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Old 3rd Dec 2020, 1:42 am   #1
Trancypants
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Default Replacement drivers in Rigonda cabinets

Hello all, I hope someone could help me, please?

I recently acquired a pair of 1960’s Rigonda passive speakers.
Both cabinets have capacity for (at least) two 8” main drivers and two 5x3” tweeters.

One is working fine. It appears mainly original (2x 4gd-28, 1x 671gd-23 plus one replacement R&A tweeter.)

The second has a pair of the original 671gd-23 Latvian tweeters, and one chunky-as-hell 10GD-30E.
(Plus another 4gd-28 which is shot to pieces, it’s a basket only...)

Neither cabinet has crossovers.

My question is this: I love the look of these cabs (apologies for being girly), but would a pair of Goodmans 12” Eleganzia in each cab, alongside the two 4gd-28 & tweeters as above, be ok with a three way crossover?

(I’m thinking of using the 10GD elsewhere. I have a pair of Eleganzia drivers just gathering dust &#128533

Ideally I’d like to set up these two passive speakers to a vintage Rotel RA-313 (25w pc, A+B 8-16ohm required) along with a pair of Beovox 3702 (4ohm) speakers.

If someone could point me in the right direction I’d be really grateful. Thank you for reading this.
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Old 3rd Dec 2020, 9:58 am   #2
Edward Huggins
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Default Re: Replacement drivers in Rigonda cabinets

I guess whatever drivers you are going to use, the fix is not that critical. I think these enclosures are essentially open back type, so no form of tuning is possible. By all means use the Goodmans units, but will the existing apertures allow? I would not bother with a 3 way crossover as the side mounted ellipticals are not really tweeters. I would just wire these 7" x 4" speakers via a 2.2uf non-polarised filter (high pass) cap to limit the amount of bass reaching/overloading them. They will not be perfectly matched, but great for non-critical listening with a good old "one-note" bass!
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Old 3rd Dec 2020, 12:13 pm   #3
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Default Re: Replacement drivers in Rigonda cabinets

I think we established in another thread that the Goodmans ex-"Eleganza" drivers, if that's what they are, were originally used in a small, sealed enclosure.
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Old 3rd Dec 2020, 1:18 pm   #4
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Default Re: Replacement drivers in Rigonda cabinets

Those Goodmans drivers have a soft, floppy surround made of foam. It doesn't give much spring force trying to return the cone to its mid position. They rely on th cabinets being sealed and small to provide back pressure ftom the air inside to return the cones to their rest position.

If you use one of these in an open-backed cabinet, the lack of restoring force will let any deep bass from the amplifier bang the speakers into their end-stops.

For an open-backed speaker, you need to look for stiff speakers of the older kind with a sort of corrugated ring of the cone paper as its outer surround.

Stiff speakers don't move much - they can't move much, so Rigonda made up for this by using a pair of large speaker units to create a large cone area to shift the necessary amount of air without having to move far.

You mentioned a Rotel amplifier. Probably this follows the usual Japanese practice of having connections for two pairs of speakers and having a switch on the front panel to select one pair, the other pair, or both pairs.

If 'both' is selected, each channel of the amplifier has to drive two speakers in parallel. Most speakers are 8 ohms, so this presents a 4 ohm load to the amplifier. The amplifier will be designed to drive 4 ohms to handle this.

Bang and Olufsen are odd in several ways, but they hav always favoured 4 ohm speakers. Your Rotel should be able to drive yout B&Os but if you have other speakers connected to the other terminals, and you use the speaker select switch to drive both, you will be overloading your amplifier.

There may be some text about speaker impedance on the rear panel by the connectors, but it doesn't seem to work at stopping people blowing up nice little amplifiers.

Rotel was brought into the UK as a Japanese brand... I think distributed by the Rank organisation, and sold lots through Comet. They were seen as more attractively priced than Sony, Yamaha, Akai, Pioneer etc. It was only later that we learned that they were, in fact, rather decent.

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Old 3rd Dec 2020, 2:22 pm   #5
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Default Re: Replacement drivers in Rigonda cabinets

I use a Rotel RA-08 from about 2007. It sounds very dynamic especially on jazz and big band music. The amp was well reviewed at the time.
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Old 3rd Dec 2020, 3:42 pm   #6
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Default Re: Replacement drivers in Rigonda cabinets

If you look carefully you'll see that the woofers are connected in series.The tweeters are also in series,but with what appears to be a rectangular capacitor and then hooked on the woofers.
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Old 3rd Dec 2020, 3:46 pm   #7
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Default Re: Replacement drivers in Rigonda cabinets

The crossover is that small brown coloured capacitor, screwed to the baffle board. It's a basic way of doing it, often done with a 100 ohm resistor and a 0.1uf non polar capacitor in series feeding a piezo tweeter. Your tweeters appear to have coils, so adding an extra resistor would probably loose too much signal.
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Old 3rd Dec 2020, 6:15 pm   #8
Edward Huggins
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Default Re: Replacement drivers in Rigonda cabinets

As I said in my Post#2, these are not really Tweeters per se. For example, the R&A unit is a standard "full range" type with a 3 ohm voice coil. I suspect that those Russian units are similar. They just need some sort of high-pass filter to avoid them being overloaded with bass.
I would use the four original 10" (?) units and leave as it is. The Goodmans drivers could be be damaged in this type of enclosure unless you add a sealed back and then tune and properly dampen the enclosure. Also you have an aperture problem going from four 10" cut-outs to two 12" cut-outs. You will need a sub-baffle and placing a 12" cone over a 10" aperture cound also mean bad news for the drivers. In all I think you are trying to turn these Rigonda units into something they can never be....
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Old 3rd Dec 2020, 7:57 pm   #9
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Default Re: Replacement drivers in Rigonda cabinets

Thank you guys for all your advice, much appreciated
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