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Three identical small sealed speaker boxes built.

Intended as a mid-range unit for use in a 3-way system: Initial target frequency was 200-4 kHz.

Obviously, I built six boxes for three stereo pairs of speakers but let us keep it simple.

 

All three units have the following identical features:

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  • MDF @ ½” thick, painted flat black.

  • Solid core AWG16 copper internal wiring.

  • No internal bracing of any sort.

  • Internal cavity (~4.8 liters) and are sealed.

  • Roughly the same volume of loose fill Roxul SAFE n' SOUND.

  • Measured at a spl of 90 dB at 30cm referenced at 1kHz.

  • No equalization added whatsoever.

  • Cost of drivers approximately $100CAD each

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As seen below:

All three-exhibit similar rising frequency responses due to no baffle step compensation being implemented here, on the equalization to show the "raw" un-equalized measurement.

Equalization would make any of the three, flat as a ruler, within their pass band.

The first speaker below is one that I really liked.

The Eton 3-400 

Pros:

  • Metal cone operating as a piston in the normal operating range (the only one of the three doing so)

  • Great from 400-3500 Hz range.

  • Relatively efficient for a 3" size. 

Cons:

  • Discontinued product

  • Big… huge…call it what you want, uncontrolled break up @ ~9 kHz*

  • Break up makes its way back to haunt you with the second harmonic at 4.5 KHz, this limit how high you can effectively use the driver.

  • Limited spl (smaller speaker diameter with limited power handling and small X-Max)

 

*Break up can be tamed with an aggressive notch filter, but lower harmonic content will still haunt you with the 3 kHz and 4.5 kHz mode which remains present and measurable. (somewhat less severe)

Second photo is a speaker that I wanted to try for a while.

Eminence PRO 5W8, with a ceramic magnet.

Pros:

  • More efficient @ 90 dB.

  • While the measurement does not show this, the power compression is half of the other two!

  • Solid cast iron frame inspires confidence

  • Very strong motor relative to cone weight.

  • Able to handle 50 watts

Cons:

  • Cone and/or dust cap break up in the midrange (not operating as a true piston) *

  • Higher harmonic distortion than the Eton.

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* See phase plug mod elsewhere on this website...

Measurement is that of a stock unit with about 20 hours of burn-in with the "stock" cone.

Third photo is an interesting offering from Eton. Eton is a reputed German manufacturer for those who may not know.

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The Eton 4-212 Orchestra (Note:  The Symphony lines has composite cone).

This is the dust cap version (model with a good-looking phase plug is also available for about the same price).

Pros:

  • Nice "high end" look with ribbed cone.

  • Smoothest stock frequency response (less peak and dips).

  • Dust cap is made of soft plastic and does not induce a breakup mode like the 5W8 does.

Cons:

  • Average harmonic distortion (especially at higher frequencies).

  • Ribbed cone seems to do nothing sound wise. 

  • Heavier cone (relative to the other two) makes for slower step response. (seen on time domain measurement)

Below is an overlay of the harmonic distortion and step response.

Putting them on top of each other really helps to put things in perspective.

It is evident that the 3-400 is "king" from 300-4 kHz, thanks to a rigid cone, it exhibit half the distortion in the intended passband.

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Had this test been done at 100 dB spl at 1 meter, the 3-400 advantage would had deteriorated to 400 Hz. (3" running out of steam)

The small 3" does extremely well at low spl, but THD rises quickly at higher SPL and 300 Hz is not the lower useful limit anymore.

However, at moderate listening intensity, the 3-400 is a strong mid-range candidate.

I used it for a while myself as a 400-3800Hz transducer.

As mentioned, these three drivers are about $100 CAD each.

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What about throwing a $400CAD driver of the same category into the mix to see how it fares?

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Below is the Scan Speak Illuminator 12MU8731, temporary in the Eton 4-212 box. (perfect fit, even the mounting screw holes matched)

$300CAD extra buys you a lot more. One would expect that though.

Pros:

  • Very low inductance (class leading in fact)

  • Cone and dust cap made as a single piece! This was nice and unique.

  • Cone is made up of two thinner cones glued together with damping glue between the layers (insert is the unproven marketing claim). This result in a less resonating sandwich cone.

  • Copper shorting ring to reduce distortion at mid frequency, which has been proven to work great time and time again.

  • Titanium voice coil!

  • Able handle 80 watts!

  • Bragging rights. This is the "top of the line" mid-range from Scan Speak...

Cons:

  • Price

  • Still exhibits break up, albeit at very high frequencies the maximum useful frequency would be @ ~3.8 kHz. (confirmed on subjective listening)

  • Average efficiency

  • Bragging rights are pointless.

Below is overlay of the 12mu8731 compared to the 3-400 at 30cm referenced at 90 dB at 1 kHz.

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