I don't know where your program is off.............
I mean, yea, you can run a larger box and tune it a little lower.....................
But your F3 will go up, but your F9 should be lower...........
I've wanted to try a double 12a in 5ft3 tuned to 50hz..........
| Speaker Stats | ||
| fs | 51 | hz |
| vas | 2.89 | ft3 |
| qts | 0.35 |
| Ported equations |
| Vb = qts^2.87 x 15 x Vas |
| F3 = qts^ -1.4 x .26 x fs |
| Fb (tuning) = qts^ -.9 x 0.42 x fs |
| Ported (butterworth) 4th | ||
| Vb | 2.13 | ft3 |
| F3 | 57.66 | hz |
| Tuning freq | 55.10 | hz |
I mean, yea, you can run a larger box and tune it a little lower.....................
But your F3 will go up, but your F9 should be lower...........
I've wanted to try a double 12a in 5ft3 tuned to 50hz..........
Please Excuse My Dear Aunt Sally:
Parenthesis, Exponentials, Multiply and Divide, Add Subtract. The parenthesis are not actually required because of the exponents, but certainly clarify when we can't type with superscripts. Otherwise since everything is multiplication in this case left to right. In a perfect world we'd all use LaTex and we could format like a text book. 😉
Call me naive, but this is what I thought the OP meant. I used the Dayton Audio DS215 8" midwoofer's publicly available FRD and impedance plots to illustrate.
Pros: The -3 dB point has been lowered from about 70 Hz to 30 Hz. The enabling factor here is impedance correction filters which flatten the woofer's resonant peak. The Zobel after is not really needed.
Cons:
I don't necessarily recommend this but did this purely as an academic exercise. Additional tweaks could be used to extend the HF response but not done here.
The plot to the right starts at 20 Hz.
Pros: The -3 dB point has been lowered from about 70 Hz to 30 Hz. The enabling factor here is impedance correction filters which flatten the woofer's resonant peak. The Zobel after is not really needed.
Cons:
- Loss of ~ 10 dB of sensitivity.
- Current flow through R3
- No consideration for Xmax, which will limit maximum output
- Also because of Xmax, this probably should only be attempted in a sealed cabinet.
I don't necessarily recommend this but did this purely as an academic exercise. Additional tweaks could be used to extend the HF response but not done here.
The plot to the right starts at 20 Hz.
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x2 ... written as x[sup]2[/sup]
Some things on the forum are not intuitive, unfortunately 😉
Put it on VituixCad simulation, there is possible to add series resistor for vented box simulation.
If sensitivity is reduced by 10 dB, then 90% of the power is being dissipated in resistors, thus doing nothing but heating-up the room. Just my humble opinion, but I'd rather solve the problem with active EQ of the low-level signal feeding the amplifier.
If you use a tweeter that's sensitive enough to need that much attenuation you also have to watch the background hum and noise of the amplifier. Resistors can reduce this but EQ will not.
Testing for this is as simple as connecting the tweeter directly and listening without music.
Testing for this is as simple as connecting the tweeter directly and listening without music.
True, but tweeter power levels are much lower than woofer power levels. So while 10 dB resistive attenuation of a woofer might waste 90 Watts, the same attenuation of a tweeter might waste 9 ... or 0.9.
For sure. It's also interesting that a typical class AB amplifier is somewhere around 50% efficient.
For a "high bias" amp, it may be 100% inefficient while it's idling. 🙂 Point is, that 50% efficiency relies on the idea of full power usage. If an amp is in class A up to say 20 Watts, it's going to be pretty inefficient most of the time, no? Most of us have way too much amplifier power. Myself very much included. 😀
Yes, it varies. It's also typical to see inefficiency everywhere and while it's not good for the environment, it isn't bad for sound necessarily.
Obviously I don't want to pad woofers if I can help it but if there is a good reason for using resistors, I'll happily use them.
Obviously I don't want to pad woofers if I can help it but if there is a good reason for using resistors, I'll happily use them.
When I built my tweeter amplifier I had surveyed the needed power. 50mW was plenty loud.
This sounded very much like "help me not spend any more money on drivers but still get bass" kind of exercise, so kind of fun to discuss and stretch our grey matter into solving the issue, but if I was trying to get a job as a speaker designer I'd be afraid of anyone seeing my suggestions on this thread and thinking this is how I normally do speaker designs. 😀
" How not to spend money on drivers" goal ? Post #44 has $168 in components at PE prices. 2 ea 16 mh air coil $110, 9 mh air coil $22 4 ea 500 uf electrolytic cap $28 1 150 uf cap $4 22 uf cap $1 2 resistors $2 .
Wtth that much in crossover components a Eminence Lab 12 driver at $259 does not look like a wasteful purchase. 2021 I picked up used monaural 150 w 0.5% HD warehouse amps for $50. MMA-8150t. 2023 I scored a Nady crossover appliance that filters and merges the two sub signals, and low cuts the two main signals, for $50.
Then I would not have to worry so much about exceeding Xmax on the main bass drivers, cutting them above Fs. Without low cut I saw my SP2-XT woofers move ~2 cm when I walked across the wood floor with the turntable arm on the record. Xmax 0.9 mm.
Wtth that much in crossover components a Eminence Lab 12 driver at $259 does not look like a wasteful purchase. 2021 I picked up used monaural 150 w 0.5% HD warehouse amps for $50. MMA-8150t. 2023 I scored a Nady crossover appliance that filters and merges the two sub signals, and low cuts the two main signals, for $50.
Then I would not have to worry so much about exceeding Xmax on the main bass drivers, cutting them above Fs. Without low cut I saw my SP2-XT woofers move ~2 cm when I walked across the wood floor with the turntable arm on the record. Xmax 0.9 mm.
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I don't know if this would work for you, but it might be worth a look. It's using a large cap in series with the woofer.
https://sbacoustics.com/wp-content/uploads/2018/05/Capacitor-Tuning.pdf
https://sbacoustics.com/wp-content/uploads/2018/05/Capacitor-Tuning.pdf
I have used this "high pass filtered woofer" quite often to improve too small enclosures. A calculation may give a good starting point, but fine tuning it, using a near field measurement will be needed. Otherwise you will usually be a few hundred micro Farad away from the optimum, which is audible. Quite simple to understand, the real Qtc the driver has in the cabinet is important and this will usually be different to the geometrical volume.
You usually combine some capacitors in parallel to get the 400-1200 micro Farad you need anyway, so this is no problem.
There is a valueable trick to get the needed bipolar capacitor size cheap. As any crossover component that has q label "for audio" on it is about 10 times overpriced, you may build your own bipolar cap from usual electrolythics.
Just take two identical capacitors and connect the positive ends together, which is important. The result is a bipolar cap with half the capacity. A good idea is to combine two 1000uF 40 Volt caps into a bipolar 500uF one and do the fine tuning with some bipolars for audio. The bipolar audio capacitor is nothing else, just combined in one housing, so don't worry about any losses.
Opposite to many voices, the resulting bass is not worse, but usually better, "faster" than without the high filter cap.
Also, you CAN NOT get the same effect from equalizing the signal. The capacitor enables the driver to use more current around the resonance frequency. It also protects the woofer from insanely low frequency and DC. All with just a capacitor. CANTON patented it for their reference DC speakers, even as the principle was used since the 70's as far as I know, mostly for limited space and amp power in car audio. So nothing new at all.
PS usually used for closed cabinets, it can be used for vented ones too, but is much more complicated to simulate and tune. The results are very good if it is used right.
You usually combine some capacitors in parallel to get the 400-1200 micro Farad you need anyway, so this is no problem.
There is a valueable trick to get the needed bipolar capacitor size cheap. As any crossover component that has q label "for audio" on it is about 10 times overpriced, you may build your own bipolar cap from usual electrolythics.
Just take two identical capacitors and connect the positive ends together, which is important. The result is a bipolar cap with half the capacity. A good idea is to combine two 1000uF 40 Volt caps into a bipolar 500uF one and do the fine tuning with some bipolars for audio. The bipolar audio capacitor is nothing else, just combined in one housing, so don't worry about any losses.
Opposite to many voices, the resulting bass is not worse, but usually better, "faster" than without the high filter cap.
Also, you CAN NOT get the same effect from equalizing the signal. The capacitor enables the driver to use more current around the resonance frequency. It also protects the woofer from insanely low frequency and DC. All with just a capacitor. CANTON patented it for their reference DC speakers, even as the principle was used since the 70's as far as I know, mostly for limited space and amp power in car audio. So nothing new at all.
PS usually used for closed cabinets, it can be used for vented ones too, but is much more complicated to simulate and tune. The results are very good if it is used right.
On 1 vac signals which are what I usually listen to during soft passages, back to back polar electrolytics sound weird. If you are a bar band and always play turned up to volume 11 don't worry about it. My hearing goes to 14000 hz, if you played loud enough often enough you will never hear this problem.
Thinking of buying 2.4 mF of polypro 200 vac capacitors to put series my SP2(2004) to prevent DC damage. Before the price doubles, $252 today. You say 1.2 mf series the speaker changes the system Q? My M-2600 amp has no DC protection and AC rated relays used in Ali/ebay/amazon protection boards are snake oil for protecting against DC.
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Be careful with that. There is a discussion about that here, starting around post #19 (though I've read that thread and still haven't come to a clear conclusion about it myself). Basically, whether back-to-back polarized capacitors act like they have a capacitance of "C" or "½C" appears to depend upon the voltage applied, and for how long.