speaker terminology

[i_amadeo]

hi all i am going to spend about ...well lets say alot.... on speakers and i realy would love to understand what makes my future speakers shine from the rest so i have been researching and studying the speaker specifications .....only to find out how hopless my case was ...i barely understood any thing on the paper
i would realy like to know what is

sensitivity ......and is ....(2.83v/1m): 90 db ....good?

frequency responce ....and my speakers state a 38 hz -30 khz what does that meen( and also ....on axis and off axis )

crossover frequency ....again 400hz /3khz

low frequncy extension ?

if its not so much trouble ...thanks

[Stoney]

Here are some basic definitions.
2.83v/1m 90db: is how loud (sound pressure level=spl) the speakers are, measured at 1 meter with 2.83v input. This measurement is usefull to determine how much amplifier power you will need to produce a certain listening level. Compare with other speakers you may know or be demonstrating.

On Axis would be directly in front of the speaker. Off axis measurements, eiither horizontally or vertically would indicate how far from offcenter (right to left or up and down) you could move without effecting what you hear.

Frequency Response; Humans are theoretically capable of hearing frequencies from 20 to 20,000 Cycles Per Second (Hz). A perfect speaker would be able to reproduce all frequencies in the audible range at the same volume with no distortion. It is also desireable to have frequencies in the sub audio range (very low frequencies 10-20 Hz) for movie sound effects and bass sounds.

Crossover Frequencies; These are the points that the speaker will divide the frequencies to the separate drivers. In your example, below 400 Hz go to the Low frequency speakers (woofer), from 400-3,000 Hz go to the mid range, above 3,000 Hz go to the High frequency speakers (tweeter).

Low frequency extension: not sure what is meant. Would probably need to see it in context.

Specifications give you general guidelines for comparing speakers on paper. Most important is that you actually listen to them and compare what you hear. It would be best to have them in the actual environment you will be using them in (room acoustics can play a big part in how they will sound) and drive them with the equipment you will be using.

Hope this is helpfull. If any one can explain further, please do so.

some links (please note that these are simply some info pages I found. I do not particularly endorse any of the products that may be sold on these sights)

http://www.bwspeakers.com/index.cfm/fuseaction/local.faq/ObjectID/F5CA2ECD-3D20-11D4-A67F00D0B7473B37

http://www.sabre-international.com/a-simple-guide-to-loudspeaker-technology.html

http://www.thespeakerstore.com/glossary/tech.htm

http://dju.prodj.com/courses/soundreinforcement/c5.shtml

[i_amadeo]

thanks man for your help my next question is if i want to biamp my speakers i only have one rotel power amplifier how can i do that ,,,,there are 4 speaker reds and balack on each speaker and only 2 on the amp

[Shane Martin]

my next question is if i want to biamp my speakers i only have one rotel power amplifier how can i do that ,,,,there are 4 speaker reds and balack on each speaker and only 2 on the amp

First you'll need to remove the gold jumpers off the binding posts, then you will connect a set of wires to each post from your amps(2 from each). To connect the amp to your preamp/recever/processor you'll have to use a y-adapter to split the signal from the pre to your amps.

sensitivity ......and is ....(2.83v/1m): 90 db ....good?

To answer your question: This is about average. This is really borderline going into lower efficiency. As a rule to add 3 db you need to double your amp power so to produce 93db at 1 watt you'll need 2 watts instead of 1 meanwhile a speaker like Klipsch only needs 1 to produce 93db.