mika wrote:
Hm i still have not found a omnispeaker like in your link 
Is there no onlinestore where i can buy one. And which is a usual model of omnispekers???
On the very site I linked this document from you can find world-wide distributors of that brand.
This are the European ones including Germany (from that site).
http://svantek.com/distributors-europe.html
What have you done already to find them?
I told major acoustic measurement equipment brands/suppliers have them or can direct you.
Which ones have you called already?
This is no typical on-line shop stuff.
If this is for pro work you should know such brands/suppliers.
If not, you can as well use any speaker with a relative flat curve within the range from "as low as possible" to ca 5000 Hz. This doesn't need to be a top class speaker. A cheap model will do.
The specs are a compromize between: as small as possible, robust construction, as low frequent as possible, above 5000 Hz doesn't or hardly matters and relative flat in that range, a high efficiency to get high levels, and as cheap as possible.
And it can have an advantage to have the vent on the front side (hence types easy usable for flush mounting).
There is no usual model, as little as there is usual measurement equipment or usual home or studio speakers.
Most of these pro things look like the one in that pdf I linked for which you could find the supplier on the very same site.
And yes, since made for a limited pro-world these omnis aren't cheap and meant for rough 'in the field' work (very strong and robust build).
They mostly come with a heavy amplifier (to 1000 W) and an equalizer, but I think you can buy them separately as well.
In reverb room labs they don't necessarily use such speakers but use the corners with more traditional high power speakers (sometimes custom made, what they need is a lot of noise, and measurements are relative not absolute).
BTW you also can use an alarm or starters pistol (is cheap and if using a 9 mm alarm revolver it has a lot of acoustic power. I have them in several types).
The disadvantage: if averaging lots of measurements it smells (the burned blank bullet powder) and you need to vent the room afterwards.
Good reverb measurements rarely depend on having the right (whatever that is) speaker, but on a lot of averaging and positioning of speaker and mic in function of correct excitation and interference patterns.
