[stegeoc]

I suppose everyone may do it a little different. However, the SPL curve, for example, is useful in a theoretical sense. it shows the full capability of the unit from a tested and verified source. Once the driver(s) are in circuit, they will all behave differently. This is where driver selection becomes imperative. You have to first establish what your goal for the soundstage will be. Flat eq, v eq, boosted highs, boosted lows, etc. Now we have a target. I start by wiring every driver into their circuit with one set 3x2 tube @10mm in length. I then run spl tests, 8 repetition, with each driver(s) in circuit. Now you can determine if your goal is achievable with the chosen drivers. Many times, ive established a circuit, tested it, and said, “not impossible or improbable, just gonna be way harder than it shoudl be.” Dampers flatten out unwanted peaks, resistors cut some high bite and volume but will push a resonant peak up the spectrum, l-pads lower volume and flatten the resonant peak, series capacitors cut the lows. Personally, Im extremely mindful of the values for capacitors. If they get too big in value AND the driver is pulling major juice, electrical and acoustic phase can get effected. Also to note, acoustic phase almost always, in my experience, is best detected by the human ear.

Wow, thanks for the thorough explanation. Lots to think about! I've ordered a microphone that I can use to make spl graphs, so once I have that I can start exploring all these areas more. Cheers!

 

[tomekk]

With universals, biocompatibility is not essential as the shell will never come in contact with your internal skin. For customs, its a must.

Off topic

If you have sensitive skin, just working with uv resins and uv varnish and isopropanol is a constant battle with skin eczema. If you are sensitive of course.
It's not that these products are safe for everyone, they are safe for the unsusceptible, sensitive people to skin diseases (30% population) are crushed by uv products such as varnishes and resins (in production mostly).

 

[Wgibson]

There is a recording trick to use two slightly different microphones at the same time, similar principle with different drivers playing the same thing. Its not reverb, not echo, you can barely hear it but I think it adds some depth/presence, a little better soundstage and more natural sound. Take it with a grain of salt because this is something you hear more than you see in measurements, so its an opinion not a fact.

Edit: related question, opinions on crossing drivers directly at the pinna peak? Should you try to overlap more, or is this generally not a problem if the frequency response is good?

 

[swtnate]

There is a recording trick to use two slightly different microphones at the same time, similar principle with different drivers playing the same thing. Its not reverb, not echo, you can barely hear it but I think it adds some depth/presence, a little better soundstage and more natural sound. Take it with a grain of salt because this is something you hear more than you see in measurements, so its an opinion not a fact.

Edit: related question, opinions on crossing drivers directly at the pinna peak? Should you try to overlap more, or is this generally not a problem if the frequency response is good?

When I first began, I didn't have a test rig. All I had was this forum and my ears to guide me. So, I established builds completely tuned by ear using traditional configurations. Once I had 3 solid configurations, I then ponied up for the test microphone. That's when I tested all 3 configurations. I knew how they all sounded. With the SPL graphs, I had a visual representation of what I heard and what I thought was good. I also use the equalizer window in iTunes to pull up and down certain frequencies to better understand where a build might be giving me some muddiness. Lastly, I use the IFI attachment for impedance compensation. That attachment gives me standardization between all drivers.

 

[swtnate]

@mattmatt @Wgibson Here's a triple driver SPL. I used a 29689 and 33AJ007i/9.

 

[mattmatt]

@mattmatt @Wgibson Here's a triple driver SPL. I used a 29689 and 33AJ007i/9.

Looks awesome! I have something similar but tuned differently.

 

[swtnate]

Any one have a preferred method for applying lacquer / shellac to the inside of the shell that allows the coating to fully cure out? No matter what product i use (Egger, Lack3, NanoScreen, L-1, detax, etc) the inside doesnt cure out in the same way as the outside. Ive even tried it in a nitrogen environment and submerged in glycerine. i even bought the Thermosoft curing agent, OxyStop, to see if that would help… nada. If I could coat the inside of the shell the waxed impression wouldnt have to be SOOO perfect…..

 

[stegeoc]

When I first began, I didn't have a test rig. All I had was this forum and my ears to guide me. So, I established builds completely tuned by ear using traditional configurations. Once I had 3 solid configurations, I then ponied up for the test microphone. That's when I tested all 3 configurations. I knew how they all sounded. With the SPL graphs, I had a visual representation of what I heard and what I thought was good. I also use the equalizer window in iTunes to pull up and down certain frequencies to better understand where a build might be giving me some muddiness. Lastly, I use the IFI attachment for impedance compensation. That attachment gives me standardization between all drivers.

When you measure SPL of drivers directly, without them being in a shell, do you just stick the standard 1cm tube into your mic coupler and seal with some putty or something?
When you compare this measurement to the same circuit once it has been added to a proper shell and sealed up, what sort of differences do you normally see in the SPL graphs? Presumably there is some difference, given that most BAs have some sort of vent?

 

[mattmatt]

When you measure SPL of drivers directly, without them being in a shell, do you just stick the standard 1cm tube into your mic coupler and seal with some putty or something?
When you compare this measurement to the same circuit once it has been added to a proper shell and sealed up, what sort of differences do you normally see in the SPL graphs? Presumably there is some difference, given that most BAs have some sort of vent?

I measure with a 0.4cc coupler when directly measuring BA raw FR, that's just for me knowing how it performs compared to other iems. Testing tuning shouldn't be done without your planned tubing/crossover. Peak shifts happen when tubing is installed. Damper position also affects its efficiency. Also. Most BAs actually don't have a vent. IIRC, testing the 38 series, having it in a sealed shell and open shell has negligible difference. Can be wrong tho.

 

[Aldo40]

Any one have a preferred method for applying lacquer / shellac to the inside of the shell that allows the coating to fully cure out? No matter what product i use (Egger, Lack3, NanoScreen, L-1, detax, etc) the inside doesnt cure out in the same way as the outside. Ive even tried it in a nitrogen environment and submerged in glycerine. i even bought the Thermosoft curing agent, OxyStop, to see if that would help… nada. If I could coat the inside of the shell the waxed impression wouldnt have to be SOOO perfect…..

I completely dip the empty shell in the lake3 or shellac, I drain it and I turn a few minutes without UV and then I turn 5 minutes minium in UV

 

[Aldo40]

When you measure SPL of drivers directly, without them being in a shell, do you just stick the standard 1cm tube into your mic coupler and seal with some putty or something?
When you compare this measurement to the same circuit once it has been added to a proper shell and sealed up, what sort of differences do you normally see in the SPL graphs? Presumably there is some difference, given that most BAs have some sort of vent?

Me I reproduced a piece in 3D printing that looks like a nozzle or I plug my drivers on it, it gives me curves close to the final, I can change the damper.
well obviously we can refine the filtering once all the drivers in place in the final shell

 

[Aldo40]

I have quickly made you a model that can serve you.
we can go up to 4 tubes, if you do a 3 tube configuration and well plugged the 4th with blutack.
the holes are made for 2mm tubes with damper at the end of the tube.
There is a 2.05mm hole for fixing a 1mmID tube for bass for example.
there are two 3.10mm holes for 1.5mm ID tube
there is a hole of 3.10mm for tube of 2.00 mm ID for EST
I put a 2 pin connector holder.
renamed the TXT file to STL

 

[tomekk]

RAU-34832-B148 Balanced Armature Supertweeter

Knowles has advanced the state-of-the for in-ear acoustics with the release of its “supertweeter”. This new balanced armature offers much improved output with the ability to reach an ultra-high frequency of 40kHz, making it ideal for in-ear monitors (IEMs) and true wireless stereo (TWS) earphones.

https://seltech-international.com/wp-content/uploads/2022/05/receiver-datasheet-rau-34832-b148-1.pdf

 

[stegeoc]

I have quickly made you a model that can serve you.
we can go up to 4 tubes, if you do a 3 tube configuration and well plugged the 4th with blutack.
the holes are made for 2mm tubes with damper at the end of the tube.
There is a 2.05mm hole for fixing a 1mmID tube for bass for example.
there are two 3.10mm holes for 1.5mm ID tube
there is a hole of 3.10mm for tube of 2.00 mm ID for EST
I put a 2 pin connector holder.
renamed the TXT file to STL

This looks great. Don't have a 3D printer, but I guess it should be possible to knock something similar out of some resin. Worth a think..

 

[Yuudelvin]

Here ya go my man.

How exactly is this done, I'm curious