Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Cabinets-Speakers => Topic started by: dwdw on April 15, 2009, 08:43:52 am
-
I have a 12" speaker from a Baldwin organ. Its an 8 ohm (measured as 6.4 ohms DC) is there any way to come up with the wattage?
The ceramic magnet is 3.3" in diameter, and has a small cone sticking out of the large cone (we called them wizzer cones)
The wire feeding the speaker was 14 guage.
The output amp is transistorized with house numbers as the speaker. The 2 transistors look as though they could be 2n3055 or similar but RCA. Is my guess that it would be 20-25 watts---close?
The speaker could be 25watts but not any more?
The reason is I'm using it with a 35-45 watt amp (2/7868 output tubes)
Any rough ideas would be welcomed!
Thank You
dwdw
-
Measure the voice coil diameter.
1" = 10W - 15W max, 1 1/4" = 15 - 20W, 1 1/2" = 20 - 30W for MI applications.
-
Thank You for the reply:
The smallest part of the speaker cone is about 1 1/4 to 1 3/8 " about 20 watts
There is an accordian folded ring around that location ,
I assume that just holds the voice coil in the center of the magnet.
Thanks for the GREAT help.
dwdw
-
>There is an accordian folded ring around that location.
Sounds like you're looking at the spider. It works with the surround (a similar structure around the circumference of the cone) to allow the cone structure to move and produce sound waves as the voice coil moves around the pole piece according to the changing polarities of the AC signal being applied. Here's a good interactive diagram. (http://www.bcae1.com/speaker.htm)
-
That was very enlightening. I thought thiis guitar amp stuff was just a piece of cake! I now know how my wife feel when I try to explain how a car starts and moves! When I was a youngster I had an IQ of 138 and it showed but now it can't be 90.
I sure opened Pandora's box with this new I almost said hobby but its a learning challenge.
I have to thank everyone that has helped me, at another site they just said for me to read this Naval electronics course and stopped helping , This site ROCKS. :)
dwdw
-
Hey man... We're here for ya!
-
Your testing my age, memory and sobriety at this. . . never mind, got it. These are called co-axial speakers: woofer + midrange and/or tweeter mounted concentrically on one frame (crossover network required). These were popular in the 50's and 60's as hi-fi speakers. They still have niche-market popularity on various diy hi-fi forums. However this seems to have a strong nostalgic component and to my knowledge no one builds co-axial speakers for hi-fi use anymore. (Still used in some automobile sound systems.)
The point is that they are h-fi speakers, or perhaps more appropriately, "drivers". For a variety of (googleable) reasons, hi-fi speakers are generally considered to be unsuitable for use as musical instrument speakers.
-
Thank You for more information, this has no crossover its just an extension of the voice coil as though it was a cone about 2" tall and 3 1/2 " in diameter, like if you took an ice cream cone and cut about 2" off the pointed end and glued the remainder to the large cone as an extension. As you said the coaxial are 2 concentric speakers with a crossover.
When I get done with this amp I'll give it a try nothing to loose.
Thanks
dwdw
-
Thats called a whizzer cone I believe, its used to reproduce a little midrange or treble. It looks like someone glued on a small cone on top of a regular speaker right?
Regards,
Dyna
-
You got my interest up and did a little web searching and found a few things about the wizzer cone. A cheap way of extending the midrange, thas why there was a tweeter in the cabinet. One idea was to use an exacto knife and caefully cut it free and it will work as a guitar speaker with clean sounding amp. Its worth the effort. Here is a picture.
Also Jenson in the 70's used thes and they worked well.
Thank You
dwdw
-
Yep, that's what a whizzer cone is and does- it acts just like a miniature speaker. The smaller diameter acts to disperse the highs better than the larger diameter woofer cone does. Above about 1,000 Hz a 12" cone becomes sharply directional (called beaming, because the big cone throws high frequency sound waves just like a flashlight throws light in a round concentrated beam). In the early 70's and prior, tweeters were small two or three inch cones. The dome tweeter was a brand new invention and not widely available. Horns came in all shapes and sizes by this time. Utilitarian (think old Newcomb record player) school and commercial A/V gear was built cheap, and gluing a little paper cone to the voice coil dust cap was cheaper than adding a tweeter and a 5mfd nonpolar cap. It wasnt as pretty as an aluminum dust cap, but actually worked better if the design was thought out correctly. Lots of times though, the little cone's glue joint failed and it started buzzing instead of singing. Hence the 'whizzer' nom de' vulgar. Some manufacturers even went so far as to list the mechanical crossover frequency as if it was a genuine two way speaker. Hell, even Fosters, Jordans, and Lowther drivers use whizzer cones to get up to the 14K~20Khz range, an' they ain't cheap!
Most Utility speakers from that time would handle 20-30 watts just fine.
-
The driver in that picture looks like an old EV Wolvarine- vintage hi-fi. I'm gonna try to stay clear of 'hi-fi vs geetar' speaker debate. My opinion is to use what sounds good to you.
-
> The 2 transistors look as though they could be 2n3055 or similar but RCA. Is my guess that it would be 20-25 watts---close?
I've seen 2N3055 pairs pushed to 75W.
I've seen them, because they fail often at that level.
I'd have to sniff your dust to guess how courageously they were driven.
And if not marked "2N3055", they could be much wimpier parts in TO-3 cases (before plastic-pack, we put 15W parts in TO-3), or they could be some bigger parts. In a complete organ, not subject to user-shorts or prolonged overdrive, I could imagine 100W from a pair of big-die TO-3s. Heck, I have a Yamaha bass-amp, honest 100W sine power, just one pair of TO-3 outputs, no trouble.
In any case, there is a major disconnect. Organs don't distort. Guitars do. 20 sine-wave watts in organ duty is never much over 20W of heat for more than a part-second, and likely under 10W average in loud passages. A guitarist will linger at 10W much of the night, blip past 20W, and may hold 35 heat-watts for a few distorted power-chords. One night of that can destroy a speaker which lived for years on the same amp in organ-duty.
What FYL said. (http://www.el34world.com/Forum/index.php?topic=6531.msg57409#msg57409) Older shellac coils 1"-1.25" can take 10W-20W of heat. For undistorted full-orchestra playback, you can use 50W-100W amp. For distorted guitar, 5W-10W is safe, maybe 7W-14W depending how hard you whang it and how much your amp sags.
Stick this guy in a Champ. There's loads of 50W gitar-rated Twelves on the market, that's what you should be using.
Wizzers are cheap-tricks. Nearly nobody bothers to get it right, nor has the production control to keep it right. I spent a LOT of time with E-V SP12... they made an honest try, but I can still hear those wizzers wizzing their own song no matter what is playing. I've lived with dozens of low-price wizzers and got what I paid for. I have not worked with Lowthers.... I believe a good wizzer is possible, just not easy, and that at usual price/quality tradeoffs, a Three and a cap is a better deal.
FWIW: the Curvilinear cone on JBL D-130 does pretty much what the wizzer on E-V SP15 did, only better. Adds an octave of dispersion. On full-range music, you still want a tweeter, so why futz-around?
> an old EV Wolverine
Yes, it does. As hi-fi speakers, the SP12 and the 8" Wolverine sounded a lot like guitar speakers. It could be either/or. Certainly not a modern-fad hi-fi, and certainly not any of the several styles of guitar speaker, but usable for either and sometimes amazingly "right" for certain sounds.
-
I really appreciate the help and the boat loads of information!
I can tell the people here are really in the KNOW and LOVE the guitar sounds.
I would if I could, spend more on this project I would but my resources are limited. This project is a joint project with my grandson, he will be graduating grammar school in the end of May. This will be my gift to him to help him along with his LOVE of playing a guitar.
OK now back to work time is a wasting.
Thank You for understanding.
dwdw :)
-
Thank You for more information, this has no crossover . . .
The "crossover network" may have been simply a capacitor, feeding the tweeter cone of this speaker. If there are separate electrical hook-ups for the 2 portions, or drivers, of this speaker, then a crossover is needed. Without it, too much power may flow to the tweeter and burn it out.