8ohm or 16ohm

Discussion in 'Amplifiers' started by Fro, Oct 27, 2016.

  1. Fro

    Fro New Member

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    I have an Archon 50 combo on the way. I'm going to try a Celestion Neo Creamback in it. I noticed the stock speaker is a 16ohm. Is there any reason to choose a 16ohm over an 8ohm speaker of the same type?
     
  2. AP515

    AP515 Mostly Normal

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    Only to match impedances. There are probably electrical reasons to design the circuit with 16 ohms, but at our level you just want to match the speaker to the amp. You can run an 8 ohm amp on a 16 ohm speaker and be ok but won't have as much headroom, but never run a 16 ohm amp with only an 8 ohm speaker. It will cause damage.
     
  3. Boogie

    Boogie SuperD

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    The Archon has two (2) speaker jacks and an impedance switch. The selection of speaker impedance is more personal preference than anything since your amp can work with all options. I happen to prefer 16 ohm loads on my PRS amps. You can choose whatever you wish, just change the switch to reflect your speaker. An 8 ohm speaker will work if that's what you want...move the switch to 8 Ohms.
     
  4. elvis

    elvis Hamfisted String Banger

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    There is a subtle difference between how a 16 Ohm and 8 Ohm speaker (even identical models) sounds. Personal preference.

    I generally choose impedance with an eye toward combining speakers. There is pretty much always at least one time that I will want to run two in parallel. I generally go for 8 Ohms, as my amps tend to have at least 8 and 4 Ohm capability.

    The Archon is cool in that it will also take 16. So you almost can't go wrong. Note that to parallel an extension cab with the internal 16 Ohm speaker, you would want a 16 Ohm cab.
     
  5. dmatthews

    dmatthews Dave's not here...

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    Yup, as stated you just need to match.
    I run my Custom 50 combo with the 16 ohm internal along with a 16 ohm 2x12 at the same time. The switch is in the 8 ohm position.
    Lovely!
     
  6. n24re

    n24re Enjoying the ride...

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    The big issue you will find is as the load of the amp ( 8 or 16 ohms ) changes so will the power output and the "clean" headroom. Most of the tube amps we know and love with an impedance select switch change the bias level of the final power stage to avoid going into saturation ( distortion ) too soon and over heating the tubes.

    In the event you are a clean tones player ( not the Arcon's selling point ) the higher impedance is a better choice as this gives the amp a lot more headroom before saturating. If your Archon has a switch to allow an 8 ohm load it will break up sooner and at lower volume levels with the 8 ohm speaker typically...some amps compensate to try and perform the same regardless of load but not most tube amps.

    Now if it does NOT have a switch and you run an 8 ohm speaker when the final stage is needing 16 ohm you will cause 2X the power to travel into the output stage. This will cause a lot of heat and a lot of distortion very early in the turning of the volume knob. It will sound awesome....right before all the magic smoke pours out of the cabinet!

    Always remember... Power = voltage squared / impedance...so as impedance halves power output doubles.

    Hope that wasn't too nerdy.

    Steve


     
  7. watelessness

    watelessness New Member

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  8. aristotle

    aristotle New Member

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    Actually, not really. Matching the speaker impedance with the output Impedance of the transformer is done to maximize power transfer to the load (the speaker). Mismatches cause reflections at the end of the transmission line (the speaker end), which travel back and hit the power transformer, which, in some cases, can cause the transformer to fail in a way that causes all sorts of mischief at the output stage. You certainly are not increasing output power or power transferred to the speaker by lowering (or raising) the impedance below (or above) the transformer output impedance. If you measure the power transferred to the speaker if you suddenly halved the speaker impedance, you would get less power transferred to it, not more. By altering the impedance, more power is reflected back (the voltage across the terminals adjusts automatically, and in a way that the power transfer is less). The danger typically isn't at the speaker, but at the output transformer at the amp.

    Having said that, a 2:1 mismatch in either direction isn't going to hurt anything with any PRS amp I've ever seen. In fact, lots of people purposefully create a mismatch because they like the way it sounds, and speakers are only at their rated impedance at one particular frequency and depending on what note you are playing, the speaker can be pretty far off of the spec'd impedance.
     
  9. n24re

    n24re Enjoying the ride...

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    I always forget about that output transformer!!!!

    Good point as that does isolate the output transferring the power through the transformer. In a Class A amplifier that I am used too the output load (speaker ) is directly connected to the output (collector).

    These tube amps are too complicated for a transistor kid like me :confused:
     

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