Ribbon-on-a-stick, round 2

JohnR · « **on:** 4 Jul 2003, 01:06 pm »

Spent the evening messing about with my dipole prototypes. I've ditched the line of four Neo8 ribbons and am now using two plus a Neo3 PDR in an "MTM" configuration. The 12" Lambda dipole woofer is raised off the floor, which frankly sounds much better. The idea here was to see if I can get this configuration to sound OK, in which case I'll build a proper baffle for the lot. For a first guess at a 3-way crossover, it's not too bad at all

Arctos · « **Reply #1 on:** 5 Jul 2003, 12:09 am »

Looks pretty cool John,
Newbie question: What is a dipole speaker? (meaning what is the difference between a regular speaker [vented or sealed enclosure] and a dipole).

Thanks,

RDS

JohnR · « **Reply #2 on:** 5 Jul 2003, 12:50 am »

The term "dipole" refers to the radiation pattern, which is a figure of 8 towards the front and back of the speaker. Two characteristics are often cited as reasons for liking dipoles: less interaction with the room because of less radiation to the sides, and no box coloration -- there's no box. (You'll still get noise from the baffle if it isn't rigid though...)

On the other side of the coin (no free lunch), they "need" equalization to correct for various frequency response funnies caused by interaction of the front and back radiation from the speaker. I haven't put any EQ on these yet.

Electrostatics and Magneplanars are the best known type. Lately dipoles using cone drivers have become popular on the DIY scene in large part due to the generosity of Siegfried LInkwitz in sharing his knowledge: http://www.linkwitzlab.com/

The Linkwitz designs use quite complicated eq. My eq is going to be simpler. On the fullrange forum a lot of guys are just putting a driver on a large piece of plywood and enjoying that, that's an easy experiment if you have a fullrange driver lying around and a bit of space. 2' x 4' would work (the bigger the baffle, the less bass cancellation).

HTH

JohnR

TG · « **Reply #3 on:** 7 Jul 2003, 08:44 am »

Pretty cool, John

Are you going to drive these actively or passively?

JohnR · « **Reply #4 on:** 7 Jul 2003, 11:58 am »

I was wondering about that actually...

There's more drivers to go "under" these, they'll definitely be biamped. I'm leaning towards also going active on the crossover between the 12" midbass and the mid/tweets, it'll be a lot easier to adjust things and I have the amps anyway

Measurement gear needs to be made now...

KevinW · « **Reply #5 on:** 7 Jul 2003, 10:57 pm »

Quote from: JohnR

Measurement gear needs to be made now...

What exactly do you have in mind for measurement gear? I'm in the same boat...

I am this close to buying the Mighty Mike from Old Colony Sound labs...
http://www.audioxpress.com/bksprods/kits/kd-4.htm
Any opinions?

JohnR · « **Reply #6 on:** 8 Jul 2003, 01:53 am »

I'm gonna make this one

http://www.gti.net/wallin/audio/preamp2/preamp2.html

I have a Behringer ecm8000 to use for a mic. Another local chap is also interested, hopeuflly between us we'll get something going.

JohnR · « **Reply #7 on:** 8 Jul 2003, 02:28 am »

Or maybe not. The ECM8000 wants at least 15V phantom power. I thought this circuit had a 40V regulated supply but it must be another one I saw

JohnR · « **Reply #8 on:** 8 Jul 2003, 11:29 am »

I've been messing about a bit with the crossover to the ribbons and ended up losing track of where I was. I decided to sit down and redo it and take account of a couple things I ignored the first time, partly so I could use parts I had on hand. Here's the result, a nice simple

first-order crossover that I'll build tomorrow:

Supposed response:

I'm still doing it the hard way using a circuit simulator, the pressure to get some proper speaker design software is increasing...

beat · « **Reply #9 on:** 28 Jul 2003, 09:07 pm »

that is quite a cross over john!!!!
keep us posted on the outcome