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Using Sunn Concert Lead stack for bass

alaskaleftybass

alaskaleftybass

Will Hanbury, Jr.
In Memoriam
Mar 21, 2012
9,920
22,352
Sitka, Alaska
#1
I fell into an unbelievable deal on this Sunn half-stack and had actually been looking for a small bass amp solution. Just for fun I hooked my bass up to it, and wow, it sounded excellent even with an open back.

But as I played it, it started cutting out, expecially when I turned the volume and tone controls around. if I shook the the channel volume control I could get it to put out a pretty nice sound, but now it's barely putting out any sound. I'm thinking, maybe I could do the following:

1. Send the head out for repair. Probably needs new pots. Does anyone know if this is expensive? I don't have a lot of extra funds to work with.

2. Remove the two back boards and replace it with one solid back. I'm thinking, I could place the two original back boards over the new back to get the holes to line up. I don't want to make new holes in the back of the cabinet.

3. Add a 3" flared port between the 4 x10" speakers for deeper bass.

4. Use "truck bed" rubberizing for the back for protection. Or should I use Tolex? I think I've seen Sunn style covering somewhere on the internet.

Other than the bad pots issue, and some spray paint on it, this amp has been sitting in a dry attic for 30 years. I would love to honor it by using it when I play.

Bear in mind, I do not play loud at all. I play at low to moderate gigs in hotel lounges where the bottom end is more important that loud volume. Just enough volume and bottom end to push the song along.

What does everyone think? Is it worth the effort to do a conversion? Of course I would save the original back to restore it to its original state if I ever passed it along or sold it.

Thanks in advance for your advice and reading my long rambling story lol....... :bassist:
 

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#3
I do that kind of thing often! I love modding amps but it doesn't always turn out how you'd like. I would try it as a closed back cab before porting it though.

A few examples... My B-12XTC I drove to Philly to pick up is now loaded with Beta 12A and 6550's to get some crazy volume and punch. I need to add a lot of bracing to the cabinet, especially the baffle, to make up for the additional air it moves now.

Last year I picked up a closed back Marshall 410 and loaded it with vintage CTS speakers pulled from an SVT810. I gigged it last night with the B-15 head at an open mic for a quieter SVT vibe.

On the other hand, my search for the right driver in my Kustom 118 was a pain. My first choice (JBL) didn't work out in that cab so I ended up with extra speakers and cabs. Armed with a new Faital and midrange driver, it came out great though. :D
 
#4
Sooooo what did you get it for?

IME, Sunn Concerts dont have much bass but are loud as hell, even the bass heads are more of a lead guitar amp. But if its enough bass for you, perfect. And the fact that your using an open back guitar cab with guitar speakers is another strike in the bass department.

What I would do is keep the Concert, I love these heads, and sell the 4x10. Some DOOM guitarist would love it, it looks like its in pretty good condition. Then buy yourself an actual bass cab, preferably with 15's but theres nothing wrong with 10s, this is just would I would do...and you dont need to listen to me.
 
#5
Thanks everyone for your thoughts.
I bought that and a vintage Kustom P.A. 100 watt head for $100. Sold the head already for $100 so the amp was free :)

I'll try leaving the back open once I try to repair the contacts on the amp, then send it out for repair if it needs it. I'll also try sealed back. As far as bass goes, I have an Ibanez SR500 lefty and it has great active electronics and a super bottom end.

Keep chiming in, I'm listening :bassist:
 
#6
B-string, sorry to sound so dumb, but how do I clean and restore the pots? I bought some contact cleaner from Radio Shack, but I don't even know where to start on the pots. I took the amp apart and it looked sealed from the backside too.

And MC Meunch, I'm very tempted to follow your device. I've been drawn to the new GK micro heads and ultralight cabs, and although I treasure the past, the new powerful ultra micro and ultralight stuff is very futuristic and exciting to me.... I'm thinking if I got the head repaired or at least the pots cleaned, I'll bet I could get enough for it on eBay to buy my new micro head and a cab... just thinking out loud here.....

Thanks.
 
#7
alaskaleftybass said:
As far as bass goes, I have an Ibanez SR500 lefty and it has great active electronics and a super bottom end.:
Click to expand...

Which won't make a bit of difference if your cab won't produce a decent bass response at appreciable gigging levels. I wouldn't put that up against anything but a mildly amplified acoustic set and expect it to hold up as a bass amp. Just IME/IMO...
 
#8
Point taken christw, i've noticed that Ampeg has 410 cabs about the same size, as does Peavey almost perfectly identical that are sealed. I'm thinking as long as I'm replacing the back, maybe pull the 4 10's and replace them with Eminence 10's. Would that address the bottom end issue?
 
#9
alaskaleftybass said:
Point taken christw, i've noticed that Ampeg has 410 cabs about the same size, as does Peavey almost perfectly identical that are sealed. I'm thinking as long as I'm replacing the back, maybe pull the 4 10's and replace them with Eminence 10's. Would that address the bottom end issue?
Click to expand...

It's certainly possible. I'd be mindful about the things you might run into converting a guitar cab to BG use like tracking down rattles, adding bracing, and possibly working out air leaks. Then there's also the cost issue. Four new Emi drivers may well cost you just as much as used cabinet already designed for BG use. I'd either keep that cabinet stock to resell with the head later or pick up a BG designed cabinet. It's really all about what you want though. I love projects and conversions myself but only undertake them if I'm going to keep something for a long, long time and have no plans of reselling it or getting my money back out of it... Sorry, now I'm lecturing you about cost on a free stack. :D
 
#10
christw said:
It's certainly possible. I'd be mindful about the things you might run into converting a guitar cab to BG use like tracking down rattles, adding bracing, and possibly working out air leaks. Then there's also the cost issue. Four new Emi drivers may well cost you just as much as used cabinet already designed for BG use. I'd either keep that cabinet stock to resell with the head later or pick up a BG designed cabinet. It's really all about what you want though. I love projects and conversions myself but only undertake them if I'm going to keep something for a long, long time and have no plans of reselling it or getting my money back out of it... Sorry, now I'm lecturing you about cost on a free stack. :D
Click to expand...

:D Laughing. All good points.
 
#14
When I was a wee lad in 70's, trying to be a prepubescent Chris Squire, I couldn't afford a Coliseum Lead head but managed to get a hold of a Concert Lead head which I used with an Acoustic 4x12 cab. It wasn't the bassiest rig ever, but man, that thing was LOUD!!! Thinking back, I seem to recall it was one of the best rock bass sounds I've ever had...
 

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