Newbie question- Ampeg B15N

[slavax]

Yes, I've been to the Vintage Blue site. Mark, your work is beautiful and I really appreciate your, JimmyM and other forum members' help.
Mark, I think I understand what you've said but I'm still curious: Are the outer edges of the grille baffle supported by anything like a rabbeted edge in the faceplate? Looking at the pics on Vintage Blue it doesn't look like it.
The original package of the Portaflex is incredibly cool looking. I was at Texas Tech Band Camp in 75' and one of the directors, Bill Snodgrass, performed with our band using a Portaflex and a Baby Bass; that was my first encounter. FWIW, I've owned a Dan Armstrong lucite guitar since 72' (ser.# 1495) my first decent electric.

 

[JimmyM]

FWIW, I've owned a Dan Armstrong lucite guitar since 72' (ser.# 1495) my first decent electric.

Do you walk with a hunch on one side? Great stuff, those Dannys, but dang they're heavy!

 

[slavax]

Yeah, I've been to the Vintage Blue site and the cabinets w/ dollys are beautiful, indeed.
Mark: I think I understand what you've said so far but I'm still wondering about the mounting of the grille baffle. Is there anything that supports the outer edges of the grille baffle? It doesn't seem like they should be floating- or do they? From the picture on the left it doesn't look like there's any reveal between the face frame and the 3/8" spacers. How wide are the face plate pieces and spacers- 1.5"?

 

[slavax]

OK, for some reason post #21 didn't show up for awhile and I repeated my questions. Yeah, the Lucite guitar is heavy, comparable to a Les Paul. I have told people that it's made of ice. I was 13 when I got it; it was just too cool looking to pass up. Also got to borrow a DA bass for a gig w/ my high school garage band and I let the guitarist use my DA guitar so we had... matching lucite guitar and bass for one gig! It was also very cool when I was playing punk/new wave later. It's been in mothballs most of the time since the early 80's.

 

[Vintage-Blue]

Mark: I think I understand what you've said so far but I'm still wondering about the mounting of the grille baffle. Is there anything that supports the outer edges of the grille baffle? It doesn't seem like they should be floating- or do they? From the picture on the left it doesn't look like there's any reveal between the face frame and the 3/8" spacers. How wide are the face plate pieces and spacers- 1.5"?

The face frame pieces on the double baffle cabinet are 1.75" (the single baffle pieces are wider @ 2.25"). Since the face frame is mounted to .75" thick sides & bottom, there is about 1" of the face frame sticking past the inside face of the cabinet. It is this exposed face that the 3/8" spacer strips get glued to. Ideally, that would make the spacer strips 1" wide, since they should finish up flush with the inside edge of the face frame. In practice though, I make them just slightly smaller, perhaps 15/16", just in case something is off somewhere. The final effect, when viewed from the front, is to give the impression that the face frame is 1.125" thick (.75 + .375). In one of the attached photos you can just barely see the seam between the face frame and the spacer strip.

The edges of the grille baffle do "float" - there is nothing supporting them. Since it's a 1/2" thick baffle, the lack of support doesn't cause a problem. Actually, there is some indirect support of the baffle. The baffle should be sized about .125" less than the inside opening of the face frame. This allows room for the Tolex that gets applied to the face frame, as well as the grille cloth that gets wrappped around the baffle. Depending on how close you make this clearance, the grille baffle can be a rather snug press fit within the face frame.

 

[vin*tone]

Hey Mark- What's the best way to stop my grill buzzing? I've tried a lot of things but there's always a little bit of bzzzzzzzzzzzzt.

 

[JimmyM]

Hey Mark- What's the best way to stop my grill buzzing? I've tried a lot of things but there's always a little bit of bzzzzzzzzzzzzt.

Dude, what happened to the fuzzy stuff you were using? I thought that worked.

 

[Vintage-Blue]

Hey Mark- What's the best way to stop my grill buzzing? I've tried a lot of things but there's always a little bit of bzzzzzzzzzzzzt.

You know, I've never had the pleasure of chasing down buzzes or rattles in an old Portaflex! The 2 old cabinets I have are in such poor shape that I don't know that they're even playable. That being said, I don't know if it will help to know what I do with the grille baffles on my cabinets or not. As far as I know, there's never been a problem with them buzzing, but maybe it's just that no one has told me. Before putting the grille cloth on I glue a piece of black felt to the front face of the baffle, using spray adhesive. Once the felt has been trimmed I put on the grille cloth, pulling it fairly tight. Once the cloth is on I put the baffle on a couple of cookie trays and put it in the oven, under the broiler. You have to watch it closely so you don't melt anything - it only takes a minute or two. I keep reaching in and tapping the cloth to see how tight it is. Once it seems pretty close, I pull the baffle out, rotate it 180 degrees, and put it back in. I do this because I never close the oven door while doing this, and I figure the back of the oven will be hotter than the front. As I said, so far that seems to work well for me. There have been times that I worried whether the loose edges of the cloth (beyond the staples) would ever vibrate or cause noise but so far I haven't noticed that.

Sorry I don't have any other ideas!

 

[Vintage-Blue]

This is a follow up to my response in post #25. Hopefully it will add a little more clarity to the face frame/spacer strip issue.

The images below represent a cross-section of the front of a double baffle cabinet, as if you were looking down through the cabinet from up above. The spacer strips are shown in red and are between the face frame and the speaker baffle. Only the side strips are shown here, but there is also a strip that runs across the top and one that runs across the bottom. The grille baffle is shown in blue. The first image shows the grille baffle before it's installed and the second image shows it in place.

 

[slavax]

Yes, that really clarifies things. Thanks!

 

[beans-on-toast]

Once the felt has been trimmed I put on the grille cloth, pulling it fairly tight. Once the cloth is on I put the baffle on a couple of cookie trays and put it in the oven, under the broiler. You have to watch it closely so you don't melt anything - it only takes a minute or two. I keep reaching in and tapping the cloth to see how tight it is. Once it seems pretty close, I pull the baffle out, rotate it 180 degrees, and put it back in. I do this because I never close the oven door while doing this, and I figure the back of the oven will be hotter than the front.

Mark, when I was shrinking the grille cloth on my front baffle, I had the same problem with it not fitting all the way into the oven. In the end, I heated the oven to 450 degrees F, opened the door all the way and held the baffle by the bolts in front of the open oven. The hot air blasting out seemed to heat the baffle fairly evenly. I pulled the baffle out every 30 seconds or so to check the tension.

I didn't have the guts to try it under the broiler. I was concerned that it would get too hot and melt the material.

David

 

[slavax]

Mark:

Are your cabs 21''x21''x14"? I was looking at the Unofficial Ampeg page and they were giving the early 60's dimensions as 21"x 21.75"x 14.5". Also, what is the inside dimensions of the ports? I've been looking everywhere and can't seem to find the info. Thanks

 

[Vintage-Blue]

Yes, my cabinets are 21" x 21" x 14". When I was building a new cabinet for Jess Oliver back in 2006 he gave me some of the dimensions, based on an old cabinet he had at the shop. I just looked back through my emails and found this, part of an email from him:

"Mark,

We were not making our own boxes, just did the case covering, so dimensions like that could have varied somewhat. They were not working from drawings, but from my hand-made samples."


With that in mind I checked an old double baffle cabinet that I got last year. It measures 21"W x 21.125"H x 14.125"D. So, it seems there is some potential for some variation in the cabinets. Continuing with that theme, the original ports were .75" x 6". However, around 1965 Ampeg started fooling around with changes to the ports. In some cases they stuffed some of the ports with blocks of foam rubber, as can be seen in the attached photo. You will also see cabinets from that time period that had smaller ports. I've never had the chance to measure them but they look very much like the ports used on the B18's, which would make them about .5" x 2.5".

BTW, for anyone drooling over the immaculate, museum-quality cabinet shown in the photo, it's not for sale!

 

[beans-on-toast]

I have this comment from Jess:


The eight ports in the inner baffle are 6" long and 3/4" wide. You may have seen a few with smaller ports.
My old boss, Everett Hull was fooling around. I won my case and the main production was as I stated.


I've always wondered if this meant that the B15 cabinets with the smaller ports were prototypes.

David

 

[Vintage-Blue]

David,

I think the larger ports were original. The only cabinets I've seen with the smaller ports or the foam blocks were from the '64-'65 era.

For what it's worth, here is another snippet from Jess:

"You may see slight variations because I think Hull was getting jealous. The B15N amp was so successful, I think he was trying to get his name on the patent, but the patent attorney turned him down. Hull did interfere with his little changes of my design, but I always won out."

He doesn't really specify a time period here, but he does refer to how successful the B15N had become, which leads me to believe the changes happened later. No matter what, if you ever spend much time trying to nail down standards with the old Ampegs it can be a bit frustrating. There seems to have been a fair number of oddball variations that were produced, with no real consistancy!

As a side note, I've attached a photo of an old grille baffle. Jess had put rubber tubing on the studs and said he used it to experiment with variations in the gap between the baffles.

 

[beans-on-toast]

Mark:

Are your cabs 21''x21''x14"? I was looking at the Unofficial Ampeg page and they were giving the early 60's dimensions as 21"x 21.75"x 14.5".

In addition to the cabinet variations, I think that part of the discrepancy in the measurements is how people use their rulers.

There's the edge round overs, the tolex, and the hardware to consider. This can lead to different dimensions. For instance, if you measure from front to back at the edge and include the chrome corner and foot, the dimension is about 14.5".

David

 

[beans-on-toast]

The B15N amp was so successful, I think he was trying to get his name on the patent, but the patent attorney turned him down. Hull did interfere with his little changes of my design, but I always won out.

There seems to have been a fair number of oddball variations that were produced, with no real consistancy!

The idea of Everett Hull modifying the design to try to get on a patent makes a lot of sense.

David

 

[Vintage-Blue]

In addition to the cabinet variations, I think that part of the discrepancy in the measurements is how people use their rulers.

David,

You’re definitely correct about how different people measure things! When Jess and I first started discussing me building a cabinet for him, Jess said he had a drawing he could send me to work off of. I thought that was great because, at the time, I had never done this before and I was totally clueless! It seems that Ampeg (St. Louis Music) was considering releasing a true reissue of the B15N (then Loud came along and that died out…). Jess sent them a double baffle cabinet to reference while doing their cabinet drawings. The drawing they came up with is what I used as a reference while building my first cabinet. It didn’t take long to realize that something was wrong. I sent Jess a copy of the photo shown below on the left, to proudly show off my progress (the photo on the right shows a “proper” cabinet). That’s when he questioned why the cutout in the grille baffle was so big. Then we realized there were other problems too. The face frame was too wide, the grille baffle was too thick (and mounted behind the face frame), etc. The bottom line is that the cabinet not only looked wrong, but the baffles, and therefore the speaker, sat back so far that you could not invert the head without it hitting the speaker. That’s when Jess took a closer look at the drawing Ampeg had done and realized it wasn’t even close! Parts of it were like a double baffle cabinet, parts were like a single baffle, and parts were like who-knows-what! I often wondered how someone could come up with those drawings when they had an original cabinet to reference?!

 

[beans-on-toast]

Talk about a lack of attention to detail! Although, I suppose that I shouldn't be surprised.

I went to a hardware store yesterday. The total was $19.75. I gave the cashier $20.75 so that they could give me $1 change. First they tried to give me $10 back. Then they needed to call their supervisor who needed a calculator to figure out what change to give me. I see this sort of thing often enough that it makes me wonder.

It's always interesting to see in progress B-15 cabinet photos.


David

 

[vin*tone]

Dude, what happened to the fuzzy stuff you were using? I thought that worked.

Hey Jimmy. The santa's beard worked a treat- and is pretty silent at most playing vols but sometimes comes up. It probably cut about 95% of the noise- the thing sounded like a goddamn gazoo when I got it.

Thanks for the suggestions mark I'll have a play around with that. I'm thinking my issue might be in the tension.