Matching Cabs to Amps

[fdavidso]

Hi all,
I am just about to take delivery of a rather splendid Eden Nemesis CN115 combo courtesy of ShergoldSnickers (thanks again). The amp part is rated 250 watts in to 4 Ohms, but the internal speaker is rated as 8 Ohms. If in the future I was to need the full whack and so got an extension cabinet, what rating does it need to be? I understand the in parallel (CN115 requires rewiring for this) an additional 8 Ohm speaker would present a 4 Ohm load to the amp. But do the speaker(s) need to be (both/all - say a 2X10 extension cab) rated at 250 watts or is there some maths jiggery pokery with watts too?

Cheers

Dyce

[geoffbyrne]

You're right - you need another 8 Ohm cab in parallel. Providing both cabs are the same impedence, then they will both get the same power i.e. 250W split between both - 125W each, so get a cab with suitable rating.

G.

[JTUK]

And I would tend to get the same sort of cab taylormade to work with this combo/amp.

Some cabs suit some amps better than others, IME. so I'd start by checking out Nemesis cabs.

On TB, there are whole threads about amp/cabs matchups, and whilst it is pretty much true that any speaker will work as an extn cab, it will help if you start in the same ball-park.

IMV, the best chance of the best match-up, cab wise, is the same as what you already have.

[waynepunkdude]

Thing is it works well in theory but when you get to a venue with short change over time and you have to borrow the cab that is already onstage you usually find it doesn't make much difference in the real world.

But yeah always check impedance.

[fdavidso]

[quote name='geoffbyrne' post='929461' date='Aug 19 2010, 10:09 AM']You're right - you need another 8 Ohm cab in parallel. Providing both cabs are the same impedence, then they will both get the same power i.e. 250W split between both - 125W each, so get a cab with suitable rating.

G.[/quote]

Thanks for all the replies -

still a little unclear on one point. If a "cabinet" is rated at 125 watts, does this mean that all speakers inside that cabinet are rated at 125 watts or again is there a division process? (In half a mind to build a cab myself - so need to know what speakers to order if and when the glorious day ever came)

[farmer61]

[quote name='fdavidso' post='929692' date='Aug 19 2010, 12:51 PM']Thanks for all the replies -

still a little unclear on one point. If a "cabinet" is rated at 125 watts, does this mean that all speakers inside that cabinet are rated at 125 watts or again is there a division process? (In half a mind to build a cab myself - so need to know what speakers to order if and when the glorious day ever came)[/quote]

Generally realtes to the total power output, ie a 4x10 320w cab would have each speaker rated at about 80w

[ShergoldSnickers]

Hi there

If buying an extension cab new - [url="http://www.bassmerchant.com/item_detail.php?product_id=449&category_id=2#"]this might be the place to go[/url] - very good price. No, I don't get any commission, but I will say they were very helpful when I chatted to them.

I was actually thinking of getting this as an extension cab and then rewiring for parallel, before some very unexpected stray dosh meant I could completely rethink from scratch. The 2 by 10" cab looks to be quite sensitive, so should actually go louder than the combo speaker for a similar input of watts. At a later date, you could buy a dedicated amp, keep the 2 by 10", look at another cab to go with it and sell the combo. This gives an upgrade path should you want one. Don't worry about the 2 by 10" being rated at more than you technically require.

As for the alternative of building a cab - that's a good one. With the right design, you'll end up with a great cab that outperforms lots of commercial ones and will probably make much more efficient use of the watts fed to it.

[url="http://www.billfitzmaurice.com/"]Take a look here[/url] The 'Jack' range, Omni 12, Omni 15 or the 'Tallboy' versions of these are the ones to look at.

There is no way of knowing how a built cab would integrate with the combo though, and you'd have to be careful with impedance matching when buying the speakers to go in it. It's tempting though.

Snicks.

[fdavidso]

[quote name='ShergoldSnickers' post='930539' date='Aug 20 2010, 07:54 AM']There is no way of knowing how a built cab would integrate with the combo though, and you'd have to be careful with impedance matching when buying the speakers to go in it. It's tempting though.

Snicks.[/quote]

Hiya,
Yes - I can imagine 9 months of slogging in the shed to plug in and the whole lot goes up like a pantomime genie... Thanks for the links Snicks. I'll read with interest.