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ampeg b-15 question

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pauldebass

May 8, 2006
91
6
#1
I pickup a mid 60s B-15 portaflex ampeg amp. it was 'restored'. looks in great shape. when I lifted up the head, the inside of the cab was lined with foam and the space of the cab was filled with insulation (that fiberglass type stuff) the owner said that's how they were. Is this true?
second question the speaker which is the original speaker seems pretty light weight. any suggestions here? were other speakers put in to improve sound like EVs or JBLs?
 
#2
My 66 B-15N has a thin layer of fiberglass insulation on the back and bare wood elsewhere. As for the speaker, I haven't heard of a lot of people replacing it unless there was something wrong with it. The B-15 sounds so good that you don't want to monkey with it unless you have to. And since mid 60's models were only like 25 watts, the speaker didn't need to be so massive to handle the SPL's.
 
#3
My B-15-N was made in 1964 and it has a thin layer of fiberglass on the inside back panel of the cabinet. The speaker in my amp is a CTS 15 inch (has square magnet) and it sounds very good.

I repaired a very old one of these a few years ago for a guy and his was missing the speaker. We just used an Eminence 15 that was a pretty low powered and inexpensive version that ended up sounding really good in that amp.
 
#4
pauldebass said:
I pickup a mid 60s B-15 portaflex ampeg amp. it was 'restored'. looks in great shape. when I lifted up the head, the inside of the cab was lined with foam and the space of the cab was filled with insulation (that fiberglass type stuff) the owner said that's how they were. Is this true?
second question the speaker which is the original speaker seems pretty light weight. any suggestions here? were other speakers put in to improve sound like EVs or JBLs?
Click to expand...

+1 on the sound absorber/insulation comments. B15N's came stock with CTS 15's with Altec 421's availble as an OEM upgrade. Jess Oliver's current business of restoring/modifying old B15's reccommends JBL D130's or the like. Personally I like ALL of those speaker options. A lot of speaker snobs diss the old CTS, but 90% of B15N's have them, and that hasn't hurt their rep one bit. Mine sounds great and has loads of bottom.
 
#7
pauldebass said:
the sound is good not 'great' and I have heard other b-15s I might try to change the speaker to a jbl to see if there's much difference.
thanks for the responses
Click to expand...

I have a b-15 too and am in the same boat. Mine sounds good but not great. I also have the CTS speaker and was thinking about putting in a jbl d140. I also thought about replacing the 6SL7's. Mine just doesn't sound as good as I think it should for what I paid for it! Maybe I am just used to the tone of my Berg cab or something!
 
#8
Pauldebass-
About 10 years ago, I inherited a mid-60's Ampeg B15 N cab (no head) with a blown Jensen speaker. There was yellow fiberglass insulation on the back panel and wood everywhere else. I put a Carvin 15" in it and use it with my Ampeg B2. It sounds great. Liked it so much that I recently bought two complete FlipTops!! Jess Oliver really hit the mark when he designed the B15.
Good Luck To You!
 
#9
I just now finished playing on mine...and found some great tone! I put the treble full, bass 3/4, volume full, and low boost on while plugged into the second brite channel. The bass knob actually acts as the volume. Sounds very very good...very full with the CTS speaker that I was fixing to write off! I have a '68 with the larger tuned cab BTW, which I am sure is a little different than the mid-sixties version. Also, mine has the insulation on the back and none on the sides as well.
 
#10
I put a JBL 2205 in mine sounded great up to a point then didn't sound so hot. I traced the problem to the JBL cone hitting the reinforcing bar across the speaker cut out, Making a ring out of 1/2" ply to go between the JBL and cabinet fixed the problem. I still can't get huge volumes out of it but what I do get is nice. When I look back to the gigs I played with a 50W Leak power amp, a simple one valve pre-amp and Marshall 100W 4x12 I shake my head. In those days I never had a worry about filling any hall I played in. How times change!
 
#12
I have an early ‘70s with the thiel cabinet equipped with an Altec 421.
The 421 is clearer than a CTS, more head room and reproduces the top and upper mids better, But lacks that raw texture and earlier break up the CTS does so well.
I do love those old CTS speakers.
I prefer the sound of the Altec to the JBL, they sound a bit warmer and smoother at the same settings.
My (matching) extension cabinet had a blown eminence when I got it. I put in a Square magnet Utah a friend swapped out of a cabinet he had. It’s dark and dirty sounding with very early break up. They do work fairly well together giving a nice blend of clean and breakup. If I come across another 421 I’d probably swap it out and give my friend his speaker back.

I have seen one ‘70s cabinet with a Jensen C15LL square magnet in it. The sound was very close to that of a CTS.

I think an EV 15 M might sound pretty good. They are super efficient and don’t color the sound so you’d get the true sound of the amp and bass.

Every cabinet I’ve seen has fiberglass on the back, and none on the sides.

Btw: it seems every studio around here has one. Each probably sounds a little different given cabinet size, age and tube compliments but you’d have a hard time saying which one actually sounds the best.

MM
 

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