Speaker rattle - unable to find the source

[Flatbass]

Hey all,

I used to have a Hartke B90 combo, a relatively cheap beginners combo with a paper speaker. At some point the amp died and I continued to use it a speaker cabinet. However, recently the speaker started to rattle and I can't find the source of the problem.

The rattle occurs mostly at low frequencies and gets louder with the increase of volume. The speaker sounds fine otherwise, there's just a rattle added to the sound.
I've tried different basses, instrument cables, speaker cables, amps, checked the connections and the rattle is still there.
I took off the metal grill protecting the speaker, and it's still there.
I took the speaker out of the cabinet, and it's still there. In other words, it's not something vibrating sympathetically in the cabinet or room.

There is no visible damage to the speaker. No tears or dents. I don't hear any 'rubbing' or 'grinding' sound when gently pushing against the speaker. The sound really seems to come from the centre of the speaker and may get amplified by the cone.

I have owned the combo/speaker for 13 years and it's been used heavily. On occasions I have used a bigger amp with it than the RMS rating specifies and pushed it quite a bit, but never to the point of distortion. I have never noticed a problem afterwards.
Recently I have transported it using a hand trolley over bumpy roads; I've also bumped it into things many times. I used it to amplify an electric piano. It also fell over once. It once was subjected to a loud, high pitched squeal caused by microphone feedback. It's been used outdoors a couple of times. However, I'm not exactly sure when it started rattling, so I can't say if (and if so, which) any of the events above cause it.

Does any of you have any idea what caused this problem? And more importantly, what I can do to repair the speaker?

Any input is appreciated, as I would really like to keep using this cabinet! Thanks.

[Rune Bivrin]

Check the tinsel leads from the connectors to the voice coil. They could be touching the back of the cone. Otherwise you need to use a finger and press gently around the perimeter of the cone and down by the dust cap while playing. There may be a spot where the small pressure stops the rattling. In that case you've got a place where the glue no longer glues.

[B-string]

You may have "cone sag". Unscrew the speaker and rotate it 180 defrees in the cab.

[Flatbass]

Thanks for the replies.

Rune: the connectors are not touching the cone. I'll try the probe method tomorrow.

B-string: This is the first time I heard about 'cone sag'. Could you elaborate a bit on it? I can't really find out what it is and how mounting the speaker upside down is supposed to cure it.

Please note that I took the speaker out of the cabinet already. I've played through the unmounted speaker in different ways, including holding it upside down and with the speaker lying on the floor pointing at the roof. There was no change in the rattle.

[B-string]

Cone sag can happen to some speakers from gravity pulling on the cone while it is in mounted in a vert. position. Put a straight edge across the basket (cone up) and carefully measure from several points from straight edge to points where the cone meets the outer surround. Carefully look at the center spider on the underside of the cone as well, all folds should be level. It is also possible the bond (glue) between the magnet and the basket has fractured (this is all if the trouble is not a burnt spot on the voice coil rubbing).

[Jerrold Tiers]

Also a really decent possibility that the "speaker rattle" is actually an air leak..... (Since you hear it, and I don't, you may know better, but...).

Sealing compound dries out, glue cracks, stuff happens.

An air leak can sound EXACTLY like a bad speaker.

You can hunt for them with a lighter (the old, bad, way) or with a strip of tissue paper. TP works fine.

As for the rattle even when out of the cab.... air leaks can be in the speaker too...... often the dust cap. With the speaker out the dust cap can still do it, but the surround, not so likely.

The flame or TP doesn't work as well with cone leaks.

As for speaker problems, sag, yeah..... but that is usually more of a "rub" problem.

Loose dust cap is good.

if the noise is ONLY after playing for a while, the voice coil may have slid on the former.... and a couple turns may be loose... they will rattle. often they only do that after the varnish/glue has warmed up.... when cold it may be just sticky enough.

Voice coil problems are invisible without destroying the cone, and they are unfixable in general, for that reason, and others.

[JimmyM]

It sounds like a miracle it lasted that long. Holy moley! Well I hope you find it's just an air leak, but don't be surprised if it's your speaker. You could probably find a suitable replacement at a decent price, though.

[Flatbass]

Thanks for the replies!

I've used and stored the cab in different orientations. Mostly on either one of its two sides. My guess is that rotating the speaker 180 degrees has the same effect as putting the cabinet on its other side and won't help much.

Rune: Touching the speaker anywhere doesn't stop the rattle.

B-string: How can I check if the bond between the voice coil and basket has become fractured? If this is the case, is there a solution for it?

JT: Great suggestions! I found a really small air leak in between the cone and the dust cap. I sealed it with a little bit of glue, but it didn't change anything. I then added more glue all around the dust cap, making sure it's completely sealed, but the problem remains.
The speaker will rattle right from the first note. The rattle doesn't change with time.

If you want to hear what the speaker sounds like. Well... here a link: Hartke B90 Rattle by user6247308 on SoundCloud - Create, record and share your sounds for free
The rattle is more present with low notes, so I used a flatwound strung bass, boosted lows and cut highs and mids. The recorder is a Zoom H2. It captures the rattle quite realistically


I'm not planning on replacing the speaker. Keep in mind that it was originally a 'beginners' combo and it didn't sound that great either. However, surprisingly it has seen a lot of use over the last couple of years on my double bass gigs where my GK 1x12 combo would be too small and my 4x10 cab too big.

[johnk_10]

it's kinda hard to hear in that clip, but it sounds like a cabinet air leak to me. a voicecoil rub usually has a higher pitched 'buzzing' sound to it on every note and at any level.

[B-string]

Originally Posted by Flatbass

Thanks for the replies!

I've used and stored the cab in different orientations. Mostly on either one of its two sides. My guess is that rotating the speaker 180 degrees has the same effect as putting the cabinet on its other side and won't help much.

Rune: Touching the speaker anywhere doesn't stop the rattle.

B-string: How can I check if the bond between the voice coil and basket has become fractured? If this is the case, is there a solution for it?
JT: Great suggestions! I found a really small air leak in between the cone and the dust cap. I sealed it with a little bit of glue, but it didn't change anything. I then added more glue all around the dust cap, making sure it's completely sealed, but the problem remains.
The speaker will rattle right from the first note. The rattle doesn't change with time.

If you want to hear what the speaker sounds like. Well... here a link: Hartke B90 Rattle by user6247308 on SoundCloud - Create, record and share your sounds for free
The rattle is more present with low notes, so I used a flatwound strung bass, boosted lows and cut highs and mids. The recorder is a Zoom H2. It captures the rattle quite realistically


I'm not planning on replacing the speaker. Keep in mind that it was originally a 'beginners' combo and it didn't sound that great either. However, surprisingly it has seen a lot of use over the last couple of years on my double bass gigs where my GK 1x12 combo would be too small and my 4x10 cab too big.

Solution: New cone. The bond I spoke of was between the magnet structure and basket. Solution new speaker.
That sounds a lot like dust in the voice coil gap. If there is a vent on the center back of the speaker a gentile vacuuming may do the duty.

[Flatbass]

I forgot to mention that the clip was recorded with the speaker unmounted. It was lying on the floor pointing towards the ceiling.

I know it's kind of hard to hear, but the recording captures the actual sound of the speaker quite well. I'm listening to it on studio monitors, though. I could make a new mp3 with less low end if anyone would like to hear that.

There is a small round vent on the back of the speaker with a little grill protecting it. I'll try cleaning it and see what that does.
Reconing or replacing the speaker is not really an option, although I did send an email to Hartke about a replacement. Maybe, if I can find a cheap replacement speaker, I'll consider it.

I've also noticed that the rattling seems to be more present on one particular area on the side of the cone. Yet, I can't see anything wrong with it and I've stared at it forever
It could be that the problem is somewhere deeper inside the speaker, but the rattle manifests itself on the side of the cone.

[B-string]

Originally Posted by Flatbass

I forgot to mention that the clip was recorded with the speaker unmounted. It was lying on the floor pointing towards the ceiling.

I know it's kind of hard to hear, but the recording captures the actual sound of the speaker quite well. I'm listening to it on studio monitors, though. I could make a new mp3 with less low end if anyone would like to hear that.

There is a small round vent on the back of the speaker with a little grill protecting it. I'll try cleaning it and see what that does.
Reconing or replacing the speaker is not really an option, although I did send an email to Hartke about a replacement. Maybe, if I can find a cheap replacement speaker, I'll consider it.

I've also noticed that the rattling seems to be more present on one particular area on the side of the cone. Yet, I can't see anything wrong with it and I've stared at it forever
It could be that the problem is somewhere deeper inside the speaker, but the rattle manifests itself on the side of the cone.

That could be a leak or damaged bond between cone and suspension? Maybe try regular household rubber cement, two thin coats around the outer suspension.

[johnk_10]

or it could be where the spider is glued to the basket. i've had that happen a couple of times.