Hi, I'll be grateful if someone can sim my 6th order bandpass sub, or help me sim it myself (I have never done that before). I'm especially interested in the frequency that the sub resonates at, as (if I understand correctly) the sub is effectively unloaded below that frequency and it is easy to exceed Xmax.
It's a 1980's TOA SLB and here is a schematic.
It's a 1980's TOA SLB and here is a schematic.
Hi and thanks! I have seen that, but what I'm trying to figure out is how low I can go with a different driver. As far as I know, if the cabinet can be modeled, I'll know the resonant frequency of the cabinet and that will inform me of the safe lower frequency.
The PDF does indicate that one of the cabinets described in it is tuned to 40 Hz and the other to 50 Hz.
BTW, the SPL charts for each cabinet both show a response that peaks +10dB at 100 Hz. Curious that they'd suggest that a cabinet tuned to 40 Hz or 50 Hz and +10dB at 100 Hz was produced to reproduce today's electronic music with its "ultra-low frequency sound". What year were these cabinets produced? 🙂
Gotcha. I was hoping that the 50 hz lower end of the SLB was at least partially from the limitations of the driver and not entirely from the cabinet tuning.
They're from the 1980's.
The cabinet tuning (Fb) will remain the same regardless of the driver used. In general, the Fb frequency should be close to the driver's resonant frequency (Fs), and larger Vas drivers require larger boxes for "flat" response. There is a much wider selection of small Vas/low Fs drivers available now than in the 1980s, with excursion double and triple what was available then. Doubling linear excursion (Xmax) increases output by 6 dB, though also takes 6 dB more power, which is now cheap in both drivers and amps by comparison to 3 decades ago.
In the 1980's, 40 Hz was as low as most pop recordings went, now 25-30 Hz is as common, and mixed at higher levels, digital does not have LF limitations like mixes made for vinyl records.
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This is extremely helpful info and I really appreciate it. Now I get that I should look for a driver with a 50 Hz FS, but should the Vas be similar to the volume of the rear chamber of the cabinet?
Generalities:
50 Hz is a relatively high Fb for a "subwoofer" this century, but will give more "bang for the buck" than a lower Fb in terms of output to size.
With a Vas similar to the volume the box (Vb- box volume less port and driver volume) and a Fs similar to Fb, the F3 (-3dB level) output will be close to Fs.
David McBean's free Hornresp program will allow you to simulate the response of any driver you have T.S. parameters for in a variety of enclosures.
I would have preferred to be able to go very low and very loud, but I'll accept these "subs" are what they are.
Surprisingly to me, I did follow what you wrote about Vb, Vas, Fs, Fb and F3. Thank you, that is very good info and I really appreciate it.
I'm trying to figure out hornresp, but can you tell me the effect of Vas being larger than the enclosure? Specifically, if I use the Eminence 3015LF4, then my Vb is 63.4, but the driver has a Vas of 118.
I went with the Eminence 3015LF4
I figured out how to fool around with a few different speaker simulatin programs. The cabinet is more or less incapable of producing less than ~50 Hz, so I went with the Eminence 3015LF4 which is similarly incapable.
I run 4 of these subs with an Inuke 3000DSP which pretty handily delivers ~500 watts to each sub. The sound is pretty darn decent for subs that I can move myself.
The 3015LF4 have a larger diameter than the stock drivers from TOA so I used PVC spacers to keep the cone from banging against the cabinet.
I figured out how to fool around with a few different speaker simulatin programs. The cabinet is more or less incapable of producing less than ~50 Hz, so I went with the Eminence 3015LF4 which is similarly incapable.
I run 4 of these subs with an Inuke 3000DSP which pretty handily delivers ~500 watts to each sub. The sound is pretty darn decent for subs that I can move myself.
The 3015LF4 have a larger diameter than the stock drivers from TOA so I used PVC spacers to keep the cone from banging against the cabinet.
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