speaker impedance query, multi line transformer?

Question

well basically, i recently aquired some bose freespace model 32 loudspeakers.http://pro.bose.com/pdf/pro/tech_data/fs_m32/td_fsmodel32.pdf

they come complete with multi-tap line transformer with adjustable tap settings. my understanding is that this is because they can work with hig power amplifiers which povide output of 100v. it is my understanding that this transformer is a step down, so it will provide a high impedance as to convert the input into a safe voltage for the speaker.

am i right??
my question is this, now if i am to use it with a standard amplifier which is designed to push 8 ohm loads would it be pushin the amplifier too hard?? because it would have much more impedance to get through?? am i in danger of "blowing" my amplifier?? i was thinking just to bypass this transformer and connect the wires straight to the speaker, but fear this may compromise in quality somehow as they sound excellent as they are but i am unsure wether this is safe for my amp.

thanxx

Answer 1

ok, here goes. a 25/70/100 volt speaker output system is designed for warehouses, department stores anything that requires a large amount for speaker to be ran off the same amplifier.



Example:

AMP ---> speaker one ---->speaker two ----> speaker three -----> speaker 4 and so on till you hit the amount of speakers needed. The amp sends out 25/70/100 volts to all the speakers. BUT before the speaker gets it the transformer takes the 25/70/100 volts and converts it down to 4ohm or 8 ohm how ever it's set up. There should be several taps on your such as .5,1.2.5.10 I think.



The best bet for you is to use the two WITH OUT the transformers sense your amp does not provide the 25/70/100 volt output needed to power those transformers. Bypass the transformer shouldn't be that hard. And by looking at the specs your speakers should be running at 4 ohm each again with out the trans.



Hope this helps

Answer 2

Most sound amps are designed to provide a certain amount of power into 8Ω. If you want to mount several 8Ω speakers, say one in each room, you have to be especially careful about wiring them together.



Say you want to put a speaker in each of 4 rooms. Wiring the speakers in series actually adds the impedances for a total of 32Ω. Ideally, the amp wants to see 8Ω, so this would be a very poor transfer of power, meaning a lot of lost energy, just trying to push all those speakers.



If you were to wire all the speakers in parallel, the total impedance seen by the amp would now be 2Ω, or almost a short. What happens to anything else when you short it? Damage.



You could engage in fancy calculations to do a combination series/parallel form of wiring to keep the total impedance as close to 8Ω as possible. But then, if you wanted individual volume controls on the speakers, say to turn down one room while the others continued to play, you'd need expensive L-pads to maintain the impedance.



By taking the amplifier output, converting it to a 70v (or 100v) system, you'd need to use line-matching transformer. Now all the speakers can be wired in parallel. By using another line-matching transformer at the speaker (built-in, in your case), you can select the tap for the amount of power you want each particular speaker to handle.



Let's say you have a 32w amp. You can send all 32w to one speaker, set at the 32w tap, or you can send a16w to each of 2 speakers using the 16w tap, or you could send 8w to each of 4 speakers, using the 8w taps, etc.



It's easier to do the simple arithmetic to add up wattages than the more complex calculations for impedance matching. Also, you can use simple dimmer controls to control the volume on individual speakers.



If you're running stereo, you just need to duplicate it for the other output. But you do need a matching transformer for your amp output, if one is not already built in, to utilize this system.

Answer 3

Bose Freespace 32

Answer 4

According to the literature, the nominal impedance in the 32W configuration is 4 ohms. Go with that setting and your amplifier will be fine.