Hall speaker cable run length limitations

[gotty]

Following up from my previous questions, we're very close to pinning down the spec for the school hall system, with 2x2x250w (1000w) Behringer B215XL speakers and EPQ2000 amp.

 

However, now that I've started the installation plan I'm concerned about speaker cable lengths as one of the runs will be 22m (the speakers are likely to be 2x2x250w (1000w peak))

 

The Behringer spec gives an upper limit of 15m (but others I've looked at give 10m), and I know that it's a function of the speakers, amplifiers and cables, but I just wondered what experiences others have had (in my pro days, I don't think we ever used much more that 10m runs).

 

One option (but very awkward) is to mount the amps on the stage gantry and this would reduce the long run to 18m, but would then require a long run of audio cable to its input.

[bruce]

As long as you're not using bell wire, it'll be fine. There will be some resistive losses in the cable, but I doubt you'll notice them if using decent cable. Get a drum of 2.5mm cable.

 

 

But a long run of "audio cable" (I presume you mean balanced line-level) will be equally fine.

[smalljoshua]

As long as you specify thick enough cable, it should be fine. I've been recommended 2.5mm as a minimum for most PA situations in the past anyway.

 

Also, I know you didn't ask but would you re-consider the speakers you're choosing? I have had to work with a pair of the B215XL (connected to a EP1500) for the past 3 years in school and I must say that they sound terrible. I'd much rather go for the Studiospares Fortissimo Range with a TSA 2200 to run them.

 

HTH

 

Josh

[gotty]

Thanks for the thoughts on the B215s. I've encountered (but not used them first hand) before and was surprised how good they sounded, although they do seem to be very sensitive to exactly where they're placed.

 

However, this is only one of three amp/speaker combos I have on the shortlist (Peaveys are there too, but I don't have it to hand and can't remember model numbers nor the third contender), and I'll take a look at the Studiospares.

 

 

 

A concurrent post has been automatically merged from this point on.

 

Thanks

 

There will be some resistive losses in the cable

 

I'm more concerned about reactive losses relative to the speaker impedance (which could end up really changing the speaker frequence/impedance characteristics at the amp, depending on the design, which could really mess up the frequency response and be a potential problem with over-driving at higher powers).

 

I'd certainly choose low-inductance 4-core 2.5mm or 2-core 4mm speaker cable.

 

As you say, a long run of balanced/line-level cable shouldn't be a problem (earths willing!)

[Jivemaster]

http://www.terralec.co.uk/cables_and_conne...ble/170_0c.html amongst others will give you several sizes of speaker cable in round and flat styles. Certainly a 1000w speaker system will need 2.5 or 4mm^2 cable.

[paulears]

I'm more concerned about reactive losses relative to the speaker impedance (which could end up really changing the speaker frequency/impedance characteristics at the amp, depending on the design, which could really mess up the frequency response and be a potential problem with over-driving at higher powers).

 

I suspect you have your technical standards somewhat out of balance with the capabilities and performance of the system.

 

The reality is you're planning a budget installation, using popular low end equipment that sonically is a little lacking in detail in the first place. While the physics is correct, I doubt if the actual impact on audio quality will be discernible, once you actually get it running. The practical upshot of the long feeder length will simply be that you have to turn it up a bit louder!

 

Budget amps tend to be built with the capability to withstand abuse - short and open circuits rarely cause them any damage nowadays. If you can get the amps closer, fine - but if not - it's not worth worrying about. I've got about a 20m run to the furthest cabinets in the system in my venue - an extra notch on the right channel is all that's required, and from time to time when necessary I've swapped a 4mm cable for a 2.5mm one and not noticed the difference!

[Brian]

What I do in situations like this is to make each cable run length the same length even if it means hiding some 'spare' cable. That way each channel sounds the same and needs the same drive level. Anyone 'tweaking' the system and setting all the volume controls to be the same will not then mess up the channel balance.

 

In a couple of installation which have need flexible positioning of speakers I've actually run the speaker feeds as a 'ring' with sockets positioned where needed. More cable but you can go down a gauge.

[Stan Hope-Streeter]

However, now that I've started the installation plan I'm concerned about speaker cable lengths as one of the runs will be 22m (the speakers are likely to be 2x2x250w (1000w peak))

The Behringer spec gives an upper limit of 15m (but others I've looked at give 10m), and I know that it's a function of the speakers, amplifiers and cables, but I just wondered what experiences others have had (in my pro days, I don't think we ever used much more that 10m runs).

One option (but very awkward) is to mount the amps on the stage gantry and this would reduce the long run to 18m, but would then require a long run of audio cable to its input.

 

You shouldn't worry about this. We regularly run 20 or 30m of 2.5 or 4 mm2 cable to overhead speakers on trusses for corporate events. This is for high quality speech and music reproduction using the best available kit.

 

Consider the runs required for flown rock'n'roll systems in arenas - they are usually longer than 20m and can be much more than this for delay systems. And don't even think about Earls Court ...

 

Yes, there's no damping factor, and no, nobody notices. Even when the subs have to be 20m away from the racks.

 

You would certainly (I hope) hear the difference in a well-designed studio contol room or an anechoic chamber, but in a normal acoustic space this will be masked by other factors.

[ramdram]

Stan's last sentence says it all really.

 

(Referring to our venue, huge semi-permanent "tent", the punters don't notice any difference in technical sound quality anyway; what they do notice is too loud sound levels ((and crap acts when we have bands appear)). For the most part they are the twilight side of fifty, like me, and they come to listen to an act and not listen to the act's sound gear.

 

Some of our younger volunteers have decent sound qualifications but have been trained on very nice kit indeed and are quite disparaging about the inhouse system...trouble is ONLY they can "hear" the difference, ** laughs out loud **.)

 

So, ref the cables, buy as best you can afford and if you have the budget then 2.5 mm cable will be perfectly acceptable for a "mere" 22mtrs. I buy my LS cable from a music shop in Bodmin for 50p per metre for 2.5mm; so a 100mtr drum, retail, will not break the bank. (Goodness only knows what the wholesale price is...)

 

The cable is about 9mm OD and carries the legend "ELV Professional Installation Cable 2 x 2.5mm2 2007 CE" in yellow print about every 300mm It appears to be some sort of black PVC outer with a white inner sheath covering the two inners, in red and black. Fitting speakons is simplicity itself and the connectors' clamps have no problems with the cable OD.

 

And, as we all sign off...hope that helps.

[gotty]

And, as we all sign off...hope that helps.

 

A belated thanks to all.

 

I'm certainly aware that pro gigs often have very long runs, but with very different kit of course. However, I'm reassured about the runs in terms of signal loss (pretty small) and damping factors etc.

[gotty]

Also, I know you didn't ask but would you re-consider the speakers you're choosing? I have had to work with a pair of the B215XL (connected to a EP1500) for the past 3 years in school and I must say that they sound terrible. I'd much rather go for the Studiospares Fortissimo Range with a TSA 2200 to run them.

 

Josh

 

For a number of other reasons, I'm reconsidering the speakers and will look at the Studiospares Fortissimos as they seem to be very robust.

 

I wondered if you had any thoughts on wall mountings as I'm particularly concerned about safety (and I can't find a weight for them).

[back_ache]

I can't find a weight for them

 

If it helps give you a ballpark figure, the matching "sub" for them is 30kg

 

 

http://www.studiospares.com/pa-speakers/st...le/invt/248230/

[Malcolm Gordon]

I can't find a weight for them

 

If it helps give you a ballpark figure, the matching "sub" for them is 30kg

 

 

http://www.studiospares.com/pa-speakers/st...le/invt/248230/

The Studiospares paper catalogue shows a weight of 30kg for the 15P, but that may be the shipping weight for calculating freight costs, as the 15P SUB is shown as 38kg.