Port Noise Complaint

[4-stringB]

OK, so my title sucks (you young punks wouldn't understand) I have a Peavey 115, with a 1502-4ohm BW. The port is a 4" hole in the front panel. The port makes so much noise that I thought the new basket was bad. Should I enlarge the port, or add another port? How about adding a port tube?? I drive it with a 300w 4ohm Behringer, set for the lowest freqs without using the ultrabass. The amp and the spkr are both 4ohm, the spkr can handle 350 continuous, the amp is not clipping. It all sounds good, except that dang port...Help!...Cheers

[Jaco who?]

I love Phillip Roth. If you're absolutely sure it's port chuffing noises and not something else, download winisd. The beta version ought to work OK for simple diameter/depth port tube calculations.

You'll need to calculate as accurately as possible the cubic ft, load the 1502's parameters into it and see what it comes up with. You can try different numbers of ports at different diameters too, sometimes more ports that are smaller work better than one big one - look at the mach number and get it as low as possible.

You can also measure the depth of the port you already have and play around with different frequency numbers to get an idea of what Peavey thought the box should be tuned to.

Another thought - You say there's a 4" hole. Maybe there's supposed to be a tube in there?

Any guesses by me would be wrong anyway.

[billfitzmaurice]

Originally Posted by 4-stringB

OK, so my title sucks (you young punks wouldn't understand) I have a Peavey 115, with a 1502-4ohm BW. The port is a 4" hole in the front panel. The port makes so much noise that I thought the new basket was bad.

A 4" port is insufficient for a fifteen; two would be required to prevent chuffing. To fix it add a second port, with the duct lengths tripled to maintain the same tuning frequency.

[mid_life_crisis]

Originally Posted by 4-stringB

OK, so my title sucks (you young punks wouldn't understand) I have a Peavey 115, with a 1502-4ohm BW. The port is a 4" hole in the front panel. The port makes so much noise that I thought the new basket was bad. Should I enlarge the port, or add another port? How about adding a port tube?? I drive it with a 300w 4ohm Behringer, set for the lowest freqs without using the ultrabass. The amp and the spkr are both 4ohm, the spkr can handle 350 continuous, the amp is not clipping. It all sounds good, except that dang port...Help!...Cheers

I recommend that you be very careful resolving the title problem with a small diameter tube.

[Mr. Foxen]

I've never had a problem with these cabs, are you totally sure its port noise? When you say the amp isn't clipping, are you meaning the input is not clipping? Because hte power stage still can be if you are cranking lows.

[Rezdog]

Greetings from the North,

LMAO! Great thread title!

Rezdog

[4-stringB]

Originally Posted by billfitzmaurice

A 4" port is insufficient for a fifteen; two would be required to prevent chuffing. To fix it add a second port, with the duct lengths tripled to maintain the same tuning frequency.

The existing port is just the 4" hole in the front panel (13/16 plywood) and there is no duct/tube. Should I add ducts, and if so, what should I make them from, and how long? Straight cut, angle cut, flared??..Thanks for the assist...Cheers...

[4-stringB]

Originally Posted by Mr. Foxen

I've never had a problem with these cabs, are you totally sure its port noise? When you say the amp isn't clipping, are you meaning the input is not clipping? Because hte power stage still can be if you are cranking lows.

I am pretty sure that clipping is not an issue because the Behringer has a VU meter on the input, and a overload LED for the output. The VU never goes over 75% of the green range, and whenever the LED lights up, I'll back off the output volume just a skosh so it doesn't light up again. Thanks for the thoughts...keep them cards and letters coming...Cheers...

[billfitzmaurice]

Originally Posted by 4-stringB

The existing port is just the 4" hole in the front panel (13/16 plywood) and there is no duct/tube. Should I add ducts, and if so, what should I make them from, and how long? Straight cut, angle cut, flared??..Thanks for the assist...Cheers...

Assuming it's properly sized (and I wouldn't, since they didn't get the diameter correct) the duct thickness in this case is that of the baffle. Tripling it would come to about 2 1/4 inches, give or take. PVC pipe is one option, readily available.

[Bob C]

Originally Posted by billfitzmaurice

Assuming it's properly sized (and I wouldn't, since they didn't get the diameter correct) the duct thickness in this case is that of the baffle. Tripling it would come to about 2 1/4 inches, give or take. PVC pipe is one option, readily available.

I don't understand the math here. What am I missing?

[Mr. Foxen]

Is it the TVX 15? That should have a duct, I think it is a little longer than that from memory.

[4-stringB]

Originally Posted by mid_life_crisis

I recommend that you be very careful resolving the title problem with a small diameter tube.

WE ARE BASS PLAYERS. WE DON'T HAVE "SMALL DIAMETER TUBES". Guitar players do...Cheers...

[lbwdog]

PORT NOISE COMPLAINT...he,he,he....... There are more geezers here that get it than I would have thunk!

For those who don't... http://en.wikipedia.org/wiki/Portnoy's_Complaint

I remember first hearing it in Johnny Carson's Tonight Show monologue. Seems like every night he made some joke about it. In fact, I thought it was really spelled that way until I saw the book!

[lindseyp]

Wow, four of us caught the title as soon as we read it. I'm surprised (you guys are old).

[will33]

If the "port" is just a 4" hole in the front of the cab, or any inch hole for that matter, it's tuned way too high. There should've been a tube residing in that hole that extended back into the cab a little ways. (cardboard glorified TP tube or PVC pipe of sorts). The tube may have either come loose/fallen out over the years or was taken out by someone who didn't know what they were doing.