Some advice on using PA and speakers needed

Hi,

I have my home-studio set up in my room and my acoustic drums are also there.

When I play the drums, I am listening to my favorite CDs and play along. The sound system was Technics amp and one pair of Jamo Studio 110 speakers. But the amp has broken (I get Overload message even at low sound levels).

So now I have to replace the amp and I am thinking of buying something like Samson Servo 600 or Servo 300 power amp.

http://www.samsontech.com...servo-series/servo600/

I will keep the Jamo speakers, they are rated 50W continuous, 91 dB SPL, 4 ohms

I have read on the web that the amplifier power of an amp should be at least 2 times the continuous power of speakers so Servo 300 or 600 will be enough.

But, I am not sure if I can use 300W (4 ohms) per channel output from Servo 600 into my Jamo speakers. Its more than 2 times the output power of the speakers so I am afraid that it will damage the speakers.

Can you help me with this? How should I set up the levels on the Amp so I will not damage the speakers but still gain maximum performance?

Thank you in advance.

In addition..
Voice coil heat-
Short term peaks don't generate a lot of heat- so this is where having the extra amp power fits in. -But there is the caution that like a sustained high instrument tone a musical instrument speaker is designed to take-  modern commercial music is highly compressed, that may apply here- to all the drivers.


Another guide to watch besides harsh sound and out right distortions and noises is woofer excursion.
The lower the frequencies, or the more bass boost, the farther the travel.
Don't know the specs (they might not be available),  could be +/- 1/2", maybe a bit more or less. But be wary of where 'lots more movement' crosses with 'little in gained volume.
 
'50W continuous', and I saw a back plate' image that said '105 short term(?) and 
'91 dB SPL'. (Presumably) that would mean they are moderately efficient speakers.
If that is reasonably true the saving grace is 50 watts continuous (average') would be quite loud. A fairly large portion of that likely is headed to the low end.
(Please, lots of just ball park stuff here..
 
Also note each doubling of amp power is just slightly louder. A few watts a low volume quickly multiplies to the 50-100, 100-200 watt jumps at the loud end. You can see where that can lead.

The signal coming out of the HP4 may be too hot for practical use but it probably wouldn't damage anything. If it was too hot it would have sounded completely distorted and fitzy for a while before any particular component melted due to to much voltage on the input. So if you set it so it sounded clean, you were probably ok.

Is the Monitor out on the HP4 meant to drive headphones or is it a +4dBu line level output.

I see you have the Main Out of the Edirol set to Unity. That's good practice for maximizing digital resolution. As long as you don't mess with that then anything you do after that stage to turn down the analog signal should be ok.

A 300watt amp in to 50 watt speakers will sound REALLY loud before you have to worry about much damage. Hopefully you'll just turn it down to a practical and workable level and never damage the speakers.

The tweeters may or may not be protected effectively from too much power... pay attention to what they sound like until you find a sweet spot.

If the tweeters or something in the speakers is going bad it can cause the amp to overload... so I'd consider inpsecting and testing the speakers if you think something broke the previous amp.

If I were you, I'd look up the manual on the Technics and find out exactly what the Overload message is meant to indicate.

best regards,
mike

 

The only easy way to check the speakers is to attach a multi meter to the inputs and confirm there is resistance. (We really want to measure for impedance, but checking resistance with a multi meter is the easiest and most practical to get an idea about the impedance.)

If there is a condition that causes over load on the amp it would probably be a short in the speaker system... it can happen in one of the crossover coils or the voice coil of a driver. The concern here is that it may only occur when the  speakers are up and running. Testing a static speaker with a multi meter may not reveal an existing problem.

The other type of damage to check for is an open circuit. It's unlikely that this is your issue as the speakers would be inoperable while the amp would be ok... although it might still throw some sort of warning message.

If you really think the speakers are part of the trouble then it is no fun to plug a fresh amp into them, but there are few other practical ways to check them.

The other possibility is that the amp simply has some small part that went bad. For example; I had a Technics amp I bought in 1978 that went through 2 routine replacements of power capacitors before I gave it away many years later.


Good luck!

best regards,
mike

You're actually better off putting a 300w amp into a 50w speaker than you would be putting a 50w amp into a 300w speaker. 

Of course, if you crank the amp up all the way, delivering 300w to a 50w voice coil will not be good for the speaker. Common sense is needed but this is a safer route. 

The 300w amp has the power to control the voice coil properly and no clipping will occur in the amp to power the speaker properly. Using a 50w amp trying to power a speaker that can easily handle 6 time the power can cause issues.  The smaller amp will reach clipping easier, and when it clips, you basically have DC flowing in the voice coil which creates heat.  As long as the coil is never fully extended and held there (by clipping) the heat is easily dissipated and the speaker continues to function properly as in the first example of the bigger amp, smaller speaker. 

Most amps have some sort of master volume or input signal attenuator on them these days. For example, I have a Carvin DCA-800, which, under the right load conditions, with a proper input signal is perfectly capable of delivering 400w per channel into a load. I used this amp for years pushing cabinets rated at 100w and never blew a speaker. Thats 4 times the rated power and not one speaker failure. I also used it on stage as a guitar power amp to run some 4x12's rated the same 100w per cabinet. I normally dialed the input attenuator back to 40% just for the sake of the sheer volume this combination was capable of delivering. 

A nice piece of hardware to have on any speaker system in a PA/monitor situation is a limiter compressor. It will weed out the big spikes and let speakers live long happy lives. 

We had a flash pot explosion one night at a gig. The flashpot was basically a fragmentation grenade. The pressure wave took out all the open back speakers on stage..... like cutting the cones out with a razor blade. However, in the PA system with the compressor/limiter, we did not loose but one speaker. All the monitor speakers were also blown. The compressor limiter stopped the pressure wave from going through the PA and putting us out of business. 

Hi Marek,

In my studio/music room set up ,I use a mixer. I run all of my direct signals thru the mixer ...ie amp modelers,electric drums a few Keyboards,sound modules,drum machine and my DAW. 

Then I use the mixer to monitor my DAW and have my Event BA 20/20's hooked up to the mixer. Every now and then I want to crank up a bit or jam with a buddy and did not want to do so and ruin my studio monitors so I bought a small pair of powered P.A. speakers and have them plugged into the mixer as well.

The whole thing works out nicely as I basically have everything in my room good to go without a lot of repatching and moving things around.........I can record or jam loudly in seconds. 

Anyway I know you were talking amps , but I really like the powered speaker set up.

I bought these................http://www.behringer.com/EN/Products/B212A.aspx 

and they work great,they run about $229.00 each U.S. or about 375.00 Euros a pair.

Here's how my room looks................

Desk w/mixer



Powered Speakers wall Mounted in Room



Good Luck
 

Thanks for heads-up on the Behringers.

Thomann has 212D for 205 EUR each. Not bad and my father will pay one half :)

However I am a little uncertain about how they sound. How would you describe their sound? Low end and clarity in mids and highs? I will have them connected to my mixer, so I can use 16 band EQ for adjustments.

Their freq response is 60Hz-18kHz. I assume I will not find 20Hz-20kHz active PAs in this price range :)

My room is approx. 17 m2 (182 square feet) big.

Hi Marek,

Keeping in mind the price point and the plastic enclosure, verses more expensive nice voidless  plywood enclosure.

I think the Behringers sound  pretty good.

I would say my Behringers are reasonably clean and tight, a touch heavy in the lower mids? Not to the point of being woofy.

They are no where near my Events.....for pure audio quality........obviously.Thats apples and oranges.

Mine are the 15" not the 12".......................so the low end is good.

I also own  a set of Madison dual 15" cabs w/horn passive crossover I use with An older and nice Alesis Gig Fx8 that is a fairly high powered unit and I will say the Behringers are just about as loud but waaaaay more accurate.

I don't believe they are physically rugged enough to  be rental or tour grade.

More reheasal or light use  in house system?

They do have a built in 2 band shelving EQ which is handy.............

It will also benefit the sound quality to have good s/n going in.

Good Luck

I too have a set of those plastic Peavey Speakers, Their only attributes are they are cheap and light. We use them for side fills and toss them on top of the pole mounted Yamaha's. They are not great sounding at all. They sound like a plastic box! Like I say the thing I notice is if you used them for mains is how much sound leaks from the back. I believe this must contribute to a bad sounding box. I was going to stuff them with pink insulation or spray the inside with foam. But I'm saving up for a set of the Behringers I think.

So my Behringers have arrived :). I had to reorganize my room in order to fit them inside :) But now they are ready.

I want to have the gain stage just right, so is it correct having the input gain on Behringers set to around 9 o´clock (first quarter) and every other fader on the route from my PC set to Unity? I will use the mentioned HP4 to attenuate the signal before PAs.

Thanks for your tips and help.