Speaker for an M20E

[Ned Gravel]

Some of you will recall that I was going to do some minor electrical work.  I started two weeks ago and Clarence at Tri City is letting me come in and do the dogwork to accomplish this.  I took out the headliner to replace the broken rheostat for lights.  I bought the LED replacement kit and I replaced all of the circuit breakers with current parts.

I found that the dome light was disconnected and speaker was gone.  The 20 Amp circuit breaker is only connected to my Trimble GPS.  The ADF circuit breaker also runs the NAV/COM (5 amp breaker so I am going to put that radio on the 20 amp breaker).  COM 1 is not attached to a circuit breaker at all - so that is going to change.  I am also going to change out my NAT 80 and NARCO CP135 combo for the Garmin 340 I bought at Oshkosh last July.

I am also going to plumb in the line for a new 406 ELT so that by the time we leave for Western Canada (Russ and Jezzie have been warned), my bird will be safer for the trip.

I connected up a new-old-stock dome light and I am replacing the old fiberglass insulation behind the headliner with some new stuff from Spruce.  But....and here comes the question.....  What are the tech specs for a speaker to put into the headliner? 

I am thinking 3W or less, 8 Ohms, probably automotive lookalike that works in 14V.  Any words of wisdom from the group?

[N601RX]

Look at the specs for the audio panel.  I think it is 4 or 8 ohms and up to 10 watts for Garmin.  The speaker doesn't have a voltage rating.

[carusoam]

One mystery (misery) solved....

"pin-out" diagram for Narco CP135 does not have a speaker as part of it's repetoire.....

http://www.narco-avionics.com/installpages/CP135-Pinout.pdf

CP136, however does......

http://www.narco-avionics.com/installpages/CP136-Pinout.pdf

See pin #4 "cabin speaker"

Ned, you gave me another reason to dislike the Narco(s) even more........

Anyone interested in CP136?, I still have one.....

Sorry, couldn't find a reference to 4 or 8 ohms for the speaker.  12V automobiles, usually use 4 ohm.  House Audio usually uses 8 ohm.  aircraft spruce shows 3.2 ohms (input impedance).....

spruce:  http://www.aircraftspruce.com/catalog/avpages/quam_speakers.php  $30 USD.

The original specs are probably in the electrical diagram in the M20 Parts Manual....

http://www.67m20e.com/M20E_manuals.htm - Thanks to Brian at Flight 2000.....

I am on a slow wireless so I was unable to go to the wiring diagrams......

I like Mike's idea best, Check your new equipment requirements and there is no need for what used to be hiding up there....

Best regards,

-a-

[N601RX]

https://buy.garmin.com/shop/store/assets/pdfs/specs/gma340_spec.pdf

[Ned Gravel]

Thanks folks.  Good advice.  Got the Garmin specs and now I also know why the speaker was missing.  Good riddance to that Narco audio panel. 

While the 340 allows for an 8 Ohm impedence speaker, I am going to go with the 10 watt 4 Ohm one from Spruce.  At least it is a/c grade and will handle all of the power put out by the 340.

Handed out some shocking news to my best friend today though.  She is going to dust off her radio operator's licence since the 340 allows her to talk to FBOs etc on one of the two COMs while her onboard Mooney Driver is busy talking with ATC.

[acronut]

If I'm reading this right I'd be careful about the circuit breakers.  Usually radios are on low 1-5 Amp breakers.  If that's whats recomended by the manufactured I'd stick with it.  Having a radio on a 20Amp breaker isn't going to do much to protect it.  Sounds like your on the right track to a nicer setup.  Good luck

Kendal

[tony]

when you design an aircraft, the circuit breakers are sized to protect the wire, not the device on the end of it.

[acronut]

Quote: tony

when you design an aircraft, the circuit breakers are sized to protect the wire, not the device on the end of it.

[Ned Gravel]

Again, good points all.  I was aiming at providing the NAV/COMS with the juice required to transmit because, of all the avionics, they should be drawing the most as they are the only transmitters in the lot. But the advice on not going with the higher rated breakers is supported by the OEMs. 

Interior lights take juice too and they are on a 10 amp circuit breaker. At the end of this little piece of work, the only incandescent bulbs in the cockpit will be in the whiskey compas, the map light, the gear lights, the check-which-tank-you-are-on under-panel light, NAV CDI light, new dome light, and the map light.  Instruments already have Nulites.

My apologies if this gets technical, but I have not had this much fun in electrical things since I was in officer training and troubleshooting SB 86's and NT 701's (see if any of you know what those are).

I have gone back to the electrical system drawings and Mooney indicates COM 1 on the same circuit as the speaker without recommendation for the size of the breaker.  "As needed" is the term used for the circuit breaker rated size and any other NAV/COM set up.  They prohibit the addition of other radios to the circuit for COM1.  COM 1 is connected straight to the bus and will get a new 4 amp breaker on AWG #16.  COM2/NAV1 will get a 7 amp breaker on AWG #18.  The speaker will be rewired to be driven by the 340.

My current intercomm and audio panel breakers are separate on that bus and rated for 1 and 5 amps respectively.  Their disappearance and replacement by the 340 will free up one space and I can put a 4 amp breaker in for COM 1 to replace the 1 amp for the old intercom.  The pinouts for the 340 call for a 5 amp breaker on AWG #22.

Serious high-current devices (fuel pump, pitot heat, external lights, etc) are on another bus and that one has been correctly configured with appropriately rated breakers (current technology ones) and I am good with that. 

Sorry, no pictures for this, unless you want me to start posting pinout diagrams.

[JohnnyM]

Ned,
I am necroing this thread to ask how that 6" speaker fit in your 65 M20E. I know it's been 12 years, but perhaps you will remember it with how much fun you were claiming to have!

I have the interior of a 66 M20E and the speaker has to be original if not 40+ years old. I am upgrading avionics as well and was looking for a speaker to swap in, but the original appears to be a 4" model, so I was wondering how much coercing you had to do to get it to fit, or if it was pretty straight forward. 
 

[N201MKTurbo]

57 minutes ago, JohnnyM said:

Ned,
I am necroing this thread to ask how that 6" speaker fit in your 65 M20E. I know it's been 12 years, but perhaps you will remember it with how much fun you were claiming to have!

I have the interior of a 66 M20E and the speaker has to be original if not 40+ years old. I am upgrading avionics as well and was looking for a speaker to swap in, but the original appears to be a 4" model, so I was wondering how much coercing you had to do to get it to fit, or if it was pretty straight forward. 
 

I have some of those speakers if you want one.

[N201MKTurbo]

[Ned Gravel]

10 hours ago, JohnnyM said:

Ned,
I am necroing this thread to ask how that 6" speaker fit in your 65 M20E. I know it's been 12 years, but perhaps you will remember it with how much fun you were claiming to have!

I have the interior of a 66 M20E and the speaker has to be original if not 40+ years old. I am upgrading avionics as well and was looking for a speaker to swap in, but the original appears to be a 4" model, so I was wondering how much coercing you had to do to get it to fit, or if it was pretty straight forward. 
 

Still works good. Don’t use it much, but it is there if I need it

[JohnnyM]

I'll send you a PM.

[JohnnyM]

Still works good. Don’t use it much, but it is there if I need it

Thanks for the response. I was mostly wondering about the fit since the spruce speaker appears to be slightly larger than OEM.

[Ned Gravel]

1 hour ago, JohnnyM said:

21 hours ago, Ned Gravel said:

Still works good. Don’t use it much, but it is there if I need it

Thanks for the response. I was mostly wondering about the fit since the spruce speaker appears to be slightly larger than OEM.

Mine fit fine.