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Amplifying bass frequencies

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awesomelumens

New Member
HiiiI need some ideas to filter frequencies from 20Hz to 1000Hz and then amplifying it a little and then feeding it into bigger amplifier with normal input.I know about tone control but I want a crispy solid bass. Speakers available include 12inch 8 ohm(20 watts+), 6*9 8 ohm(10watts). I think bigger is better. Guide me about best bass frequency also. E.g if speakers best perform at 200Hz. Can I collect power from 20 to 1000Hz and make it into 200Hz. I think quiting frequencies upto 1000 and alowing only one type of f i.e 200 or 120Hz wil give me similar bass on every song. Which is what I want
 

crutschow

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Most Helpful Member
No you can't readily convert from one frequency to another to increase the bass (and you don't really want to as it will muddy the music).

If you can afford it you should buy a subwoofer with a built-in amplifier that goes to below 40Hz to about 100Hz or so. They have filters to amplify only the bass frequencies.
For "crispy" solid bass you need a subwoofer with good transient response (sealed speaker cabinets are generally better for this but a good ported design can also have good transient response.)
I got good solid bass for my computer speaker setup from a relatively inexpensive Sony subwoofer by (literally) stuffing a large sock in the ported tube to make it more like a sealed sub. It reduced the maximum output some, but the bass was much more solid with better transient response.
 

Tony Stewart

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Electromagnetic back EMF tries to generate voltage from inertia of cone with bass travel, so dampening of this effect is defined by impedance ratio of load/source. Typ. values are DF=>100 thus Zout of bass amp <=8/100 Ohm or 80 mOhm.

As @crutchow did well to reduce Q of helmholtz resonator effect with extended bandwidth and tuned port but by physical dampening air flow for a large Volume enclosure (0.5~1m^3).

Lower Q reduces overshoot and makes kick drum sound tighter. This is one way to do it.

More modern way is to use compliant cone rim in sealed sub-woofer box and use optical cone feedback in servo feedback to extend response or in loaded horn air duct or labyrinth 1/4wave tuned box.

more info http://www.diysubwoofers.org/definitions.htm#tsparam
 

spec

Well-Known Member
Most Helpful Member
Electromagnetic back EMF tries to generate voltage from inertia of cone with bass travel, so dampening of this effect is defined by impedance ratio of load/source. Typ. values are DF=>100 thus Zout of bass amp <=8/100 Ohm or 80 mOhm.
Tony,

I have always wondered about the damping factor figure and suspect it is purely a marketing ploy, but please correct me if I am wrong:

To a first approximation, a loudspeaker comprises a perfect solenoid (motor) in series with a resistor. That resistor is pretty much the characteristic impedance of the loud speaker so, by definition, the lowest effective output impedance seen by the solenoid (the motor) is the value of the series resistance. So, it follows that the actual damping factor, influencing the solenoid is likely to be around 50.

To further support this, the efficiency of a cone loudspeaker is only around 5%, at very best so this implies very loose coupling between the amplifier output and the loudspeaker motor.

When I was a sprog an old (probably 40) audio engineer explained this to me and I never forgot it; what is your view?

spec
 
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simonbramble

Active Member
I know you are right about the efficiency of a loud speaker. When I was going through the training school of my first company, the head of training designed the amplifier in the Odeon Leicester Square. The amplifier there is only about 20W, but have lots of volume because the loud speakers are very efficient (about 45%)
 

simonbramble

Active Member
Attached is a battery powered bass amp I designed for an MP3 player. The first stage amplifies the bass, the second stage acts as a volume control, but does not amplify the dc. You can use this as the basis of a bass amplifier
 

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spec

Well-Known Member
Most Helpful Member
I know you are right about the efficiency of a loud speaker. When I was going through the training school of my first company, the head of training designed the amplifier in the Odeon Leicester Square. The amplifier there is only about 20W, but have lots of volume because the loud speakers are very efficient (about 45%)
Yes, many of the cinema (movie house) speakers were loaded by a huge horn. This matches the radiation resistance of the speaker cone to the radiation resistance of air and produced an effortless expansive sound that you only normally expect from a live concert.

A friend pretty much rebuilt an old inn and, without his missuses knowledge, incorporated a huge masonry horn in the chimney breast/stack. He uses it as the bass sub for his audio system, which is also on a grand scale.

It is a good job he lives in the country with no near neighbors.:D

spec
 
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awesomelumens

New Member
No you can't readily convert from one frequency to another to increase the bass (and you don't really want to as it will muddy the music).

If you can afford it you should buy a subwoofer with a built-in amplifier that goes to below 40Hz to about 100Hz or so. They have filters to amplify only the bass frequencies.
For "crispy" solid bass you need a subwoofer with good transient response (sealed speaker cabinets are generally better for this but a good ported design can also have good transient response.)
I got good solid bass for my computer speaker setup from a relatively inexpensive Sony subwoofer by (literally) stuffing a large sock in the ported tube to make it more like a sealed sub. It reduced the maximum output some, but the bass was much more solid with better transient response.
I have some amplifiers but i want a tone control. What if I use 2 amplifiers and use 1 for frequency below 1000Hz. And other for frequency above it. Than combine and feed it to a speaker. That resistor-capicitor circuit can filter effictively or some op-amp is needed?...
Yeah sealing it also reduces noise sometimes. It gives a very confined bass than...thanks
 
Last edited:

awesomelumens

New Member
Electromagnetic back EMF tries to generate voltage from inertia of cone with bass travel, so dampening of this effect is defined by impedance ratio of load/source. Typ. values are DF=>100 thus Zout of bass amp <=8/100 Ohm or 80 mOhm.

As @crutchow did well to reduce Q of helmholtz resonator effect with extended bandwidth and tuned port but by physical dampening air flow for a large Volume enclosure (0.5~1m^3).

Lower Q reduces overshoot and makes kick drum sound tighter. This is one way to do it.

More modern way is to use compliant cone rim in sealed sub-woofer box and use optical cone feedback in servo feedback to extend response or in loaded horn air duct or labyrinth 1/4wave tuned box.

more info http://www.diysubwoofers.org/definitions.htm#tsparam
I will try enclosures of both types. Something about plastic or wood. I want some plastic this time. Its light weight. I have got some gallons :D
 

awesomelumens

New Member
Yes, many of the cinema (movie house) speakers were loaded by a huge horn. This matches the radiation resistance of the speaker cone to the radiation resistance of air and produced an effortless expansive sound that you only normally expect from a live concert.

A friend pretty much rebuilt an old inn and, without his missuses knowledge, incorporated a huge masonry horn in the chimney breast/stack. He uses it as the bass sub for his audio system, which is also on a grand scale.

It is a good job he lives in the country with no near neighbors.:D

spec
Can I use a truck pressure horn. Will it sound a song. I am imagining that when ever my smaller speakers give a normal bass. A large bass(dum) comes from back ground. I really want this stupid thing to occur. Thats why I want to separate out low f and ask it to switch on(((((e.g tda2003(Guru from Canada might not like this) if gives 2-3volts and on bass from song it elevates to 4 ....a zener of 3 volts can be used to drive some transistor or relay for compression system))))) oscillator of 100Hz for one millisecond. It will drive a powertransistor etc and a dum at my big speaker will be produced. Is it possible?
 
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spec

Well-Known Member
Most Helpful Member
Hi AL,

In addition to and to support the above posts, here are a few points:
(1) It is possible to add synthetic bass to music, but it is not really a practical proposition in this instance as some complex electronics would be required to make the added base sound natural.
(2) The crispness and agility of the bass is fundamentally a function of the speaker chassis. In general you need a light stiff cone with a highly compliant surround and spider to keep the resonant frequency low.
(3) The speaker then needs to be placed in a matched enclosure: closed box or ported, of the correct volume.
(4) The enclosure needs to be designed/constructed so that reflections are minimized and the enclosure does not flex.
(5) Also the enclosure needs to be mounted rigidly with free air all around it and away from reflecting surfaces: walls for example.
(6) In order to get an easy articulate bass with plenty of clout you need an amplifier with plenty of voltage headroom and, most important an amplifier that can supply a huge amount of excess current.
Take an example of an amplifier driving an 8 Ohm loudspeaker. If the amplifier were producing a peak voltage of 16V that would imply a current of 16V/8 Ohms = 2A. And by using Oms law alone that would be it.
But in practice to get a good base sound you would need at least 6A or, preferably, more current capability.
(7) Amplifying the bass frequencies in music, as Simon illustrated, involves standard design techniques. So that is not an issue.

What I wounder is do you really want what you say, because a well designed HiFi system can sound pretty bass light, until the music actually has some bass and then it will smack you in the guts.

The alternative is to have a wall-of-bass system which produces a mixture of low frequencies by cone breakup and resonances. Reggae systems tend to favor this style and, with the right music, they are pretty impressive and enjoyable.

spec

(our posts crossed AL)
 
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spec

Well-Known Member
Most Helpful Member
Can I use a truck pressure horn. Will it sound a song.
Afraid not for many reasons which I will not go into.

Your best approach would be to have two speaker cabinets with mid and tweeter to handle frequencies from around 300Hz to 20KHz and one bass sub for the frequencies below 300Hz from both channels. You would then have three amplifiers which can be in the same case or separate.

Your only decision is whether you want articulate or wall-of-sound bass.

The former requires a lot of careful design, an expensive speaker chassis and a real solid cabinet construction, all driven by a substantial amplifier. The later is much simpler: a large ported box with a large speaker chassis- 18 inches would be good- and a standard high power amplifier, say 100W.

The only complication with the wall-of-bass sound is that you would need to have the foundations of your house strengthened, unless they are already 'quake proof.:D

spec
 

spec

Well-Known Member
Most Helpful Member
I forgot to mention that with either approach you will need a filter circuit to combine the low frequencies from both channels and feed them into the bass sub amplifier- all pretty standard stuff. Your base boost control will just comprise a volume control on the base sub amp.

On question: are you planning on building or buying?

spec
 

spec

Well-Known Member
Most Helpful Member
Planning. If it goes right than building. Done with some easy DIY stuff. Now trying for some cheeky bass b on someones request
Can you indicate which of the following you are talking about building:
(1) Bass sub speaker
(2) 2 of mid/high speakers
(3) Bass amplifier
(4) Mi/high amplifier
(5) Bass filter/combiner

spec
 
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