Chappie

It looks like Shure make a preamp that might work - RPM 626 - but they suggest that's only suitable for their Beta mics.

The RPM626 is used for Beta mics because it's a lower sensitivity and can therefore take the higher SPL required for drum mics. The higher sensitivity model for lavs and headworns etc is the RK100PK.

 

Canford also do a range of pre-amps with different connectors link

It's not just you, we have this issue on multiple brands of headworn, including DPA. Interestingly, we have experienced differing levels of noise dependant on cable colour, across the same model of mic. For example, the cable on some of the black mics we have has a slightly different feel to some of the beige, so there must be differences in cable construction out there that reject better than others.

 

I did see a comment from Shure somewhere that the cables on their new TwinPlex mics are double shielded and do not suffer from this issue but, of course, I can't find it now.

Whether it's still produced, after the acquisition of Ciare by Eighteen Sound and then B&C, I couldn't say, but there is the odd link still out there, for example.

It's a Ciare

Another option could be something like this. It might give you enough clearance and make the mic easier to get on and off.

The one I mentioned is a bit thinner than the K&M one and works fine with 55s etc. Ours have 3/8" adapters on the end which make them a bit longer, but if you removed them and just used the American 5/8" threads, it's a bit more compact.

 

Another option could be something like this. It might give you enough clearance and make the mic easier to get on and off.

Maybe have a chat with someone like Radio Structures, who specialise in outdoor antennas and masts. They would be able to make you something custom, if you have any special requirements (bandwidth, cable length etc).

We are looking for the right individual to work as a key part of the sound engineering delivery for live shows at London venues, particularly The Roundhouse, London.

 

If you have excellent communication skills and are a competent sound system engineer (L-Acoustics KARA and K2 strongly preferred) and know SMAART measurement software you would be a strong candidate. If you can also manage the requirements of Front-of-House, Monitors, RF and patch, you would be an excellent match for our requirements.

 

Please get in touch by emailing recruitment@deltalive.com

 

Salary £26-28k

 

Person Spec:

 

• A proven track record of technical delivery of live shows

• Ability to problem solve and work to tight deadlines

• Highly self-motivated, with a flexible and “can do” attitude

• Precise attention to detail

• Diplomacy and sensitivity on-site

Running an 8Ω cabinet on an amp that has a specified (on paper) power rating at 4Ω will be fine (to a point). Forgive the simplicity of this, I hope this explanation is not too simple.

 

Loudspeaker impedance is a measure of resistance that the amp has to drive against. Each amp only has a finite amount of power it can produce; you put in a certain level of signal and it amplifies it by a set amount when pushing against a certain (average) impedance. If you raise the impedance, the amp has to push harder and the amount of power available reduces accordingly. If you lower the impedance, the amp doesn't have to work as hard and the amount of power increases. Obviously, there is a downside to this "free" power and that is the amount of heat created within the amp. An amplifier's ability to cope with lower impedances is basically (amongst other factors) based around its ability to dissipate heat. A well designed amp with big heatsinks and fans can obviously dissipate more heat than the same one with only a small heatsink and thus can generally cope with lower impedances.

 

A rather basic analogy is you pushing a large rock, which you can only push at a certain speed due to the weight. If you double the size of the rock, you can only push it half as fast as previously. If you halve the size of the rock, you can push it twice as quickly, but you will get hot because you are running. If you then start rolling it down a hill, it will run away from you and you collapse from exhaustion.

 

Amplifiers can therefore work across a range of impedances, the minimum of which has been defined by the manufacturer as the safe point below which the amp may cook itself and the maximum is the point where you can't get any useful level out of the speaker. Some amp manufacturers specify ratings at 4Ω, rather than 8Ω, because it produces a bigger number for their spec sheet. Others may spec it because that may be the prevailing standard in a given field.

 

I mentioned at the beginning that it will be fine to a point and this point is how loud you want said speaker. As you said, your 900W @ 4Ω amp is probably good for roughly 450ish @ 8Ω, but it's generally good practice to use an amp that is 1.5 to 2 times as powerful as the rated load you are driving to allow for the dynamics of the musical content (obviously this depends on the type of content running through the amp). If it's not loud enough because there isn't enough power, you may want to keep turning it up, or turn up the volume downstream, to increase the amount of signal going into the amp. At this point the amplifier may start to clip, and the further into clipping you drive it, the more heat is produced (both within the amp and the speaker driver) and the more likely you run the risk of damage. You are far more likely to damage something using an under-powered amp run hard than you are with an over-powered amp running with clear headroom.

 

So, in reference to your original question, yes, the amp will be fine, as long as you don't push it too hard given that it is slightly under-powered for the cabinet you are driving.