How To Increase Speaker Bass Using Capacitor

Subwoofer Tuning Using Cabinet, Capacitor and Resistor

The closed cabinet subwoofer is the easiest. The closed cabinet ensures that rear radiation doesn't cancel out the front radiation.

This type of subwoofer is quite easy to calculate. If the Thiele and Small-scale parameters are known (they can also be measured) the chiffonier volume is easy to calculate.

In general the chiffonier should be tuned to a fitting Q factor of Qtc=0.71. Should the bass be particularly dry and tight, a somewhat smaller Qtc value could be chosen.

This leads to a bigger chiffonier and a considerably more gentle level decrease towards lower frequencies, whereby sloping starts already at higher frequencies.

Subwoofer tuning with resistor in series

If a resistor Rv is inserted before the bass driver the result is the same every bit if a weaker drive system (e.1000. a weaker magnet) had been used.

The electrical Q gene increases:
Qes = Qes.previous * (Rv + Re) / Re, where Re is the DC resistance of the bass driver.

As a result the drive organization may be weakened and bass reproduction in the lower bass region could be increased, requiring a bigger cabinet.

Subwoofer tuning with capacitor in series

But, what is the upshot of a capacitor in serial to the commuter?

At a glance you would say that this is a six dB high pass, assuasive only high frequencies through. As an approximate explanation this is correct.

For a more detailed explanation we demand to utilise the complex number plane. For, resistance is not only a one-dimensional value that may simply be added up, they, rather, consist of several components that should be entered in the complex number plane in different directions.
To the left we have the uncomplicated case of having a driver that acts every bit a resistor, with a capacitor in series.

The red arrow to the right indicates the commuter's resistance (since we are talking about voltage, the driver'south resistance - like whatsoever other resistance - is to be multiplied with the electric current I).The blue arrow corresponds to the capacitor, of which the resistance is dependant on the frequency. This is expressed mathematically as jω whereby ω = 2πf, i.e. 6.28 ten the frequency f.

You lot will notice that the smaller f (or ω) or the smaller the capacitance C, the smaller the denominator resp. the longer the blue arrow.

If the blue arrow is longer, then the ratio of the lengths ULS (voltage applied to the driver) divided by U_ges (total voltage on input terminals) is smaller.

Therefore: when the frequency drops or using a smaller capacitor value, less and less voltage will achieve the driver.

All the same, nosotros had made the assumption that the driver only has an effective resistance.

But, in reality that's non the case.

The driver has:
- An constructive resistance (the voice coil's resistance), marked red
- An inductive reactance of the vocalization coil jωL, upward in the picture show
- And an induced voltage function (by the movement of the vox coil inside the magnetic field, represented by a black arrow)

The sum of all individual voltages issue in ULS, i.east. the voltage applied to the loudspeaker terminal.

In addition, the capacitor is going to be wired in series (blue pointer downwards).

You will notice in the movie that the voltage practical to the driver ULS is bigger (i.e. the pointer is longer) than the voltage U_ges applied to the loudspeaker terminals (turquoise arrow).

In other words: the capacitor causes an upward transformation, i.due east. the capacitor increases the voltage applied to the commuter.

Now the question comes up, when this happens.

Answer: whenever the capacitor helps to move the pointer of the total voltage closer to the axis to the right (effective / loss voltage).

What are the implications in do?

If you lot have a measuring instrument that is capable of measuring circuitous impedance (perchance your sound card?), then it's piece of cake to summate how a capacitor changes the level.

Below, we have done this for the Alcone AC12 SW4 (first five columns).

In column 6 (inductive part C) the inductive impedance of a 800 μF capacitor was added (since the impedance is capacitive the values are negative).

Column 7 shows the sum of all anterior parts. If this value is smaller than the inductive role in cavalcade five, then the level rises, indicated by the 2 last columns.

	Loudspeaker Impedance	+ Capacitor		Gain
Frequency	Impedance in Ohm	Phase in caste	Actual share	Inductive share	Inductive share C	Inductive sum	ULS/Uges	in dB
10 Hz	4.32	xiv.36	four.19	1.07	-19.ninety	-18.83	0.21	-thirteen.46
11.2 Hz	4.28	eighteen.89	four.05	one.38	-17.74	-xvi.36	0.25	-11.90
12.vi Hz	4.31	23.84	3.94	1.74	-15.81	-14.07	0.29	-10.60
14.1 Hz	4.43	28.91	3.88	2.fourteen	-fourteen.09	-eleven.95	0.35	-9.05
xv.ix Hz	4.64	34.26	three.84	2.61	-12.56	-ix.95	0.44	-7.23
17.8 Hz	4.95	39.four	3.83	three.14	-11.19	-8.05	0.56	-five.11
20.0 Hz	v.4	44.64	3.84	three.79	-9.98	-6.18	0.74	-2.threescore
22.4 Hz	vi.03	49.66	3.90	four.59	-8.89	-iv.xxx	1.04	0.33
25.1 Hz	6.85	54.46	iii.98	v.57	-7.92	-2.35	1.48	three.41
28.2 Hz	eight.06	59.02	iv.xv	6.91	-7.06	-0.16	1.94	five.76
31.6 Hz	9.95	63.24	iv.48	8.88	-half-dozen.29	2.59	1.92	five.68
35.48	13.64	66.66	v.41	12.52	-5.61	6.91	1.55	3.83
39.8 Hz	17.43	64.78	7.43	xv.76	-five.00	10.76	1.33	2.49
44.7 Hz	51.32	61.4	24.58	45.04	-4.46	40.59	1.08	0.68
50.1 Hz	85.6	-28.86	74.97	-41.30	-three.97	-45.27	0.98	-0.20
56.2 Hz	24.thirteen	-71.16	seven.fourscore	-22.83	-3.54	-26.37	0.88	-i.14
63.one Hz	15.43	-68.09	v.76	-fourteen.31	-three.15	-17.47	0.84	-1.53
lxx.eight Hz	8.95	-65.98	three.64	-8.17	-2.81	-x.98	0.77	-two.23
79.iv Hz	7.38	-53.81	4.36	-five.95	-2.51	-8.46	0.78	-2.21
89.1 Hz	5.33	-45	3.77	-iii.77	-2.23	-6.00	0.75	-2.47
100 Hz	4.82	-34.xiv	3.99	-2.70	-1.99	-4.69	0.78	-2.xiii
112 Hz	iv.21	-22.four	3.89	-1.60	-one.77	-3.38	0.82	-1.76
126 Hz	4.xvi	-xi.72	4.07	-0.84	-one.58	-2.43	0.88	-1.14
141 Hz	4.26	-0.85	4.26	-0.06	-1.41	-i.47	0.95	-0.49
158 Hz	4.34	7.58	iv.30	0.57	-ane.26	-0.68	1.00	-0.03
178 Hz	4.59	fifteen.65	four.42	i.24	-1.12	0.12	1.04	0.32
200 Hz	four.9	22.38	4.53	ane.86	-i.00	0.87	ane.06	0.52
316 Hz	6.75	39.29	5.22	4.27	-0.63	three.64	1.06	0.50
501 Hz	nine.four	47.47	6.36	6.92	-0.40	vi.53	ane.03	0.27
1000 Hz	15.29	53.63	9.07	12.31	-0.20	12.xi	1.01	0.09
1995 Hz	25.46	52.56	xv.48	20.21	-0.x	20.11	1.00	0.03

What causes the rising levels?

Area i (subsonic, yellow):
At low frequencies the capacitor's impedance is so loftier that the driver'due south level is lowered.

Area 2 (below the resonance frequency of the bass driver, light-green):
From 22 Hz on, where the inductive function of the impedance is higher than the sum of the anterior and capacitive part, the level continues to ascent up to 49 Hz.

Area iii (to a higher place the resonance frequency of the bass driver, light-blue):
At 49 Hz the commuter reaches its resonance; at this signal the phase changes as is typical. The capacitor at present starts reducing the level; a slight change initially since the driver's impedance is high. When the frequency continues to ascent the imaginary impedance of the capacitor decreases, only much faster than the commuter's impedance, which is why the capacitor causes the level to decrease up to seventy Hz.

Area iv (higher frequency range, reddish):
When the frequency continues to rise the capacitor's impedance becomes so small that this component doesn't play an important part anymore. Once again, some pocket-sized level increase may occur.

The calculated values represent closely to the measuring results. If the capacitor's value is increased the bass boost starts at a lower frequency but turns out to be somewhat gentler:
- at yard uF: heave from xx.5 Hz / increase of five.5 dB
- at 1200 uF: heave from 19 Hz / increment of 4.7 dB
- at 1600 uF: heave from 17.5 Hz / increase of four dB

The capacitor's value, however, should not exist also small, otherwise the driver's pulse response suffers.

Subwoofer tuning with bass reflex cabinet

A subwoofer in a bass reflex cabinet has singled-out advantage: in this case both front and rear radiations of the diaphragm is made apply of. The bass reflex port adjusts the phase of the rear radiation of lower frequencies in such a manner that front and rear radiation complement i another.

This is important since otherwise the diaphragm needed to much bigger (several square metres are needed for 20 to 50 Hz).

The disadvantage:
The bass reflex tube is a resonating object and therefore, shifts the phase and reproduces bass with less accurateness.

In case the commuter's magnet is too stiff it can be weakened by employing a resistor.

Or a low bass tuning has to be applied. In that instance the driver has accented control over its own diaphragm; but then, the amplifier module needs to restrict the bass at higher frequencies. The Alcone subwoofer Sub 10-60 piece of work co-ordinate to this organisation.

Advantages / disadvantages of tuning methods

The closed chiffonier loudspeaker - especially when a Qtc of less than 0.7 was called - still offers the cleanest audio reproduction. Withal, should you lot plan to add together a bass reflex or band pass subwoofer at later stage - similar some of our loftier-end customer - then a low tuned Alcone or whatever other top notch bass driver is the all-time solution.

The method to heave depression bass with a capacitor provides less control, since every energy storing component (like a capacitor) reduces pulse response. The advantage of the bass reflex port (using the rear radiation of the diaphragm) doesn't come up into effect here. We, therefore, don't regard the solution to utilize a capacitor for less than optimal (only disadvantages, no advantages!).

We prefer the fiddling known tuning method by employing a resistor in series (see above or more than detailed here) to the method of using a capacitor. The serial resistor solution is totally unconventional and is rejected by many designers due to reduced damping of the amplifier. However, if this unconventional method is employed correctly, there won't be whatsoever disadvantages, only advantages - refer to interview.

Farther interesting solutions are the infinite consuming horn loaded bass, it needs at least a room corner. Or the transmission line speaker, trying to combine the advantages of the closed cabinet with advantages of the bass reflex cabinet. Simply, here other disadvantages become evident, similar e.g. the TML gap.

Home

Source: https://www.lautsprechershop.de/hifi/aka_tief_c_en.htm

Share this post