Prestigious Two – Mini Monitor

Concept:

 

Prestigious Two – Mini Monitor is a small sized 2-way stand-mount bass-reflex loudspeaker. It’s ideal for small to medium sized listening room. The tweeter can be fine-tuned to several different levels according to personal preferences and taste. This loudspeaker design is the less expensive cousin to the Excellence Two – Mini Monitor loudspeaker.

Loudspeaker driver units:

Prestigious Two – Mini Monitor uses driver units from SEAS and Dayton Audio. The SEAS L12RCY/P is a 4.5” mid-woofer from SEAS affordable “Prestige” Series. For its size it has a nice low-frequency extension and the aluminium cone act as a piston within its usable frequency range.

The Dayton Audio RS28F-4 has an effortless neutral sound character with a nice top-end finish without ever sounding exaggerated or harsh. The two drivers blend very nicely with each other.

For further details see:

L12RCY/P

RS28F-4

Cabinet:

 

Prestigious Two – Mini Monitor uses an 8 liter “Dayton Audio” enclosure. This is a very nicely built curved cabinet with a 25mm (1″) MDF front-baffle. The enclosure walls are made of 18mm MDF as well as a 15mm brace from the bottom to the top.

The internal volume needs to be reduced with something solid by approximately 3 liters. This gives an enclosure net volume of around 5 liters (enclosure volume – drivers, filter and port). It’s ok to reduce the depth of the enclosure if the pre-fabricated Dayton enclosure is not used, in order to achieve the 5 liter net volume and as long as the baffle dimension and lay-out is kept.

The enclosure should be tilted backwards about 5deg. An alternative when building enclosures from scratch would be to build the box with a 5deg slanted baffle.

Cabinet drawing: Dayton 8 liters Curved Cabinet #302-701

The internal cabinet walls are taped with strings of bitumen pads to reduce resonances. The enclosure is lightly filled with sheep wool. All drivers are flush mount and in order to let the mid-woofer “breathe” properly, don’t forget to chamfer the baffle for the mid-woofer.

 

Baffle drawing and driver unit layout:                                                              Chamfered baffle:

 

 

 

 

 

 

 

Box simulation:

 

5 liter bass-reflex box with port tuned to 55Hz (anechoic response)

-3db = 55Hz

-6db = 49Hz

-12db = 42Hz

The enclosure is a bit oversized and uses the concept of “Extended Bass Shelf” (EBS) alignment, which helps to extend the lower frequencies at the cost of some decrease mid-bass. When room-gain is added to an EBS tuned loudspeaker you get a nicely extended bass from a small loudspeaker as in this design.

The mid-woofer has for its size a respectable woofer capability and goes down to the high 40:ies when the room gain is added. However, due to its physical size the max output is somewhat limited. Don’t expect the same max output as a 6.5-7” woofer.

 

Cross-over design:

 

 

The cross-over is very simple and consist of a first-order electrical filter for the mid-woofer together with a notch filter (C1+L2) for the cone break-up. A second-order electrical filter is used for the tweeter together with a response shaping filter (C3+R2) to reduce the tweeters rising top-end frequency response.

The cross-over filter is optimized for the 15deg off-axis frequency response and with a 5deg backwards tilt of the enclosure.

The cross-over is asymmetrical with an acoustical second-order slope for the mid-woofer and a third-order slope for the tweeter. Together with the relative acoustical driver off-set this asymmetrical filter and a 5deg backwards tilt of the enclosure gives an optimal phase behavior between the driver units for the system.

Attention! The tweeter should be connected with reverse polarity.

 

Tweeter level option:

The tweeter level can easily be changed +/- 2db by swapping one single resistor (R1).

 

 

 +2dB

R1 = 2.7 Ohm

 

 

 

 

 

 

 

 

 

 

 

+1dB

R1 = 3.3 Ohm

 

 

 

 

 

 

 

 

 

 

 

0dB Reference level

(max linearity)

R1 = 3.9 Ohm

 

 

 

 

 

 

 

 

 

 

 -1dB

R1 = 4.7 Ohm

 

 

 

 

 

 

 

 

 

 

 

 -2dB

R1 = 5.6 Ohm

 

 

 

 

 

 

 

 

 

 

 

I personally like the -1dB or -2dB setting the most as it gives the best tonal balance. I strongly recommend testing different resistor values to tune in personal taste and conformity with the used stereo equipment and music genre. If you have a very dark sounding equipment you might want to test the 0dB or +1dB setting.

Impedance measurements:

 

 

Green = Left loudspeaker

Blue = Right loudspeaker

The impedance never falls below 6 Ohm in lower frequencies. Depending on the used tweeter attenuation the impedance varies between 5-8 ohms in the upper frequencies. The loudspeaker is amplifier friendly, but due to the loudspeakers low sensitivity (83dB @ 1m/2.83v) an amplifier capable of >50W is recommended.

Frequency measurements:

 

If nothing else is noted in the comments, the following frequency measurements of the finished loudspeaker are made at a 2m distance at tweeter height and for the 0db tweeter reference level.

All frequency response charts are presented in a 50db scale with 1/24 octave smoothing and the measurements are valid down to 350Hz.

Frequency response 15deg off-axis, reference tweeter level  (80db) scale:

Blue = Left loudspeaker

Red = Right loudspeaker

There is almost a perfect frequency match between the left and right loudspeaker. The right loudspeaker has a slightly higher top-end response, but nothing that’s audible in real life.

System frequency response 15deg off-axis, reference tweeter level:

The mid-woofer cone break-up at 9kHz is effectively suppressed 30dB thanks to the notch filter. The knee between 4.5-6kHz is reduced with an increasing off-axis angle. The tweeter falls off rapidly over 20kHz. The baffle step compensation for this loudspeaker is about 4-5dB.

System frequency response 15deg off-axis, reference tweeter level:

As expected with a second-order filter, connecting the tweeter with the same polarity as the mid-woofer shows a broad dip in the frequency measurement. Attention! The tweeter should normally be connected in reverse polarity in order to function properly.

System frequency response 15deg off-axis, reference tweeter level:

Blue = Without front grill attached

Red = With front grill attached

I would recommend listening to this loudspeaker without the front grills attached.

System frequency response (0dB) reference tweeter level:

Blue = On-axis

Red = 15deg off-axis

Green = 22.5deg off-axis

System frequency response (0dB) reference tweeter level:

Blue = 30deg off-axis

Red = 45deg off-axis

Green = 60deg off-axis

Distortion measurements:

 

Measurement setup:

  • Tweeter-axis near-field measurement at 18cm
  • Frequency Range: 200-10000Hz

The distortion measurements are done in near-field and the amplifier output level was adjusted for the loudspeaker so that the fundamental is 85dB at 1m and 90dB at 1m. This setting simulates normal to medium-high listening levels.

85dB at 1m

90dB at 1m

As expected there is a bit higher distortion for the mid-woofer than the Excellence Two – Mini Monitor, but still good. The odd-order distortion is held back by an effective notch-filter.

Component list:

 

 

At 580 US$ a pair this “Mini Monitor” isn’t exactly super cheap, but the cost can be reduced by choosing less expensive cross-over components and by building your own enclosures.

However, I strongly advice to use the suggested cross-over component quality because it gives a very noticeable sound quality boost together with these two very fine loudspeaker drivers.

Summary:

 

Sound description:

Since the Prestigious Two – Mini Monitor is virtually the same design as the Excellence Two – Mini Monitor the sonic similarities is striking. You could say that it has 75% of the Excellence Two – Mini Monitor qualities and if you disregard the bass performance they are very close in sound quality. In this case, it’s a matter of taste and personal preferences.

Compared to its cousin the Excellence Two – Mini Monitor the bass hasn’t the same weight and depth and it has less low mid-range punch, but he bass is well defined and effortless in its character. However, the law of physics still applies and the small size has its limitations, but with a powerful amplifier you can play respectably strong before it loses control.

The midrange is clean, neutral and is a bit warmer in its character than the Excellence Two – Mini Monitor.

The tweeter is well extended and neutral in its character.  It never sounds harsh or tries to draw your attention from the music. The tweeter works in harmony with the neutral clean character of the mid-woofer and they are a perfect match to each other.

The loudspeaker is a bit forward sounding with pin point imaging and they have a generous sound stage with a nice width and height and to some extent, depth. The 3D dimensionality is actually a tiny bit better than the Excellence Two – Mini Monitor.

When you close your eyes and listen you can easily hear the location of the individual instruments and musicians in the recording.

With a well-made recording you are rewarded with a huge crisp soundstage. Less good recordings are still enjoyable, since the loudspeaker is forgiving and non-analytic in its character.

 

Recommended loudspeaker placement:

  • No or little toe-in.
  • >0.5 meters from back wall.
  • 2 meters apart.
  • 2.5 meters listening distance

 

The loudspeaker is optimized for a listening distance of 2.5m, but everything between 2-3.5m works fine. As always it pays off to test different loudspeaker placements and see what fits the room and personal preferences the best.

Technical specification:

 

Prestigious Two – Mini Monitor
Type: Two-way small sized stand-mount loudspeaker
Enclosure type: EBS tuned bass-reflex
Woofer driver unit: 4,5” Aluminium cone. SEAS L12RCY/P
Tweeter driver unit: 1-1/8” Soft dome. Dayton RS28F-4
Cross-over frequency: 2100Hz.
Cross-over function: Asymmetrical LR second-order acoustically, first-order electrically (wo) and second-order electrically (tw)
Frequency response: 55-20000Hz
Sensitivity: 83db 1m/2.83v
Nominal impedance: 8 Ohms
Minimum impedance: 6 Ohms
Enclosure volume: 5 liter internal net volume
Weight: 9kg
Enclosure dimensions (height x width x depth): 30.48×19.05×26.75cm (12″x7.5″x10.5″)

 

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Thank you!

/Göran

Author of the “AudioExcite Loudspeaker Design” website