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New Guy Signing In (and asking for help) [message #9000]

Thu, 08 November 2007 15:55

bhall
Messages: 6
Registered: November 2007
Location: Indianapolis

Junior Member

Good afternoon. I stumbled upon this forum a couple of weeks ago, and let me compliment the moderators and members on what a neat forum you have developed. Friendly, informative, helpful - and lots of eye candy on the website. I will pre-qualify any stupid questions I may ask by admitting I am a drummer who just happens to share your passion for vintage Kustom T 'n R goodies. Any talk of "ohms", "loads", "impedance", etc., may as well be in Martian as far as my comprehension goes, which brings me to my first round of stupid questions.

I recently acquired a K150-5 PA amp that I expected would come with the matched 4 x 8" speaker columns that were offered with this system. When I went to pick it up, I was surprised and delighted to find two 4 x 12" columns came with the amp. Only drawback was that one speaker had been removed from one of the columns. Now, for the questions:

1. The speaker that needs to be replaced is a CTS 8-ohm, 12�. Markings on the magnet are 5812218 and 038-0011-00, but I don�t know which one is the model number. Markings on the back of the cone are 12373. In reading some of the earlier threads, it appears Eminence makes a suitable replacement, but I can�t find a cross-reference. Can anyone recommend a good replacement?

2. Now it gets scary (for me). Since these were not the mating columns that originally came with the amp, I want to make sure the speakers are wired for optimum compatibility with the amp. The speaker outlet jack panel on the amp reads "one 8-ohm load or two 16-ohm loads". I will be trying to drive two cabinets, each containing four 8-ohm speakers and would appreciate any recommendations you may offer.

Many thanks!!

Bill

[Updated on: Thu, 08 November 2007 15:57]

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Re: New Guy Signing In (and asking for help) [message #9001 is a reply to message #9000]

Thu, 08 November 2007 18:21

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

Hey Bill, welcome to the board.

What are you going to be using the amp and speakers for? Vocals, guitar, pre-recorded music?

If you just want to replace the one speaker, then almost any 12" rated for at least 25 watts will serve fine in there. I'm sure that some of the other guys will have specific brands and models for you to consider, but it's only one speaker in an array of eight. Almost anything will blend in with no problems.

As for your impedence question, you're gonna have to make a few compromises. First off are you sure that the speakers in the cabs are 8 ohms? I thought that most Kustom pa cabs were loaded with 16 ohm speakers. Do you have a way to check them? Any ohmmeter will give you an idea of what is in the cabs.

If they are in fact all 8 ohm speakers, each cabinet of four eight ohm speakers can only be wired to be either 2 ohms (all in parallel), 8 ohms (series parallel wiring) or 32 ohms (all in series). So using two speaker cabinets, you will never get to the eight ohm load that the head is looking for.

You can wire both cabs to 32 ohms and end up with a 16 ohm load on the head (less power), or you can wire the cabs to be 8 ohms and load the head at 4 ohms (may cause the head to overheat).

Hope this helps.

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Re: New Guy Signing In (and asking for help) [message #9002 is a reply to message #9000]

Fri, 09 November 2007 07:08

stevem
Messages: 4733
Registered: June 2004
Location: NY

Senior Member

If your speaker is indeed a 8 ohm model, then the same speaker in up for bid on ebay as I type this. If you type in CTS speakers, and then search under musical instruments it will come up.
my two cents worth would be if I found I had to rewire the cbainets, I would set them up for 32 ohms each, which would be in serise, and that will get you a safe 16 ohm load at the head.
The amp will only put out about 50 watts rms, not its rated 75 but it will not burn up on you, and 8 12" drivers pushed by 50 watts should be ok for you.
Let us know how you do?

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Re: New Guy Signing In (and asking for help) [message #9003 is a reply to message #9000]

Fri, 09 November 2007 11:04

bhall
Messages: 6
Registered: November 2007
Location: Indianapolis

Junior Member

chicagobill and stevem - thank you for your responses. The speakers are clearly marked as 8 ohms (forgot to add that in the original post). I will be using them for home practice and/or small venue vocal PA application, so the series wiring option makes the most sense. Thanks for the link to the speaker auction, as well. Have a great weekend.

Bill

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Re: New Guy Signing In (and asking for help) [message #9007 is a reply to message #9000]

Fri, 16 November 2007 19:07

bhall
Messages: 6
Registered: November 2007
Location: Indianapolis

Junior Member

Update: I won the eBay auction for the matching speaker and have it installed. Took the back off the other column and it is wired in the series/parallel format which would produce an 8 ohm load. Amp has output of "one 8-ohm load or two 16-ohm loads". I will use this as a vocal PA with both speaker outputs, so the "two 16-ohm load" designation is in play. So . . . there are two options.

1) Wire the second column the same as the other in series/parallel producing two 8-ohm loads, or

2) Re-wire both columns in series producing two 32-ohm loads

Questions:

If I go option 1 (two 8-ohm loads), do I stand a serious threat of hurting the amp?

If I go with option 2 (two 32-ohm loads), do I eliminate a lot of flexibility driving them with other amps that may be more compatible?

I'm getting a headache asking these questions that I know nothing about, so I have to be driving you guys and gal crazy. I'll go have a beer and check back.

Thanks, and have a great weekend!!

Bill

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Re: New Guy Signing In (and asking for help) [message #9008 is a reply to message #9007]

Fri, 16 November 2007 23:08

LesS
Messages: 477
Registered: December 2002

Senior Member

Hi Bill,
Here is what I would do:
I would go with option 1 for your K150-5: two 8 ohm loads.

A Kustom K100 is also recommended for a 8 ohm minimum load and I used one for many many hours at 4 ohms. It usually will not hurt the amp, you just get distortion a little sooner as you turn up the volume control.

Putting in larger caps will make the amp a little better at running at 4 ohms.

-Les S

[Updated on: Sat, 17 November 2007 10:41]

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Re: New Guy Signing In (and asking for help) [message #9010 is a reply to message #9000]

Sun, 18 November 2007 11:24

bhall
Messages: 6
Registered: November 2007
Location: Indianapolis

Junior Member

Les S - Thank you. I appreciate your response. If I interpret correctly, the K-150 is rated for a minimum 8-ohm load?

Thanks, again.

Bill

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