ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi,
I have a pair of S120 speakers and just had them re foamed. I never had a chance to hear them play before I bought them. My question is, is there something wired incorrectly in the speakers because to get the proper sound stage I need to hook up one of the speakers with reverse polarity. I does not appear that these have been opened up before. I have been trying to do some reasearch and thought I found an old post that says the mid range speaker should be hooked up with reverse polarity???? Or could this have something to do with needing to have the crossovers recapped? This is something that I would like to do as well. Does anyone know where a good place is to get the caps?? thanks
Chuck
Martin is selling me some caps to re do the crossovers. thanks
Hi Chuck,
I have a pair of MC 120.2 speakers which are nearly identical to your speakers and purchased one of Martin’s capacitor kits, which are excellent. Martin definitely is the best source for re-capping.
I also had my speakers re-foamed, which is a good idea.
Martin might also have an answer to your question, as I do not. However I will say that I sincerely hope your experience with the S 120 speakers is different from mine as I found them to be anemic, colorless speakers….. a complete disappointment.
That said, it maybe that my amplifier is just not sufficiently powerful for these rather power hungry speakers.
In any case, I shall follow this thread with great interest. Best wishes!
Jeff
Beogram 4000, Beogram 4002, Beogram 4004, Beogram 8000, Beogram 8002, Beogram 1602. Beogram 4500 CD player, B&O CDX player, Beocord 4500, Beocord 5000 T4716, Beocord 5000 T4716, Beocord 5000 T4716, Beocord 8004, Beocord 9000, Beomaster 1000, Beomaster 1600, Beomaster 2400.2, Beomaster 2400.2, Beomaster 4400, Beomaster 4500, Beolab 5000, Beomaster 5000, BeoCenter 9000. BeoSound Century, S-45.2, S-45.2, S-75, S-75, M-75, M-100, MC 120.2 speakers; B&O Illuminated Sign (with crown & red logo). B&O grey & black Illuminated Sign, B&O black Plexiglas dealer sign, B&O ash tray, B&O (Orrefors) dealer award vase, B&O Beotime Clock. Navy blue B&O baseball cap, B&O T-shirt X2, B&O black ball point pen, B&O Retail Management Binder
Phase polarity issue can derive all the way back to lousy mp3 conversions, and also back to source recordings of music with lots of un-phase information when "what is phase" will become a subjetive question of what IS the right phase.
But a general advice is that if you sit in the middle of the two speakers you will have the best strong bass if your speakers are connected correctly to the amp.
In your case there are many "what ifs"
If connected through din-pluggs to a B&O amp the chance for wrong phase is slim to zero, then someone might have been messing with the internal wiring after the speaker left factory.
Phase polarity is generally only a bass problem as the acoustic wavelength of bass tones are physical long.
The acoustic wavelenght of high frequences are in cm to mm,so just moving your head while breathing will change polarity.I say this because , as long as your woofers are connected in phase you wont have a realistic problem. ( subjetive, my opinion, of what matters , some will disagree )
If you want to be dead end down to earth of exact configurations of your speakers you have to run many tests and check many things
But dont give up depending of what you want to achieve :) there are many talented people here to help.
Regarding midrange speaker, some speakers have midrange speakers connected with oposit polarity because of crossover design, not to worry about.
My re-capped M75 are my precious diamonds.
I have had these re foamed, and different binding posts put on the back that use banana plugs. I know the guy that did this for me is very particular about things and when I picked them up he was showing me that they were out of phase. With both wired correctly there was no stereo imaging, when the polarity on one was reversed, it was like a different set of speaker, beautiful stereo imaging and the sound was fantastic. At that point I decided that they were keepers. That is why I am going ahead with the recap. Hopefully they will be able to give me many hours of entertainment. Hopefully the cap kit arrives in the next couple of weeks, then change them and see what a difference it makes. I also found an app for my phone that will be able to test to see if the individual components of the speakers are in phase or not. will report back when I get this all done
The need for recap is only because old capacitors dries and then their values change.
That means that the crossovers all values, and design will drift in many directions.
In some cases the change is REALLY dramatic.
I recapped my beovox 1200 last month with cheapest avaliable capacitors.Did A-B test between the the re capped speaker and the one that wasnt re-capped and it was a completly new speaker. The change was REALLY dramatic.Clarity lived up , the treble speaker got a huge freshness, and the woofer got a stiff controlled bass compared to very muffled before..Well the beovox 1200 is very old, so the caps have had time to dry and dry and dry
perspective of stereo is unphase, the more unphase information the more subjective stereo.
Actually correct phase is when you experience the least stereo image.
Connecting you speakers unphase, your will experience loss of bass and a dramatic wideness of the stereo image.
But if you modify the amount of unphase information that the artist decided to have in the mix. that means that the music is not orginal anymore if you connect your speakers un-phase to widening the stereo image
Yes that is my thinking as well. These are an older speaker so a re cap should be in order for them to get the best sound out of them. I have did the re cap on a set of IMF TLS80's I have and the difference in sound from before to after was amazing. Hopefully the same will happen here.
With so much expertise here, I hope no one will mind me butting into someone else’s thread.
I have had my MC 120.2 speakers for several years. Initially they sounded OK, but recently became metallic and artificial in the upper range with absolutely no bass.
I had them re-foamed and installed one of Martin’s superb capacitor kits, which improved the upper end and added a bit of bass, but nothing remotely near what is expected.
These speakers performed well enough with a Beomaster 4500, so I am surprised that they are so anemic powered by a Beomaster 4400, which has a good deal more muscle than the 4500.
I am using DIN connectors so there is little chance they are out of phase.
I discussed this very subject in my own thread but with all this new input, I thought I’d give my situation another shot.
Any ideas?
I am courious to see what you find out on yours as well Jeff.
JeffAre you sure the woofers are working, are there sound from both of them .
Interior design has a dramatic effect on how bass reproduces in a home, any changes ?
Jeff,
Check that your woofers has been correctly phased after the refoam.
Martin
Christian,
Yes the woofers are working; there is sound and physical movement. However one of the differences between these MC 120.2 speakers and the S 75 speakers which are both connected to the same amp is the S 75’s move a LOT of air. Put your hand in front of the woofers and you feel the wind. With the MC 120.2 speakers there are whiffs of air and totally anemic bass.
Martin,
Here I go again showing my ignorance. I could have avoided this by sending you a private message, but thought maybe someone else didn’t know the answer and might learn from this, so how do I check for a speaker being out of phase?
If I was using standard exposed wire I would know to reverse the wires on one speaker and listen for a major bass improvement. However I am using DIN connectors. In addition much preferring the S 75 speakers to the MC 120.2 I swapped them, thus changing outputs from the amp as well as the wires, and the general anemic condition followed the MC 120.2’s….. so we can definitely rule out a connector or wire problem.
I suppose I could connect the MC 120.2 speakers to my McIntosh system as one of the curious benefits of the MI-3 Maximum Performance Indicator is when speakers are out of phase the video display reverses. However doing this is a lot more work than would seem apparent, so how would YOU determine if the MC 120.2 speakers are out of phase?
I suspect that Martin thinks the wires to just the woofer might be the wrong way round - you will need to take the baffle off the speaker to see this - quite easy - I did it when I replaced the woofers on my S120s and am useless mechanically!!
Peter
Hi Peter,
Well if you say it is easy, I believe you and that means I will be able to do this.
Martin gives me more credit than I am due when it comes to tackling the various issues that have plagued my B&O collection. I become extremely anxious when taking these amps apart, especially after opening up the BeoCenter 9000 and the two glass panels flew off, without warning, at the same time. That was a heart-stopper and it was a miracle (dumb luck, your choice) that I managed to catch both before they hit the floor.
Speakers are quite a bit easier so I’ll take a look this weekend and sans apprehension.
There just HAS to be something wrong as the way these MC 120.2 speakers perform no one, and I mean NO one would ever have purchased them new.
It is possible that while I fixed one issue by re-capping these speakers the shop that re-foamed them created a new problem with the wiring. Makes sense…. hope it turns out to be true.
Quick question, I am assuming that I am checking to see if the two speakers are wired the same, is that right?
I found this app that I was going to use to check the speaker polarity/phase
https://itunes.apple.com/ca/app/speaker-pop/id293263027?mt=8
give it a look and see what you think? It looks very user friendly
Peter: I suspect that Martin thinks the wires to just the woofer might be the wrong way round - you will need to take the baffle off the speaker to see this - quite easy - I did it when I replaced the woofers on my S120s and am useless mechanically!!
Peter,
I have had a bit of time to think about this and I am requesting a bit more information.
Taking the speaker apart is no problem, ditto removing the woofers….. I have had a good deal of practice in this area.
However after that I am in unknown territory, and as you know I don’t like surprises. As such could you please provide a “Checking woofer polarity for Dummies” type of instruction? I probably could figure this out on my own, but then maybe not.
Although it is comparing apples and oranges I recently replaced all the tiny and unusual lamps in my Tandberg 9000X deck. I was apprehensive and asked for instructions and thank God I did as I undoubtedly would have broken all the switches on the deck.
The plastics used by Tandberg are atrocious and are literally falling to pieces. The switches are hinged at the top and are released by putting pressure at the bottom of the switch. Not knowing this I am sure I would have tried to gently pry them up with a screwdriver which would have shattered the switches.
Lack of knowledge is always expensive. So how do I take off the baffle and what do I look for? If this is a stupid question, that’s alright, as I would rather ask then break something.
To check polarity: Connect a 1.5 V battery to the woofer, + to + and - to - , the woofer will pull inward, if + from battery is connected to - on woofer, the woofer will push outwards. Mark the + terminal, now check in the schematics which wire from the crossover is the positive, and you are good to go.
Collecting Vintage B&O is not a hobby, its a lifestyle.
I just had mine apart, and another quick question, on the top of the speaker, there is a small foam sealing strip, is this supposed to go all the way around the speaker or are they just sealing the top?
I´m not familiar with the 120, but if there are gaskets (sealing strips) they normally go all around the speaker.
Søren Mexico: To check polarity: Connect a 1.5 V battery to the woofer, + to + and - to - , the woofer will pull inward, if + from battery is connected to - on woofer, the woofer will push outwards. Mark the + terminal, now check in the schematics which wire from the crossover is the positive, and you are good to go.
You really SHOULD be able to HEAR out of phase woofers. Playing some music, pull your speakers together so that they're a few inches apart, and face to face. The woofers are now playing right at each other.
Listen for awhile at a decent level. Not too loudly; say, at a normal "conversation level" (80 dB or so?). Let's call this Listening Condition A.
Now take ONE of the speakers and switch polarity of the speaker cable at ONE end. With DIN connections at BOTH ends this isn't possible. (Yet another reason why I don't like DIN connections at the speaker.)
Now listen again at the same level. Let's call this LIstening Condition B.
You now have listened to the woofers both in phase and out of phase. The Listening Condition which provided the most bass is when the woofers were in phase. When they were out of phase, much of the bass content would have been cancelled by one woofer pushing while the other was pulling.
If your woofers were originally wired out of phase, Condition A would be the lesser bass content. If when you switched the polarity of the entire loudspeaker (Condition B) you then lost a lot of bass, the woofers are wired in phase.
Follow me?
To answer one of your earlier direct questions, Jeff: Yes - when you open them up you should just verify they are "wired the same."
Søren Mexico: I´m not familiar with the 120, but if there are gaskets (sealing strips) they normally go all around the speaker.
I have never encountered a speaker without gaskets, and all gaskets always went all the way around.
But I've only messed with a couple dozen pair, so my knowledge is certainly less than "Martin-like."
Jeff, there are several way a blown woofer can react. One is that they do sound, but you only hear a little sound from them , mostly mid, with aaalmost no bass.
I actually think there is a big risk you have blown woofers.
C
Christian Christensen: Jeff, there are several way a blown woofer can react. One is that they do sound, but you only hear a little sound from them , mostly mid, with aaalmost no bass. I actually think there is a big risk you have blown woofers. C
Hi Christian,
I am in no position to question your assessment; however I would have thought that a blown woofer was the result of over-powering them.
I can safely say that 7 years ago when I purchased them the woofers were not blown and as I was powering them with my now defunct Beomaster 4500, if anything it had too little muscle to power these speakers as opposed to too much.
While being rather technically-deficient I have never heard nor do I believe that too little power can damage a speaker.
Tomorrow I am going to check to see if these speakers were inadvertently wired backwards by my re-foam guy.
I will report what I find.
Dom
2x BeoSystem 3, BeoSystem 5000, BeoSystem 6500, 2x BeoMaster 7000, 2 pair of BeoLab Penta mk2, AV 7000, Beolab 4000, BeoSound 4000, Playmaker, BeoLab 2500, S-45, S-45.2, RL-140, CX-50, C-75, 3x CX-100, 3x MCL2 link rooms, 3x Beolab 2000, M3, P2, Earset, A8 earphones, A3, 2x 4001 relay, H3, H3 ANC, H6, 2014 Audi S5 with B&O sound, and ambio
I´ll keep my fingers crossed, Jeff :)
DMacri:You can damage speakers with a stereo with too little power when you drive the output into distortion to gain more volume than the little amp can provide. The resulting square wave output could be very damaging. It's easier to get that distortion with a little amp than with one with much more generous output capabilities. Typically, the damage it to the tweeters first, so I'm not saying that's what happened here, just pointing out that too little power kills too.
I was unaware of this, but as least I have learned something.
That said I very, very much would be surprised if my Beomaster 4500 would have been a good candidate to do damage to these woofers.
Whereas the 25 watts per channel is not sufficient to really properly drive the MC 120.2 speakers I doubt that it is so feeble as to damage them, especially considering the 4500 has protection to prevent it from being over-driven….. serves as protection for the speakers as well.
Next thing on my agenda, take these speakers apart and see what gives….
Christian Christensen: I´ll keep my fingers crossed, Jeff :)
Why thank you kind sir! Much appreciated
Søren,
All wiring is correct. Positive test works as described, how about I try testing to see if the main wires, yellow and grey are backwards? Would this hurt anything?
Which is positive and negative, see arrows.
Thank you.
Black, blue and white are negative (upper left arrow). Gray (lower right) negative, goes to spade terminal, Brown (lower right) positive goes to round pin,
This according to schematic for crossover for S120 on site.
Søren Mexico: Black, blue and white are negative (upper left arrow). Gray (lower right) negative, goes to spade terminal, Brown (lower right) positive goes to round pin, This according to schematic for crossover for S120 on site.
The black, blue and white get the grey connecting wire. The other connection gets the yellow wire.
I opened up the MC 120.2 speakers and all appeared to be correct. The connections on the woofer, red and black were the same on both speakers, plus there is a red dot besides the one connection indicating it is to have a red wire.
It then occurred to me that I may have gotten the two main connections reversed, yellow and grey so I reversed them deliberately to see what difference it would make.
The answer is very little, possibly a little bit worse, but nothing dramatic.
So I put things back the way they were for a really good listen.
Trying to be as objective as a scientist neither speaker sounds especially good. The left speaker has a bit more bass, and I should add that there IS bass, but I was playing a particularly boomy record.
With my amp playing a just shy of clipping I was physically able to put my ear to the woofer which didn’t impress. Needless to say it would have been painful to try this with the S 75’s.
Then I turned the volume down and turned on the S 75’s which play at a considerable higher volume being vastly more efficient than the MC 120.2’s. However even with reduced volume the S 75’s produce the boomy sound from the recording.
In all candor the record is poorly made with way too much electronic alteration to make a hard judgment, but that said it sounds reasonably good on the S 75’s, not so on the MC 120.2’s.
At this point I don’t see what else there is to do, I think the “fat lady has sang,” and she didn’t sound too good on the MC 120.2’s.
In short my MC 120.2’s are very close to worthless in my view, but do add a bit of zest when playing with the S 75’s.
I’d sell them on eBay, but how could I honorably describe them, “Attractive and in pristine cosmetic condition Bang and Olufsen MC 120.2 speakers suitable for producing elevator music,” and expect them to sell?
So guys, it was a great effort and I thank everyone for your advice and assistance. You win some and lose some, unfortunately this is the latter.
If grey goes to spade terminal, thats OK, I dont see any yellow wire, the brown wire in your pic is positive, to round pin terminal
I have been listening to mine for a bit now and the bass is improving after the re foam, looks like it takes a bit of time for things to work themselves in. I think I have about 8 hours on them now. The sound is continually getting better. I can start to tell now that they are definately in need of a re cap(which are on order). Also trying to find some sealing foam to put around the plastic cover that the speakers go in. I think that will make a difference in the bass as well. Looks like these will be a nice set of speakers with a little more work,
Jeff, are you sure the crossover has gotten recapped, to me it looks original, there are foam rests on the caps, with new caps there should not be.
I have no experience with the 120th but the crossover looks untouched to me.
CBN700 can you post a pic from your crossover(s)
I will try but will not be for a day or two until I get home
Søren Mexico: Jeff, are you sure the crossover has gotten recapped, to me it looks original, there are foam rests on the caps, with new caps there should not be. I have no experience with the 120th but the crossover looks untouched to me.
You have a keen eye indeed! I am sincerely impressed. The photo is an old photo before I re-capped and one that I had conveniently on file.