Headroom question.

[TheRev]

I currently use an old model EA Doubler amp which is rated at 500w @4 Ohms. The new model of the Doubler has an uprated power amp rated at 650w @4 Ohms.

I'm considering buying the new model as I sometimes overdrive/clip my amp on big stages and I hope that the more powerful amplifier will give me more headroom and therefore reduce the chances of overdriving the amp.
Am I on the right track or talking bollocks? Will I even notice the difference between 500 and 650w?
Just to be clear - I don't need more output volume, I just want to stop the occasional farty noises.

Churrz

Dave.

*Edited for 4/8 Ohm typo.*

Edited October 23, 2017 by TheRev

[Lozz196]

I don`t know if you`ll hear much difference volume wise, but that extra 150 watts may be just the difference between the clipping, and not clipping, which is the aim. It has to be worth a try although I`d assume if being on a big enough stage to push a 500 watt amp into clipping surely you`re going through FOH? If so, ask for a better monitor mix.

[chris_b]

Can't answer your question, but one of the new features seems to be an HPF which might reduce the "farty noises".

//www.gollihurmusic.com/product/1825-EUPHONIC_AUDIO_DOUBLER_MARK_II_BASS_AMPLIFIER.html

[Hellzero]

To double the power, you'll have to add an extra 3 dB which is approximately 10 (yes ten) times the wattage... With 150 Watts more, there will be a slight improvement in clipping. Go to your cabinet (speakers) and try (in all terms) one that have at least 3 dB more or even better 6 dB, and clipping will be history.

[Bill Fitzmaurice]

[quote name='TheRev' timestamp='1508592587' post='3393164']
Will I even notice the difference between 500 and 650w?
[/quote]No. You need to double the power to get 3dB of additional headroom, which isn't all that much. Besides, nine times out of ten what you describe is caused by your speakers running out of excursion capacity.

[Phil Starr]

The new amp is 650 into 4 ohms not 8. That means around a 1dB increase in maximum output. 1dB is the minimum change ind sound level we can normally reliably detect. So no it isn't worth spending the money on. With that much power though you really shouldn't be struggling and people have mentioned the two things you could address. Use an HPF to remove the subsonics which you can't really hear but which will push your speaker to make farty noises and eventually damage them, or look to get a louder speaker.

[TheRev]

Thanks for the replies everyone.

I suspect that Bill is probably right and it's my cab farting out (although its a BigE/MAS45, which has pretty high excursion drivers).

I already use a HPF in my Fishman preamp, so that's covered.

In terms of volume, I'm not using the full 500w output as my cab is 8 Ohm, but at some gigs I'll have the input gain at 2 o'clock and the main volume at 3 - 4 o'clock, so I'm pushing the amp quite hard.

I probably need to add a second cab..... didn't want to have to do that, I haven't got anywhere to store the bugger...

[TheRev]

[quote name='Lozz196' timestamp='1508601892' post='3393252']
I`d assume if being on a big enough stage to push a 500 watt amp into clipping surely you`re going through FOH? If so, ask for a better monitor mix.
[/quote]

My cab is 8 Ohm so it's more like 300w than 500 (or does the load not affect input clipping?)
All my gigs are full fat PA jobs, but I'm playing double bass so I need to be careful with putting bass in the monitors as it can quickly degenerate into feedback city.
Having said that, I have had some engineers manage to give me an excellent monitor mix with bass in, but it's too few and far between to rely on for my onstage sound.

[chris_b]

Your MAS45 is the 4x5" Mike Arnopol cab? And it's farting out with 250 watts at 8 ohm? That doesn't sound right. This cab should be able to handle 250 watts.

On the MAS website, this cab looks like it's used in conjunction with a sub. Maybe it is struggling to handle the big lows that a DB can push out. I'd definitely try it with your HPF.

Do you get this problem with the other amps in your sig?

[Bill Fitzmaurice]

[quote name='TheRev' timestamp='1508663331' post='3393570']
its a BigE/MAS45, which has pretty high excursion drivers.
[/quote]Long excursion maybe, but they're still only 5 inch drivers. Four of them have less cone area than a single ten.

[mcnach]

[quote name='chris_b' timestamp='1508605482' post='3393300']
Can't answer your question, but one of the new features seems to be an HPF which might reduce the "farty noises".

//www.gollihurmusic.com/product/1825-EUPHONIC_AUDIO_DOUBLER_MARK_II_BASS_AMPLIFIER.html
[/quote]

+1

using a HPF has been a revelation for me...
In fact, rather than buying a new amp, I'd probably try getting a little adjustable HPF pedal first (Broughton Audio make one for around $90)...

edit: so you already use a HPF. Then I suspect the speakers are the limiting factor here... you might just be running into their limit and a more powerful amp would not help.

Edited October 22, 2017 by mcnach

[TheRev]

[quote name='chris_b' timestamp='1508668446' post='3393606']
Your MAS45 is the 4x5" Mike Arnopol cab? And it's farting out with 250 watts at 8 ohm? That doesn't sound right. This cab should be able to handle 250 watts.

On the MAS website, this cab looks like it's used in conjunction with a sub. Maybe it is struggling to handle the big lows that a DB can push out. I'd definitely try it with your HPF.

Do you get this problem with the other amps in your sig?
[/quote]

I don't know if it's the amp distorting at the input stage or the cab farting out. I'm pointing the finger at the amp as I generally run it at 3/4 on the gain and master volume.
I've spent some time working with the gain stages (plat pro input trim, plat pro output level and Doubler input gain) to make sure that I havent got any stupid variations in gain going on.

I haven't used the Markbass or BFM Omni10 in anger for a couple of years, so I can't recall if my current setup is any more or less farty.

The fartyness only really happens when I get a bit enthusiastic on the E string which is why I'm thinking that an amp with more headroom will cope with the occasional high peak. The question is whether the new Doubler with its 650W versus my current 500W will add enough headroom to make that difference - assuming that it's the amp that's overloading and not the cab.

[Bill Fitzmaurice]

Going from 500w to 650w won't make any difference. Depending on the tuning frequency of the cab chances are that the amp is putting out [i]less[/i] power at 40-45 Hz than at 50-55Hz, because the impedance will probably be higher at 40-45Hz than 50-55Hz. Excursion with equal voltage input is probably considerably higher at 40-45Hz than at 50-55Hz, and that's the likely source of the problem.

[Dood]

[quote name='Bill Fitzmaurice' timestamp='1508677977' post='3393688']
Long excursion maybe, but they're still only 5 inch drivers. Four of them have less cone area than a single ten.
[/quote]

I have to say that was my immediate reaction. I'd be very hard pushed to gig with a single 10" speaker, unless It was a sing song around Bagpuss's house with the mice.



edit: added smileys as I'm joking around

Edited October 22, 2017 by dood

[Lozz196]

That mouse organ pushes a lot of volume..................

[Al Krow]

[quote name='Bill Fitzmaurice' timestamp='1508705954' post='3393955']
Going from 500w to 650w won't make any difference. Depending on the tuning frequency of the cab chances are that the amp is putting out [i]less[/i] power at 40-45 Hz than at 50-55Hz, because the impedance will probably be higher at 40-45Hz than 50-55Hz. Excursion with equal voltage input is probably considerably higher at 40-45Hz than at 50-55Hz, and that's the likely source of the problem.
[/quote]

Bill, if I've understood the OP's post correctly it's 500W @ [b]4[/b]ohms versus 650W @ [b]8[/b]ohms, so if we are comparing like with like wouldn't this be 250W @ 8 ohms versus 650W @ 8 ohms? Let's assume they are both going into the same 8 ohm cab which can handle all the power either of these amps can throw at it (e.g. a BF Super Twin), then increasing the available wattage by 260% is surely going to have a more than negligible effect on audible volume and therefore the headroom?

[chris_b]

As was pointed out the new amp is 650w at 4 ohm, not 8 ohm.

[Al Krow]

[quote name='chris_b' timestamp='1508709178' post='3393987']
As was pointed out the new amp is 650w at 4 ohm, not 8 ohm.
[/quote]

Ah ok thanks Chris - I missed that.

[artisan]

Would a compressor help ?
It'll take out the spikes in your signal

Edited October 23, 2017 by artisan

[TheRev]

[quote name='chris_b' timestamp='1508709178' post='3393987']
As was pointed out the new amp is 650w at 4 ohm, not 8 ohm.
[/quote]

Yep, sorry - my mistake.

[Al Krow]

[quote name='TheRev' timestamp='1508759572' post='3394166']
Yep, sorry - my mistake.
[/quote]

Easily done Please feel free to edit your original post with a "correction" - to prevent folk like me annoying far more erudite cabsmiths like Bill!

[Chienmortbb]

If you are using an HPF and getting problems it may be that the cut- off is too low. Also as others have said if those little speakers are complaining, adding more watts will make them complain more and you will run into (more?) power compression.

Edited October 23, 2017 by Chienmortbb

[Phil Starr]

Sorry it's almost certainly your speakers. Sure they may be able to handle 250W but that is their thermal handling, They aren't going to handle the excursion at lower frequencies, as Bill has pointed out you have something smaller than a 10" single driver in effect. Your options are to roll off the bass, turn your amp down, use some compression, perhaps a limiter which will reduce the peaks, go through the PA or buy another or different speaker.

Edited October 23, 2017 by Phil Starr

[Dan Dare]

Don't 4 5" speakers have exactly the same surface area as a single 10"? Area of a circle is Pi x r squared. So 2.5 x 2.5 x 3.142 x 4 = 78.55, the same as 5 x 5 x 3.142.

[Bill Fitzmaurice]

The cone diameter isn't the same as the frame size. Even with the same frame size the cone area, T/S spec Sd, differs from driver to driver. There are some fives where four of them will have the same, or even more, cone area than some tens, but by and large they won't.

Edited October 26, 2017 by Bill Fitzmaurice