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Old 14th March 2011, 04:03 PM   #1
sherpa is offline sherpa  United States
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I would love to try a few of your small full range drivers but all of my hand built tube amps need 8 ohm impedance. My single ended transformers only have an 8ohm secondary. your drivers are all 4ohm as far as i can see. seems my only options are to either change output transformers or order 2 pairs and build a bi-polar speaker system. Neither of which are cost effective for me. Do any of your drivers come in 8ohm impedance?
Thanks,
Paul

my amps,
DIYTube ST-35, SE 6EM7, SE EL-84, SE KT-88

Speakers,
Zigmahornets with drivers scavenged from a Yamaha center channel speaker
or the FE-127 Fonken with FE-103 drivers.
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Old 24th March 2011, 01:21 PM   #2
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Quote:
Originally Posted by sherpa View Post
I would love to try a few of your small full range drivers but all of my hand built tube amps need 8 ohm impedance. My single ended transformers only have an 8ohm secondary. your drivers are all 4ohm as far as i can see. seems my only options are to either change output transformers or order 2 pairs and build a bi-polar speaker system. Neither of which are cost effective for me. Do any of your drivers come in 8ohm impedance?
Thanks,
Paul

my amps,
DIYTube ST-35, SE 6EM7, SE EL-84, SE KT-88

Speakers,
Zigmahornets with drivers scavenged from a Yamaha center channel speaker
or the FE-127 Fonken with FE-103 drivers.
+1
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Old 29th March 2011, 04:45 AM   #3
sherpa is offline sherpa  United States
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So does anyone at Markaudio want to answer?
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Old 29th March 2011, 07:00 AM   #4
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IIRC, the Alpair 10.2 is 'rated' at 6 Ohms, though the impedance plot appears to put it generally (well) above this. That is, if the chart for the 10 on the Mark Audio site is for the 10.2...

Edit: It looks like the details for the Alpair 10 on the Mark Audio site are for the previous version. If so, I would like to see the impedance plot for the new version.

Cheers.
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Last edited by rcdaniel; 29th March 2011 at 07:16 AM.
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Old 29th March 2011, 07:35 AM   #5
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CHR70.3 is likely going to be 8 ohm at user request. A12 is nominal 8 ohms. 6 ohms is close enuff to 8 to break into a sweat. Twins of the 4 ohm drivers is not a hardship (twin EL70s in a good cab stun people with their bass capabilities)

But one needs to remember that impedances are nominal. They do not look like a straight line at all.

I just measured 10 Alpair10.2, I'll run downstairs and generate a postible curve.

dave
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Old 29th March 2011, 08:24 AM   #6
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A typical curve from a set of 10 drivers. This would be called an 8 ohm driver. Note that over most of the range it is >8 ohms.

dave
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Old 29th March 2011, 04:37 PM   #7
sherpa is offline sherpa  United States
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Thank you, I would love to do a bi-polar speaker but the extra cost would be hard to justify to the wife.
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Old 17th August 2013, 07:47 AM   #8
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Quote:
Originally Posted by planet10 View Post
A typical curve from a set of 10 drivers. This would be called an 8 ohm driver. Note that over most of the range it is >8 ohms.

dave
Not sure this is the right thread for this but... All of cone impedence graphs I have seen look similar to this. Big spike at free air resonance, followed by a long shallow depression through its midband , and a rise from there to its upper frequency range. Even though the audio output is relatively flat. Does this mean some of the output in a cones upper operating range (highe impedence) is actually from resonance (distortion) ? Just wondering.
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Old 17th August 2013, 08:51 AM   #9
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Why is cone resonance 'distortion?'

Welcome to the myth of 'pistonic' drive units. It doesn't work that way. All wideband drive units produce the majority of their BW through controlled resonance of the cone / cones / parts thereof. Note the word 'controlled.' That is of course the critical point, i.e. how well controlled it is. That's down to the design of the cone, suspension & the motor structure. Many midbass units grab a useful extra octave or so through the same. The top end of the audible BW of many tweeters is also achieved through this. No big deal.
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Old 17th August 2013, 02:58 PM   #10
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Thanks . This forum is the first place I've received a reasonable sounding answer. However, controlled or otherwise, a resonance is not part of the original signal, and I would consider it to be a distortion . In view of the tiny distortion numbers in the most decent components upstream from the speakers in the signal chain, maybe this is why we can always easily hear the difference between live and recorded so easily.
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