Restek powered studio monitors
Arfa Daily
these in with the surrounds rotted away on the bass drivers. Apparently,
these things were 8 grand apiece 12 years ago when new. He managed to get
some new cones / surrounds from the States somewhere for a reasonable price,
and fitted them. One of the amps also needed a new level pot, so he put one
of those in, too. When he repowered them, one worked perfectly, but the one
that he had put the pot in, buzzed so loudly that it nearly destroyed his
new cone work. He couldn't see anything that he had done wrong, so he sent
them both to me. One double hernia later, I had them both up on the bench.
They are signal-sensing for main power turn on, so first I had to work out
which was the relay for this, and bridge it such that the amp could be
powered via a variac. At about 40v input, the amps started working (separate
amps for bass and mid / top drive) but the bass amp started motorboating
violently. I spent a very long time checking caps in the power supply and
bass amp. Interestingly, I found one with very poor ESR on the driver board,
but replacement made no improvement, and then a 470uF that read very good
ESR - in fact so good, that it rang alarm bells, so I whipped it out and put
a good old analogue ohm meter across it. It was short circuit (near enough).
Remember we were talking about just this a couple of days back in the thread
about SMPS cap testing, where someone asked if an ESR meter showed a cap as
good, could it still be bad, and someone else then commented that a straight
ohms test should be carried out "for sanity" I think was the phrase. Well
here we are with a good real life example. Anyway, that turned out to be a
red herring too. I don't know what that cap did as I have no schematics, but
a replacement had no effect on the instability problem.
At this point, having already spent too long on the job, I phoned the store
owner to tell him where we were at with the problem. He then went through
what he had done again, and then casually tossed in that the voice coils on
the bass units that he had re-coned, were unusual in that there were two of
them per driver ...
Now some real alarm bells started to sound in my head. I asked him if he
meant that the drivers had four wires going to each of them, and he said
yes. I hadn't actually seen the backs of the drivers, as they come out from
the fronts of the cabs, and the backs are packed with damping material. I
rang off, and pulled one out, and indeed, there were four terminals, two of
which had a fairly heavy piece of twin connected to them, and the other two,
had a piece of thin screened wire connected to them. Looking at the
soldering, he had definitely had these wires off, so I removed the screened
wire, and reversed it. That cured all the problems, so I have to conclude
that the second 'voice coil' is in fact some kind of feedback winding, and
when the cone went say forward, this winding, being reverse connected, was
telling the amp that it had moved backwards, playing havoc with the
stability.
In many many years of servicing all sorts of hifi and audio amplification
equipment, I don't ever recall having come across a bass driver with a
feedback coil like this. Has anyone else on here, or anyone have any
knowledge of the system, and what the advantages are claimed to be ?
Arfa
Ron
Didn't Phillips do something like this back in the 70's? Motion feedback
or some such daft name?
Ron
--
I am using the free version of SPAMfighter.
We are a community of 7 million users fighting spam.
SPAMfighter has removed 1580 of my spam emails to date.
Get the free SPAMfighter here: http://www.spamfighter.com/len
The Professional version does not have this message
whit3rd
> Didn't Phillips do something like this back in the 70's? Motion feedback
> or some such daft name?
I think they called it 'David', it was a motion feedback woofer in a
powered-speaker
form factor. This kind of system can control the low frequency
behavior
of the cone very accurately. Mossbauer apparatus uses the same
hardware for motion control with < .01% distortion, but that's a
linear-motion
measurement, no idea what the air movement effectiveness is.
Arfa Daily
>
>> Didn't Phillips do something like this back in the 70's? Motion feedback
>> or some such daft name?
>
> I think they called it 'David', it was a motion feedback woofer in a
> powered-speaker
> form factor. This kind of system can control the low frequency
> behavior
> of the cone very accurately. Mossbauer apparatus uses the same
> hardware for motion control with < .01% distortion, but that's a
> linear-motion
> measurement, no idea what the air movement effectiveness is.
>
OK, both. Don't remember the Philips system, but then the company that I was
working for back then, didn't do much with Philips. Still, that sounds like
the sort of system. Those specs for the Mossbauer are impressive. I guess
that's the sort of thing that it's going to be, given the claimed value of
these things. I've just been listening to a CD through them. They sound
nice, and very smooth with a very flat and stiff sounding bass. Quite easy
on the old lug-holes, but I'm not sure that I would rate them as 16 grand
more easy than my home-built EMI 13 x 8 cabs from the 70's ... :-)
Arfa
Ron
Ahh 13 x 8's did they have the whizzer cone in the centre?
David Nebenzahl
> On 28/07/2010 17:50, Arfa Daily wrote:
>
>> I've just been listening to a CD through them. They sound nice, and
>> very smooth with a very flat and stiff sounding bass. Quite easy on
>> the old lug-holes, but I'm not sure that I would rate them as 16
>> grand more easy than my home-built EMI 13 x 8 cabs from the 70's
>> ... :-)
>
> Ahh 13 x 8's did they have the whizzer cone in the centre?
Whizzer cones? Are you pulling our legs?
I always associated whizzer cones with the know-nothing, 6x9 oval weird
expensive speakers to throw in the back of your car market, not anything
near audiophool quality. Am I wrong?
--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.
- Comment from an article on Antiwar.com (http://antiwar.com)
William Sommerwerck
> 6x9 oval weird expensive speakers to throw in the back of
> your car market, not anything near audiophool quality.
> Am I wrong?
Yes, and no.
The whizzer was a kind of tweeter. But it also served the purpose (though I
don't understand the mechanics) of decoupling the central section of the
driver, allowing it to do a better job with the mids and highs.
My understanding is that there /were/ some "good" drivers with whizzers, but
I don't remember the manufacturers or models.
Please do not equate "audiophile" with "audiophool". If nothing else, it's a
rude insult to the people who have gotten high-quality sound reproduction to
the point where it is.
David Nebenzahl
>> I always associated whizzer cones with the know-nothing,
>> 6x9 oval weird expensive speakers to throw in the back of
>> your car market, not anything near audiophool quality.
>> Am I wrong?
>
> Please do not equate "audiophile" with "audiophool". If nothing else, it's a
> rude insult to the people who have gotten high-quality sound reproduction to
> the point where it is.
I don't equate the two; it was just a built-in disclaimer.
To a first approximation, audiophools swear by Monster cables and
gold-plated connectors, which audiophiles do not.
Phil Allison
"Ron"
>
> Didn't Phillips do something like this back in the 70's? Motion feedback
> or some such daft name?
>
** Philips MFB speakers used a piezo ceramic accelerometer mounted on the
cone.
... Phil
Adam Sampson
> In many many years of servicing all sorts of hifi and audio
> amplification equipment, I don't ever recall having come across a bass
> driver with a feedback coil like this.
It's a common enough arrangement for subwoofers -- the term to search
for is "servo". Proponents claim significantly lower distortion.
--
Adam Sampson <a...@offog.org> <http://offog.org/>
Arfa Daily
"Ron" <r...@lunevalleyaudio.com> wrote in message
news:54KdnVpXyYEKHc3R...@bt.com...
> On 28/07/2010 17:50, Arfa Daily wrote:
>>
>>
>>>
>>>> Didn't Phillips do something like this back in the 70's? Motion
>>>> feedback
>>>> or some such daft name?
>>>
>>> I think they called it 'David', it was a motion feedback woofer in a
>>> powered-speaker
>>> form factor. This kind of system can control the low frequency
>>> behavior
>>> of the cone very accurately. Mossbauer apparatus uses the same
>>> hardware for motion control with < .01% distortion, but that's a
>>> linear-motion
>>> measurement, no idea what the air movement effectiveness is.
>>>
>>
>> OK, both. Don't remember the Philips system, but then the company that I
>> was working for back then, didn't do much with Philips. Still, that
>> sounds like the sort of system. Those specs for the Mossbauer are
>> impressive. I guess that's the sort of thing that it's going to be,
>> given the claimed value of these things. I've just been listening to a
>> CD through them. They sound nice, and very smooth with a very flat and
>> stiff sounding bass. Quite easy on the old lug-holes, but I'm not sure
>> that I would rate them as 16 grand more easy than my home-built EMI 13 x
>> 8 cabs from the 70's ... :-)
>>
>>
>> Arfa
>
> Ahh 13 x 8's did they have the whizzer cone in the centre?
>
> --
Some of the 13 x 8s did have, and I seem to recall that some also had a
bracket fixed across the centre, which held a pair of black Mylar-coned
tweeters. The 13 x 8s that I used were the 'straight' bass version. I built
3 ways with them, using the matching EMI 8 x 5s for the mids, and they did
indeed (still do) have a whizzer cone in the middle. The mids are separately
baffled by their own sub-enclosure behind them, and inside the volume of the
bass cabs. The tweeters are Eagle aluminium domes. Very bright sound. I
picked them because I loved the clarity that they added to the top end of
the sorts of music that I was listening to back then - mainly heavy and
progressive rock. The crossovers are also Eagle. They used to make some good
products. I guess they don't exist any more. :-(
Arfa
Arfa Daily
"David Nebenzahl" <nob...@but.us.chickens> wrote in message
news:4c508fbb$0$2390$8226...@news.adtechcomputers.com...
> On 7/28/2010 12:10 PM Ron spake thus:
>
>> On 28/07/2010 17:50, Arfa Daily wrote:
>>
>>> I've just been listening to a CD through them. They sound nice, and
>>> very smooth with a very flat and stiff sounding bass. Quite easy on
>>> the old lug-holes, but I'm not sure that I would rate them as 16
>>> grand more easy than my home-built EMI 13 x 8 cabs from the 70's
>>> ... :-)
>>
>> Ahh 13 x 8's did they have the whizzer cone in the centre?
>
> Whizzer cones? Are you pulling our legs?
>
> I always associated whizzer cones with the know-nothing, 6x9 oval weird
> expensive speakers to throw in the back of your car market, not anything
> near audiophool quality. Am I wrong?
>
>
I wouldn't say that these speaker cabs, which I constructed when I was just
married and struggling for cash back in the early 70's, are especially
brilliant. They were constructed to the basic shape and volume specified by
EMI, and they gave - well actually still do give - a sound which I found
pleasing enough, and suited the types of music that I was listening to at
the time. The mids that EMI made as matching units to the bass drivers, had
a whizzer cone which was claimed to significantly increase their high
frequency response. Whether that was actually true or just a gimmick, I
never really investigated, as I fitted my cabs with a surface mounted dome
tweeter, the response of which would easily drown any top coming from the
whizzer cone on the mids.
These speakers certainly sounded better back then than pretty much anything
that came as standard with any kind of hifi rig, and were much better than
anything that I could have afforded off the shelf, as 'proper' hifi
speakers. To be honest, they still sound better even now, than much of the
crap that is sold as general hifi.
As to the audiophool thing, I'm certainly not one of those. I don't believe
at all in the purported system 'improvements' to be obtained by the fitting
of Monster hook up cables, mains filter blocks, oxygen free speaker cable as
thick as your arm and all that stuff. By the same token, I'm not what I
would describe as an audiophile either. Just someone with a reasonable ear,
and a better than Joe Average understanding of the principles of audio
reproduction, and a firm believer in the laws of diminishing return, which I
think is amply demonstrated by the apparent value of these Resteks ... :-)
Arfa
Archon
> Some of the 13 x 8s did have, and I seem to recall that some also had a
> bracket fixed across the centre, which held a pair of black Mylar-coned
> tweeters. The 13 x 8s that I used were the 'straight' bass version. I
> built 3 ways with them, using the matching EMI 8 x 5s for the mids, and
> they did indeed (still do) have a whizzer cone in the middle. The mids
> are separately baffled by their own sub-enclosure behind them, and
> inside the volume of the bass cabs. The tweeters are Eagle aluminium
> domes. Very bright sound. I picked them because I loved the clarity that
> they added to the top end of the sorts of music that I was listening to
> back then - mainly heavy and progressive rock. The crossovers are also
> Eagle. They used to make some good products. I guess they don't exist
> any more. :-(
>
> Arfa
Should have built the , Kef B139, B110, T27's, built them in 1976, still
using them, still sound awesome!
JC
Archon
Arfa Daily
"Archon" <Chipbee4...@yahoo.com> wrote in message
news:_a64o.495695$Jq1.2...@en-nntp-05.dc1.easynews.com...
Friend of mine has just built some ! He bought all the drivers way back
then, and has had them 'stored' ever since from lack of finance, skill, and
will. Then, last year, he decided to build them, so had a local joinery
place cut all of the boards for him. The job still took him the better part
of a year, but he finally finished them, and was then extremely disappointed
with the sound. However, he persevered with them, and eventually found that
they were extremely critical of their positioning in the room, and performed
loads better, when elevated from the floor. He now alternates between his
Quad electrostatics, and the Kefs, depending on what he is listening to.
Arfa
Ron
> On 7/28/2010 12:10 PM Ron spake thus:
>
>> On 28/07/2010 17:50, Arfa Daily wrote:
>>
>>> I've just been listening to a CD through them. They sound nice, and
>>> very smooth with a very flat and stiff sounding bass. Quite easy on
>>> the old lug-holes, but I'm not sure that I would rate them as 16
>>> grand more easy than my home-built EMI 13 x 8 cabs from the 70's
>>> ... :-)
>>
>> Ahh 13 x 8's did they have the whizzer cone in the centre?
>
> Whizzer cones? Are you pulling our legs?
>
> I always associated whizzer cones with the know-nothing, 6x9 oval weird
> expensive speakers to throw in the back of your car market, not anything
> near audiophool quality. Am I wrong?
>
>
the 60's tho they were still around well into the 70'. I don't think EMI
ever claimed that they were 'hifi'
However, you still see whizzers on modern speakers, Eminence still make
them. I was interested to see a speaker with a 'dual cone' in a modern
Mark Bass combo only yesterday.
Ron(UK)
--
I am using the free version of SPAMfighter.
We are a community of 7 million users fighting spam.
SPAMfighter has removed 1589 of my spam emails to date.
Adrian Tuddenham
I'm using individully amped 2 x B139, B110, SEAS H881 in
totally-enclosed cabinets as monitors for pipe organ recordings. They
weigh 50Kg each (including the amplifiers) and are of 'sandwich'
construction of 9mm plywood, roofing felt and 19 SWG galvanised steel
plate.
We arranged an impromptu test which fooled the organ tuner into thinking
he was actually hearing the organ.
--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
Arfa Daily
"Adrian Tuddenham" <adr...@poppyrecords.invalid.invalid> wrote in message
news:1jme00i.1ow576w1bfmub8N%adr...@poppyrecords.invalid.invalid...
Love it ! Is this just church organ recordings, or theatre organs as well ?
We had a beautiful three manual Wurlitzer in town for many years until the
venue where it was housed, closed down. It had one of the best sounds I have
ever heard, and the resident organist played it like it was an extension of
himself. Shades of Dixon and Torch. I had a couple of CDs that were sold to
visitors to the venue, but all I have left now, is the case to one of them.
They were proper commercial discs, but I have been completely unable to
trace them anywhere since. Sadly, as the venue is now gone, there's no
chance of ever replacing them, I fear. Don't suppose you've ever come across
Sovereign Music, have you ? I wonder who bought that instrument when the
place closed, and where it is now ?
Arfa