Bad Cabinet Overtone

[Backdraft]

Hi guys...I've got an unusual cab issue going on.

I just bought a brand new Splawn 4x12 guitar cab with their "small block" speakers installed to go with my Splawn Quick Rod head. Sounds killer except.......

When I hit a "D" note on the 6th string at the 10th fret I get a HUGE overtone of a second "D" note... but it's an octave lower happening at the same time. Cool....except I don't own an Octave pedal!?

If I hit any other "D" notes anywhere else on the guitar that overtone is still in there but not as noticeable. I've eliminated the guitar itself and amp head - it's definitely the cab doing this.

Anybody have any ideas on how to fix this?

A buddy suggested putting bricks or maybe a paint can inside the cab to change the resonating frequencies/air space. I'm not liking that idea so much as it would bring new meaning to the term "HEAVY" rock music!

Thanks for any suggestions.

 

[lolzgreg]

Sounds like a room resonance.

Download modecalc: http://www.realtraps.com/modecalc.htm

Put in your room dimensions.

If you get 146.83 Hz or 73.416 Hz, in mode calc, especially more than once, those are both D notes.

Cheers, and good luck.

 

[Backdraft]

Hi lolzgreg - thanks for the reply. I'm thinking that's not going to be the solution because the cabinet does this in different rooms. I'll try your suggestion though. Thanks again.

 

[Scumback Speakers]

The sound you're hearing is called cone cry. This happens from a few different sources in my experience.
1) One or more of the speakers is bad.
2) One or more of the speakers have been overtightened at it's mounting bolts and the frame is warped, which will also produce this sound.
3) The speakers are being sent too much power, or a fuzz/od/boost unit is set so high that it's pushing the speakers so hard that they react with that tone.

First thing I'd do is check your speaker installation for the bolt tightness. Here's how I do it.

How to install your speakers: http://www.scumbackspeakers.com/speakermounting.pdf

If the bolts aren't too tight, then you most likely have speakers that are either bad, or they don't have enough power handling limits to handle your amp.

Examples of this are as follows:

50w amp with two 30w speakers, 100w amp with four 25/30w speakers. You really need to have double the power handling in your speakers of the clean rated power of your amp.

So you'd need two 65w speakers for a 50w in a 2x12, or two 100w speakers with a 100w. For a 4x12 you'd need two 100w speakers in a 2x12, or four 65w speakers in a 4x12.

Good luck!

 

[::fred::]

do you hear the overtone on other notes?

 

[kirk]

The sound you're hearing is called cone cry. This happens from a few different sources in my experience.
1) One or more of the speakers is bad.
2) One or more of the speakers have been overtightened at it's mounting bolts and the frame is warped, which will also produce this sound.
3) The speakers are being sent too much power, or a fuzz/od/boost unit is set so high that it's pushing the speakers so hard that they react with that tone.

First thing I'd do is check your speaker installation for the bolt tightness. Here's how I do it.

How to install your speakers: http://www.scumbackspeakers.com/speakermounting.pdf

If the bolts aren't too tight, then you most likely have speakers that are either bad, or they don't have enough power handling limits to handle your amp.

Examples of this are as follows:

50w amp with two 30w speakers, 100w amp with four 25/30w speakers. You really need to have double the power handling in your speakers of the clean rated power of your amp.

So you'd need two 65w speakers for a 50w in a 2x12, or two 100w speakers with a 100w. For a 4x12 you'd need two 100w speakers in a 2x12, or four 65w speakers in a 4x12.

Good luck!

i agree sounds like cone cry,not that unusual to get a bad speaker every once in a while ,if you have other speakers you can swap the new ones out one at a time til you find the bad one ,it's probably only one of them,the other thing ,if you can remove the back panel altogether and play,..see if you still get it

 

[Backdraft]

Fantastic advice guys - thanks!
I'll try all your suggestions.

It's a Splawn 4x12 cab with 55 watt Eminence speakers being run by a Splawn 100 watt tube head which I had around 1/2 way up...1/2 volume. It's not that loud. The cab is brand new right out of the box. It appears to be extremely well built and rock solid. I have no pedals involved here...just guitar straight into the amp.

I did originally call Scott at Splawn amps on this and he was asking about it maybe being a bad speaker right away - so obviously his customer service is great and he stands behind his products. I did check the speakers as best I could but because the amp needs to be at that volume for the problem to happen I pretty much blew out these old ears trying to look for a funky speaker. Not in a hurry to do that again

I was just hoping maybe some of you had other ideas of what might be causing this as sending the cab all the way back is really not something I want to do and as I'm recording right now and actually using this rig, I'm looking for a simpler solution other than a bad speaker or whatever. Yup....kinda hoping all I need to do is adjust a screw or something but I know there's probably something else going on here that I'll need to deal with.

I'll try out your suggestions first thing tomorrow and post my findings in case anybody else ever has this problem. In over 40 years of playing I've never seen this before.

 

[Ventura]

The sound you're hearing is called cone cry. This happens from a few different sources in my experience.
1) One or more of the speakers is bad.
2) One or more of the speakers have been overtightened at it's mounting bolts and the frame is warped, which will also produce this sound.
3) The speakers are being sent too much power, or a fuzz/od/boost unit is set so high that it's pushing the speakers so hard that they react with that tone.

First thing I'd do is check your speaker installation for the bolt tightness. Here's how I do it.

How to install your speakers: http://www.scumbackspeakers.com/speakermounting.pdf

If the bolts aren't too tight, then you most likely have speakers that are either bad, or they don't have enough power handling limits to handle your amp.

Examples of this are as follows:

50w amp with two 30w speakers, 100w amp with four 25/30w speakers. You really need to have double the power handling in your speakers of the clean rated power of your amp.

So you'd need two 65w speakers for a 50w in a 2x12, or two 100w speakers with a 100w. For a 4x12 you'd need two 100w speakers in a 2x12, or four 65w speakers in a 4x12.

Good luck!

I'm opting with No.2 on this list - as weird as it may seem, I've heard the effects of overtigtening or even, uneven tightening, that when a special little frequency comes along, it resonates with the immediate environ and creates a dual or secondary vibration... In this case, what sounds like a secondary note.

If you have a mic, mic each cone in the 4x12 hitting this D on your guitar to a) see if it's global to the entire cabinet or b) isolated to only 1 cone in the 4x12.

V.

 

[Backdraft]

Quick Update - the tone only happens on the "D" note when played....no others.

I tried Ventura's idea of micing each speaker individually (thanks for that tip - way better than sticking my head in there) and the results were that while the overtone was still in there just a bit on EVERY speaker it was slightly louder in one speaker. Because I thought it might be unusual to be heard on all 4 speakers I then took the back of the cab off, played a D note, and the overtone seems to disappear almost completely. This cab is built like a tank...excellent quality. I see there is a bit of padding on the end of the bracing wood that would be pushing against the back wall of the cab. There is no screw there. I'll try a bit more padding there and maybe screw that brace in to the back wall and see what happens. I'm now thinking maybe the back wall is resonating too much. I'll let you know what happens.

 

[Scumback Speakers]

I think the Splawn cabs used to use a special bolt that you could really crank down way too hard if you weren't careful, I've had clients do this before, and reinstalling killed the problem.

Taking the back off isn't the solution, though, as the overtone will come back when you put it back on, if it's cone cry. Taking off the back allows the speaker cone to move freely without the closed air space affecting the cone movement. But cone cry can happen with open back cabs, too.

Not to bash Eminence speakers but I've heard this happens more than a bit with them, can't tell you why, but I've read about it on the net, and heard it myself when I owned a Private Jack 5 years back. Other speakers they make don't do it, though, so this just may be a bad batch, or one, and it needs to be reconed/rebuilt more than likely if the bolts aren't too tight.

 

[Backdraft]

I took a look at the speakers and they are bolted down with bolts that need Allen keys to tighten. Adjustment wise, they actually appear to be not tight at all...almost a bit loose actually...but tighter than "finger tight" for sure. I assume this is correct.

I put the back panel back on and just turned the amp down so I could continue recording. When I get time I'll try Kirk's suggestion of swapping out the speakers one at a time and see if that isolates the problem.

Thanks for the tips guys - very appreciated!

 

[glpg80]

I took a look at the speakers and they are bolted down with bolts that need Allen keys to tighten. Adjustment wise, they actually appear to be not tight at all...almost a bit loose actually...but tighter than "finger tight" for sure. I assume this is correct.

I put the back panel back on and just turned the amp down so I could continue recording. When I get time I'll try Kirk's suggestion of swapping out the speakers one at a time and see if that isolates the problem.

Thanks for the tips guys - very appreciated!

ive also heard that splawn will outsource the small/big block builds out to warehouse speakers if the eminence speakers are out of stock.

it is quite possible that if swapping them out you do not find the problem, being an eminence based issue as mentioned above, you could simply switch out to 4 WHS made speakers to the same specifications through scott splawn?

more headache than its probably worth, but if you love those speakers that is an option on the table.

 

[kirk]

keep us posted
on a second note,not sorta related,i had a modified 64 fender deluxe in here that had a crazy overtone but on the g string and only at the 12th fret,weird problem,i thought sure it was cone cry ,but 4 different speakers later,..its was still there,the customer gave me permission to track it down,i checked everything scoped it all out ,..nothing...i built a clone board and stuck it in ,...still there..i changed both transformers..still there...tighten anything and everything,still there,loosened everything ,..still there...wtf i said ,i consult several other techs who couldnt help,finally another buddy of mine said over the phone,"some of those fenders have an inherent trait of sounds like that ,he said to add the extention speaker and see what happens ,..ya know what...that worked!when you played with just one 12 you got that sound(barely audiable)but when you add a second 12 it disappeared...weird ,especially since i changed everything and it still did it unless i added the second speaker
the amp was modified by a real good tech here in ohio before i got it ,adding an extra gain stage,and the customer wanted it left that way,so i setup the normal channel as stock and it still did it,its the only deluxe that did that and i never had another do it and i've had half a dozen or better since then , weird ass problem that went unsolved
i personally could barely hear it ,unless he pointed it out by sitting the note for a few ,but when he was just playing ,i couldnt tell it was doing it,was very frustrating not to find it even though it was minor