YASpeakerT: Resistance of Speakers

[Toastedlightly]

So, I am trying to get into this whole expensive audiophile thing. I have an embarrasing question (or two) though:

Do revievers need a certain resistance of speaker? I see 4, 6 and 8 ohm speakers and was wondering which would be appropriate (no, I don't know my current speakers resistance, can't find any specs on it).

Also, after looking at a crossover diagram, is it possible to tell what the resistance of that speaker will be (given that you know the speakers to be used themselves)?

Thanks


Here are the 2 way loudspeaker plans I am looking at:

Woofer: P17WJ00 6-1/2?
http://www.madisound.com/cgi-bin/index.cgi?cart_id=5318945.8427&pid=1358

Tweeter: D25AG35 1? dome tweeter
http://www.madisound.com/cgi-bin/index.cgi?cart_id=5318945.8427&pid=1323

Crossover Diagram:
http://users.ece.gatech.edu/~mleach/labsp2/crsnet.gif

Yes, I am kinda a noob. Don't need to tell me the overall resistance, just give me the direction to do so.

 

[YOyoYOhowsDAjello]

Generally we're talking impedence for speakers instead of resistance. Your average low end to midrange receiver is meant to be run with speakers that have a nominal impedence of 8 ohms. That's not to say that you can't run other impedences, but the lower the rating, the more strain you'll be putting on your amps.

I'm really not a speaker building guy so I can't help you out there, but I'm sure someone like Howard could give you good advice in that department.

 

[Pepsi90919]

Originally posted by: YOyoYOhowsDAjello
Generally we're talking impedence for speakers instead of resistance. Your average low end to midrange receiver is meant to be run with speakers that have a nominal impedence of 8 ohms. That's not to say that you can't run other impedences, but the lower the rating, the more strain you'll be putting on your amps.

I'm really not a speaker building guy so I can't help you out there, but I'm sure someone like Howard could give you good advice in that department.

i should really know the answer to this, but why would LESS impedence mean MORE strain on the amp? wouldn't less volume be needed?

 

[Rubycon]

Originally posted by: Pepsi90919

i should really know the answer to this, but why would LESS impedence mean MORE strain on the amp? wouldn't less volume be needed?

Lower impedance implies higher current draw (assuming regulated output stage which it SHOULD be) so yes it will get louder.

A signal from an amp is alternating current so the correct term is impedance not resistance. A loudspeaker can often read lower DC resistance but have a higher impedance. This really depends on the crossover as well. A well designed crossover will include conjugate load matching where for a given frequency and impedance a proportionately inverse impedance is presented. This allows for flatter frequency response with stiffly regulated reference amplifiers.

Some speaker builders will actually use this as a form of passive equalization. As the frequency drops, so does the impedance! This will draw more current from the amp resulting in better bass extension. Of course if an amplifier is used that doesn't "jive" with this, the bass rolloff is augmented and the amp will get unstable and nasty things usually prevail. :Q

 

[Fenixgoon]

Originally posted by: MS Dawn

Originally posted by: Pepsi90919

i should really know the answer to this, but why would LESS impedence mean MORE strain on the amp? wouldn't less volume be needed?

Lower impedance implies higher current draw (assuming regulated output stage which it SHOULD be) so yes it will get louder.

A signal from an amp is alternating current so the correct term is impedance not resistance. A loudspeaker can often read lower DC resistance but have a higher impedance. This really depends on the crossover as well. A well designed crossover will include conjugate load matching where for a given frequency and impedance a proportionately inverse impedance is presented. This allows for flatter frequency response with stiffly regulated reference amplifiers.

Some speaker builders will actually use this as a form of passive equalization. As the frequency drops, so does the impedance! This will draw more current from the amp resulting in better bass extension. Of course if an amplifier is used that doesn't "jive" with this, the bass rolloff is augmented and the amp will get unstable and nasty things usually prevail. :Q

*head asplodes*:Q

 

[AlienCraft]

Originally posted by: Fenixgoon

Originally posted by: MS Dawn

Originally posted by: Pepsi90919

i should really know the answer to this, but why would LESS impedence mean MORE strain on the amp? wouldn't less volume be needed?

Lower impedance implies higher current draw (assuming regulated output stage which it SHOULD be) so yes it will get louder.

A signal from an amp is alternating current so the correct term is impedance not resistance. A loudspeaker can often read lower DC resistance but have a higher impedance. This really depends on the crossover as well. A well designed crossover will include conjugate load matching where for a given frequency and impedance a proportionately inverse impedance is presented. This allows for flatter frequency response with stiffly regulated reference amplifiers.

Some speaker builders will actually use this as a form of passive equalization. As the frequency drops, so does the impedance! This will draw more current from the amp resulting in better bass extension. Of course if an amplifier is used that doesn't "jive" with this, the bass rolloff is augmented and the amp will get unstable and nasty things usually prevail. :Q

*head asplodes*:Q

Cool, I love it when n00bs do that.

 

[Viperoni]

A speaker built with those 2 drivers will have an average impedance between 6-8ohms, but in the area where it matters (the bass region), it'll be high enough not to cause a big problem.

MS Dawn, I see what you're getting at, but take for example the average woofer. The box is irrelevant. It'll have an impedance peak at the system's resonant frequency (for a sealed box this is dependant on the box size, for a ported box it's the box's tuning frequency, etc), and this means that the power output from the amplifier would be very low because of the high impedance. This doesn't mean there's a dip in frequency response at that impedance peak though.

 

[Fenixgoon]

Originally posted by: AlienCraft

Originally posted by: Fenixgoon

Originally posted by: MS Dawn

Originally posted by: Pepsi90919

i should really know the answer to this, but why would LESS impedence mean MORE strain on the amp? wouldn't less volume be needed?

Lower impedance implies higher current draw (assuming regulated output stage which it SHOULD be) so yes it will get louder.

A signal from an amp is alternating current so the correct term is impedance not resistance. A loudspeaker can often read lower DC resistance but have a higher impedance. This really depends on the crossover as well. A well designed crossover will include conjugate load matching where for a given frequency and impedance a proportionately inverse impedance is presented. This allows for flatter frequency response with stiffly regulated reference amplifiers.

Some speaker builders will actually use this as a form of passive equalization. As the frequency drops, so does the impedance! This will draw more current from the amp resulting in better bass extension. Of course if an amplifier is used that doesn't "jive" with this, the bass rolloff is augmented and the amp will get unstable and nasty things usually prevail. :Q

*head asplodes*:Q

Cool, I love it when n00bs do that.

....unless you mean about audio building, cause i have more posts than you (granted i joined later)😛

 

[Toastedlightly]

Originally posted by: Viperoni
A speaker built with those 2 drivers will have an average impedance between 6-8ohms, but in the area where it matters (the bass region), it'll be high enough not to cause a big problem.

MS Dawn, I see what you're getting at, but take for example the average woofer. The box is irrelevant. It'll have an impedance peak at the system's resonant frequency (for a sealed box this is dependant on the box size, for a ported box it's the box's tuning frequency, etc), and this means that the power output from the amplifier would be very low because of the high impedance. This doesn't mean there's a dip in frequency response at that impedance peak though.

Now, any way to explain why or a website to point me to for an explanation? I don't just want sound, I want knowlege!

 

[Rubycon]

Originally posted by: Viperoni
A speaker built with those 2 drivers will have an average impedance between 6-8ohms, but in the area where it matters (the bass region), it'll be high enough not to cause a big problem.

MS Dawn, I see what you're getting at, but take for example the average woofer. The box is irrelevant. It'll have an impedance peak at the system's resonant frequency (for a sealed box this is dependant on the box size, for a ported box it's the box's tuning frequency, etc), and this means that the power output from the amplifier would be very low because of the high impedance. This doesn't mean there's a dip in frequency response at that impedance peak though.

It really depends on what's driving that woofer. In a full active system (where every driver has its own amp) this is much more critical than a full range system. This is why some amps are known to make certain speakers "sing" as well. 😉

 

[YOyoYOhowsDAjello]

Originally posted by: Toastedlightly

Originally posted by: Viperoni
A speaker built with those 2 drivers will have an average impedance between 6-8ohms, but in the area where it matters (the bass region), it'll be high enough not to cause a big problem.

MS Dawn, I see what you're getting at, but take for example the average woofer. The box is irrelevant. It'll have an impedance peak at the system's resonant frequency (for a sealed box this is dependant on the box size, for a ported box it's the box's tuning frequency, etc), and this means that the power output from the amplifier would be very low because of the high impedance. This doesn't mean there's a dip in frequency response at that impedance peak though.

Now, any way to explain why or a website to point me to for an explanation? I don't just want sound, I want knowlege!

For general info, this might be a good forum to look at.
http://www.avsforum.com/avs-vb/forumdisplay.php?f=155

I'm sure if you hunt around there will be plenty of good links in threads there too 😛

 

[Viperoni]

Originally posted by: Toastedlightly

Originally posted by: Viperoni
A speaker built with those 2 drivers will have an average impedance between 6-8ohms, but in the area where it matters (the bass region), it'll be high enough not to cause a big problem.

MS Dawn, I see what you're getting at, but take for example the average woofer. The box is irrelevant. It'll have an impedance peak at the system's resonant frequency (for a sealed box this is dependant on the box size, for a ported box it's the box's tuning frequency, etc), and this means that the power output from the amplifier would be very low because of the high impedance. This doesn't mean there's a dip in frequency response at that impedance peak though.

Now, any way to explain why or a website to point me to for an explanation? I don't just want sound, I want knowlege!

Really, I learned from being on the PartsExpress and Madisound forums, reading webiste, and chatting with a lot of DIY'ers back in the day.
Also, Vance Dickason's "Loudspeaker Cookbook" is supposed to be very good, don't have it myself.


On another note, I have Vifa P17WG09-04 (4ohm, car model) 6.5's in my doors, and they handle power pretty nicely. I've got probably 100 watts RMS on tap, and they do a great job of handling the power. Sounds quality is pretty decent too. I'm looking for more of everything, so I'll probably upgrade them in the summer, but for a lower end driver, I'm plenty happy with them.

 

[Rubycon]

Text

 

[Viperoni]

Originally posted by: MS Dawn

Originally posted by: Viperoni
A speaker built with those 2 drivers will have an average impedance between 6-8ohms, but in the area where it matters (the bass region), it'll be high enough not to cause a big problem.

MS Dawn, I see what you're getting at, but take for example the average woofer. The box is irrelevant. It'll have an impedance peak at the system's resonant frequency (for a sealed box this is dependant on the box size, for a ported box it's the box's tuning frequency, etc), and this means that the power output from the amplifier would be very low because of the high impedance. This doesn't mean there's a dip in frequency response at that impedance peak though.

It really depends on what's driving that woofer. In a full active system (where every driver has its own amp) this is much more critical than a full range system. This is why some amps are known to make certain speakers "sing" as well. 😉

I run an active front stage in my car 😉

Can you explain the phenomenon better? I understand what you're saying in terms of impedance, but it's like you're implying the DCR of a driver, if really low, will lead to augmented FR below the system's resonant frequency... which I can't see happening since all box types have their own specific rolloff-rate below their resonant frequencies...

Are you trying to say that a driver with a greater impedance peak @ it's Fs when measured in free air, will have a larger frequency response peak when placed into a box?

 

[AlienCraft]

Originally posted by: Fenixgoon
....unless you mean about audio building, cause i have more posts than you (granted i joined later)😛

LOL, like post count matters when talking about audio, transducer frequency / power relationships, impeadance and crossover (filter) designs.
Naw, I wouldn't know anything about that.

I was 12 when my dad first tried explaining impedance versus resistance to me. This simple demonstration did it for me.

Get a sweepable frequency source (Oscillator), amplifier, VOM meter and speaker.
Connect them so one can read the "resistance" of the speaker.
Apply power and sweep the frequency. One should observe a modulation of the meter (indicating the changng resistance) as the frequency changes.

If you change the VOM setting to AC Voltage ( Or have another meter), one could also observe the changing OUTPUT Voltage of the amplifier, It will show an INcrease in Voltage as the Frequency is swept DOWN, with anomolies depending on speaker Cabinet / crossover / transducer interaction (design).


Change the input source to a music source and then observe the meters. One will see that simply getting music out of a moving paper cone attached to an electro-magnet is a pretty cool thing.

 

[Rubycon]

Originally posted by: Viperoni

Are you trying to say that a driver with a greater impedance peak @ it's Fs when measured in free air, will have a larger frequency response peak when placed into a box?

It's only going to change depending on the loading principle. 😉

It also depends on your amplifier's design and how feedback is used.

So called "free air" woofers are a huge compromise but then again what is car audio all about? 😉 There are woofers designed for ported boxes that can be run free air without a problem chiefly because they were designed for hard use in a pro (reinforcement) environment, etc. Drivers like this often employ shorting rings at the end of the voice coil to as a form of braking at Vmax, etc. There have been other experiments performed where sufficient room exists to build larger boxes. One was a two driver system where the second driver was used as a passive radiator and fed a signal to dynamically change its compliance. Specially wound voice coils can be used in single driver systems too. There's a plethora of testing out there that the car guys never get involved with as these boxies are HUGE!

Keep in mind that I'm more of a studio engineer/entertainment person not an equipment design engineer. 😉

Originally posted by: AlienCraft
. One will see that simply getting music out of a moving paper cone attached to an electro-magnet is a pretty cool thing.

And getting accurate reproduction of the original is a very difficult science sometimes borderline amazing. 🙂