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Old 17th January 2009, 11:07 PM   #1
Pano is offline Pano  United States
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Default Old Grundig Fullrange fun

Well I bought a pair of these beauties:
Click the image to open in full size.
image courtesy of
German Vintage Loudspeakers
click for more pix


I didn't really care how they sound, I just love the look! And my wife thinks they're "cute." Mine are not as pretty as those web photos, they need some serious clean up and restorting.

These are late 50s full range. Just one 7x10" oval driver in each. Bass reflex via a big square port under the driver. No stuffing, no bracing, no filters, nothing. Just a flimsy empty box with a driver. Mine do have an on/off switch on the side. 5 ohm driver.

They styling is very cool and fits our taste in mid-century modern furniture. They stand about 32" tall and weigh next to nothing.

How do they sound? Awful. Real vintage mush. No highs, no lows (just like Bose!). Not Hi-Fi at all. The curved backs are super thin, maybe 3mm. No bass at all, forward mids, no imaging. I thought they might be muddy and boomy, but they aren't.

They are running now with a BSC circuit - 2mH in series with 5 ohms. Helps, but that's all. Might need to go to 3mH. Maybe some bracing and covering the walls with fiberglass could help, I don't know. The whole curved edge front baffle comes off as a piece, but does not seal well at all, so the BR can't really be working.

But as mentioned above, I bought them for their good looks, not the sound. Once I clean them up I may try to squeeze some better sound out of them. Or maybe not. =)

Anyone here ever take on a project like this?

BTW, I have T/S measurements of the drivers, if anyone cares....
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Old 17th January 2009, 11:20 PM   #2
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Go for it -what do they spec. like?
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Old 17th January 2009, 11:44 PM   #3
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Maybe keep the enclosure, but replace the speakers with something more musical? You could seal up the port and make it a sealed enclosure, if that suits the new speakers T/S better. Also, you could fill up the inside to make the sealed volume smaller if needed...


Cheers,
Mitch
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Old 18th January 2009, 12:13 AM   #4
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If they are the same drivers as I think they are, then the drivers themselves are fantastic. All they need is a decent enclosure and a pair of helper tweeter and they should sound lovely.

Shoog
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Old 18th January 2009, 12:17 AM   #5
BudP is offline BudP  United States
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EnABL them and treat the box inside to EnABL, made from balsa wood strips, end of problems, except for real bass.

Bud
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Old 18th January 2009, 04:32 AM   #6
Pano is offline Pano  United States
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Hi guys,
Not really sure yet what to do with them. But probably will try to make them the best they can be with the oval driver, even if that means adding a tweeter (they do beam a bit).

Bud, good idea on the balsa EnABL. =)

Shoog, I'll take a photo of the driver.

FWIW, here are the T/S parameters.

f(s)= 68.64 Hz
R(e)= 3.70 Ohms
Z(max)= 32.19 Ohms
Q(ms)= 7.004
Q(es)= 0.910
Q(ts)= 0.805
V(as)= 20.3liters (0.72 cubic feet)
L(e)= 0.59 mH
SPL= 90.47 1W/1m

The Vas is seriously in doubt as the added mass method was used and the mass was placed on the back of the driver - because I didn't take it off the baffle. Once they are removed, I'll measure again.

My best guess is that the cabinet is ~26L.

Funny thing, these also came in a powered version - with a mono tube amp in each cabinet! I believe overall size was larger for the powered version.
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Old 18th January 2009, 04:58 AM   #7
mp9 is offline mp9  United States
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Default hifi lautsprecher-box 14

spitzenbelastbarkeit 6 watt impedanz 5 Ω vor feuchtigkeit schutzenl 1400-022 yes i have a pair of the cabinets only w/out driver's but in good condition. i think they'll look cool next to the mint scott 222c (org. everything inc. telefunken 7189 power tubes). thinking of beefing up the interior walls and poss. installing a 89db tangband 6x9 w69-1213sb midbass & a tweeter. anyone know what 6x9 drivers were used in the brentworths? haven't decided what to do w/them yet, its low on my to do list.
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Old 18th January 2009, 05:21 PM   #8
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Qts of .8 in a ported enclosure? Can't really see that giving satisfying results - especially not in 26L!
To be honest, if your params are correct 26L is too small for this driver even sealed so I would probably try stuffing the vent and going for some aperiodic alignment

Edit: Yes, add a tweeter! I'm sure even a few $ tweeter with just a cap would be a huge improvement. If those 7x10s even produce treble the dispersion must be terrible
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Old 18th January 2009, 05:39 PM   #9
Pano is offline Pano  United States
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I think the 0.8 Qts measurement is about right. My WT3 tester seems to do that well. (but I should double check)

Yeah, I agree about the aperiodic. I can't find any vented alignment that seems to work well with this driver. And aperiodic would be easy to build into the exisiting flat port.

I have several paper cone tweeters, even some Grundig. That will be the next thing I try.

The big problem is going to be gettting a good seal between the front baffle and the rest of the box. It may take some serious work.


MP9, do you have any ideas?
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Old 18th January 2009, 06:02 PM   #10
chops is offline chops  United States
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If you have any of those Grundig electrostatic tweeters laying around, you could use a pair of them as super tweeters added to the paper cone tweeters you mentioned.

My father has a large table top Grundig out in his shop right now that he just finished restoring the other day. He always runs them in for several days to make sure everything is just right. Anyway, it has dual 8" woofers, dual 3" cone mids and dual 2" electrostatic tweeters. Even though its mono, it doesn't sound half bad.
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