Author Topic: RCA 6HF2 original speaker question any owners? (Pat you out there?)  (Read 5780 times)

bastardbus

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I have two RCA 6HF2 units.  They are nice pieces, with the infamous RCA SP-20 amp for power.  Anyhow....I have two of them here and am in the process of going through them both.  I have come across a bit of a conundrum, both seem to have had the original speakers (12" woofers) replaced.

I have the SAMS folder here and it shows this info.
-OPT has 3 taps 16,8 and 4 ohm.  The stock 6hf2 speaker plug uses the 8ohm hook up.
-According to the Sams the 6HF2 uses the (common to all RCAs of the time) stock RCA 12" speaker part number 100897 (marked 961628).

Issue I find is all the 961628 speakers I have measure 3.2 (4ohms)  as with the common set up (two tweeters and the 961628) they measure 3.2 as well.  You even see the back of the RCA extension speaker cabinets marked 3.2 ohms.

So my ?? is why would RCA use the 8ohm tap and run a 4 ohm speaker set.  Wondering if there is a mistake on Sams part...though I found the RCA 7HF2 (practically same as the 6HF2) uses the same set up according to RCAs own Service Data sheet.  Two different publications with the same incorrect info?

Anyhooo...both of my 6HF2s have different speakers.  One measures 3.2 ohms and the other dead on 8 ohms.  I do have a factory RCA 961628 I can use but it measures 3.2 ohms as well.  If someone else (pat???) has a 6HF2 maybe you can chime in on what your unit has in it for a speaker.  Hoping to see one with an untouched original speaker still in it.

T

Magnavoxland

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Re: RCA 6HF2 original speaker question any owners? (Pat you out there?)
« Reply #1 on: April 01, 2015, 11:18:33 PM »
The 12 inch woofer, and both the tweeters, should be 6-8 ohms in this unit.  From what I've heard, the woofer in the 6-HF-2 is a much heavier magnet woofer than RCA used in its other sets such as the SHF-3, 4 and 5.  Those used the standard Alnico woofers.

The RCA part number for the woofer is 100897 and it shows a Quam part number of 12A10X.  The other number you mentioned isn't shown in the Sam's photofact.

624Magnificent

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Re: RCA 6HF2 original speaker question any owners? (Pat you out there?)
« Reply #2 on: April 02, 2015, 06:37:58 AM »
One thing to think about is that measuring the resistance of a speaker with a multimeter is a good test to see if a speaker is blown. The resistance reading is based on DC current put out by the meter while the "rated" resistance of the speaker is based on it's DC resistance at "resonance" under an AC load. They do vary. I generally find that 8 ohm speakers read about 6 ohms with a meter.

The other thing to consider is that a factory crossover with options for 4, 8 and 16 ohms will have three different arrangements of capacitors and likely resistors that change the frequency cutoff of the tweeters, they generally don't affect the woofers. Woofers generally in older equipment are run "wide open" with no crossover elements. Later speakers in the component era sometimes have inductor coils on the woofers to limit highs.

It's also possible that the factory or an owner changed which terminals were used with these particular tweeters to adjust the crossover point to improve perceived sound quality.

It's entirely possible that the arrangement you have is correct "as sold" even if it doesn't match the paperwork. It's also possible that the tweeters were changed.
Tom

Pat L

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Re: RCA 6HF2 original speaker question any owners? (Pat you out there?)
« Reply #3 on: April 02, 2015, 07:13:46 AM »
I will post pictures of mine when I get a chance soon. I know mine is original except for the capacitors that I changed.

bastardbus

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Re: RCA 6HF2 original speaker question any owners? (Pat you out there?)
« Reply #4 on: April 02, 2015, 11:59:10 AM »
The tweeters are the correct RCA units and identical in both but the woofers have been replaced for sure. You can see the original proprietary speaker cables have both been crudely cut and spliced, and the woofers are after market garbage plain as day.  I know for a fact Nolan's was replaced as he stated he had removed and replaced the original speaker for some reason but is long gone now.

As far as the 6HF2s having heavier magnets, that is just an old wives tale and I have found zero proof of that.  We had a big in-depth discussion about this on the ARF long ago but I can't find the thread.  At the time of discussion there was only two known 6HF2s mine and Nolan's, both of which I currently own and neither have the original woofers.  The only documentation we found referring to what the original speaker installed in the 6HF2 was is the SAMS folder and it listed the speaker as having a 100897, which is the same  12"  inch speaker found in all New Orthophonic and Stereo Orthophonic RCA sets at the time. RCA and Sams lists them a RCA part number 100897 but they are only stamped with the 961628 numbers. If you take a look at a Factory RCA Service Data Manual, RCA lists the speakers as 100897 (961628).

I have the RCA Service Data for the RCA 7HF2 (the `57 version of the 6hf2) as well that states the same RCA 961628 being used .  There is a fellow in Cleveland with a RCA 7HF2 and has posted photos on ARF showing an original 961628 speaker installed too.  So that with the Sams info has me leaning towards the fact the that is the correct original speaker. 

What is throwing me off is the fact that the 6HF2 is tapped at 4,8,16 ohms they use the 8 ohm tap but ALL the 961628 speaker (and tweeter combos) measure 3.4 ohms (4 ohms).  Only thing I can think is I have seen the 961628 speakers with a suffix number after them. That suffix could possibly designate a variance in the impedance of the speaker.  It is also possible that RCA ran this 4 ohm set up on the 8 ohm tap.  Tube amps are quite forgiving and will tolerate a one step difference on speaker impedance.  This slight mismatch might have been for a bigger bass response from the unit.   

Anyhow, I would like to match up an correct speaker for the unit which is why I am looking for someone who might have a 6HF2 with the original speaker still in it.  I recently heard Pat L has a 6HF2 and I heard of another 6HF2 selling on eBay out East.  It would be great if he or someone else has the original and we can check the numbers and measure the impedance as well.


Magnavoxland

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Re: RCA 6HF2 original speaker question any owners? (Pat you out there?)
« Reply #5 on: April 02, 2015, 12:12:42 PM »
Todd, you posted this picture of one of your 6HF2s on ARF after you acquired it.  This is the set you found that didn't have a headshell with the changer... which isn't the one Nolan had.  I thought this woofer was original to the set.  It certainly isn't like the Alnico 12s I had in my SHF-4.  If RCA used the standard 12 inch woofers with that big amp, I can understand how folks might have blown them.  That is way too potent an amp for the normal 12 inch woofer.  RCA should have used a nice 15 inch woofer in that set.

Pat L

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Re: RCA 6HF2 original speaker question any owners? (Pat you out there?)
« Reply #6 on: April 02, 2015, 12:29:35 PM »
Here are pics of the speakers in my 6HF2. They are original and have never been removed. I did replace the original electrolytic crossover cap with the film cap. Pat

Magnavoxland

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Re: RCA 6HF2 original speaker question any owners? (Pat you out there?)
« Reply #7 on: April 02, 2015, 12:38:10 PM »
That is the same woofer as the SHF-4,5s have.  I'm surprised that RCA didn't use a more substantial woofer for this set.

Here's the big 15 inch woofer that was in my 6-HF-1, which has the same amp as a 6-HF-2.

« Last Edit: April 02, 2015, 01:08:47 PM by Magnavoxland »

Magnavoxland

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Re: RCA 6HF2 original speaker question any owners? (Pat you out there?)
« Reply #8 on: April 02, 2015, 01:10:15 PM »
Pat, how does your 6-HF-2 sound compared to the Magnavox mono consoles of the same vintage (1956-57)?

bastardbus

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Re: RCA 6HF2 original speaker question any owners? (Pat you out there?)
« Reply #9 on: April 02, 2015, 01:32:33 PM »
Larry, yes that is my 6HF2 and the woofer that came with it.  No, it is not the original.  When I first bought it and with a quick glance I thought it was original but closer inspection proved otherwise.  One can see where the wires have been cut and spliced back together with masking tape (which you can actually see in the picture you posted).  There is not even any manufacture markings or codes on the thing at all.   Regardless, take a closer look...that magnet is NOT any bigger then the one used on the RCA 100897 (961628) speaker.  Pictures can be deceiving, the basket has a weird stamping that is very wide at the top but the magnet is only that little square.  I compared it to the RCA unit and they are almost identical size.

Pat, thanks a bunch you are the man! That with the Sams and the fact that Nolan told me the original he pulled from mine looked "just like" the 100897 (961628) it pretty much seals the deal.  The only question I have (it is an easy one).  What is the impedance of your speaker set up?  Would you pull the speaker connector from the amp and check the impedance of the speakers with your DMM.  There is four pins on that speaker cable, two are empty and the other two are for the speakers.  Bottom left pin is positive and upper right negative.  Just hot those and see what you get, should give us the entire effective impedance of the woofer and tweeters total.  If you notice there is a small -1 suffix on the speaker number as well.  I have seen this number increase through the years.  So I wonder if the impedance changed with that number (I don't think so all mine are dead on 3.2 (4 ohms).

Also...you might want to check the polarity on your speaker system.  See that green dot....that is usually positive on RCAs of this era.  If it is...according to normal RCA designs, the crossover cap and tweeters are hooked up out of phase. I would check the phase of the speaker cord off the amp too.  I think half the big RCAs I have had come across my plate have had something out of phase in the speaker system just from servicing etc over the years.

bastardbus

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Re: RCA 6HF2 original speaker question any owners? (Pat you out there?)
« Reply #10 on: April 02, 2015, 01:39:50 PM »
BTW another clue Pat's speaker is original to the unit is the date code 274 is RCA manufacture code and the 602 is 1956 2nd week.   The 6HF2s were 1956 and that would put that speaker smack dab in the right time frame for this unit.

Sometimes RCA stamped the tweeters too...I often see the woofers and tweeters with matching (if not close) date codes on unmolested RCA units.

T

Magnavoxland

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Re: RCA 6HF2 original speaker question any owners? (Pat you out there?)
« Reply #11 on: April 02, 2015, 01:41:15 PM »
Todd, you are right.  Pat's woofer and tweeters are out of phase.

bastardbus

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Re: RCA 6HF2 original speaker question any owners? (Pat you out there?)
« Reply #12 on: April 02, 2015, 01:51:58 PM »
.... If RCA used the standard 12 inch woofers with that big amp, I can understand how folks might have blown them.  That is way too potent an amp for the normal 12 inch woofer.  RCA should have used a nice 15 inch woofer in that set.

True and why the ones I have all been replaced.  If you look closely at the progression of the Mark 2 through the 3 years it was available you can see RCA fixed the problem as they went along.

6HF2- 12 inch 100897 (961628) speaker
7HF2- 12 inch 100897 (961628) speaker with added 4 watt 12ohm resistor between the woofer terminals, possibly to cut down on the power output to the speaker?
SHF-2 15 inch Jensen woofer with HUGE magnet, mid speaker added too.

These units are only 25 watts and that is well within the range of any of these speakers.  Today you can find 12 inch speakers that handle 150Watts and up EASY....in fact it is difficult to find a low wattage 12 inch speaker.  I was contemplating trying a modern speaker to see how it sounds in something like this but don't have any on hand (and really don't want to spend on one) lol.

Pat L

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Re: RCA 6HF2 original speaker question any owners? (Pat you out there?)
« Reply #13 on: April 02, 2015, 02:04:28 PM »
Wow, How about that (being out of phase). That's the way it left the factory. A little history on the unit, I bought this console from an estate sale at a nice 1950's brick ranch in Chicago. This unit was down in the basement and hadn't been used in many years (decades). Upstairs in the main living room was a 1961 Magnavox French Provincial Imperial. The Magnavox had been in the same place for so long the shag carpeting was faded around it. I bought both consoles, I believe I paid $50 for the RCA and $60 for the Magnavox. The RCA had a custom piece of plate glass cut and edge polished for the top which kept it in remarkably nice condition.


As to how the RCA sounds, It's ok, nothing really great. The little tweeters don't really compare with the horns used in competing Magnavox's. The RCA is very pretty though, the dial and knobs are very attractive. The record changer is the original as well and is still shiny. The brass parts never tarnished. I never restored the record changer, as I had read that I would need to modify the unit for a new cartridge.


I just remember how excited I was to find an all original high end model like this when I wasn't even looking. As to the Magnavox, I restored it and it was a housewarming gift for my sister and her husband (also in excellent condition). Also, Larry won't remember but I bought a Photofact from him a few years ago when I found the unit  :)

624Magnificent

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Re: RCA 6HF2 original speaker question any owners? (Pat you out there?)
« Reply #14 on: April 02, 2015, 02:15:36 PM »
I see the polarity issue. Are both sides wired backwards? If so it shouldn't affect polarity/phasing, just an inconsistency in color coding.

Great discussion!!!
Tom