Crossover Trial Tweak Download
10/02 A short study on the validity of a generic 2-way
The Objective:
In the forum postings, I have often read of the trials of aspiring speaker builders overcoming the pitfalls of
could be devised that would take into account some of the variables implicit in such a design, such as BSC
and tweeters in a simple enclosure and still provide an acceptable on axis FR (frequency response) of within +/-
The Assumptions:
Of course no crossover can be truly universal, so certain limitations and assumptions must be made to define
For the purposes of this study, it is assumed the published information is accurate, and that the crossover
crossover point. On one hand you have the Fs of the tweeters, which should be at least one octave below the
4KHz. With this in mind, as well as the driver spacing limitations, I chose 2350 Hz as the target crossover point.
> Baffle configuration:
One consideration necessary in order to achieve flat frequency response is to account for the diffraction effects
MT designs and a 9 in. by 28 in. for MTMs. For ease of construction, no chamfering or rounding was modeled.
woofer was centered 10 inches from the top of the baffle. On the MTM, the top woofer was modeled centered
woofer centered 18 inches from the top of the baffle. The center-to-center spacing between the mid/woofer and
maximum size of the mid/woofer to approximately 8 inches.
> Acoustic centers:
A difference in signal propagation time will occur if the distances from the acoustic centers of the woofer and
and cause frequency response abnormalities in the crossover region. In the MT crossover, no attempt was made
tilt the baffle to align the centers. This can be done either by sloping the front baffle, or tilting the entire
assumed 6 ohms and 1.0 mh. For the tweeter, 5 ohms and 0.05 mh.
> Driver FR:
The drivers should have a flat FR throughout the pass band, and ideally at least one octave past the crossover
The Design Process:
To compensate for diffraction effects, I first determined a target response for the system. This is required as
and driver orientation using Paul Verdone's BDS program, and determined the woofer diffraction effects (gain)
caused by the baffle. This curve was inverted and exported to Ingemar Johansson'sLspCAD to provide the
target response, or attenuation required to obtain a flat on axis frequency response. Different target responses
response and the transfer functions of the crossovers selected. My initial investigation was to see if an acoustic
the crossover frequency. Importing various driver FR files however, indicated insufficient attenuation with some
the attenuation was still insufficient in some cases. I then modeled an acoustic 4th order LR, and found the
attenuation was adequate to mitigate the response irregularities of most drivers, including some with some
4100 Hz. This peak was attenuated acceptably using this modeled crossover. A zobel circuit was used to allow
provided acceptable results with a variety of tweeters. Phase tracking was good, assuming proper alignment of
target curve for the MTM baffle, and modified
the assumption of the tweeter and woofers relative acoustic centers, but due to the sharp roll off rates of the
impedance curves for the MTM remained above 4 ohms for all the drivers I modeled.
The Circuits:
MT woofer networkMT tweeter networkMTM woofer networkMTM tweeter network
The circuit topology turned out to be quite simple and is the same for both designs. Any resistors with values
For the low pass network, a third order electrical filter with zorbel was used to achieve the BSC and the 4th
a 4th order acoustic slope. The two resistors after the network represent an L-pad, or fixed resistors for tweeter
The Tweaks:
For most of the drivers I modeled, the frequency response criteria of +/- 3 dB could be achieved by merely
design, I would suggest purchasing a pair of L-pads for each speaker to do the initial voicing adjustments. The
resistance with respect to the middle terminal when the L-pad is turned fully clockwise. On the ones I tested,
but abruptly went open circuit at the full clockwise position.. To obtain the best response, additional resistance
will reduce the resistance, and reduce the woofer output from roughly 700 Hz to 2 KHz. Note that while the
or lowering both L-pads simultaneously.
Additional Tweaks:
While the modeled frequency response of most drivers fell acceptably within my +/- 3 db target using only the
system.
>Low pass section:
Reducing the value of L1 will have the effect of lessening the baffle step. Note that this will also raise the
change in the crossover frequency, at the expense of making the system slightly less efficient.
Increasing the value of C1 will lower the crossover frequency and affect the FR around the crossover
crossover frequency.
Modeled Results:
After determining the final values and topology for this circuit, I wondered if it would model well with a woofer
I selected the response curves of a SEAS L17REP, a 6.5 inch aluminum cone driver to model with my TM
accompanying snapshot. The blue curve is the SEAS woofer without the
sufficiently far down in the pass band as to mitigate their audible effects. The red curve is an SS9500 with
the black band is the combined response with the tweeter out of phase, showing good phase tracking through
Conclusions:
This was a design study. I have not used this crossover in an actual design. However, the modeling of various
results. A reasonably flat modeled frequency response is accomplished in most instances with no adjustments
actual drivers in the intended enclosure with an optimized crossover design unique for that specific application.
equipment or design software, I suggest the topologies presented here might be used as a template for further
Erratum:
While I made every attempt to insure the validity of my procedures, data, and results. I do not profess to
constructive comments or suggestions you may have.
Copyright 2002 by Curt Campbell
Crossover Trial Tweak 2020
The Objective:
In the forum postings, I have often read of the trials of aspiring speaker builders overcoming the pitfalls of
could be devised that would take into account some of the variables implicit in such a design, such as BSC
and tweeters in a simple enclosure and still provide an acceptable on axis FR (frequency response) of within +/-
The Assumptions:
Of course no crossover can be truly universal, so certain limitations and assumptions must be made to define
For the purposes of this study, it is assumed the published information is accurate, and that the crossover
crossover point. On one hand you have the Fs of the tweeters, which should be at least one octave below the
4KHz. With this in mind, as well as the driver spacing limitations, I chose 2350 Hz as the target crossover point.
> Baffle configuration:
One consideration necessary in order to achieve flat frequency response is to account for the diffraction effects
MT designs and a 9 in. by 28 in. for MTMs. For ease of construction, no chamfering or rounding was modeled.
woofer was centered 10 inches from the top of the baffle. On the MTM, the top woofer was modeled centered
woofer centered 18 inches from the top of the baffle. The center-to-center spacing between the mid/woofer and
maximum size of the mid/woofer to approximately 8 inches.
> Acoustic centers:
A difference in signal propagation time will occur if the distances from the acoustic centers of the woofer and
and cause frequency response abnormalities in the crossover region. In the MT crossover, no attempt was made
tilt the baffle to align the centers. This can be done either by sloping the front baffle, or tilting the entire
assumed 6 ohms and 1.0 mh. For the tweeter, 5 ohms and 0.05 mh.
> Driver FR:
The drivers should have a flat FR throughout the pass band, and ideally at least one octave past the crossover
The Design Process:
To compensate for diffraction effects, I first determined a target response for the system. This is required as
and driver orientation using Paul Verdone's BDS program, and determined the woofer diffraction effects (gain)
caused by the baffle. This curve was inverted and exported to Ingemar Johansson'sLspCAD to provide the
target response, or attenuation required to obtain a flat on axis frequency response. Different target responses
response and the transfer functions of the crossovers selected. My initial investigation was to see if an acoustic
the crossover frequency. Importing various driver FR files however, indicated insufficient attenuation with some
the attenuation was still insufficient in some cases. I then modeled an acoustic 4th order LR, and found the
attenuation was adequate to mitigate the response irregularities of most drivers, including some with some
4100 Hz. This peak was attenuated acceptably using this modeled crossover. A zobel circuit was used to allow
provided acceptable results with a variety of tweeters. Phase tracking was good, assuming proper alignment of
target curve for the MTM baffle, and modified
the assumption of the tweeter and woofers relative acoustic centers, but due to the sharp roll off rates of the
impedance curves for the MTM remained above 4 ohms for all the drivers I modeled.
The Circuits:
MT woofer networkMT tweeter networkMTM woofer networkMTM tweeter network
The circuit topology turned out to be quite simple and is the same for both designs. Any resistors with values
For the low pass network, a third order electrical filter with zorbel was used to achieve the BSC and the 4th
a 4th order acoustic slope. The two resistors after the network represent an L-pad, or fixed resistors for tweeter
The Tweaks:
For most of the drivers I modeled, the frequency response criteria of +/- 3 dB could be achieved by merely
design, I would suggest purchasing a pair of L-pads for each speaker to do the initial voicing adjustments. The
resistance with respect to the middle terminal when the L-pad is turned fully clockwise. On the ones I tested,
but abruptly went open circuit at the full clockwise position.. To obtain the best response, additional resistance
will reduce the resistance, and reduce the woofer output from roughly 700 Hz to 2 KHz. Note that while the
or lowering both L-pads simultaneously.
Additional Tweaks:
While the modeled frequency response of most drivers fell acceptably within my +/- 3 db target using only the
system.
>Low pass section:
Reducing the value of L1 will have the effect of lessening the baffle step. Note that this will also raise the
change in the crossover frequency, at the expense of making the system slightly less efficient.
Increasing the value of C1 will lower the crossover frequency and affect the FR around the crossover
crossover frequency.
Modeled Results:
After determining the final values and topology for this circuit, I wondered if it would model well with a woofer
I selected the response curves of a SEAS L17REP, a 6.5 inch aluminum cone driver to model with my TM
accompanying snapshot. The blue curve is the SEAS woofer without the
sufficiently far down in the pass band as to mitigate their audible effects. The red curve is an SS9500 with
the black band is the combined response with the tweeter out of phase, showing good phase tracking through
Conclusions:
This was a design study. I have not used this crossover in an actual design. However, the modeling of various
results. A reasonably flat modeled frequency response is accomplished in most instances with no adjustments
actual drivers in the intended enclosure with an optimized crossover design unique for that specific application.
equipment or design software, I suggest the topologies presented here might be used as a template for further
Erratum:
While I made every attempt to insure the validity of my procedures, data, and results. I do not profess to
constructive comments or suggestions you may have.
Copyright 2002 by Curt Campbell
Crossover Trial Tweak 2020
Objective Although crossover trials enjoy wide use, standards for analysis and reporting have not been established. We reviewed methodological aspects and quality of reporting in a representative sample of published crossover trials. Methods We searched MEDLINE for December 2000 and identified all randomized crossover trials. We abstracted data independently, in duplicate, on 14 design. This is the fifth of an occasional series on the methods of randomised controlled trials In a crossover trial subjects are randomly allocated to study arms where each arm consists of a sequence of two or more treatments given consecutively. The simplest model is the AB/BA study. Subjects allocated to the AB study arm receive treatment A first, followed by treatment B, and vice versa in the BA. A crossover randomised controlled trial (RCT) is a specific type of RCT where you assess 2 or more interventions. In this design, all participants receive all the interventions, but the order in.