[Ron Ramirez]

Okay, so I have this Masterpiece VI sitting here.

The original Jensen Super-Giant is long gone and quite possibly sitting in the home of some audiophool in Japan or Hong Kong.

Not long ago, a Super-Giant sold at Estes for $9000, a new record:
http://antiqueradios.com/forums/viewtopi...9#p1810749

Then last week, I caught an auction on eBay for a very similar 18 inch Jensen with pedestal, not a McMurdo Silver speaker but nearly identical. It sold for $6,700!
http://www.ebay.com/itm/330874469013?nma..._cvip=true

I had an opportunity to buy an original some months back from a private collector for less than the going rate, but still in four figures. My first reaction was to go for it, but after thinking it over, I passed - and bought my 2000 Ford Excursion instead.

I would really like to have an 18 inch speaker in my MP VI, but it doesn't have to be a Jensen Super-Giant. And I am seriously considering building my own coaxial speaker (much like the Scott 800B speaker) using a modern 18 inch woofer with a frequency range of 20 to 6000 Hz, and using metal strips to mount a small tweeter in the center with a frequency range of 2000 to 15000 Hz; connecting them to a suitable 2-way crossover; and driving them with a high fidelity Edcor audio output transformer.

This would require power resistors to replace the original field coils, of course.

Yes, I know that doing this would reduce the value of my set, but it will not be seen unless I show off the back of the set; and it would be a completely (and easily) reversible mod.

I could do all of this for around $150-200 - much easier on the old wallet than spending thousand$$$$ on the proper original Jensen.

What are your thoughts? Is this heresy? Am I crazy?

(Actually, I think spending four figures - getting close to five figures - for a speaker is crazy.)

[morzh]

It's not heresy. And it will probably sound as well. All depends on your goal: if it is to eventually make your McMurdo to sing well, this is one thing, if it is also to show it off (not that there is anything wrong with it - it is a normal part of col'lecting things, to show them off) - you need the original or something close to it.

I respect either approach as long as it does not become a psychiatric issue.

[Paul Philco322]

When you are dealing with issues that require a significant an investment I would defer to the owner of the sets judgement. Many collectors strive for authenticity but unless you have won the LOTTO there are always limits. A humble collector who would like to listen to his/her set cannot be faulted because he/she has to eat and pay rent.

So as long as one is being true to his/her philosophy their work should be respected. In my humble opinion there are a lot of bad feelings created sometimes because a collectors' wish to judge others too harshly, the hobby should be enjoyable, a guy/gal should not be made to feel inadequate because someone else chooses to tell them they did not do it "right".

Now I have to go paint a model 90 florescent pink.

Paul

[37silverstreak]

In my very humble opinion, I would say that as long the modification is reversible if an original speaker is found. Go for it! $150-$200 makes a whole lot more sense to me than spending that much for a speaker!!!!! If you can make the radio perform close to as it should without permanently altering it's design, who cares what others might think!
Kevin

[Steve Davis]

A few thousand for the speaker then several thousand for the divorce.

Steve

[Arran]

You could try finding a large electrodynamic of another brand, I have a 15 inch Magnavox that came out of a Northern Electric/American Bosch console. I don't know if Magnavox, Utah, Quam, Rolla, or any of the others made 18 inch pedestal speakers though.
Out of the old American speaker manufacturers Jensen is the only one that seems to have that sort of cult following among audiophools, probably because it's one of the last ones standing, sort of like brand Z was to TV sets and other consumer electronics. Not to bash Scott or McMurdo-Silver but quite frankly any audiophool that thinks an electrodynamic would deliver higher fidelity sound then a PM dynamic must have cotton shoved up their ears.
You could go with a PM replacement, but I would suggest using proper filter chokes in place of wire wound resistors, not only do they not produce heat but they are far more efficient at filtering AC ripple without causing a voltage drop under load.
Regards
Arran

[Eliot Ness]

First of all it really hacks me off that these classic radios are being raped of their speakers so they can be shipped to some fool in Asia.

I also think it would be foolish to spend that kind of money on a speaker, so your idea has merit and is sure worth a try. The ironic part is your 'economy' speaker will most likely have higher fidelity that the high dollar originals being sent overseas.

[Arran]

No irony about it, they are called "audiophools" for a reason, it's the same logic being a brand X 5U4 making the amp sound better then a brand Y 5U4. If they knew anything they would demand older British made loudspeakers over a Jensen any day, Jensen had some nice speakers but they also produced a lot of mass market junk too. On the other hand now that Europe is imploding economically one of the big markets for Asian goods is going with it.
Regards
Arran

[TA Forbes]

God made radios to be turned on and listened to. They are not door stops or plant stands.

I say go for it! From the listening-end of the radio no one will know the difference, and you will be able to enjoy the Scott doing what it does best!!!

[Ron Ramirez]

Thanks to everyone for your input. I've ordered a new 18 inch woofer, tweeter and 2-way crossover board from Parts Express. This weekend I'll see about getting some steel for coaxial mounting of the tweeter on the woofer. Later on, I'll order a suitable audio output transformer from Edcor, and get a metal box from somewhere to mount the crossover into, and the output transformer on.

The original speaker had a dual field coil - 680 ohms and 5000 ohms 8000 ohms (edit by me). From careful study of the schematic, it appears that the 8000 ohm section could be deleted as it served only to energize the original speaker. The 680 ohm section was used as part of the power supply. I didn't see any chokes from Edcor or Hammond with a DC resistance close to 680 ohms that could handle a fair amount of current.

E.H. Scott's model 800B originally used a 15 inch coaxial Jensen speaker, which had a dual field coil setup very similar to the MP VI. Later, this electrodynamic speaker was changed to PM. The PM replacement had a 680 ohm 675 ohm resistor mounted in back to replace the 675 ohm section of the field coil! And the 5000 ohm 9000 ohm section was deleted entirely. So...I'm thinking that, if it worked in the Scott 800B, that the same design should work in the MP VI...that is, using a power resistor to replace the 680 ohm field and eliminating the 5000 ohm 8000 ohm field.

I had actually bought a Scott 800B speaker for the McMurdo, only to find that it was the later PM type. I'll be reselling it as I really want an 18 inch speaker in my McMurdo. If I used a 15 inch speaker, I would have to mount it on a board to fill the empty space, then mount speaker and board inside the McMurdo.

You get the picture...

[Chuck Schwark]

You have my vote too. Most reasonable alternative to
dropping your pants and bank balance.

And...like you say easily reversible if the impossible
actually happens to drop in your lap.



Mr. Bench

[morzh]

If this thing drops in your lap.....you won't be able to think of anything else for a while. I promise you.

[y2kbruce]

Ron-Interesting thread and I too say go for it. If your idea works, I think there are quite a few people also missing their 18" speaker and you could turn a profit by offering some of these retros as plug and play replacement speakers. I could even sell the 3 I have and replace them and pay off my mortgage all at the same time (Just Kidding !!)

Your explanation of the dual voice coil explains a similar problem i ran into on my MP v speaker-My repairman said one of the 2 voice coils was bad but the speaker still works fine. I could not understand why till i read your explanation.

[codefox1]

Well, I have a couple of 15" Rolas from Hammonds with 750 ohm fields sitting around doing nothing. Been a while, but if there is any interest, I'll take another look. You'll want to use at least 3/4" marine grade plywood if you build an adaptor.

One of my greatest (audio) thrills was when the old man of the distributer I workled at as a kid let me hook up a kick a** Mac and decent turntable to his pair of Electrovoice Patrician's and left me to play records for a couple of hours. My birthday, twas. Now that's 30 inch woofers. Made my ankles shake did. That and Nam, not to mention 2 ex wives, and it's a wonder I can hear at all. EEH?

Let me know.

[Ron Ramirez]

NOTE: I corrected my previous post above. The Jensen Super-Giant used in the McMurdo Silver Masterpiece VI has a dual field coil with DC resistances of 680 ohms and 8000 ohms.

Thanks, guys, for your additional input and comments. I do appreciate hearing from you good folks...and I also appreciate all the words of support for my idea!

Codefox, thank you for the offer, but I'm committed to the new 18 inch woofer and 4 inch tweeter now - in fact, they are supposed to arrive tomorrow. Maybe you can sell yours? All you have to do is hint at the magic words - "WESTERN ELECTRIC" - and you too can sell your speakers for thousand$$$!

Today, I went to Lowe's and bought a couple steel strips. I will be cutting these to fit, drilling holes in them, and using them to suspend the 4 inch tweeter in front of the 18 inch woofer, right in the center where it will not interfere with the woofer's cone. When done, it will look much like a Scott 800B speaker - a homemade coaxial.

I'll post pictures, too.

It is going to be a while before I know how well it sounds, though. I need to get the McMurdo's power supply chassis rechromed before I can rebuild it. And I will also have to rebuild the tuner. I am looking forward to this project!