Rockola 1454 Speaker

Hi

The speaker that is not working is a Jensen Horn speaker 3 X 7 3/8 ( 220533) CCB758).

Anyone know how many ohms this speaker is?

Repair? If so who would you use?

Replace if so with what?

Thanks

Best
Darrell

Darrel. if i recall correctly, they are 8 ohm and not very efficient. AMI used the same speaker. Measure the V.C. You should see around 6 ohms DC resistance. I was told that if i washed them horn and diaphragm driver it would help the output a bit. It did help "a bit" bit I added a modern round horn to actually provide decent high end.

One of the horn tweeters here would be suitable:
http://www.pyleaudio.com/ProductsList.a ... ue=tweeter

Good efficiency at, or close to 100db/1 watt along with a crossover for both woofer's voice coil and tweeter would really improve that old machine. That, along with a magnetic pickup are what i used on the R-Os I rebuilt. Rock Ola and many other makers often skipped crossovers back then. Getting the upper-mids and highs out of a driver that can't properly deal with them really improves the listenability of the machine.

Rob/NYC

Rob

Thank you for info, any idea what the OHMS are on this speaker?

Which crossover would you use?

Best
Darrell

Darrell, as I mentioned, the speaker voice coil is probably 8-ohm. Easy to measure, just trace out the two wires from the flexible wires that connect to the voice coil on the cone. Your meter measures against DC resistance which is slightly lower than the AC impedance the amp sees. So, 6 0hms on the meter equals an 8 ohm speaker. 12 Ohms= a 16. Be sure to unplug it from the amp to avoid the effect of the output transformer.

The simplest type of crossover for the woofer is an approx 1.2 milli-Henry (Mh) coil and whatever capacitor is supplied for the tweeter you buy. In both cases the items are placed in-series with the voice coil.

Do a search for "speaker crossover". There are plenty of packaged crossovers available at low cost. Since you are using only two speakers you'll use a "two way" crossover.

Seeburg and pre-Rowe AMI used 12 decibel per octave crossovers which are slightly more complicated, but I have found that just the simple choke and capacitor combo which is a 6 db/octave is just as good for jukebox use when 12" woofers are used.

Rob

Rob

Thank you for the advice.

Best
Darrell

The old speaker is not marked for polarity and the new speaker is. The speaker is connected to a two prong plug that is also not marked for polarity. The wire color is very hard to tell, one is lighter than the other is the best I can tell (might be a white and a brown?). The only thing I can see that you might be able to useto figure out polarity might be the two prongs. One has a larger crcumference than the other one. I am hoping somone will be able to tell me which wire goes to positive or which one goes to negative?

Thank you

Best
Darrell

Hi Darrell,
Play a LOUD record at full volume--wet one hand--hold one wire in that wet hand--stick your tongue on the other --if it pulls you inward, your tongue is on the "plus" wire--if it pushes your tongue--that's the minus wire---------
And if I have con-ed you into believing that stuff-- I gotta bridge for sale, with your name on it--
If this is a "mono" phonograph with only one speaker--it don't mater, which way it's connected.If a stereo model--one way will have about twice as much bass as the other--that's the correct way---
Ron Rich

Ron

I believe every thing you say.

It is mono, but, it has a 15 inch speaker and the tweeter hotn speaker that I am replacing, so there are two speakers.

The problem is you can not see any cone push or pull on these speakers to determine if it is hooked up correctly. I guess I can just wire it up and see how it sounds and then reverse the wires to see how it sounds that way to determine how it should be hooked up. Would the louder bass indicate correct hook up in a mono two speaker system?

Also no one could positively say how many ohms the original speaker was, some say 16 and others say 8 ohms. The replacement is 8 ohms, what if any difference will this make if the original was actually 16 ohms?

The Rockola 1454 is from 1955/6, not sure what year Rockola came out with stereo.

Best
Darrell

hi Darrell
The polarity of speakers can be checked with a battery , when the speaker is connected to the battery, if polarity is correct the speaker will push outwards if not will push inwards, for a 1454 a 16 ohm horn (measures between 12 and 16) tweeter would be suitable, the lower you go in ohms will put more demands on the amp
clones

Please, --do not use a battery to test a tweeter--! You won't see anything and can easily damage the diaphragm in a horn driver.

Polarity-phasing won't really matter in this case because the two speakers' response do not overlap.

The point in phasing is to make sure that both speakers are creating sound waves that are coherent with each other. If they are out-of-phase one will be compressing air while the other is expanding the air. The net effect is to cancel each other over the frequencies they are both reproducing at the same time.

In cases like what you have in a mono speaker system the two speakers are dealing with entirely different frequencies and "never the twain shall meet". There might be a very slight cancellation due to the fact that the woofer is not choked (no crossover) but given how sluggish that big cone is at low frequencies it isn't likely to matter much.

Rob

Rob

I did not use a battery as I could not see how you would be able to tell anything, as there is no cone to observe.

So polarity will not matter in this case. The manufacturer says that a crossover is not needed with this speaker.

Thanks for explanation.

Best
Darrrell

Well I finally received an answer from Rockola about the ohms of the Jensen Horn Tweeter. It is not 8 ohms, Rockola said that it was a 16 ohm speaker. I have an 8 ohm replacement speaker, is there any concern or should I look for a 16 ohm horn tweeter? Just rebuikt the amp and do not want to damage that by over working it

Aoppreciate your thoughts on this?

Best
Darrell

Darrell,
Install a 5-8 ohm (higher--less volume), 5/10 watt resistor in series with the horn--it will be fine--
Ron Rich

Ron

Thank you. Project is coming along, will post some pics when I have it completed.

Best
Darrell

ds100h wrote:Well I finally received an answer from Rockola about the ohms of the Jensen Horn Tweeter. It is not 8 ohms, Rockola said that it was a 16 ohm speaker. I have an 8 ohm replacement speaker, is there any concern or should I look for a 16 ohm horn tweeter? Just rebuikt the amp and do not want to damage that by over working it
Aoppreciate your thoughts on this?
BestDarrell

Darrell, the amp local output is 8 ohm. Rock-ola used a 16 ohm tweeter to get a cheap 3db pad-down in it's response. They continued doing this straight through the 1960's (possibly beyond). The only reason to use a series resistor with an 8 ohm tweeter here is if the tweeter is too loud relative to the woofer and that is a matter of personal taste and acoustic environment.

I have a question here
:

The manufacturer says that a crossover is not needed with this speaker.

Is this a piezo tweeter? This is the only type that doesn't need a crossover. If so, the impedance of the tweeter is so high at low frequencies that the tweeter itself essentially has no loading on the amp. You would not need any sort of resistor in-series.

Rob