Amplifying bass frequencies

[awesomelumens]

Hi again AL,

You may be interested in reading this thread @ https://www.electro-tech-online.com/threads/12v-bicycle-trailer-sound-system-details.149152/

spec

haha I should purchase a bicycle

 

[awesomelumens]

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

well as I told that the requirement was to get some special bass. But I have tested a compression speaker with 12" one combined and sounds are terrible ... I would like to know about a decent bass filter, a bass amplifier or high power amplifier(thinking on 4702 +darlington pair). Speakers to be used will be 12". .....Bass combine?how? :O

 

[awesomelumens]

Thanks in anticipation.. Do comment that can sound be made as clean as from laptop out of lm1875. If you have a tested circuit/thread, I would feel interested to read it.

 

[spec]

Thanks in anticipation.. Do comment that can sound be made as clean as from laptop out of lm1875. If you have a tested circuit/thread, I would feel interested to read it.

Your best bet is to do the following:
STAGE 1
(1) Store you audio as digital audio files, MP3, but preferably FLAC, in a folder on your PC.
(2) Download and install J River Media Jukebox (free)
(3) Get that all working so that you can play the audio files on your PC's speakers by using Media Jukebox.
(4) You can also play back music from CD/DVD

STAGE 2
(1) Buy a USB audio DAC ($10 upwards) that will output good quality audio, depending on the quality of the source files.
(2) Buy a 100W RMS stereo audio amplifier, possibly second hand
(3) Buy a pair of speakers, possibly second hand (look for good mid frequency and high frequency quality)

STAGE 3
(1) Connect one of the USB sockets on your PC to the input USB socket on the USB DAC
(2) Connect the analog output from the USB DAC to the input of the amplifier and listen to the music

STAGE 4
(1) Buy a bass sub with built in amplifier, possibly second hand, and connect the two analog outputs of the USB DAC to the left and right channel inputs of the bass sub amplifier.

And you are done.

You can then crank the base up and down either in Media Jukebox and/or by adjusting the volume control on the bass sub.

spec

 

[spec]

An amplifier based on an LM1875 can be bought quite cheaply and while that will give a nice pleasant sound it will not crack your foundations.

spec

 

[awesomelumens]

Your best bet is to do the following:
STAGE 1
(1) Store you audio as digital audio files, MP3, but preferably FLAC, in a folder on your PC.
(2) Download and install J River Media Jukebox (free)
(3) Get that all working so that you can play the audio files on your PC's speakers by using Media Jukebox.
(4) You can also play back music from CD/DVD

STAGE 2
(1) Buy a USB audio DAC ($10 upwards) that will output good quality audio, depending on the quality of the source files.
(2) Buy a 100W RMS stereo audio amplifier, possibly second hand
(3) Buy a pair of speakers, possibly second hand (look for good mid frequency and high frequency quality)

STAGE 3
(1) Connect one of the USB sockets on your PC to the USB socket on the USB DAC
(2) Connect the analog output from the USB DAC to the input of the amplifier and listen to the music

STAGE 4
(1) Buy a bass sub with built in amplifier, possibly second hand, and connect the two inputs to the left and right channels from the USB DAC

And you are done.

You can then crank the base up and down either in Media Jukebox and/or by adjusting the volume control on the bass sub.

spec

woah...It would be fine adjustment. I dont have DAC now but I wil get one in near future. Till then I have installed a bass booster in my phone. And added active tone control to my amplifier.

 

[awesomelumens]

An amplifier based on an LM1875 can be bought quite cheaply and while that will give a nice pleasant sound it will not crack your foundations.

spec

I was asking it for my computer speakers. They have dead bass. When I connected its speakers to big amolifier with volume down, they rocked the room. Will the datasheet diagram work good. Any ideas

 

[Les Jones]

The design of the speaker system is more important than the amplifiers to give good base performance. This usually means they will be large and rigidly constructed to avoid resonances.

Les.

 

[spec]

I was asking it for my computer speakers. They have dead bass. When I connected its speakers to big amolifier with volume down, they rocked the room. Will the datasheet diagram work good. Any ideas

I am sure the LM1875 will sound fine, but I don not like bridge amplifiers as they introduce more distortion and can get into a tangle with some music and difficult-to-drive speakers. There are much better integrated amplifiers.

To get the best from an amplifier you need direct coupling, which means plus and minus supply lines, and good components: metal film resistors and polypropylene capacitors or good quality aluminum electrolytic capacitors for the high values.

spec

 

[spec]

woah...It would be fine adjustment. I dont have DAC now but I wil get one in near future. Till then I have installed a bass booster in my phone. And added active tone control to my amplifier.

I think you have missed the point that you can get much better audio quality from digital audio files by using an external DAC and you can adjust the bass and all other frequencies with the graphics equalizers built into an audio media players, which are free. Media Jukebox, in my experience, is the best sounding all around audio media player. You can also download VLC Media Player for all other media files, mainly video, which similarly has a nice sound and is free.

As DACs can be dirt cheap and good media players are free, it is a no-brainer.

spec

 

[audioguru]

You say you want "cheeky" bass. What is that?
You want "synthetic" bass at only one frequency that sounds like the resonance of a very cheap speaker. It sounds very bad.
You say that your computer speaker system has "dead bass" but its speakers sound good when connected to a big amplifier. Then if the speakers are not overloaded by the big amplifier then use them with a big amplifier. An LM1875 produces up to 21W into 4 ohms or 8 ohms when it has a 50V power supply. Your computer speakers might be destroyed with more than 5W.

What is a "compression speaker" and what is "combined sound"?

 

[Tony Stewart]

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

We know from speaker impedance plots vs f that impedance is an average and depends on both the sound pressure and electrical impedance. I checked a 6" full spectrum speaker on an LCR meter and recorded at 120Hz 2.5 Ohm 80uH and at 1kHz 2.5Ohm and 800uH. I might expect like a linear motor the no load impedance to rise and pressure loaded impedance to drop. except for a motor the DCR would be 10 to 20% which implies a start surge current of 5 to 8x max rated current.

What I don't know is if impedance changes with power applied as air power loading increases with air moved. A motor effective impedance changes from no load to load at constant input voltage due to mechanical load..43

But Air pressure in each direction is not a linear modulation of 1 Atmosphere


In any case Back pressure response on a Step waveform will induce resonant current which looking back into the PA output impedance must be shunted otherwise it results in an error voltage. I haven't personally verified the effects of Dampening Factors on many speakers, but on large high quality speaker cabinets I recall a salesman I went to school with indicate he did a blind test with a room full of critics and found significant approval just by changing the speaker wire from AWG14 to 00 welder's cable. This would be comparable to changing the dampening factor from 50 to 500 on a high power Amp. I suspect it would make no difference on poor speakers but evidently makes a big difference on high quality large cabinets.

 

[spec]

Wow Tony,

Thanks for the excellent summary.

My feeling is that the interface between an audio power amplifier is very complex and generally unsatisfactory in many cases, especially with highly reactive cross-over networks.

As you say, some systems sound OK with any set up while the more top-end gear is quite sensitive to cable type, cable length, connector type etc.

spec

 

[audioguru]

Damping Factor demo:
Take a loudspeaker that is in an enclosure with no connections and thump its woofer cone with your hand. It will make a resonant "bong" sound like a bongo drum. Then short its connections with a piece of wire that has the same 0.04 ohms or less resistance as the output impedance of a modern amplifier and thump its cone again, no resonance. If the crossover coils are good then their resistance is very low. The cable between the amplifier and speaker should also have low resistance.

A good amplifier damping ratio determines if a woofer (and a mids squawker and a highs tweeter) resonates all the time like a bongo drum or plays music properly.
I think series connected guitar speakers resonate like crazy (especially if they have the same resonant frequency and high impedance at resonance) because the series connection ruins the amplifier damping factor and old vacuum tube amplifiers had a low damping factor anyway. Old speakers in vacuum tube days were made to damp themselves.

 

[spec]

There is also the, click_bing_bong test.

You touch a 1.5V battery across the speaker terminals: if you get a click the speaker is over-damped and if you get a bong the speaker is under-damped.

spec

 

[audioguru]

A battery has a fairly low resistance so when it is connected to a speaker you should hear a damped "thud" and when it is disconnected you will hear an undamped "bong".

 

[Tony Stewart]

Actually batteries vary widely in ESR and LiPo could be in the 5m~10mOhm range while Alkaline in the 100~300mOhm range and make a distinct difference in the resonance effect.

So an Alkaline simulates say a DF = 8/200m=40 while a good LiPo simulates a potential DF of 8/8m = 1000 unless degraded by crossover.

I have not used a high end stereo for a long time and am satisfied with my el cheapo recycled Yamaha monitors and sub-woofer, but some day I may do some tests with speakers using crossovers and pay special attention to the FM modulation distortion than can only be measured using Intermodulation measurements with multiple tone sources. The FM effect is the Doppler effect of the max f in the crossover modulate by the lowest frequency that ithe media plays and system responds to. Thus the FM shift is 1/2 of the ratio of crossover range of the speaker .i.e. 1/2 of fmax/fmin which for 20 to 2kHz is =/-50Hz FM deviation on a 2kHz tone amplified and dispersed by 20Hz bass. I may have to get the Polk Audio system to appreciate this. I already have the Home Video system with a wide screen at 1m distance in the Rec Room with free 1080p movies on Kodi.

I have the Popcorn too. Next just need the 5.1 linear phase high dampening factor, low IMD amp and speakers to replicate true studio quality sound mastered in some movies.

I think the woofer should be mounted under the lazy boy rocker chair to replicate true earthquake feelings of some movies. Or add ag 's jackhammer bolted to the frame or get the mechanical massage motors built into some high end chairs sync'd to the sub-woofer.

Now that would really be going over the top. Mind you the US Festival in San Bernadino with its 1 Megawatt sound system was pretty awesome with 1M speakers arranged like a drive-in screen except in stereo. and Epcot centre's circle theatre with 8? screens and 8 sources of audio/video was pretty impressive with IMAX quality. (circa mid 80's)

 

[Tony Stewart]

For kicks I once put a LiPo cell across the primary of a 5000kVA transformer in a factory to see what happened. To my surprise the current rose slowly for 10 seconds indicating the primary inductance and then after 20 seconds started rising twice as fast just more than 1A for an average of 10Amp-seconds indicating the massive 3phase core was saturating. It had me wonder why they don't test transformers in factories for Remanence and abrupt current interruption out of phase from dropout where the cores saturate and act like a short circuit on the grid causing massive Hum until equalized in 1 to 30 seconds depending on design. They usually don't do short circuit tests to see if the windings blow up either. But I digress from audio battery tests.

 

[spec]

A battery has a fairly low resistance so when it is connected to a speaker you should hear a damped "thud" and when it is disconnected you will hear an undamped "bong".

Yes, I should have said when you connect a battery across a speaker.

A speaker that is correctly damped (mechanically) will not produce a noticeable bong.

spec

 

[awesomelumens]

You say you want "cheeky" bass. What is that?
You want "synthetic" bass at only one frequency that sounds like the resonance of a very cheap speaker. It sounds very bad.
You say that your computer speaker system has "dead bass" but its speakers sound good when connected to a big amplifier. Then if the speakers are not overloaded by the big amplifier then use them with a big amplifier. An LM1875 produces up to 21W into 4 ohms or 8 ohms when it has a 50V power supply. Your computer speakers might be destroyed with more than 5W.

What is a "compression speaker" and what is "combined sound"?

Perhaps you have messed up two different situations. Cheeky means excessively loud but amusing. I asked for can I get synthetic bass of a type i.e if I love a bass of a particular song and I can tune my amplifier to give that bass on other songs too. While omitting their original bass. The big amplifier is of big size and paired up with bigger speakers. I cant place it near computer nor it is free. I have a 19 v supply for lm1875. I can also make supplies with 24-30 volts. Compression driver is sometimes used with large speakers in place of or combined with tweeters.