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Discussion Starter · #1 ·
Hello, I have been a long time reader of AVSforum and really have learned a lot here from the community. I am really inspired by a lot of what I see in the dedicated home theater section and I'm designing my own theater for the room we are building over the garage. I have learned a lot here by reading others advice and I hope someone can help me figure this out, I researched it here but its sort of specific.


I've got all my audio gear for the most part and I'm testing it to see how it all works together. A long time ago my uncle gave me a set of AWESOME Infinity RS IIa towers and I have taken good care of them.


won't let me post a link or pic but if you google image search "Infinity RS IIa" bobbyshred has some just like mine.


Recently I picked up a set of 4 Clarion SL6 speakers, a B&W center channel, and a Klipsch 10'' sub in preparation for my dedicated theater build. The speakers were sold to me with an old Yamaha HRT-5250 receiver which is an older first generation AVR that supports 5.1 surround.


I bought a Harman/Kardon AVR254 recently because it supports HDMI switching and 7.1 surround. I plan to use the H/K as my main amp for the Clarion SL6 speakers that I will be using as surrounds and it will handle the center channel and the "high frequency inputs" into the RS IIa Towers. There is one issue that I'm running into though. My uncle doesn't have the Infinity LFE and he didn't give it to me with the speakers.


I've been reading the owners manual for the Infinity set and it says you really need the LFE even if you only run one amp to these speakers.


Here's what I want to do and I'm hoping someone can help with some solid audio knowledge. I'm planning to run two amps to the Infinity set. I decided against using the Yamaha 5.1 AVR to preamp because its super complicated...I want to have an old Technics sa-ex110 (2ch 100Watts per channel 8 Ohms) power the woofers on the Infinitys. I am looking to take the "preout Right front and Left Front" output connections from the H/K 7.1 and put them into the CD source Inputs on the technics amp to run enough juice to the woofers to get clean sound from them. The H/K is 50 watts x 7 channels 8 Ohms, and 2 Channels 65 watts at 8 ohms.


The infinity reference manual for these speakers says that they need between 70 and 400 watts per channel at 4 Ohms to the woofers and high frequencies need between 75 and 300 watts per channel at 4 Ohms. I just want to make sure that I'm understanding whats going on with the ohms so I don't blow these beauties up or damage them.


I'm wondering: Will the wattage going to the woofers on the Infinity towers be 200 watts (100 watts at 8 ohm would be 200 watts at 4 ohm?)for each the right and left channel? Will it be a higher wattage than 200 per channel for the woofers since its getting it's input from the H/K's preout's ? Will the setup described above damage these speakers ? Do I really need the LFE that I'm missing if I'm going to have a dedicated preamp for just bass to the woofers anyways?


If anyone sees any options with the equipment that I may be missing I'd love to hear them. I'm just trying to learn all I can to do this setup justice... it already sounds great but I know it will really come to life once I get this figured out.


Thanks for your help.

B
 

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Quote:
Originally Posted by Bojacked /forum/post/18312154


I bought a Harman/Kardon AVR254 recently because it supports HDMI switching and 7.1 surround. I plan to use the H/K as my main amp for the Clarion SL6 speakers that I will be using as surrounds and it will handle the center channel and the "high frequency inputs" into the RS IIa Towers. There is one issue that I'm running into though.

Ok.

Quote:
My uncle doesn't have the Infinity LFE and he didn't give it to me with the speakers. I've been reading the owners manual for the Infinity set and it says you really need the LFE even if you only run one amp to these speakers.

I owned the RS2b's for several years in the '80s, and it is night and day difference without the EQ. Nowadays you could probably simulate most of it with a Behringer parametric EQ, for example, if you can find a plot of the response. I saw one back in the day by Bascom King in Stereophile IIRC. Might want to have a rummage around Uncle's boxes, though before you give up.

Quote:
Here's what I want to do and I'm hoping someone can help with some solid audio knowledge. I'm planning to run two amps to the Infinity set.


I want to have an old Technics sa-ex110 (2ch 100Watts per channel 8 Ohms) power the woofers on the Infinitys. I am looking to take the "preout Right front and Left Front" output connections from the H/K 7.1 and put them into the CD source Inputs on the technics amp to run enough juice to the woofers to get clean sound from them. The H/K is 50 watts x 7 channels 8 Ohms, and 2 Channels 65 watts at 8 ohms.

Should work once the gains are set correctly.

Quote:
The infinity reference manual for these speakers says that they need between 70 and 400 watts per channel at 4 Ohms to the woofers and high frequencies need between 75 and 300 watts per channel at 4 Ohms. I just want to make sure that I'm understanding whats going on with the ohms so I don't blow these beauties up or damage them.

While the 4-ohm rating might stress the amps, it will not hurt the speakers. If the amps shut down or overheat, I'd stop using them and seek something more robust. Otherwise, continue.

Quote:
I'm wondering: Will the wattage going to the woofers on the Infinity towers be 200 watts (100 watts at 8 ohm would be 200 watts at 4 ohm?)for each the right and left channel?

You will be tending to pull more juice than the 100w 8-ohm rating, but how much depends on the amp's power supply.

Quote:
Will it be a higher wattage than 200 per channel for the woofers since its getting it's input from the H/K's preout's ?

No, there is no cascading effect for power.

Quote:
Will the setup described above damage these speakers ? Do I really need the LFE that I'm missing if I'm going to have a dedicated preamp for just bass to the woofers anyways?

As above.
 

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Discussion Starter · #3 ·
Roger, Thanks for your response! I checked out your theater and wow what a sweet setup! I love the amp rack and center channel stand you have. Running all the wires in the soffits and having them swing down like that is brilliant. I think I'm going to have to really sit down and study your setup and soundproofing before I get into my dedicated build in a room over the garage.


I emailed my uncle and he dug around and found the old Infinity LFE that was paired with these speakers! He is still looking for the power cord though it's sort of specific (13-14 volts AC ; 50-60 Hz). Hopefully it will turn up. I will keep ya posted.


I'm still wondering about the 8 Ohm amplifiers to the 4 Ohm rated speakers. Is the amperage doubled because there is half the resistance from 8 Ohm to 4 Ohm? So putting in 100 Watts a channel 8 Ohm is really pushing 200 Watts a channel at 4 Ohms due to the resistance being lower?


Also if I were to push a higher wattage to these and get a better dedicated amp for these speakers would the sound just be louder or would it change the actual sound profile at even lower sound levels?


B
 

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Quote:
Originally Posted by Bojacked /forum/post/18314963


Roger, Thanks for your response! I checked out your theater and wow what a sweet setup! I love the amp rack and center channel stand you have. Running all the wires in the soffits and having them swing down like that is brilliant. I think I'm going to have to really sit down and study your setup and soundproofing before I get into my dedicated build in a room over the garage.

Thanks for the high praise!

Quote:
I emailed my uncle and he dug around and found the old Infinity LFE that was paired with these speakers! He is still looking for the power cord though it's sort of specific (13-14 volts AC ; 50-60 Hz). Hopefully it will turn up.

Great that he found the box. That's the hard part--the transformer is easy. Might be able to use one of these in the 13v setting, as Radio Shack has a selection of tips that can mate with it. Take the box with you to the store to get the correct fit.

Quote:
I'm still wondering about the 8 Ohm amplifiers to the 4 Ohm rated speakers. Is the amperage doubled because there is half the resistance from 8 Ohm to 4 Ohm? So putting in 100 Watts a channel 8 Ohm is really pushing 200 Watts a channel at 4 Ohms due to the resistance being lower?

Theoretically, yes. But whether a given amp rated only at 8 ohms will really double the power into 4 ohms depends on the output stage and moreover the power supply.

Quote:
Also if I were to push a higher wattage to these and get a better dedicated amp for these speakers would the sound just be louder or would it change the actual sound profile at even lower sound levels?

Whether a higher power amp will sound louder depends on if you are running out of steam on the lower power amp. If it is not clipping, and it's already loud enough, I would not expect a huge change in quality. It's a very subjective thing--though. Best to start with what's in hand, and see how it fares.
 

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Discussion Starter · #5 ·
Here's a photo of the towers if it will let me post it this time. It was hard to find the same model I have but this is it




Soon they will be played as they were meant to be
 
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