Does anyone know the efficiency ratings for the individual drivers on the RS 2.5's (EMIT, EMIM, Watkins woofers)? Also, anyone a guru on the crossovers on these things? Trying to figure out the schematic is driving me nuts...I can't even tell if the crossover is first or second order, because the ratings on the components don't seem to match either first or second, based on the crossover calculators that I find online. I'd love to tri-amp these things with an active crossover. Thanks!
RS 2.5 driver efficiencies
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AWESOME, rs1b, thanks! Looking at the schematic, it sure looked to me like a 12db/octave, but I keep reading about first order, and supposedly the electronic crossover/eq for these (which I do not have) mentions first order also. So, lots of confusion. I would like your opinion on whether or not to actively bi-amp or tri-amp these speakers. I would love to tri-amp, but then I obviously have to decide which passive components must stay. My thoughts would be only the 700uf cap and 20mh inductor on the 2 ohm coil for the Watkins woofer, but I'm not sure. Looking at the schematic, I have no idea what is what. For example, the 3.83uf cap and .20mh inductor aren't even close to what shows online for a 12db/octave crossover at 5000hz (more like 7.95uf and .13mh. So...lots I'd love to understand with these crossovers. I'd like to get the most that I can out of these speakers. All that I've done so far is replace the binding posts with high quality posts from Parts Express. That alone looks much nicer. Any help you can give would be great...I'd even be willing to talk on the phone about it. Thanks much!
rs1b
Member
Bi-amp is the way to go. Much less complex than tri-amping. And besides these were made to be bi-amped even if you can run them with a single amp. When you switch the bi-amp switch it allows he mids to work lower and the woofers to work higher thus when using your electronic cross over you won't end up with a big dip at your crossover point. Don't go much below 300 HZ as the Emim's can be easily overdriven. I use a 24 db at 280HZ and use a 24db at 225 HZ on my RS1B's. There are those who will argue they can go lower and they will (at lower volumes) if you want to push them a little higher is better.
Don't be in a big hurry to remove the crossover parts as you will find little improvement. I have modified many 4.5's and 2.5's over the years. Customer have had me rewire and upgrade the caps. For the cost there is small gain . Again there are many who will argue that and that is their choice. Especially after they spent vast amounts of cash. Your best bet for great sound with 2.5's is a good electronic crossover a 2 robust amps . The Watkins woofer love a good high current and stable amp, and so does the EMIM's as they dip below 2.5 ohms depending on where you have the variable resistor set. By the way the resistance on the EMIT's for crossover design purposes is about 1.8 ohm on the high setting and 2.8 on the low. Not amp friendly. The Emit's are around 3 ohms and are in parallel. There are 2 X .5 ohms resistors that are added in as you select the high to low setting. The schematic show 5 ohms. There should be a dot in front of the 5.
Don't be in a big hurry to remove the crossover parts as you will find little improvement. I have modified many 4.5's and 2.5's over the years. Customer have had me rewire and upgrade the caps. For the cost there is small gain . Again there are many who will argue that and that is their choice. Especially after they spent vast amounts of cash. Your best bet for great sound with 2.5's is a good electronic crossover a 2 robust amps . The Watkins woofer love a good high current and stable amp, and so does the EMIM's as they dip below 2.5 ohms depending on where you have the variable resistor set. By the way the resistance on the EMIT's for crossover design purposes is about 1.8 ohm on the high setting and 2.8 on the low. Not amp friendly. The Emit's are around 3 ohms and are in parallel. There are 2 X .5 ohms resistors that are added in as you select the high to low setting. The schematic show 5 ohms. There should be a dot in front of the 5.
Great information...it's very cool to have someone on the forum who has so much experience with these speakers! So, if I have understood correctly, you suggest to NOT worry about re-capping with better caps (i.e. poly), and as long as the current caps are working, let them be because the difference that I would notice would be negligible at best, correct? Also, a 2-way, 24db/octave active crossover to separate the Watkins woofer from the EMIMs/EMITs, and the switch in the bi-amp position. Yes, it will save lots of money going this way. Any suggestions for the 2-way crossover? The one thing that really annoys me with these speakers is the upper part of the speaker (foam surrounding the EMIMS and EMIT). It just isn't aesthetically pleasing...not like the winged design of the RS2b. If anything, I'd love to change that part of the speaker. I may also get the new black Watkins woofers from Bill Watkins, just because I think the looks would be great, but I'd also be assured that the sound from the woofers will be as good as possible. Lastly, do you have any thoughts on replacing the ribbons on the EMIMs with the new Graz (Apogee) ribbons that I've seen mentioned here on the forum. Thanks so much for your feedback and suggestions!
Oh...one further question for you, rsb1. Any idea why the woofers on the 2.5's are offset the way that they are, with the woofer offset to the OPPOSITE side of the cabinet as the EMIM/EMIT section? Also, it would appear that the EMIM/EMIT section is kind of a pseudo MTM setup, with the EMIT off to the side to allow the EMIMs to be closer together. I wonder also why the EMIT is not exactly in the middle of the EMIM array, and why the top EMIM is angled up, and the bottom EMIM is angled down. Guess I just like to know the reasoning behind the design...maybe for time-alignment purposes? Just wondering out loud if aligning the EMIM/EMIT with the woofer would make any imaging difference. I'm sure that you've probably taken many measurements with these speakers. Again, thanks so much for your experience and feedback!
rs1b
Member
If you can afford to do so the new Watkins woofer is a good improvement. Especially since they don't bottom out on really low bass passages due to his bumped back plate that allows greater excursion. they are also smoother with a little more mid bass so they work better with the Emim's than the older one. It is a different color though. As to the best crossover the Bryston is one of the best but be prepared to pay dearly for it.
As to the position of the woofer in the box. It was moved to the side to reduce standing waves in the box as per the original design. I have tried it in the centre in a hybrid model I made and noticed little difference. I upgraded my brothers 2.5's and used wonder caps and on a pair of 2b's we used solen's. We did one side at a time to compare and did blind curtain switching. Both sounded great, but so did the non modified version. For some people they just feel better doing it. Kinda like a K&N air filter on your car. Big expense and little difference. Put the money where is counts. If you still have some left over do the caps. I replaced the foam on mine. It needs to be there. Here is a picture on mine. And yes there is another tweeter. That is another story as if the mods to the mid crossover. I use Graz Emim's on my RS1B's . I'll talk about that later.
As to the position of the woofer in the box. It was moved to the side to reduce standing waves in the box as per the original design. I have tried it in the centre in a hybrid model I made and noticed little difference. I upgraded my brothers 2.5's and used wonder caps and on a pair of 2b's we used solen's. We did one side at a time to compare and did blind curtain switching. Both sounded great, but so did the non modified version. For some people they just feel better doing it. Kinda like a K&N air filter on your car. Big expense and little difference. Put the money where is counts. If you still have some left over do the caps. I replaced the foam on mine. It needs to be there. Here is a picture on mine. And yes there is another tweeter. That is another story as if the mods to the mid crossover. I use Graz Emim's on my RS1B's . I'll talk about that later.
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All great info, thanks again so much! I'll be looking forward to hearing what you have to say about the Graz EMIMs and the extra EMIT! I do understand about the foam being necessary, and I did find some that is as close to the original Infinity foam as I think could be found. I just think that the top half of the speaker is not nearly as appealing as the bottom half because of the foam and the lack of the gorgeous Infinity oak finish on the top half.
rs1b, I hope that you don't mind all the questions, but this is a great opportunity for me to understand these speakers, and I want to know all that I can about them, especially the crossover components. So, along with the above comments that you made regarding the Graz EMIMs, your extra tweeter and mid crossover mods, I also have the following questions:
1. You mentioned that bi-amping is the best way to go with these speakers, but could you expand on that? Why wouldn't tri-amping with a 3-way active crossover be better? I understand the extra cost of another stereo amp, but wouldn't it be possible to remove every passive crossover component, and the control module at the top of the speaker, EXCEPT for the 20mh inductor and 700uf capacitor on the 2 ohm coil of the Watkins woofer? I also realize that a person would also need speaker measurement software to set the individual speaker levels using the active crossover. So...is there a reason why some of the passive components on the EMIMs or EMITs need to remain, and can't be removed?
2. If it still is best to bi-amp, and I get a 2-way active crossover to split the Watkins woofer from the EMIMs/EMITs and set the switch to bi-amp, then which of the passive components WILL NOT be in use any more? Basically, if I choose to upgrade the caps, which ones would I not have to worry about?
3. If you're really feeling energetic and not tired of my questions yet, I'd love to know the reason for each inductor and capacitor value in the crossover (and the values). For example, I can see that the inductor and cap on the EMIT circuit looks like 2nd order 12db/octave slope, but the 3.83uf cap value and .2mh inductor value don't match what I see in crossover calculators for a 5,000 crossover. Why is that? Also, the EMIM circuit doesn't resemble a 12db/slope bandpass circuit.
Again, thanks so much. Let me know if you've had enough of my questions. Too bad I'm 3,000 miles away...I'd love to stop by and pick your brain.
1. You mentioned that bi-amping is the best way to go with these speakers, but could you expand on that? Why wouldn't tri-amping with a 3-way active crossover be better? I understand the extra cost of another stereo amp, but wouldn't it be possible to remove every passive crossover component, and the control module at the top of the speaker, EXCEPT for the 20mh inductor and 700uf capacitor on the 2 ohm coil of the Watkins woofer? I also realize that a person would also need speaker measurement software to set the individual speaker levels using the active crossover. So...is there a reason why some of the passive components on the EMIMs or EMITs need to remain, and can't be removed?
2. If it still is best to bi-amp, and I get a 2-way active crossover to split the Watkins woofer from the EMIMs/EMITs and set the switch to bi-amp, then which of the passive components WILL NOT be in use any more? Basically, if I choose to upgrade the caps, which ones would I not have to worry about?
3. If you're really feeling energetic and not tired of my questions yet, I'd love to know the reason for each inductor and capacitor value in the crossover (and the values). For example, I can see that the inductor and cap on the EMIT circuit looks like 2nd order 12db/octave slope, but the 3.83uf cap value and .2mh inductor value don't match what I see in crossover calculators for a 5,000 crossover. Why is that? Also, the EMIM circuit doesn't resemble a 12db/slope bandpass circuit.
Again, thanks so much. Let me know if you've had enough of my questions. Too bad I'm 3,000 miles away...I'd love to stop by and pick your brain.
rs1b
Member
Sure a 3 way electronic would be the best but it requires some knowledge before you tackle this. Not to mention much more money. You do not want to remove the caps . They will actually protect your speakers for DC . There are other posts on this topic . I will just say this, I did a mod on a set of 4.5's and was asked to bypass on passive components. I suggested not to do that but he insisted. A power outage followed by a power surge took out all 8 emims and all the emits. I have tried it both ways and the improvement is there but minimal. You do get more control over the drivers but they not longer sound as they were originally designed. Everyone wants to make something better and in the process can make it worse.
As far as when you switch to the bi-amp mode you do not actualy bypass anything.If you look at the drawing for the Emim's you actually add the 50uf and the 125uf together which makes it works lower. For the woofers it taps off part of the coil to a 2.5MH from a 5MH which allows it to work higher. I explained why in a previous post. Like I said before you can change all the caps if you want to that is up to you. If you do one do then do them all. Use similar voltage ratings.
The Emim does use a 6db to roll it off but a 12db on the front end. The Watkins portion of the circuit where the 700UF and 20MH coil is used is actually a tuned circuit that resonates at 40HZ. Which is also the resonant frequency of your box. I have posted detailed explanations of this on this website if you are interested. The 1100uf cap in the woofer circuit is a subsonic filter. Keep in mind these speakers were made when turntables were in. And feedback was a real problem for this speakers as they could get down into the subsonic region. In the bi-amp mode you add the 1100 and 700uf caps together which basically makes that filter to low to be of any use.
As to the Graz midrange. He did a great service to all Infinity owners who have emim's. he gave many old and dying emims a chance for a new life. Are they and improvement. Yes. Are they perfect . Well let's just say this the designers of the Emim's made a number of changes in the Emim later on. If you look at the white paper on the Epsilon's you can see where they laminated 2 pieces together. It really takes out the slightly aggressive nature the emim's can sometimes show. I can't speak for Graz but I don't think he set out to make the best mid range in the world. His goal if I read the post correctly was to offer a great replacement that offered nice improvements over the original. One great feature is they don't buzz. No need to add tape to the film. Great to have people like him around. But people complained about the price. You can't win. I personally say thanks to him.
As far as when you switch to the bi-amp mode you do not actualy bypass anything.If you look at the drawing for the Emim's you actually add the 50uf and the 125uf together which makes it works lower. For the woofers it taps off part of the coil to a 2.5MH from a 5MH which allows it to work higher. I explained why in a previous post. Like I said before you can change all the caps if you want to that is up to you. If you do one do then do them all. Use similar voltage ratings.
The Emim does use a 6db to roll it off but a 12db on the front end. The Watkins portion of the circuit where the 700UF and 20MH coil is used is actually a tuned circuit that resonates at 40HZ. Which is also the resonant frequency of your box. I have posted detailed explanations of this on this website if you are interested. The 1100uf cap in the woofer circuit is a subsonic filter. Keep in mind these speakers were made when turntables were in. And feedback was a real problem for this speakers as they could get down into the subsonic region. In the bi-amp mode you add the 1100 and 700uf caps together which basically makes that filter to low to be of any use.
As to the Graz midrange. He did a great service to all Infinity owners who have emim's. he gave many old and dying emims a chance for a new life. Are they and improvement. Yes. Are they perfect . Well let's just say this the designers of the Emim's made a number of changes in the Emim later on. If you look at the white paper on the Epsilon's you can see where they laminated 2 pieces together. It really takes out the slightly aggressive nature the emim's can sometimes show. I can't speak for Graz but I don't think he set out to make the best mid range in the world. His goal if I read the post correctly was to offer a great replacement that offered nice improvements over the original. One great feature is they don't buzz. No need to add tape to the film. Great to have people like him around. But people complained about the price. You can't win. I personally say thanks to him.
rsb1, great explanations, thank you! You do have me convinced to keep the passive components (possibly upgrading the caps), and looking for a 2-way active crossover to substitute for the optional Infinity unit (possibly a custom Marchand Electronics model). So then the question becomes, do I stay with the 6db/octave for the active crossover that is described in the Infinity literature for their crossover/eq module to keep the design as original as possible, or go to 24db/octave? It seems that if any caps could be removed, it would be the 700 and 1100 on the 4 ohm Watkins coil, even though it seems that keeping them there won't help or hinder. I plan on using only CDs as my source. And I would definitely be interested in reading the detailed explanations regarding the Watkins circuit (by the way, the 20mh and 700uf components on the 2 ohm coil are the ones that I did understand, for the resonance frequency). Oh...also...your reason for adding the second EMIT on your 2.5's? Thanks again!
rs1b
Member
Go with a non Infinity crossover. Unlike the RS1B and similar where they use a servo on the woofers the 2.5's and 4.5's do not. So use any good hi quality crossover.
The reason for the extra tweeter on the 2.5's was that I bought them new in 1980. When the RS2B's came out I really wanted them but could not afford them so I copied the tweeter design. I also did a mod on one of the Emim's crossover so it only goes up to 3000. Similar to the RS1B. I made at least 20 revisions and now have it where ( I ) like it. I do have all the equipment so i can play with it till the cows come home. Since then I have in my collection a pair of mint RS2B's, RS1B's restored to the original design before the Audio critics made infinity adjust the crossover on the tweeters to make them sound gritty. This is where you need to know how tuned circuits play havoc with your impedance curve in your crossovers. Most important I have a loving wife who shares my passion and let's me tinker. We worked together in a Hi end audio store in the late 70's and early 80's
The reason for the extra tweeter on the 2.5's was that I bought them new in 1980. When the RS2B's came out I really wanted them but could not afford them so I copied the tweeter design. I also did a mod on one of the Emim's crossover so it only goes up to 3000. Similar to the RS1B. I made at least 20 revisions and now have it where ( I ) like it. I do have all the equipment so i can play with it till the cows come home. Since then I have in my collection a pair of mint RS2B's, RS1B's restored to the original design before the Audio critics made infinity adjust the crossover on the tweeters to make them sound gritty. This is where you need to know how tuned circuits play havoc with your impedance curve in your crossovers. Most important I have a loving wife who shares my passion and let's me tinker. We worked together in a Hi end audio store in the late 70's and early 80's
Great stuff! I would LOVE to find a pair of the RS 2B's...I just love the looks of them as compared to the 2.5's. I swapped my RS IIIA's and some other stuff for the 2.5's. I'd really love to completely understand this crossover design so I can do my own tinkering. By the way, how do the dual woofers in the RS2B's compare to the Watkins woofer in the 2.5's?
rs1b
Member
The 2b's have a little more punch in the mid bass and will play a little louder.I personally prefer the 2.5's bass but there for sure is a gap transitioning from the Watkins 12" to the Emim's. They should have used a small mid bass driver from about 150HZ to 300HZ like they did with the QLS1's. Question is where to put it.
I did a 4 way version of the 2.5 for a customer. Removed one of the Emim's ( lower)and put in a Dynaudio 6" . Seamed a shame but he loved it and still has them to this day. The new Watkins woofer helps the mid bass so that would be money well spent.
I added a picture of my home theatre center channel that my son made for me out of solid oak as a project. Uses 2 x 6" mid bass drivers and 3 tweeters. 2 front one back. He placed the tweeters in their position so i won't comment on that except to say it makes a great center. The 2.5's are on either side.
I did a 4 way version of the 2.5 for a customer. Removed one of the Emim's ( lower)and put in a Dynaudio 6" . Seamed a shame but he loved it and still has them to this day. The new Watkins woofer helps the mid bass so that would be money well spent.
I added a picture of my home theatre center channel that my son made for me out of solid oak as a project. Uses 2 x 6" mid bass drivers and 3 tweeters. 2 front one back. He placed the tweeters in their position so i won't comment on that except to say it makes a great center. The 2.5's are on either side.
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Nice job by your son on the center channel! I actually thought about a 4-way version of the 2.5's using one of the EMIMs for the lower mid-range and the other for the upper mid-range. However, I'm not sure how low these EMIMs can safely go and still be musical. I also wondered what the early 90's High Energy EMIM and EMIT would do for the 2.5's, but then good luck finding those drivers from Renaissance speakers. Very nice for you that you already have all the required measurement software. All kinds of speaker measurement and crossover design software out there, but finding something reasonably priced that would do the job is another thing! The other thing I wonder about the 2.5's is that the tweeter sits up pretty high on these speakers...a good 6" or so higher than most people's ears would be when sitting...that just doesn't seem like the best design to me. Like you said...because of the woofer part of the cabinet being so high and not very deep, design changes are tough because the upper part of the cabinet is so small...and then you have the crossover components to deal with also. Maybe another good reason for an active crossover for these speakers. Lots of ideas in my head...just not sure what all I can do about it. Guess my programmer mentality! By the way, for purposes of calculating the passive crossover components, are all drivers rated at 4 ohms (other than the 2 ohm Watkins coil)? I imagine it isn't quite that simple. Oh...also...just for fun I downloaded the crossover schematic for the RSIIb's, and even though that's 5-way, the crossover looks much more straightforward than the 2.5 crossover.
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rs1b
Member
If you want to do it correctly forget the charts and programs. Do the math by hand. The charts are more guidlines than anything. You need to know what the impedance of the driver is and at what frequency. If you don't know that than you are throwing darts. All drivers impedance changes with frequency. However there is an exception to this rule. The Emit's and Emim's are purely resistive so they are more predictable. For example you can't say the Emim is 3.1 ohms and look at a chart. There are 2 of them in parallel which makes them a 1.5 ohm load. Added into to that is a .7 ohm resistor and a 1-4 ohm variable resistor.
If you want to really learn this get a program that can measure impedance throughout the audible range. You can even use it to make your own coils and test caps as to their true value.
If you want to really learn this get a program that can measure impedance throughout the audible range. You can even use it to make your own coils and test caps as to their true value.