The last driver measurement to publish for the Sequence Three – Grand Reference loudspeaker design is the AudioTechnology 10C772510KAP 10” woofer. This woofer uses a very stiff rigid thick (2mm) sandwich cone. For its size it has an extended flat frequency response, with a cone break-up at approximately 1.9kHz.
Besides Troel Gravesens measurements, I haven’t seen any independent measurements made for this woofer. One thing that differs my measurements from Troels is that his cone break-up occurs higher up in frequency (2.5kHz), compared to my measurements.
In my case this is not an issue since I intend to cross-over the woofer to the mid-range somewhere between 3-400Hz. Even though the frequency response is very flat I doubt anyone would use this woofer any higher than 5-600Hz.
Next I will connect the Sequence Three – Grand Reference loudspeaker to my active DEQX HDP-3 system and start some listening and cross-over testing. 🙂
The woofer weighs about 8.5kg and is very robustly built. It has a large ventilation hole through the centre pole piece allowing for a compression free ventilation of the voice-coil. The ventilation hole is covered by foam.
The enclosure build is progressing as planned and the first box is finished. Some minor adjustments remain, but the build slowly beginning to nearing its final stage.
The next series of measurements I will publish is for the 10C772510KAP woofer, thereafter followed by DEQX measurements and some listening evaluation of the drivers capabilities.
All walls are covered with bitumen pads and some walls are covered with egg shaped foam and the enclosure is filled with sheep wool.
Two flared 70mm bass-reflex ports are housed in the bottom of the enclosure.
At the first look at the loudspeakers they look black, but they are actually dark grey. In real life they look a bit darker than the pictures.
Note the replacement baffle system and the separate tweeter enclosure than can be slide back and forth in order to fine tune the “relative acoustic center off-set” between the tweeter and the mid-range.
The speaker terminals are prepared for both active and passive cross-over use.
The next driver measurements to publish for the Sequence Three – Grand Reference loudspeaker design is the AudioTechnology 15H 52 12 06 SDKM. This is the pure mid-range version of the 15cm AT driver.
The mid-range is an over-hung version with a special mid-range surround for optimized frequency response. Measurements for the under-hung mid-woofer can be found here: AudioTechnology C-Quenze 15H 52 06 13 SDK
If we compare the two different versions we can see that the mid-range version both have a more linear frequency response as well as lower distortion throughout the mid-range drivers usable frequency range.
Blue = 15H 52 12 06 SDKM (mid-range) Red = 15H 52 06 13 SDK (mid-woofer)
Note! The SPL is normalized. They don’t have the same sensitivity.
The dip in the frequency response at 1.25kHz for the mid-woofer version caused by the cone-edge resonance is completely eliminated with the specially constructed surround of the mid-range driver.
To be honest, this dip in the frequency response is more of a cosmetical nature rather than technical, since it doesn’t have a large impact on the sonic performance of the mid-woofer.
The mid-range is perfectly usable up to about 3-3.5kHz and my goal is to use it up to 3kHz +/- 200Hz, where it’s crossed-over to the RAAL 140-15D ribbon tweeter.
Simulations, measurements and listening test will determin which filter topology to use, LR2 or LR4? If it works I would like use a shallower sloped filter e.g. a second-order LR, since I often think such filter topology sounds better if it can be done properly.
As can been seen the distortion is higher for the mid-woofer version when tested at medium-high levels. To sum up!
This mid-range driver from AudioTechnology delivers top notch measurement performance without any surprises as nasty cone break-ups, odd frequency response or distortion problems.
I think the mid-range will complement the RAAL 140-15D perfectly!
I’ve made some extensive measurements on the RAAL 140-15D ribbon tweeter and before the measurements I installed brand new replacement ribbons in both the RAAL tweeter samples and tightened up the ribbons as in this instruction video from RAAL.
As instructed, it worked perfectly. 🙂
Since it’s possible to shape the frequency response both vertically and horizontally with the supplied “foam deflection pads”, it seemed as the tweeter measurement setup could almost be done in an infinite number of variations.
I finally decided and ended up with the following tweeter configurations:
Upper Left: DPN = No “deflection pads”. Upper Right: DP1 = With “deflection pads” and 7cm visible ribbon. Lower Left: DP2 = With “deflection pads” and 5cm visible ribbon. Lower Right: DP3 = With “deflection pads” and 3cm visible ribbon.
The best overall balance and linearity between the horizontal and vertical frequency response is to use the “deflection pads” in the DP1 or DP2 setting e.g. 7cm or 5cm visible ribbon.
I wouldn’t recommend using the RAAL ribbon without the “foam deflection pads”. Without it the performance decreases in all aspects, both in frequency response and in distortion performance. Nevertheless I made a lot of measurements without the foam pads to have as a baseline to compare with.
Even though the RAAL ribbon is a very robust ribbon tweeter I made all frequency measurements with a 44uF protection cap connected in series with it.
Flush-mounting or not?
I’ve tested the RAAL ribbon with and without flush-mounting it on the baffle and the test results shows that there is no big diffraction problem and frequency response impact if it’s not flush-mounted.
Blue = No flush-mount
Red = Flush-mount
Upper Left: DPN
Upper Right: DP1
Lower Left: DP2
Lower Right: DP3
The face-plate of the RAAL ribbon is only 2mm thick and flush-mounting it is more or less a cosmetically decision rather than technical. All my published measurements are made with the RAAL ribbon flush-mounted using a 2-3mm thick felt carpet covering the entire baffle.
What about distortion?
The distortion figures isn’t up to the very best dome tweeter’s performance e.g. ScanSpeak D3004/664000 Beryllium tweeter, but for a ribbon tweeter still a respectable performance.
As can be seen on the distortion charts the gap between them narrows down with increasing SPL. Also the harmless second-order harmonics is actually lower for the ribbon. And obviously the dome tweeter can be crossed-over much lower without distortion issues.
When using the supplied “foam deflection pads” it actually helps lowering the distortion as well as controlling the vertical horizontal frequencies dispersion.
Based on the distortion figures I would recommend as many other people have for the RAAL ribbon tweeter, a cross-over point of about 3kHz or higher. If the max SPL requirement isn’t a concern or if you use steep filtering a 2-2.5kHz cross-over point could possibly work.
With the Sequence Three – Grand Reference loudspeaker design I’m aiming for a cross-over point of around 3kHz, so it’s seems to be working as I planned and expected. Further measurements and of course listening test will finally decide the exact cross-over point. With the AT mid-range and the RAAL ribbon I will have a possible cross-over range somewhere between 2.5-3.5kHz. Not a super wide range, but wide enough to make it work.
To sum up, I think the RAAL 140-15D measurement performance lives up to my expectations and I’m eager to continue with the Sequence Three – Grand Reference loudspeaker design. Next up is to publish the results from the AudioTechnology mid-range measurements.
The work is proceeding as planned even though it has been delayed a bit by bad weather. Unfortunately the Swedish summer weather is a bit unpredictable. 🙂
Lately the work has mostly been – sand, fill, sand, fill, sand, fill, sand……… I almost forgot how boring I think sanding is. 😉
Currently I’m working on the loudspeaker foot as well as attaching additional bracing and damping in the woofer section. I’m also planning for the spray painting of the baffles and some parts of the enclosure. The final finishing of the loudspeaker isn’t 100% decided yet.
Left: Mid-woofer and Tweeter baffles.
Right: Woofer baffles
The left loudspeaker shows the tweeter/cross-over enclosure and the baffles, excluding the loudspeaker foot. The right loudspeaker shows the mid/woofer enclosure without baffles.
There has been a bit quiet here on the AudioExcite blog for a while, since work and family vacation had priority over speaker building and blog writing. Even though there hasn’t been much writing lately you can rest assured that the speaker building continues unabated. 🙂
I’ve started the Sequence Three – Grand Reference enclosure construction and I will continuously report about the building progress as it proceeds.
The Sequence Three – Grand Reference enclosure is made of two parts, one which contains the tweeter and the cross-over and one which contains the mid-woofer and the woofer. The top tweeter enclosure can slide back and forth in order to be able to adjust the acoustical off-set between the tweeter and mid-woofer, if needed in the design.
All baffles uses a baffle replacement system in order to be able to swap drivers in and out as needed and at the same time make the enclosure somewhat future proof.
The overall enclosure dimension is (WxHxD) 33x105x43cm incl. feets + baffle thickness. The tweeter and mid-woofer replacement baffle is 19mm thick, while the woofer baffle is 38mm thick.
The tweeter + cross-over enclosure is 33x20x43cm + the tweeter baffle. The mid-woofer and woofer enclosure are 33x78x43cm + the baffles. The two bass-reflex ports are mounted in the bottom of the enclosure. The enclosure feet’s are 7cm high including the “Sonic Design” damping feet’s.
All internal walls are covered with 4mm bitumen pads as well as bracings for the mid-woofer and woofer section.
The woofer net volume is about 64 liter minus the volume for the bracing, bitumen pads, bass-reflex ports and driver, which gives approximately 55-56 liter for the woofer to work in. The mid-woofer and tweeter sections are about 18 liter volume each.
Upper Left: Mid-woofer and woofer enclosure.
Upper Right: Woofer section.
Lower Left: Mid-woofer section.
Lower Right: Tweeter and cross-over enclosure.
Upper Left: Round-over jig.
Upper Right: Mid-woofer chamfering.
Lower Left: Woofer routing and flush-mount cutout.
Lower Right: Milled groove to be filled with elastic filler for invisible MDF board joints.
After a period of additional listening tests and by request of DIY builders, I here describe more tweeter tuning options for the Prestigious Two – Monitor DXT loudspeaker. The original version could sound a bit to warm or light dark at times depending on which stereo equipment where used or how the loudspeaker was placed and toed-in etc.
All the options below are technically equally good and the phase behavior and phase tracking around the cross-over frequency are not compromised at all compared to the original version. The large amount of tweeter padding options are available so each and every one can find their own setting that fits their personal tweeter level preference and taste in combination with their HiFi equipment, room interaction and setup.
I urge everyone to buy a couple of extra resistors for this build and try out some of the tweeter options. It really pays off, since what seems to be a small change in the frequency chart can be could be a significant difference that works out in your setup.
In some of the options the actual cross-over frequency is lowered compared to the original version and it’s perfectly normal, since the lower treble output is higher in these versions, but the configurations are carefully chosen in order to have optimal phase tracking around the cross-over frequency. You can see the phase tracking effect of the different tweeter level options by looking at the “reverse null” charts, which all show a very deep null as they should and it indicates a good phase behavior around the cross-over point.
All frequency charts use a 1/24 octave smoothing and are based around the 15deg off-axis measurements. The grey reference line (83dB) is used in order to easier see the effect of the different tweeter level options.
The resistor R1 is used to change the upper treble level from 8kHz and up and the resistor R3 is used to change the lower treble to mid treble level.
I think it turned out to be a very nice modestly priced loudspeaker design. The SEAS DXT tweeter, although not my absolute favorite tweeter is a very interesting concept with great potential and I hope to see more of its kind from SEAS and other loudspeaker driver unit manufacturers.
I’ve tested and used the DXT tweeter in several designs and I think it really shines when used with a LR2 (acoustical) filter topology.
The bass from the small SEAS U16RCY/P is very good and I think the warm mid-range character it reproduces, will appeal to many people.
I also think the cross-over design worked out the way I wanted, with a minimalistic design approach and with very few components. It’s not often a loudspeaker design work out as good as this with a first-order (electrically) filter topology, but both these good drivers can handle it.
This is the last design I publish before the family vacation starts, but stay tuned I have several exciting designs coming soon.
First of all I’m starting the “Sequence Three – Grand Reference” build this summer and parallel to it I will start the work with the “Revelation Two – Monitor MkII”, which will be released with two new different tweeter flavors.
Finally the driver units for the “Reference” build has been chosen and delivered to me. 🙂
This is a construction which I will build in parallel with other smaller projects and I think it will take some considerable time to finish it. I have no rush into getting this “Reference” loudspeaker up and running, but I will publish measurements and design thoughts here in my construction blog, along the way the design project progresses and develops.
The driver units used in the “Sequence Three – Grand Reference” 3-way loudspeaker:
Tweeter:
Here I will use the RAAL 140-15D Ribbon Tweeter. This is a ribbon tweeter that many people regards to be one of the best ribbon tweeters on the market and it’s supposed to have very low distortion compared to other ribbon tweeters. Time will tell if it’s true or not and I will release extensive measurements to evaluate the claims.
Mid-range:
Here I will use the AudioTechnology C-Quenze 15H-52-12-06-SDKM. This is the mid-range version of the 15H 5” mid-woofer and it has a special rubber mid-range surround. This is the “over-hung” version with a Kapton voice-coil former. According to AudioTechnology the “over-hung” version of the mid-range has a bit more detailed mids and “monitor” characteristics as well as higher sensitivity compared to the “under-hung” version.
Woofer:
Here I will use the AudioTechnology Flex-Units 10C-77-25-10-KAP. This is a 10” driver with a woofer cone made from two thin carbon reinforced paper cones. The result is an extremely rigid and stiff cone. The kapton voice-coil former is laminated with aluminium foil and presents a very low mechanical resistance, which allows the driver to play bass with authority, even at low levels.
The woofer weighs about 8.5kg and is very robustly built. It has a large ventilation hole through the centre pole piece allowing for a compression free ventilation of the voice-coil. The ventilation hole is covered by foam.
The mid-range has the special rubber mid-range surround with an unusual looking shape. The mid-range also has a similar ventilation of the voice-coil, as the woofer.
All the “Sequence Three – Grand Reference” driver units showed together. Note! the huge magnet size on the woofer compared to the mid-range, which also have large magnet considering its size.
I’ve started a new build project called “Prestigious Two – Monitor DXT” and currently I’m in the fine tuning, listening test and final measurement project stage. This time I’ve used less expensive driver units from the “Seas Prestige line”. The mid-woofer used is the U16RCY/P, which has a woven polypropylene cone and phase plug.
The mid-woofer has a smooth extended frequency response with a controlled roll-off, without nasty cone break-ups. For its size it has a large radiating surface (99cm²) and the bass performance is very good.
I’ve used both these drivers in active as well as passive loudspeaker designs before, but I haven’t been fully satisfied with the end result and I have always thought they could perform even better and now I think I’ve succeeded!
The DXT tweeter isn’t the easiest tweeter to work with. Don’t misunderstand me, it’s not that hard to shape it in to a working cross-over that on paper looks good, but in my opinion this tweeter has a tendency to become dull, un-engaging and less musical in certain configurations.
I found this tweeter to work and sound the best in a second-order LR filter topology (acoustically). This means that in order to use a simple electrically first-order filter it needs to be crossed-over a bit higher up in frequency to ensure that it operates within its “comfort zone”. In this case I’ve targeted a 3kHz cross-over point for the design.
On the other hand, this requires a mid-woofer capable of a 3kHz cross-over point without sacrificing any off-axis dispersion (beaming) and to match the DXT tweeters excellent and controlled off-axis frequency characteristics. The Seas U16RCY/P fulfills that together with a very smooth and controlled frequency slope roll-off, without the need to do corrections for nasty cone break-ups.
To sum up, this all ended up in a very simple cross-over design, which was one of the goals of this loudspeaker design.
The mid-woofer cross-over filter section is an electrical first-order and is very simple and consists only of a large coil (L1) that shapes the cross-over slopes to a LR2 roll-off with a targeted 3kHz cross-over point. The inductor (L1) also tunes the “Baffle Step Compensation” (BSC).
The tweeter cross-over filter section consists of a single tweeter padding resistor (R1) and a first-order electrical filter (C1) that shapes the cross-over slope to a LR2 roll-off with a targeted 3kHz cross-over point. The value of (R1) can be changed to tailor the tweeter level to personal preferences.
The tweeter is connected with reverse polarity and (C2+R2+R3) shape the tweeters frequency response and flatten the response at higher frequencies.
Simulated 15deg off-axis frequency response with a targeted second-order LR topology (acoustical). Cross-over point at 3kHz. Note the tweeters sharp peak at the hard dome break-up frequency!
