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8 ohms cab or make a new one?

Discussion in 'Amps [BG]' started by Hetzer, Apr 4, 2014.


  1. Hetzer

    Hetzer

    Joined:
    Sep 5, 2010
    Hello people! I need a word of advice from you.

    I plan on getting an 2*10 extension cab for my Peavey TNT 115 (redline). This TNT gives 150 W on 4 ohms, and a minimal impedance for output speaker is 4 ohms. The problem is that it is very hard to find 210 cabs on 4 ohms to be found here in Serbia.
    My first question is what would happen and is it recommended that I use something like Hartke 210 TP Transporter cab that gives out 150 W on 8 ohms or something else of that range? Will something burn out, get overloaded, have bad sound, or will it work at all?

    If this isn't the option, then I would have to build my own cab. 10", 4 ohm bass speakers are also scarce here but I found where I can buy Eminence BP 102-4 speakers, 200 W. Are these 200 W too much for my TNT (150 W)? I know that some difference is usual, but I am concerned if this is too much. There is also a chance to find Peavey Sheffield® TVX 1035-4, but it is even a long shot.

    And finally, what are your experiences (good and bad) with building these cabs? What kind of wood (plywood or splinter board), how to calculate dimensions for correct air volume, bottom sealed or opened, screwing or gluing and similar? If you have any useful links, I would appreciate.

    Thanks
     
  2. StraightSix

    StraightSix

    Joined:
    Nov 23, 2011
    "and a minimal impedance for output speaker is 4 ohms"

    There's your answer - 4 ohms is the minimum so use an 8 ohm 210 and you will be fine.
     
  3. Hetzer

    Hetzer

    Joined:
    Sep 5, 2010
    Will that cab give it's bast sound like that? Can amp be somehow abused by long term usage like this?
     
  4. StraightSix

    StraightSix

    Joined:
    Nov 23, 2011
    The amp is rated at 150w into 4 ohms (minimum).

    As it stands on its own it is probably only putting out around 90-100W into the single 15" driver (which is 8 ohm).
    Adding an 8 ohm 210 will drop the impedance that the amp 'sees' to the 4 ohm minimum and you will get the benefit of full power from the amp and much more volume from the extra 2 ten inch drivers.

    The only way you may damage the amp is if the 15 in the combo is actually 4 ohms (it may have been replaced in the past)...have a look at the label on the 15, it will tell you the spec.
    If the 15 is 8 ohms, you can safely add another 8 ohm cab.
     
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  6. christw

    christw Get low!

    Joined:
    May 11, 2008
    Location:
    Dayton OH
    Disclosures:
    Endorsing: J Worrell Bass
  7. Hetzer

    Hetzer

    Joined:
    Sep 5, 2010
  8. christw

    christw Get low!

    Joined:
    May 11, 2008
    Location:
    Dayton OH
    Disclosures:
    Endorsing: J Worrell Bass
    You're right! My mistake... I should have looked at the manual. If it can run a 4 ohm extension in parallel to the 4 ohm internal speaker that means it is 2 ohm safe and it will be just fine with an 8 ohm 210. You could even buy 2 8 ohm 210s and make a giant stack out of it!
     
  9. Jaco who?

    Jaco who?

    Joined:
    May 20, 2008
    Don't know where you are, but here in the states check Music Go Round or GC used for a Peavey 115BVX. Virtually nobody wants one, since it's a 4Ω 15 with no tweet and isn't really full range enough as a stand alone cab for a 4Ω minimum head, so they go for $100-$150. They were pretty much made as an extension for the 2Ω TNT 115.
     
  10. Hetzer

    Hetzer

    Joined:
    Sep 5, 2010
    OK, now I am certain that 8ohm cab is safe. But how much power can amp that gives 150W at 4ohm push through an 8ohm, 150W cab?

    I am in Serbia, that is the probem. I have seen many suitable stuff on Ebay, but shipping is too expensive.
     
  11. christw

    christw Get low!

    Joined:
    May 11, 2008
    Location:
    Dayton OH
    Disclosures:
    Endorsing: J Worrell Bass
    With an 8 ohm extension speaker your amp will put 2/3 it's power into its 15 (~120w) and 1/3 (~60w) it's power into the 210.
     
  12. Hetzer

    Hetzer

    Joined:
    Sep 5, 2010
    Does this mean that with 4ohm extesnion cab, it will be 50/50% power distribution between internal speaker and external one?

    Will this result with lower sound quality (not power) from each speaker, being that only a portion of power is put through them
     
  13. christw

    christw Get low!

    Joined:
    May 11, 2008
    Location:
    Dayton OH
    Disclosures:
    Endorsing: J Worrell Bass
    Yes it does!

    No. With a 115 or 210 extension you will have twice the speaker area and more power from the amp. If anything, it should be louder and capable of more lows.
     
  14. Hetzer

    Hetzer

    Joined:
    Sep 5, 2010
    This really makes sense now. If I use 8ohm 210 extension cab, then more power will go through internal 15'' and mids and highs from 210 will not be so dominant, but very present. It looks like the option I will make.
     
  15. fnordlyone

    fnordlyone Supporting Member

    Joined:
    Jun 12, 2013
    Location:
    south Louisiana
    A minimal impedance means you cannot not go lower than a 4 ohm extension cab into the peavey's output with internal speaker still connected (any cab/cabs rated above 4 ohms is A-okay!). A single 8ohm rated cab is fine or two 8 ohm cabs = 4 ohms together will be okay. The fact that the TNT combo has a single 4 ohm speaker means the head in the Peavey combo is rated to 2ohms. :hyper:
    quote op:
    "If this isn't the option, then I would have to build my own cab"

    You don't have to, but you might Want to! In order to get the most volume, I'd build a cab made of two 8 ohm speakers wired parallel in a single plywood enclosure of 3/4" plywood (no bracing required). This cab will have a 4 ohm rating by having two 8 ohm speakers wired in parallel. Please don't be confused by single speaker ohm ratings versus cab ohm ratings of two or more speakers. If one would build a 2x10 with two 4 ohm speakers, one would end up with a 2 ohm cabinet (lower than your peavey combo's head ext out minimum) or an 8 ohm (wired series) which won't utilize you're peavey's head to full 2 ohm load.

    http://www.talkbass.com/forum/f15/square-back-ampeg-early-70s-cab-dimensions-1032572/
    interior dimensions for a 2x10 ampegy thing
    http://www.talkbass.com/forum/f15/general-rule-2x12-sealed-cab-1034379/
    for a 2x12
    each cab is rated 4ohms and could plug into your peavey ext speaker out.

    I had good results with these two builds,
    fnord!
     
  16. Hetzer

    Hetzer

    Joined:
    Sep 5, 2010
    Things are much clearer to me now, thanks for that. :hyper:
    I'll explore some more, maybe something good comes up.
     
  17. Hetzer

    Hetzer

    Joined:
    Sep 5, 2010
  18. B-string

    B-string Gold Supporting Member

    Joined:
    Nov 21, 2008
    Location:
    Lake Havasu City, Az USA
    Only two ways to make a two speaker 8 ohm cab. Use two 4 ohm speakers series wired or two 16 ohm speakers parallel wired. Can't make a two speaker 4 ohm load out of either one.
     
  19. fnordlyone

    fnordlyone Supporting Member

    Joined:
    Jun 12, 2013
    Location:
    south Louisiana
    can see where the specs on that site would confuse

    Specifications
    Hartke 210TP Specifications
    Type
    Impedance (Ohms) Power Handling Drivers
    SPL
    Frequency Response Inputs
    Weight Dimensions
    Tuned,Tube Port Enclosure
    8 Ohms Impedance
    150 Watts Peak Power Handling 2 Hartke 10TP16 Special Design Aluminum 15", 8 ohm, 75 watt drive units
    94dB @ 1W/1M
    50Hz - 4kHz
    Single 1/4”

    Somebody alert Larry (TBer and founder of Hartke), I believe that's a typo! 15 inch heads in a 10 could cost the company a GM recall where few would return the larger heads!

    B-String is correct.

    If you want a 2x10, to run with your Peavey at most volume, you need a bass cabinet rated at 4 ohms. Unless using 2 ohm speaker heads in series, the only way to do this is with two 8 ohm speakers wired parallel.

    I find this link helpful:
    http://cie-wc.edu/Series_Parallel_9_14.pdf
     
  20. B-string

    B-string Gold Supporting Member

    Joined:
    Nov 21, 2008
    Location:
    Lake Havasu City, Az USA
    I would bet the 16 in "10TP16" stands for 16 ohm drivers. :)
     
  21. fnordlyone

    fnordlyone Supporting Member

    Joined:
    Jun 12, 2013
    Location:
    south Louisiana
    yep
    f!
    the other was a wild copy and paste, I'm sure
     

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