstand (the rest alas did though).
Hi Norman. English is not my first language, perhaps thats why I dont understand exactly what you mean.
Lets say I have a driver with 40Hz Fs, in a certain box. My F3 comes to a certain frequency.
How should I understand "tune to F9" ?
Also "pole at said F9" ?
I do have the ability to do active crossing with dsp....
Thanks
Danny