Ross Matheson wrote:
: Having bought a pair of Rogers ls6a speakers last week I hooked them
: up to my 80 watt Plinius pre power amp and spent a great night
: listening to a variety of music reggae, rock , jazz. The next day I
: had an opportunity to test the ls6as at higher volumes. The music was
: loud with the amp between 70% and 80% load.
How was it determined that the amp was between 70 and 80 percent load?
: I was listening to
: Leftfield "Leftism" and ON-U sound system. This music is quite bassy
: and electronic.
OK, something modern, overcompressed bass-junked crap. That genre of
music, and the music itself can indeed be excellent, tends to contain
large amounts of very deep bass, something like 10 dB more than a
probable powerhanding asumptions for your loudspeakers assumes.
: I didn't hear any distortion but then at the same
: volume there was a small amount.
It takes time to heat a voicecoil, once it is hot it expands, and in all
likelyhood a single turn got loose and scraped.
: I turned down the speakers with evry
: thing still seeming okay.
Yes, but voice coil heat expansion was not yet done.
: When I returned to play music later there
: was a problem with one speaker. Even at moderate
: volume the bass is indistinct distorted and rattley.
Probable problem: multiple windings has left the coil former and scrape
against the magnet.
: 1 Do you think I should send just the bass driver and ask that it be
: repaired by having the coil rewound (the likely problem) or the
: complete speakers and have them fully tested graphed and serviced.
Which is to say that you feel bad about it and worry whether you also
destroyed the other one. No - it still works or Yes - send them both.
You have received advice about a local service facility, you should ask
them. It is highly probable that the service recommendation in case it
is about a reconing is to recone both units in a stereo pair, but it may
matter more with some membranes than with others.
Yes. Well, over to you after consultation but maybe just the faulty unit.
Best local contact (as a multiply pleased and happy customer) is
AXENT AUDIO PRODUCTS LTD: Loudspeaker & Audio Specialists
25 Portage Rd New Lynn Auck Ph (09)827-1220 Fax (09)826-0302
email: sales AT axent.co.nz (I've munged that!)
: 2 Should I be able to play this bassy electronic music at higher
: volumes
Yes, with suitable loudspeakers and or with sane use of the volume
control. Generally that type of music requires and deserves a subwoofer.
: or should I adopt a more conservative approach?
Sir, you have purchased loudspeakers designed for on site monitoring of
location recordings of The Academy of Saint Martins in the Fields, the
Ridgeway Bach Choir and the like.
You are - politely said - utterly out of your mind if you think you can
use such loudspeakers for MumboJumbo of the JumbleJungleBazzRamTaTa if
played at party levels after consuming even modest amounts of alcohol.
Reason #1 is the very simple one that you loose 3 dB
sensitivity pr. bottle of beer or glass of fine wine.
Reason #2 is that the excellent loudspeakers you have
are quite unable to reproduce anything below some 45 Hz.
Reason #3 is that those very same excellent loudspeakers
have a RMS powerhandling of some 20 to 40 watts continuous
sinewave. (twice that for "integrated programme", twice
that for "music power", add VAT and you get a 200 watts spec
that I can not believe is the factory spec for RMS but it
may well be the recommended max amplifier size) (x)
(x) max amplifier size == kinda like the amp that will not have enough
power to push the bass unit voicecoil through the membrane on an
orchestral bass drum hit nor melt the treble unit with a single cymbal
hit, nothing like using it for max power in sinewaves or broadband
noise.
: I would be
: satisfied with using these speakers at moderate volumes but would like
: to be able to have an occasional party with some dance music. Is this
: unsuitable?
Most. You have to understand that powerhandling is about average power,
and the type of music that goes well with a party may have an average
power as high as -6 dB relative to max power (25 percent). That is the
asumption done when specifying powerhandling for rock loudspeakers,
consequently mostly also an asumption that includes the possiblity of
gravely (more than 10 dB) clipped poweramps. If ya wanna do that kind of
music under that kind of conditions then get that kinda loudspeakers and
do remember to read the warning label about damage to your hearing.
In contrast the music and sound production style the designer(s) of your
loudspeakers had in mind is likely to have an average power no higher
than -15 dB relative to max power and generally -20 dB, only if via
compressed FM broadcast - and not all broadcast of classical/acoustic
music is compressed, not even all webcast, say BBC - will it reach -10
dB. It is fairly easy to see that a recommended max amplifier size of
200 watts with at most 1 to 5, worst case 10 percent used when averaged
makes a lot more sense in the context of a loudspeaker with a probable
40 watts RMS powerhandling.
It's possible you drove them too hard, I suppose, but you should look into
everything ...
If he drove the amp to 80 percent based on the volume control being at
"8" on a scale to 10, the he clipped is amp gravely.
perhaps it was already slightly compromised,
As good an explanation as any other of why that one and not the other.
But is is kinda like having a slighly damaged piston in a car, you can
drive 100 miles with it with no problems or 100000 miles and not knowing
it, no extra oil used, and it will not matter. It will only matter the
next time the engine overheats in which case that will be the piston
that "has a problem".
Yes, it actually may even have died the first time and scraped loudly,
but it came back and lived on because the voice coil contracted
reasonably back in shape.
maybe the
extended session has caused an overheated and swelling voicecoil ... does
the surround look intact? Cabinet sound and airtight (apart from port)?
Seems like just a single damaged bass driver from your description IMO.
I have an expat friend who has, I think, a kit version of these ... Axent
were able to help. [I wonder if the crossover is worth inspecting, too.]
It usually takes a larger amp than 80 watts to really whack a cross-over
.... if the shop is nearly or freight is cheap, then by all means, if it
is far away or freight is costly then it does come to mind not to ship
the boxes along, but only the relevant unit(s).
: I dearly love these speakers and would like suggestions as to how to
: maximize my listening pleasure.
Respect them as classical performes, they are not the Johnny Winter's of
the speakerworld, rather the Menuhin's.
Oh, and get a sub if you wanna do bass, be it organs or synths.
Reasonable powered subs may start as low as some 150 of your local
dollars if they are only for party use. Subs actually able to do deep
bass may cost more .... O;-) ... and I will still suggest looking for
something far more sturdy, Cerwin Vega's or something like that, for
party noisemaking. I think Behringer has a not-too-costly &
I-wonder-how-good powered PA speaker that may make sense in case you
want to play Abba on the back porch ...
: Dave Winter
Axent are THE specialists in NZ for speaker repair, test, development etc.
Just contact them and see what they say - I'm sure they handle Rogers.
Best of luck. I'm sure you'll be helped!
Ross Matheson
nz not zn
PS: They weren't these ones, were they? ;-)
http://tinyurl.com/xnsz
Thanks for coming up with that link with a picture of the loudspeaker
model, it was most helpful for the guesstimates above, mind you folks:
guesstimates.
--
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