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Post subject: Speaker design question
Posted: Thu Mar 31, 2016 5:32 am
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Aspiring Musician
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I've been wondering why we're so concerned with tube vs solid state, and so many other aspects of amplifier design that no attention is paid to the idea that good frequency response can't be handled only by a 8-10-12-15in speaker. Having owned high end stereo systems most of my life, I know there are different speakers to handle the highs, midrange, and lows but guitar amps limit themselves to a single speaker size that can't quickly and accurately handle the range of human hearing. So it seems to me that most other design issues are moot, or at least not that critical if the speaker can't project these signal variations. What am I missing here? Shouldn't a good guitar amp. have different size speakers to handle frequency range?


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Post subject: Re: Speaker design question
Posted: Thu Mar 31, 2016 5:53 am
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Roadie
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The frequency range of a guitar is pretty limited compared to the range on a stereo recording. The low E string is about 82 Hz open. The high E is about 330 Hz open. At the 24th fret, that's only about 1320 Hz. Add some higher harmonics caused by distortion effects, and you're still only talking 5 KHz max. Probably not even that high. I'm not trying to down play the importance of the speaker and it's cabinet - I agree it's usually overlooked. But a guitar amp's speaker requirements are much less that you would tolerate on your home stereo. .


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Post subject: Re: Speaker design question
Posted: Thu Mar 31, 2016 6:44 am
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You beat me to it, pdawg!

Another aspect to consider -- a full-range speaker system (20-20kHz) would likely make any noise inherent in the amp's circuitry more pronounced, especially above 10kHz.

There were a few companies back in the '60s that offered two-way speaker systems with their amps......Kustom, Acoustic Research, and Vox to name a few. That these models disappeared from their respective company's catalogs rather quickly speaks volumes.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Speaker design question
Posted: Thu Mar 31, 2016 7:57 pm
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Fender Acoustasonic 150 amp uses:

Two - 8" Foam-Surround Low-Frequency Drivers
TWEETER: One - High-Frequency Piezo Horn

So why is it that Acoustic amps include a HFreq Piezo Horn?

(I'm actually interested in buying one, for Electric guitar. The amp included models for Electric and Acoustics with effects)

http://www.fender.com/guitar-amplifiers ... 36&start=1


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Post subject: Re: Speaker design question
Posted: Fri Apr 01, 2016 9:27 am
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Roadie
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I was thinking an acoustic amp and speaker might be designed to cover higher frequencies to reproduce all the subtle tones of the acoustic body.


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Post subject: Re: Speaker design question
Posted: Fri Apr 01, 2016 11:40 am
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pdawg wrote:
I was thinking an acoustic amp and speaker might be designed to cover higher frequencies to reproduce all the subtle tones of the acoustic body.


+1

As well, many solo performers will run both their guitar and vocal mike into amps such as those and the two-way speaker system favors that scenario.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: Speaker design question
Posted: Sat Apr 02, 2016 9:38 am
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A home stereo is designed to reproduce music as accurately as possible.
A guitar amp is designed to replace the guitar's sound box and its characteristics.
You still have strings and a fretboard, but the tone balance and dynamics are handled by the amp.. Each design is as unique as guitar bodies. So rather than a PA, think of the amp as part of the musical instrument.
The single speaker is used to maintain tonal characteristics through the audio spectrum.
The sound characteristics of a guitar change when played through different speakers.
So the tweeter has one characteristic and the mids sound different.Iits difficult to maintain the same voice through different speakers.
To compensate for dropoff in a large speaker's treble sensitivity, the builders simply boost treble to compensate.
Its cheaper than a tweeter and doesn't create any acoustic phase distortion that multi-speaker arrays can't avoid at their crossover points..

Acoustasonics have a tweeter to reproduce the rich harmonics in the highest ranges of acoustic guitar..
While these harmonics may be too high to hear directly, their interactions produce secondary harmonics that do drop into the audible range
Many acoustic amps have extended frequency response with usable harmonics up to 35KHz.
The piezo tweeters are a feature that is cheap to add to an amp. They don't need a crossover because they are very high impedance at low frequencies. To my ear, they sound harsh and tinny. They are difficult to damage.
A dynamic tweeter needs a crossover or bi-amp, but has a more musical tone. They can have fragile voice coils however.
Ahh, the price of tone.


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Post subject: Re: Speaker design question
Posted: Sun Apr 03, 2016 7:59 am
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One could plug one's guitar amp into full-range home sound system speakers and report back on the sound quality. Or, one could plug one's home sound system into a couple guitar speakers and also report their findings. We'll wait here.


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Post subject: Re: Speaker design question
Posted: Sun Apr 03, 2016 8:07 am
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Rock Star
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Might be a good idea to limit the high frequency going from your home stereo into the guitar speakers. At least before you really crank it up. Simple crossover should suffice.

A friend once rigged up his McIntosh home hi-fi amp (200 watts) so I could plug in my guitar. It was a Telecaster. Man, did that sound terrible. Loud and sterile. No harmonics or overtones. Just a loud, super clean tone. Ear bleeding terrible. Don't try this at home.

;)


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Post subject: Re: Speaker design question
Posted: Sun Apr 03, 2016 6:44 pm
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Professional Musician
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Don't try electric guitar on home stereo speakers. Their suspension is too soft and the high gain of the uncompressed guitar will throw the voice coils right out of the basket. Like taking a cadillac to Baja.
A softstrum acoustic guitar or light jazz can sound wonderful on the same equipment.


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Post subject: Re: Speaker design question
Posted: Mon Apr 04, 2016 6:12 am
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Aspiring Musician
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Reading all the replies made me think that actually a guitar pickup and string work much the same as a phonograph cartridge and needle, don't they? The cartridge is a copper coil that reads the movement of the needle, much the same as the guitar strings and pickup work together. A phonograph cartridge and needle due to size and manufacturing control can much more accurately reproduce sound than a guitar and all it's variables, so maybe the speaker performance is less critical and maybe actually an asset in that most unwanted input doesn't make it out the speaker?


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Post subject: Re: Speaker design question
Posted: Mon Apr 04, 2016 7:22 am
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Pretty close. Both involve the use of permanent magnets and wound electro-magnet assemblies.

The tonearm cartridge converts movement of the needle in the record's grooves to electrical current within the wound wire portion of the cartridge.

The electric guitar pickup sets up a permanent magnetic field around the string. When the string is plucked, this changes the field around the string. The change to this field induces current flow within the wound portion.

In general, the voltage from a phonograph cartridge is less than most guitar pickups. Thus, the reason for the extra pre-amp stage within audio amplifiers that have turntable inputs. These TT pre-amps also have an RIAA frequency EQ circuit built-in to playback records, manufactured to this standard.

A similar type of EQ circuit is not necessary in the guitar amp gain stages.


https://en.wikipedia.org/wiki/RIAA_equalization


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Post subject: Re: Speaker design question
Posted: Thu Apr 07, 2016 1:25 pm
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Roadie
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Sometimes I play through a Zoom G3X pedal with an amp model activated into computer speakers. It's actually kind of pleasant.


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