TCE BG250-208 MODIFICATION

[Downunderwonder]

On 11/12/2022 at 09:41, Jamieboy said:

I seem to have managed to bugger up putting the original speakers back in. They sound fine on higher notes but there sounds like there is a sort of buzz on the lower notes. I thought it might be that I hadn't tightened them enough and the speakers themselves were vibrating but tightened it further and not improved.

 

 

 

Upset with myself as I should have left it alone...

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

It sounds like you haven't caught the gist of the suck and blow warning. Swapping the leads on the one speaker will very likely it will cure it.

 

Having one speaker pushing lows while the other is pulling lows kills the low end dead. The effect is much less noticeable on the highs.

[blisters on my fingers]

1 hour ago, Downunderwonder said:

It sounds like you haven't caught the gist of the suck and blow warning. Swapping the leads on the one speaker will very likely it will cure it.

 

Having one speaker pushing lows while the other is pulling lows kills the low end dead. The effect is much less noticeable on the highs.

How would swapping the polarity cure a buzz?

[Phil Starr]

1 hour ago, blisters on my fingers said:

How would swapping the polarity cure a buzz?

It won't but to be fair it's almost impossible to describe a sound exactly in words.

 

A buzz could be something loose in the cab, check the speaker wires aren't rattling against anything. next thing to check are the speakers themselves: if they have been stored for a long time they may have deteriorated or may be damaged. Isolate them and try pushing them carefully back and forth, use a pint glass or similar to do this with even pressure and be gentle. Listen for any scratching sound when you do this. Examine the speakers carefully for anything that is torn or has become loose.

 

[Downunderwonder]

7 hours ago, blisters on my fingers said:

How would swapping the polarity cure a buzz?

Stop you from cranking it up endlessly to no good effect.

 

+1 -1 +1 -1 +1 -1 +1 -1 +1 -1 +1 -1 = zero but also +6 -6

 

JB kept going to 11.

[blisters on my fingers]

11 hours ago, Phil Starr said:

It won't but to be fair it's almost impossible to describe a sound exactly in words.

 

A buzz could be something loose in the cab, check the speaker wires aren't rattling against anything. next thing to check are the speakers themselves: if they have been stored for a long time they may have deteriorated or may be damaged. Isolate them and try pushing them carefully back and forth, use a pint glass or similar to do this with even pressure and be gentle. Listen for any scratching sound when you do this. Examine the speakers carefully for anything that is torn or has become loose.

 

 The above is the type of response that could well help somebody track down a buzz coming from a speaker cab.

 

I once bought a second hand cab online from a well known bass specialist shop. It buzzed like crazy on the lower notes, turned out their appalling packaging skills were to blame for this. A small piece of expanded foam had got wedged in between the cone and the basket.

That was the problem.

Cab still going strong no more problems.

 

6 hours ago, Downunderwonder said:

Stop you from cranking it up endlessly to no good effect.

 

+1 -1 +1 -1 +1 -1 +1 -1 +1 -1 +1 -1 = zero but also +6 -6

 

JB kept going to 11.

 

What is the point in talking in riddles?

 

So I'll ask again...

 

How does swapping polarity stop a speaker cab buzzing?

[Downunderwonder]

12 minutes ago, blisters on my fingers said:

So I'll ask again...

 

How does swapping polarity stop a speaker cab buzzing?

The buzz was described as occurring when trying to get some lows. Any amount of turning up is liable to cause driver conniptions when one is pushing while the other pulls in the same cabinet. The tuning is shot to hell with overexcursion happening at a fraction of the nominal power handling.

 

Instead of the power being applied to making lows it goes instead to making its cab mate fly in the opposite direction, and vice versa, while the combined audio output in front sums to zero.

[blisters on my fingers]

The buzz was described as occuring on the lower notes and not on the higher notes.

 

There is nothing at all mentioned about "trying to get some lows" or anything about turning up.

 

Are you seriously suggesting that one of a pair of speakers wired out of phase produces zero sound ? Really ?

[Downunderwonder]

3 hours ago, blisters on my fingers said:

Are you seriously suggesting that one of a pair of speakers wired out of phase produces zero sound ? Really ?

No. It's the just the lows that drop out and only mathematically. The result is the low notes have no oomph while the speakers move like crazy. That causes distortion best case and mechanical damage if not careful.

 

"Buzz" + "no lows" is entirely consistent with miswired speaker.

 

Could be there's a dud speaker there that caused the replacing in the first place? Do a battery test on them for a start.

 

A blown speaker has a similar effect to one that is miswired, moving opposite to the working one in the lows, and good potential for buzzing too.

[blisters on my fingers]

Maybe you could have proposed your "battery test" on the dud/blown speaker in the first place, rather than make some dubious claims that an out of phase speaker makes a buzz, produces zero sound, and/or "mathematically" drops out the lows.

 

That might have been helpful....

 

 

"A blown speaker has a similar effect to one that is miswired, moving opposite to the working one in the lows, and good potential for buzzing too."

 

Interesting that a blown speaker is so similar to a miswired speaker, of course it would move in the opposite direction............it's just physics isn't it?

 

[Downunderwonder]

3 minutes ago, blisters on my fingers said:

dubious claims that an out of phase speaker makes a buzz, ..

Not what I said. You made a leap from cure of dubious symptom to cause. Let it go.

[Jamieboy]

Thanks for the suggestions. I tried swapping polarity, checking connections and wire routing and generally inspecting the original speakers as best i could, but ultimately couldn't get them to sound right. 

 

 

 

I've put the Fane speakers back in. They do sound good so ultimately I at least have a functioning combo. Unfortunately it's still at 4 ohms so I can't extend from there.

 

In future I'll probably look to source 2x 16ohm speakers to use. Or just stop fiddling around and buy something else completely.

 

 

 

 

[Phil Starr]

Good decision, those Fane's are really great sounding things for bass, I built a cab for a friend and I have to say it was surprisingly good especially with double bass as it turned out.

[BassmanPaul]

You can check if you have the polarities correct by applying a 9V battery across the speaker cable. Both drivers should move in the same direction at the same time.

[Downunderwonder]

1 hour ago, BassmanPaul said:

You can check if you have the polarities correct by applying a 9V battery across the speaker cable. Both drivers should move in the same direction at the same time.

Only with the combo amp disconnected!!!

[BassmanPaul]

12 minutes ago, Downunderwonder said:

Only with the combo amp disconnected!!!

I would have thought that was obvious but good catch my friend.