Ampeg svt cl fan question

#46
LetItGrowTone said:
@spatters, the CL fan *sucks in through the grill cloth* and blows out the back.
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JuanB said:
On my CL, the air blows out the front. It came this way from the factory.
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:roflmao: :roflmao: :roflmao: I wonder if Ampeg built them both ways? If so, that would validate my theory that very little time was spent on the solution!

Whichever way it goes, it's a lot less efficient to push or pull air through grille cloth.
You can easily feel and hear this without instruments.
Detach the fan from the grille and feel the airflow with your hand.
Then push the fan up against the grille cloth and feel what's coming through the cloth.
Not only will the airflow be a fraction of what it is before -- the fan will be louder because it's trying to push air through the grille.

Funkdified said:
So after much searching to find comparable fans I found this.
https://www.alliedelec.com/product/8500n-8500n/70105498/

36cfm and 34db. iPhone db app says stock is 70db.
Click to expand...

If those are the dimensions of the stock fan, that'll work...but it may not be any quieter than the one OP already has. The dB reading on phone apps isn't very accurate. More importantly, small variations in distance will overwhelm the actual difference in noise level! (The standard is to measure the fan in free air at exactly 1 meter, with background noise < 15 dBA.)
CFM measurements, however, can easily be compared.
I would be reasonably confident that, if it weren't blowing through grille cloth, you could use a fan rated at half the CFM. I would also verify this with my contactless temperature probe before running with that modification.

(Fans in qty 1 are much cheaper on ebay than from electronics supply places, even for the same item...search "80mm 120V fan" for a start.)

Another approach would be to take the fan off the front grille, and mount a larger fan on the back grille, pulling air through the head and out the back.

First, fans move air proportional to their speed, and noise is proportional to fan speed -- but they move air at roughly the cube of their diameter (somewhat less in reality), so going from a 80mm to a 120mm diameter fan will move over twice as much air at the same RPM and noise level! Alternatively, a 120mm fan will be much quieter than an 80mm fan that moves the same CFM.

Second, pulling air out the back allows air to flow through the entire area of the front grille, instead of just a tiny 80mm circle in front of the fan...dramatically increasing airflow, even if the fan remains at the same CFM.

(Before hacking on your amp, please read my disclaimer in my first post in the thread.)

agedhorse said:
The weave on the cloth is pretty open.
Click to expand...

Not as open as a metal wire grille, though :)
 
Last edited:
#47
spatters said:
:roflmao: :roflmao: :roflmao: I wonder if Ampeg built them both ways? If so, that would validate my theory that very little time was spent on the solution!

Whichever way it goes, it's a lot less efficient to push or pull air through grille cloth.
You can easily feel and hear this without instruments.
Detach the fan from the grille and feel the airflow with your hand.
Then push the fan up against the grille cloth and feel what's coming through the cloth.
Not only will the airflow be a fraction of what it is before -- the fan will be louder because it's trying to push air through the grille!



If those are the dimensions of the stock fan, that'll work...but it may not be any quieter than the one OP already has. The dB reading on phone apps isn't very accurate. More importantly, small variations in distance will overwhelm the actual difference in noise level! (The standard is to measure the fan in free air at exactly 1 meter, with background noise < 15 dBA.)
CFM measurements, however, can easily be compared.
I would be reasonably confident that, if it weren't blowing through grille cloth, you could use a fan rated at half the CFM. I would also verify this with my contactless temperature probe before running with that modification!

(Fans in qty 1 are much cheaper on ebay than from electronics supply places, even for the same item...search "80mm 120V fan" for a start.)

Another approach would be to take the fan off the front grille, and mount a larger fan on the back grille, pulling air through the head and out the back.

First, fans move air at roughly the square of their diameter, so going from a 80mm to a 120mm diameter fan will move over twice as much air at the same RPM and noise level -- and a 120mm fan that moves just as much air will be much quieter.
Second, pulling air out the back allows air to flow through the entire area of the front grille, instead of just a tiny 80mm circle in front of the fan...dramatically increasing airflow, even if the fan remains at the same CFM.

(Before hacking on your amp, please read my disclaimer in my first post in the thread.)



Not as open as a metal wire grille, though :)
Click to expand...


AFAIK the OEM fan is rated for 30CFM at 35dB(A) on 60hz.

For comparison I believe the OEM equivalent fan for the vintage amps is rated for 60CFM at 37dB(A). This is for a 120x120x25mm fan. Go to a 120x120x38 you can get 51CFM at 25dBa.

I went through the various 80x80x38 fans I could find, and the noise level for 30CFM is pretty consistent from one fan to the next. To reduce the noise, you have go to a lower CFM rating. Going to a deeper fan does not seem to help reduce the noise as much as with the 120mm fans. Mouser lists one 80x80x42mm fan. It is rated for 15CFM at 25dBa. No idea if a deeper fan will fit, but that is only half the original CFM rating.

A better solution (IMHO) is get an amp that is more appropriate for bedroom level practice. Perhaps a V4 or PF-50T.
 
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#48
Funkdified said:
So after much searching to find comparable fans I found this.
https://www.alliedelec.com/product/8500n-8500n/70105498/

36cfm and 34db. iPhone db app says stock is 70db.
Click to expand...

Don't believe the numbers you measured, they aren't even close to accurate. Your numbers tell me this.

The published numbers are essentially free air, at 1M distance, A weighted. As soon as you put it into the enclosure, the numbers will change (sometimes a lot).

See below for how fans are specified:

Important Factors to Consider When Comparing Acoustical Data
 
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#51
LetItGrowTone said:
It could be that someone decided to avoid the dust ring on the *outside* (see some old examples on Reverb) if the fan sucks in, but it doesn't seem ideal to pull the hot air all the way through, and downhill too.
Click to expand...

I'm sure that fans get turned around. Here is the disassembly instructions of the CL from Loud. Page 2 shows the correct air flow direction - from the inside outward through the front panel. The makeup air is supposed to come from the back, past the power tubes, and out the front.
 

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#52
PrinceByTor said:
I’m not too sure if it’s correct, but I believe newer Ampegs will shut down if there is a malfunction in the cooling system. I once bought an SVT 1000 solid state head and when it got delivered wouldn’t run even 5 seconds before it just powered down. I sent it back and found out from the seller that the fan had a problem with it and triggered a shutdown.
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So is it normal for that SVT 1000 to have a continuous running fan, even when it’s first powered on?
 
#53
Cory rich40 said:
So is it normal for that SVT 1000 to have a continuous running fan, even when it’s first powered on?
Click to expand...

In my experience, yes. I have yet to own an Ampeg head that does not have a fan immediately turn on. Also, I cannot remember for sure, but I believe that with my SVT-450H head it would spool up faster as the transformers got hotter. Like I said, I did not have the 1000 for more than a couple days before I sent it back. I hope that helps.
 
#54
PrinceByTor said:
In my experience, yes. I have yet to own an Ampeg head that does not have a fan immediately turn on. Also, I cannot remember for sure, but I believe that with my SVT-450H head it would spool up faster as the transformers got hotter. Like I said, I did not have the 1000 for more than a couple days before I sent it back. I hope that helps.
Click to expand...
I got a used one that looked to be in mint condition last month. It’s definitely not something you would use in a studio because of the fan. It sounded great. Feel like I’m missing something because I don’t have an ampeg cab though
 
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#55
@beans-on-toast I was wondering about the fan direction and came across this. After further reading in this thread I see you linked to it also. So I am going to assume that there are tons of SVT-CL amps out there with the fan installed backwards if you go by this drawing from Ampeg. I can see this happening EASILY in a production factory setting.
AMPEG SVT-CL AIRFLOW.jpg
 
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#56
Rick_Bass said:
@beans-on-toast I was wondering about the fan direction and came across this. After further reading in this thread I see you linked to it also. So I am going to assume that there are tons of SVT-CL amps out there with the fan installed backwards if you go by this drawing from Ampeg. I can see this happening EASILY in a production factory setting.View attachment 4725311
Click to expand...

Sometimes they are turned around. The amp runs hot and people try different things. I sometimes supplement the SVT airflow with a small desk fan blowing into the back. I use this fan, it's quiet and does a good job.

Caframo Chinook
caframo.jpeg
 
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#57
I was reading this morning older thread this morning and it makes me wonder… can you replace the cooling of an SVT-CL for a quieter, at least as effective, in a simple plug and play/no need for extensive modifications operation? If so, anybody knows what fan to get?
 
#58
Inconnu said:
I was reading this morning older thread this morning and it makes me wonder… can you replace the cooling of an SVT-CL for a quieter, at least as effective, in a simple plug and play/no need for extensive modifications operation? If so, anybody knows what fan to get?
Click to expand...
The noise a fan produces is a function of the physical dimensions, shape of the blades, and how fast the fan turns. A significantly quieter fan is unlikely to have the same air flow and/or static pressure specs. The most important thing for the fan to do is force enough air through the amp to keep the temperature within tolerance. Install a fan with lower air flow and/or static pressure capabilities and the amp may overheat and self-destruct.

IMHO use an OEM fan in the amp. If the fan noise is too high for your situation, get a different amp.
 
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