Cornwall I restoration

[ronajon]

i just got a pair of Cornwall speakers that have been sitting in a barn shed for some years. so after first dusting and some inspections (and a little shock about the size they are sitting in my living room) i've connected them to my amp, replacing a pair of quartets.

 

info from the tags

sn: 21T096 / 21T097 i found they are from 1979

one has initials OD, the other ASL

 

They have been playing for a couple of days now, and i'm thinking about restoring them. The state is sort of oke, there are some chips in the woodworks and the cloth has some rips.

before i begin, i have some questions about restoring them

 

1. i'm not sure if i want to repaint the speakers or put veneer on them. Is the colour bound to the serial number? ( for now i would like to keep them as stock as possible, only repair what is needed )

2. as seen in one of the photos, it looks like the sides have a veneer (there is a layer peeling off), but from the top it looks like they are painted?

3. in case of a repaint, what paint is advised ?

4. does the front panel have another paint or brush or is it the same as the side panels ?

5. what can be used for filling the chips on the corners and edges ?

6. should the caps be replaced? i've read about the JEM Performance Audio caps. is there a European dealer of JEM ?

7. one of the plastic tweeter housings has a hole, it look like the connector was replace to the left bottom. does the hole affect the sound ?

8. are there other points i should think about when restoring them ?

 

thanks for any help

 

Edited December 1, 2023 by ronajon
added caps, changed topic title

[billybob]

Welcome back! Members will be with you soon I hope.

Thanks!

@ronajon

[Ceptorman]

Congrats on detailed photos. The insides look wonderful. Satin black paint and lambswool grill cloth would look spectacular. 

How do they sound?

[OO1]

2 hours ago, ronajon said:

 

is there a European dealer of JEM ?

7. one of the plastic tweeter housings has a hole, it look like the connector was replace to the left bottom. does the hole affect the sound ?

 

JEM only operates in the USA , but they can ship overseas ,  as far as the tweeters , these are non-original  5$  piezo tweeters ,  try to locate a pair of K-77 tweeters 

[ronajon]

44 minutes ago, OO1 said:

JEM only operates in the USA , but they can ship overseas ,  as far as the tweeters , these are non-original  5$  piezo tweeters ,  try to locate a pair of K-77 tweeters 

 

i was just looking at the tweeters, and comparing with k77. noticed the difference

i've seen k77 with square and round drivers. what are the differences and which are appropriate for my Cornwall I  ? (and which are better ? )

[OO1]

38 minutes ago, ronajon said:

 

i was just looking at the tweeters, and comparing with k77. noticed the difference

i've seen k77 with square and round drivers. what are the differences and which are appropriate for my Cornwall I  ? (and which are better ? )

round are Alnico magnets ,  square are ferrite magnets , same diaphragms , the square are more recent  , the tweeter is the Electrovoice T-35 8 Ohms  

[KT88]

@ronajon I would install as a tweeter what was installed in time. I do not know when the K77M came out. My 1977 LaScala have the round magnets of the K77 alnico. I also bought 1981 K77M sort of as a backup if something bad happens to the alnicos.
Advantage of the K77M: they retain their magnetic force forever.
Advantage of the old K77 alnico (my personal view). They sound very silky and fine in and out fade of strings, for me more emotional...if you like classical music.
Disadvantage of the old alnico K77, they can lose magnetic force over the decades, even with great probability. I had my K77 remagnetized in a special workshop in Mannhein, Germany. Before 12 Khz, after 16 khz and 1.5 dB louder. If you listen primarily pop, rock goes the K77M just as well in my opinion, for classical and jazz I would prefer the alnico. It seems that 1979 is pretty much on the edge of change.

One more thought on the diaphragms of the K77/K77M. There are replacement diaphragms offered, but all that are currently available are cheap and bad. If you buy K77(M) and they run, don't change the diaphragms. I had bought new ones (bad ones i didn't know) and the shop that remagnetized my alnicos was supposed to install them at my request. they got back to me and said that the old original diaphragms are much better...still. Of course you have to make sure that your purchase is really still original K77(M) May I ask where you live?

[ronajon]

@KT88 thank you for your reply.

i mainly listen to Rock (metal) but my wife prefers classical, so there we have a difference when i comes to K77 or K77M. For now i think i would go for what is available.

Living in the Netherlands, it seems difficult to source components.

 

I'm tracking several sites (dutch and german marketplaces, ebay) for the tweeters, up until now the only ones i see are located in the USA. Unfortunately the shipping costs from there are quit high

 

i do not have much rush, but on the other hand i'm very curious how the speakers would sound with the correct tweeters in it

[KT88]

5 minutes ago, ronajon said:

@KT88 thank you for your reply.

i mainly listen to Rock (metal) but my wife prefers classical, so there we have a difference when i comes to K77 or K77M. For now i think i would go for what is available.

Living in the Netherlands, it seems difficult to source components.

 

I'm tracking several sites (dutch and german marketplaces, ebay) for the tweeters, up until now the only ones i see are located in the USA. Unfortunately the shipping costs from there are quit high

 

i do not have much rush, but on the other hand i'm very curious how the speakers would sound with the correct tweeters in it

Do you know hifishark? It is a meta search engine for hifi gear. You can register and you get every day updates about that item you like to search from most hifi sites plus ebay etc from everywhere, even from marktplaats

 

hifishark.com

[ronajon]

10 minutes ago, KT88 said:

Do you know hifishark? It is a meta search engine for hifi gear. You can register and you get every day updates about that item you like to search from most hifi sites plus ebay etc from everywhere, even from marktplaats

 

hifishark.com

 

i did not know that site.

just looked at the list that site is scraping !

[CWOReilly]

5 hours ago, ronajon said:

 

i was just looking at the tweeters, and comparing with k77. noticed the difference

i've seen k77 with square and round drivers. what are the differences and which are appropriate for my Cornwall I  ? (and which are better ? )

I have ‘79 CWs as well you need the round magnet k77. 

[Audible Nectar]

CWOReilly has it right. It appears the OGs were swapped out for some piezoelectrics and need to be swapped back to be as original.

[ronajon]

you're right @Audible Nectar

i'm already looking for a set of K77's or K77M's

[ronajon]

small update,

i bought a pair of Crites CT125 tweeters to replace those cheapo plastic tweeters. the sound now sounds less fatiguing, highs are smoother and warmer. 

 

Next job is to fill all gaps in the woodwork, repair the sides and the do a veneering job.

Was thinking about birch veneer, and put some danish oil on it afterwards. The look is going to be the same as my upgraded Lenco L75 turntable with custom birch plinth

 

 

[ronajon]

Just now, ronajon said:

 

the step up from the plastic piezo tweeters to the CT125 from @KT88 was already a huge one.

The sound with these CT125 is warmer and smoother.

 

 

i'm sure willing to mod the CT-125, but not sure how to "move the tweeter filter from tap 4 to tap 5 " ?

as this is not my topic and i don't want to hijack it with my questions, i'll move this to my own thread about the Cornwalls i recently purchased. Feel free to continue there on modifying the CT125's i've got .

 

 

[mboxler]

1 hour ago, ronajon said:

 

the step up from the plastic piezo tweeters to the CT125 from @KT88 was already a huge one.

The sound with these CT125 is warmer and smoother.

 

 

i'm sure willing to mod the CT-125, but not sure how to "move the tweeter filter from tap 4 to tap 5 " ?

as this is not my topic and i don't want to hijack it with my questions, i'll move this to my own thread about the Cornwalls i recently purchased. Feel free to continue there on modifying the CT125's i've got .

 

 

On the Type B crossover,  the tweeter filter is connected to tap 4 (-3.35db, dotted line).  Simply desolder that wire (which is connected to the 2uf tweeter capacitor), and solder it to tap 5 (-0db, bold line).

 

[ronajon]

thank you. it took me some time to figure out the layout of the scheme from @mboxler since i'm a total noob on electronics, but finally got there.

only did one for A/B testing purposes, my first impression was that the overall sound level seemed a little lower? 

 

i'm not sure if that's correct, because from the thread i read that the voltage for the CT125 should raise by 3.35 db (is that decibel ?) and the squawker should drop with 1db

 

So to my understanding the overall sound should be louder, or am i totally wrong here ?

[KT88]

How is the balance now between squaker and tweeter? May be that it could sound a bit less loud because most of our loudness impression may come from the squaker, but that drop you could compensate with your volume control. Relevant is if the tweeter in now louder in relation.

[ronajon]

in the modified crossover sound warmer now.

 

in the non-modded crossover, i can distinguish the tweeter more from

not sure if that is the result that was to be expected ?

[mboxler]

57 minutes ago, ronajon said:

thank you. it took me some time to figure out the layout of the scheme from @mboxler since i'm a total noob on electronics, but finally got there.

only did one for A/B testing purposes, my first impression was that the overall sound level seemed a little lower? 

 

i'm not sure if that's correct, because from the thread i read that the voltage for the CT125 should raise by 3.35 db (is that decibel ?) and the squawker should drop with 1db

 

So to my understanding the overall sound should be louder, or am i totally wrong here ?

 

We are all noobs one way or another.

 

Yes, db is decibel.

 

Perhaps the squawker dropped by more than I thought.  The only other thing would be to move the squawker from tap 3 to tap 4 as well.

 

Sorry.  If I had Cornwall's I would try this myself before suggesting the changes.  I know it's a pain to remove the back.