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Single speaker lightweight 4 ohm cab?


1970
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Sorry to start yet another lightweight cab thread. I'm over the moon with the barefaced compact but would ideally like to drive my new amp at 4ohms instead of 8. Is there something similar to the BFC that runs at 4ohms?

Could always add a 2nd BFC or a midget - that's my plan B.

Edited by 1970
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I'd switch your plans around.

You'll get a little extra volume from the difference between running at 8 ohm and 4 ohm and very little extra tone, but you'll get a substantial increase in volume and improvement in tone between running one cab and two cabs.

Edited by chris_b
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[quote name='chris_b' timestamp='1385399564' post='2287764']
You'll get a little extra volume from the difference between running at 8 ohm and 4 ohm.
[/quote]

Even if this amp is solid state? The wattage doubles @ 4ohms... so I was thinking that headroom/volume would be a distinct bonus of running a 4ohm cab instead of 8?

Edited by 1970
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2 x eight ohm cabs wired parallel will give you a total load of four ohms so you get more power out of your amp and the bonus of greater cone area / displacement. ie it will be louder with two cabs than either a 4 or 8 ohm cab by itself.

Doubling the watts into a given speaker will only yield an extra 3dB in theory. In practice losses through power compression and other factors will reduce this further.

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[quote name='1970' timestamp='1385399670' post='2287766']
Even if this amp is solid state? The wattage doubles @ 4ohms... so I was thinking that headroom/volume would be a distinct bonus of running a 4ohm cab instead of 8?
[/quote]Wattage is moot. Volume is limited by voltage swing, and whatever you gain by increasing the voltage sensitivity into a 4 ohm cab is offset by the increased current draw. If you can't get the volume you need from an 8 ohm cab you don't need more power, you need a second identical cab. That will give you a 6dB increase, which equals quadrupling your power/doubling the voltage into one cab, assuming it could handle it, which it probably can not.

Edited by Bill Fitzmaurice
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It's a rare amp that actually doubles its maximum power at 4 ohms compared to 8. What is it?

Even if it does double, you'll gain only 3dB, which is not much.

The Compact is a fairly efficient cab. You could end up with a less efficient 4 ohm cab that will draw the maximum power from your amp without any increase in volume.

Edited by dincz
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[quote name='Bill Fitzmaurice' timestamp='1385402763' post='2287840']
Wattage is moot. Volume is limited by voltage swing, and whatever you gain by increasing the voltage sensitivity into a 4 ohm cab is offset by the increased current draw. If you can't get the volume you need from an 8 ohm cab you don't need more power, you need a second identical cab. That will give you a 6dB increase, which equals quadrupling your power/doubling the voltage into one cab, assuming it could handle it, which it probably can not.
[/quote]

What he said. And I know from experience that a dual Compact setup is pretty spectacular.

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It's arguably worth it if the amp is quite low power compared to the speaker thermal handling, and you're just after a little more clean headroom where a couple of dB can make all the difference.
That said there isn't an obvious 4 ohm equivalent of the 15" driver in your cab. Faital 15PR400 is probably closest but is still a dB or so quieter per watt in the low mids and is voiced differently, lacking the upper-mid 'bump' of the current driver so it'll sound a bit smoother, but a little less prominent in the mix.
If you like the current sound but want more heft, adding another Compact is definitely the best solution.

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Agree, adding a Midget to my Compact made a huge difference, much more depth to the sound but more "bite" as well. However as stated you like the sound of the Compact I`d look to get another for big gigs - think a dual Compact rig would be immense.

That said, I`m sure Alex at BF will be happy to recommend a solution.

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You could always buy my single-speaker 4 ohm light weight cab. At a fraction of the price of a BFC, and still with an Eminence driver..

Shameless plug here..[url="http://basschat.co.uk/topic/216488-purple-chili-115-eminence-neo-cab/page__p__2278771__hl__purple%20chili__fromsearch__1#entry2278771"]http://basschat.co.uk/topic/216488-purple-chili-115-eminence-neo-cab/page__p__2278771__hl__purple%20chili__fromsearch__1#entry2278771[/url]

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[quote name='1970' timestamp='1385399670' post='2287766']
....The wattage doubles @ 4ohms....
[/quote]

But the volume won't.

Is this just a bit of gas or do you really need more volume?

If you're current rig is underpowered then the most cost effective option is to add a second cab. Going to a 4 ohm cab will only work if it contains more speakers, like a 410. But, IMO, 2 Compacts will be better because they are practically as loud and much lighter.

Techy stuff is not my forte.... but I believe the increase in volume between 8 ohms and 4 ohms is about 3 db and that's a very small number to your ears, especially in a noisy band. Adding a second 8 ohm cab will give you an extra 6db, which is a difference in volume that you [i]will[/i] hear and, because you're moving much more air, will give you better tone.

I know someone using 2 Compacts and they get a great sound.

I’d check out the Compacts in the FS section.

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You generally get an extra 2dB more volume from the amps contribution by going 4ohm and 2dB more headroom. This is only just noticeable in absolute terms and only noticeable in practical terms if you hover at the point of distortion as Lawrence has said. As Bill points out by doubling the speaker count you'll get an extra 6dB, actually probably 5dB (3dB from the extra cone area and 2dB from the extra amp power)

Since you are using a very efficient driver changing the speaker will probably lose you a dB or two. (2-2=0 so no change in volume)
Most 4 ohm speakers sacrifice either efficiency or bass extension (Xmax) so you will probably be worse off.

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Another benefit of adding a BF midget is that this effectively gives you [b]three[/b] rigs:

Amp + Midget = tiny but surprisingly big-sounding rig - I also use this as my practice set-up
Amp + Compact = what you have now, and what I use for function band gigs
Amp + Compact + Midget = take no prisoners - I use this for loud rock gigs

Of course if you then get another (spare) head, you have the same all over again in a different flavour, plus you can have two complete amps set up for teaching (if that's your thang).

At the risk of stating the obvious, don't just add any other 8ohm cab to your Compact, as they are not likely to play together nicely, let alone look bitchin'!

Finally, if you are anywhere near Swindon, PM me to try your bass guitar and amp head through various Midget/Compact combinations. I can even play guitar while you do this to give you an idea how it would all sound in a band context.

Oops - have I stoked your gas!?

[font=comic sans ms,cursive][i]PS - I am not looking to sell any part of my bass rig.[/i][/font]

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OK so you are sorted for heads. Just buy a Midget! Plenty BF cabs going cheap(-ish) now as people upgrade.

I noticed your post in [url="http://basschat.co.uk/topic/223545-for-those-of-you-who-dont-drive-or-live-in-inner-city-areas"]this thread[/url] - a Midget on a bus or the tube would be no problem.

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[quote name='1970' timestamp='1385718158' post='2291393']
...This question is unfair....
[/quote]

How?

The question was do you [i]want[/i] to do this or[i] need[/i] to do this, i.e. do you have a need for more volume out of your rig.

We've given you a lot of opinions, but no one has asked why you want to do this.

You might get better advice if we knew.

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