Mismatched speaker ohms?

Electromancer

Electromancer

Oct 13, 2024
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#1
Hi everyone. I’ve been reading posts here for a few years now and it’s finally time that I need to get in here and ask some questions. I’ll start by saying that I’ve been building pedals for a several years but I’m new to messing with amps and cabs.

I’ve recently acquired an old 2x15 Kustom (?) cab that I’m told is from the 60s. It has no badge (it doesn’t look like there was ever one there) and the plate where the input jack went is gone, so I have nothing to go on to get any info.

The speakers are old square backs and appear to be original but one reads 16.9 ohms and the other reads 6.6 ohms which ,from everything I’ve read, ain’t right. What’s up with that? The 6.6 seems to need replacing (sounds fuzzy and when I push on the cone I can hear paper rubbing somewhere inside).

I beleive a reading of 6.6 Means it is an 8 ohm speaker and I picked up an eminence delta 15lfa at a good price that I was planning to throw in there but after doing some research I decided I should ask some questions.

The speakers were wired in parallel by the way. Also the cab is not ported and has a baffle between the two speakers with a two inch air gap on the right side looking from the back.

Any insight into the speaker configuration and advice on how to proceed would be very much appreciated.

Thanks
 
#4
Hm. Sealed, that means that you can stick into it any 15" woofer with high Qts (as a rule of thumb, higher than 0.55 or so, with a resonant frequency, fs, about 30-50, xmax over 4mm). There aren't many woofers that kind nowadays.

Choices:
Celestion Pulse 15
Lavoce Fbass-15-20
Eminence Alpha or Beta 15
IIRC, also the FaitalPro 15-PR-300 should work.

The former three may have more of a traditional voicing (boosted mids).
 
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#5
I had 3 Kustom 215's, the ones with tuck 'n roll, sparkle Naugahyde. They had two round ports on the front grill. Never knew they made a sealed 215, so maybe its not a Kustom? Anyway, I used JBL K140's in them, 8 ohm models for a 4 ohm load. Modern equivalent might be the Faital PR-400.
 
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#8
The original 2/15 cabs didn't have ports or labels. The original square magnet speakers were inefficient and didn't really sound very good. They killed with JBLs. Put some modern speakers in there.
 
#9
radbass said:
The original 2/15 cabs didn't have ports or labels. The original square magnet speakers were inefficient and didn't really sound very good. They killed with JBLs. Put some modern speakers in there.
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Actually they probably shouldn't be all that modern. Most modern speakers are designed with ported cabinets in mind (because of the greater efficiency a ported cabinet with a woofer designed for one can yield). Exceptions are some subwoofer speakers (which will usually lack the midrange extension needed to sound pleasing on bass) and some specialty speakers. His best bet are "bass" speakers not explicitly marketed as modern sounding. For instance, SICA has two 15" bass woofers on offer, one named "Smooth" (which can work in a sealed cabinet) and one named "Punch" (which is less suited to a sealed cabinet).
 
#10
Mike Caldwell said:
Is there any numbers on the speaker?
I'm guessing the speakers were 16 ohm for an 8 ohm cabinet and the one that measures 6.6 has shorted voice coil windings and that is the rubbing sound you hear.

The baffle between the speakers is more for cabinet strength and bracing.
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That makes sense to me. The one that reads 6.6 has WHF-5327 printed on the back of the cone but I don’t see any other markings.
 
#11
The numbers on the back of the cone are meaningless.

There are two likely possibilities, either the lower resistance driver is damaged or it is an 8 ohm driver (either reconed or replaced).

Are you sure the cabinet is sealed and doesn’t have a port(s)? A few pictures would help.
 
#12
radbass said:
The original 2/15 cabs didn't have ports or labels. The original square magnet speakers were inefficient and didn't really sound very good. They killed with JBLs. Put some modern speakers in there.
Click to expand...
Hmmm. I can find nothing on the net where it states this. From WIKI: " The original Kustom amps came in a variety of colors including Red Sparkle, Blue Sparkle, Gold Sparkle, Cascade Sparkle (teal), Charcoal Sparkle (grey), Silver Sparkle (white), and Flat Black (which contained no glitter). Eventually the company branched out to produce organs, drums, microphones, and guitars." Every photo I can find shows a front ported cab. This cab should at least be in Nauga of some color. I'm wondering if it is actually a Kasino cab, which Kustom also made, without the Nauga sparkle.
 
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#14
Smooth_bass88 said:
FYI it's called mismatched impedance, not ohms
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Thank you. I don’t like to sound like a dumbass so I will correct my vocabulary.
jnewmark said:
Hmmm. I can find nothing on the net where it states this. From WIKI: " The original Kustom amps came in a variety of colors including Red Sparkle, Blue Sparkle, Gold Sparkle, Cascade Sparkle (teal), Charcoal Sparkle (grey), Silver Sparkle (white), and Flat Black (which contained no glitter). Eventually the company branched out to produce organs, drums, microphones, and guitars." Every photo I can find shows a front ported cab. This cab should at least be in Nauga of some color. I'm wondering if it is actually a Kasino cab, which Kustom also made, without the Nauga sparkle.
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This one is tuck and roll in black. No sparkle.
 
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#15
Here are some pics.

Would it be sacrilege to cut in some ports and throw in some new speakers? I’m a carpenter so I have the skill set required to do this cleanly. I also got it pretty cheap so turning it into something I can use sounds cool to me.

I like doom metal and fuzz pedals. My peavy mark iv wants 2 or 4 ohms. I mostly play by myself. I have one 8 ohm eminence delta 15-lfa that I acquired and I can get another one locally for a pretty fair price if that would be suitable for my needs. If the speaker I have is not really what I need I can go another direction. Thanks
 

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#16
moody said:
I'm going to be the detractor here. If all you have is a 2x15 with one 15 working, and the cabinet itself isn't collectable or special is it worth putting the effort into it? What other cabinets do you have? Could the single 15 work in a smaller, easier to move cabinet.
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I got it cheap and I like how it looks so I want to make it into something I can use. If it isn’t collectible I’ll just do whatever to it. I like projects.
 
#20
agedhorse said:
The cabinet may have been a knock-off back then
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I found some info on a dead site this morning. vintagekustom.com. There was anecdotal evidence that early on Frankie was building these by himself and broke the hand saw he was using to cut the holes so he continued making them without cutting the ports. I’m guessing this means he broke the tip which would have made cutting the smaller homes more difficult but probably not effected the part of the saw used for cutting the larger holes. The thread also mentioned units that went out with no badge.

After reading some other info there I took a closer look at the square back speaker and I guess poor lighting and bad eyes conspired to hide the number on the back. Printed in pale green I can make out most of a number now. The top line is 5815091. The bottom line is harder to make out due to corrosion ???628.
 

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