Dead Spots

[BOD2]

The following is a summary of the main points raised in various “dead spot” threads here on Basschat previously. Thanks to all contributors and to “ikay” for the thread suggestion.

[u][b]What Is a “Dead Spot” ?[/b][/u]

A “dead spot” is a note on the neck of guitar that does not sound as loudly or as long as other notes on the neck. When that note is played it will sound quieter than others around it.

Dead spots occur on even the best of basses. They happen because all necks are flexible to some degree (even graphite ones). The wood that makes up the neck also has specific frequencies where it will vibrate to greater and lesser degrees in sympathy with the string and this is called 'harmonic resonance'. All materials from glass through to granite have a harmonic resonance. Its also the property that makes microphone diaphragms and drum skins vibrate in sympathy with a loud sound.

Due to the properties of the wood, the neck will also be slightly more flexible at these peaks (which is what allows it to be vibrate in sympathy) and a fretted note at the same frequency will have less sustain due to the subsequent lack of rigidity. Thats what gets you the Dead note..

A scientific article about the nature of dead spots is available at the link below -

[url="http://www.acoustics.org/press/137th/fleischer.html"]http://www.acoustics.org/press/137th/fleischer.html[/url]

Also a video that shows the principles involved –

[url="http://www.wimp.com/rubenstube/"]http://www.wimp.com/rubenstube/[/url]


[u][b]How Do I Know If I Have a Dead Spot ?[/b][/u]

The obvious symptom is a quiet note at a particular location (or fret) on the bass neck. It should occur with or without amplification (i.e. you’ll still hear a difference with the bass unplugged).

You can further determine if the problem is frequency-dependent by down-tuning the bass by a semi-tone or more. This will change the frequencies generated by fretted notes on the bass. If the dead spot disappears when the bass is tuned differently, then it is caused by interaction of frequencies within the neck.

Another simple “test” you can try is to sit down with the bass headstock resting firmly on a table top so that string vibrations are transmitted through the neck to the table. This changes the effective mass, and therefore resonant frequencies, of the neck. If the quieter note disappears when playing with the headstock touching the table top, but reappears when you lift the headstock off table, then you have a dead spot.


[u][b]What Can I Do to Fix a Dead Spot ?[/b][/u]

Anything that changes the resonance of the bass as a whole, and the neck in particular, may affect dead spots but note that any such “fix” may simply move the dead spot from once frequency to another (i.e. from one fret on the neck to another fret)

Typical “fixes” that the user might try can include -

1) Change the strings
2) Change the flexibility of the neck (adjust the truss rod)
3) Check for and fix any poorly seated frets

In addition to this, changing the mass of the headstock can sometimes alter the resonance of the neck and might fix a dead spot. You can test this by simply attaching a DIY metal G-clamp to the headstock. If this works then a more attractive proposition is available in the form of the “Fat Finger” sustain enhancer -

[url="http://www.stringsdirect.co.uk/products/406-fender_fat_finger_sustain_tool_in_chrome"]http://www.stringsdirect.co.uk/products/406-fender_fat_finger_sustain_tool_in_chrome[/url]

Another possible, if slightly more extreme, solution is discussed here -

[url="http://www.bestbassgear.com/ebass/gear/hardware/tuner/treating-your-basses-deadspot.html"]http://www.bestbassgear.com/ebass/gear/hardware/tuner/treating-your-basses-deadspot.html[/url]

Changing the machine heads on your bass will also change the mass of the neck but again this is a rather drastic solution.


[i][b][u]IMPORTANT [/u]- Note that there are no guarantees that any of the above techniques will resolve a particular problem.[/b][/i]

[kurosawa]

The spots may be found using clamps, and "cured" by inlaying tungsten weights into the back of the headstock Article: http://www.talkbass.com/forum/f8/dead-spot-removal-743976/

[fingerz]

Nice topic, I'm sure really useful for a lot of people. Everyone should read this, the headstock advice is really handy.

With the frequencies we play within, dead spots can be a real problem. Low end resonates to a much larger degree than high end does, it's such a pain if you play a nice big 'A', but then the 'Ab' one step down doesn't have any body, or doesn't sustain. It's really noticeable.

I've heard (but never tried), that tapered strings can offer a step in the right direction if you are having resonance problems too. Worth adding my $0.2 !

[7ender]

Sometimes a "dead spot" will disappear when you just place te bass-guitar in a corner of the bathroom ( not under the shower of course ) , just for a time of two days . By placing it in a steamy environment for a short period of time , will recover it, , and you will hear that the sustain of the tone is back again . Sometimes it will be okay for ever , but don't be too disapointed when it comes back again within a couple of weeks/months. Dead spots will mainly occure in bass guitars with rose-wood frett-boards . I've had troubles in the past with bass guitars of several brands/types like : Musicman Stingray , Yamaha BB1100S , Fender Jazz Bass (japan) What I think is , that it maybe has something to do with a not solid attachment of the rose-wood layer on the maple neck , wich consist of different types of wood , with different expansions. For a good repair , you have to bring it to a guitar builder for a frett-board replacement. ( sorry for the bad English , but I'm dutch )

Edited March 18, 2013 by 7ender

[Shonks]

I was in Harlesden once. Now that's a dead spot!

[kurosawa]

Another thing, if you can't find a neck for your body that doesn't have dead spots, it might be the body. Poplar taught me this.