GK 700RB to run a SVT-810E and a SVT-215E together(810 has maybe 1/2 the gain and is muddy vs 215)

Discussion in 'Amps and Cabs [BG]' started by SamTheToolMan, Jun 23, 2021.

  1. SamTheToolMan

    SamTheToolMan

    Jun 23, 2021
    Ive been playing my GK w/the SVT810 and Luv it, Got an opportunity to pick up an SVT810E and couldnt pass it up, thinkin, "now that tone and EQ would balance so well together with them both running from the the 700RB,...I cant wait!)
    The dude i got it from only played it through the #1 input (top 4 -10's) as he said his amp wasnt big enough to run all 8. :eyebrow:
    To make a long story short, Ive tried hooking it up with both configurations using 1/4" non-shielded in dual mode and speakon for all 8 to run with one output feed to each cab,(also both the speaker outs and also Speakon outs) from the GK 700RB, regardless of which type of jack set up, either on the head and/or on the 8-10 and 2-15, the 8-10 has maybe half the gain, (more like 1/4 the gain) as the 2-15 and is quite muddy in comparison as well.
    Ive read up on both manuals and pretty sure my ohms and jack selection and cabling is correct, but something has got to be up. I did do a visual check of the 8-10 input board for any evidence of a burnt board or bad solder joint but did not pull connectors nor DeoxIt, so thats my next step. Just was hoping for anything else particular maybe any of you could either suggest or have a way or specs to ohm out the board or anything else/ read smthng here i may be overlooking or completely am unknowledgable of.
    Please Help.
    Ihave limited time as it is for "my time" and would luv to speed up or simplify my troubleshooting and get to making some noise.
    Thanks
    Peace
     
  2. Wasnex

    Wasnex

    Dec 25, 2011
    Pretty sure the 700RB is rated for 4 ohms minimum. So you can only run one 810 with this amp. The 810 is 4 ohms all by itself.


    classic-svt-810e-8x10-800w-4-ohms-hd-4-50159.jpg

    The speakON and bottom 1/4" jacks are tied together. You should be able to plug into either and get all 8 speakers to work.

    The top 1/4" jack has a switching contact. When you insert a plug into the top jack it breaks the cab down into two 8 ohm 410s. The idea is use the top jack for one amp, and use one of the bottom jacks to plug in a second amp.

    You need to figure out if switching contact in the top jack is bad. Also I would suggest confirming all of the drivers are good and wired with the proper polarity.


    To check polarity, remove the front grill and then plug a 1/4" speaker chord into one of the bottom 1/4" jacks. Short a 9V batter across the terminals of the other 1/4" plug. All speaker should move in the save direction. If you put the battery negative on the sleeve and the battery positive on the tip, the speakers should move out from the baffle. If you turn the battery around, the speakers should all move in.
     
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  3. Matthias

    Matthias

    May 30, 2000
    Vienna, Austria
    So it is. Only one fridge possible.
    We have a setup with an Ampeg 215 and an Ampeg 810 driven by 2 Ampeg SVT-3 Pros in our reharsal studio. This results in a huge wall of sound. Meanwhile I prefer using only one cab, this sounds more focused to me (and is plenty loud anyway).
    And I prefer my 700RB over the Ampegs, but that's just my taste...
     
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  4. SamTheToolMan

    SamTheToolMan

    Jun 23, 2021
    :bookworm::bookworm:So the cab ive been playing through and love is an ampeg classic 2-15, i made a typo, apologies,...
    the "new" one is the 8-10. Upon further investigation here, seems to me to be wired wrong anyway hence the negative gain.(thankfully did not damage my 700RB baby)
    Anyway, wondering if since gonna go through each driver and fix wiring anyway on the 8-10, im hoping to find a diagram or way i can wire it for 8ohm since the GK manual says its safe to run a 4 ohm and an 8ohm according the the manual. Also worth mentioning, the SVT810E manual shows a "split mode" (two Amps feeding), but using the top 1/4' and 1/4" dual mode directly underneath upper 1/4' input and creating 8ohms,( which according to GK) is a safe rig to run with the 2-15. Id run one of the two speakons outs from GK to the (only input) being a 1/4" on the SVT-215, Then run one of the 1/4" speaker out's from GK to upper #1 1/4" 4-10 Dual Mode on SVT-810 and the other 1/4" speaker out of GK to #2,( the lower 1/4") Dual Mode or Mono Mode, Just feeding all from the 700RB vs two separate heads. Maybe, hopefully if need to re/wire 810 anyway, i can find a diagram to have it be an 8ohm cab all the time where what im reading , would be a safe way to just always have it as an 8ohm cabinet and be able to have the Wall of Sound...:bookworm:
     
  5. Wasnex

    Wasnex

    Dec 25, 2011

    This is straight from the 700RB manual: "One 4 Ohm and one 8 Ohm together is not recommended." The minimum impedance for this amp is 4 ohms. One 4 ohm and one 8 ohm cab in parallel with give you 2.67 ohms.

    The original wiring for the 810E puts eight 32 ohm drivers in parallel. 32/8=4 ohms. If you do series parallel you will get 16 ohms. 8 ohms is not possible.
     
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  6. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    This would be a good time to stop screwing around without understanding what you are doing before you damage your amp.
     
  7. Gearhead17

    Gearhead17 Supporting Member

    May 4, 2006
    Mount Prospect, IL
    SamTheToolMan - You have two of the smartest people on here giving you advice. Please listen to them. Otherwise, you will be spending money on repairs and/or new equipment.
     
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  8. Dave W

    Dave W Supporting Member

    Mar 1, 2007
    Westchester, NY
    I'm going back well over a decade on this one all from memory...

    I'm pretty sure you're reading about the GK bi-amp feature. It's meant to run a GK bi-amp capable cabinet, and there is a small 8ohm 50w amp dedicated to running the tweeter of those particular cabinets. It is not meant to run a whole speaker cab, let alone a fridge like an 8X10 (or even half of the 8X10).

    The only GK amp I'm aware of off the top of my head that can do what you want is the 2001 RB (it's got dual power amps) or to some extent, the 800RB which has a 4ohm 300W amp and an 8ohm 100W amp.
     
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  9. mouthmw

    mouthmw

    Jul 19, 2009
    Croatia
    For crying out loud, do not run both of these cabs together with a GK 700RB.. :rollno:
    Ampeg 810 is a 4 ohm cab. Ampeg 215 is a 4 ohm cab.
    Run one or the other. Your head isn't designed to go under 4 ohm load.

    Don't try to rewire the 810 cab to be 8 ohm either, it doesn't work that way, you'd have to swap out drivers anyways. Mixing 4 and 8 ohm isn't a good idea for 700RB either.

    Go either 4 ohm single cab, or 2 x 8 ohm cabs. You don't seem to know what you're doing.
     
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  10. Try to choose between the 810 OR the 215.
    I expect either will be good, but different.
    Each cabinet will want a different EQ at the amp to be happy.
    Finding that might help decide which will be best for you and the sound you want.
     
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  11. SamTheToolMan

    SamTheToolMan

    Jun 23, 2021
    Hence the joining a forum full of knowledge and better advice than me and my own mind in the wee hours of the morning, making typos and flipping my numbers and research backwards etc. I am plenty capable of learning as i go , life long mechanic/ custom motorcycle builder/ performance and vintage retoration/ DC voltage expert, also hence why i am trying ask advice and options from more knowledgeable in this so I DONT screw up my gear and cost myself more heartache and headaches and money... Thats all bro,... just working on a vision since have to re-wire the 810 anyway.
     
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  12. SamTheToolMan

    SamTheToolMan

    Jun 23, 2021
    I dont, lolol
    this is why im here asking advice. Thnks
     
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  13. mouthmw

    mouthmw

    Jul 19, 2009
    Croatia
    Why do you think you need to rewire the 810? Is it faulty?

    Anyways, if you want to run 2 x 4 ohm cabs, get a GK 2001RB. That amp can take 2 ohm loads. You could even run 4 x 4 ohm cabs with that amp.
     
  14. SamTheToolMan

    SamTheToolMan

    Jun 23, 2021
    Well, not re-wire completely, but it seems the guy i got it from replaced the first speaker and hooked the red/black/white and blue up wrong, so while im in there, im pulling each speaker to verify he didnt hook any other ones up wrong, looking at the board and solder joints etc for excessive heat, ohming out the other speakers to verify what i (actually have) here and just thought hey, if i can re-configure the series/parallel feeds etc to be able to run both these cabinets together to get the proper or (usable) impedance loads, now would be the time to do it is all. I am also looking at using the GK700RB for a different application and searching out a 2001RB for this vision of the wall of sound.
     
  15. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    The way it came from the factory is the proper way, also the most useful way.

    What you have is an amp that is not suitable for your “vision”.
     
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  16. Wasnex

    Wasnex

    Dec 25, 2011

    IMHO the amp is fine, he just needs two of them to realize his "vision." ;)
     
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  17. Wasnex

    Wasnex

    Dec 25, 2011

    If the cab has non-OEM replacement drivers, I strongly suggest that they be installed in matched pairs. The 810E has four separate sealed chambers and you need identical drivers in each chamber. Then the power handling is determined by the weakest drivers.

    A stock 810E is rated for 800W RMS. So the drivers are rated for 100W each in the available space.

    A few years back people tried installing a pair of Jensen MOD 10-50s in the upper chamber for a brighter sound. This driver has a pretty low X-max and a 50W RMS power rating, so i's likely that it will be mechanically limited to less than 50W below 100hz. If we assume it can handle 30W, then the power handing of the cab becomes 8x30=240W at best. Again, you need matched pairs of drivers in each acoustic chamber. 30W may be optimistic for this driver with bass. A common remedy is to install a large capacitor inline with the MOD drivers to roll of the extreme low end.

    If you use unmatched pairs of drivers in one of the chambers, the power handling may go way down. This is because the stronger driver will tend to dominate the weaker driver. Since the drivers do not balance each other out, excursion will increase.
     
    Last edited: Jun 26, 2021
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  18. Dave W

    Dave W Supporting Member

    Mar 1, 2007
    Westchester, NY
    The 2001RB is not the only amp that can handle a 2ohm load and may prove to be difficult to find, they've been out of production for a while now.
     
  19. groovaholic

    groovaholic Protect your hearing. Supporting Member

    Sep 19, 2004
    Mount Prospect, IL
    @SamTheToolMan - the basics of combining speakers are as follows:

    Unless SPECIFICALLY marked otherwise, the multiple outlets on your amp and inputs into your cab are in parallel.

    The resistance of speakers (the whole cabinet OR the individual drivers within a cabinet) will combine differently based on if they are connected in PARALLEL or in SERIES.

    The resistance of speakers in parallel will divide, while speakers in series will ADD.

    So, your two four ohm cabs would combine to put a 2-ohm load on the amp, and your 700RB is not safe at that load.

    The specific math for parallel is to add the reciprocal of the load; impedance is the reciprocal of the result.
    Two four ohm loads: 1/4 + 1/4 = 2/4, take the reciprocal of 2/4 and you have 4/2, which = 2
    An eight and a 4 ohm load: 1/8 + 1/4 = 1/8 + 2/8 = 3/8, the reciprocal is 8/3 or 2.67 - again, not safe for the 700RB.

    Your 810 has eight 32-ohm speakers wired in parallel: 1/32 + 1/32 +... = 8/32; reciprocal is 32/8 or 4 ohms.

    IF* you could run your 215 and 810 in SERIES, you would have 4 ohms + 4 ohms = 8 ohms, which would be safe for the 700RB, but would put out less power than just going into a single cab.
    (*You would either need a custom speaker cable or a custom connector box to run your cabs in series; I've done this and it's absolutely a hassle)

    As others have recommended, you can pick up a second 700RB and be absolutely safe - with the added benefit that now you can put all 480 watts into EACH cab, and optimize the EQ on each amp for its respective cab.

    Now, about that miswired 810...
    With eight 32-ohm speakers, stock is everything wired parallel for 4 ohms.
    Your amp would be safe with all the speakers in series, but at 256 ohms, your amp would only be putting out a couple watts.

    Lots of cabs combine speakers in series-parallel arrangements, where pairs or columns of speakers are wired in series, then those halves are wired in parallel to reduce the load.

    Doing this, you could make your 810 into a 16 or 32 ohm cab, and limit your 700RB to like 50-85 watts; not enough juice for rock & roll!

    Since you're a mechanic, I'll make this analogy:
    Imagine a car parked on a slick piece of ice; you floor it, and the engine redlines - you'll blow that engine before you ever get where you're going, because there isn't enough resistance.
    Next day, same car is parked with the bumper up against a redwood - you floor it and go nowhere again, this time because there's too much resistance.

    You have good gear, and that gear has a sweet-spot where it wants to run and will sound killer doing so.

    Let it.
     
    Last edited: Jun 29, 2021
  20. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa Boogie, Development Engineer-Genzler (pedals), Product Support-Genz Benz
    Series connected speakers work much more predictably when the speakers are identical.

    When the speakers are not identical, additional variables come into play.
     
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