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DjOverdose

Planning on changing amps from PP KT120 to SET 2A3

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57 minutes ago, DjOverdose said:

noted on this... will ask the builder what those tubes are for. really have no idea.... 😁 

 

 

Go on line, to Frank's Electron Tube Data pages, and download the data sheets on a 12AT7 and a 5U4GB, and read what they do !!  Also, download data sheets on the 6L6GC, and do your own homework.   No need to bother your builder when the data is readily available. 

 

You VERY MUCH have to bother builder - for a nicely written set of instructions for each and every switch he put on that chassis !!!     

 

Switches improperly positioned - create failure modes.

 

Personally, I am not a fan of tube amps designed for public use, with any user-adjustments on them, other than an on and off switch .  Thank goodness, you are now on top of this from the get - go. 

 

Consider taping the switch instructions, a neatly typed synopsis on  ( or inside ) the amp's bottom plate, ( if its not used for ventilation),  as a back-up in the future, for your grand kids to see. 

 

I also would ask him now for a schematic and operating voltages, so this amp can be easily repaired / maintained  in future decades, without having to reverse engineer his design, by a repair technician.  You are a customer, he will likely be happy to give you that information.

 

Jeffrey

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16 hours ago, dwilawyer said:

It is sensitivity, not efficiency.  It would depend how he has them placed in his room, and his room, on whether they will be right at spec, below,  or even above, right?

room placement will impact the available room gain but the speaker will not change sensitivity no matter where you place it. Sorry if I used the wrong term I always get confused between the two. When you have a speaker it has an efficiency level and you can install that in  any boc you like or horn but that number does not change. A bass reflex may help boot the bass output or a horn can add up to 6db of additional output over a specific range but the efficiency of the driver does not change that is set by the driver design/build. So I guess sensitivity is a function of the overall loudspeaker system then? I have found factory numbers do not accurately reflect what you get most of the time they always seem to b e high to me generally in the 2 - 4 db range. YMMV as always.

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A Klipsch engineer once wrote on the forum:

  • The sensitivity figures given on the spec sheet refer to the equivalent sensitivity of the speaker in an average listening roomAn asterisk now informs consumers of this on most spec sheets.  I think this must be some kind of crunched average, because the location in the room makes a difference, and moving the speaker from out in the room to snug in a corner increases the output by 6 dB.
  • The engineer went on to say to get anechoic sensitivity, subtract 4 dB from the spec sheet figure. 
  • IMO, measuring sensitivity at 1K Hz only would be misleading and useless.
  • I believe Klipsch measures across the full advertised bandwidth of the speaker.

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37 minutes ago, garyrc said:

A Klipsch engineer once wrote on the forum:

  • The sensitivity figures given on the spec sheet refer to the equivalent sensitivity of the speaker in an average listening roomAn asterisk now informs consumers of this on most spec sheets.  I think this must be some kind of crunched average, because the location in the room makes a difference, and moving the speaker from out in the room to snug in a corner increases the output by 6 dB.
  • The engineer went on to say to get anechoic sensitivity, subtract 4 dB from the spec sheet figure. 
  • IMO, measuring sensitivity at 1K Hz only would be misleading and useless.
  • I believe Klipsch measures across the full advertised bandwidth of the speaker.

Another Klipsch engineer posted in that same discussion you are referring to that they measure using pink noise per AES standards.  So whatever the standard AES prescribes is what they measure to.

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3 hours ago, moray james said:

room placement will impact the available room gain but the speaker will not change sensitivity no matter where you place it. Sorry if I used the wrong term I always get confused between the two. When you have a speaker it has an efficiency level and you can install that in  any boc you like or horn but that number does not change. A bass reflex may help boot the bass output or a horn can add up to 6db of additional output over a specific range but the efficiency of the driver does not change that is set by the driver design/build. So I guess sensitivity is a function of the overall loudspeaker system then? I have found factory numbers do not accurately reflect what you get most of the time they always seem to b e high to me generally in the 2 - 4 db range. YMMV as always.

It should be -4 anechoic (or free from any room gain). As @garyrc mentions above, the spec sheets say "* Sensitivity in average listening room." (Direct quote from consumer speaker spec sheet I picked at random). So if your measurements are with room gain you have an "average listening room" or slightly better one at only 2db difference. 

 

Efficiency is directly related to sensitivity so it is easily confused, I still do it all the time, but I think efficiency accounts for work in the physics sense.

 

Travis

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I always thought that speakers have no sensitivity only how efficient they can be.

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From Kerry,  the Klipsch Engineer that was quoted above:

 

The test bandwidth is typically 100Hz - 10kHz using pink noise.  The 100Hz cut-off is just a limitation of the test chamber. 

 

Kerry 

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There seems to be much discussion on speaker efficiency in this thread.   I suppose because of use of a JJ 2A3-40 amp.

 

Question :  Does the system gain an additional 3 dB , when a second speaker ( for stereo ) is added??  

 

Is there any measurement continuity .....of a Manufacturer quoting efficiency to the public  testing in mono,  or quoting to the public testing with a a pair of stereo speakers??

 

I often have wondered, about the above.  

 

Ideas, comments??  Thanks!

 

Jeffrey

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Manufacturers test speakers in pairs?

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2 hours ago, Schu said:

Manufacturers test speakers in pairs?

No, not typically, and not determining specifications.  They will listen to a pair speakers for voicing, soundstage,  etc. but that doesn't produce specs. 

 

However, on the pro side they will test groupings of speakers, like in a theater, to determine if they are meeting design criteria for reference levels or certification specs like for Dolby and THX, and actual real coverage patterns (seats to the far side of a theater, seats in the rear, etc.).  

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that's pretty what I assumed... thank you

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just want to uodate this thread... got my 2a3 amp already and boy it does not disappoint! now i know what it sounds like when they say youll be surprised what a few watts can do. its still in the break in period but it sound good already. though the bloom is still not there but the voice... the voice.... its like they are just right in front of you. comparing it with my kt120 amp, the kt120 feels like its too excited to show off but your trying to hold it down. the highs sometimes goes too high but the lows and the thump are really there. while the 2a3 is like the guy in your neighborhood who takes his time walking like his not in a hurry and appreciates everything he see's around him. everything seems to he balanced listening to the 2a3. its so quite that theres very little to no hum at all. the details and nuances are more pronounced in tye 2a3 amp. 

 

probably it is because of the sensitivty of the speakers as well. its easy to be driven thats why when im using the kt120, the hum is more evident compared to the 2a3. also the kt120 is much louder its like even playing at the same volume level, the kt120 feels like its shouting while the 2a3 is just telling you a good story. 

 

Its not a night a day difference but the 2a3 is just dead silent and clean. what more if its totally broken in.  maybe if i pair the kt120 with a speaker that has an 85db or 87db probably it will sound much better since itll be flexing its muscles to move those woofers in and out... 

 

I will be replacing the 6n3c with kt66 and the 5u4gb with 274b and hope they will sound nicer. 

 

thanks guys for all the replies.... 

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Very cool... what are you pairing them with again?

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17 hours ago, Schu said:

Very cool... what are you pairing them with again?

its powering a pair of RP280F. 

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On 7/10/2019 at 6:08 AM, Jeffrey D. Medwin said:

 

 

Question :  Does the system gain an additional 3 dB , when a second speaker ( for stereo ) is added??  

 

 

 

Yes, but ...

 

If the same signal is sent to two identical speakers, through each of the channels of a 2 channel stereo system, the SPL should be 3 dB higher than with just one speaker connected, unless there is significant phase cancellation, or the positions of the speakers are dissimilar. 

 

It's good not to depend on this.  Lets say one desires a 110 db peak from simultaneously struck bass drum, timpani, tom-tom and tam-tam, and that a single channel of the sound system is reliably 1 dB below clipping with one speaker connected.  If the recording was made with those percussion instruments dead center, at the rear of the orchestra (a frequent arrangement), adding an identical second channel should increase the SPL by about 3 dB, providing additional headroom, since the burden of reproducing them would be divided equally between the channels.  But if all those percussion instruments were all the way over to one side (as they were in an orchestra I once played in), the second channel would not be doing full duty, so the SPL would not gain a full 3 dB.

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