Hearing aid

[Rajchumberis]

Anyone have any information on loop systems?! So far we're using a wired system that affects our semi acoustic instruments like bass guitars and electric guitars. It's their pickups. The more we put in the loop mix, the more thefeedback from these instruments. Are there any other solutions?! Thanks.

[david.elsbury]

Have you searched the forums? We've covered loop (and other such systems) before.

[revbobuk]

but broadly speaking, yes. Single coil pickups could have been designed as loop receivers. You can:

 

1. Make sure the instruments are outside the loop. Simple single-turn loops have a lot of spill, so that's hard. Laying out the loop with a second, reversed direction loop at the front edge can give better cancellation at the front - check out the Ampetronic website for details. But if you're stuck with the layout, then

 

2. Make sure there is none of the feed from the offending instruments in the loop mix. Use an ambient mic instead of feeding instruments into the loop mix.

 

3. Try to use humbucking pickups for the instruments.

 

4. Keep the loop drive at the right level - often nobody has ever measured the system. Canford will supply a comprehensive test set (I've got one) to check levels of drive, to make sure your loop signal is set right.

[cedd]

Got to say, I've never put an instrument into the loop mix in my life. I always try and keep it a "clean" mix of just vocals (spoken word, but occasionally singers). At least 2 local venues I know of just have an ambient mic over the stage with no way of injecting your own mix. I'd certainly be looking to cut back what the loop gets in its mix.

 

I'm no audiologist, but I can't imagine a hearing aid coping that well with a bass guitar. My dad is a hearing aid wearer and also conductor of 2 brass bands. He had to go very expensive before he got a pair that'd cope. Granted that's using their own mics, in the incredibly high SPL in the middle of the band (why do you think he's wearing them?) but I'm sure one consideration was frequency response.

 

Of course an ambient mic will still allow a feedback loop to exist, but probably less likely than a direct feed.

[revbobuk]

Instruments in the loop mix aren't the only way to get feedback - say you have a vocal mic for a singer who is also playing guitar, using their own amp. The guitar picks up the loop, including vocals. That comes out the instrument's amp, which may then get picked up by the vocal mic, especially it is behind the performer. Moving the instrument amp can sometimes help in those situations.

[Rajchumberis]

The only inputs that are in the loop mix are the lead singer's voice, his piano (just a little bit), and the RF mic's which are used for the preach. the loop cable actually was install a lonnnng time ago and actually goes around the stage. (the stage is inside the 'loop'). If I turn up the hearing aid, on the hearing aid amp I find that it can spill in to and oddly only enough in my right hand side speakers. bizzare? You'd think it'd affect them all. So any other considerations? I'll look in to that canford hearing aid test that you've mentioned to see if that can help me.

 

Thank though!

[revbobuk]

If the stage is inside the loop, it's time to re-route the loop cable. The device I use to test and calibrate loops is the Ampetronic FSM which you can get from Canford, direct from Ampetronic, or you could get a proper survey done by someone with the equipment and the expertise!

[Simon Lewis]

If the stage is inside the loop, it's time to re-route the loop cable. The device I use to test and calibrate loops is the Ampetronic FSM which you can get from Canford, direct from Ampetronic, or you could get a proper survey done by someone with the equipment and the expertise!

 

Raj,

 

Since I've seen your system, perhaps I could make a few general points? The three main group assisted listening systems all have their pros and cons:

 

FM radio can be very effective, but requires users to have receivers (one for each user and this needs charging, aintaining etc.), and we are often struggling for radio spectrum, so having a channel tied up with an ALS isn't always the best approach (although some systems work outside of the radio mic spectrum).

 

Infra Red has good fidelity and the ability to transmit more than one channel. It does tend to need line of sight view of the transmitter (which can be a real problem), and it can be harder to get the required coverage in the "three sided balcony / congregational chapel" type building you have. Also, you need to wear a receiver (with the attendant maintenance and management issues), and the cost of the system for medium to large spaces can be up to a factor of ten higher than that reqiured for a loop.

 

Loop systems can work very well, only require the user to have a telecoil fitted to their aid (so no special receiver is needed), and it tends to work in all directions (in the horizontal plane). Frequency response is deliberaltely retsricted. but if you need to use a loop, excellent frequency response is somewhat academic anyway! I believe that it is worth getting a workable loop in your church, as it represents the best solution for those with hearing loss.

 

From memory, you have a small voltage driven unit that perhaps isn't the best for your application. As you are considering some upgrades, I'd suggest you add the loop to this, and get a better quality loop amp with current limiting and compression perhaps in conjunction with a properly designed cancellation loop to minimise the magnetic signal on stage. This isn't quite a DIY project, and unfortunately, having a £240 meter doesn't buy you the expertise to interpret the results and know how to design a workable system ;-)

 

Simon