Wiring cabs to amp...need some urgent input on this...

kiulseth · 1st February 2010, 12:10 AM

Hi folks...newbie talking here, so please bear with me

I need maximum loudness out of this setup:

The scenario is a Marshall Valvestate 80 + 80 watt poweramp and two cabs 16 ohm each.

The options are one cab on each channel of the amp, or the two cabs wired in parallel on one channel.

Try and listen is not possible at the moment, I need some theoretical answer to this, please.

Regards from near the north pole

firechief · 2nd February 2010, 06:01 PM

Kiulseth -- I am having a hard time pinpointing just what amp you have. Could you post a link to a technicial description of the beast? From the title it sounds like you have two seperate power sections, although that is pretty rare. If so, you must connect a speaker of the approriate impeadance to each output to avoid possible damage. So right off the bat one speaker on each output sounds right. Also a picture would help. No matter how you cut it the total power avaiable is just that.

godfrey · 07:33 PM

Is it one of these? Marshall Amps :: Heritage

That looks like a two channel amp with one 12" speaker built-in?

Sounds like a solid-state output so there's no impedance taps?

If one amp channel is used for a built-in speaker, then it's probably best to connect both 16 ohm cabs in parallel on the other channel.

If not, then a separate amp channel for each cab might give a bit more power.

edit:
[rant]Whole pages of waffle on their website about how great it sounds, but no mention of how to connect or use it - not even in the PDF "manual"

[/rant]

kiulseth · 4th February 2010, 12:03 PM

Hi again, thanks for the replies, and sorry for my late respons....was away for a couple of days

The amp is a Marshall Valvestate, Model 8008. Rackmounted SS power amp.

PDF: http://www.drtube.com/schematics/mar...4-8008-hbk.pdf

Two inputs, two outputs 80 watts each, bridging not recommended (they say it can kill the amp).

Racket Scientist · 8th February 2010, 11:17 PM

The PDF doesn't specify the recommended impedence load, but amps designed for guitar generally tolerate mild impedence mismatches well. Its probably designed to take an 8 ohm load per channel. I'd put a cab on each channel.

infinia · 9th February 2010, 12:47 AM

Quote:

Originally Posted by kiulseth

Try and listen is not possible at the moment, I need some theoretical answer to this, please.
Regards from near the north pole

Your answer is ...Run them in parallel for an 8 ohm load on one channel.

Amps (voltage FB) that are rated for it, provide more power at a lower impedance ( ohms law with fixed voltage).
Your amp is rated for 4 ohms so 16//16= 8 is no problem (see attached highlight)

Keep warm

Minion · 18th February 2010, 12:19 AM

Why don"t you just rewire each cab to 4 Ohms ,a 16 ohm 4x12 will have four 16 ohm speakers which wired in Pairs in paralell then each paralell pair in series to get 16 ohms , Which can also be wired with all 4 speakers in paralell for 4 ohms .....

That way you will get 4 times the output power from your amp and speakers ....

An amp that puts out 80w into 4 ohms is only putting out 20w into 16 ohms ....

It is simple to do and will make you a LOT louder .....

Cheers

1st February 2010, 12:10 AM	#1
kiulseth diyAudio Member Join Date: Sep 2008	Wiring cabs to amp...need some urgent input on this... Hi folks...newbie talking here, so please bear with me I need maximum loudness out of this setup: The scenario is a Marshall Valvestate 80 + 80 watt poweramp and two cabs 16 ohm each. The options are one cab on each channel of the amp, or the two cabs wired in parallel on one channel. Try and listen is not possible at the moment, I need some theoretical answer to this, please. Regards from near the north pole

2nd February 2010, 07:27 PM	#3
godfrey diyAudio Member Join Date: Nov 2009 Location: Cape Town	Is it one of these? Marshall Amps :: Heritage That looks like a two channel amp with one 12" speaker built-in? Sounds like a solid-state output so there's no impedance taps? If one amp channel is used for a built-in speaker, then it's probably best to connect both 16 ohm cabs in parallel on the other channel. If not, then a separate amp channel for each cab might give a bit more power. edit: [rant]Whole pages of waffle on their website about how great it sounds, but no mention of how to connect or use it - not even in the PDF "manual" [/rant] Last edited by godfrey; 2nd February 2010 at 07:33 PM.

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2nd February 2010, 06:01 PM	#2
firechief diyAudio Member Join Date: Sep 2008 Location: Near Seattle Wa	Kiulseth -- I am having a hard time pinpointing just what amp you have. Could you post a link to a technicial description of the beast? From the title it sounds like you have two seperate power sections, although that is pretty rare. If so, you must connect a speaker of the approriate impeadance to each output to avoid possible damage. So right off the bat one speaker on each output sounds right. Also a picture would help. No matter how you cut it the total power avaiable is just that.

4th February 2010, 12:03 PM	#4
kiulseth diyAudio Member Join Date: Sep 2008	Hi again, thanks for the replies, and sorry for my late respons....was away for a couple of days The amp is a Marshall Valvestate, Model 8008. Rackmounted SS power amp. PDF: http://www.drtube.com/schematics/mar...4-8008-hbk.pdf Two inputs, two outputs 80 watts each, bridging not recommended (they say it can kill the amp).

8th February 2010, 11:17 PM	#5
Racket Scientist diyAudio Member Join Date: Jan 2010	The PDF doesn't specify the recommended impedence load, but amps designed for guitar generally tolerate mild impedence mismatches well. Its probably designed to take an 8 ohm load per channel. I'd put a cab on each channel.

18th February 2010, 12:19 AM	#7
Minion diyAudio Member Join Date: May 2006	Why don"t you just rewire each cab to 4 Ohms ,a 16 ohm 4x12 will have four 16 ohm speakers which wired in Pairs in paralell then each paralell pair in series to get 16 ohms , Which can also be wired with all 4 speakers in paralell for 4 ohms ..... That way you will get 4 times the output power from your amp and speakers .... An amp that puts out 80w into 4 ohms is only putting out 20w into 16 ohms .... It is simple to do and will make you a LOT louder ..... Cheers

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