gregt@tektronix.UUCP (Greg Thomas) (03/15/84)
I'd be very interested to hear some opinions about the better Acoustic Research speakers, such as the AR-9 (unfortunately I'm not able to recall other model numbers). I'm considering getting a pair since a family member can get me a deal on them. Perhaps others are interested. Can we get a discussion started?
bill@dual.UUCP (Bill Kanawyer) (03/15/84)
< Bug Filter >
I have two notes on the AR-11s.
First off, it is very very easy to blow out the mid and high freq drivers.
When I was working for the Laserium (light shows) we used 24 of these in one
area (Cleveland) and I seemed to always be replacing drivers. I have also
had experences with people I have known who have had AR-11s and replaced
the mid and high drivers. It would seem that they are over rated for the
rated speaker wattage. Look out!
2nd, opinion. I myself do not like the sound of the dome tweeters they
use in the AR-11s. Too harsh for my tastes. I used to wear headphones during
the shows to save my ears!
Please note that AR3as seem to fair much better.
Bill Kanawyer
{ucbvax,amd70,ihnp4,cbosgd,decwrl,fortune}!dual!billrcd@opus.UUCP (03/16/84)
<> > I have two notes on the AR-11s. > > First off, it is very very easy to blow out the mid and high freq drivers. > ... > 2nd, opinion. I myself do not like the sound of the dome tweeters they > use in the AR-11s. Too harsh for my tastes... Obviously I don't know the circumstances around this - but I would conjecture that these two are related and perhaps not the fault of the speakers. When an amplifier is overloaded, meaning that it is asked to deliver more power than it has, it will "clip". What that means is that as the amplifier tries to follow a rising signal, it runs into the upper limit of its power supply's capability. The top of the waveform gets chopped off. In some amplifiers, this cutoff happens very abruptly so that you get a "corner" in the waveform. The effect is the same as an impulse with gobs of high-frequency power. The sound is extremely harsh, and letting an amplifier run in clipping mode for very long can put trash into the higher-end speakers that will fry them. People tend to overlook this phenomenon because speaker systems are normally rated in terms of "system capacity" which assumes a reasonable frequency distribution. However, in a system regarded as capable of operating with a 100 W amplifier, it may only take 10 watts to blow out a tweeter. Another reason that the phenomenon is overlooked is that an amplifier in clipping can produce bursts of power which far exceed its rated power output - yes, a 10 watt amplifier can produce 50 watts of pure high-frequency crap for short intervals. So (as he finally returned to the point of the discussion), it could be that the speakers were being driven by an overworked amplifier driven into clipping, and they were being killed by the amp. -- {hao,ucbvax,allegra}!nbires!rcd
seifert@ihuxl.UUCP (D.A. Seifert) (03/20/84)
In defense of the AR-11 loudspeaker:
I am quite familiar with these, I've owned a pair for several years.
I have only heard one speaker that sounds clearly superior, that is
the Snell type A. (The AR-9 is a second possibility, but I haven't
listened to these enough to judge them fairly) The Klipsch Cornwalls
and Klipschorns sound approximately similar in quality.
(The Heresy deserve to be hooked up to a $5 AM radio.) Close
seconds include the ADS 810s, the Dalquests, and Magnaplaners.
No speaker is perfect. The AR-11 does not have the *very* low bass
needed for organ pedal notes, it's 3dB point is approx 35Hz. This
is quite adequate for most other music, the limitation is usually
the source, not the speaker. Between 35Hz to over 20Khz, the response
is within +/- 5 dB. Not perfect by any means, but very good.
Remember this is a speaker, not an amplifier. (BTW, I have a
plot of the response measured at a speaker clinic by another
speaker manufacturer, which used a short burst method to eliminate
standing waves or other room effects. I'm not just going by AR's
specs or a magazine report.) They are also of "reasonable"
size, weight, and cost, as opposed to most other speakers I can
stand to listen to.
About the treble response. Some people like the sound of AR's
tweeters, some don't. I'm quite happy with it, a couple of my
audiophile friends have minor quibles with it. (The ones with
the ADS 810s and Dalquests) Apparently there is some imperfection
in the high frequency response of ARs that bother some people,
but not others. Other speakers have similar slight problems that
*do* bother me (but don't bother others). I picked the speaker
that had the problem *I* couldn't hear. The ADSs have a slight
problem in the bass. (possibly room related) The Dalquests *require*
a subwoofer, since they cut off at 60 Hz. And so on. The idea
is to find a speaker that sounds good to *you*, even if some
other speaker measures better on the average. If it has some querk
that grates on your ears you're going to hate it, no matter
*how* many golden ears praise it, or how wonderful it's measures
specs are.
About power handling. I've never blown a driver in them. The
rating given by AR is 150 watts clipping 10% of the time, on
normal "music" (not sine waves). I have observed clipping
at over 110 watts (as measured on a 'scope) with no problems.
My current amp is rated at 200 watts into 4 Ohms and so far
no problems. (Thou I'm not stupid enough to drive it into
clipping at these power levels, also I don't listen to hard rock
(read: loud) much these days) The amp (Hafler) has speaker fuses (2 Amp).
Once a source created a high level noise and blew one of the
speaker fuses, with no problems. In the owners manual, AR
gives a rather complete spec for power rating. The main problem
is heat buildup, so you can actually pump, say 1000 Watts into
one for a very short time, say 2 seconds, with no damage.
(Check the manual for exact figures) In the setup described
in previous articles, the amp is quoted as being 1000 Watts, and
24 speakers were used. Assuming power was equally distributed
to all speakers, this gives 41.6 Watts per speaker, which
*should* have been quite safe, given "normal music" and less
than 10% clipping.
Correct me if I'm wrong, but isn't the AR3a a member of the
previous (1st) generation, with *much less* high freq output? (They
hadn't invented the whiz-bang dome tweeter with ferro-fluid yet)
Maybe you like a speaker with less treble? (Try playing with the
switches on the back of the speaker, or use eq) In fact I seem
to remember reading about how the hot setup used to be using
ARs for bass, and someone's electrostatic tweeter for treble.
I think they might have even made a woofer-only system just
for this sort of application!
Warning, before anyone runs out to audition AR's latest,
don't judge the 2nd generation ARs by the 3rd generation
garbage they're making now. I don't know what they did to
screw them up, but the current ones sound *bad*, dispite
things that should be improvements like lining up the drivers
for better imaging. Haven't listened to them enough to figure out
*what's* wrong, thou.
The opinions expressed above are mine alone.
--
_____
/_____\ I taught Walter Mitty everything he knows!
/_______\ Snoopy
|___|
____|___|_____ ihnp4!ihuxl!seifertbrb@philabs.UUCP (Brian Bertan) (03/20/84)
The following was said of the AR-11 speakers: >>Just remember when buying these to use them with an amp of<< >>modest power. 30 watts per channel is more than enough to use.<< I just had a party and I played VERY LOUD music through a pair of AR-9LS speakers, which have the same tweeter found in some of AR's less expensive models. I was using a Carver amp rated at 300 watts/channel into 4 ohms. The amp overheated and shut down, so you can imagine how much power was used, and my AR's tweeter did not blow (the amp should not have shut down -- I hear Carver amps have this problem but we can flame about it some other time). I agree with nbires!rcd's statement regarding low power amplifier's. A high power amp supplying clean power is less likely to fry a tweeter than a low power amp that clips and delivers horrible harmonics. Brian Bertan Philips Labs Briarcliff Manor, NY {allegra | decvax | seismo}!philabs!brb (914) 945-6309
grw@inmet.UUCP (03/22/84)
#R:tektronix:-184000:inmet:2600056:000:852 inmet!grw Mar 20 13:21:00 1984 I have a pair of AR12 speakers. I have had them for about 5 years and I am generally very happy with them. They were cheap (I bought them as demos) and they have never had any problems with drivers blowing. They are very sensitive to room acoutics (as are all speakers) and I have had to play with the high and mid cut switches on them as I've moved from one place to the next. I recently took them to a party at which they were blasted for 5 hours by small amps (probably clipping a fair percentage of the time) with no apparent damage. SR this month has some nice things to say about the new next-to-top-of-the-line ADS speaker (1290?). You might check the whole new ADS line out before deciding on ARs. My folks recently bought a pair of AR48s. They sound OK though the high end (they have a cone midrange) leaves something to be desired.