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Please, recommend me a speaker for busking

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Re: Please, recommend me a speaker for busking

Postby James Perrett » Thu May 28, 2020 11:32 am

prako2 wrote:Does amperage matters? I found this one https://m.skelbiu.lt/skelbimai/nauji-ir ... 80519.html and in the picture it says that it's 750 A. What does it mean? And maybe I'm enough to have 600W countinuous inverter if I'm not going to play a music with distortion and damage my speaker. But I still don't understand one thing, in Thomann description it's written that HF is 300W and LF is 1000W and the rating is 1300W and it's written on the speaker. As I understand, 300W is equivalent to 300W RMS and what is higher than that, damages the speaker (when I turn up the too much volume on the speaker and hear a distortion).

The 750A marked on that battery is the absolute maximum current that you can take from it. That sort of current demand usually only happens when you are starting your car from cold and you can ignore it for what you want to do. The more important thing to look at is the capacity which is marked as 74Ah. In perfect conditions this means that you could draw 1 amp for 74 hours or 74 amps for one hour (but in practice things will be slightly different).

Active PA speaker specifications can be rather hard to interpret as manufacturers are often rather optimistic with their power ratings. The best guide is to look at the markings next to the power connector. For the Mackie Thump 15a this shows that the power consumption is only 75W so the 1300W specification is definitely "marketing" power rather than real watts. A 150W continuous power invertor would probably work but it might be safer to go for something like 300W to give you some headroom. At 300W you would be drawing 25A out of the battery (assuming 100% efficience) so the battery that you linked to would last just under 3 hours (if it was in top condition). At 75W you would have 12 hours life.
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Re: Please, recommend me a speaker for busking

Postby Sam Spoons » Thu May 28, 2020 12:16 pm

The Mackie's 75 watts will almost certainly be it 1/8th power consumption at full volume. Audio amps don't continuously draw full power from their PSU and a working figure of 1/8th of the RMS power of the amps is often quoted as the real world consumption*. I did a load of tests a few years ago when speccing a generator to run my own PA rig** and found this to be a useful approximation that stood up in real world usage.

Lead acid batteries don't like to be run down to nothing, in fact doing so can irrevocably damage them and will almost certainly shorten their service life. I'd consider 40% to be the minimum before recharging. Leisure batteries or 'deep cycle' batteries are better designed to come with frequent discharge to low levels so are better that car starter batteries for this job but rarely turn up cheap on the secondhand market. An inverter will protect your battery to some extent by shutting down when the supply voltage falls to 10VDC.

That battery powered PA will work fine but is complex, heavy and will probably cost more than you think. I built this (pics below) which runs for around 2 ½ hours from a built in sealed lead acid battery***. The inverter is a modified sine wave job which works fine in this context but I have had noise issues with a MSW inverter on other, more sophisticated, PA kit so would use a pure sine wave inverter if I did it again.

* 75 watts = 1/8th power so RMS ('continuous') = ~ 600 watts, 'peak' output = 1200 watts and if it was a car amp they would probably claim 2400 watt PMPO or 'music power'.

** https://www.soundonsound.com/forum/viewtopic.php?f=26&t=36681#p335876

*** It is also totally reversible apart from a few screw holes inside the cabinet and it is simple to plug a standard mains cable into the IEC receptacle on the back to run off 'shore power'. Total cost including the SLA charger was about £150, £80 of which was the combo.

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Re: Please, recommend me a speaker for busking

Postby prako2 » Fri May 29, 2020 12:55 am

Thank you, learned a lot. I think, this https://www.aliexpress.com/item/4000929 ... web201603_ 20Ah LiFePo4 battery would be the best choice. It should maybe last about 5 hours on a half of volume. Or this one for lower budget https://autodaliuparduotuve.lt/2673-dyn ... ovimo.html though a bit heavy, 8 kg maybe. Actually, I couldn't find a lighter deep cycle battery (about 20Ah).
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Re: Please, recommend me a speaker for busking

Postby prako2 » Fri May 29, 2020 11:13 am

https://www.aliexpress.com/item/3304150 ... jBizeyyOkE this one is even better. Has battery indicator.
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Re: Please, recommend me a speaker for busking

Postby Sam Spoons » Fri May 29, 2020 12:39 pm

A 12V/24AH SLA battery costs around £40 in the UK and weighs 9kg so those LiPo batteries are around ⅓ the weight and three times the price :D They look very nice TBH.

BTW, you seem to have searched for 'deep cycle' batteries and got 'motor cycle' batteries. They are different things, though with LiPo technology it shouldn't matter. But make sure you buy a suitable charger, 'normal' lead acid chargers don't work well with LiPo batteries as the charging requirements are different (it will charge the battery but will result in a shorter service life from what is a fairly expensive battery).
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Re: Please, recommend me a speaker for busking

Postby prako2 » Fri May 29, 2020 4:07 pm

You said:
Lead acid batteries don't like to be run down to nothing, in fact doing so can irrevocably damage them and will almost certainly shorten their service life. I'd consider 40% to be the minimum before recharging. Leisure batteries or 'deep cycle' batteries are better designed to come with frequent discharge to low levels so are better that car starter batteries for this job but rarely turn up cheap on the secondhand market. An inverter will protect your battery to some extent by shutting down when the supply voltage falls to 10VDC.

That motocycle battery doesn't have an indicator, I posted another battery below, it comes with DC charger. Do you think it's worth buying SLA not deep cycle one instead? I read that LiFePO4 battery life-time is 6x longer than SLA and I can damage SLA a lot by discharging below 40% (if you were talking about 24Ah not deep cycle battery for 40 GBP) also, my dad said that they degrade in the time by not using it and Lithium doesn't (not sure if it's true). I didn't find SLA battery that has an indicator as well.
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Re: Please, recommend me a speaker for busking

Postby Sam Spoons » Fri May 29, 2020 4:57 pm

I doubt you'll find a lead acid battery with a voltage readout though some car starter batteries have a crude indicator built in. Li-Ion/LiPo tech has a control and protection circuit built in which helps protect the battery, dedicated Li-Ion/LiPo chargers provide a charge regime that is tailored to the type of battery so help minimise degradation. If you can afford a LiPo battery go for it, just the light weight (2.7kg instead of 9kg) would be enough to convince me. I suspect the difference between LiPo batteries designed for motorcycles and those designed to run electronics or WHY will be in the control and protection circuitry, the former need to be able to provide very high amperages for a short period of time which a laptop battery does not need to do.

And, yes, I believe your dad is right, Li-Ion batteries do last considerably longer than lead acid.
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Re: Please, recommend me a speaker for busking

Postby prako2 » Sat May 30, 2020 5:15 am

https://drive.google.com/file/d/1O8qVSR ... p=drivesdk Just want to ensure if that 25Ah battery will work well and look what I got? I actually didn't understand what he said.
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Re: Please, recommend me a speaker for busking

Postby Sam Spoons » Sat May 30, 2020 10:03 am

He's right in the sense that to supply 600 watts the inverter will draw 50A from the battery (a little more actually allowing for losses) but your speaker will only be drawing around 75 watts which will require only 6 ¼A.

However, just to rethink this, you are looking at spending $140 on a battery, $40+ on an inverter and another $40 or more on a charger. When we were discussing DIY as a way of keeping the cost down it made some sense (which is why I did it with my VJ) but you are now at well over $200 just for the DIY power for the Mackie Thump.

I think it's time to research self contained battery powered speakers like the QTX blinddrew linked*, though I'd look for something which doesn't include wireless mics and other 'frills' look for the best speaker you can find and either buy a folding stool for a few dollars or limit your DIY to making a padded plywood seat to place on top.

* Selling the Thump should add a little to the budget and get you into $300 territory.
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Re: Please, recommend me a speaker for busking

Postby prako2 » Sun May 31, 2020 6:11 am

I read in the Mackie's manual that it has HF 300W and LF 1000W RMS limiters. From that, I understand that the max Gain knobs, max Main knob (see in the photo https://www.thomann.de/gb/mackie_thump_15a.htm) and full sound from PC (actually don't know if PC volume matters, tell me if you know) consumes 1000W continuously with bursts up to 1300W. So, if I set Gain knobs to the 1/2th, Main knob to 1/4th to get HF, should it consume 250W continuously and with bursts up to how many? If that's true, I'd discharge 25A battery in less than an hour by constantly playing a music because I read in some forum that power consumption (75W) is consumption when the speaker is idle, but in Youtube comment that 18W is when idle and 74W is 1/8 power consumption, not sure which is true. And I don't understand what's point to show 1/8 power consumption if the real RMS consumption is 600W. Also, you said that RMS of this speaker is 600W. By you, RMS is 600W because it's 8x 75W written usage. https://www.thomann.de/gb/mackie_srm_450_v3.htm This one has a power consumption of 160W but RMS in specs is 500RMS so it's not 1/8 anymore. I have no doubt that battery will work me but for me it matters how loud can I play it and how much will I consume at certain volume. I'd say 1/2 gain (tried only with 1 channel), 1/4 main knob and 1/2 of PC volume is loud enough for busking.

25Ah battery is with a charger so I wouldn't need to buy an additional one.
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Re: Please, recommend me a speaker for busking

Postby Sam Spoons » Sun May 31, 2020 10:32 am

prako2 wrote:I read in the Mackie's manual that it has HF 300W and LF 1000W RMS limiters. From that, I understand that the max Gain knobs, max Main knob (see in the photo https://www.thomann.de/gb/mackie_thump_15a.htm) and full sound from PC (actually don't know if PC volume matters, tell me if you know) consumes 1000W continuously with bursts up to 1300W.

No that's incorrect, without reading the manual I'm not sure about limiters but the 1000 watt LF and 300 watt HF is the power output of the two different amps driving the two driver units.

So, if I set Gain knobs to the 1/2th, Main knob to 1/4th to get HF, should it consume 250W continuously and with bursts up to how many? If that's true, I'd discharge 25A battery in less than an hour by constantly playing a music because I read in some forum that power consumption (75W) is consumption when the speaker is idle, but in Youtube comment that 18W is when idle and 74W is 1/8 power consumption, not sure which is true. And I don't understand what's point to show 1/8 power consumption if the real RMS consumption is 600W. Also, you said that RMS of this speaker is 600W. By you, RMS is 600W because it's 8x 75W written usage. https://www.thomann.de/gb/mackie_srm_450_v3.htm This one has a power consumption of 160W but RMS in specs is 500RMS so it's not 1/8 anymore. I have no doubt that battery will work me but for me it matters how loud can I play it and how much will I consume at certain volume. I'd say 1/2 gain (tried only with 1 channel), 1/4 main knob and 1/2 of PC volume is loud enough for busking.

25Ah battery is with a charger so I wouldn't need to buy an additional one.

Lots of misunderstandings and confusions here, I'll try to explain.

RMS is a standardised means of measuring the power output of an amplifier using a continuous sine wave signal, as such it is meaningless in the real world for anything but comparison. Music is not continuous, it varies in level constantly and features very short transients that are much louder than the average which the amplifier needs to be able to reproduce., The 1/8th power thing is just another way of guesstimating the power consumption of an audio amplifier when playing music. It's not perfect, EDM with a high bass content will consume more average power than guitar/vocal or classical guitar but it is a useful approximation. Your Mackie Thump will use around 75 watts of power playing typical recorded music at full volume. It's very easy to test, just buy a 'power monitor' plug like the one linked below and play some loud rock music through your Thump, the monitor readout will tell you how much power it is consuming.

HTH
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Re: Please, recommend me a speaker for busking

Postby Sam Spoons » Sun May 31, 2020 3:19 pm

I did indeed, thanks Mr S
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