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Discussion Starter · #1 ·
A while back I was thinking about experimenting with some kind of horn for a guitar cab. Bill Fitzmaurice and some others here make alot of sense and told me not to bother with a horn design. After some thinking, I came to the conclusion that a horn design, although being a fun project, would probably not yield anything useful to me.


I am going to build two separate designs, one closed back cab design and one ported design. After playing with winisd and guitar speaker TS parameters, I have found that most guitar speakers Fs hang around 90-110hz.


I played with a program called "Graphic Equalizer Studio 2011", with a multitude of guitar recordings played in various styles of music, but predominately heavy metal tones. After careful testing and taking notes, I found that cutting all the frequencies up to 100Hz made almost zero difference on the sound and resulting waveform. Removing the 80Hz slider took a tiny bit of oomph away, then turning the 100Hz slider down made a more substantial impact, enough to start messing with the commanding presence in the room.


Now when I enter most TS parameters from different speakers, they all react quite well to a 100Hz tuning for the ported cab. A very compact cab could still provide quite the boost in the 100-150Hz region when compared to a larger sized closed back cab.


In practicality, I tried out two ported cabs, both of which brought a very solid presence of low bass that I hadn't heard before.


So you wonder why in the hell I would want more bass in my guitar sound? I don't really want more bass - its more about efficiency. If I can build a guitar amp that doesn't have to provide as much bass, say a 3dB cut in the low end, I have just gained a bit more headroom for the rest of the response curve. This would mean that I can build a lower wattage amp to provide similar performance as a larger setup.


If I can pull any of this off, I can start building small 15-30watt amps, which are much lighter and portable to most musicians - then a small ported cab which could work in synergy with the amp to make it sound bigger. My goal is compact and efficient.


So my question would be more about input about this subject - how to approach the ported cab angle theoretically, based on practicality. I read that guitar speaker TS parameters are pretty much useless, since at 1 watt (level at which TS parameters are taken) their response is non-linear, and most of their application happens at much higher than 1 watt.


Thanks for the input, sorry for the long wind..
 

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it is a great post and way out of my league.


since the 'cab' of a guitar speaker actually serves to provide a lot of the harmonics that give it its timbre, i'd try to experiment with cabs that have a sound that you really like. i would not be surprised if these cabs had thin walls and little bracing, kind of like a real acoustic guitar. i would also experiment with the type of wood that is commonly used in musical intruments that provide a pleasant tone. the woods that are commonly used in violin and cello are spruce and maple. obviously, they resonate with a pleasant tone. then you have to choose a driver. that is going to be a pain as they all have a different frequency response and you can't experiment with them all. i'd probably look for something with a low qes and low inductance and relatively flat frequency response. then 'tune' it with eq to taste rather than relying on the driver. guitar cabs are something very new to me and i think that they are very interesting. i'll definitely be lurking here...
 

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Without going into a lot of detail, here are some things that should be considered.


Basically I think it is not a good idea-for the following reasons.


Not in any order


1: The amplifier is part of the musical instrument-with the amp and the loudspeaker working together to give the particular tone the musician is looking for.


2: Musicians are looking for a particular "sound" and that sound is often what would not be considered to be accurate-as in hifi reproduction terms.


3: It is a common misconception that by simply sticking a horn in front of a loudspeaker will make it louder. Yes it will make it louder (if the horn and the back chamber and the loudspeaker choice are properly done)-over part of the response range. But that range is limited.


On the low side-the overall size and pattern will determine the low point. As the pattern narrows, the size will have to be larger to give the same gain as a wider coverage horn.


On the high side (the part that most people forget-but it important if you want to reproduce the overtone harmonic structure of the guitar), the horn gain is limited by the size of the throat. If you want to get high, you are going to have to use small driver.


Do the math, but you are probably looking at a driver that is just a couple of inches or so-maybe less. Think-the highest freq you want (don't forget overtones) being about equal to the circumference of the driver.


Horns only operate over a limited freq range.


4: If the idea is to make a small cabinet-then a horn may not be what you are looking for.


Of course the final result cannot be determined by looking at a response graph or pretty much any other form of measurement. It is determined by the sound-and different people look for different things from a loudspeaker used for a guitar.


For example some people like the clean sound of JBL D120's while others like the crunch of Celestion Greenbacks. Others like the warmness of vintage american stamped drivers with paper voice coils.


It depends on your market.

But hey-give it a shot and see if you end up with something that works for you and your customers.
 

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also, for a six string with standard tuning, 82hz is the frequency of the low e string, so make sure that you can go at least that low, but the wheelhouse octave for the kind of guitar that you are describing is really 80-160hz or so, with harmonics going all the way up.


i wouldn't skimp on power though. the digital amps are really light and offer lots of power for not much money.


the real trick to a guitar cab is getting the "sound" that you want. it is definitely more like tuning a musical instrument than setting up a two channel audio system.
 

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Discussion Starter · #6 ·

Quote:
Originally Posted by Ivan Beaver /forum/post/20906219


Without going into a lot of detail, here are some things that should be considered.


Basically I think it is not a good idea-for the following reasons.


Not in any order


1: The amplifier is part of the musical instrument-with the amp and the loudspeaker working together to give the particular tone the musician is looking for.


2: Musicians are looking for a particular "sound" and that sound is often what would not be considered to be accurate-as in hifi reproduction terms.


3: It is a common misconception that by simply sticking a horn in front of a loudspeaker will make it louder. Yes it will make it louder (if the horn and the back chamber and the loudspeaker choice are properly done)-over part of the response range. But that range is limited.


On the low side-the overall size and pattern will determine the low point. As the pattern narrows, the size will have to be larger to give the same gain as a wider coverage horn.


On the high side (the part that most people forget-but it important if you want to reproduce the overtone harmonic structure of the guitar), the horn gain is limited by the size of the throat. If you want to get high, you are going to have to use small driver.


Do the math, but you are probably looking at a driver that is just a couple of inches or so-maybe less. Think-the highest freq you want (don't forget overtones) being about equal to the circumference of the driver.


Horns only operate over a limited freq range.


4: If the idea is to make a small cabinet-then a horn may not be what you are looking for.


Of course the final result cannot be determined by looking at a response graph or pretty much any other form of measurement. It is determined by the sound-and different people look for different things from a loudspeaker used for a guitar.


For example some people like the clean sound of JBL D120's while others like the crunch of Celestion Greenbacks. Others like the warmness of vintage american stamped drivers with paper voice coils.


It depends on your market.

But hey-give it a shot and see if you end up with something that works for you and your customers.

Oh i am not building a horn desing. I will be building a ported one - ported is what i am asking about..
 

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Quote:
Originally Posted by diaz /forum/post/20906438


Oh i am not building a horn desing. I will be building a ported one - ported is what i am asking about..

The same caveats apply. Guitar players want their drivers to go non-linear at low power levels, and one way to do that is with an open back cab, another is sealed. Bass reflex low end efficiency is for the most part unwanted.
 

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Discussion Starter · #8 ·

Quote:
Originally Posted by Bill Fitzmaurice /forum/post/20906562


The same caveats apply. Guitar players want their drivers to go non-linear at low power levels, and one way to do that is with an open back cab, another is sealed. Bass reflex low end efficiency is for the most part unwanted.

What do you mean by non-linear at low power? Speaker distortion/breakup?
 

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Quote:
Originally Posted by diaz /forum/post/20906438


Oh i am not building a horn desing. I will be building a ported one - ported is what i am asking about..

I can't tell you say I thought you were considering a horn, I guess I did not read your post close enough-or my mind was somewhere else (very likely).


So on that subject, most guitar cabinets (not talking about bass guitar cabinets) are either sealed or open back. There have been a couple of ported cabinets (Rolled and pleated kustoms with silver ports come to mind-but I bet those were more for looks), but not many over the years.


I can't say why, but there is probably a reason. Tonality would probably be the answer.
 

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Quote:
Originally Posted by diaz /forum/post/20906601


What do you mean by non-linear at low power? Speaker distortion/breakup?

Another desired non linear behavior is when the output transformer in a tube amp get saturated.


It is a "rounding off" and a "thickening" of the sound.


Of course this usually means that it is getting loud, but that is also part of the "fun". Hence the need for the "power brakes" and so forth. But even those were not as good sounding as the real thing.


Think old non master volume Marshalls. The Marshalls with a master volume (distortion in the preamp) had a totally different sound. Some people like that better, others not. It depends on what they are going for.
 

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Quote:
Originally Posted by diaz /forum/post/20906633


Ah yes, in my case, the distortion is strictly from the preamp. For that sound, the power section stays clean, and the speakers as well..

That's an option, but not one yet embraced by the mainstream. Most guitar players don't feel that purely electronically derived tone matches that of a Plexi, Twin or AC30 cranked into Greenbacks. And there's good reason for that, as a driver pushed into clipping by a tube power amp that's also clipping delivers a tone that can be emulated but not duplicated.
 

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This is way beyond me, but to get nice even order harmonics without the cabinet induced harmonics, why not go the vacuum tube preamp route?
 

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Discussion Starter · #15 ·

Quote:
Originally Posted by Looneybomber /forum/post/20907691


This is way beyond me, but to get nice even order harmonics without the cabinet induced harmonics, why not go the vacuum tube preamp route?

My amp will be entirely built out of 12ax7 preamp tubes, and 6V6 power tubes.. Its actually 90% done right now
 
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