Dance/Huge Gig P.A. Systems Versus Domestic Hi-Fi

[AlexM]

I still think that the most impressive PA I've heard was that used for the Leftfield Aternative Light Source 2015 Tour. I saw them at the Forum in Kentish Town, and the rig there had astonishing output and bass power. Low bass notes actually caused blurring of the vision as your eyeballs rattled in your head. It was also very clean, and generally clean, detailed and quite 'Hi-Fi' considering the bone crushing levels and bass output that could be generated.

Don't know if this is the same system they were touring in for their Alternative Light Source 2015 tour, but in the past (Brixton 2012) they have used a Turbosound Flashline PA, with 10 x Flashline Subs per side, each with 2 x 18" Subs, that's 20 x 18" subs per side and a total of 40 x 18" Subs. As an idea, the Turbosound TSW218 is a horn-loaded Sub cabinet, produce 104Db/1W at one metre. A stack of eight TSW218s gets to 110Db/1W @ 1M (!!). Frequency response is quoted as flat to 36Hz, and power handling per cabinet is 1600W continuous, or 6400W peak. Continuous output per cab is 135Db peak or 145Db Peak (!!)

Some pics of their installations in various venues here

That is some serious bass in your face (and everywhere else) right there

Cheers,
Alex

[ff1d1l]

I've wondered myself.... I would be thinking more along the lines of removing all the pro gubins that's not needed (balanced inputs etc) and replacing the naff op amps in what's left, then some upgrading of the power amps. I doubt time alignment would help as they are naturally time aligned any way by the compression driver diaphragm being in the same plane as that of the woofer coil. They are also designed for wide and controlled dispersion.
A pair of active JBL K2's including amps and crossovers for <2K anyone?

I know this is conventional wisdom. But logically its the bass cone which is the sound source, not its voice coil, and the cone is appreciably forward of the HF diaphragm on the RCFs. My Urei 811's, of which much was made of their time alignment in their time, are apparently giving seven cm worth of delay to the bass driver, which is the distance between the LF cone apex and HF diaphragm. They image rather well, and have very low listener fatigue, and also are reputed to reproduce a square wave reasonably well, in contrast to most multi driver loudspeakers.

The RCF's didn't, to me sound as if they were time aligned, although you're quite right, the lack of depth and focus could well be attributable to the electronics upstream.

With regard to huge PAs, at the year before lasts Green man festival, bass on the main stage PA was overloading so badly I felt the need to point it out to the sound men in the mixing booth. To their bewilderment...they just couldn't hear it. Hmmmm......

[Reffc]

I know this is conventional wisdom. But logically its the bass cone which is the sound source, not its voice coil, and the cone is appreciably forward of the HF diaphragm on the RCFs. My Urei 811's, of which much was made of their time alignment in their time, are apparently giving seven cm worth of delay to the bass driver, which is the distance between the LF cone apex and HF diaphragm. They image rather well, and have very low listener fatigue, and also are reputed to reproduce a square wave reasonably well, in contrast to most multi driver loudspeakers.

The RCF's didn't, to me sound as if they were time aligned, although you're quite right, the lack of depth and focus could well be attributable to the electronics upstream.

With regard to huge PAs, at the year before lasts Green man festival, bass on the main stage PA was overloading so badly I felt the need to point it out to the sound men in the mixing booth. To their bewilderment...they just couldn't hear it. Hmmmm......

Time alignment is a little misunderstood and one needs to consider it in terms of lobing field of the system which is dependant upon wavelengths of a particular frequency arriving at the listening position at the same time for the crossover frequencies. In un-aligned systems, at crossover frequency, there is usually a tilt in the lobing field, and with the convention of tweeter above woofer with no physical or phase corrected time alignment, there will be two lobing fields (the pressure envelope of equal SPL radiated on axis from each drive unit) with the summed field pointing down below the woofer's horizontal lobing field and on-axis signals from each drive unit arriving to the listener out of phase. This causes cancellation amongst other effects, but most speakers, especially at the budget end, have no correction, and that includes many PA type speakers.

The actual point at which the sound source should be measured is at the head of the voicecoil/base of the cone which for most woofers is about where the dust-cap fits onto the cone and for most tweeters will be the base of the dome. However, it does NOT work this way for horn compression drive units where phase shifts take place within the horn throat due to the transfer of the signal from diaphragm to horn passing through air before coupling with the horn. Speed of sound in air is slower than speed of sound transferred into a cone. The only way of accurately achieving time alignment is by measurement at the design stage to work out physical placement or electrical ( active/passive) phase compensation or a combination of both.

Physical time alignment on its own does not achieve the required field lobing compensation as there are phase shifts within the crossover itself so proper time alignment has to include understanding the electrical phase shift. ie in order for it to work passively, L-R type summations in the crossover work best since they sum to plus/minus 180 degrees of phase and result in equal summation at crossover unlike all other filter types.

To complicate matters more, L-R cannot be accurately calculated for any driver combination (forget on line calculators...they don't work in the real world unless they can calculate for each specific drive units electro-acoustic response) but has to be measured.

For such a simple concept, it's actually quite difficult to get right! Active correction with measurement is the easiest way to achieve it these days but if designing passive systems, it becomes an iterative process of design/simulation/measurement/correction whether or not physical time alignment is used.

[Firebottle]

Great post Paul.

[Reffc]

Thanks Alan. I'm sure that someone more eloquent with words than myself can explain it in simpler terms though!

[ff1d1l]

Great post Paul.

+1 great explanation.

I did however mean the cones apex, there's no dustcap on the Ureis which use (selected) Altec 804G drivers. The RCFs have a fairly shallow cone with a large dustcap, physically well forward of the gauze protecting the HF diaphragm. And being used to the Ureis sound, didn't sound in alignment to me. Presumably alignment would be rather easier in an active system though?

[Reffc]

+1 great explanation.

I did however mean the cones apex, there's no dustcap on the Ureis which use (selected) Altec 804G drivers. The RCFs have a fairly shallow cone with a large dustcap, physically well forward of the gauze protecting the HF diaphragm. And being used to the Ureis sound, didn't sound in alignment to me. Presumably alignment would be rather easier in an active system though?

Hi Nial

Time alignment is easier to adjust for in an active system with variable phase adjustment but achieving it still relies on identifying phase relationships at crossover, so measurement is still a requirement. Many active systems using horns use RTA (Real Time Analyser) software for this.

[User211]

I know where your coming from.
When i was in my late teens, i started going to a place near me called the beer Keller,[it was a basement below the high street, solid walls, floors etc] there was a resident DJ there who had a real good ear, and some realy nice equipment, course it was all vinyl, never forgot how good that system sounded, i would always try and get there early before the crowds came in, so that i could have a real good listen to it, 12" singles sounded Fab.
A...

You mean the Bierkeller in All Saints Street close to the Police station? Been there many a time.

I always thought the Lakota's system in the 90/00s (Upper York Street) was pretty phenomenal at pumping out bass at high volume. Thing is the rest of the frequency range was pretty good too. Electronic dance music as a genre is the biz at shaking rooms and hitting your chest - literally making it vibrate. Not many domestic systems can do the later.

Half the reason I use the system I do is to create that sort of effect i.e. get the room moving and shift sizeable volumes of air at high volume. Since I no longer live in Bristol going to clubs just isn't practical anymore.

Then there was Ajax - the blues club with some of the best reggae sounds going. More chest thumping bass using horn loaded speakers and valve amps. Quite a bit of respect for that. Best rendition of Buju Banton's Boom Bye Bye your likely to hear.

For scale, bass output and volume 99% of domestic systems can't even vaguely get close.

[Audio Advent]

With regard to huge PAs, at the year before lasts Green man festival, bass on the main stage PA was overloading so badly I felt the need to point it out to the sound men in the mixing booth. To their bewilderment...they just couldn't hear it. Hmmmm......

Even if they could hear it, they would be taking advice from a member of public... so they "couldn't hear it".

[Audio Advent]

Often I think you get quite a dirty and rough sound dominated by dynamics and loosing out on things like reverb tails, I don't think they do quiet listening too well. And some Mackie 450s and Berhingers as per the photo are quite his

That said, what PA speakers I have heard have been quite good. Some Tannoy PA speakers were good with electronica and gave something I couldn't get at home (perhaps because of volume) but the best I've heard are from Flare Audio which are unusual speakers i themselves - polished aluminium facias and really thin by comarison to normal, especially their 18" drivers in a box about 12" deep yet still able to push out the deep bass without any special DSP. They use some kind of special, vortex air venting which equalises the pressure on both sides of the cone yet at the same time keeping the control of having a box via the air movement "impedance" of that venting .. or something.

But surely the best of both worlds would be some active studio monitors? Many are also designed to deliver dynamics but only to the room (not vast spaces) or nearfield and should be designed to portray all the fine details too. There was some buzz over on another forum for Event Opals a while ago I remember.

Fast dynamics are something which hifi doesn't do often enough at normal listening volumes in my opinion, might be more down to amps and things though.