- speaker refoam - 14 Updates
- Lexicon PCM70 legacy digital effects unit ... - 2 Updates
- Tascam DR-05 ticking noises - 9 Updates
| John-Del <ohger1s@gmail.com>: Nov 13 11:06AM -0800 This is a favor for a friend of a friend. I've never done a refoam before but I realize it's not rocket science but there's probably a learning curve. I won't have the option of do a trial run. These drivers come out of a pair of Infinity Crescendos, and the plastic dust caps seem well bonded to the cone. I'd much prefer to shim the cone before bonding the foams, but I don't know if the dust caps can be removed somehow from the cones without damaging them. Any advice appreciated. |
| tabbypurr@gmail.com: Nov 13 11:25AM -0800 On Tuesday, 13 November 2018 19:06:15 UTC, John-Del wrote: > This is a favor for a friend of a friend. I've never done a refoam before but I realize it's not rocket science but there's probably a learning curve. I won't have the option of do a trial run. > These drivers come out of a pair of Infinity Crescendos, and the plastic dust caps seem well bonded to the cone. I'd much prefer to shim the cone before bonding the foams, but I don't know if the dust caps can be removed somehow from the cones without damaging them. > Any advice appreciated. shim it from behind the cone, using bent bits of card. NT |
| John-Del <ohger1s@gmail.com>: Nov 13 12:17PM -0800 > > Any advice appreciated. > shim it from behind the cone, using bent bits of card. > NT It's got a cloth barrier running from the basket to the back side of the cone. The VC is completely hidden. Too bad the dust caps weren't tacked down with hyde glue. |
| "pfjw@aol.com" <peterwieck33@gmail.com>: Nov 13 12:21PM -0800 On Tuesday, November 13, 2018 at 2:06:15 PM UTC-5, John-Del wrote: > Any advice appreciated. You will find that if you are exceedingly careful, and use a bit of high-tack contact cement to get things started to center the cone to the foam, that shimming will not be necessary. But, it will help to cure the finished job upside down so that the cone is floating just a bit. Peter Wieck Melrose Park, PA |
| tabbypurr@gmail.com: Nov 13 02:38PM -0800 On Tuesday, 13 November 2018 20:17:07 UTC, John-Del wrote: > > NT > It's got a cloth barrier running from the basket to the back side of the cone. The VC is completely hidden. > Too bad the dust caps weren't tacked down with hyde glue. cloth airfilter can be cut & replaced without affecting speaker operation. The voice coil is already centred by the spider anyway, so not convinced you need to shim it. NT |
| dplatt@coop.radagast.org (Dave Platt): Nov 13 03:14PM -0800 In article <9174cb59-61f8-44c4-9197-ae1c678a3598@googlegroups.com>, >cone. I'd much prefer to shim the cone before bonding the foams, but I don't know if the dust caps can be >removed somehow from the cones without damaging them. >Any advice appreciated. SpeakerWorks sells re-foaming kits for a lot of sizes (both foam, and rubber surrounds). There are at least three ways to make sure that the cone is centered, when you do the final glue-down of the surround: (1) Remove the dust cap, shim, and then re-glue the dust cap afterwards. Apparently the dust caps can usually be removed without too much damage by cutting them carefully near the base with a single-edged razor blade or a sharp box cutter or etc. One must be careful not to cut the voice coil, damage the voice coil former, or get debris into the gap between magnet and voice coil. Lots easier with a paper voice coil than with plastic, I don't doubt! The instructions which SpeakerWorks provides with their re-foaming show how to do this, but it is _not_ their recommended approach. (2) Do it "unassisted". SpeakerWorks shows a procedure where you press gently down on the dust cap, and carefully manipulate the dust cap and cone side to side slightly so you can feel the positions where the voice coil moves in and out freely without touching the magnet assembly. This is their recommended approach, and they claim that most customers have no problem with it. (3) Use electro-mechanical centering. If you apply a small DC voltage (a single AA cell is sufficient - even 1 volt works in many cases) it will energize the voice coil, move the speaker inwards or outwards by a fair percentage of its Xmax, and the force of the "spider" and the magnetic field interaction between voice coil and magnet will tend to center the voice coil in the gap. I used method (3) when re-foaming a pair of Minimus 77 drivers, and it worked perfectly - no scraping was evident after the repair was done. I did it again, last night, when gluing new rubber surrounds onto a pair of Minimus 7 drivers, and it seems to have worked just as well. After the glue dried I disconnected everything, and gently pressed the dust caps, and the cones moved smoothly without any sign of rubbing. The method I used was: apply a positive voltage to the coil, moving the cone in the "outwards" direction for several millimeters. This makes it convenient to glue the new surround to the cone, as the outer edge of the surround will be up above the frame. Let the glue dry. Lift up the outer edge of the surround, spread glue on the frame, relax the surround, then turn voltage down to zero (returning the cone to its rest position), reverse polarity, and apply a small negative DC voltage. This pulls the cone "inward" slightly and snugs the edge of the surround down onto the glued frame. You can do this with just a penlight cell - when I did the Minimus 77 drivers I found that 1.5 volts was plenty, even with the two drivers wired in series. I took a more delicate approach with the Minimus 7 drivers last night, using an adjustable DC supply (with the current limit set to about 100 mA just to be safe!). |
| John-Del <ohger1s@gmail.com>: Nov 13 05:28PM -0800 On Tuesday, November 13, 2018 at 6:14:47 PM UTC-5, Dave Platt wrote: > wired in series. I took a more delicate approach with the Minimus 7 > drivers last night, using an adjustable DC supply (with the current > limit set to about 100 mA just to be safe!). Thanks Dave - I really like the idea of adding a bit of DC to the coil. I do have a programmable power supply so I'll be sure not to cook that VC with too much DC. I was thinking a nice, *slow* setting, syrupy although not too viscous adhesive would allow the cone to self center under the new foam. The kit the guy gave my brother has a small bottle of adhesive (that leaked a bit!). Hopefully it'll be suitable. |
| tabbypurr@gmail.com: Nov 13 06:46PM -0800 On Wednesday, 14 November 2018 01:28:51 UTC, John-Del wrote: > > limit set to about 100 mA just to be safe!). > Thanks Dave - I really like the idea of adding a bit of DC to the coil. I do have a programmable power supply so I'll be sure not to cook that VC with too much DC. > I was thinking a nice, *slow* setting, syrupy although not too viscous adhesive would allow the cone to self center under the new foam. The kit the guy gave my brother has a small bottle of adhesive (that leaked a bit!). Hopefully it'll be suitable. The coil is centred by the spider 100% of the time. What you want to centre is the edge of the speaker at the foam surround. There is nothing in the standard moving coil speaker mechanism that will do this by itself. Method 2 works IME. NT |
| Phil Allison <pallison49@gmail.com>: Nov 13 08:15PM -0800 John-Del wrote: > but I don't know if the dust caps can be removed somehow > from the cones without damaging them. > Any advice appreciated. ** Plenty of u-tubes to be found on speaker repair, including the art of replacing loudspeaker surrounds - whether foam or neoprene / rubber. This one in about the Infinity Crescendo CS3007 model. https://www.youtube.com/watch?v=UwVDVQ8_feI TIP: Speakers that use rubber roll surrounds last waaaaay longer. .... Phil |
| tabbypurr@gmail.com: Nov 13 09:15PM -0800 On Wednesday, 14 November 2018 04:15:41 UTC, Phil Allison wrote: > TIP: > Speakers that use rubber roll surrounds last waaaaay longer. > .... Phil than what? from what I've seen cloth lasts longer. NT |
| Phil Allison <pallison49@gmail.com>: Nov 13 09:36PM -0800 > > Speakers that use rubber roll surrounds last waaaaay longer. > than what? ** Than the kind mentioned in the *heading* and throughout of this thread - dickwad. |
| tabbypurr@gmail.com: Nov 13 09:56PM -0800 On Wednesday, 14 November 2018 05:36:10 UTC, Phil Allison wrote: > > than what? > ** Than the kind mentioned in the *heading* and throughout of this thread - dickwad. Expecting people to be mind readers is rather silly. |
| gregz <zekor@comcast.net>: Nov 14 08:41AM > before bonding the foams, but I don't know if the dust caps can be > removed somehow from the cones without damaging them. > Any advice appreciated. Applying tones to hear when it rubs works well. You can move outer around to get centered so the coil is parallel to pole piece. There is also the way to cut slits in dust cap and insert shims through dust cap. Then glue up slits when done. And check spiders for sag and securly attached to frame. Also check tinsel condition. A DC voltage and moving them should have no noise. When done apply low frequency sine wave and listen or any noises. Greg |
| Phil Allison <pallison49@gmail.com>: Nov 14 12:45AM -0800 > > ** Than the kind mentioned in the *heading* and throughout of this thread >> - dickwad. > Expecting people to be mind readers is rather silly. ** Never expecting that. You a lack the ability to follow the context. .... Phil |
| JoeF <f6ceedb9c75b52f7fcc0a55cf0cfbf5d_1119@example.com>: Nov 14 03:37AM responding to http://www.electrondepot.com/repair/lexicon-pcm70-legacy-digital-effects-unit-38488-.htm , JoeF wrote: > even as NOS. Anyone help ? > TIA > Arfa Still interested after all these years? I've got one. JF3 |
| Fox's Mercantile <jdangus@att.net>: Nov 13 10:00PM -0600 On 11/13/18 9:37 PM, JoeF wrote: >> Arfa > Still interested after all these years? I've got one. > JF3 I forwarded to Arfa -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
| Jeff Liebermann <jeffl@cruzio.com>: Nov 13 09:17AM -0800 On Mon, 12 Nov 2018 16:50:02 +0000, >Can anyone suggest why this is occurring (bearing in mind that it only >affects the left channel) and can anyone suggest a cure? I would guess(tm) that the "ticks" are coming from something outside of the recorder. Try testing it again at a different location. If the "ticks" go away, look around at your original location for suitable culprit. Periodic noises are fairly easy, but random is difficult. For example, I just found a similar problem that was caused by RF noise from an ultrasonic mouse and rat repeller: <http://www.victorpest.com/store/rat-control/ultrasonics> The device produces random ultrasonic noises and whatever was doing the randomizing was also producing random bursts of RF noise. You might have something similar happening. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
| adrian@poppyrecords.invalid.invalid (Adrian Tuddenham): Nov 13 06:00PM > >affects the left channel) and can anyone suggest a cure? > I would guess(tm) that the "ticks" are coming from something outside > of the recorder. Try testing it again at a different location. I first noticed it when I was recording a brass band in a school hall and subsequently a radio play in a small studio - the test recordings were made on the kitchen table at home. It doesn't appear to be location-specific. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
| adrian@poppyrecords.invalid.invalid (Adrian Tuddenham): Nov 13 06:00PM > > ....beware loud clicks! > Any chance of cutting a couple of traces and jumpering/swapping left and > right to see if the problem swaps channel or stays the same? I really don't want to go butchering it, I'mrelying on it quite a bit for location recordings. > tapes. > A small bit of ferrite/magnet buried in the pinchwheel rubber was the > cause there. I've had that happen with a car cassette player, the tapes got worse and worse until one day I found the cause. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
| John-Del <ohger1s@gmail.com>: Nov 13 11:17AM -0800 On Monday, November 12, 2018 at 11:50:19 AM UTC-5, Adrian Tuddenham wrote: > connected to anything, for it to happen. If there is any sound on the > channel, the noise immediately stops, but re-starts about one second > after complete silence returns. To be clear, this doesn't happen when using the internal mics? What sort of "external circuit" are we talking about? If it only happens when recording silence, wouldn't that be easily mitigated with post production software? But if it's a design problem, I would try adding an osc signal above audible frequencies at low levels right at the input jack. Should have no effect on the recorded audio and may be enough to keep the phenomenon from happening. If there's no room inside the Tascam, maybe you can add it to the external circuit. |
| N_Cook <diverse@tcp.co.uk>: Nov 13 07:22PM On 13/11/2018 18:00, Adrian Tuddenham wrote: >> cause there. > I've had that happen with a car cassette player, the tapes got worse and > worse until one day I found the cause. Do you use batteries or what used to be oddly called "battery eliminators" to power the recorders? |
| N_Cook <diverse@tcp.co.uk>: Nov 13 07:27PM On 13/11/2018 19:17, John-Del wrote: > What sort of "external circuit" are we talking about? > If it only happens when recording silence, wouldn't that be easily mitigated with post production software? > But if it's a design problem, I would try adding an osc signal above audible frequencies at low levels right at the input jack. Should have no effect on the recorded audio and may be enough to keep the phenomenon from happening. If there's no room inside the Tascam, maybe you can add it to the external circuit. Even if it had to be sub 20K , then it could be knotched out quite easily as only low level anyway and doubtful whether anyone would know. |
| dplatt@coop.radagast.org (Dave Platt): Nov 13 02:59PM -0800 In article <1ny79x7.wl3ij9kcn7mqN%adrian@poppyrecords.invalid.invalid>, >Demonstration at: >www.wrightshardware.co.uk/Other/DR0002_0276.wav >...beware loud clicks! Looking at that file, I see three sets of noisy impulses... two negative-going and one positive-going. They're present in both channels - similar but not identical waveforms in the two channels. There's a very sharp leading edge (rise time is two or three samples) and then a much slower fall, with some ringing. The signal takes about 40 milliseconds to fall back to zero, and then overshoots. This doesn't look like a one-sample error on the digital-storage side of things - it's not just a brief impulse. It appears to me that something is spiking the input to the ADC pretty hard, and that this glitch is getting into both ADC inputs. The fact that the pulse and ringing is slightly different, between the two channels, suggests that it's not just a single sample of bad data in the ADC being blurred out by the ADC's filters. Is this .WAV exactly as it came out of the recorder, or did you adjust it (e.g. gain-boost for visibility) in any way? |
| adrian@poppyrecords.invalid.invalid (Adrian Tuddenham): Nov 13 11:31PM > > worse until one day I found the cause. > Do you use batteries or what used to be oddly called "battery > eliminators" to power the recorders? Two AA cells, recharged in a separate charger. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
| adrian@poppyrecords.invalid.invalid (Adrian Tuddenham): Nov 13 11:31PM > > channel, the noise immediately stops, but re-starts about one second > > after complete silence returns. > To be clear, this doesn't happen when using the internal mics? That is correct - or at least I have never noticed it. I'm guessing it is because: 1) I never use the internal mics for professional work and rarely use them at all. 2) When I do use the mics, nowhere is quiet enough to show up the effect. 3) I would record from the mics with the gain at a level where just the pre-amp noise floor prevented the effect. > What sort of "external circuit" are we talking about? I tried it with a 'double-ender' 3.5mm screened jack lead about a foot long, with nothing connected to the far end. The effect also happens with the same lead plugged into a passive mixer and also on a longer lead with a built-in 12dB attenuator, fed from a powered mixer I have also used a passive distribution box with separate L and R inputs (P.O. 315 jacks) taking line level from the mic pre-amp (floating and battery-powered) and delivering signals to two 3.5mm output plugs, one attenuated by 12 dB and one by 24 dB for the two recorders. > If it only happens when recording silence, wouldn't that be easily > mitigated with post production software? I had to do that on one occasion, but it is time-consuming taking out the clicks by hand. I would rather tackle the problem at source if at all possible. > effect on the recorded audio and may be enough to keep the phenomenon > from happening. If there's no room inside the Tascam, maybe you can add > it to the external circuit. ...or add a bit of hiss to dither it. ...or add a sub-audio signal. ...or never turn the recording gain right down and let the pre-amp noise floor take care of it.. I haven't looked to see if new software is downloadable for that model - but I suspect this is more likely to be a hardware fault. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
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