Replacing vintage stereo speakers

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Hi there,

I've been fixing up an old stereo hi-fi console from the 50s and want to replace the speakers. It's a simple 2-way system but I want to put in better speakers than the ones that are in there. I know nothing of speaker design so any input would help.

First, I'm limited to the size. The woofer has to be 12" and the tweeter can be either 3.5" or I suppose I can go up to 4". From what I can tell, they're connected by some kind of simple condenser/crossover. I do not know the freq range of the speakers but I do know that the speakers are 9ohm (woofer) and 4ohm (tweeter).

So what I'm looking for is some idea of what I need without a lot of involved math. I've looked for kits online but have turned up nothing with this size combination. I'm not interested in price range right now but really what I should be looking for. What should be the ceiling on my woofer (40hz - 2000? 3500? 4000?) and what should be the bottom of my tweeter (2000?) What sort of crossover do I need between? (generically speaking) Do the freq controls on the console have any bearing on this on my selection? (I'm guessing no)

Again, any help would be appreciated.

Kind regards,
Giacomo
 
diyAudio Editor
Joined 2001
Paid Member
Are they in a box like structure? ie, are they in a box, even if the box is part of the structure of the consule?
If so, what is the internal size of the box?

Is there a vent or port in the box area? ie a hole in the front or back without a driver?


Do you know what brand the existing drivers are?
 
I don't want to put a dampener on this but if the original units
are still working there are those that would be appalled if you
changed them (people who like vintage drivers).

If you want to change them planet10 seems to be the expert
in this area. A Tangband 3" or 4" unit sealed off and a 12"
unit 6dB more sensitive than the TB crossed over first order
near the baffle step frequency seems to be the way to do it.

IMO this will be much better than the vintage units.

:) sreten.
 
Thanks for the reply.

From more research that I did this morning, I presume the setup I have now is serial. There is no brand marking on the speakers. The console is a Voice of Music from 1959 and as they went out of business some thirty years ago, it's a bit difficult to find out if the speakers were made by VM or if they were build by a third party for them. I have a repairman's schematics for the whole unit, but there is very little info on the speakers themselves.

I have plenty of room to work with on the inside of the cabinets. Unlike most of the 50s consoles, these speakers are separate from the amp/turntable. On the inside is actually another piece of wood that can be removed from the cabinet. It is this piece that holds the speakers. It is possible for me to cut another piece of wood with different size holes for any configuration, but as I'm an apartment dweller, I'm unsure if I want to undertake this right now.

I've been informed by another VM enthusiast that I should be presenting 8ohms to my amp. So if I want to keep this in a series, that means I have to get two 4 ohm speakers, correct? Or if I want to go parallel, then I will need to get two 16ohm. Am I on the right track here?

I'm still unsure about the capacitor between the two speakers. Based on what speakers I buy, how do I know figure what capacitor to use? I'm presuming that it's this capacitor that filters my low frequencies to my tweeter, correct?

If you can think of any good setup for a tube amplifier, and considering that I have room to work (plenty of room for a crossover if that's the way to go) please post.
 
follow up

Just read the post from sreten. Yes, usually I wouldn't try to change the speakers. I have a 67 fender vibrolux amp that would be pure desecration if I changed over, but I don't think the speakers for the console were the absolute best from the era. They are pemanent magnet and I know that on the whol (but correct me if I'm wrong) that pm's usually don't have good response. The console is so well made (real walnut, great tube amp) that I think that's where they cut corners.

Thanks and kind regards,

Giacomo
 
diyAudio Editor
Joined 2001
Paid Member
Since the 2 drivers for each channel are crossed over to do different parts of the spectrum, usually you would use 2 8 ohm drivers per channel. Now if they are run in parallel without a crossover, then you would need 2 16 ohm I guess, but I suspect that is not the case. The tone controls have nothing to do with things as you suspected. You are still unclear about the speaker box. Is it open on the back?

You would help yourself a whole lot if you take photos of the speaker box from front and back , and close ups of front and back of the drivers.


Anyway we need Planet 10 here- where is he when we need him? but he needs photos too.
 
Variac,

Thanks for your continued interest. I've posted a pic of the drivers that are in there now. Check the next post for the enclosure.

I hooked up a pair of Event 20/20 studio monitors to the power amp but they're rated 4 ohm. I know this is not supposed to be good for the amp. The sound is definitely not as clear as with the original speakers. A bit muffled. Could this be from the impedence difference?

I've been looking into those eminence speakers. I'll presume from your suggestion that they are are good value. What do you think about the tweeters? Here's where I'm confused - should the tweeter range pick up where the woofer leaves off (5k for the betas) or is it all right to go lower (say, a bottom of 3.5 or 4k) Then there's the capacitor or crossover to consider too.

You've been a great help so far!

Thanks and kind regards,

Giacomo
 

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I don't think a PA type speaker using the Eminence Beta is a
good idea, its only around 90dB/W in the bass and has a
strongly rising axial output in the midrange.

http://www.partsexpress.com/pdf/290-408.pdf

This bass unit looks decent if your cabinets are big :

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=295-320

This should have a sensistivity of around 89dB in box,
mate this to a mid/treble driver, e.g. :

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=264-814

Use a first order series crossover set at around 250Hz.
(~ 90uF and 4.5mH calculated with 7R)

Or alternatively use a parallel network say 5mH with the
bass unit and simply use a capacitor to protect the TB
from low bass, you need to experiment here, but I'd
guess about 250uF.

Stuff the box, there is no need to seal off the smaller driver.

Your other option for a 12" bass unit is a full 3-way design.

A 12" two way with a normal tweeter is not a good idea.

I think there are better TB units not sold by PE,
as I said I'm no real expert at this.

:) sreten.

(illustration is for 1Khz c/o)
 

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Sreten,

Than you for your continued interest too!

Here's a pic of the front. Yes, the cloth is on all three sides. The speaker board fits into it from the back. That's why I have a lot of room to work with. This is from an era when hi-fi was furniture!

The amp is rated 140 watts. So I suppose I can go with 150watt speakers and above if that makes any difference to your recommendations.

Cheers and kind regards,

Giacomo
 

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The 140W rating is probably power drawn from the supply.

The cabinets really do have me confused, what the angled
section in the base for ? Is this where the baffle goes ?
Is there another screw on back as well ?

They will require some major work to convert to sealed boxes,
are you interested in doing this ? or using them as is ?

:) sreten.
 
Using the cabinets as they are this woofer is a better choice and cheaper :

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=290-335

The drivers high Qts will counteract some of the baffle roll-off,
(see attached plot for driver in a very big baffle)

Use the TB unit, flush mount to the front of the board if you can.

Use a first order series crossover set at around 200Hz.
(~ 110uF and 5.5mH calculated with 7R)

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=027-360
Bypass this with this in parallel:
http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=027-428

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=266-570

They will sound very different to the current driver set
up, hopefully somewhat better, though accept this is
all educated guesswork on my part.

Its possible the amplifier has buillt in pre EQ for the speakers,
in this case its impossible to say how you should approach
this without some measurements.
(You can check for this by using a radio with some decent
heaphones and then connecting the heaphones to the
speaker outputs with the console radio, if there is a lot of
extra bass its likely the console does have pre-EQ.)

Good luck !

:) sreten.
 

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I've had a rethink on the crossover frequency.

Use a 4mH inductor same type as before.

Use 68uF +6.8uF (non-polar electrolytics) + 6.8uF bypass,
all in parallel, same types as before.

For 280 Hz, should be a safer bet than 200Hz.

:) sreten.


http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=027-336

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=027-424

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=027-356

http://www.partsexpress.com/pe/pshowdetl.cfm?&DID=7&Partnumber=266-562
 
sreten. variac

you guys are monsters! Really, thanks for all the feedback on this project. Here's a pic of the whole system, so you can get an idea of where I'm coming from.

To answer your question about the angle in the base, this is where the speakers go. Why they were angled within the cabs, one can only guess. I think the idea was to make a sweet spot with the cabs flush against the corners of the walls. That way the cabs would be facing forward, but the speakers would be angled. Aesthetics, eh? I didn't discover this till I opened them up and found I had left and right transposed.

To make this even more interesting, you have to understand that the phono section has a selector for bandwidth based on the engineering of the album. Back in the 50s there were several competing methods for mastering. A record could either be LP, RIAA, or FFRR. By switching this selector, you would get the best sound for our record. For instance, when set to LP, the amp would be set to a bandwidth filter for a certain range that would limit the 'rumble' of a record that was mastered in LP.

Anyway, this is my stereo and on which I listen to all my records and cds, so I want to make this sound as best as I can. I'm budgeting about $250 for the project, so if you think anything in he Eminence line would sound better, please let me know. Forgive my ignorance, but I really don't understand the math behind all this, so i think I will be asking more questions about the capacitor to buy. Especially all that stuff about first order, second order. But I think I've got the basics now.


Again, thanks for all the help. You've both been so very kind.


JR
 

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Well the stuff I've suggested would come to a lot less than $250.

Having the tweeter underneath the top wooden section isn't
great but then again the whole design of the speakers isn't
exactly rocket science.

They look like boxes but they are open baffles.

My suggestions are based on not being expensive, and staying
relatively true to the sort of sound produced at the time, though
using the smaller unit for midrange should be a huge improvement.

The only problem could be that the drivers I've suggested will
not be particular loud, but I've no idea how efficient the current
drivers are and if volume capability is an issue.

IMO what I've suggested will be fine if efficiency / volume is not
an issue. You could spend more on the drivers for more efficency
and if you did then I'd suggest some sensible changes to the
cabinets also, nothing too drastic, and no external changes.

It really depends how far you want to go.

But other than my concerns about efficiency, the drivers I've
suggested will be extremely cost effective and you shouldn't
regard them as the "cheap" option, just well chosen.

The other concern as mentioned before is the tonal
balance of the speakers, and any amplifier correction.
If the drivers suggested don't work well, more expensive drivers
chosen along the same lines won't either, they'll just be louder.

If the drivers do sound OK, then as mentioned before there are
some internal modifications you could try to improve matters
further, if you want to go down that route.

:) sreten.
 
Just curious but have you tried using the original speakers? If they work, why do you want to replace them? The tube amps in those old Voice of Music units are great by the way. I have several VM integrated amps and recently bought the guts from a VM console. The console amp I have uses 6BQ5 (EL84) output tubes and sounds awesome. They also made a version with 6V6 outputs that seems to be essentially the same amp design. I got the raw speakers too but one of the woofers has a couple of small tears in the cone. . . . Charlie
 
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