Introduction
Many impressive small monitor projects have been presented on the pages of HT Guide and other publications, with the concept that, if you mate this with a good "bass bin" concept for music, you will have an exceptional high performance system. The proposed Ascent two way is an example, as well as the older NatlieP and Modula MT designs. Many others from other contributors exist, with similar performance credentials. For the moment, we will not discuss if what seems to be a two way can really fully compete with a well engineered three way system with optimized selection of the midrange driver. Instead, we will simply present a proposal (currently in construction and to be tested soon) for a modular bass bin approach derived from a few key points:
Core LF Driver
Many manufacturers offer nominally high performance small subwoofer drivers; few have taken a driver design and utilized feedback from an experienced engineer such as Sigfried Linkwitz and corrected/updated the design of the driver for truly impressive large signal behavior. The Seas Design L26RO4Y is that driver, and delivers exceptional performance for a 10" driver.
While not suited for delivering infrasonic frequencies in a Home Theater system, due to it's T/S parameters, for music it may be effectively unchallenged for this driver class, considering overall sensitivity, large signal distortion, Xmax, and compact size.
But this driver will not meet the overall low frequency output goals on it's own- and considering the tunings desired, a port in a small enclosure is not feasible. It is most unfortunate that Seas is currently not able to deliver a passive radiator matched to this driver- investigations by our agents have indicted that manufacturing issues with surround and suspension are the blocking issues.
However, there is another....
ScanSpeak 26W/0-00 Passive Radiator
This driver has the mechanical properties needed to work with the L26RO4Y driver, and appears to be readily available. It also has an adjustable mass system, like many PR's, but the starting mass point is near ideal for the proposed system alignment.
Enclosure
The ideal enclosure starting point should be ~40L, well braced, compact in dimensions, and as a stretch goal, available with a cutout for the driver matching the Seas L26RO4Y. Note the mechanical dimensions of the Seas woofer.
Sometimes, the Force is with us....
PE Enclosure for Ultimax 10" subwoofer
The L26ROY fits quite well in the rebated mounting for the Ultimax woofer, being just very sightly smaller in outside frame diameter and cutout requirement. Construction of one of these to test is nearly complete. Details, including modifications for optimizing the PR mounting, will be posted soon.
Modularity/Extensibility
Last, let us examine some possible options for extensibility of this proposed configuration beyond a mono or stereo woofer concept with a single or dual cabinet.
In detail, the characteristic for a single cabinet and driver, noting the sensitivity and output capability, with the T/S parameter analysis.
First, the rather obvious possibility of dual woofers wired in series (these are 4 ohm drivers).
With the second driver, for the same power feed, a 3 dB increase in sensitivity is normal. In this case, though, the impedance is doubling, so driving with the same 2.83VRMS the actual power delivered is halved, so for 2.83VRMS drive, the sensitivity remains unchanged.
What about a 3rd driver?
Now we see a further increase in the true 1W sensitivity, while due to the increased load impedance (roughly 12 ohms), the current draw for 2.83VRMS driver is further reduced, resulting in the same net sensitivity as for the other two cases- but the ability to handle three times the power and deliver higher SPL.
An intriguing point is reached if we take this array of three drivers in series, and add a second array in parallel. In this case, the net sensitivity goes up 6 dB- 3 dB for the driver area and coupling, and three dB for the doubled current/power draw- with a six ohm load this is fairy easy to manage for almost any solid state amplifier, and often is the maximum power output impedance if the power supply hasn't been carefully optimized for low impedance loads. In this case, though, we see a sensitivity of 95.2 dB for 1 watt driver power, and acoustic output of 118 dB (from one array, anechoic, while not stressing the drivers) - definitely showing characteristics suited to a high end line array.
What do we mean by not stressing the drivers? This is the predicted cone excursion with 100W to 2 drivers, the same nominal 50W working per driver- clearly, over 3 dB of headroom exists for the woofer and PR.
Many impressive small monitor projects have been presented on the pages of HT Guide and other publications, with the concept that, if you mate this with a good "bass bin" concept for music, you will have an exceptional high performance system. The proposed Ascent two way is an example, as well as the older NatlieP and Modula MT designs. Many others from other contributors exist, with similar performance credentials. For the moment, we will not discuss if what seems to be a two way can really fully compete with a well engineered three way system with optimized selection of the midrange driver. Instead, we will simply present a proposal (currently in construction and to be tested soon) for a modular bass bin approach derived from a few key points:
- Compact size, and frequency extension versus size focussed more on the needs of music, rather than HT with subsonic explosions
- Robust large signal behavior with a driver design specifically optimized for that characteristic
- Low distortion
- Compact
- Easy to build, with only a few tools (saber saw and drill at minimum; router recommended)
- Extensible and modular - capable of being scaled up to a true technological terror with the same tool set
- Components selected from multiple vendors, each optimized for key functional aspects addressing these requirements
Core LF Driver
Many manufacturers offer nominally high performance small subwoofer drivers; few have taken a driver design and utilized feedback from an experienced engineer such as Sigfried Linkwitz and corrected/updated the design of the driver for truly impressive large signal behavior. The Seas Design L26RO4Y is that driver, and delivers exceptional performance for a 10" driver.
While not suited for delivering infrasonic frequencies in a Home Theater system, due to it's T/S parameters, for music it may be effectively unchallenged for this driver class, considering overall sensitivity, large signal distortion, Xmax, and compact size.
But this driver will not meet the overall low frequency output goals on it's own- and considering the tunings desired, a port in a small enclosure is not feasible. It is most unfortunate that Seas is currently not able to deliver a passive radiator matched to this driver- investigations by our agents have indicted that manufacturing issues with surround and suspension are the blocking issues.
However, there is another....
ScanSpeak 26W/0-00 Passive Radiator
This driver has the mechanical properties needed to work with the L26RO4Y driver, and appears to be readily available. It also has an adjustable mass system, like many PR's, but the starting mass point is near ideal for the proposed system alignment.
Enclosure
The ideal enclosure starting point should be ~40L, well braced, compact in dimensions, and as a stretch goal, available with a cutout for the driver matching the Seas L26RO4Y. Note the mechanical dimensions of the Seas woofer.
Sometimes, the Force is with us....
PE Enclosure for Ultimax 10" subwoofer
The L26ROY fits quite well in the rebated mounting for the Ultimax woofer, being just very sightly smaller in outside frame diameter and cutout requirement. Construction of one of these to test is nearly complete. Details, including modifications for optimizing the PR mounting, will be posted soon.
Modularity/Extensibility
Last, let us examine some possible options for extensibility of this proposed configuration beyond a mono or stereo woofer concept with a single or dual cabinet.
In detail, the characteristic for a single cabinet and driver, noting the sensitivity and output capability, with the T/S parameter analysis.
First, the rather obvious possibility of dual woofers wired in series (these are 4 ohm drivers).
With the second driver, for the same power feed, a 3 dB increase in sensitivity is normal. In this case, though, the impedance is doubling, so driving with the same 2.83VRMS the actual power delivered is halved, so for 2.83VRMS drive, the sensitivity remains unchanged.
What about a 3rd driver?
Now we see a further increase in the true 1W sensitivity, while due to the increased load impedance (roughly 12 ohms), the current draw for 2.83VRMS driver is further reduced, resulting in the same net sensitivity as for the other two cases- but the ability to handle three times the power and deliver higher SPL.
An intriguing point is reached if we take this array of three drivers in series, and add a second array in parallel. In this case, the net sensitivity goes up 6 dB- 3 dB for the driver area and coupling, and three dB for the doubled current/power draw- with a six ohm load this is fairy easy to manage for almost any solid state amplifier, and often is the maximum power output impedance if the power supply hasn't been carefully optimized for low impedance loads. In this case, though, we see a sensitivity of 95.2 dB for 1 watt driver power, and acoustic output of 118 dB (from one array, anechoic, while not stressing the drivers) - definitely showing characteristics suited to a high end line array.
What do we mean by not stressing the drivers? This is the predicted cone excursion with 100W to 2 drivers, the same nominal 50W working per driver- clearly, over 3 dB of headroom exists for the woofer and PR.
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