• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

This is a Journey Into (not as much) Sound

A

-Asdfgh-

Apr 13, 2010
15,362
27,569
UK
#1
The fan on my Ashdown EVO Original was a bit louder than ideal on idle.

It's a 12V 2-wire fan, 60mm, 15mm deep with probably not enough space for a 25mm one. The spec sheet is in cu ft/min at 26.7 and minimally about 36dB. It would have been nice if it was attached via its own Molex, but it's not. I wish I'd added one inline.

I first tried a Noctua. It's rated as up to 23dB full blast but I'd misread the spec sheet and the maximum airflow is about half what is required. When running at idle (low speed), though, it's inaudible unless I put the amp right up against my ear.

In the end, I've opted for a fan with 23.6 cu ft/min airflow and 30dB Max noise. It's quiet enough that my wife (who can hear dog whistles) thinks it is quiet. I can hear it, but it's not bad and definitely quieter than the OEM fan.

I may replace other fans over time.

I might fully kit out my PC with Noctua (it's halfway there).
 
#2
Just be aware that without the static pressure spec, airflow means very little. There is a curve that relates the two values, curves between two fans (ant their performance) can be wildly different.
 
  • Like
Reactions: Balog and Guitalia
#3
agedhorse said:
Just be aware that without the static pressure spec, airflow means very little. There is a curve that relates the two values, curves between two fans (ant their performance) can be wildly different.
Click to expand...
Thanks. Maybe it just wasted £20 and need to put the original one back in.

The original is an ADDA AD0615HS-90A. As far as I can tell 06 is 060mm, 15 is depth in mm, HS is sleeve and 90A - no idea. I couldn't work that out from the data sheets I could find.
 
#5
OEM fan static pressure 0.152 inches (of something) the Noctua, 2.53mm H2O. Which assuming it's H2O for both is 0.152 and 0.01 and ADDA does do fans with that low pressure. The fan that is just put on - no comparable data.
 
#7
-Asdfgh- said:
OEM fan static pressure 0.152 inches (of something) the Noctua, 2.53mm H2O. Which assuming it's H2O for both is 0.152 and 0.01 and ADDA does do fans with that low pressure. The fan that is just put on - no comparable data.
Click to expand...
The static pressure of the Noctua is .10", which means that it's rated CFM is at ~33% lower pressure which affects net airflow.

This is why we are so careful when choosing fans for new designs, because in addition to these parameters, there is also the quiescent current, loop gain and damping of any proportional fan control circuit that's used., as this affects the tracking between temperature and speed.

When all of these are integrated into the design calculations, we get a really good idea of a fan's performance over a wide variety of conditions. This is especially important when an amp must perform into 2 ohm loads at high ambient temperatures yet still maintain the lowest practical noise.
 
  • Like
Reactions: One Way, Lo-E and Guitalia
#8
agedhorse said:
The static pressure of the Noctua is .10", which means that it's rated CFM is at ~33% lower pressure which affects net airflow.

This is why we are so careful when choosing fans for new designs, because in addition to these parameters, there is also the quiescent current, loop gain and damping of any proportional fan control circuit that's used., as this affects the tracking between temperature and speed.

When all of these are integrated into the design calculations, we get a really good idea of a fan's performance over a wide variety of conditions. This is especially important when an amp must perform into 2 ohm loads at high ambient temperatures yet still maintain the lowest practical noise.
Click to expand...
Yes, 0.1". Maths is also not my strong suit tonight as well as general thinking, manual dexterity with screws or being tidy. Hopefully, I am learning something, though.

The Noctua specs say about half the peak CFM of the OEM ADDA fan

The SPL readings in dB at 20cm (simply convenient on my desk and for comparative purposes) and not calibrated, so just for comparison, all at idle are:

OEM (ADDA): 36dB
the other one I'd need to check branding ofB: 27dB
Noctua: 23 or 24dB
Background: 22dB.

In a theatrical show (not theatre, just atmospheric), I don't think 27dB is an issue, but 36dB is potentially annoying. Of course, this assumes that the amp hasn't got hot in the previous section and is now trying to cool down, as then it would be a lot louder, but perhaps the audience too deaf to notice. But idle noise is where I've started this journey into less sound.

The OEM fan is now reattached.

I'm not convinced there's any opportunity to get rubber pads and any additional sealing between fan and case as it's really tight spacing. I'm not convinced it would make any difference. If I tighten the grille it seems to foul the blades, which isn't ideal. I have some rubber washers to space that a little.
 
#9
JimChjones said:
Which one did you end up using?
Click to expand...
I'm back to the OEM. If the Noctua did all the right things based on speeds that aged horse noted and stayed pretty quiet up to maximum I'd be very happy. I'll see if I get chance to rig the Noctua up to a 12V supply and attached to a simple baffle and a similarly sized box to the amp on the back and see how loud it gets at maximum speed, ditto the medium loudness one, just out of curiosity.
 
#10
Some of the earlier Ashdown amps had a switched fan, it would turn on when the sensor measured 70 deg C, but IIRC, later models used a more sophisticated form of fan control because under some conditions the fan couldn't cool the amp down once the temperature got that hot, leading to a runaway condition.

How the fan is being used is also an important part of the cooling solution.
 
  • Like
Reactions: One Way and -Asdfgh-
#11
agedhorse said:
Some of the earlier Ashdown amps had a switched fan, it would turn on when the sensor measured 70 deg C, but IIRC, later models used a more sophisticated form of fan control because under some conditions the fan couldn't cool the amp down once the temperature got that hot, leading to a runaway condition.

How the fan is being used is also an important part of the cooling solution.
Click to expand...
It's billed as 'adaptive'.

Maybe I should either

(1) ask Ashdown if there is a quieter option

(2) clip the wires back up neatly, put all the screws back in and see if it's possible to live with it

(3) find a quieter amp which might have been the backup and use it as the primary for gigs requiring relative silence at times.

I like the sound of the Ashdown well enough - not quite as much as the Warwick Profets I just sold (Silent at idle) but much lighter to lug around.
 
#15
^there shouldn't be a need for a fan at all to keep an efficient <1000W Class D amp from overheating at low to moderate power levels. Not after we've all seen 2x400W class AB amps working just fine without any fans for decades. It's just lazy/penny-pinching design by some manufacturers. A small internal heatsink + fan is way cheaper than a substantial external heat sink that needs no fans.
 
#16
Jerry Catanescu said:
^there shouldn't be a need for a fan at all to keep an efficient <1000W Class D amp from overheating at low to moderate power levels. Not after we've all seen 2x400W class AB amps working just fine without any fans for decades. It's just lazy/penny-pinching design by some manufacturers. A small internal heatsink + fan is way cheaper than a substantial external heat sink that needs no fans.
Click to expand...
Jerry - from your flippant comments, it’s clear that you haven’t designed any commercial class D amps because you do not appear to understand the complexity of the thermal management process and the number of components that need to be included in the cooling algorithm. It’s not just the matter of a bigger heatsink (in almost all cases), but multiple parts that may share a thermal equation but not be located physically together.

This all goes hand in hand with the design duty cycle, the power, the minimum load impedance, the design ambient temperature and the expectation for long reliable service under tough conditions. For a real company, the amp must also pass international safety standards as well as many different EMC standards.
 
  • Like
Reactions: Guitalia, One Way, Bassdirty and 1 other person
#17
Jerry Catanescu said:
^there shouldn't be a need for a fan at all to keep an efficient <1000W Class D amp from overheating at low to moderate power levels. Not after we've all seen 2x400W class AB amps working just fine without any fans for decades. It's just lazy/penny-pinching design by some manufacturers. A small internal heatsink + fan is way cheaper than a substantial external heat sink that needs no fans.
Click to expand...
Have you shared your schematics with amplifier manufactuers?
 
  • Like
Reactions: agedhorse
#19
-Asdfgh- said:
(3) find a quieter amp which might have been the backup and use it as the primary for gigs requiring relative silence at times.
Click to expand...
I know the TC BAM 200 is fanless but I am wary of its reputation and stepping down from 300W to 200W. I've gone from a Tech Sound 1x15 (I still have one 4ohm one as I got low offers on a potential sale) to two 8 ohm TC 2x8s for the sake of ease of carriage and being able to stack them so a speaker is a bit closer to where I have ears, which is not behind my knees,. They are a bit less efficient than the 1x15 indvidually, although not so hugely less paired, according to the specs. Granted 200W to 300W isn't much in terms of audibility, but it could be in terms of headroom. However, they are on offer currently. That doesn't mean I won't try to make the EVO Original quieter is there is a simple option.
 
#20
Apparently, the BAM 200 does have a fan, but it's quiet. 200W is not a lot of juice. 300W isn't massive, but has done the job as often there is PA support. For under £100 it might be a good practice/backup option of quiet.

I haven't had a gig to test how intrusive the Ashdown is. I'm almost tempted to take it to a friend's gig and just leave it on stage and sit in the audience or having them use it for bass to check under load. It makes more sense than trying to tell from on stage.
 

Latest posts

Top Bottom
Back