hissing sound coming from behind woofer on one side AR11
in [Repair]
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From: Reverend Fuzzy on 20 Jul 2010 19:39 On Jul 20, 2:30 pm, Amanda Ripanykhazov <dmanzal...(a)googlemail.com> wrote: > Anyone know what this means? This hissing sound isnt constant, it is > irregular: It isnt related to the music or any movement of the cone > or any signal put through it, though it doesnt happen when no sound is > put through the speaker. > > Frankly it sounds more mechancial than electronic (as if there is > something behind there!) but as I say, it isnt related to whatever is > coming through the speaker though it does increase and decrease with > adjustment of the volume control. Andit is louder than most signals > put through the woofer itself?? > > Is it indicative of some pot in the crossover needing cleaning or is > there something else going on please? (I have seen reference to people > improving the sound of AR11s by bypassing the tone controls in the > speaker completely). This speaker is quite elderly and I would > imagine that if it does use mechanical pots, they must be fairly dirty > by now If there is a cross-over board in the case, you may have an electrolytic capacitor going bad. When they over heat, they'll make those sort of noises.
From: Jim Adney on 20 Jul 2010 21:01 On Jul 20, 2:30 pm, Amanda Ripanykhazov <dmanzal...(a)googlemail.com> wrote: > Anyone know what this means? This hissing sound isnt constant, it is > irregular: It isnt related to the music or any movement of the cone > or any signal put through it, though it doesnt happen when no sound is > put through the speaker. > > Frankly it sounds more mechancial than electronic (as if there is > something behind there!) but as I say, it isnt related to whatever is > coming through the speaker though it does increase and decrease with > adjustment of the volume control. Andit is louder than most signals > put through the woofer itself?? My guess is that the suspension for the woofer cone has come unglued. This can allow the voice coil to rub on the magnet, which makes sounds that are mechanical and vary with volume. To check for this, you'll need to remove the grill cloth so you can get to the speakers. Gently press all five fingers of one hand against the woofer cone, next to the center dome. Push sideways on the cone; try several directions. It should not want to move. It may be useful to do this on both speaker (stereo, right?) so you can be sure of any differences. You may see that the "surround" has disintegrated. That would be an obvious flaw. There is also a lower support called a spider which centers the cone near its small end. If the spider has come unglued, it can be reglued while holding the cone centered. Older AR speakers used wirewound controls for the tone controls. These corrode and lose contact. The effect of this is to lose the midrange or tweeter completely. They can be disassembled and cleaned, but they don't tend to make extra noises. The capacitors in decent speaker crossovers are never electrolytics, so they don't generally deteriorate over time.
From: Phil Allison on 20 Jul 2010 21:41 "Jim Adney" You may see that the "surround" has disintegrated. ** Happens to ALL speakers made with foam surrounds - like the AR11. That would be an obvious flaw. ** Obvious only if you look, the OP must be blind. If the spider has come unglued, ** Very unlikely. Older AR speakers used wirewound controls for the tone controls. ** Not the AR 11 - it uses a switch. The capacitors in decent speaker crossovers are never electrolytics, ** Fraid that is just not true. Most famous brand name hi-fi speakers use bi-polar electros for the larger values at least. ..... Phil
From: William Sommerwerck on 21 Jul 2010 07:21 > The capacitors in decent speaker crossovers are never > electrolytics, so they don't generally deteriorate over time. Never? I haven't checked "decent" speakers lately, but the AR11 is from an era when non-polar electrolytics were commonly used. Even inexpensive Mylar caps cost more than electrolytics. The tendency toward two-way designs (the AR11 is three-way) has raised the crossover point to a frequency that makes the use of a film cap more-practical. But even "the" classic two-way speaker (The Advent Speaker) used an electrolytic. The DQ-10 was one of the first speakers to use film caps. The original version used mostly electrolytics; the changeover occurred several years into production. In exchange for loaning him a pair of Pearl mics, Jon sent me a box of cheap Mexican Mylar caps, and I repopulated the crossovers. I was in such a rush to get it all done, that I didn't leave one of my four DQ-10s unmodded, and wasn't able to make a valid comparison. I /was/ going to suggest a mechanical problem with the woofer or midrange, but the OP /specifically stated/ that the hissing sound had no relationship with what was playing, or how loud it was, or /any movement of the cone/.
From: Amanda Ripanykhazov on 21 Jul 2010 12:26
On Jul 20, 9:01 pm, Jim Adney <jad...(a)vwtype3.org> wrote: > On Jul 20, 2:30 pm, Amanda Ripanykhazov <dmanzal...(a)googlemail.com> > wrote: > > > Anyone know what this means? This hissing sound isnt constant, it is > > irregular: It isnt related to the music or any movement of the cone > > or any signal put through it, though it doesnt happen when no sound is > > put through the speaker. > > > Frankly it sounds more mechancial than electronic (as if there is > > something behind there!) but as I say, it isnt related to whatever is > > coming through the speaker though it does increase and decrease with > > adjustment of the volume control. Andit is louder than most signals > > put through the woofer itself?? > > My guess is that the suspension for the woofer cone has come unglued. > This can allow the voice coil to rub on the magnet, which makes sounds > that are mechanical and vary with volume. > > To check for this, you'll need to remove the grill cloth so you can > get to the speakers. Gently press all five fingers of one hand against > the woofer cone, next to the center dome. Push sideways on the cone; > try several directions. It should not want to move. It may be useful > to do this on both speaker (stereo, right?) so you can be sure of any > differences. > > You may see that the "surround" has disintegrated. That would be an > obvious flaw. There is also a lower support called a spider which > centers the cone near its small end. If the spider has come unglued, > it can be reglued while holding the cone centered. > > Older AR speakers used wirewound controls for the tone controls. These > corrode and lose contact. The effect of this is to lose the midrange > or tweeter completely. They can be disassembled and cleaned, but they > don't tend to make extra noises. The capacitors in decent speaker > crossovers are never electrolytics, so they don't generally > deteriorate over time. I dont know why but the first thing I tried was pushing the cone in to see if I could identify that rasping effect when a speaker has blown. Dont know why I did this as the speaker has obviously not blown (the bass is still quite good. And for some reason I have never understood, the surrounds in those old speakers aren't made of rubber which disintegrates so that isnt a problem) in that way but what I didnt try was to push eccentrically and see if there was any resistance. I suspect I am going to have to get them over to Miller Sound at some time to rebuild (along with a pair of AR3s I have which have badly corroded cross-overs) but what I was wondering was whether this sound was likely to make the speaker terminal. Incidentally the snake behind the woofer is the best description of what I can actually hear! (a snake with a volume control, that is) |