speaker/crossover/ohms

[garage inc.]

Two 4 way speaker enclosures i built from scratch each containing a 8 ohm tweeter with a 8 ohm passive 2nd order xover, a 8 ohm midrange speaker with a 8 ohm passive 2nd order xover, a 4 ohm mid bass speaker with a 4 ohm passive 2nd order xover all connected to receivers L&R speaker outputs on speaker A switch, receiver is 4 ohm stable on speaker switch A & 8-16 ohms stable on A+B switch. The crossovers & speakers/tweeters are wired in typical parallel configuration and one 4 ohm subwoofer in each enclosure powered separately by a 1000 watt plate amp connected to receivers low output to amps input, plate amp has its own adjustable rotary crossover. Question: Does this work without any conflicts such as the mid bass speakers being 4 ohm or subwoofers being 4 ohm connected via receivers/plate amps low inputs/outputs with the other speakers connected to receivers speaker outputs, thanks for any input or is it output, thanks again.

 

[patate91]

Since the subwoofer has it's own power amp I don't see why you coule have any issue. Maybe I just don't understand your question.

 

[toxcrusadr]

Should not be an problems here, with a few assumptions. Patate is correct that if the sub has its own amp, the impedance of the sub driver is not an issue with respect to the main amp.

The aforementioned assumptions include "the overall impedance curve of the speaker is reasonable and doesn't dip below 4 ohms for any appreciable part of the spectrum." Assuming this is a reasonably well engineered speaker, with a 4 ohm capable amp, there's no problem.

 

[garage inc.]

Should not be an problems here, with a few assumptions. Patate is correct that if the sub has its own amp, the impedance of the sub driver is not an issue with respect to the main amp.

The aforementioned assumptions include "the overall impedance curve of the speaker is reasonable and doesn't dip below 4 ohms for any appreciable part of the spectrum." Assuming this is a reasonably well engineered speaker, with a 4 ohm capable amp, there's no problem.

Thanks, I wasn't sure about the 4 ohm mid bass speaker/crossover being a problem. Through studying passive crossovers I have learned they work independently to each & don't halve speaker ohms like paralleling just speakers & I thought the 4 ohm subwoofers would cause a ohms problem but I can see that the plate amp see's the 4 ohms not the receiver. Thanks a lot I didn't want to fire her up with the money I have in it that I don't really have & watch it all go up in smoke, lol thanks again.

 

[WaynerN]

It's not the impedance of each individual speaker or X-over network, its the impedance of the entire speaker system that is the concern. It's probably rated at 8 ohms, maybe 6.

 

[garage inc.]

It's not the impedance of each individual speaker or X-over network, its the impedance of the entire speaker system that is the concern. It's probably rated at 8 ohms, maybe 6.

That's fine because I had an all 4 ohm system in the garage before this one & the tweeters/midrange speakers were a little annoying standing 6 feet away from two 42 inch tall enclosures stacked on top of each other, I had the 4 ohm mid bass speakers & I decided I might as well use them so we will see what 1000 watts on the subwoofer's side does to the garage, the last 500 watt amp I had would pop open the circuit breaker box metal door for the house.

 

[WaynerN]

Glad you are not my neighbor..........

 

[garage inc.]

That's fine because I had an all 4 ohm system in the garage before this one & the tweeters/midrange speakers were a little annoying standing 6 feet away from two 42 inch tall enclosures stacked on top of each other, I had the 4 ohm mid bass speakers & I decided I might as well use them so we will see what 1000 watts on the subwoofer's side does to the garage, the last 500 watt amp I had would pop open the circuit breaker box metal door for the house.[ All blues, savoy brown, climax blues band, etc. & beer. The subwoofer low waves are very therapeutic for the old bones.

 

[toxcrusadr]

The impedance of these speakers in the operating range of that 4-ohm driver may be 4 ohms. But it's not a critical part of the spectrum - most of the power goes into the woofers due to physics, so that's where it's important to not let impedance drop too low. If it's not original and designed into the speakers though, replacing an 8 ohm driver with a 4 ohm will change the crossover points. That, along with just having a different driver, will affect the sound of the whole speaker.

 

[garage inc.]

The impedance of these speakers in the operating range of that 4-ohm driver may be 4 ohms. But it's not a critical part of the spectrum - most of the power goes into the woofers due to physics, so that's where it's important to not let impedance drop too low. If it's not original and designed into the speakers though, replacing an 8 ohm driver with a 4 ohm will change the crossover points. That, along with just having a different driver, will affect the sound of the whole speaker.

Doesn't my receiver just feed the plate amp the signal & the plate amp handles the load of the subwoofers & as for the tweeter, mid bass & midrange speakers, the xover points will change that I set because the 4 ohm mid bass will lower the 8 ohm crossovers impedance for the 8 ohm tweeters & midrange speakers? changing the xover points? I was hoping the crossovers worked independently from each other for their respective speaker, no problem I will just use a 8 ohm mid bass speaker & it will be all 8 ohm speakers & xovers on the receiver side of things, thanks.

 

[toxcrusadr]

Crossovers are RLC circuits - containing resistance (mainly in the voice coil), inductance (inductors in the crossover + the voice coil is an inductor), and capacitance. The behavior is dependent on the combination of the three. Have a look at the table on this page:

http://www.colomar.com/Shavano/crossover12db.html

Which gives inductor and cap values for various crossover frequencies, for both 4 and 8 ohm drivers. Note the cap and inductor values change by a factor of 2 for the same crossover frequency when the impedance changes from 4 to 8. Another way of saying it is if you keep the crossover components the same and change the driver impedance, the crossover frequency will change.

If you're selecting replacement drivers for an existing speaker, keeping the same nominal impedance should be item #1.

If you have a 4 ohm driver you want to use, it may work OK, but things will change as described.

 

[markn2wae]

If you are concerned about loading of the driving amplifier (not the sub amp) going too low below 4 Ohms WITH the sub woofer connected, there is no problems as POWERED subs do NOT put a heavy load on the driving amp.

What may happen if you use the "AMP IN-SPEAKER OUT" terminals on some subs and drive your main speakers through this connection, you may find (if so designed) your main speakers may be getting a slow "roll off" as you go lower in frequency at the same point the sub is "taking up the slack" so to speak, so in this condition your main amp is actually "working less hard" at the lower frequencies than WITHOUT the sub woofer (this applies only if the sub has a "high pass" filter in line with your main speakers AND you are driving them THROUGH the subs SPEAKER terminals as above.

Mark T.

 

[garage inc.]

If you are concerned about loading of the driving amplifier (not the sub amp) going too low below 4 Ohms WITH the sub woofer connected, there is no problems as POWERED subs do NOT put a heavy load on the driving amp.

What may happen if you use the "AMP IN-SPEAKER OUT" terminals on some subs and drive your main speakers through this connection, you may find (if so designed) your main speakers may be getting a slow "roll off" as you go lower in frequency at the same point the sub is "taking up the slack" so to speak, so in this condition your main amp is actually "working less hard" at the lower frequencies than WITHOUT the sub woofer (this applies only if the sub has a "high pass" filter in line with your main speakers AND you are driving them THROUGH the subs SPEAKER terminals as above.

Mark T.

Yes I used to have a Dayton 250 watt plate amp with high level inputs/outputs that high passed to main speakers, this Dayton 1000 watt plate amp I am using now has no high pass to main speakers just low level inputs & main speakers run off receivers speaker outputs, thanks.