[rollei_list] Re: Completely OT- Loudspeaker info a pop up question

Ruben,

Hoo boy!!  We gotta go BEFORE Audio 101.  Impedance is NOT the
same as pure resistance, it is frequency dependent.  The LAST thing you
want to do is put a resistor in series with a speaker.

Please don't screw with the Kef or B&W speakers!  They are PFG as
they are.  It takes an expert to improve them.

Jerry

Ruben wrote:

> I see that you are talking loudspeakers and I have a couple of questions
>
> 1. On an amplifier it is often statet to use only 8 ohm speakers - I I have
> a speaker unit and it mesures 8 ohm when an Ohm meter is attached to the + -
> I guess it is ok - but what if there are more thant one speaker ?  or my
> speaker set is only 4 Ohm - can you just put a resitant 4 ohm on the wire
> and everything is cool ???
> 2. I have several boxes with speaker units, from jbl, cervin vega, pearless,
> b&o, kef and b&w - I would like to built new cabinets and could use a guide
> to both "spliting filters" - cabinet acoustics etc. Can you recommend books
> on do it your self high end speakers ??
>
> thanks and sorry for jumping into your thread
>
> Ruben
>
> ----- Original Message -----
> From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
> To: <rollei_list@xxxxxxxxxxxxx>
> Sent: Wednesday, February 16, 2005 12:30 PM
> Subject: [rollei_list] Re: Completely OT- Loudspeaker info
>
> >
> >
> > -----Original Message-----
> > From: "A. Lal" <alal@xxxxxxxxxxxxx>
> > Sent: Feb 15, 2005 10:18 PM
> > To: rollei_list@xxxxxxxxxxxxx
> > Subject: [rollei_list] Re: Completely OT- Loudspeaker info
> >
> >
> > Jerry, a bare ribbon would in fact behave like a dipole. However, in
> > many designs material is put on othe back side to try to damp out
> > resonances.
> >
> >   There have been ribbon speakers that used an impedance tube at the back
> > of the ribbon similar to the method used by RCA for directional
> > microphones. For a ribbon speaker an absorptive box probably would do. The
> > path length around the ribbon structure is what controlls the minimum
> > frequency it can radiate with any efficiency. This is different from
> > damping of resonances.  What is needed if both sides of the speaker are to
> > be open to the air is a large enough baffle so that the path around it is
> > longer than a half wave at the minimum frequency of interest.
> >   It seems to me that what the "dipole" speaker people are doing is an old
> > trick of exciting the reverberant field with the back radiation.
> >
> >
> >
> > --
> > Richard Knoppow
> > dickburk@xxxxxxxxxxxxx
> > Los Angeles, CA, USA
> >

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