Hoffman Amplifiers Tube Amplifier Forum

Other Stuff => Cabinets-Speakers => Topic started by: chocopower on June 05, 2011, 06:22:25 am

Title: Unknow speaker. Power handling
Post by: chocopower on June 05, 2011, 06:22:25 am
Hellow,

are there any simple test to measure the power handling capability in a speaker.
"Simple" means: No osciloscopy. No signal generator....

I know, i know.
"play it hard till it seems to be in problems"
I would like to use that method as last solution.

Pics attached. Maybe some one know the logo or have some information.
Is 12" - 16ohm
Title: Re: Unknow speaker. Power handling
Post by: LooseChange on June 05, 2011, 07:34:05 am
Cool looking speaker. Size matters. Looking at the magnet size and age (can't see the voice coil but I figure it's small too) I would guess 15 to 25 watts max.  Age is another factor. Could be a 25 watt speaker but crank it up with a 10 watt amp and she could blow.
Title: Re: Unknow speaker. Power handling
Post by: FYL on June 05, 2011, 08:00:18 am
Quote
are there any simple test to measure the power handling capability in a speaker.

You can somewhat guesstimate it by measuring the voice coil diameter (usually sightly smaller than the glued dust cap) and looking at the motor assembly as well as the suspension.

For pre '60 12" speakers used in MI applications:

1" => app. 5 watts (very small magnet, one-piece paper cone with an untreated pleated surround) to 10 watts (medium-sized magnet, treated surround)
1.25" => 10 to 20 watts
1.5" => 15 to 30 watts (large magnet, glued fabric surround)
2" => 25 to 60 watts

Post '60 speakers usually have higher ratings, 50 to 100% depending on brand/model/... OTOH, most vintage paper cones and surrounds have become quite brittle and fragile, with very poor real-world power handling.

Can you post higher resolution pics of the logo as well as of the markings on the basket?

Title: Re: Unknow speaker. Power handling
Post by: Tiny_Daddy on June 05, 2011, 09:19:36 am
Looks like an extension speaker for a movie projector. Any brand name?
Title: Re: Unknow speaker. Power handling
Post by: chocopower on June 05, 2011, 09:29:11 am
those are seller pics.

When it arrives i post some more.

thanks!!!
Title: Re: Unknow speaker. Power handling
Post by: Frankenamp on June 05, 2011, 12:48:18 pm
Quote from: Tiny_Daddy on June 05, 2011, 09:19:36 am
Looks like an extension speaker for a movie projector. Any brand name?

Correctamundo! It is an extension speaker of some sort. It looks to be no earlier than late 50's styling. If it is a 12" driver I would guesstimate from the size of the motor that the VC is 1.25 to 1.5". Given the age, I wouldn't hit it with anything much over 15 watts. Ten really distorted, or 20 sqeaky-clean watts.

EDIT: Looking closer, at the second picture It seems to be a "Peerless" brand driver. Peerless is a pretty good Danish brand. What you have is a higher-end utility speaker.
Title: Re: Unknow speaker. Power handling
Post by: kagliostro on June 05, 2011, 01:43:39 pm
Which a nice future combo .............. :icon_biggrin:

Kagliostro
Title: Re: Unknow speaker. Power handling
Post by: tubeswell on June 05, 2011, 04:49:03 pm
I vote for 15-20W judging by the size of the magnet in relation to the frame
Title: Re: Unknow speaker. Power handling
Post by: chocopower on June 05, 2011, 08:13:13 pm
Quote from: kagliostro on June 05, 2011, 01:43:39 pm
Which a nice future combo .............. :icon_biggrin:

Kagliostro

You read my brain!!!   :icon_biggrin:

A vox AC15 or a 5E3 tipology amp will be a nice partner for this cab.
Title: Re: Unknow speaker. Power handling
Post by: rafe on June 05, 2011, 08:34:09 pm
That would make a nice looking Vibro-champ  :worthy1:
Title: Re: Unknow speaker. Power handling
Post by: chocopower on June 05, 2011, 10:10:48 pm
Now i need to think about the best way to put the controls (vol, tone...) with minimun cab damage.

Ah! back side!



Title: Re: Unknow speaker. Power handling
Post by: chocopower on June 06, 2011, 08:51:28 am
Cab at home.

is mark with:

"P120FM  -  16ohm"

Googleing:
Peerless  P120FM: 30,5cm - 8Ohm - 20Watt - Fres40-16kHZ - Alnico - Doppelkonus

I tried to get out the bell without succes.

Title: Re: Unknow speaker. Power handling
Post by: FYL on June 06, 2011, 03:46:18 pm
Quote
Peerless  P120FM: 30,5cm - 8Ohm - 20Watt - Fres40-16kHZ - Alnico - Doppelkonus

A dual cone wide range speaker designed for hifi/PA applications. Could be too smooth and too linear for MI.

The 20-watt power rating should be halved for MI.

Title: Re: Unknow speaker. Power handling
Post by: jeff on June 06, 2011, 04:39:00 pm
Cool looking cab.

 It always confused me that they mark a speaker with the one thing you can test for easily with a multimeter(Ohms) but don't mark the thing you can't test for. :w2:
Title: Re: Unknow speaker. Power handling
Post by: chocopower on June 06, 2011, 05:01:12 pm
Quote from: FYL on June 06, 2011, 03:46:18 pm
Quote
Peerless  P120FM: 30,5cm - 8Ohm - 20Watt - Fres40-16kHZ - Alnico - Doppelkonus

A dual cone wide range speaker designed for hifi/PA applications. Could be too smooth and too linear for MI.

The 20-watt power rating should be halved for MI.

IŽll test it tomorrow with diferent amps.
If the speaker is not ok for guitar use, iŽll try with some celestions i have around.
I love the cab look so much!
Title: Re: Unknow speaker. Power handling
Post by: chocopower on June 06, 2011, 05:01:52 pm
Quote from: jeff on June 06, 2011, 04:39:00 pm
Cool looking cab.

 It always confused me that they mark a speaker with the one thing you can test for easily with a multimeter(Ohms) don't mark the thing you can't test for. :w2:
Never thought about it, but you are on right.  :dontknow:
Title: Re: Unknow speaker. Power handling
Post by: chocopower on June 06, 2011, 05:35:34 pm
Eii!!

is perfect for my last baby!! (with a diferent speaker, i know)

http://www.el34world.com/Forum/index.php?topic=11677.0 (http://www.el34world.com/Forum/index.php?topic=11677.0)