A description of IRS 4.5s

[Arkay]

Someone selling Infinity Reference Series 4.5 speakers had this to say about them:

Once you have heard these, you are spoilt as far as other speakers are concerned. I have never heard anything, other than Genesis at $20,000.00 upwards, that compares. The sound produced by the combination of the Emit Tweeters and the Emim Mids, along with two 12" Bass Drivers per cabinet is hard to describe. It depends very much on the Amplification, but a high current, high output unit is a must (speaking of which, if your amp can't cope with drops to 1 ohm loads during peaks, dont use it with these) Many superlatives have been used to explain the sound these produce, but seamless is one that springs to mind. From the lows of 24 Hz through to the 32000 Hz highs, with only +/- 3 db, these will reproduce everything that is provided from your source. They are equally at home with Solid State or Big Valve Amps and can be Bi-Amped for even more impressive results. These are speakers that are capable of incredible dynamic detail, yet the "shimmering" magic from those Emits will still send shivers up your spine.

Mine are a model or two lower down in the RS series (RS IIs), but the description still fits, as they can send shivers up my spine and chills down my spine, too! You DO hear things with these that you don't hear with other speakers. Often, that is great... sometimes, it leads to disappointment, as you will not want to listen to poorer-quality recordings on these.

[Note: I have no affiliation with the sale/seller. Just thought the description was worth sharing, for those who haven't heard these speakers... and maybe those who have!]

 

[ThinMan]

Even though I currently have the "lesser" 2.5:s I have to agree with the quote. This series of speakers truly is *very* impressive, and have got to be one of the finest loudspeakers ever produced. I am biamping them with a Kenwood L-1000C as a preamp, L-1000M for the woofers and a Dynavox VR70-E2 tube amp for the mids/tweeters. Together this produces a sound that has made me into a true audioholic, the bass is exact and gutsy, the highs silvery shimmering and I find I have a constant smile on my face and a warm sensation in my body. Every evening, after the kids have gone to bed, I must listen to music, it´s almost like an addiction. Dylans "Time out of mind" has now returned to my playlist, as have every rrecord that has a nice production. The downside is of course that bad recordings are now practically unlistenable. But what a loudspeaker! Get these if you can, you will not be disappointed!

 

[robertk]

I have a pair and have had them for decades.

You are going to have to spend a lot of $$$$ on amplifiers to drive them. Much more than the cost of the speakers themselves. At that point, you'll have something.
Specifically, I use a krell ksa 100 just to drive the bass on these.

A tube amplifier for midrange is ideal and you'll need some money for cables as well.

 

[Nakdoc]

In our store we had 4.5s and a pair of 6.5s made with 32 6" woofers per cube for Jon Nork of Absolute Sound in a custom deal. The 4.5 were very difficult to balance unless they were brought well out into the room. Of the two the 6.5s sounded even more effortless, if you can imagine. We perched some Rogers LS3/5a on the 4.5's shoulder and A/B'd using the woofers in biamp. Suprisingly close. When the mid panels are far from the wall you really cannot hear the rear radiation...I remain puzzled by that observation.

 

[Vitopanch]

Nakdoc,
Whoa, 6'5's. I have never heard of those. Were those the only two that were made to your knowledge? By any remote chance do you have pictures? Also too, I have been seeking knowledge about a design difference in the RS 4'5's. Mine are a bit different in appearance than all of the other RS 4.5's that I have seen. Do you know as to whether mine were a later or earlier model or custom. The fella that I bought them from, the original owner, bougth them new this way. A picture is attached.
Vito

 

[robertk]

It's my understanding that physically they all looked identical. The difference was in the crossover network--both the external unit and quite a bit of modification to the crossover network in the back of the speaker.

Mine look identical to yours.

 

[phaedrus]

Mine look identical to yours.

Robertk,

Which "yours"? Vito's is on the left, and a "standard" 4.5 is on the right. Mine look like the one on the right, and Vito's is the only one I've ever seen with that neat V-shaped wood cutout beside the EMIMs.

David

 

[robertk]

On the right.

Was that a dealer or individual's modification? Or, it came from Infinity that way?

doeesit still have the detachable covers?

 

[Vitopanch]

robertk,
It came from Infinity that way. I do not know as to whether is was a special order from the dealer or a commercial vrsion, however, the original owner bought it that way from the dealer,. Yes, the grills remove the same way.
Vito

 

[robertk]

Some of those early absolute sound issues covered the 4.5 Then once the IRS came out it became almost impossible overnight to find anything out about them. However, they did mention the crossover issues and gave serial numbers I seem to recall, to help identify what is what.

I seem to recall the dealer at the time saying far more were exported than ever stayed in the U.S.

 

[Vitopanch]

Hail,
I found out why there are two different versions. As it was explained to me, there were only 200 to 300 RS 4.5's that were made and that the version that I have was a special order for clients that wanted the midrange to be more out in front. Infinity did this a lot whereas as sales worked with clients, special orders were accomodated during production runs. The internals of the loudspeakers are the same.

Vito

 

[phaedrus]

Vito,

Very interesting, glad you got to the bottom of it. I have to say I like the looks of yours a lot.

I didn't realize the 4.5 was that limited a production run. I have been trying to find production figures on the older Infinities but have been unable to do so. Good data point.

David

 

[Vitopanch]

Hail,

Vito,

I didn't realize the 4.5 was that limited a production run. I have been trying to find production figures on the older Infinities but have been unable to do so. Good data point.

David

The RS 4.5 was not a mass produced loudspeaker, that is why. Each dealer pretty much received a display model, with the larger ones getting one or two in stock. It was mostly a loudspeaker that was ordered from the factory. At $4500.00 clams back in 1979 not many, including me, could cough up that kind of cash for them. I saw my first pair at Tech HiFi in 1979/80 and nearly dropped dead at the demo with the music that came out of them. Now that I am out of the woods from raising a family, I set about finding a pair, which I did early this year. I then set it up with the same power amplifiers that they used during the Tech hifi demo and here I sit. The problem is however, I now want a pair of each version to set up in the corners of the room, Ha Ha.

Vito

 

[Jeff M]

Vito, how would you compare the sound of the 4.5's to the RS1B's? I love my 1B's, but I sure would to hear some of the real big boys that Infinity put out back then

 

[Vitopanch]

Hail Jeffm,
I love the RS1B's as well. They both actually will produce fabulous music comparably with many types of music. The significant difference is with music that has a lot of ensemble work and soundstage in it as a source. For example; symphonic music, choral music, Allman Brothers, Moody Blues, jazz quartets to name a few. The RS 4.5 soundstage is wide and DEEP, VERY DEEP. Harmonies, instrumental and vocal nuances can be heard that are not heard on many other loudspeakers are there with DEPTH. The music is there without a sense of the loudspeakers themselves.

When it was developed and subsequently debuted at the Consumer Electonics Show in Chicago, it was tuned and voiced in alliance with Soundstream, Jack Renner, which was the first company to do digital recordings in the world with Telarc, along with the IRS which was at the debut as well, to do A/B comparisons. The IRS as you know was built as their internal reference loudspeakers that all others were bench marked against. With this tuning they were able to achieve phase coherance that other loudspeakers could not. Truly a historic acheivement.
Vito

 

[Vitopanch]

Here is an unusual pair.

Vito

 

[phaedrus]

Vito,

Very interesting look on those. Sort of a quasi-Beta physical layout. I wonder how well the horizontal EMIMs do with dispersion though?

Have you heard these? Were these a "one-off" design or did they actually produce a number of them like this?

David

 

[Vitopanch]

David,
No, I have not heard them. A fella in Germany that I was talking to owns them. He claims that they are more coherant in this formation. It was a 'running production change' no doubt as he says that he ordered them this way. I do know that Infinity accomodated requests of this ilk frequently.

The purpose of the full padding on the standard configuration is to reduce reflections off of the baffle board, because at certain frequencies, the midrange frequencies were folding back onto themselves and phase cancelling each other coming off of the baffle board. With my design, the midrange frequencies are a more more forward than with the full padding.

It is tough to conjecture as to what his sound like, however, he paid bucks to have them this way and loves them. If only we were rich we could search the globe and start a collection of all of the variations of vintage Infinities.
It is fun to collect the pictures and stories that are associated with them anyways.

Vito

 

[phaedrus]

Hi Vito,

Thanks for the update. You sure do know a lot of Infinity people!

The reason I was asking about the dispersion issue is because this design seems to contradict what I (thought I) knew about their design concepts. My understanding (from Infinity literature) was that the whole point of the EMIT/EMIM vertical line source was that it had high horizontal dispersion and low vertical dispersion, minimizing the floor/ceiling first reflections and reducing sound smearing.

This fellow's design seems to stand that on its head, with high vertical dispersion and low horizontal dispersion.

I realize the Delta/Gammas had the L-EMIM positioned sideways, but I thought that was a design compromise to fit everything into one tower. You don't see sideways EMITs or EMIMs in any other Infinity design.

Oh well, live and learn, I guess.

Thanks,

David

 

[Vitopanch]

Hi Vito,

The reason I was asking about the dispersion issue is because this design seems to contradict what I (thought I) knew about their design concepts. My understanding (from Infinity literature) was that the whole point of the EMIT/EMIM vertical line source was that it had high horizontal dispersion and low vertical dispersion, minimizing the floor/ceiling first reflections and reducing sound smearing.

This fellow's design seems to stand that on its head, with high vertical dispersion and low horizontal dispersion.

David

David,
Yes, I agree with you and that is exactly my understanding. I was non-plussed when he showed the pictures. I would love to hear them to confirm or dispell what he is saying, but alas.... I am going to dig into it more.

Vito