Help, its just toooooooo bassy

[mike_bax]

I've just built a compact 4x12 cabinet

Its built to the same size as the Marshall MG412 cab, (for the MGHDFX100 head)
Its loaded with Celestion GT12 75's, and made from 18mm (3/4") birch ply. (All of it, top, bottom sides, back and baffle board), I have the strut running from the baffle board to the back of the cab, so its all there, its just so bl00dy bassy.

Any ideas

PLEASE, SOMEBODY HELP

[überfuzz]

Are the speakers used or brand new? Some speaker need some 'fly hours' before they sound... great.

[mike_bax]

The speakers are nearly 20 years old.

They are from my old 4x12which I think was a Laney, but was reloaded with these speakers in about 1991

They sounded OK in that cab, but I built this cab around a month ago, and it has never sounded right.

They are wired in the standard "mono" way, the same as the above mentioned MG412 cab (i have had the back off our other guitarists one, and checked)

A friend of mine has said that if one of the speakers, for some reason is faulty, this may effect the sound of all the speakers, and that I should check them one by one, see if one is faulty, is this a possibility?

[pdf64]

A speaker fault is unlikely to be the cause of this.
More likely is that there's just not enough volume in this sealed box. What are the internal dimensions? Does taking the back panel off a little get rid of the boom?

[mike_bax]

Its not so much a boom, more of a bassy sound, thick and muddy.

I thought of this, so I cut 2 x 75mm holes on the back panel, but this made no difference

The inner dimensions, from memory, are around 650mm (wide) x 650mm (high) x 300mm(deep)

As I said, exactly the same as a Marshall MG421 cab, from which I took the measurements

I do have 4 x 50watt speakers in some old H&H PA speakers that I can try in it. This would I guess, tell me if the problem id the cabinet or the speakers.

Would a thinner baffle board that the speakers are mounted on help, say reduce to 12mm from 18mm

[mike_bax]

Don't know if this has any bearing, but as standard, an MG412 Cab has 4 x G12-30's in it, as opposed to my 4 x GT12-75's

[pdf64]

How about you take the back off completely?
I think Laney and Marshall use 15mm birch ply, cheaper Marshall also have chipboard for the back panel.

[loudthud]

Have you used a battery to verify that each speaker works and has the correct phase? (Hint: You must disconnect everything from at least one terminal of the speaker being tested.)

[oc disorder]

Sealed enclosures do accentuate bass response.
As Loudthud said check the phasing (polarity) of the speakers.
Normally a reverse wired speaker would cancel the bass .
I guess it would be series parallel so that 4 x 8ohm speakers have a total impedance of 8 ohms or 4 x 16 ohm speakers have a total of 16 ohms.
see attached diagram

[mike_bax]

Sealed enclosures do accentuate bass response.
As Loudthud said check the phasing (polarity) of the speakers.
Normally a reverse wired speaker would cancel the bass .
I guess it would be series parallel so that 4 x 8ohm speakers have a total impedance of 8 ohms or 4 x 16 ohm speakers have a total of 16 ohms.
see attached diagram

Yeah, from memory, thats how its wired, just like the diagram, should I change it?

[mike_bax]

Have you used a battery to verify that each speaker works and has the correct phase? (Hint: You must disconnect everything from at least one terminal of the speaker being tested.)

To be honest, I reallly don't know what you mean, I'm not "up" on the tech side of speakers, I just know how I want it to sound

[überfuzz]

1. What speakers do you have? 16 Ohm, 8 Ohm or 4 Ohm?
2. What output do you have, check for Ohms there as well.

Try to find the answer to nr 1 and 2. Then you/we will be able to establish how to connect the speakers in the cabinet.

[mike_bax]

1. What speakers do you have? 16 Ohm, 8 Ohm or 4 Ohm?
2. What output do you have, check for Ohms there as well.

Try to find the answer to nr 1 and 2. Then you/we will be able to establish how to connect the speakers in the cabinet.

1) Celestion G12T-75 (each rated at 75w/16ohm)

2) Amp is 100w @ 4 ohm (4 ohm is also the minimum load)

Cab is currently wired in series-parallel

Cab is sealed, but has 2 x 75mm holes in the back panel

[überfuzz]

Ok, you need to wire the speakers parallel to each other.

+ on speakers goes to + on output
- on speakers goes to - on output

Make sure you know the polarity on each speaker. You can check it with a 9V battery. When the speaker membrane pops outwards you've located the + and - of the speaker. + on battery shows + on speaker.

[mike_bax]

Ok, you need to wire the speakers parallel to each other.

+ on speakers goes to + on output
- on speakers goes to - on output

Make sure you know the polarity on each speaker. You can check it with a 9V battery. When the speaker membrane pops outwards you've located the + and - of the speaker. + on battery shows + on speaker.

A wiring diagram would help

The speaker chassis are marked for + terminals, can I trust this?

Will the cabinet still handle the power? I'm not up on wirings and ohms.