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To readers of the AudioExcite blog, there should be no surprise that I like two-way stand-mount loudspeakers and here is another one and most likely not the last one. 🙂

With the Sequence Two – Monitor we take a step up in both the price, but also in sound quality.

At this price point you should expect good measurements and consistency between the driver units. The chosen drivers for this design fulfills that more than enough.

The response dip centered at 1250Hz for the mid-woofer sure does look nasty, but despite some higher second-order distortion it doesn’t affect the sound quality of the driver and is actually only a beauty spot in the frequency measurements.

There is a very nice consistency between the two mid-woofer samples. They have a very flat frequency response from the mid-range to the upper mid-range 1.5-4kHz. The driver has a very nice off-axis behavior and starts “beaming” as high as 3.3kHz. The rising top-end is easily tamed with a response shaping circuit in the filter design and there is no severe and nasty cone-break-ups that needs to be treated.

This mid-woofer just begs for to be crossed-over high up in the mid-range and the listening test confirms it.

For further details see:
AudioTechnology 15H520613SDK

After using my DEQX system for a while in order to break-in the drivers and to get a feel of the driver units behavior and sound characteristics, I’ve decided to cross-over the drivers at a fairly high frequency, around 3kHz.

One might argue that a tweeter like the ScanSpeak AirCirc driver is over-kill for such a design and why not use a small ¾” tweeter instead, but in this design I want to use a true symmetrical LR2 cross-over slopes.

Using a true LR2 cross-over slopes requires some robust tweeters to handle the shallow frequency response slopes as well as a well-behaved mid-range without frequency anomalies above the cross-over frequency.

The AirCirc tweeter has an extended low-end frequency response and has the distortion numbers to back it up.

The two tweeter samples have almost a perfect consistency between each other. It simply doesn’t get better than this.

The rising top-end above 15kHz is nothing that needs to be corrected for. If it at all can be heard it gives the high frequency a bit more air.

For further details see:
ScanSpeak D3004/660000

I think these two mid-woofer and tweeter drivers complement each other perfectly. 🙂

When using a symmetrical Linkwitz-Riley 2nd order cross-over filter topology, the mid-woofer and the tweeter “acoustic center off-sets” is a very important factor to consider for a successful design.

The acoustic center off-set between the drivers in the Sequence Two – Monitor design is about 26mm, when measured at tweeter-axis and at a 2.5m distance.

There are several solutions to adjust the acoustic center off-sets between the mid-woofer and the tweeter and here’s the most commonly used techniques:

1.    Use an asymmetrical cross-over slope.
2.    Use a stepped baffle.
3.    Use a slanted baffle.
4.    Tilt the enclosure back-wards.
5.    Use a ladder delay network circuit.

Each technique has its pros and cons. The most commonly used “asymmetrical cross-over slope” technique can often cause poor phase tracking around the cross-over point.

Using a “stepped baffle” can cause additional baffle diffraction and using a “slanted baffle” cause added enclosure building complexity.

In my prototype design I will use the option 4 and 5. The “ladder delay network” adds complexity to the filter design, but doesn’t have the same issues in the vertical off-axis response roll-offs as the option to “tilt” the enclosure back-wards.

Listening tests will decide which of the solution 4 and 5 that performance the best. If they are equally good, I will publish both options as a part of the design.

The first (left) prototype mid-woofer cross-over section is very simple and consist of an electrically first-order section (L1) and a response shaping circuit (C1+L2+R1) to achieve a full “baffle step correction” and an acoustical LR2 cross-over slope with a cross-over point at 3000Hz.

The tweeter cross-over section consists of an simple electrically second-order section (C2+L3) and an adjustable tweeter level attenuation (R2) together with a “notch filter” (C3+L4+R3) to flatten out the sharp impedance peak at the resonance frequency of the tweeter.

The tweeter “notch filter” is a must in order to achieve an acoustical LR2 cross-over slope with a cross-over point at 3000Hz and to avoid audible distortion and “ringing” at the tweeters resonance frequency.

The second (right) prototype cross-over filter has the “ladder delay network” (L4+C3 and C4+L5) circuit connected between the cross-over filter and the “notch filter” section.

Observe! In this filter the tweeter isn’t directly connected to ground.

I have published two new driver unit measurements!

These ScanSpeak and AudioTechnology drivers will be used in the upcoming Sequence Two – Monitor design. Currently I’m breaking-in the drivers using my DEQX system and to familiarize myself with the driver unit capabilities.

So far everything is looking good 🙂

Here are the measurements details:
AudioTechnology 15H520613SDK

ScanSpeak D3004/660000

I have now released the design for the Prestigious Two – Mini Monitor and the details can be found at:

Prestigious Two – Mini Monitor

The Prestigious Two – Mini Monitor is the less expensive cousin of the Excellence Two – Mini Monitor. They are virtually the same loudspeaker design, but the Prestigious loudspeaker uses the aluminium cone SEAS L12RCY/P instead of the magnesium cone W12CY001.

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. Which one to choose is more 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.

There are several tweeter level options in order to adjust the tonal balance according to personal taste and HiFi equipment.

/Göran

Author of the “AudioExcite Loudspeaker Design” website

I have now released the design for the Excellence Two – Mini Monitor and the details can be found at:

Excellence Two – Mini Monitor

Soon I will also release the Prestigious Two – Mini Monitor which is the less expensive cousin of the Excellence Two – Mini Monitor. They are virtually the same loudspeaker design, but the Prestigious loudspeaker uses the aluminium cone mid-woofer  L12RCY/P instead of the magnesium cone mid-woofer W12CY001.

Excellence Two – Mini Monitor is a very nice sounding small loudspeaker that can play some serious bass for its size. It has a generous soundstage and sounds clear and detailed, but without sounding analytical.

There are several tweeter level options in order to adjust the tonal balance according to personal taste and HiFi equipment.

/Göran

Author of the “AudioExcite Loudspeaker Design” website

I have released new driver unit measurements on the L12RCY/P used in the “Prestigious Two – Mini Monitor” loudspeaker.

“Prestigious Two – Mini Monitor” is a less expensive alternative to the “Excellence Two – Mini Monitor” design. The SEAS 4.5” mid-woofers used in these two designs are more alike than different from each other.

The L12RCY/P has 1-1.5dB higher sensitivity and the cone break-up occurs at a lower frequency, 9.2kHz instead of 10kHz for the W12CY001. The W12CY001 also has a bit lower distortion profile and a greater bass extension. Besides that they are very similar drivers.

Blue = L12RCY/P
Red= W12CY001

As in real life, loudspeaker building can take a sharp turn and the Excellence Two – Mini Monitor is no exception.

When I listened and tested the loudspeaker with my DEQX in an active setup it sounded fantastic. It worked best when I used a 48dB/octave linear-phase cross-over with a cross-over point between 1750-2000Hz.

With that in mind I started to design and build a first prototype of the cross-over with steep cross-over slopes (4th-order LR, acoustical) and with a cross-over point around 2-2.1kHz.

Everything was looking good, both frequency and distortion measurements, but something was missing…. Yes, the loudspeaker sounded good, but the magic was gone!

I used a “Sledgehammer” Steel Laminate Inductor for the mid-woofer section of the cross-over in order to keep the inductors “DCR” as low as possible. I quickly swapped this inductor to a 12 AWG copper-foil inductor instead (expensive).

The effect surprised me. Now the loudspeaker sounded much better. Some muddiness disappeared and the mid-range clarity was much better, but still no magic! I expected more of these drivers after listened to them in the active setup.

First of all, even though these “Sledgehammer” Steel Laminate Inductors have a good reputation they will never be used as a cross-over part in one of my designs. Perhaps they would work in the woofer section of a 3-way cross-over, but I would never use them in any mid-woofer or mid-range section of a 2 or 3-way system. They have poor sonic performance in my opinion and when using a high resolution driver as the SEAS Excel, they just don’t work in this design.

What to do? Scrap the project……. Of course not! Back to the drawing table and build the v2.0 cross-over.

Ok, a steep passive cross-over for the W12CY001 mid-woofer killed the midrange resolution and even though the cap shunt over the inductor technically worked in reducing the 10kHz cone break-up, it didn’t sound good enough.

This time I simplified the cross-over even further. I used a single inductor together with a LC notch to reduce the cone-break-up at 10kHz. Now the acoustical cross-over slope is a 2nd order LR topology. The mid-woofer section has the same number of cross-over components, but the components connected in series with the signal path are reduced to one. That’s a good thing sonically.

The tweeter section only needed a minor change to fit the new design. It was as simple as removing one cap and the new cross-over only needs 8 components to achieve the desired cross-over point at 2100Hz.

The v2.0 cross-over consist of a single inductor (L1) and with the above mentioned LC (C1, L2) notch-filter for the mid-woofer section. The tweeter uses a single cap + inductor (C2, L3) and has a response shaping circuit ( C3, R2) in order to reduce the tweeters rising top-end. The single resistor (R1) is used to attenuate the tweeter level to an appropriate level and personal taste.

The cross-over is an asymmetrical filter design with a mid-woofer acoustical 2nd order topology and a tweeter 3rd order topology. The asymmetrical filter design together with the relative acoustical off-set between the mid-woofer and the tweeter makes a perfect acoustical 2nd  LR cross-over filter with a 180deg phase shift at the cross-over point, which means that the tweeter must be connected in reverse polarity.

Left picture: Cross-over v1.0

Right picture: Cross-over v2.0

Left picture: System — 85dB @ 1m

Right picture: System — 90dB @ 1m

A tiny bit higher distortion numbers compared to the v1.0 cross-over, but it’s still very low.

Blue:  Filter v2.0 without notch (10cm near-field measurement)

Red: Filter v2.0 with notch (10cm near-field measurement)

The notch-filter reduces the cone break-up by 25dB. The “knee” between 5.5kHz and 7.5kHz are smaller in the far-field measurements and isn’t as pronounced in the off-axis measurements.

15deg off-axis cross-over simulation.

Notch filter and distortion measurements:

I’ve built the first prototype (see my last post) of the cross-over and made some distortion and mid-woofer near-field frequency measurements with the focus on the cone break-up behavior.

The mid-woofer cross-over section is made of a simple 2nd order electrical filter in order to achieve a 4th order LR cross-over slope with a cross-over point at 2000Hz. For the notch filter section a cap shunt over the series coil is used to reduce the cone break-up at 10kHz.

In order to simplify the cross-over and to get a more accurate notch filter, I choose the cap shunt instead of the LCR notch filter type. A cap shunt connected across the coil and in series with signal path, requires a high quality component in order not to degrade the sound quality.

Thanks to the relatively low cross-over frequency, the odd-order distortions are low, even at higher listening levels. There isn’t a huge difference in the distortion measurements between using a notch filter or not for the mid-woofer cone break-up.

Don’t be fooled by the distortion measurements alone, the cone break-up is very audible and a notch filter is a must. The notch filter reduces the break-up with an additional 15dB and the effect is clearly visible in the frequency measurements.

A brief listening test to the prototype cross-over suggests that some work needs to be done at the tweeter section in order to find the proper balance between the mid and highs and the tweeter level.

For the mid-woofer cross-over section I want to use a coil with as low internal resistance as possible. I will test and listen to both iron-core and copper-foil coils to determine the best choice for the design.

Left picture: Cross-over version 1.0 with mid-woofer notch filter – 85dB level.

Right picture: Cross-over version 1.0 without mid-woofer notch filter – 85dB level.

Blue = 10cm near-field measurement without notch filter.

Red = 10cm near-field measurement with notch filter.

I’ve begun with the cross-over simulations based on the frequency measurements I did last weekend. So far everything is going well and it was quite easy to simulate the first prototype cross-over design, which I will build, measure and listen to.

There are a couple of challenges to deal with in this design. First of all the mid-woofer cone break-up needs to be taken care of properly. I will use steep cross-over slopes (24dB/octave acoustical) and a notch filter to reduce the 10kHz break-up mode.

I’m not fully satisfied with the conventional LCR notch approach, instead I will try an alternative method to deal with the break-up and to reduce the complexity of the filter. Distortion measurements and listening tests will decide which method I will use.

Second, I have to deal with the tweeters rising top-end response and how much attenuation it needs in order to get a well-balanced sound that doesn’t sound to bright, but still manage to present an open and airy sound.

Left: On-axis Right: 15deg off-axis

Left: 22.5deg off-axis Right: Individual driver phase integration

The 1m measurement indicates that the mid-woofer relative acoustic off-set is approximately 25mm (1”) compared to the tweeter.

The cross-over simulation is optimized for the 15deg off-axis measurement and at a 2.5m listening distance.

As can been seen I’ve used almost a full baffle-step compensation and the sensitivity is about 81dB 2.83v/1m. Not exactly a high sensitivity design, but as expected when using such a small mid-woofer for woofer duties and not only for mid-range duties.

The mid-woofers cone break-up at 10kHz is well suppressed and the 13.5kHz and higher break-ups is suppressed by 45-50dB and should be off the audible radar.

The cross-over frequency occurs at 2100Hz and the phase integration between the mid-woofer and the tweeter is superb.

The tweeter has a rising top-end at the 0deg, on-axis frequency response and it’s still visible from 15kHz at the 15deg off-axis frequency response. Listening tests will decide if the tweeter needs more attenuation.

Personally I like when the on-axis response has a somewhat rising top-end, since it often contributes to a greater 3-D perspective and soundstage. However, to avoid an overly bright sound characteristic this calls for a non toe-in loudspeaker setup.

I have made frequency measurements for the “Excellence Two – Mini Monitor” this weekend and the measurements look good. Both the mid-woofers and the tweeters measures as expected and each sample are a close match to each other and the build consistency seems to be very good.

The mid-woofer has  cone break-ups at 10kHz and 13.5kHz. These break-ups are visible in the distortion measurements and have to be eliminated in the cross-over design with a notch filter centered at the stronger 10kHz break-up. They have a very smooth mid-range frequency response up to 2kHz where it starts to roll-off and does so without any visible cone-edge resonances. A 3-4dB BSC (Baffle Step Compensation) seems to be a good starting point to test with these mid-woofers.

The tweeter has a nice smooth frequency response with a slightly rising top-end response at the on-axis measurement. The baffle diffraction is noticeable at 3.5kHz as a mild dip in the frequency response. This dip flattens out as the off-axis angle increase and is gone at a 30 degree angle.

Now I have all the data to begin the cross-over simulation. 🙂

Sample 1 = Blue

Sample 2 = Red

For details see:

Driver Unit Measurements – Dayton Audio RS28F-4

Driver Unit Measurements – SEAS E0021 W12CY001

I have updated the Revelation Two – Monitor design with distortion measurements of the finished loudspeaker. I have also updated the driver unit measurements section with distortion measurements for the ScanSpeak mid-woofer 15W/4531G00 and the tweeter D2608/913000.

For details see:

Distortion measurements Revelation Two – Monitor

Distortion measurements ScanSpeak 15W/4531G00

Distortion measurements ScanSpeak D2608/913000