Double Bass An Ehrlund blog, sort of

[DB Slidefunk]

I've found that the the gap between the EAP and bass makes a big difference. I used it squashed really close for a while. Lots of low end and a pleasing tone but the high notes just aren't there. Getting a bigger gap really opened the sound. I'm also blending with the lifeline for loud gigs and getting a very usable sound. On the weekend we played a loud gig on a huge hollow stage with 4 sub traps underneath and no feedback issues. It's not the best sound but I'm certainly happy enough with it.

 

[Ric Vice]

I've found that the the gap between the EAP and bass makes a big difference. I used it squashed really close for a while. Lots of low end and a pleasing tone but the high notes just aren't there. Getting a bigger gap really opened the sound. I'm also blending with the lifeline for loud gigs and getting a very usable sound. On the weekend we played a loud gig on a huge hollow stage with 4 sub traps underneath and no feedback issues. It's not the best sound but I'm certainly happy enough with it.

+1 I hadn't really thought about that, but mine sits on three tiny balls of putty at each corner, and there is definitely a gap between the pickup's surface, and the table. It's counterintuitive to the way most piezo's mount. Most piezo's are wedged into tight spaces.

Ric

 

[drurb]

As is typical with the EAP, it depends on the bass and personal preferences. As of now, the preferred sound for me is with a minimal amount of putty such that the gap between the EAP and the table is <0.5 mm. YMMV.

 

[engedi1]

IME, the bowed volume was very similar to pizz. That is one of the things I loved about this pickup. It is so touchy with placement, that if you move it over an half inch in any direction I bet you can find the sweet spot where some of that midrange dies out and the arco volume is more balanced. And then the putty like the other guys are talking about.

 

[Vertigo Jones]

I find that a minimum gap between the table and the pickup works for me. Mine is probably about half a millimeter. I also had to adjust the gain as the Ehrlund isn't wasn't as hot as the FC.

 

[Ric Vice]

I find that a minimum gap between the table and the pickup works for me. Mine is probably about half a millimeter. I also had to adjust the gain as the Ehrlund isn't wasn't as hot as the FC.

+1 Same experience here, but the difference in tone quality, more than makes up for the volume difference. The Ehrlund's timbre blends with other instruments, where the FC or Realist are more "in your face". Just my take.

 

[Vertigo Jones]

+1 Same experience here, but the difference in tone quality, more than makes up for the volume difference. The Ehrlund's timber blends with other instruments, where the FC or Realist are more "in your face". Just my take.

My findings as well. I don't miss the piezo zing at all. I'll gladly trade a little less volume and pointedness for a more natural tone. That said, I struggled hard to get anything near a good sound with it on my ply bass. The FC definitely works better for that bass. The EAP works a treat on my carved. Personally I really like the preamp too. I tried going direct into my AI Focus III and it was passable, but the preamp really made the difference to my ears. My only problem is I found a spot that I really like and shudder at the thought of having to remove the EAP for any reason. It's almost impossible to get the same sound again once you move it.

 

[Ric Vice]

My findings as well. I don't miss the piezo zing at all. I'll gladly trade a little less volume and pointedness for a more natural tone.

+1 on both of my carved basses the EAP works beautifully, it's so nice to have a transducer that works with either pizz or arco

That said, I struggled hard to get anything near a good sound with it on my ply bass. The FC definitely works better for that bass.

Actually, that doesn't surprise me. Realists don't work all that well on a ply bass either, because of their multi-laminate table.

The EAP works a treat on my carved. Personally I really like the preamp too. I tried going direct into my AI Focus III and it was passable, but the preamp really made the difference to my ears.

My only problem is I found a spot that I really like and shudder at the thought of having to remove the EAP for any reason. It's almost impossible to get the same sound again once you move it.

I worried about that to, but when I had to have my Mirecourt repaired, the pickup had to come off and I found the sweet spot without to much trouble, but I don't take it on and off the bass.

 

[drurb]

My solution for re-placing the EAP is to surround it with blue painter's tape before removing it. The painter's tape is quite helpful when you're trying to find the sweet spot because you can evaluate new positions and then return it rather precisely to previous ones.

 

[Mark Gollihur]

My solution for re-placing the EAP is to surround it with blue painter's tape ...

So, wait - your earlier suggestion of drawing a big "X" with a Sharpie wasn't serious?

 

[drurb]

So, wait - your earlier suggestion of drawing a big "X" with a Sharpie wasn't serious?

The problem with the Sharpie idea was that you have to remove the EAP before drawing the "X" to make sure you get the "X" in the right spot. That was the only drawback... other than the "X"s all over the bass. So, next, I tried removing the endpin and scratching a mark on the top. That worked well... except for all those nasty marks. At your suggestion, I purchased seven more EAPs (Thanks for the shipping discount!) and covered all the marks with them. Now I can connect any number of the eight EAPs through a mixer and get all sorts of different tonal palettes.

 

[SVT4001]

What about stacking them? If an Ehrlund picks up the sound of your bass, wouldn't the sound of an Ehrlund picking up the sound of an Ehrlund picking up the sound of your bass be twice as good? Or maybe the effect would be EXPONENTIAL?!!!

 

[DB Slidefunk]

Strangely when I was adjusting my Ehrlund the other day, I noticed that the weight of my finger pressing on it increased the volume significantly. There may be something in it DC Bass. I may hire an apprentice bass understudy to crouch down and press on it during performances from now on.

 

[Vertigo Jones]

Strangely when I was adjusting my Ehrlund the other day, I noticed that the weight of my finger pressing on it increased the volume significantly. There may be something in it DC Bass. I may hire an apprentice bass understudy to crouch down and press on it during performances from now on.

For me, the EAP definitely gets louder the closer it gets to the table. The amount of putty used makes a big difference in that regard. When I had the EAP sitting higher, I got a more diffuse sound. Almost like a distant mic kind of tone. Placing it closer to the table increased the gain and gave it a more direct sound. The effect is comparable to what happens when you turn the FC adjuster a few degrees.

+1 on the painter's tape idea. I finally wised up and got some masking tape after racking my brain figuring out how to mark a spot that I liked. I ended up putting tape at the sides of the EAP making a triangle shape. If I wanted to go back, I just placed the EAP back in the center and removed the tape. No fuss, no muss. Still -it never sounds exactly the same to me.

 

[DB Slidefunk]

Yeah, I'm still experimenting with the putty and gap.

 

[DoubleMIDI]

Due to the patent I read, the Ehrlund EAP is a contact microphone based on a triangular piezo film membrane.
In a contact microphone there is a weight on the membrane which, due to inertia, hardly moves but the rest of the EAP moves with the top of the bass and so the piezo film is bent.
The thicker the putty between top and EAP the more damping happens from top to EAP, so the sound is quieter and less direct. To a certain amount this might sound nicer, but it's not the true movement of the top at the position of the EAP. But it might help against feedback to have some damping of certain frequencies.

I hope this explains the audible effect of higher or less distance between top and EAP.
The area of putty contact with both, top and EAP might have some influence too and using a harder putty might have a similar effect to a closer distance. So it's not the distance alone that might influence the sound.

 

[drurb]

As I understand the EAP, and I have seen one of Ehrlund's patents, it works much like other contact mics. Specifically, the membrane is held in place at its edges or surround, allowing the central portion to vibrate relative to the edges. I believe the central portion of the membrane vibrates within the casing and is not in contact with it. Increasing the thickness of the putty adds damping and less efficient transmission of the vibrations. Bridge-wing pickups are contact mics as well.

 

[DB Slidefunk]

That would add up with my experience. I put more putty on and increased the gap a little. The sound was rounder and a bit mid rangy. Quite pleasing but a bit indirect compared to when I used a smaller amount of putty and had a smaller gap.

 

[DoubleMIDI]

I wouldn't say bridge wing pickups are contact microphones but rather pressure sensitive transducers. And piezo disks like the Fishman BP-100 bending sensitive transducers. Which doesn't mean that they may work with less efficiency in a different mode of operation, but it's not where the main signal comes from.

The main difference of contact microphones to air pressure sensitive microphones is that the air pressure sensitive microphones membrane is put into vibration by air pressure and the case doesn't vibrate, whereas the contact microphone has a mass on the membrane that does not vibrate due to inertia, but the case vibrates together with the part it is in contact with.

I agree that the membrane could be replaced by a different kind of sensor, but there should be a larger non-moving mass on one part of the sensor and a rigid connection to the case of the contact microphone on the other. I think the bridge wing is a bit less mass for that and also loosely in contact with the case. So in some sense it might look like a contact microphone but I don't think this is the main mode of operation.

 

[drurb]

Actually, if you consult the definition of a contact microphone (e.g., see here and more formally here), you will find that a bridge-wing pickup and virtually all piezo pickups are contact microphones. Your own description of how they operate vis a vis microphones excited by airborne transmission makes that apparent as well. You do, however, seem to be correct that there must be some mechanical contact between the case and the central portion of the membrane. There is nothing I could find that necessitates that the membrane in a contact mic must be in rigid contact with the case and that would seem to be most undesirable. As you point out, that's not true for many bridge-wing pickups, which are contact mics, and I'm not aware that it is true for the EAP either. In fact, if you speak with the designers of such products, you find that the "secret sauce" is the nature of the damping materials that are placed between the case and the membrane. My understanding is that rigid contact between the case and the membrane would produce an awful-sounding transducer. The damping materials are used to tune the response of the device. Basically, the distinctions you made concerning the loading of membranes describe variations in the design and operation of different contact mics. That is, different members of the class of contact microphones, which all of them are. The main mode of operation of a bridge-wing pickup is absolutely as a contact microphone.