Threaded Inserts (Steel) - TONE A/B TEST

Hi Fellow TB'ers,

Just wanted to share my thoughts & results regarding threaded inserts - or more specifically, trying to perceive and capture any tone & sustain changes after installing them. I've seen talk on other internet forums (and some here as well) regarding the use of machine screws & threaded inserts in place of standard wood screws to attach a bolt-on neck to a body. I've seen talk of both tone & sustain change (some would say enhancement) after installing these - and an equal, if not greater amount of talk debunking such claims. Most people stated that it should make no discernible difference, it's all placebo effect, etc. What I haven't seen anywhere is even so much as a single set of A/B recordings after installing threaded inserts. So enough talk, lets check it out:

I recorded a series of some very simplistic before & after audio tracks that I thought might have a pretty good chance of highlighting any tone or resonance/sustain differences in an A/B test (simple, light thumb bouncing on a few notes, a fingerstyle track & a slap style track). I also thought it might serve some purpose to take a couple of screen shots to get a visual A/B on the size & shape of the waveform on these audio tracks (see Post #2).


Before/After Tracks:

Track 1 BEFORE Inserts: <http://www.zshare.net/audio/80920801dabff43f/>
Track 1 AFTER Inserts: <http://www.zshare.net/audio/80920869d4f0b305/>

Track 3 BEFORE Inserts: <http://www.zshare.net/audio/809209148e4b4cc1/>
Track 3 AFTER Inserts: <http://www.zshare.net/audio/8092106616033fc4/>

Track 4 BEFORE Inserts: <http://www.zshare.net/audio/8092111843beaec1/>
Track 4 AFTER Inserts: <http://www.zshare.net/audio/809211543bad4905/>


Same tracks are being hosted HERE as well (Thank You rodneyat) if you are experiencing any difficulties with the first set of links:

Link Removed
Link Removed

Link Removed

Link Removed

Link Removed

Link Removed





After listening to the audio A/B & seeing the visuals of the waveform results, I found some very interesting things:

1. What appears to be a decrease in some amount of low end response, most likely due to absorption into the body of the bass.

2. Liveliness, sustain, responsiveness to playing touch are greatly enhanced.

3. Looking at the average peaks, a slight drop in volume by 1 or 2db, at least in visual A/B comparisons of the waveforms when the tracks were loaded up along side a db scale in my recording software - this slightly lower volume may be related to observations in #1 (slight perceived attenuation of some lows or overall energy).

4. No perceivable, harsh "spike" or specific resonant frequency in the upper mids or top end. A very natural, even, & musical sounding extension of those frequencies. Perhaps extension is not the best term to choose since they were there in the first place, just not transferred as well...lets just say I can hear those frequencies much better now.

Oddly enough, I will say that when plugged in through my bass rig - I felt no lack of volume or want for more low end than usual, despite what I see visually happening in the waveform amplitude. Obviously - it is occurring. However things such as a slight EQ adjustment, raising the pickup height and/or tilt to the bass side of things could compensate for any perceivable volume drop. To me, the extended detail & enhanced responsiveness to touch are outstanding & quite a worthwhile trade off of perhaps some slight low end and/or volume being absorbed by the body - that can be compensated for many ways in the signal chain. I also obviously recognize that some or any of these changes would not be welcome by some folks in the least. I've seen it said in this article that the tremendous clamping force at the neck pocket essentially transforms neck & body into a single piece of wood, in turn imparting a lot of the qualities found in neck through instruments. IME here, I would have to agree with that.

Thanks for taking the time to read through my ramblings here. The before/after tracks are listed below. I hope your playback speakers can accurately reproduce the differences in tone I'm hearing & seeing. Furthermore, I hope it sheds some light on the topic of threaded inserts regarding tonal aspects - which is the focus of this thread. Again, through a bass rig - the differences are BIG and IMO - a much welcome enhancement to my instrument(s) that I've installed these on. I am loving the "alive" tonal qualities these threaded inserts have brought, YMMV of course.



Notes regarding the test:

8-32 steel threaded inserts & (4) 8/-32 machines screws were installed.

Bass tested was an SX 5-string SJB-75 (70's pickup spacing w/Rotosound 66 strings).

The same set of Rotosounds were removed, inserts installed, then put back on the bass. String height over pickups measured & checked before & after installing inserts.

Bone-dry wave forms - no bass amp during recording - plugged straight into M-Audio Firewire Solo, then into PC soundcard (Creative Audigy Soundblaster 2)

No normalizing, volume leveling, compression, EQ, MP3 conversion, etc. applied to the tracks. Tracks were saved in wav file at 48Khz*32-bit*mono format.

Pics for general reference:









Here are a couple of screenshots A/B'ing the same section of waveform from Track 1. As you can see, the meat & potatoes portion (not the attack spikes) of the waveforms are hitting about the -4db marker in the BEFORE shot. Those same notes are hitting a little less loud at about -5, -6db in the AFTER shot.

BEFORE:



AFTER:





Here's a general waveform size comparison holding true on track 4:

rodneyat said:

Cool idea..it takes forever for those clips to download. I gave up after waiting 5 minutes for the 1st one to download. Stringray69, If everyone else is having problems...I can put them up on my own server for you. Just send me a PM and I will send you my email address for the files.

Click to expand...

PM sent.

And apologies to everyone having difficulties with the downloads - I left these in .wav format to retain audio clarity & avoid compression & losses encountered during the mp3 conversion process, but the wav format is much larger size than your typical mp3. Or maybe just too many people trying to hit the same few files on the zshare.net server - things may access more quickly as the thread goes on...

thebisch said:

I only listened to the first test, but based on that, I think I like the sound of the wood screws better!

Click to expand...

And that's the intent of this test - to shed light on what exactly is happening by using these. Interestingly, I had not read a word about perceived low end or volume drop on any other internet forums on the topic. Although in all honesty I noticed neither when plugged into a bass rig - had I not did a "wait a minute" double-take on the waveform sizes, I may not have caught it myself. After seeing all the AFTER tracks come in about 1.5 - 2db lower, I knew something was occurring beyond me perhaps not playing at the same volume the second time around.

What I noticed right off the bat was a very musical sense of clarity to the notes that was definitely not there to such a degree before the inserts - much the same way you get when throwing on a well-overdue new set of strings. Believe me, as a bass player it pains me to report any loss of low end or volume (slight as it may be) but it shouldn't be mistaken as a total neutering of your instrument. Again, had I not noticed it in waveform first, I probably would not have caught onto it. I'm just laying out the physical properties of the changes I saw as best & "scientifically" as I can. In fact, on page 3 of this thread I put up a clip of a Squier jazz bass that had inserts installed in the neck - I doubt anyone would have guessed that just by hearing it.

KJung said:

It would have been interesting to run the test by just taking the neck off and putting it back on with the wood screws (i.e, changing the coupling of the neck and body a touch).
My guess is, that would have resulted in some minor change on the scope also.

Click to expand...

+1

Wish I had thought of that. Now that they're installed though, it's got me wondering if I decided to remove the steel inserts, plug the holes & go back to wood screws...would the results go back to the Before state as well? I'm thinking probably so...the sheer clamping/coupling force is clearly a factor behind these slight changes.

rodneyat said:

Here are the audio files

Link Removed
Link Removed

Will post the rest as I get them.

Click to expand...

Thank You Sir! You are 'da man!

Last set of files headed your way.

Chef said:

removing the inserts and replacing with dowels and re-drilling might be similar to stock, but certainly not the same.
differing wood densities, glue inbetween, etc.
kinda late to undo that

still, great test, and great work, thanks!

Click to expand...

+1

True, in theory it would never be the "same". But to what degree would it go back? Filling & going back to wood screws may prove to be so close to the original state that would it be undetectable by the human ear - maybe even so in visual & recorded waveform. It would be a great test - I may get around to that one out of curiosity (not that I'm disliking the new found tone changes & clarity). I will certainly post that as a follow up if I can get around to doing that - it would take some work & a block of time to get it done, but I think it's worth it to find out.

Rocky McD said:

I like threadded inserts but have reservations on any tone enhancement or change. To me, the amount of transfer from neck to body is related to the pressure of the neck to the neck pocket. If a neck is secured by a screw or an insert the main thing is they should be torqued to the exact same pressure for proper comparison. Yet torque of a screw will be higher than a bolt due to increased friction of the screw.
Also, six attaching screws or bolts should transfer more than four. A tight fit should transfer more than a loose fit. However, I do believe the threaded insert is an improvement. Thanks for sharing your test.
Rocky

Click to expand...

Good point - I can only say that I went hand tight with the machine screws. Without access to a torque wrench, I can't say how tight (exactly) that may be. Not sure how I would have evaluated the Before wood screw tension unless there is a philips-head attachment of some sort that one could use in conjunction with a torque wrench.

Fuzzbass said:

Excellent point.

Don't get me wrong, it's a fascinating test, but I'll add a reservation: for accurate results the bass must be played EXACTLY the same way before and after... the slightest change in technique will invalidate the comparison. Nothing against the OP, it's simply the human factor: I'd have the same reservation if someone like Victor Wooten or Will Lee were performing the test.

Click to expand...

No offense taken at all - the thought had crossed my mind as well. Sure, there will be some note-to-note volume discrepancies occurring within the individual tracks. However, after seeing the same general lower volume pattern happening across all the AFTER waveforms, I had no other conclusion left to draw other than the tighter coupling was accounting for more frequencies, more energy being absorbed into the mass of the body - either that or I fail miserably at playing the same track twice at anywhere near the same volume, lol. Which may be so, but I've never had much of a problem with that in past recording experiences.