I am setting up a website which plays recordings of lectures to professionals in the building industry. I have purchased a video camera and a sennheiser wireless microphone EW100. I needed a lapel microphone and bought new one which cost around 20 uk pounds ($30) from ebay. The quality is good but there is still a slight hiss of background noise. I have looked at the next level up in cost and see second hand sennheiser lapel microphones for about 70 uk pounds ($100) and new ones from £150 uk pounds ($220) upwards. I fed the sound into my macbook pro which has the standard soundcard. I am not sure if the sennheiser lapel mic is worth the extra money or how important the soundcard is. I would spend another 200-300 uk pounds ($300-$450) but am not sure if it would make a difference. Can anyone comment? thanks
Since hiss is your issue, I'd venture a bet that you've got a noisy mic preamp in your signal chain. It sounds like you are feeding your audio directly into your MacBook's sound card. That's most likely the source of your problem. Most consumer level sound cards are noisy as hell.
Make sure your wireless receiver is outputting line level audio, if possible, in order to give you the best signal-to-noise ratio.
I would highly recommend purchasing a decent USB or Firewire audio interface (Focusrite makes some good and not-too-expensive models.) That will probably deliver the best jump in quality for your money. You would have to use the XLR cable for your portable receiver, or adapt the 3.5mm to 1/4" TRS in order to plug into the audio interface, but that should be your best bet quality-wise.
If you have access to a decent mixer that sounds clean, you can double-check that your hiss isn't coming from the wireless system by plugging it into the mixer and listening that way, but I would bet that the majority of your noise is coming from your sound card.
i work in theatre as a Sound #3 so I know a fair bit about lapels. But in theatre we position the mics in hair and over ears, which provides good levels, but will not be best for a lectuer. So assuming you're running in a lapel position on a jacket, then gain will be your enemy.
Sennheiser make the MKE which is a really good mic, however the red dot is a brilliant model, which is sadly discontinued. But if you can find one online, go for it. I've only used them as a 3pin lemo model, but retermination shouldn't be a problem if you're good at soldering. And dont worry about buying a pink/beige mic. They can be coloured black very easily if you want them to blend better on clothes. Just don't use a sharpie as they go purple over time. The benefit of the MKE series, if they are supplied with different 'caps' which can be used to attenuate the sound to make up for position. I really think this mic will help alot with hiss, as they are really smooth and cope well under stress.
The DPA 4060 is another great mic, and likewise Im certain a retermination will work if you need them in the mini jack format.
Ask around local theatres. We had a stock of at least 20 microphones which we couldn't use due to them once sweating out, cables being frayed or being painted black when we need beige. Im certain a sound department would happily sell you their used stock. They just cant use them because they are too unreliable for a live theatrical show. But for a lecture, they should be absolutely fine.