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Restoring bass performance on your RS4.5's

According to the passive crossover schematic, connecting an amp up to the woofer terminals will not bypass the inductors and large NPEs in the woofer circuit-- you will need these for proper operation of the Watkins woofer so this is a good thing.

I am wondering how you bypass the upper crossover, do you just connect up to the EMIM and EMIT terminals in the upper rear of the speaker or maybe connect to their terminals in the passive crossover?

I find a 100 Hz crossover is too low in my room with these speakers, I get quite a bit of dipolar cancellation in the 100-200 Hz region. This actually sounds a bit thin on many recordings and I confirmed it with pink noise and a 1/3 octave spectrum analyzer (Phonic PAA2). I prefer crossing over at 200-220 Hz, either 6 dB/octave or 24 dB/octave L-R. I can get quite a flat response with the pink noise using this crossover. I mostly use either a Bryston 10B or Marchand XM-26 active crossover.

I find the passive crossover (late version) and a powerful single amp can be quite good as well, and occasionally prefer this to biamping. Lately I have been biamping using tubes on top (Music Ref RM-9) and Mac solid state on the bottom to good effect.
 
My understanding is when you flip the switch to bi-amp mode, the woofer circuitry operates direct from info recieved from the bass amp and low pass of xover. the upper passive xover in the 4.5's have to much garbage in them, they sound far better direct driven. the emim's will eq 100hz flat, the reason I do this is to keep vocals out of the woofer. on orchestral I xover at 150hz, programed in DBX memory :) . I also use tube's on top end as well when I like a change. AR D250 on mids, AR D150 on tweets.
 
With the passive crossover switch in biamp mode and the jumpers removed from the speaker terminals, you will disconnect the woofer circuitry from the mid- and high-frequency sections of the crossover. The low frequency signal will still pass through a substantial number of passive components before arriving at the 2 dual-coil woofer terminals. Some of this circuitry is needed to process the signal to drive the Watkins woofer.

To see a schematic, go here:

http://www.infinity-classics.de/infinity/technik/manuals/RS_4.5_technical_sheet.pdf

Your EMIMs must be in good shape to withstand EQ, I think mine are in less good shape! ;)
 
That circuitry just controls the drive of the 2 voice coils on low pass side, It's separate from the upper in bi-amp mode and is limited to what ever the low pass allows. Thats the nice thing about the dual drive, with good amps it has the ability to move lots of air with short pistonic action due to speed and dampning factor. :)
 
The bi-amp switch just changes the crossover frequency. The crossover is still in circuit ;) In bi-amp mode the crossover frequency is lowered.
 
Odd I can't find anything about that in my 4.5 manual that came with the speakers when I bought them new, and it's not in the active crossover manual either. learn something new everyday.
 
InAp said:
Odd I can't find anything about that in my 4.5 manual that came with the speakers when I bought them new, and it's not in the active crossover manual either. learn something new everyday.
Click to expand...

It's inferred on the schematic diagram of the passive crossover ;)
 
rabbit said:
It's inferred on the schematic diagram of the passive crossover ;)
Click to expand...

Yep, all the switch does is move the low pass "corner" frequency of the woofers substantially above the nominal 150 Hz passive crossover frequency, and move the high pass corner of the EMIMs substantially below that same 150Hz crossover.

The switch allows an active crossover like the Infinity or similar unit to determine the actual crossover between woofers and EMIMs by doing the filtering prior to feeding the signal to the bass and mid/high amps. The range of values over which the active crossover can adjust the crossover between the woofs and EMIMs is implied by the Infinity active crossover range, 110Hz - 440Hz. In other words, I wouldn't try to set an active crossover much below 110Hz or much above 440Hz.
 
kmanusa said:
Yep, all the switch does is move the low pass "corner" frequency of the woofers substantially above the nominal 150 Hz passive crossover frequency, and move the high pass corner of the EMIMs substantially below that same 150Hz crossover.

The switch allows an active crossover like the Infinity or similar unit to determine the actual crossover between woofers and EMIMs by doing the filtering prior to feeding the signal to the bass and mid/high amps. The range of values over which the active crossover can adjust the crossover between the woofs and EMIMs is implied by the Infinity active crossover range, 110Hz - 440Hz. In other words, I wouldn't try to set an active crossover much below 110Hz or much above 440Hz.
Click to expand...

It's funny but the series LC tank circuit in the woofer crossover still has the same resonant frequency in either switch position. All that changes is the Q of this circuit.
 
Yes, I think the Watkins-related components in the woofer circuit do not seem to be much affected by the biamp switch. I have fiddled around with modeling the woofer circuit using PSPICE. The biamp switch primarily changes the woofer upper rolloff in the woofer circuit although the Q is affected a bit as you point out. The tank circuit really comes into play in the very low frequencies where the impedance drops below 2 ohms at around 25 Hz as I recall (it's been a while since I looked at this).
 
Great detailed thread here! I hope to gut my newly acquired RS-IIIa's one day soon and see whats lurking in them. Because the bass response seems to be lacking on them as well to my ears.
 
This is a fabulous thread - I am gradually working through the items covered in this thread in a pair of RS4.5 and the insights presented here are invaluable.
I have so found mis-wired watkins in my RS2.5s causing low (relatively) bass. Im working through getting an understanding of how these larger RS4.5 work and gradually tracing the wiring in mine to check that all is good. Have been a bit busy at work and just listening to them to get too far to find much amis as yet.
But I wonder just how common such a reversal between the 2 coils in the watkins is in the various infinity speakers over the years, especialy following reconing or service. It seems such an obvious thing to check, yet several posts and threads have mentioned it over time as well as my own experience . Perhaps some grand old Infinities have been moved on as no longer wonderful due simply to mis wiring.
 
No - single amp. Currently a NAD 218 is being used, but I have a Perreaux 8000C ready to go and possibly a second one to put into service as well. I have an original infinity active crossover as well as an Ashley XR2001 unit to experiment with, but have yet to have the amplifiers ready to connect to - so single amp it has been.
Currently bass does not seem a problem, but Im not generating very large levels (kids have been studying for university and would not take kindly to the delinquent noisy old people creating that much noise) - I did initally think the bass was not that huge, but these infinites’ are so flat in response that there is no real bass peak just lots of presence.
I recall reading somewhere that the RS-4.5 worked better with a single large amp than biamped - but that being said I intend to try the 8000C initially then biamp with the two of them (although I may need to do some work on the electricity supply to the listening room first).
Since my last post on this thread, I have obtained a pair of QLS-3 that also had the polarity of the voice coils reversed on the 2-ohm side. Once that was fixed they sound great - but not quite in the same league as the RS-4.5
 
The 4.5's have to be bi-amped to sound thier best, the orginal folder that comes with them new also states that.
 
Another thing to remember, Some Infinity crossovers invert, so if it sounds bass shy, swap the minus and positive on the speaker
 
Do the Infinity RS crossovers invert on both HIGHS and LOWS? I interpret as both are inverted and the positive/negative swap should take place at the speakers. Of course this is in a bi-amped situation.
 
The ACTIVE crossover that came with the 4.5's, that was optional on the 2.5's, inverts phase. The passive built in crossover does not. If using the active crossover, you need to swap leads at the back of the speaker. ie. red from amp goes to black on speaker and vice versa. If not using the active crossover, you do not swap leads.
 
Seems I'm a little late in finding this thread.
Being a 4.5 owner I'd like to mention something that I don't think has been mentioned. Please excuse me if I am mistaken. In the process of refoaming my woofers and wanting to use the shim method of alignment, I removed the dust caps to find four ~1/4" holes drilled through the cones. The dust caps were the vented cloth type so the enclosure is vented and not sealed. I emailed Bill Watkins and Orange County Speaker asking if this was normal. Bill said that Infinity did this to some of his woofers in certain models but not all. OCS said that most, if not all, the 4.5 woofers had holes. Of course I sealed the cabinet in a similar manner that is described here and I really enjoy my 4.5's.
 
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