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Converting 8 ohm cab to 4 ohm through new speakers


chrisaxe
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Hello,

Firstly, apologies if this has been asked before. I've had a little search and read some similar stories, but I just wanted to double check what I was doing was correct.

So I have an Ampeg SVT VR and currently run it at 4ohms through a 410 - sounds great. However, as the amp only runs at 4 or 2 ohms, it has made my 8ohm 210 cab redundant. I love this cab and for smaller gigs it is much more suitable that it's bigger 410 brother.

I have opened up the 210 and, as I thought, it has two 16ohm eminence speakers wired in parallel - giving the 8ohm total.

My question is, could I fit two 10inch 8ohm speakers, wired just the same in parallel, to give a total rating of 4ohms? And these new speakers are rated at 200w each - is that going to be enough when wired together for the 300w SVT?

Many thanks in advance,

Chris.

Just in case it makes any difference

- the cab is the TC Electronic BC210 ([url="http://www.tcelectronic.com/bc210/"]http://www.tcelectronic.com/bc210/[/url])
- the 8ohm speakers I was looking at wiring in are these Eminence Legends ([url="https://www.bax-shop.co.uk/bass-guitar-speakers/eminence-legend-bp102a-10-inch-speaker#specs"]https://www.bax-shop...h-speaker#specs[/url])

Edited by chrisaxe
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You're throwing away everything in this cab that makes the sound you love. It won't sound anything like it does now so. . . . is there really any point?

I'd buy a cab that you can audition and will give you the sound you want.

For me that would be a 4 ohm 212 or a the 4 ohm Barefaced Two10.

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The answer is yes to both points. Two 8 ohm 200W speakers wired in parallel will give a 4 ohm load and the amps power will be split equally between the two speakers, so 300W in will mean 150W to each speaker, comfortably within their 200W rating.

So, technically, yes it will work but Chris_b makes a very valid point above. It may well not sound as good.

Edited by 4stringslow
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I'm not so much in love with the sound of the 210 - what I am a fan of is it's portability and ease of use in smaller gigs. So I am happy to play around with speakers and change the sound of the cab.

Thanks 4stringslow - that clears it all up. I'll go ahead and swap out the speakers.

Cheers.

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[quote name='SubsonicSimpleton' timestamp='1467893737' post='3087080']
Don't waste your money modding, sell the 210 as it is and replace it with a portable 4ohm cab that you like the sound of.
[/quote]

I had considered doing just this, but it's going to be much cheaper to just swap out the speakers. The cab is cosmetically poor (it's been well gigged) and I wouldn't get much for it - certainly not enough to fund a new cab.

Whereas I can buy a couple of high quality Eminence speakers for around £150 and just fit them myself. Makes much more sense and saves me a fair bit of money.

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[quote name='pete.young' timestamp='1467914678' post='3087308']
Before you start spending money and dismantling good gear wouldn't it be a good idea to ask Ampeg if it is possible to run a single 8 ohm load off the 4 ohm tap?
[/quote]

Read another post about someone who asked Ampeg this very question, and they said it was not a good idea. Don't want to blow the output transformer on the amp.

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it is possible to run an 8 Ohm cab off a 4 Ohm ampeg all tube head (i did for a short while while awaiting my HLF 4 Ohm cab) without any problems but it is not recommended according to forums I looked into (something to do with shortning tube life? But I could be wrong). Likewise switching on a tube head without it being connected to a cab is a big no-no and waiting 20 minutes for the tubes to warm up before coming out of stand-by, and leaving the tubes to cool down after a gig before moving the head! So many new rules to learn!

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[quote name='skidder652003' timestamp='1467921630' post='3087390']
it is possible to run an 8 Ohm cab off a 4 Ohm ampeg all tube head (i did for a short while while awaiting my HLF 4 Ohm cab) without any problems but it is not recommended according to forums I looked into (something to do with shortning tube life? But I could be wrong). Likewise switching on a tube head without it being connected to a cab is a big no-no and waiting 20 minutes for the tubes to warm up before coming out of stand-by, and leaving the tubes to cool down after a gig before moving the head! So many new rules to learn!
[/quote]

I think you're right - at low volumes it would probably be fine but I'd rather not. Those things can be expensive to fix, even just to re-valve, so I'd like to play it safe!

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Yes, it's actually the output transformer that gets stressed with too high load. And the stress happens on transients, just an accident like plugging the guitar in pop, and it only takes one event if it's ever going to fail at all (which generally it doesn't phew!). Given the possible downside, it's best not to !

LD

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Before you do this you should be aware of the possible outcome.

Speaker cabs work by balancing the air load in the cab against the movement of the cone which acts as both a spring and a damper. In a ported cab like yours the port also tunes the cab to the speaker making sure you get the most output from the speakers and the best power handling. If you swap speakers around without anyone doing the calculations then two probelms might occur. You may not get a great sound and the bass might not be great. If you lower the power handling enough then your speaker might blow. They only handle the rated power in the right cab. Skidder will testify to that, he put two expensive speakers into two random cabs and lost one of them because the cab wasn't suitable. The other worked fine.

I'm not saying the swap won't work just that you need to get someone to check or it could be £150 wasted.

Worth noting that these are up for sale on BC http://basschat.co.uk/topic/287056-celestion-bn10-neo-speakers/

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