Advice on Purchasing Amp & Speakers

[Andy Dunn 0]

Thanks for your help,

 

a limiter would limit the signal coming from a mixer making it "impossible" for the amp to blow the speakers if set up correctly? Could you recommend a limiter?

 

This would match the system perfectly, 2x 700W

http://www.thomann.de/gb/tamp_ta1400_amplifier.htm

so no need for a limiter, but I could pay £20 more and get a amp with 1000 more watts (and need a limiter) Which would you go for?!

Go for the higher amp power and a limiter if you must.You should ideally be running your system with an amplifier which can deliver more than the speakers can take thus ensuring you have a clean signal getting to the speakers.

Class D speakers I have no knowledge of but I can tell you that I run a pair of Turbosound mid-hi boxes rated at 150watts rms at 16 ohms a side.This then translates to 300watts rms at 8 ohms.I drive these speakers off a Crown amplifier delivering 650watts rms into 8 ohms without limiters and have done for years without blowing up any drivers.It all depends how careful you are in setting up your system,what components you are using,and how efficient your system is not necessarily about rms as you rightly say!!

[slapthatbass 0]

ive recently bought a pair of peavey 12s ul series,do they have crossovers in them for when i add a bass bin ?and if my peavey 1200 watt amp has 4 ohms per chanel output,can i not only connect the 2 speakers of 4ohms but even add a 8ohms speaker as a monitor ?

 

my gear

 

1 peavey 1200 watt mixer/amp- 600 each side at 4 ohms

2 4 ohms each output

 

what am i allowed to add ?

[McCardle 1]

If your amplifier is only rated at 4 ohms per channel, and you are already running speakers of 4 ohms per channel then thats about your lot. Driving into loads below 4 ohms may seem to work okay initially but can stress the amplifier components and lead to overheating and even failure. If you want to connect additional speakers of either 4 or 8 ohms to the same amplifier as your existing 4 ohm speakers, then you need to invest in a decent quality amplifier which is capable of driving loads down to 2 ohms per channel.

 

If you want to add additional speakers or even a monitor then why not invest in a powered (active) speaker?

[slapthatbass 0]

If your amplifier is only rated at 4 ohms per channel, and you are already running speakers of 4 ohms per channel then thats about your lot. Driving into loads below 4 ohms may seem to work okay initially but can stress the amplifier components and lead to overheating and even failure. If you want to connect additional speakers of either 4 or 8 ohms to the same amplifier as your existing 4 ohm speakers, then you need to invest in a decent quality amplifier which is capable of driving loads down to 2 ohms per channel.

 

If you want to add additional speakers or even a monitor then why not invest in a powered (active) speaker?

cheers for that,....

[Dan allanthemsdisco 0]

why is it that the guide says to use an amp thats 50 watts lower than the power of the speaker. When i joined the forum i found a link on here to an external site with many DJ guides which i printed and read. The one on speakers clearly stated that the best sound will be produced when an anp is higher powered than the speaker, as running an amp at a high volume level will loose quality. ie 8 ohm 300 watt speaker should have a 400watt amp powering it.

[sicktrick 0]

I run a pair of Turbosound mid-hi boxes rated at 150watts rms at 16 ohms a side.This then translates to 300watts rms at 8 ohms

 

 

does that mean that a 300watt 8ohm speaker is able to run at 600watt @ 4ohms?

[DJMickeyk 0]

Hi all,

 

I've been offered a pair of these

 

http://www.jblpro.com/catalog/general/Prod...Id=93&MId=6

 

barely used at a great price, tried em out and they sound good. I know they have been discontinued but really like these. Can anybody recommend a sub to go with them? Will one of these below be sufficient for the pair of speakers? Was actually gonna buy one anyway to go with my passive EV's but would like to have a spare set of speakers just in case, hence thinking of purchasing the above.

 

http://www.jblpro.com/catalog/general/Prod...d=266&MId=3

 

Or will I need a bigger sub than that to go with the powered JBL's? I normally only do small venues but have started to get some weddings in pretty big rooms now so need a bit more power. Im a bit clueless when it comes to sound equipment :wall:

 

 

[aimeehudson 0]

Everyone’s tastes are different. There is no best speaker, only the one that is best for you. When you shop for speakers, listen to several models with familiar music. Take your favorite discs with you when you shop and identify speakers that sound good to you. Your experience in listening to live music is a good gauge to evaluate speakers. The speaker should sound natural to your ears, have balanced tone quality and should be easy to listen to for long periods. Don't feel rushed, listen to a speaker several times before making a final decision.

[Megasong 0]

When thinking about speakers and amplifiers the first thing to do is establish what you want. This may sound silly but many purchases are driven by completely the wrong factors.

 

Typically I hear things like

 

'my mate's got a 1500W amp and and his sounds good so I want at least 1500W.'

'I've heard these great speakers at xxxx they really thump, so I want those'

 

As with most things in life there are no simple answers but there ARE some simple questions and things to remember that will help stop you going completely wrong.

 

Learn to understand at least the basics of specifications, to understand what they actually mean and to recognise when an incomplete spec. is being given, this is often done to make something appear much better than it is. If this is the case walk away, if they need to be evasive or claim not to have the information you can be pretty sure they've tested and didn't like the results otherwise they'd be using them in their sales literature. It does not cost a lost to take a decent set of meaningful measurements relative to the sales benefit of having these figures.

 

And before you think I'm on a sales pitch We do NOT sell equipment, we do however assist a lot of DJs, Bands and others in choosing, setting up and using kit, be it ours on hire or theirs. We try to build relationships with our professional customers, becoming part of their team.

 

So what are your trying to achieve? Volume? Clarity? Coverage? Boosting certain frequency band(s) -Subs for example? Power reductions -outside venues from generators perhaps? Weight reduction? The most common request I get from DJs is more bass, closely followed by a more general request for more volume.

 

1) Amp/speaker power has almost nothing to do with the maximum volume you can achieve without distortion

 

A lot of DJs seem to be going higher and higher powered with their amplifiers chasing a bit of extra volume but to get a just noticeable increase in loudness from a given set of speakers you have to DOUBLE the power of the amplifier. In technical terms a 3dB increase requires the amplifier to push twice the watts through the speakers.

 

Speakers are normally rated by the sound pressure in dB they generate at a distance of 1M with an input power of 1W. You will find ratings typically in the range of 91dB to (at the very top end) 111dB.

 

If you think about it for a second you'll realise that it would take about 120W to get the volume out of the 91dB speakers that you'd get with 1W from the most efficient ones! At the other end of the scale to get the pounding beat at 131dB would take 4096W and less than 128W from the more efficient speakers.

 

When buying speakers therefore one of the most important things (after the sound - of which more elsewhere) is the sensitivity.

 

2) Find out what is the maximum SPL (Sound Pressure Level) your intended speaker will deliver. There should be two figures, peak and sustained. On a good speaker it will also give you a graph of the frequency coverage. If you can't get these figures they are easy to work out from the 1W/M figure in theory, for each doubling of power you get an additional 3dB up to the maximum power of your speakers. In practice however this does not always hold true and you may find that the dB increase is a lot less as you get louder due to mechanical factors in the speaker and cabinet. If they do not give peak and sustained figures be very cautious, ask yourself why?

 

If the manufacturer does not even give a 1W/M figure, walk away or get some new speakers.

 

 

3) Music will almost never deliver an RMS (Root Mean Square) waveform (sine wave) so an amp with a given RMS power will almost never be able to deliver to it's full potential, You will typically find that music will average out to about half to two thirds or RMS. Therefore amplifier becomes the limiting factor, the RMS waveform not giving the headroom needed for music. RMS is a great comparison measure but for music you'll normally need an amp rated at about twice the RMS rating of the speakers to allow some headroom and to get the maximum potential output. This is why many speakers have three figures for power. RMS, Program or Music which is normally double the RMS and peak which is the maximum current you can put through the voice coil before it fuses. This is an instantaneous power and should never be approached.

 

For any given speaker you would typically look for an amplifier that will deliver twice the RMS power of the speaker, or an RMS power equal to the program power, whichever is lower. If your speaker manufacturer does not give this information I suggest you get some new speakers.

 

4) Speaker Frequency Response tells you how high and how low the speaker will respond, but some speaker manufacturers are pretty coy about their figures. Having a frequency response listed without some sort of qualification is one of the ploys they use to try to make a naff speaker look good.

 

3dB is about the smallest difference in sound level you can hear so most reputable speakers refer to the -3dB points. A frequency response of 50Hz to 16000Hz (or 16kHz) is adequate for most applications unless you want serious 'feely' bass. Some speaker makers will however publish a response of (for example) 40Hz to 20kHz. This information on its own may look good but is useless. It only tells you the speaker can reproduce these frequencies, not how loud it is at any frequency. I have tested speakers that claim an excellent frequency response but which are so quiet at the extremes as to be effectively inaudible. They may also have frequencies where they go flat or boom. Useless.

 

If the speaker you are looking at does not give a reference (such as - 3dB) the specification is meaningless except that it tells you the manufacturer is probably scared to tell you and is trying to make their product look a lot better than it is, hence you should avoid it!!

 

Please do not be fooled into thinking that because a speaker can reproduce a wide frequency range at about the same volume it will sound OK. This is something you'll have to listen to the speaker to determine. Things get MUCH more tricky for a speaker when it is trying to reproduce music than when doing a pure single frequency test tone, and even more difficult when being driven hard. ALWAYS test your proposed speakers at the sort of volume and with the sort of music you want them to handle. If you can set them up using a pink noise generator when you're at the venue.

 

5) A 10dB increase in volume roughly equates to a perceived doubling of loudness, it also requires approximately an order of magnitude increase in power. To double the volume with a given pair of speakers you therefore need to multiply the amplifier power by 10. If you haven't fried the speakers you're within sensible limits, if you would have then you need more sensitive or higher powered soeakers or better still a complete re-think.

 

6) Amplifiers are normally rated in Watts RMS (if the figure quoted for an amp does not state RMS be very very cautious as it may be giving a max rating which can be many times greater than the RMS value). RMS stands for root mean square - as if you care - but basically this is the power you'll get if you present it with a pure sine wave, music is not like this, which is why you'll often see RMS, Program and Peak ratings on speakers. You should choose your amp to drive your speakers fully without straining, an RMS rating about 50-100% over your speaker's RMS rating (at the appropriate impedance - in ohms) is more than adequate if it's a decent amp.

 

The RMS figure will typically be given for the amp driving the minimum load it'll handle and for the total across both channels. A 1200W amp will therefore give 600W per channel, or 1200W into one channel when bridged. When you bridge an amp the minimum load it'll handle is doubled so an amp that'll drive 2ohms at 600W/ channel will deliver 1200W into 4ohms when bridged, it'll no longer be capable of driving a 2 ohm load in this configuration.

 

If you double the impedance of the load (the speakers) you'll normally halve the power the amp can deliver, so in our example if you have 8ohm speakers you'll get 150WRMS per channel or 1200WRMS from it when bridged and your speakers are in parallel.

 

Since it needs a higher voltage to drive higher impedance loads in some cases you may find that the differences may not follow as expected, especially with cheaper amps. Always check what power it'll give into the load you are going to put on it.

 

To get a just noticeable difference in the sound level from a speaker you have to double the power you give it. This means that if you have a 150W amp you'll not notice any difference in volume unless your next amp is at least 300W, then 600W, then 1200W etc. As I've discussed elsewhere the best way to get more volume is to get more efficient speakers.

 

The next meaningful piece of information you can find is the peak power the amp can deliver. This is normally dictated by a combination of it's voltage (in the driver circuitry) the current it can deliver and the reserves of power it stores to cope with peaks. You can roughly work out some figures using ohms law. To get 500W into an 8ohm load you need about 63V at 8A RMS, this will also give you a peak power of 1000W. However to peak at 1000W (not an unrealistic need) you'll need just over 11A at 90V peak. If the amp's power supply and output stages can't both deliver this you're going to get nowhere except clipping and probably blowing up your speakers.

 

Sometimes on cheap amps the PSU cannot deliver the voltages and or power required to deliver these peaks, and it sometimes reveals itself if the bridged power is not double the individual channel power.

 

If you want to see examples of cheap amp specs take a look at Gemini or any of the Maplin Prosound range.

 

 

 

There is a whole long screed I could go on to write, about how important speaker placement is, how to use the equaliser, how to set up a sound system and many other factors. If anyone's interested please let me know their issues and what they need help with. I've given a bit of a flavour here to try to help stem some of the misunderstandings that are so common.

 

Caveat emptor or something.

Be happy and choose wisely

 

[McCardle 1]

^ Great Post very informative ^ :Thumbup: