Omni 12 resizing

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tallevan
Posts: 89
Joined: Sun Oct 20, 2019 12:15 pm
Location: London, England

Omni 12 resizing

#1 Post by tallevan »

Hi All,

I'm going down the dark hole of valve bass amplifiers.
Just purchased a Fender Bassman 135 head, and am now considering cabinets.

It's very big. 26" wide.
It shouldn't matter, but having it sit muffin-top style on top of a narrow cabinet would grind my corn.

So I'm considering building a non-tallboy Omni 12 for it. No tweeter, just a 3012LF woofer and the usual Alpha mid.

Questions:

1) Could I make it an inch wider without drama? If so, would I take an inch off the height?
2) The head is only 135 valve Watts, probably overestimated. So efficiency is a goal. The 3012LF seems relatively inefficient compared to the Deltalite II 2512 for example. Is the 3012LF a good choice for this application? I'm thinking the cabinet design makes up for this, or it might not be an audible difference. Thoughts?

Regards

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Bill Fitzmaurice
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Re: Omni 12 resizing

#2 Post by Bill Fitzmaurice »

An inch wider is fine, no need to reduce the height. For maximum sensitivity use two tens. Tube amps don't like 8 ohm cabs anyway.

tallevan
Posts: 89
Joined: Sun Oct 20, 2019 12:15 pm
Location: London, England

Re: Omni 12 resizing

#3 Post by tallevan »

Bill Fitzmaurice wrote: Tue Nov 02, 2021 10:44 am An inch wider is fine, no need to reduce the height. For maximum sensitivity use two tens. Tube amps don't like 8 ohm cabs anyway.
Thanks Bill. Worth checking.

I take your point on the 8 ohm cabs for tube amps.
This amp has an output transformer with a tapped secondary matched to either 4 or 8 ohm loads.
In fact, it was a Talkbass article to which you contributed a million years ago that pointed this out for this particular amp. Good to know.

So assuming two 8 Ohm 10" woofers, would the relatively efficient (97.3db) Deltalite II 2510 be a better choice than the relatively inefficient (92.7db) 3010LF? (@ 1W/m)

Or am I tilting at windmills?

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Bill Fitzmaurice
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Re: Omni 12 resizing

#4 Post by Bill Fitzmaurice »

The difference between those drivers is that the LF goes lower, useful if you run low B, and has more xmax, which matters not with only 135 watts.

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