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Post by Deleted on Dec 31, 2015 16:32:30 GMT
Those Electra Be tweeters can take a fair amount of punishment, though short shape shock treatment is not the best way to keep them in top condition.
I would suggest the following, switch off amp, let current drain from caps give it 5 minutes to sure.
With the span of your hand opened up push gently against the bass driver cone it should be a smooth quiet transition between max and minimum cone excursion.
If it feels notchy, rouch or makes any out of the ordinary noises then I would look at inspecting the driver concerned.
Repeat this for the four bass drivers.
Jez's observation regarding volume knob/digital counter to power output is valid, this is purely down to line level output voltage at a given point on the dial / readout.
If you wished to be BBC engineer about it, you could use a 300W dummy load instead of the speakers and match up the volume position measure the voltage with DVM and then calculate the output in watts unless you have a scope or Spectrum or Network analyzer handy.
The tweeters you could use some test tracks over 400Hz and upwards to help ascertain as to whether you would need to remove them for a physical inspection / measurement session.
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Post by MartinT on Dec 31, 2015 20:12:15 GMT
Hah, logarithmic scales catch a lot of people out.
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Post by Deleted on Jan 1, 2016 16:15:27 GMT
I seriously doubt that would do damage. I listened well past 11 o clock (closer to 1 o clock) with exposure amps and Snell Js (94db) on a daily basis. Probably closer to 1 o clock and that was wtth a Dual IV HEY YOU! TURN IT DOWN!!!  S. Hey Shane: Did you buy a Frog or is it just a dream?  Youll know if your Tweeters arnt 100% |
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Post by Deleted on Jan 1, 2016 16:37:49 GMT
The position on the volume control has nowt to do with how much power is being produced. Depends on output of source and input impedance of amp as well as pot design as well as speaker efficiency. I would expect max vol to be close to max on a well designed and matched set up. You would likely blow your ear drums before the speakers in most cases (well before max volume). At first I thought this must be a 'Spinal Tap' 11. |
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Post by dsjr on Jan 1, 2016 17:05:04 GMT
The problem is that the old Exposure was designed before CD I think, and so the volume control and phono stage gain structure is designed around old tuners and tape decks with half a volt max output. The volume control may probably be around two o'clock for a fairly high volume with these pre CD sources - and (sorry Marco  ), that's how it was supposed to be, so you could use ALL of the volume control, not just a third of it! Of course, in 1983 along comes CD with nearly three times the output of a typical 70's tuner and these old amp designs were then hobbled with nine o'clock on the control often being 'loud' with a CD source This, coupled with possible input overload on buffered designs like the Quad 33, used to give no end of problems I remember, the obvious being to pad the CD player down in level, only to amplify it again in the preamp! To the audio-uneducated, having a very loud volume level with the control barely a quarter of the way up, just made them think the amp was more powerful than it really was and this way of thinking continues to this day sadly. In my domestic situation, the bridged Crown amps have their gain pots turned down to half way and this means the preamp works much harder, the volume setting on CD being around one to two o'clock most of the time. The tuner needs around two to three o'clock for similar perceived volume - and that's just how Crown designed their pre and power amps at the time to work (more modern op-amps in the preamp have removed the necessity of this setup now, but I still adhere to it). With the NVA system upstairs, the volume control is more set to modern settings as the power amps are deliberately more sensitive and of highish impedance (I think) to allow good use of a passive pre. CD plays comfortably at around ten o'clock but low levels has the control just off minimum. The film pot normally used and the stepped attenuators have different laws though, but I'm muddying the water even more now. The ladder type attenuator currently fitted to my P50 passive pre (not authorised by the Doc) does almost nothing until half way up, but then the steps become quite sharp. The difference on the last two clicks is massive. Hope the experiences above go some way to explaining what a volume control does and to try to explain how the control position from minimum has NO bearing at all on amp output. The only way a speaker will be damaged on music is if there's a hugely pounding bass line that bottoms the bass unit out, usually continuously with a moderately powered amp like the Exposure, or if the amp is overdriven for a period, causing the tweeters to fry. Loud peaks or a few seconds' of inadvertent high volume *shouldn't* do any damage at all, other than give the system owner a fright |
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Post by Deleted on Jan 1, 2016 17:34:13 GMT
The problem is that the old Exposure was designed before CD I think, and so the volume control and phono stage gain structure is designed around old tuners and tape decks with half a volt max output. The volume control may probably be around two o'clock for a fairly high volume with these pre CD sources - and (sorry Marco ), that's how it was supposed to be, so you could use ALL of the volume control, not just a third of it! That is right Dave. My amp has to be up around 12 o'clock for good listerning via Turntable, a bit louder when headphones are attached. I don't worry about CDee anymore because im 100% Vinyl system these days. |
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Post by Deleted on Jan 1, 2016 17:47:27 GMT
Paul's Exposures were the last of the JF pre/power pairings so they date to the 1990s and are therefore well after CD took hold. I seriously doubt any input would overload with CD at 11 o clock
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Post by MikeMusic on Jan 1, 2016 17:49:58 GMT
The Pass goes up to 83 and that was dangerously, monstrously loud even with no signal
From somewhere..... I seem to remember each number on the Pass = 1db
So listening at 60 is *loud *.
83 would do damage
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Post by MartinT on Jan 1, 2016 18:57:42 GMT
So listening at 60 is *loud *. 83 would do damage Only if the power amp could track that high in power. It would likely hit the end stops before that. |
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Post by Deleted on Jan 1, 2016 19:56:07 GMT
Paul's Exposures were the last of the JF pre/power pairings so they date to the 1990s and are therefore well after CD took hold. I seriously doubt any input would overload with CD at 11 o clock Yes the XVII and XVIII were the last of the JF designs and are of a 1994 vintage. I have had a good inspect of the drivers as recommended by Tony and they all look fine and appear to sound fine so I think I've been luck, thankfully |
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Post by dsjr on Jan 1, 2016 21:14:25 GMT
Thanks for clarifying the dates, although I wonder how far back the circuits go - not criticising as much of my stuff pre-dates the creation of Exposure by JF I suppose that if there was a risk of this happening again, the power amp could either have its gain reduced a little - or a dedicated attenuator could be fitted using high quality resistors (just in case you thought their insertion might be audible). The only time I've *really* done damage, albeit accidentally, was in my early 80's Naim days, when a Naic cable hadn't latched properly and came out - they had push-latching din's back then, not the twist-locks. The resulting deafening scream from the Isobariks took the Scan tweeters out in seconds and removing them took some of the chipboard with them as they used putty or similar to seal them in. |
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Post by MikeMusic on Jan 1, 2016 21:28:11 GMT
So listening at 60 is *loud *. 83 would do damage Only if the power amp could track that high in power. It would likely hit the end stops before that. So there is a safety built in to the power amp ? Good to know To protect amp and speakers ? |
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Post by MartinT on Jan 1, 2016 21:58:44 GMT
Not a safety, Mike, simply its maximum operating limits. 23dB above what you call *loud* would be beyond the power capabilities of almost any hi-fi amp on the market.
The amount of clipping distortion at that level would blow virtually any tweeter, which returns us neatly to the o/p.
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Post by Deleted on Jan 15, 2016 23:43:31 GMT
I can confirm after spending a very pleasant afternoon listening to the system that all is well with the speakers. Thanks for the advice given everyone.
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Post by ChrisB on Jan 15, 2016 23:45:38 GMT
Good news
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Post by Deleted on Apr 13, 2016 12:39:42 GMT
So update,
Something to my mind isn't quite right.
I'm finding that vocals specifically sound strained when pushed, now I spoke to Focal who said they'd doubt the speakers could have been damaged unless the amps clipped but they have suggested it could be the amplifiers themselves that have been damaged.
Unfortunately because these are the earlier John Farlowe amps there isn't really anyone at the current Exposure that could help, there's a guy called Tony I have been advised to contact so will email him but just wondered if anyone on here could advise?
Is it possible to knock out the balance if the sound by doing this sort of thing? Or is it purely in my head?
Paul.
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Post by MikeMusic on Apr 13, 2016 12:51:34 GMT
Get a second pair of ears on the case
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Post by Deleted on Apr 13, 2016 12:55:31 GMT
Get a second pair of ears on the case You free? |
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Post by MikeMusic on Apr 13, 2016 12:56:27 GMT
In May !
About 2nd week on
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Post by zippy on Apr 13, 2016 13:59:14 GMT
It's not really possible to equate power directly to volume control position of course... stating the bloody obvious I know but I've been amazed (shocked!) as to how many people think things like "it's a 100W amp so at 5 it will be giving 50W" etc! Yes I too am amused when people ask ' what level do you have your volume control' when that equates only approximately to the volume of the music. Even more confusing when your amp shows attenuation - e.g. my Cyrus displays from -80 (virtually inaudible) to 0 (much too loud). On top of that I think it's a logarithmic scale so -30 to -20 isn't as much difference as -20 to -10. I tend to have it running at about -30 for rock, -20 for classical. |
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), that's how it was supposed to be, so you could use ALL of the volume control, not just a third of it!
