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Author Topic: Near field use on 87db speakers in a masive room.  (Read 9296 times)

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Offline currly30

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Near field use on 87db speakers in a masive room.
« on: July 29, 2022, 12:17:46 AM »
Looking at getting the Kaiju to run my near field speaker set up on ~87db speakers. My desk is currently set up in one corner of the room. To give a ruff measurements: The fronts of the speakers would be about 6' away from a wall. The backs would be about 30' from a wall. Left side about 5' and right side about 25'. Also the ceiling is 9' high above the desk then take a sharp incline to 14'.  Basically I'm wondering if, in my very unique room situation, the kaiju would be enough for near field use. I am currently using a 75watt SMSL amp and it gets plenty loud. I have it set at about half volume then use my pre-amp to fine control the volume.

Offline currly30

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Re: Near field use on 87db speakers in a masive room.
« Reply #1 on: July 29, 2022, 12:23:41 AM »
Also, a second question. Is it possible to use 2a3 tubes in the Kaiju? Or would it require rewiring the Kaiju?

Online Paul Birkeland

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Re: Near field use on 87db speakers in a masive room.
« Reply #2 on: July 29, 2022, 04:31:29 AM »
For desktop use, the Kaiju would definitely be plenty of power.  We have had many customers in the past use our 2W SEX amp with 87dB desktop speakers for this use.  If your speakers are 8 ohms, you can get out your multimeter and set it to AC volts, then open up a tone generator app and play a 60Hz tone through your speakers until you see 8V on your meter.  That would represent 8W and the Kaiju still has some dynamic headroom beyond that.

The Kaiju is not at all optimized for 2A3 tubes and you would have to replace the power transformer and redesign the circuit to make that work, at which point you'd end up pretty close to a Stereomour.   
Paul "PB" Birkeland

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Offline currly30

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Re: Near field use on 87db speakers in a masive room.
« Reply #3 on: July 29, 2022, 07:00:13 AM »
Thank you the info. I will have to try out putting 8w through my speakers to see how loud they get.

Offline Doc B.

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Re: Near field use on 87db speakers in a masive room.
« Reply #4 on: July 29, 2022, 12:26:35 PM »
They will put out 96dB at 8W. You will find that pretty loud for a continuous tone. Typically an amp only gets anywhere near its maximum output on transients like drum hits, dynamic piano, etc. 
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Offline currly30

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Re: Near field use on 87db speakers in a masive room.
« Reply #5 on: July 29, 2022, 02:53:28 PM »
Good to know that it would only really be using that much power on occasion.

Offline Thermioniclife

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Re: Near field use on 87db speakers in a masive room.
« Reply #6 on: July 29, 2022, 04:48:34 PM »
An S3X at 2w sounds fine in nearfield with Paradigm Atoms and Overnight sensations in my Evil laboratory.
Lee R.

Offline ccmccull

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Re: Near field use on 87db speakers in a masive room.
« Reply #7 on: July 30, 2022, 10:30:31 AM »
And not-so-near-field! (Yes, with a bit of help from subs.)

https://forum.bottlehead.com/index.php?topic=13966.msg127473#msg127473
Colin
{Ortofon 2m Blue > U-Turn Orbit > Eros 2} & {Roon Ropieee RPi4 > hifiberry-digi2-pro > ANK DAC 2.1} > Moreplay > S.E.X. > {{Spendor_S3/5r2 & SVS_SB-1000 (x3)} & Grado_sr325x}

Offline currly30

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Re: Near field use on 87db speakers in a masive room.
« Reply #8 on: July 30, 2022, 01:34:00 PM »
Quick follow up question on testing what 8 watts sounds like.
If I run a 60Hz tone through my speakers and get the Volt meter to read 8V. If I stop the tone and switch to regular music will that represent how loud music will sound coming out of the Kaiju?
When I switched to music from the tone the volt meter dropped to 1V-2V when the music was playing.

Online Paul Birkeland

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Re: Near field use on 87db speakers in a masive room.
« Reply #9 on: July 30, 2022, 04:50:24 PM »
That kind of depends on the settings on the device you're on and the music itself, so that's not a great comparison. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline currly30

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Re: Near field use on 87db speakers in a masive room.
« Reply #10 on: July 30, 2022, 09:57:12 PM »
I suppose that makes sense. Is running a 60Hz signal going to take more power faster than music that focuses more on mids?
« Last Edit: July 30, 2022, 09:58:48 PM by currly30 »

Offline currly30

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Re: Near field use on 87db speakers in a masive room.
« Reply #11 on: July 30, 2022, 10:06:46 PM »
One more question.
I also found the Elekit TU-8900/8600 while looking for a Kit 300B. It seems to be similar to the Kaiju but I haven't been able to find any comparisons between the 2. Does anyone happen to know the differences between them?

Since I own the Mainline the headphone amp on the Elekit would be pretty useless.

Online Paul Birkeland

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Re: Near field use on 87db speakers in a masive room.
« Reply #12 on: July 31, 2022, 05:04:42 AM »
That's a tough question to answer since it's a competitor's product, but I'll try to do my best to give some objective differences from my own perspective.

The Elekit in a way is more like what we used to sell back in the day.  The kit is offered with some budget iron with lots of hints dropped that you should really go for the Lundahl upgrade if at all possible.  We did this with our SEX monoblocks and Paramour monoblocks and we worked with Magnequest to create better iron for those pieces.  There are some missing dimensions to the specs on those stock Elekit amps that I would imagine are rather drastically improved with the Lundahl bits.

The schematic for the 8600 is floating around and it has a vastly more complicated power supply than the Kaiju and active biasing circuitry, but the 300B driver is rather simple and multiple stages.  I would expect less 120Hz noise making it from the power supply to the speaker terminals.  The DC filament supply on this amp is a bridge rectifier and a cap.

The Kaiju has an incredibly simple power supply, very simple 300B biasing, but a more complicated driver stage, which is just a single triode driving the 300B.  The increase in 120Hz noise that you might expect to see at the speaker terminals will be somewhat mitigated by the parallel feed output stage.  The (available) DC filament supply is regulated and keeps Jac at EML happy.

I believe the 8600 with the Lundahl transformers will make more than 8W (maybe 11?), but it also runs pretty high plate voltage.  R114/214 on the 8600 are twice the allowable value on the Western Electric published datasheet, and I have experienced this causing problems with Russian 300Bs in a different amplifier in the past, but YMMV and this is something I have run into in many 300B amps.  With the 12AX7 input stage, the schematic shows either a 50K or 100K volume pot, and I would strongly advise against running a 100K pot into a 12AX7. 

The Kaiju will make less power and requires a bias adjustment to the driver stage, so I would say it's less user friendly.  I think the big advantage to the Kaiju comes if you happen to blow up one of the PC boards, as everything is modular and we can just send out replacement parts pretty easily.  I've seen something like this happen from the wrong 9 pin tube being put into the amp, and a repair like that can be done pretty easily by the builder. 
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline Paul Joppa

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Re: Near field use on 87db speakers in a masive room.
« Reply #13 on: July 31, 2022, 05:35:45 AM »
Music signals have peak voltages that can be 5 times the average, on well-recorded dynamic music. (Much pop music is severely compressed and the peak-to average ratio can be as low as 1.25 ). This is called "headroom." It complicates loudness prediction...
Paul Joppa

Online Paul Birkeland

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Re: Near field use on 87db speakers in a masive room.
« Reply #14 on: July 31, 2022, 05:36:50 AM »
...and the Kaiju has some dynamic headroom above the 8W as well, particularly for short transients. 

PJ and I can pretty much nuke any yes/no question asked on this forum ;)
Paul "PB" Birkeland

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