Car audio amplifier for outdoor bass use?

[Mottlefeeder]

I'm starting to put together a battery powered rig, which has to be loud enough to be heard with about 10 acoustic guitars in a pub, or busking outdoors. One option is to use existing amplifiers and speakers and an invertor and 12 volt battery, but the other option is to use a bridged car stereo amp with a battery.

I have previously run a 300W Hartke head into a 1*15 Hartke cab using a 300W invertor with a caravan battery, but the standing current is about 1.5 Amps and at normal playing volumes, the battery is delivering an average of about 3.5 Amps. Car audio amplifiers have a standing current of about 0.5 Amps, so the battery could be smaller and lighter.

To give me about 100W RMS into 8 ohms, I need something like 2 * 50W RMS into 4 ohms, which translates into an amplifier marketed as 300W to 500W depending on the manufacturer.

I'm think of the brands Kenwood, Alpine & JBL as being fairly good, but I have no feel for the other brands at the budget end of the market - FLI, Edge, Juice etc.

Can anyone advise me on the brands to avoid/consider for this project?

Thanks

David

[Thunderbird]

I may have missed the point but wouldnt it be easier to run a small combo to do this? certainly alot less to lug around

[Mottlefeeder]

[quote name='Thunderbird' timestamp='1386185865' post='2296938']
I may have missed the point but wouldnt it be easier to run a small combo to do this? certainly alot less to lug around
[/quote]

The acoustic sessions I attend, and the outdoor gigs I plan to attend, may not give me easy/any access to a 240v supply, so a combo on its own is not the optimal solution. In pubs without a performance area, they tend to have one socket for the vacuum cleaner, and one for the fruit machine, and sods law states that neither of them are anywhere near where you need them.

The combo I have is a 1 x 10, and weighs 15kg. Carrying it more than 100 yards needs a trolley, so it is feasible to put a caravan battery and an invertor on the same trolley, but a 4kg battery and a 2kg amp would fit in a rucsak and a neo-loaded speaker cab and bass could be carried by hand, which would be a much easier option.

A PJ Briefcase with battery would be heavier and only lasts one hour.

David

[MoonBassAlpha]

how about the E H 44 Magnum, runs off 24V 2A? 2 old Bike Batteries would do the trick, I would imagine.
I always thought it would be a good idea to try a small class D amp off a couple of cordless drill battery packs

[Mottlefeeder]

[quote name='MoonBassAlpha' timestamp='1386265302' post='2298002']
how about the E H 44 Magnum, runs off 24V 2A? 2 old Bike Batteries would do the trick, I would imagine.
I always thought it would be a good idea to try a small class D amp off a couple of cordless drill battery packs
[/quote]

A possibility, but quite low powered and expensive compared to dedicated auto designs.

On the subject of batteries, car and bike batteries are designed to run almost fully charged all the time, and do not take kindly to being fully discharged. For this kind of application I would need a golf cart battery or something similar.

David

[Dad3353]

DC watts, for our purposes, may be considered to be V x A. A 12v battery, delivering 100W, has 8A being drawn. Pro rata, 300W draws 24A etc.
A battery with a capacity of 10A/H may deliver 100W for about an hour or so. At 300W it'll run out after approx 15-20 minutes.
Hope this helps.

[Mottlefeeder]

[quote name='Dad3353' timestamp='1386291148' post='2298516']
DC watts, for our purposes, may be considered to be V x A. A 12v battery, delivering 100W, has 8A being drawn. Pro rata, 300W draws 24A etc.
A battery with a capacity of 10A/H may deliver 100W for about an hour or so. At 300W it'll run out after approx 15-20 minutes.
Hope this helps.
[/quote]

Thanks for your input - I agree with the theory, but the rig will not be delivering continuous power. There is an article on the EBS site about power requirements for bass amplifiers which states that the ratio between the peak signal of a plucked string and the average of the note is about 12:1, so you need the 100W for the first few vibrations of the string, and much less for the rest. My approximate measurements of average current drawn are in the same ballpark as the EBS figures, and show the audio power taking about 2 amps at 12V, and the losses for the invertor, power transformer, preamp, etc taking about 1.5A at 12V. Cutting down on the losses would make a big difference to how long the battery will last.

David

[MoonBassAlpha]

Don't forget, the car audio amp will expect to be fed with line level input, so you'll need a preamp to get the power out, and you don't need 300W of bass power to beat off 10 acoustic guitars, a Cube 30 or similar would be more than adequate.

[Mottlefeeder]

[quote name='MoonBassAlpha' timestamp='1386321203' post='2298628']
Don't forget, the car audio amp will expect to be fed with line level input, so you'll need a preamp to get the power out, and you don't need 300W of bass power to beat off 10 acoustic guitars, a Cube 30 or similar would be more than adequate.
[/quote]

I've heard a bass player using a passive Squire P and Peavey Microbass in this situation, and it was distorting as it struggled to keep up, which makes me wonder whether 30W will be enough - I agree with you that 300 watts would be overkill: that was a rig I used for an outdoor event.

I already have a Hartke Kickback 10, and that works for me, but takes up more space than I would like. My aim is to use a speaker cab that is the right height to sit on, so that I do not take up any more space than the other players - that tends to limit the number of combos I can consider.

My main interest in car amplifiers is that they are readily available, cheaply, second hand, so I can dabble and sell on if it does not work. Their sensitivities tend to be variable from 200mV up to 4V, so an active bass may be able to drive them with no further boost.

David

[Count Bassy]

[quote name='Mottlefeeder' timestamp='1386320432' post='2298617']
Thanks for your input - I agree with the theory, but the rig will not be delivering continuous power. There is an article on the EBS site about power requirements for bass amplifiers which states that the ratio between the peak signal of a plucked string and the average of the note is about 12:1, so you need the 100W for the first few vibrations of the string, and much less for the rest.
[/quote]

This is why the old Marshall DBS7400 is so good - a nominal 400W amplifier with a peak of 4000W. A 10:1 ratio rather than the more typical 2:1. (but it weighs a ton).

[woodyratm]

[quote name='MoonBassAlpha' timestamp='1386321203' post='2298628']
power to beat off 10 acoustic guitars
[/quote]

*Snigger*

[MoonBassAlpha]

well spotted Woody!

[mcnach]

Last summer I needed something portable for busking and I ended up with a battery operated "miniPA system".
It cost me under £150 and it worked beautifully. I never needed to crank it above 11am or so (if you imagine a clock face on the volume knob).




You can find more info on this thread:

[url="http://basschat.co.uk/topic/212137-portable-solution-for-busking-on-bass-new-amp-or-batteryinverter/"]http://basschat.co.uk/topic/212137-portable-solution-for-busking-on-bass-new-amp-or-batteryinverter/[/url]

[mcnach]

By the way, we ended up with three Roland Micro Cube amplifiers for the guitars, so they could get much louder than acoustics, and my amp coped perfectly with them and a strip down kit, plus trumpet and sax.

[Mottlefeeder]

[quote name='mcnach' timestamp='1386555312' post='2301480']
Last summer I needed something portable for busking and I ended up with a battery operated "miniPA system".
It cost me under £150 and it worked beautifully. I never needed to crank it above 11am or so (if you imagine a clock face on the volume knob).




You can find more info on this thread:

[url="http://basschat.co.uk/topic/212137-portable-solution-for-busking-on-bass-new-amp-or-batteryinverter/"]http://basschat.co.u...atteryinverter/[/url]
[/quote]
Thanks - I remember reading this and another thread earlier in the year.

I'm aiming more for a hand-carry system - The pubs I go to are old Victorian ones, with steps up to the door, which opens outwards. Getting in with a bass on my back is bad enough, but a bass and a trolley and steps is something I am trying to avoid. Also, to take up less space in the pub, I would prefer a rig that I can sit on.

David

[Phil Starr]

Can you put up a link to the EBS article on power requirements please? I've been looking for this sort of information.

I use the Hartke kickback10 for this sort of gig though only with mains, It's an awkward thing to carry due as much to its shape as it's weight. My 2x10 is lighter louder and a lot easier to carry.

I'm really not convinced you need 300W though, It is going to drain the battery pretty quickly and you will have to carry a correspondingly heavy battery. to reduce weight overall I would start with the speakers. Moving from Hartke's 92 dB/W to something like 102 dB/W would give you the same sound level with a tenth of the power. If you are prepared to compromise on deep bass you could easily use short throw speakers like guitar speakers which are much louder because more of the coil is in the magnet at any one time making electrical efficiency higher. There are drivers out there with intermediate characteristics that would give higher efficiencies too. My 2x10 built with ceramic magnet drivers and 18mm ply weighs only 17kg and has a sensitivity of 98dB/W and I'm sure I could achieve better if I designed for lightweight. This alone would give you the same sound output with a quarter of the power than using a less efficient speaker.

I haven't measured the output from my KB10 but it is going to be around 112dB, in any case this is limited by bass excursion as i can hear it distorting if I push it hard. If the Hartke is loud enough for you but just too awkward to carry then you only need that sound level. Using a 100dB/W speaker would only need 12db of gain so 16W of amp. A 30w amp would be louder and save your batteries, and you wouldn't be driving the speakers beyond their excursion limits so your bass would be cleaner.

[mcnach]

[quote name='Mottlefeeder' timestamp='1386590429' post='2301757']
Thanks - I remember reading this and another thread earlier in the year.

I'm aiming more for a hand-carry system - The pubs I go to are old Victorian ones, with steps up to the door, which opens outwards. Getting in with a bass on my back is bad enough, but a bass and a trolley and steps is something I am trying to avoid. Also, to take up less space in the pub, I would prefer a rig that I can sit on.

David
[/quote]


It looks bigger than it is!

When I received it I was like "what? is this it? they sent me the baby version or what?"

Look at the bass body for size. The bass is not resting on the floor, by the way.

Although it's made as a trolley, I *never* wheel it. In fact, I don't even use its handle, but grab it from the "trolley frame" at the back. It's tiny and very light. While I might not want to walk like that for 5-6 miles, trips from car to venue are a breeze.
I often used a trolley type travel bag, just for protection (in case it rains) and because I could carry the amp, a box of CDs to sell, a jacket for when it gets cold, a couple of FX pedals etc... so when busking in town and moving from one place to another it was easy to just dump everything in one bag. But if you just want to carry the amp, it's very comfortable to carry in your hand. It's too small and light to wheel it around anyway, and all the vibrations... I don't like that.

Anyway, I don't get commision for sales, so I'll shut up now I just wanted to clarify the bulk/weight issue.

When I got it I thought maybe I should have gone for the slightly bigger 12" version... but I'm glad I did not, as this is powerful enough and very compact.

[jazzyvee]

How about a PJB Briefcase that runs off the mains and also an internal rechargeable battery. It also comes with a lead to charge it from a car accessory point plus you can also clip a car battery to the external terminals on the back.
[url="http://www.philjonespuresound.com/products/download.htm?ft=download&id=8&fid=16"]User Manual[/url]

Jazzyvee

[Mottlefeeder]

[quote name='Phil Starr' timestamp='1386663981' post='2302692']
Can you put up a link to the EBS article on power requirements please? I've been looking for this sort of information.

I use the Hartke kickback10 for this sort of gig though only with mains, It's an awkward thing to carry due as much to its shape as it's weight. My 2x10 is lighter louder and a lot easier to carry.

I'm really not convinced you need 300W though, It is going to drain the battery pretty quickly and you will have to carry a correspondingly heavy battery. to reduce weight overall I would start with the speakers. Moving from Hartke's 92 dB/W to something like 102 dB/W would give you the same sound level with a tenth of the power. If you are prepared to compromise on deep bass you could easily use short throw speakers like guitar speakers which are much louder because more of the coil is in the magnet at any one time making electrical efficiency higher. There are drivers out there with intermediate characteristics that would give higher efficiencies too. My 2x10 built with ceramic magnet drivers and 18mm ply weighs only 17kg and has a sensitivity of 98dB/W and I'm sure I could achieve better if I designed for lightweight. This alone would give you the same sound output with a quarter of the power than using a less efficient speaker.

I haven't measured the output from my KB10 but it is going to be around 112dB, in any case this is limited by bass excursion as i can hear it distorting if I push it hard. If the Hartke is loud enough for you but just too awkward to carry then you only need that sound level. Using a 100dB/W speaker would only need 12db of gain so 16W of amp. A 30w amp would be louder and save your batteries, and you wouldn't be driving the speakers beyond their excursion limits so your bass would be cleaner.
[/quote]

Hi Phil,

EBS link - Oops, it wasn't EBS, it was TC - http://www.tcelectronic.com/rh450/support/ - the article is called 'TC Electronic bass amp power rating & Active Power Management'. Sorry if I've wasted your time looking in the wrong place.

I agree the Kickback 10 is great, but I wish it was lighter. The component parts weigh in at: speaker 3.2kg, amplifier module 4.3kg and case 8kg - about 15kg in total. I can carry that for about 100 yards, but beyond that it goes a on a trolley. One option might be to build a replacement cab using thinner ply with more bracing. I think I could lose 3-4kg from the cabinet weight by doing that, or alternatively, build a separate amp sleeve and speaker cab, so the amp can go in a rucsack, and the hand-carry would be lighter - but still mains powered.

The 300W rig I referred to was my normal gigging setup at that time, pressed into service for an outdoor event. It was powered by an invertor connected to a caravan battery (85AHr). It worked, but is not a serious contender for this job (Hartke HA3000 - 12kg-ish, Hartke VX115 - 20kg, battery - 18kg, trolley etc - 5kg: total 55kg-ish - doesn't do stairs).

I'm currently experimenting with an Eminence Basslite S2010 neo speaker in a 1cu ft reflex enclosure. It weighs 6kg, is the right height to sit on, and allegedly puts out about 95dB.

Stage 2 is to aquire a small 12 volt car-audio amplifier, and prove that the bridged 90-100W output gives adequate volume, and reasonable current draw, using the existing caravan battery. At that point I will have enough data to be able to size a lead-acid battery for a 3-4hr gig, and will be able to decide whether this is a runner or not.

Your comments on more efficient speakers are interesting - I had not thought of going that way. If the existing design does not work, that is certainly worth considering.

David

[MoonBassAlpha]

I think he dissed this PJB Briefcase idea earlier on in the thread, mainly for charge life, but they ain't cheap either....

Edited December 10, 2013 by MoonBassAlpha

[Mottlefeeder]

mcnach - thanks for the clarifaction - it is smaller than I first thought, so I will keep it in mind if the current experiment fails

jazzyvee - PJB looks good, but is quite expensive and think I read that the recommended battery only lasts an hour. Last night's session was 3 1/2 hours.

David

[muttley]

[quote name='Phil Starr' timestamp='1386663981' post='2302692']
I'm really not convinced you need 300W though, It is going to drain the battery pretty quickly and you will have to carry a correspondingly heavy battery. to reduce weight overall I would start with the speakers. Moving from Hartke's 92 dB/W to something like 102 dB/W would give you the same sound level with a tenth of the power. If you are prepared to compromise on deep bass you could easily use short throw speakers like guitar speakers which are much louder because more of the coil is in the magnet at any one time making electrical efficiency higher. There are drivers out there with intermediate characteristics that would give higher efficiencies too. My 2x10 built with ceramic magnet drivers and 18mm ply weighs only 17kg and has a sensitivity of 98dB/W and I'm sure I could achieve better if I designed for lightweight. This alone would give you the same sound output with a quarter of the power than using a less efficient speaker.

I haven't measured the output from my KB10 but it is going to be around 112dB, in any case this is limited by bass excursion as i can hear it distorting if I push it hard. If the Hartke is loud enough for you but just too awkward to carry then you only need that sound level. Using a 100dB/W speaker would only need 12db of gain so 16W of amp. A 30w amp would be louder and save your batteries, and you wouldn't be driving the speakers beyond their excursion limits so your bass would be cleaner.
[/quote]

Defo use a more efficient speaker for the reasons stated above, but not a guitar speaker. Guitar speakers usually have paper edge cones (ie one-piece diaphragm plus dust cap) which are not designed to move large volumes of air. Play a bass through one at anything higher than bedroom levels and you risk ripping the edge. Fine if you want to sound like JJ Burnel but I don't suppose this will go down too well in an acoustic set. If you can find a guitar speaker with a cloth edge this might fit the bill (but note the comment in the quote about deep bass).

[MoonBassAlpha]

[quote name='muttley' timestamp='1386684324' post='2303046']
Defo use a more efficient speaker for the reasons stated above, but not a guitar speaker. Guitar speakers usually have paper edge cones (ie one-piece diaphragm plus dust cap) which are not designed to move large volumes of air. Play a bass through one at anything higher than bedroom levels and you risk ripping the edge. Fine if you want to sound like JJ Burnel but I don't suppose this will go down too well in an acoustic set. If you can find a guitar speaker with a cloth edge this might fit the bill (but note the comment in the quote about deep bass).
[/quote]

Don't agree with this at all.
I used to use an old Cube 60 with a Sessionette 75 on top of it with my bass, did lots of gigs back in the day and the guitar speaker (Celestion G12-80) is still absolutely fine. ymmv.

[fonzoooroo]

I've actually done this!...

I built a little battery combo using a maplin "flight" tool case, a random 10" driver I had, a cheap car amp and a 12V lead gel battery.(the battery was the only bit I bought new) ... I used it with bass guitar and EUB for pub trad folk sessions. Battery life was fine (ran for hours - charged it before each session, never ran it to flat), plenty of volume, sound was technically a bit poor (due to the enclosure resonating/flexing/rattling a bit!) but adequate- the resonances gave the sound a bloomy, acoustic quality which, though it was a sound I'd never WANT to achieve, worked nicely!

As for brands of amp, I've had a couple of "Mutant" amps running in cars, a "Boss" (no relation to the Roland/Boss we know!) ... I never spend over £25 on an amp - 2nd handers off ebay are always available. Clearly, if run flat out, the cheapies are more likely to struggle than a Phoenix Gold etc, but you're unlikely to really run it that hard.

[Mottlefeeder]

[quote name='fonzoooroo' timestamp='1386941446' post='2306650']
I've actually done this!...

I built a little battery combo using a maplin "flight" tool case, a random 10" driver I had, a cheap car amp and a 12V lead gel battery.(the battery was the only bit I bought new) ... I used it with bass guitar and EUB for pub trad folk sessions. Battery life was fine (ran for hours - charged it before each session, never ran it to flat), plenty of volume, sound was technically a bit poor (due to the enclosure resonating/flexing/rattling a bit!) but adequate- the resonances gave the sound a bloomy, acoustic quality which, though it was a sound I'd never WANT to achieve, worked nicely!

As for brands of amp, I've had a couple of "Mutant" amps running in cars, a "Boss" (no relation to the Roland/Boss we know!) ... I never spend over £25 on an amp - 2nd handers off ebay are always available. Clearly, if run flat out, the cheapies are more likely to struggle than a Phoenix Gold etc, but you're unlikely to really run it that hard.
[/quote]

Useful stuff - thanks

My main problem with the ebay stuff is that I don't know whether it is reasonable quality, or poor quality stuff that previous users have grown out of. Coupling that with typical prices of £25 for the amp + £10 to post it, and I start to think that maybe a £50 'postage free', new one with a guarantee might not be such a bad idea.

Anyhow, it's good to know I am following a path that thas been travelled before.

David