Speaker Gurus.. i need help

[gustobassman]

So recently i bought some older Eden 15's a few weeks ago and am digging them considerably. Haven't gigged with them yet, because i have one gripe....

On the the D115 (no tweeter) i bought all the notes play evenly across my fretboard (including low D, C, and B on the 5), except for when i fret the F# on the E string and the octave on the D string, and occasionally on C on the A string. I lose all power and get this low farty, grinding sound. Note, this does NOT happen on the D115XLT that i bought too.

BUT, this ONLY happens on those 3 notes. Seriously, i am baffled by this. I can play anything i want except when i hit the F# and the octave. Is this an issue with my bass? It's a '97 Am STD Jazz V, i just had a fret job done about 4 months ago and have only had 3 gigs, but i have done a lot of recording, under a low stress environment (on the bass at least). Is this an issue with 15's?

What the @#$% is this? Any ideas?

[will33]

Try moving the rig to different spots in the room and try playing it outside. C is almost the fifth of the F#. Could be running into some wierd room modes there. Is the problem cab lined inside? May also be hitting some cancellation inside the box at those particular frequencies. Make sure the speaker is screwed down tight. That particular frequency may be exciting some box resonance or something. Try it with a different bass to eliminate that as the problem.

[gustobassman]

Originally Posted by will33

Try moving the rig to different spots in the room and try playing it outside. C is almost the fifth of the F#. Could be running into some wierd room modes there. Is the problem cab lined inside? May also be hitting some cancellation inside the box at those particular frequencies. Make sure the speaker is screwed down tight. That particular frequency may be exciting some box resonance or something. Try it with a different bass to eliminate that as the problem.

Ahh ok... that's an idea.

[gustobassman]

will33.. thanks!

moved cab, sounded better: check
made sure speaker was attached tightly: check
different (p.o.s.) bass, possibly better: not sure

as far as the cab being lined i can feel and see some insulation on the bottom, but when i reach to the sides (through the back port) i don't feel any. Is there supposed to be some in this particular cab?

I did still hear some slight loss and a little bit of the fart even after i moved it, but it was nothing as to where i had it placed before. I can't make a valid judgement call on the other bass as it is a junk beater. It is definitely different having moved the cab. Having been an Ampeg (mainly 10's) user for years, this is my first go at the eden "sound". I'm hoping this isn't it! hahaha

[rpsands]

Sounds like a tuning issue. Might want to try to figure out the tinning freq.

First try blocking one section of port with a piece of wood wrapped with weather stripping. If it goes away with the port half blocked your tuning freq might be too high. Or too low.

[will33]

Originally Posted by gustobassman

will33.. thanks!

moved cab, sounded better: check
made sure speaker was attached tightly: check
different (p.o.s.) bass, possibly better: not sure

as far as the cab being lined i can feel and see some insulation on the bottom, but when i reach to the sides (through the back port) i don't feel any. Is there supposed to be some in this particular cab?

I did still hear some slight loss and a little bit of the fart even after i moved it, but it was nothing as to where i had it placed before. I can't make a valid judgement call on the other bass as it is a junk beater. It is definitely different having moved the cab. Having been an Ampeg (mainly 10's) user for years, this is my first go at the eden "sound". I'm hoping this isn't it! hahaha

Check this out. Boundary Cancellation and Room Modes

Every distance from every boundry (walls, cieling, etc.) is going to cancel out and/or reenforce some frequency, usually in the lows/lowmids in typical size rooms. It means placement matters and you're going to sound a little different in each place you setup and play. Your particular setup just happened to hit the F# and it's tritone pretty bad. This kinda stuff can make or break you when setting up subwoofers in a PA system.

Your cab should be fully lined. Having it on the back wall is better than nothing. There are cancellations with the speaker inside the box just like there are with the rig in the room. The lining helps smooth that out.

[will33]

Originally Posted by rpsands

Sounds like a tuning issue. Might want to try to figure out the tinning freq.

First try blocking one section of port with a piece of wood wrapped with weather stripping. If it goes away with the port half blocked your tuning freq might be too high. Or too low.

+1

Another possibility.

[gustobassman]

Originally Posted by will33

Check this out. Boundary Cancellation and Room Modes

Every distance from every boundry (walls, cieling, etc.) is going to cancel out and/or reenforce some frequency, usually in the lows/lowmids in typical size rooms. It means placement matters and you're going to sound a little different in each place you setup and play. Your particular setup just happened to hit the F# and it's tritone pretty bad. This kinda stuff can make or break you when setting up subwoofers in a PA system.

Your cab should be fully lined. Having it on the back wall is better than nothing. There are cancellations with the speaker inside the box just like there are with the rig in the room. The lining helps smooth that out.

I think you hit it on the head. I'm in my oddly shaped living room and i can see that being the cause. As i moved the cab closer to a wall it lessened a bit and completely went away when i placed it in from of my open patio door. It might be that the rear port and where to place the cab is throwing me off. I'm used to sealed ampeg cabs and my front ported 610HLF. When i run the 2 - 15's together i don't notice it, but then again i might not have had them set up where i got the fart to happen with the single cab.

[will33]

Theoretically port location doesn't matter but if your box is tuned 45-50hz as many are, your F#'s fundamental is also right in there. It's harmonics are multiples of that frequency. If you also just happened to be setup 1/4 wavelengths distance from a wall at that very same frequency, you can pretty much smear out your F#. If the problem goes away by changing rig placement, I wouldn't mess with the tuning port.