petetexas Posted February 15, 2023 Share Posted February 15, 2023 How does a 4 or 8 ohm switch work on the back of a cab , when you only have one speaker of 4 or 8 ohms in the cab ? Quote Link to comment Share on other sites More sharing options...
Baloney Balderdash Posted February 15, 2023 Share Posted February 15, 2023 (edited) Passive transformer? Just a wild guess, I am not exactly an electronics expert. Edited February 15, 2023 by Baloney Balderdash Quote Link to comment Share on other sites More sharing options...
BigRedX Posted February 15, 2023 Share Posted February 15, 2023 Anything that doesn't involve tapping the speaker coil is going to be wildly inefficient and wasteful of energy. 2 Quote Link to comment Share on other sites More sharing options...
basstone Posted February 16, 2023 Share Posted February 16, 2023 How odd. Multi speaker cabs often have the capability to switch between series and parallel connection to match to the amp. If there is only one driver speaker the switch possibly adds a series or parallel resistor which only makes any sense if connecting to a valve amp? It might be worth opening up the cab to see what the switch does Quote Link to comment Share on other sites More sharing options...
petetexas Posted February 16, 2023 Author Share Posted February 16, 2023 Hi , The Hartke HD112 cab is a 1x12 cab , and has a switch on the back for 4 ohms or 8 ohms , Pete Quote Link to comment Share on other sites More sharing options...
wateroftyne Posted February 16, 2023 Share Posted February 16, 2023 Did someone say 'Accuswitch'? 😄 1 Quote Link to comment Share on other sites More sharing options...
Woodinblack Posted February 16, 2023 Share Posted February 16, 2023 2 hours ago, basstone said: If there is only one driver speaker the switch possibly adds a series or parallel resistor which only makes any sense if connecting to a valve amp? It doesn't make any sense regardless of the type of amp it is connected to, your resistor would have to match the wattage of any speaker it was connected to as half of your power would be going to heat up the resistor, which means it needs to be very big and bolted to some metal to get rid of the heat and you are wasting half of your power. So if you have a valve amp, connect it to the correct impedance output, and if you have a solid state amp, you can put more power into the speaker, and use more power, just to throw away that power heating a resistor, giving you the same volume if you had connected it without the resistor. The Harkte has a dual voice coil apparently, so I guess you are only using half of it in one of the modes. 2 Quote Link to comment Share on other sites More sharing options...
basstone Posted February 17, 2023 Share Posted February 17, 2023 10 hours ago, Woodinblack said: It doesn't make any sense regardless of the type of amp it is connected to, your resistor would have to match the wattage of any speaker it was connected to as half of your power would be going to heat up the resistor, which means it needs to be very big and bolted to some metal to get rid of the heat and you are wasting half of your power. So if you have a valve amp, connect it to the correct impedance output, and if you have a solid state amp, you can put more power into the speaker, and use more power, just to throw away that power heating a resistor, giving you the same volume if you had connected it without the resistor. The Harkte has a dual voice coil apparently, so I guess you are only using half of it in one of the modes. Totally agree with you, but if the switch is there just thinking out loud really. I didn't know about the Hartke speaker with the dual voice coil. It would be good to hear what it is actually doing but opening up the cab 🙂 Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted February 17, 2023 Share Posted February 17, 2023 Tech Soundsystems did a 1x15 that had a 2/4/8 ohm switch; I remember opening it up and I'm sure it was dual coil. 1 Quote Link to comment Share on other sites More sharing options...
Baloney Balderdash Posted February 21, 2023 Share Posted February 21, 2023 (edited) On 17/02/2023 at 00:21, Woodinblack said: It doesn't make any sense regardless of the type of amp it is connected to, your resistor would have to match the wattage of any speaker it was connected to as half of your power would be going to heat up the resistor, which means it needs to be very big and bolted to some metal to get rid of the heat and you are wasting half of your power. So if you have a valve amp, connect it to the correct impedance output, and if you have a solid state amp, you can put more power into the speaker, and use more power, just to throw away that power heating a resistor, giving you the same volume if you had connected it without the resistor. The Harkte has a dual voice coil apparently, so I guess you are only using half of it in one of the modes. Rather than only using half of the dual voice coil couldn't it be a case of either using the dual coil in respectively parallel and series mode of the two coils, seems to make the most sense to me? Edited February 21, 2023 by Baloney Balderdash Quote Link to comment Share on other sites More sharing options...
Downunderwonder Posted February 21, 2023 Share Posted February 21, 2023 25 minutes ago, Baloney Balderdash said: Rather than only using half of the dual voice coil couldn't it be a case of either using the dual coil in respectively parallel and series mode of the two coils, seems to make the most sense to me? There is simply no way to swap equal loads series to parallel and achieve a factor of 2 change. 2X in series 0.5X in parallel. In the same way a 4 ohm 410 can't be rewired to be 8ohm. 2 Quote Link to comment Share on other sites More sharing options...
wateroftyne Posted February 21, 2023 Share Posted February 21, 2023 Re: my slightly vague ‘AccuSwitch’ reference earlier, this was a minor scandal about 20 years(!) ago, in which respected cab builder Accugroove added a mysterious sealed black box to their cabs which they claimed offered switchable impedance. It was swiftly identified as snake oil. A very strange move. I’m sure @Bill Fitzmaurice remembers that one! Quote Link to comment Share on other sites More sharing options...
Baloney Balderdash Posted February 21, 2023 Share Posted February 21, 2023 22 minutes ago, Downunderwonder said: There is simply no way to swap equal loads series to parallel and achieve a factor of 2 change. 2X in series 0.5X in parallel. In the same way a 4 ohm 410 can't be rewired to be 8ohm. Right, I wasn't thinking that properly through. Thanks for correcting me. Quote Link to comment Share on other sites More sharing options...
Dood Posted February 21, 2023 Share Posted February 21, 2023 12 hours ago, wateroftyne said: Re: my slightly vague ‘AccuSwitch’ reference earlier, this was a minor scandal about 20 years(!) ago, in which respected cab builder Accugroove added a mysterious sealed black box to their cabs which they claimed offered switchable impedance. It was swiftly identified as snake oil. A very strange move. I’m sure @Bill Fitzmaurice remembers that one! I do! I remember that well! Quote Link to comment Share on other sites More sharing options...
Dood Posted February 21, 2023 Share Posted February 21, 2023 Hartke’s cabinets (112) did indeed use a driver with two coils and a switch to select 8 or 4 ohms operation. It wasn’t a dummy or resistive load. Quote Link to comment Share on other sites More sharing options...
Downunderwonder Posted February 22, 2023 Share Posted February 22, 2023 4 hours ago, Dood said: Hartke’s cabinets (112) did indeed use a driver with two coils and a switch to select 8 or 4 ohms operation. It wasn’t a dummy or resistive load. Adds up to only one coil used in 8 ohm operation, other coil becoming dead weight. Quote Link to comment Share on other sites More sharing options...
warwickhunt Posted February 22, 2023 Share Posted February 22, 2023 7 hours ago, Downunderwonder said: Adds up to only one coil used in 8 ohm operation, other coil becoming dead weight. Indeed. IIRC the Tech Soundsystems 115 used a light weight Sica driver (spelling could be wrong) which made the cab a very reasonable weight. Quote Link to comment Share on other sites More sharing options...
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