Midnite Magic

Midnite Magic

Midnite Magic

Project Category:
Bookshelf Speakers

Project Level:

Project Time:
8-20 Hours

Project Cost:
$100 – $500

Project Description:
2way ported bookshelf speaker system

Design Goals:
To use the Dayton AMT2-4 as I had never used one before. To make a versatile bookshelf that would work well for movies, TV, and music. To be able to be used with or without a subwoofer.

Driver Selection:
Dayton AMT 2-4 tweeter (275-092) Is a very smooth and easy to work with unit. The off-axis response is very good
Faital Pro 5FE120 woofer (294-1141) is a gem, really. It is linear throughout its operating range and exhibits little cone breakup.

Enclosure Design:
I used the Denovo knockdown .23 cu ft cabinet (300-7062)
The cabinet is ported on the rear using 1.5″ pvc, 5.5″ long. For an Fb of 55Hz. F3/6/10 is 51/45/40

The drivers are centered left to right. The tweeter center is 3.25″ from the top edge (before the oak top was added). The woofer is 7.562″ from the top.

Enclosure Assembly:
The cabinets are CNC cut and even include a roundover on the baffle. There was very little sanding needed. I did use a brad nailer in the corners to hold the pieces steady as I applied the clamps. With the accuracy and fit, I was able to assemble both cabinets in about 20 minutes time.

I added corner blocks of 3/4″ BB ply to hold t-nuts for a removable baffle.

The walls are lined with 1/2″ sonic barrier and there is a handful of loose fiber fill behind the woofer.

The baffle and rear are coated in duratex. The sides in paper-backed oak veneer and the top with 1/4″ oak.

Crossover Design:
I used more parts than I normally do but not anything difficult either. The woofer is a damped 3rd order, the tweeter 4th order, both electrically. This resulted in a 4th order LR alignment at the crossover point of 3.5KHz. A single 8ohm resistor was used ahead of the tweeter circuit for level matching. I did use a 20w unit here for extra heat protection, if it was warranted or not, I’m not sure but it is cheap insurance.

Tips & Tricks:
Use a brad nailer for temporarily holding the pieces together as you apply clamps.

In testing, I used a 30uF cap in series with the tweeter for protection.

These were a really fun, fast project. Using the manufacturers provided data, I was able to make a very close sim. After taking the measurements and playing around for a few days in PCD, I was able to put together the crossover. They have a very smooth response on and off-axis and handle power very well to way to loud levels. For testing I use an Adcom GFA-555 amp and had no problems driving past the halfway point on my preamp.

These now reside in my living room awaiting a matching sub for movies or when I want to play them way to loud!

About the Designer:
I am a member of the Parts Express speaker design team

Project Parts List:

ERSE 2.5mH 18 AWG I Core Inductor Crossover Coil
ERSE 0.20mH 18 AWG Perfect Layer Inductor Crossover Coil
Jantzen Audio 0.15mH 20 AWG Air Core Inductor Crossover Coil
Jantzen Audio 0.10mH 20 AWG Air Core Inductor Crossover Coil
Audyn Cap Q4 15uF 400V MKP Metalized Polypropylene Foil Crossover Capacitor
Audyn Cap Q4 6.8uF 400V MKP Metalized Polypropylene Foil Crossover Capacitor
1 Ohm 10W Resistor Wire Wound 5% Tolerance
8 Ohm 20W Resistor Wire Wound
Sonic Barrier 1/2″ Acoustic Sound Damping Foam with PSA 18″ x 24″
Round Speaker Terminal Cup 2-15/16″ Satin Nickel Banana Binding Post
Parts Express Cast Frame #8-32 Speaker Mounting Kit
M3.5 x 25mm Cap Head Wood Screws Black 100 Pcs.
M4 x 35mm Cap Head Wood Screws Black 100 Pcs.

1 comment

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  1. 1
    Chuck Morris

    On the BOM, there are 2 inductors listed for the woofer. I used a 2.5 mh and unwound it to the required 2.2mh size. The Jantzen pcore is a suitable replacement if unwinding the 2.5 is an issue.

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