Infinitys RS II

damonrink

damonrink

New Member
Hello all you gear heads out there in audio land! Got a simple question i'm sure for some of you out there. I just purchased a set of RS IIs and i would like to get my hands on as much info on these speakers as possible. Before i bought them a few of you recommend a very strong and quality amp stable at low ohm loads. I took the advise and bought a GFA- 555 II high current amp to drive them. It has not come in yet but should be soon. The biggest question on my mind concerning the speakers is, how the crossover works on the low end. I mean, when they were being demonstrated to me it sounded like the two woofers were being crossed over at different frequency's. Like the lowest woofer to the floor might be a sub and the upper one might be a woofer. Any help here would clear up a lot. I'm sure there is a lot more i don't no about these as well. I guess i need a RS II gu ru.
 
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there's a special LC circuit for the woofers that makes that operate in tandem similar to a single watkins woofer. One woofer increasingly takes over the frequencies as they get lower and lower, in the same way that the second voice coil in the watkins woofer takes over at a lower frequency. the reason for doing this isn't that hard to understand, but it may be beyond my skills of explanation depending on how much physics and speaker design knowledge you have. if you search the Infinity forum for "watkins woofer" you should be able to find some good info, or you can go here:

http://infinity-classics.de/infinity/models/Quantum-series-1976/index-Quantum.htm

and read the brochure pages 4-6 at the bottom about the Watkins woofer, which all carries pretty much straight over to your dual woofer design if you transplant the words "dual woofer" for "dual voice coil." if i'm incorrect on anything here, please chime in! hope this helps, though.

chris
 
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damonrink said:
Hello all you gear heads out there in audio land! Got a simple question i'm sure for some of you out there. I just purchased a set of RS IIs and i would like to get my hands on as much info on these speakers as possible. Before i bought them a few of you recommend a very strong and quality amp stable at low ohm loads. I took the advise and bought a GFA- 555 II high current amp to drive them. It has not come in yet but should be soon. The biggest question on my mind concerning the speakers is, how the crossover works on the low end. I mean, when they were being demonstrated to me it sounded like the two woofers were being crossed over at different frequency's. Like the lowest woofer to the floor might be a sub and the upper one might be a woofer. Any help here would clear up a lot. I'm sure there is a lot more i don't no about these as well. I guess i need a RS II gu ru.
Click to expand...

Congrats on picking them up.

If you do a little research (searching) on AK, you'd find this thread among many others. This thread contains a link to the technical data sheet below that was uploaded by "Todd G" who happens to use the same avatar as your bro.. "Audiodreamin". Does he use two names here?
 

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Congratulations on getting some great speakers, and having the smarts to get an amp right away that can handle them (the Adcom 555-II is safe with these, and if you ever do manage to push it too far (unlikely), the red light will come on and warn you).

Yes, the two woofers on the bottom do NOT produce exactly the same tones, as cdfac explained. You will find that similarly, the three midrange drivers each produce a different sound. This is all part of the "magic" which makes these speakers sound as good as they do.

Let us know your impressions after you have it all set up and have given them a fair listen. Be sure to try a variety of sources (LPs or CDs), as your system now will reveal things you've never heard before --both good AND BAD. You may not want to listen to half your CDs with something so revealing!
 
Congrats. You did very well getting that Adcom amp. A good match to the RSII's. You are going to hear music like you never have before. And those woofers produce some incredible low end punch.
 
RSll's

Wow, I had no idea that these speakers were designed the way they are, and each driver playing different parts of the frequency range. I can't wait to hear them on his new amp!:thmbsp:
 
Congrats and welcome to the Infinity addiction. That Adcom amp is an excellent match with the Infinity's, and should play them as loudly and cleanly as you're likely to ever need.

One word of caution: this combo is likely to reveal any upstream shortcomings, which will lead you to want to upgrade your pre-amp, sources, cables, etc. etc. etc. It's a terrible disease :banana:, but the end results can be audio nirvana :music:.
 
cdfac said:
there's a special LC circuit for the woofers that makes that operate in tandem similar to a single watkins woofer. One woofer increasingly takes over the frequencies as they get lower and lower, in the same way that the second voice coil in the watkins woofer takes over at a lower frequency.....

and read the brochure pages 4-6 at the bottom about the Watkins woofer, which all carries pretty much straight over to your dual woofer design if you transplant the words "dual woofer" for "dual voice coil." if i'm incorrect on anything here, please chime in! hope this helps, though.
Click to expand...

There is actually a difference here. The 2 10" woofers are not really a single Watkins dual-drive split into two parts, per se (even though the RS-II's brochure infers so).

The bottom 10" woofer fires in a lower frequency range, pretty simple. Bigger inductor, lower frequencies to the driver. But, it's still the same model woofer. Which means... same resonance frequency, same impedance rise at resonance, and same low-frequency roll-off approaching resonance.

The dual-drive woofer has a larger inductor in series with the 2-ohm voice coil, so the 2-ohm v.c. is only working at lower frequencies. But, since the impedance of this v.c. is lower, the amp will see less of an impedance rise as the driver is approaching resonance, and is therefore able to "push" the woofer a bit lower in the frequency band.
 
geoff727 said:
The bottom 10" woofer fires in a lower frequency range, pretty simple. Bigger inductor, lower frequencies to the driver. But, it's still the same model woofer. Which means... same resonance frequency, same impedance rise at resonance, and same low-frequency roll-off approaching resonance.

The dual-drive woofer has a larger inductor in series with the 2-ohm voice coil, so the 2-ohm v.c. is only working at lower frequencies. But, since the impedance of this v.c. is lower, the amp will see less of an impedance rise as the driver is approaching resonance, and is therefore able to "push" the woofer a bit lower in the frequency band.
Click to expand...

if i'm reading the schematic on infinity-classics.de correctly, there is no real difference in the wiring of the two woofers. are they not showing something? what you're saying makes sense, but i originally thought that somehow the circuit for the lower woofer was able to decrease it's effective impedance as it went deeper, if that's even possible.

as far as the watkins goes, all other things being equal except the VC impedance, do the resonance frequency, rolloff, and impedance curve shape change for a 4-ohm woofer compared to an 2-ohm, or are they functions only of woofer material, spider, cab dimensions, and maybe VC diameter?
 
cdfac said:
if i'm reading the schematic on infinity-classics.de correctly, there is no real difference in the wiring of the two woofers. are they not showing something? what you're saying makes sense, but i originally thought that somehow the circuit for the lower woofer was able to decrease it's effective impedance as it went deeper, if that's even possible.

as far as the watkins goes, all other things being equal except the VC impedance, do the resonance frequency, rolloff, and impedance curve shape change for a 4-ohm woofer compared to an 2-ohm, or are they functions only of woofer material, spider, cab dimensions, and maybe VC diameter?
Click to expand...

Are you reading the schematic for the -II or the -IIa/b? For the -II, the top woofer is in series with a 5mH inductor, the bottom has a 30mH. And, yes, there is something omitted- a 600uf shunt cap across the lower woofer's terminals. For the dual-drive woofer, the 'mechanical' resonance (that of the physical structure) may stay the same, but the 'electrical' resonance (affected by the voice coil and xover components) will change, yes. About how the specific shape of the curve will change, that I don't know.

Going back to the brochure for the RS-II, it shows both woofers having the same cut-off (which, of course, is actually a roll-off) on the bottom end. Whether this is the direct consequence of the resonance of the driver/voice coil impedance rise at resonance (and, as you said, the 'upstream' impedance would be different between the two woofers), or that big 1600uf series cap effecting a low-frequency filter, I really don't know.

Back to the books for me, I guess.
 
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