#1
How should I go about doing this? I found that after I finished making my guitar cabinet that there is very little bass if any. When I plug it into my Hughes & Kettner Switchblade 100 and I turn the bass from 0 to 10, there is very very little difference in the bass response but if I do the same thing with mid-range, treble, and presence, there is a noticeable difference.

So my question is, how do I go about porting this thing?
Last edited by gtrplyr at Sep 28, 2009,
#2
Is the cabinet completely sealed or open back?

I've noticed open back gives you less bass.
Imagination is more important than knowledge...
It is a miracle that curiosity survives formal education.
- Albert Einstein -
#3
Quote by Bertallica
Is the cabinet completely sealed or open back?

I've noticed open back gives you less bass.



completely sealed
#4
Quote by gtrplyr
completely sealed

Then you should be getting some decent bass. I don't think I've ever seen a ported guitar cabinet and I don't think it would make any different.

Porting a speaker enclosure is more for sub-woofers with long throws.

Be sure they are both wired + to + & - to -. If one were to be wired opposite then one would be firing backwards. This means it'd be cancelling the bass the other one is producing.

Also, have you checked the wiring vs the Ohm rating the amp has? Probably not the problem but just throwing it out there.
Imagination is more important than knowledge...
It is a miracle that curiosity survives formal education.
- Albert Einstein -
#5
Quote by Bertallica
Then you should be getting some decent bass. I don't think I've ever seen a ported guitar cabinet and I don't think it would make any different.

Porting a speaker enclosure is more for sub-woofers with long throws.

Be sure they are both wired + to + & - to -. If one were to be wired opposite then one would be firing backwards. This means it'd be cancelling the bass the other one is producing.

Also, have you checked the wiring vs the Ohm rating the amp has? Probably not the problem but just throwing it out there.



i'm almost positive i wired it correctly, i checked it over 5 times and i even had my dad check it over 5 times. we are going to open it up soon to see if letting the sound out of the back would help, ill check the wiring when we do that.

and there are a few ported guitar cabinets out there: http://www.zzounds.com/item--GEZGFLEX
#6
I commented on your other thread. I guess I wasn't paying close enough attention. I thought the cab was for a bass, so I brought up porting, oops. Does the bass control on your head work well with a different cab? If it doesn't, that may be the problem. If not, I got nothin'.
#7
Quote by gtrplyr
and there are a few ported guitar cabinets out there: http://www.zzounds.com/item--GEZGFLEX

I didn't say there weren't any. Just saying guitar speakers don't reach those low frequencies to require porting.

Playing with the back open won't help either. You'll get the same bass cancelling effect I mentioned earlier.
Imagination is more important than knowledge...
It is a miracle that curiosity survives formal education.
- Albert Einstein -
#8
Easy way to check speaker phase:

Take the two main input leads and connect them to the terminals of a 9V battery (doesn't matter which).

Each speaker should move about 1/2 a cm.

Check to make sure that they all move the same direction (doesn't matter which).

If they do, you're good, if not, switch the + and - wires of the offending speaker(s).
#9
Quote by Rutch
Easy way to check speaker phase:

Take the two main input leads and connect them to the terminals of a 9V battery (doesn't matter which).

Each speaker should move about 1/2 a cm.

Check to make sure that they all move the same direction (doesn't matter which).

If they do, you're good, if not, switch the + and - wires of the offending speaker(s).

If you did this + to + & - to -, then both speakers should move outwards.
Imagination is more important than knowledge...
It is a miracle that curiosity survives formal education.
- Albert Einstein -
#10
i will try these suggestions and report back, ill have my dad pop it open for me tonight
#11
After I looked at the GenzBenz, I must admit, I got interested in porting a guitar cab. THD does a long narrow shallow port across the back. That would probably be the easiest to try with a finished cab. I also saw a diy with similar dimensions to yours, with what appeared to be 2-2" holes at the top and bottom of the cab, on the centerline between the speakers. I don't know what tube length he used. My guess would be 4"-6". The guy really liked the sound.

It appears there are not really any set rules for how to port a guitar cab. It seems like people are still experimenting to get the sound they want. I don't see a definitive way to do it. I've got some stuff laying around, so I may even give it a go. As usual, some people like the sound, some don't.

I'd still make sure the bass on your amp is functioning properly first, otherwise it won't matter what you do with the cab.
#12
Ok we tried the 9v battery and they are both moving the same direction, what should we do now?
#13
Don't bother with porting a guitar cab. Porting is a well worked out process and there are mathematical formulae to work out port length, area etc but it wont really affect the frequency response above 80Hz which is below bottom E. Porting is for bass only.

Is the cab bass light or is it only that the tone control doesn't work? It may be that the tone control works on frequencies below the bottom frequency of your cab.

Is your cab airtight? even small leaks could be losing the loading on the speakers. Seal all the joints with silicone or acrylic mastic (caulk)

If the cab is too big for the speakers then they will be overdamped and lacking in bass, too small and they will be underdamped and boomy. Cabs have to be matched to speakers.

Please double check that the speakers are wired in phase. you don't need to take the back off so long as you can see the cones. Just connect a battery across the jack lead. I f the cones move in the same direction everything is good.
#14
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Quote by Phil Starr
Don't bother with porting a guitar cab. Porting is a well worked out process and there are mathematical formulae to work out port length, area etc but it wont really affect the frequency response above 80Hz which is below bottom E. Porting is for bass only.

Is the cab bass light or is it only that the tone control doesn't work? It may be that the tone control works on frequencies below the bottom frequency of your cab.

I'm not quite sure what you mean but when I turn the bass knob from maximum to minimum, I can only tell a very slight difference from having the knob at 1 and putting it to 0

Is your cab airtight? even small leaks could be losing the loading on the speakers. Seal all the joints with silicone or acrylic mastic (caulk)

It's airtight apart from the back panel which is just screwed in, the rest of the thing like the handles and jackplate we used something to seal it with

If the cab is too big for the speakers then they will be overdamped and lacking in bass, too small and they will be underdamped and boomy. Cabs have to be matched to speakers.

This may be the problem, the cab is pretty big, anything we can try to reverse the effect?

Please double check that the speakers are wired in phase. you don't need to take the back off so long as you can see the cones. Just connect a battery across the jack lead. I f the cones move in the same direction everything is good.
#15
Hi,

The first question is about whether the cab lacks bass completely or is it just a problem with the tone control?

To reduce the volume of a cab ( try halving it if possible) you need something solid to fill the insides temporarily, Try bricks if you have them to hand.

If you tell me which speakers you are using I can tell you what size cabinet you need so long as I can find the thiele/Small parameters for them.

Have you done the check to see if they are moving in the same direction when you put a battery across them?
#16
Quote by Phil Starr
Hi,

The first question is about whether the cab lacks bass completely or is it just a problem with the tone control?

I'm going to find that out soon when I take my amp and cab to guitar center by trying my amp on a different cab and trying a different amp with my cab to see what the problem is

To reduce the volume of a cab ( try halving it if possible) you need something solid to fill the insides temporarily, Try bricks if you have them to hand.

If you tell me which speakers you are using I can tell you what size cabinet you need so long as I can find the thiele/Small parameters for them.

G12K-100 Celestion Speakers

Have you done the check to see if they are moving in the same direction when you put a battery across them?

I did this and both of the speakers went in about a cm


fg
#17
The G12K 100 needs to be in a cab with a volume of about 15 -20 litres per speaker for maximum power and efficiency. Their resonant frequency is 85 Hz though so they are not a bassy speaker. If you put them in a cabinet of 60litres then the bass will be deeper but not so pronounced. Don't go bigger or smaller than these figures.

checking with another amp and speaker is a great idea

If you have checked everything else and they are still lacking bass then look at the speakers and check they are not leaking air.
Last edited by Phil Starr at Sep 29, 2009,
#18
Thats odd, the celetion website says the g12k-100 has the biggest low end of any of their speakers...


Damn, just calculated the internal volume and it's 113.8 liters. I'm guessing that's too much....
Last edited by gtrplyr at Sep 29, 2009,
#19
The trouble is that you can't believe the ads. To be fair what constitutes a 'big' low end is subjective. Does it mean that it genuinely reproduces the lowest notes cleanly or that it has a bass hump in the frequency response which gives a nice warm tone like JBL hi fi speakers.

85Hz is just about bottom E, but putting the speaker in a small cabinet will raise the resonance. The small air volume acts like a spring on the back of the cone tuning it upwards. It will also create a small bass boost just above resonance which will make the sound seem warmer. Increasing the volume will reduce the resonance of the speaker back down (in this case to bottom E) but you will lose the bass hump and some warmth.

If you search the net for information you will find that what you are doing is changing the systems damping factor or Q. 15 litres will give a Q of 1.1 which is the best for power handling and efficiency and will give you a bass lift above resonance. 60 litres per speaker, which is pretty much what you have, will give a Q of 0.7 which is perfect for the deepest, flattest frequency response .

Your cab is at the big end of what is sensible but should be fine. Making it smaller will trade genuine deep bass and a neutral sound for a bit of warmth and boominess.
#20
Quote by Phil Starr
The trouble is that you can't believe the ads. To be fair what constitutes a 'big' low end is subjective. Does it mean that it genuinely reproduces the lowest notes cleanly or that it has a bass hump in the frequency response which gives a nice warm tone like JBL hi fi speakers.

85Hz is just about bottom E, but putting the speaker in a small cabinet will raise the resonance. The small air volume acts like a spring on the back of the cone tuning it upwards. It will also create a small bass boost just above resonance which will make the sound seem warmer. Increasing the volume will reduce the resonance of the speaker back down (in this case to bottom E) but you will lose the bass hump and some warmth.

If you search the net for information you will find that what you are doing is changing the systems damping factor or Q. 15 litres will give a Q of 1.1 which is the best for power handling and efficiency and will give you a bass lift above resonance. 60 litres per speaker, which is pretty much what you have, will give a Q of 0.7 which is perfect for the deepest, flattest frequency response .

Your cab is at the big end of what is sensible but should be fine. Making it smaller will trade genuine deep bass and a neutral sound for a bit of warmth and boominess.



so is there anything i can do that will give me low end like a sub that ill actually feel when i hit those low notes?
#21
Um, I'm a bass player not a guitarist. I'm not sure I've ever felt the output from a guitar even with a bass I'd use an octaver to go that low and bass players generally use a lot more power and lots of speaker cone area to get that effect. It may be of course that I don't know quite what sound you are after. Have you heard a rig that gives you what you want or better still played with one?

I'm probably not the person to ask, I usually only really answer tech questions on speaker design or electronics.

Try out your cab with another amp and your amp with another cab. This should tell you if the cab is working as it should. If it is working ok but you don't like the sound then try reducing the volume of the cab to see if that gives a sound more to your liking.

If you want a really rich guitar sound without losing all articulation try out your amp with a 4x10 bass speaker. They will cover all the fundamental bass of a guitar but the cones should be light enough to give you some good cleans.

If you want any more help to get the best out of your cab let me know.

Good luck
#22
Quote by Phil Starr
Um, I'm a bass player not a guitarist. I'm not sure I've ever felt the output from a guitar even with a bass I'd use an octaver to go that low and bass players generally use a lot more power and lots of speaker cone area to get that effect. It may be of course that I don't know quite what sound you are after. Have you heard a rig that gives you what you want or better still played with one?

I'm probably not the person to ask, I usually only really answer tech questions on speaker design or electronics.

Try out your cab with another amp and your amp with another cab. This should tell you if the cab is working as it should. If it is working ok but you don't like the sound then try reducing the volume of the cab to see if that gives a sound more to your liking.

If you want a really rich guitar sound without losing all articulation try out your amp with a 4x10 bass speaker. They will cover all the fundamental bass of a guitar but the cones should be light enough to give you some good cleans.


If you want any more help to get the best out of your cab let me know.

Good luck



these are the 2 things i will try, itll probably be a while before i can get to guitar center though