Tri Amping RS 4.5s

[goat67]

Looking for your input on Tri Amping my RS 4.5s all input welcome

The Passive crossover I have is a very early model Pre rev A believe it or not.
I do not have the original equalizer that was available so I am using the equalizer from my RS IIbs. So I was thinking of rebuilding the passive crossover up to the final rev and buying a active crossover more suitable.

Well that would mean no tunes while I did that so I was wondering why not just remove the Passive all together and Tri Amp them. I have another Souncraftsmen amp so I would have 3 identical amps and they all have gain controls If I need them but I think the active would take care of this at any rate.

In another thread I seen a pair that was sold on the bay that was built from Infinity for Tri Amping the EMITs and EMINS where centered in the cabinet instead of mirrored anyway it said the EMITs and EMINS where configured for 1 ohm loads wired in parallel

Question why not wire the EMITs and EMINS in a parallel series configurations for a 3.5 ohm Load for each?

The woofers where wired as such that the dual voice coils 2 and 4 ohms in each driver wired in series for a total 6 and then in parallel with other driver for a 3 ohm total.

This would allow for an easy load for the amps on all three of the drivers loads

So recomendations on a active crossover like to not spend more on this than I did on the speakers as I may not keep this configuration.

Concerns?

Suggestions?

Thanks Jerry

 

[goat67]

What you all have no comments?

 

[Charivari]

What you all have no comments?

I wanted to post earlier, but I try to ration my thoughts and opinions to keep too many people from getting cranky.

I think it's a fine thought to go partially active, triamping the 4.5s while retaining the passive Watkins circuit sans the smaller low pass inductor for the woofers. You might want to ask Michael (MagicMarksy) for his thoughts on it as he has experimented with converting RS-Ibs into fully-active line arrays. He has already posted some on it in the QRS sticky (towards the end) and the issues of mismatched levels with the EMIMs.

As to a recommendation for an affordable crossover, might I suggest the Behringer DCX2496? It has quite the following amongst DIY circles and being that it does its thing in the digital domain, it avoids phase shift issues found in typical electronic crossovers.

Going active is supposed to be a significant improvement in the sound of any speaker and nets an effective 6dB gain in sensitivy in addition to the amplifiers' sum power. Someday, I'd like to try it as well.

- JP

 

[goat67]

I wanted to post earlier, but I try to ration my thoughts and opinions to keep too many people from getting cranky.

I think it's a fine thought to go partially active, triamping the 4.5s while retaining the passive Watkins circuit sans the smaller low pass inductor for the woofers. You might want to ask Michael (MagicMarksy) for his thoughts on it as he has experimented with converting RS-Ibs into fully-active line arrays. He has already posted some on it in the QRS sticky (towards the end) and the issues of mismatched levels with the EMIMs.

As to a recommendation for an affordable crossover, might I suggest the Behringer DCX2496? It has quite the following amongst DIY circles and being that it does its thing in the digital domain, it avoids phase shift issues found in typical electronic crossovers.

Going active is supposed to be a significant improvement in the sound of any speaker and nets an effective 6dB gain in sensitivy in addition to the amplifiers' sum power. Someday, I'd like to try it as well.

- JP

Thanks for the post

You said

I think it's a fine thought to go partially active, triamping the 4.5s while retaining the passive Watkins circuit sans the smaller low pass inductor for the woofers.

What do you mean by this.

"retaining the passive Watkins circuit sans the smaller low pass inductor for the woofers."

Can you expand on this thought regarding sans the smaller low pass inductor
what would the circuit look like?

On the active Xover I weas also looking at the Behringer

Come on tell me what you think about running the EMITS and EMINs in the paraell series config seems to make since on the surface

Keep the comments coming

 

[Charivari]

"retaining the passive Watkins circuit sans the smaller low pass inductor for the woofers."

Can you expand on this thought regarding sans the smaller low pass inductor
what would the circuit look like?

Oh, I was thinking about pulling the 12mH inductor from the woofers that determines the 150Hz XO point for the transition from the cones to the planars while leaving the rest of the passive components that enact the Watkins principle in place. Unfortunately, I had forgotten that the 4.5s have a switch for compatibility with the electronic crossover. Looking at the schematic, it would appear that the switch does not remove the passive components, but rather alters their value to push the low pass filter much higher and moving the high pass much lower. This would seem to be to avoid overlapping the passive slopes with the active slopes while maintaining the goof factor protection of the passive parts.

So, for what it's worth, I'd think that you can leave the inductor in there and use the switch for playing around with it. If you decide that you really like what's happening by going active, then it's a simple matter to pull the inductor later.

As to connecting two EMIMs in serial twice over and then those two sets in parallel, I can't offer up more than a guess as I've not had a chance to play with any EMIMs yet. Personally, I think it would work just fine thanks to these drivers being nearly purely resistive and those avoiding issues of inductance and the like. However, there are those with experience with these drivers who note that they do seem to not be all that consistent in levels and that it may not work too well.

There's no harm in trying and determining if you like the result or not,

- JP

 

[goat67]

Thaks for the input.
On the Woofers what about not using any of the passive Xover?
Also what about running the woofers as I described? To bad the person who bought the Tri Amped version of the 4.5s is not a member he could tell us how Infinity did it

 

[Kencat]

Thaks for the input.
On the Woofers what about not using any of the passive Xover?
Also what about running the woofers as I described? To bad the person who bought the Tri Amped version of the 4.5s is not a member he could tell us how Infinity did it

goat67, I was thinking you were a bit crazy for a while wanting to mess with the 4.5's, but I finally came across the post that must have started all this.

Per this post by Vito http://www.audiokarma.org/forums/showpost.php?p=1010065&postcount=31
he talked to the dude so maybe he can hook you up with him?????

It sounds like in Vito's description

He says that they are a tri-amp variation that have no crossovers and all of the Emims are in parallel for 1 ohm load and same with the Emits. The 2 voice coils on the woofers are in series and then paralleled with the other woofer for a 3.5 ohm load.

that there are NO crossovers, and putting the two voice coils in series would totally blow away the design intent of the Watkins principles to wipe out the impedence spike, but maybe they found a way to work with the impedence spike in some other way (cab tuning?). Putting the VC's in series and wiring the two woofers in parallel is a total reversal of the current design with passives, so this oddball design may indeed be "passive free" even on the woofers.

Sure sounds interesting :yes:

 

[Charivari]

Thaks for the input.
On the Woofers what about not using any of the passive Xover?
Also what about running the woofers as I described? To bad the person who bought the Tri Amped version of the 4.5s is not a member he could tell us how Infinity did it

As Kencat noted, you would lose the Watkins principle, which is the strength of the woofers or you would need to simulate it with the active crossover. For that, you would need a four-way stereo crossover and the Behringer (last I checked) only does three-way in stereo mode. So, you would need two running in four-way mono to do that. Then, you'd still need to reverse engineer the existing passive crossover and figure out at what frequencies the VCs are switching in and out. Even then, it'd be somewhat rough as you'd have to rely on the DCR rather than the actual impedance unless you've the Watkins white paper and found an impedance chart for the 12" Watkins woofer (something I've not seen) to figure out what each VC is doing at what frequency.

Is it a good idea? Absolutely, I've wanted to try the same. Trouble is trying to figure out how to configure the crossover to handle the Watkins properly.

- JP

 

[goat67]

You guys nailed it on the woofers Vito has the White paper And man I would love to get to read it. The Watkins dual voice coils and its Xover are sure hard to understand. I found it interesting that that thread said the dual voice cols were ran series and then in parallel with the 2 drivers.

I also thought of using a 4 way on this and use the other amp so I would have 2 amps for the woofers but as you said what freq to cut over at?

Well it sounds like it could be done but I do not want to fry anything. Maybe Vito can come thru on the white paper

At a min I think keeping the passive for the woofers and none for mids and tweets would work.

Thanks for all the input

Jerry

 

[phaedrus]

Goat67,

I believe the fellow who bought the tri-amped 4.5s sometimes posts on the Infinity Classics message board (Infinity Classics Forum) under the user name tinkeringjay.

You might drop him a line and see what he can tell you about them. Jay's a nice guy and very helpful.

David

 

[Kencat]

Goat67,

I believe the fellow who bought the tri-amped 4.5s sometimes posts on the Infinity Classics message board (Infinity Classics Forum) under the user name tinkeringjay.

You might drop him a line and see what he can tell you about them. Jay's a nice guy and very helpful.

David

It's a small community ain't it?

goat67,

Sounds worth trying to get in touch with this guy. Avoid all the guess work and get the facts. Especially if you're serious about trying this out :yes:

 

[goat67]

Goat67,

I believe the fellow who bought the tri-amped 4.5s sometimes posts on the Infinity Classics message board (Infinity Classics Forum) under the user name tinkeringjay.

You might drop him a line and see what he can tell you about them. Jay's a nice guy and very helpful.

David

Update

I have got in contact with him and the update is this yes they where TRI Amped no crossover at all but he never listened to them they and another pair of 4.5s and a pair of 2.5s have been parted out.
Image of the bare cases

The interesting thing is the top panel bafle it looks like the EMITS where set up to be open in the back. allowing for a true Dipole configuration on the EMITS if you used the mod mentioned by Mark here this could be something also look at the use of foam on the rear of the bafle. So 2 more pairs of RS4.5s accounted for

So I think I will go with an active passover for mids and tweets and use the passive in the woofers

I still am not done evaluating the existing crossovers I have found out some interesting things on the LCR circuits used in the woofers. Regarding Impedance and what the BandPass was designed for.

Does anybody have specs on the watkins regarding Freq response V impedance this would go along way understanding these circuits

 

[phaedrus]

Goat67,

Ouch! That's really disappointing, Jay had said he wasn't going to part those out. Real shame to see a unique pair that like that bite the dust.

Regarding the EMITs, if you look at the picture of the baffle it looks like only the EMIMs are open to the back, there are just slits in the foam behind the EMITs for the wiring.

I am still not convinced on the whole "dipole EMIT" thing; I find it difficult to imagine Nudell & Crew hadn't thought of it anytime in the 20 year lifetime of the EMIT. They clearly had the ability to make them dipoles if they chose to, and certainly had plenty of experience with dipoles. I suspect they deliberately chose to make it directional and we just don't know what their rationale was.

David

 

[Kencat]

Man......I don't think Jay is a very nice guy now Hope he doesn't get any more Infinities.

Whoever got those series connected VC Watkins woofers will or has been in for a nasty ride if he put them into a regular circuit without knowing how to undo whatever mod was done.

Some real valuable information has been lost. Really too bad.

For those who have talked to Jay, was this an Infinity modification, or a DIY job done by someone else?

 

[phaedrus]

For those who have talked to Jay, was this an Infinity modification, or a DIY job done by someone else?

Kencat,

My understanding was they were one of Infinity's custom jobs. Really annoying to see them die like that.

David

 

[goat67]

I to was disapointed but you know as he said in an email who knows how many other infinitys where saved by being able to buy spare parts think about it

18 EMIMs
18 EMITS
10 Watkins Woofers
= $4000.00 He used to buy some other speakers.

He still has the cabinets so even this hybrid is not lost until the cabinets are destroyed

On the EMITS in this hybrid I did not say they where true Dipoles I said they could be if the mod Mark mentioned was used as it is open in the back.
If mine where open to the back it could be tried without permanent modifications

Also check out the foam that is used all over the top bafle

 

[Charivari]

I to was disapointed but you know as he said in an email who knows how many other infinitys where saved by being able to buy spare parts think about it

Heard that one before, too many times. Unfortunately, everything in these speakers can be repaired or rebuilt without the need to sacrifice other speakers for parts. Even then, smaller, more common units should fall under the knife, not the 4.5s.

He still has the cabinets so even this hybrid is not lost until the cabinets are destroyed

Maybe someone with a ratty pair of 4.5s should pick those up before he decides to part them out for firewood and comes up with an excuse for that.

- JP

 

[Kencat]

Goat67,

This guy was contacted by some folks here who believed him when he said he would not part them out. He's a lier. He could have offered them for sale whole, knowing these were very rare, especially after being approached in fear of them being parted out. Someone here would of scooped them (I hope), and if not, then they could have been rightfully stripped.

The leftover cabs will reveal no clues about what was done to the Watkins woofers, or details of the Emit/Emim wiring, and as said before, there are no crossover circuits to look at.



Nope, no defense. Makes me

 

[Infinutty]

Greetings all! This is Jay, the apparently notorious Infinity dismantler. I became an audiophile around 1990 when a friend introduced me to the Infinity RSIIIa. It was the first time I listened to music without tone controls and I discovered that with the right speaker, flat was great and indeed correct. I had never heard a soundstage before and became mesmorized by the layers of instruments in symphonic music and imaging in really any style of music. From there I discovered the RSII a year later and fell big time for dipole sound, placing the RSIIIa's with a friend where they worked their magic. Next was the IRS Delta (just passive crossover) and the sheer clarity and bass it offered. Then I discovered the RS4.5 and it slaughtered the Delta in every way and I soon realized all the compromises in that attractive speaker and how it may have been more a marketing ploy than a true advancement in sound. I traded the Deltas for RS1b's as I was now addicted to multiple Emims. However, it showed me a flaw in the RS4.5 that always bugged me which was vague imaging and I came to see that the bowed design for the Emims was exaggerating the soundstage size. As my foam fronts were rotting anyway, I set the speakers aside for some rebuilding and played the RS1b's until it seemed most of my Emims were slapping and drifting soundwise all over the road. When I joined eBay and discovered the feeding frenzy buyers had on old Emims, I cut and ran thinking there was no affordable rebuild for them and that I could modernize with other ribbon mids. But there may not really be anything quite like the Emim even with all the materials science advances. No other design leaves so much open space for the sound to emerge from and so comb filtering seems to plague these newer types. So, here I sit having disabled some of the truly great speakers ever. I must make time to at least put together a workable trial with that one of a kind RS4.5 variant. But as you can see, I am not the type that preserves originals. Life to me is about pushing forward on the shoulders of those that paved the way. No museum pieces for me to set up an altar to. Sorry to send a chill through the air for some of you who really admire these classic designs. I do intend to enjoy them again, but I can't leave well enough alone! JAY

 

[goat67]

Welcome Jay to Audiokarma.
I see you got the email thing figured out to register