Need a new PA System

[Light]

Hi Blue-Room,

 

I was doing a small mobile disco the other night when it's come to realisation that the size of venue I do is just too big for the current speakers I have. I currently run my mixer directly into my Prosound 800 Watt Amplifier, going out to 2 x 300 Watt speakers. It just really isn't doing anything anymore and the audio quality is awful.

 

So, I want to change it all. I'm a guy who is into lights more than sound (I've been upgrading lights all the time, seem to have forgot the PA) so I'm totally confused. I've been reading about crossovers, 1 or 2 subwoofers and I'm totally lost. I think what I need is 2 Tops(?) and either 1 or 2 Subwoofers hooked up to a crossover. I don't mind if my speakers/subwoofer is Passive or Active.

 

Can anyone give me a good idea of what I need to get and how to set it up efficiently.

 

Thank you!

[sam.spoons]

Without a budget it's hard to give solid advice but as a starting point consider the following

 

Budget rig

Alto Truesonic TS112A x 2

Alto Truesonic TSsub15 x 1

These are fantastic value for money (around £750 for the above rig) and sound very good (all be it not quite as loud as more expensive kit) total 1400 watts RMS 2000 watts 'dynamic'.

 

Mid price rig

Yamaha DXR12 x 2

Yamaha DXS 15 x 1

A significant step up in volume, build quality and sound quality at around £1700. total 2000 watts continuous (RMS? Yamaha don't say) 3150 'dynamic (Alto may have stolen a word from Yamaha herehttp://www.blue-room.org.uk/public/style_emoticons/default/rolleyes.gif)

 

I'd definitely go for actives (as above) for most bang for the buck and no crossover needed for the above as the subs have one built in. Compared to your present rig either of the above would be a revelation.

 

This is just my opinion, you must go and listen for yourself at a dealer who can do a side by side comparison at gig levels.

 

For the record I do live band gigs (both as a sound engineer and performer, covering both rock and acoustic acts) and, after listening to 10 or 12 active speakers with 12" bass drivers, I bought two QSC K12s (@ £750 each) for FOH in July (I use them with a single EV SbA750 sub which I've had for a while), and for monitors I bought 2 x Yamaha DXR10s and one Alto TS110A (probably with another one or two to follow).

 

HTH

[TonyMitchell]

I currently run my mixer directly into my Prosound 800 Watt Amplifier, going out to 2 x 300 Watt speakers. It just really isn't doing anything anymore and the audio quality is awful.

 

The amplifier is underpowered for your speakers. The amplifier you refer to is rated 150w per channel at 8 ohms, 300w per channel at 4 ohms. As a rule of thumb, when matching an amplifier to speakers, the amplifier should be rated 1.5 to 2.0 times the rms rating of the speakers. If your speakers are 8 ohms, the amplifier is severely underpowered, if they are 4 ohms, the amplifier is still too small.

 

I've been reading about crossovers, 1 or 2 subwoofers and I'm totally lost. I think what I need is 2 Tops(?) and either 1 or 2 Subwoofers hooked up to a crossover. I don't mind if my speakers/subwoofer is Passive or Active.

 

Whereas typically you would always want two tops, to place L & R (as mid/high frequencies are directional), low frequencies handled by subs are omni-directional, so in a small system, deploying a single sub for a little low frequency extension generally works.

 

The components of a small active system would include two top loudspeakers, one or two subs, a 2-way active crossover and either two 2-channel amplifiers or one 4-channel amplifier. The active crossover separates the low frequencies that go to the amplifier driving the sub/s and the mid/high frequencies that go to the amplifier driving the tops.

 

For the application you've described, I'm guessing portability is of the essence and it is likely the vehicle you use will influence the size of the equipment you can take out. Truth is, for small discos, you may not need an active system, unless you are regularly playing lots of bass heavy modern dance music. For family parties, etc, many mobile DJs use a pair of good, passive speakers, with either a 12" or 15" LF driver and a compression driver. A speaker with a 15" LF driver will play lower frequencies than a 12" LF driver, however the comparable 12" cabinet will often play just as loud and be much smaller and lighter. A good example of this at entry level, being the JBL JRX112 and JRX115.

 

Another option is to consider powered speakers. Although generally heavier than their non-powered counterparts, the amplifier modules being onboard, mean you do not need to carry separate amplifier/s, you simply run a power feed and a line level signal to each powered cabinet.

 

The best thing is to listen to a few different options, but also get to grips with the cabinet - make sure you like the handles and can comfortably lift them on and off stands at a useable height.

 

A couple of other pointers - forget about watts - you can't hear watts. I have a 2,000w heater under my desk, but it doesn't actually make much noise and even with it on full, I can still hear clients on the phone and colleagues talking in the office next door to mine.

 

When comparing speakers, look at the "sensitivity" rating, measured 1w/1m (one watt at one metre) - look for a higher number rather than a lower number. When researching product, you'll encounter lots of people, particularly sales staff in disco shops, quoting big wattage numbers as though they are the ultimate unit of measurement of one's manhood! However, one 200W loudspeaker may be significantly louder than another 600w loudspeaker. How loud a particular loudspeaker will play, is largely dependent on its efficiency, rather than how many watts of power it can accept. A simple analogy is a 2.2L car capable of 0-60 in 5 seconds and 40mpg is in every way superior to a 3.8L car capable of the same 0-60 time but only 20mpg.

 

Finally, whatever you buy, always invest in padded bags to protect your speakers - otherwise the grilles and cabinets will start to look tatty after only a few gigs.

[bakerboy]

On a portability area and if it party stuff then two LD DAve 15 would be perfect as the bass is brilliant and then tops are in good balance with Bass

 

:)

 

 

 

[Light]

Budget rig

Alto Truesonic TS112A x 2

Alto Truesonic TSsub15 x 1

These are fantastic value for money (around £750 for the above rig) and sound very good (all be it not quite as loud as more expensive kit) total 1400 watts RMS 2000 watts 'dynamic'.

 

This looks like the kinda thing I need. Do you have any more examples that I could take a look at? And as for cabling, I assume that I would run 2 direct XLR outputs from my Mixer (L & R) into the Sub, and then run another 2 XLRs into the Left and then the other into the right speaker? As you can tell, I haven't done this before..!

 

When comparing speakers, look at the "sensitivity" rating, measured 1w/1m (one watt at one metre) - look for a higher number rather than a lower number. When researching product, you'll encounter lots of people, particularly sales staff in disco shops, quoting big wattage numbers as though they are the ultimate unit of measurement of one's manhood!

 

Thanks for this little tip off, I didn't know about this at all and it'll definitely effect my end purchase. Thank you for your efforts!

[sam.spoons]

Budget rig

Alto Truesonic TS112A x 2

Alto Truesonic TSsub15 x 1

These are fantastic value for money (around £750 for the above rig) and sound very good (all be it not quite as loud as more expensive kit) total 1400 watts RMS 2000 watts 'dynamic'.

 

This looks like the kinda thing I need. Do you have any more examples that I could take a look at? And as for cabling, I assume that I would run 2 direct XLR outputs from my Mixer (L & R) into the Sub, and then run another 2 XLRs into the Left and then the other into the right speaker? As you can tell, I haven't done this before..!

 

When comparing speakers, look at the "sensitivity" rating, measured 1w/1m (one watt at one metre) - look for a higher number rather than a lower number. When researching product, you'll encounter lots of people, particularly sales staff in disco shops, quoting big wattage numbers as though they are the ultimate unit of measurement of one's manhood!

 

Thanks for this little tip off, I didn't know about this at all and it'll definitely effect my end purchase. Thank you for your efforts!

 

I don't know of anything which does the job as well as the Altos for the price (or comes close TBH). Re cabling, you are right on the money there.

 

The sensitivity in dB @ 1watt/metre applies to passive cabs and is not usually quoted for actives. They are usually quoted as a calculated max output (which is calculated from the dB@1watt/metre and the amplifier power) which may or may not be realistic in real world situations (e.g. my QSC K12's have 2 x 500 watt amps, one for the bass driver and one for the tweeter. The tweeter can't possible need the same power as the bass driver, tweeters are usually rated at around 10% of the bass driver power capacity so to use 1000 watts to calculate the max output is suspect. However, they are bl00dy loud so maybe I'm wrong).

[TonyMitchell]

In active cabs, the manufacturer usually quotes the sensitivity for each active section, as well as the power handling of each section.

 

Take the Martin Audio H3+, a popular 3-way box, with two active sections (LF & MF+HF) and two passive sections (MF+HF)

http://www.martin-audio.com/products/h3+.asp

 

With any type of loudspeaker, calculated maximum SPLs are meaningless, as there are several fundamental flaws:

- they are usually based on the peak power handling of a transducer, sustainable for less than a second,

- they assume no thermal compression (in simple terms, watts being transferred into heat and not sound)

- they do not indicate the frequency range applicable to this theoretical SPL

 

This is why it is so important to look at sensitivity data rather than "maximum SPL" Whilst this won't tell you if the speaker will sound nice, there are less variables to be exagerrated by the Marketing Dept. in their attempt to sell product!

Over the past decade, as amplifier power has become cheaper and huge output capacities packed into 1U and 2U cases, some loudspeaker manufacturers haven't IMO made much effort to increase the efficiency of drivers.

[sam.spoons]

In active cabs, the manufacturer usually quotes the sensitivity for each active section, as well as the power handling of each section.

 

Take the Martin Audio H3+, a popular 3-way box, with two active sections (LF & MF+HF) and two passive sections (MF+HF)

http://www.martin-au...roducts/h3+.asp

 

With any type of loudspeaker, calculated maximum SPLs are meaningless, as there are several fundamental flaws:

- they are usually based on the peak power handling of a transducer, sustainable for less than a second,

- they assume no thermal compression (in simple terms, watts being transferred into heat and not sound)

- they do not indicate the frequency range applicable to this theoretical SPL

 

This is why it is so important to look at sensitivity data rather than "maximum SPL" Whilst this won't tell you if the speaker will sound nice, there are less variables to be exagerrated by the Marketing Dept. in their attempt to sell product!

Over the past decade, as amplifier power has become cheaper and huge output capacities packed into 1U and 2U cases, some loudspeaker manufacturers haven't IMO made much effort to increase the efficiency of drivers.

 

+1 to all above, as I said "which may or may not be realistic in real world situations" but most manufacturers don't quote 1 watt sensitivity figures for active cabs so the only figure you have to go on is the max output. One just has to hope that all the manufacturers use the same mathematical tricks and dodges to make their boxes appear louder than everybody else's thus giving us a flawed but rudimentary means of comparison http://www.blue-room.org.uk/public/style_emoticons/default/mad.gif

 

 

[TonyMitchell]

... but most manufacturers don't quote 1 watt sensitivity figures for active cabs so the only figure you have to go on is the max output.

 

Sorry, but that's not the case. Most manufacturers quote sensitivity for each active element, as per the MA example I quoted, as do the likes of Turbosound, JBL Professional, Void Acoustics, etc...

 

One just has to hope that all the manufacturers use the same mathematical tricks and dodges to make their boxes appear louder than everybody else's thus giving us a flawed but rudimentary means of comparison.

It's not that simple. The manufacturer that has a big stake in car audio is, IMO, the worst offender when it comes to quoting apsirational maximum SPLs. The fact their drivers are relatively inefficient, but have a high rms handling and quoted peak is 4*rms, makes the magic SPL number more ridiculous than some other brands, where power handling is lower and peak is say 2*rms.

[sam.spoons]

... but most manufacturers don't quote 1 watt sensitivity figures for active cabs so the only figure you have to go on is the max output.

 

Sorry, but that's not the case. Most manufacturers quote sensitivity for each active element, as per the MA example I quoted, as do the likes of Turbosound, JBL Professional, Void Acoustics, etc...

 

One just has to hope that all the manufacturers use the same mathematical tricks and dodges to make their boxes appear louder than everybody else's thus giving us a flawed but rudimentary means of comparison.

It's not that simple. The manufacturer that has a big stake in car audio is, IMO, the worst offender when it comes to quoting apsirational maximum SPLs. The fact their drivers are relatively inefficient, but have a high rms handling and quoted peak is 4*rms, makes the magic SPL number more ridiculous than some other brands, where power handling is lower and peak is say 2*rms.

 

I'm away from my broadband connection for a couple of days so protracted searching for info isn't possible but at the level of gear we are discussing here, JBL Pro (PRX), QSC (K series) and Yamaha (DXR), they don't quote sensitivity figures for drivers in their user manuals (or, IIRC their marketing bumf) nor do they explain in any detail how they arrive at their max output figures (other than to state that they are calculated from driver sensitivity and amplifier power). It may be possible to find the numbers if one delves deep enough into the support docs and for Turbosound, Void, Nexo, JBL,s proper professional kit (as opposed to the semi-pro+ PRXs) etc I'll assume you are correct. For the sensitivity figures to be useful you'd also need to know the individual drivers power handling as well as the power amps RMS output into the relevant driver impedances (all of which I guess is available from the 'proper pro' makers). Also, as you said earlier, non of this tells you what the speakers actually sound like http://www.blue-room.org.uk/public/style_emoticons/default/rolleyes.gif.

 

As you say, car an domestic audio makers are utterly ridiculous in this area with PMPO (peak music power output) being the biggest load of tosh imaginable. I'd hope (being, probably, a bit too trusting) that the professional PA manufacturers would quote some numbers that bear at least some relationship to reality. When it all comes down to it you must let your ears be the final judge.

 

 

 

[Brian]

Sensitivity figures are, on the whole, meaningless as very very few manufacturers quote their power compression figures.

[john deans]

PMPO= Purely Mythical Power Output

[Shez]

Sensitivity figures are, on the whole, meaningless as very very few manufacturers quote their power compression figures.

What sort of range of values would you expect to see for power compression? I know how widely the sensitivity can vary but I've never investigated the specifics of power compression. What would be a poor, average and good figure?

[Simon Lewis]

Between three and seven dB is what JBL cite. They have quite a useful info-marketing document here...

[TonyMitchell]

Between three and seven dB is what JBL cite. They have quite a useful info-marketing document here...

 

& for an example of how meaningless the max SPL is, take their STX828S (the replacement for their very well known twin 18" SRX728 sub) http://www.jblpro.com/catalog/General/Product.aspx?PId=444&MId=3

The sensitivity is 99dB 1w/1m, the continuous power handling is 2,000w, "program" is 4,000w and "peak" is 8,000w

The "rated maximum SPL" is "138dB peak", calculated from the 99db/1w base figure, assuming zero thermal compression and based on 8,000w amplifier power (for however many ms this is sustainable).

 

Thermal compression will be at the higher end of the scale for the higher power that a transducer can handle.

So, the "real" SPL for this particular cabinet is probably somewhere closer to 126dB, a considerable 12dB less than the Marketing Department's dream number.