Induction Loops

[TallPaul]

Has anyone ever encountered problems using guitars within induction loop systems. We seem to be very prone to feedback when using guitars running through a DI, and those connected to an amp. When the loop system is disabled, the problem vanishes. I think the guitar pickup is acting in the same way as the coil inside a hearing aid, and feeding the induction loop signal back through the amp/PA. The loop system is not currently fed from the desk, so presumably giving it its own aux output minus guitar could be a solution. Just wondered if anyone has had this problem before? I found some information here:

 

See Point 2

[Fleeting]

Hi,

Yes it is a problem with guitar coils picking up the induction loop signal. There is no real way of curing it other than turning the loop off. If there is amplified guitar on stage, then there is usually a big enough sound sytem making the loop redundant. How this fits in with the new Disability Discrimination Act I don't know?

If you have the Sennheiser Infra-red system installed then this gets round the problem albeit a little more expensive than the traditional loop system.

 

Fleeting

[TallPaul]

Yeah, I don't think we can turn the loop off (Disability Discrimination Act). Infra-red sounds like a good bet, but it's probably quite pricey. Anyone know how much it might cost for a small (350 seater) venue?

[Pete McCrea]

No way that you could feed the loop from an Aux as you mentioned? or a matrix feed? Or route the mix through a Stereo group, taking a feed for the Loop, and putting the Guitar straight into the main mix?

[Brian]

We've overcome this in the past by re-routing the loop when we have a band in. We added some small boxes containing jack sockets which we could plug in an extra loop section which we could then put outside the band pit putting the guitar outside the loop.

 

Something we keep meaning to try is to put a feedback destroyer onto the loop feed.

[misterbassman]

I have also had this problem in the past, however I found it only effected guitars with single coil pickups, those with humbuckers seemed to be effected very little if at all.

 

Dan

[TallPaul]

It's definately the case that some guitars are absolutely fine, then we suddenly seem to have a problem with others. It's not going to be that easy to split the loop up, so I think we'll maybe go down the route of trying to provide a seperate mix for the loop in some way.

[Brian]

Anyone know how much it might cost for a small (350 seater) venue?

Budget at least £1500 for the 'transmitter' and installation and then £100 for each receiver. You can spend lot more.

 

Yeah, I don't think we can turn the loop off (Disability Discrimination Act).

This is a very interesting question. The DDA has a test of 'reasonableness' in it. If something costs too much to do then you are not obliged to do it. But the act does not say what is reasonable, that will be left to the courts.

 

those with humbuckers seemed to be effected very little if at all.

True, the humbucker coil is doing exactly what it should - rejecting external magnetic fields.

 

taking a feed for the Loop, and putting the Guitar straight into the main mix?

Probably won't work. Remember you have at least 2 possible feedback paths.

 

1. guitar pickup -> mixer -> loop amp -> loop -> guitar pickup. This one you can cure BUT it isn't really a problem, most people with impaired hearing can hear a band just fine, the guitar doesn't need to be in the loop. They need assistance for speech.

 

2. guitar pickup -> guitar amp -> open mics -> mixer -> loop amp -> loop -> guitar pickup.

 

If you've got open mics on stage to pick up the dialogue so people with impaired hearing can still hear then you're stuck.

 

The problem is not helped by most loop amps having fairly heavy compression on the signal which tends to make feedback more likely.

 

Another problem is people being sold loop amps when they are not suitable. IMHO a loop amp should not be fitted into a performance venue or if it is, to a restricted part of the space only.

[Conscript]

This problem seems to be very guitar specific. Might be something to do with the pick-up being used.

 

Another loop feadback route is if there is a spring-line reverb unit being used. Most reverbs are now digital these days, but spring lines were used to create reverb before digital delays became cost effective, so check any backline stuff out too.

[PeterT]

I could be wrong, and I'm not sure if it's still applicable but I remember that grants were available for things like upgrading induction loop systems to more fully comply with the DDA. It might be worth checking with your local authority to see if it's still the case.

[paulears]

I'd never come accross this problem, but just tried it out this afternoon. with a strat all three pickups received the loop audio as soon as it got close to the loop area. I tried another guitar with humbucker and single coil pickups. humbucker fine (as reported in another post) the single coils with one polarity reversed reduced the level to nearly, but not quite gone. The line 6 guitar with onboard electronics seemed imune.

[Bob in Derby]

Grants should definitely still be applicable. We recently upgraded our old 2 channel sennheiser IR system with more radiators, and a 6 channel unit... and the DDA grant helped out very nicely! We've been doing some audio described performances as well as just "programme" feeds, giving users choice of channels - description, desk feed, ambient mic feed.

 

Huge improvement for us, and users, who can now use "stethosets", standard headphones, "T" switch induction loops or for regular patrons, bring their own fave headphones to plug in!

 

Not got specifics about contacts for grants as it was dealt with by one of the many "papery" parts of the council - we just ordered and installed the kit :unsure:

 

I've also had problems with various guitars and flourescent fittings, pub (beer pump) electrics and all sorts. My precision lyte bass has had copper foil screening put inside the electronics housing, but I still get occasional problems and have to angle myself in a certain direction (someting to do with ley lines I imagine ) but that's another story!

[andy_s]

slightly off topic, but related - when I worked in Taunton we used to have to apologise profusely when we had shows with guitars / keyboards in, as we had to turn off the deaf loop. with keyboards, it was related to volume pedals, with guitars (as above) with single coil pickups. Another problem very difficult to solve was that when long mic / signal cables had to be used, we would inadvertantly set up an arial which would pick up Radio Bristol and broadcast it over the PA. - this was not often a problem with bands, but for theatre shows with live sound, where you couldn't use the sound engineers technique of "shortest distance between 2 points", but had to route cables round the back and up and down bits of scenery as necessary.

 

many phone calls with Radio Bristol later, the only solution we could come up with was to lengthen or shorten the cable length, so as to not coincide with the wavelength. Apparently the radar room at RNAS Yeovilton (supposedly completely interference-proof) suffered from the same problem, so we didn't think there was much point in fussing with tinfoil screens and the like....