Keep Blowing Center (HTM) Tweeter

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  • CFoote
    Junior Member
    • Dec 2010
    • 7

    Keep Blowing Center (HTM) Tweeter

    Hello Everyone,

    I am new to the forum but not to B&W speakers My first set of B&Ws was a set of CDM1's, and then I upgraded to a pair of Matrix 802 S3s, and now I have a set of N802's which I've had for ~7 years.

    A few years ago I purchased a HTM3S as I purchased my N802s used and never found a used center channel. The HTM3S is a great center speaker for use with the N802s, however I keep blowing the tweeter. For example, tonight I was giving a demo to a friend and we were watching Avatar -- granted I had the volume up (not ear piercing loud, but it was up there) and the tweeter in the HTM3S blew. I could tell because the tweeter housing was hot and I've had this happen twice before...of course there no sound too :B This is the third time it's happened!

    I know, I know....turn the volume down. However, the N802 tweeters are just fine. I realize the parts are physically different, but is the tweeter really that bad on the HTM3S?

    My question is this: Is it possible to replace the tweeter (which I understand just screws out of its housing) with a HTM1 tweeter, or better yet, a N802 tweeter? I'm trying to figure out what the scoop is here. If heat is an issue, would an aluminum enclosure from a higher model Nautilus speaker help?

    I'm at a losss...the tweeters are not too expensive at $120 U.S., but if I can prevent this from happening in the future that would be nice.

    Thanks for listening and your help.

    Chris
  • beden1
    Super Senior Member
    • Oct 2006
    • 1676

    #2
    Originally posted by CFoote
    Hello Everyone,

    I am new to the forum but not to B&W speakers My first set of B&Ws was a set of CDM1's, and then I upgraded to a pair of Matrix 802 S3s, and now I have a set of N802's which I've had for ~7 years.

    A few years ago I purchased a HTM3S as I purchased my N802s used and never found a used center channel. The HTM3S is a great center speaker for use with the N802s, however I keep blowing the tweeter. For example, tonight I was giving a demo to a friend and we were watching Avatar -- granted I had the volume up (not ear piercing loud, but it was up there) and the tweeter in the HTM3S blew. I could tell because the tweeter housing was hot and I've had this happen twice before...of course there no sound too :B This is the third time it's happened!

    I know, I know....turn the volume down. However, the N802 tweeters are just fine. I realize the parts are physically different, but is the tweeter really that bad on the HTM3S?

    My question is this: Is it possible to replace the tweeter (which I understand just screws out of its housing) with a HTM1 tweeter, or better yet, a N802 tweeter? I'm trying to figure out what the scoop is here. If heat is an issue, would an aluminum enclosure from a higher model Nautilus speaker help?

    I'm at a losss...the tweeters are not too expensive at $120 U.S., but if I can prevent this from happening in the future that would be nice.

    Thanks for listening and your help.

    Chris
    What amp/power is driving the center speaker? I think something else is going on here as I have a hard time understanding why just your center speaker tweeter is failing? Have you checked your wiring, as in are the wires crossed causing an out-of-phase condition, or, is the plus wire also touching the negative wire terminal, etc.?

    Comment

    • CFoote
      Junior Member
      • Dec 2010
      • 7

      #3
      Thanks for your response. I have a Krell HTS 7.1 for a processor; the amplifiers are KAV-250a/d (250w/channel). The only thing I can think of is that the center channel output was bumped up by +2db on the processor compared to the N802's. I know people always mention lowering other speakers to compensate for the less sensitive speaker, maybe I should do that?

      I have a strong feeling its clipping, but don't todays processors prevent that from happening? Maybe I am wrong and they do not

      Thanks for your time.

      Chris

      Comment

      • Glen B
        Super Senior Member
        • Jul 2004
        • 1106

        #4
        Clipping is caused by driving the amp beyond its limits, plain and simple. Your processor will not prevent that from happening. You're probably either clipping the amp or just driving the center too hard (too much high frequency content) and burning out the delicate tweeter voice coil. In my experience, I find the center channel and sub do most of the work. With that in mind, your N802 tweeters would be fine because they are working only part of the time, whereas the center channel tweeter is being worked harder, and experiencing greater stress.

        Some speaker manufacturers use polyswitch resettable fuses in series with their tweeters, to protect them from overload. The polyswitch opens in response to excessive voltage, current and heat. You could try putting one in series with your tweeter after you get a replacement. They come in different ratings. Following is a link to one you can try, available at Allied Electronics. It should handle at least 40W, which should give you some safety margin. If you find that you get a lot of nuisance tripping, you could try a slightly higher rating.

        Last edited by Glen B; 10 December 2010, 14:01 Friday.


        Comment

        • bnieman
          Senior Member
          • Jun 2006
          • 202

          #5
          How big is your room? In a moderately sized room I would think it would be tough to blow a tweeter in the HTM3s before you blow your ears.
          Guide: Ripping DVD-Audio Discs (DVD-A) to FLAC in Windows

          Comment

          • dan87951
            Senior Member
            • Nov 2005
            • 379

            #6
            Wow, are you serious? The HTM3s can handle some serious power for a center. I'm with the other listeners your amp has gotta be clipping. Can you still hear though?
            dan87951
            audio guru

            Comment

            • Canuck525
              Member
              • Sep 2010
              • 31

              #7
              I have never blown a tweeter in the 20+ years of being an audiophile. Something is wrong with either the processor or amp which is causing clipping.
              Go out and pick up a high powered receiver just to try it. I'll bet you won't blow any more tweeters...

              Comment

              • emig5m
                Senior Member
                • Aug 2008
                • 646

                #8
                Originally posted by Canuck525
                I have never blown a tweeter in the 20+ years of being an audiophile. Something is wrong with either the processor or amp which is causing clipping.
                Go out and pick up a high powered receiver just to try it. I'll bet you won't blow any more tweeters...
                My same thoughts...

                Comment

                • CFoote
                  Junior Member
                  • Dec 2010
                  • 7

                  #9
                  Originally posted by Glen B
                  Clipping is caused by driving the amp beyond its limits, plain and simple. Your processor will not prevent that from happening. You're probably either clipping the amp or just driving the center too hard (too much high frequency content) and burning out the delicate tweeter voice coil. In my experience, I find the center channel and sub do most of the work. With that in mind, your N802 tweeters would be fine because they are working only part of the time, whereas the center channel tweeter is being worked harder, and experiencing greater stress.

                  Some speaker manufacturers use polyswitch resettable fuses in series with their tweeters, to protect them from overload. The polyswitch opens in response to excessive voltage, current and heat. You could try putting one in series with your tweeter after you get a replacement. They come in different ratings. Following is a link to one you can try, available at Allied Electronics. It should handle at least 40W, which should give you some safety margin. If you find that you get a lot of nuisance tripping, you could try a slightly higher rating.

                  http://www.alliedelec.com/search/pro...px?SKU=4200055
                  Thanks for your response Glen. I too am baffled by the whole situation. The fuse sounds like a great idea to start with.

                  Chris

                  Comment

                  • CFoote
                    Junior Member
                    • Dec 2010
                    • 7

                    #10
                    Originally posted by bnieman
                    How big is your room? In a moderately sized room I would think it would be tough to blow a tweeter in the HTM3s before you blow your ears.
                    I totally agree! This is very, very baffling. The few times the tweeter blew the SPL (A weighted) has been up around 95-100db; yes this is loud (and trust me, I don't listen at these volumes for any longer than a few minutes!) and was only done to demonstrate the system to a friend.

                    Room size is difficult to talk about, because I'm in a raised ranch, so the Family Room and dining room are a shared space (like an L), and the entryway/foyer is wide open too. If you are talking about just the family/living room, it's 20 X 12... but wide open, it's 26 X 24.

                    Chris
                    Attached Files

                    Comment

                    • CFoote
                      Junior Member
                      • Dec 2010
                      • 7

                      #11
                      Originally posted by dan87951
                      Wow, are you serious? The HTM3s can handle some serious power for a center. I'm with the other listeners your amp has gotta be clipping. Can you still hear though?
                      :B Yes I can hear fine, this happened with the volume somewhere up around 95-100db peak volume. Yes, loud, and no, we definitely didn't keep it there for more than 3-4 mins.

                      Something has to be going on. I'm tempted to swap channels on the amp and see whats going on. I just checked the processor and my fronts are -7 and -6 for output, and the center is -1 (that's trying to attain a 75db output, A weighted, per Krells manual).

                      Strange indeed...

                      Chris

                      Comment

                      • CFoote
                        Junior Member
                        • Dec 2010
                        • 7

                        #12
                        Originally posted by emig5m
                        My same thoughts...
                        Sadly I think you're both right. Chasing this down will be difficult and expensive.

                        Chris

                        Comment

                        • CFoote
                          Junior Member
                          • Dec 2010
                          • 7

                          #13
                          Hi Everyone,

                          So I just did a little bit of testing in Avatar and remembered where the tweeter blew.

                          In 1hr 9mins 36 secs into the movie, Jake is screaming at a dragon, and the dragon hisses back. There is so much high frequency information that my meter went well over 100db. Average listening volume in the movie is 75-80db, there are so many fighting and quiet scenes it's tough to judge.

                          As I mentioned above, I checked my output levels in the processor, and all are beow 0db; Left is -6, Center is -1, Right is -6, surrounds are -4 and -5...sub is -3.

                          Comment

                          • Antus
                            Senior Member
                            • Apr 2008
                            • 141

                            #14
                            by the information you provide, i can come up with few things you can look into.

                            1. what pre/pro and amp are you using? many home theater pre/pro can only output 1V to 1.5V in the pre amp section. when you mate that with a regular 2 channel amp. which normally require 2V or 4V to output at full power. by turning the volume way up will cause pre amp clipping. (instead of power amp clipping)
                            2. since you are buying the center channel used, the crossover within the speaker may be defective. to be more specific, the capacitors (high -pass) tweeter network may not working as designed.

                            one way to find out is to connect one of your 802 as center channel. and use the HTM as right or left channel and see how it goes.

                            Comment

                            • azazel
                              Member
                              • Dec 2010
                              • 31

                              #15
                              There is a problem with early nautilus tweeters where the foam surround that holds the dome/ voice coil assembly in place comes unstuck. It is only held in place with a self adhesive material. When it comes unstuck, the voice coil comes out of the gap in the magnet. This means it is not being cooled by the ferrofluid and leads to overheating failure. I would think that its output would be reduced as less coil is in the gap intereacting with the magnetic field which would mean the user is moor likely to turn up the volume causing more heating and result in failure. The foam surround was the same diameter as the outer bevel apperture on the older models but B&W have since modified it so that the foam is larger and held in place by the outer casing.

                              Comment

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