Owner's Manual for Pete Riggle 8 Ohm Hiraga Circuit Crossover with Supertweeter Circuit Option
About the Hiraga Circuit
The Hiraga circuit was developed by Jean Hiraga, a renowned French audiophile, for a pair of Altec A5 speakers using one Altec 515 woofer and one Altec 1505 15 cell tweeter horn per channel. Hiraga used a notch filter to achieve a broad, shallow 4 dB dip in the high pass response. The dip begins near the crossover frequency, gradually arrives at a low point at about 3.5 kHz, and and gradually returns to the reference level around 9 kHz. Beyond 9 kHz the output gradually rises, helping to compensate for tweeter fall off beyond 9 kHz.
For more detail than presented in this manual on the Hiraga circuit and its behavior , please go to the following link, Hiraga Circuit Crossovers, where calculated response curves are given.
Pete Riggle tried an 8 Ohm version of the Hiraga circuit with his Altec A7-500 8 Ohm Voice Of The Theatre speakers, and was more than pleased with the results. This crossover should work well with any 2-way loudspeaker system, or 2-way system with capacitor blocked supertweeter, capable of being crossed over as low as 525 Hz.
The Pete Riggle version of the Hiraga crossover circuit is calculated by the SPICE program to cross over at 525 Hz into constant 8 ohm resistances. Driver deviations from constant resistance will cause variations from said SPICE calculations. Nonetheless, the SPICE results are a good initial guide to the actual performance.
Switches are provided to allow the maximum notch depth to be set at -4 dB, -2dB, or flat in the region of the notch, which is between the 525 Hz crossover frequency and 9 kHz.
It is characteristic of a second order crossover to have a bump in output somewhere near the crossover frequency. For this crossover the bump is about 2 dB at 450 Hz.
Connect The Amplifer(s), Woofer, Tweeter, and Supertweeter (supertweeter optional)
The photo below shows the rear panel of one of the crossovers.
The Hiraga circuit was developed by Jean Hiraga, a renowned French audiophile, for a pair of Altec A5 speakers using one Altec 515 woofer and one Altec 1505 15 cell tweeter horn per channel. Hiraga used a notch filter to achieve a broad, shallow 4 dB dip in the high pass response. The dip begins near the crossover frequency, gradually arrives at a low point at about 3.5 kHz, and and gradually returns to the reference level around 9 kHz. Beyond 9 kHz the output gradually rises, helping to compensate for tweeter fall off beyond 9 kHz.
For more detail than presented in this manual on the Hiraga circuit and its behavior , please go to the following link, Hiraga Circuit Crossovers, where calculated response curves are given.
Pete Riggle tried an 8 Ohm version of the Hiraga circuit with his Altec A7-500 8 Ohm Voice Of The Theatre speakers, and was more than pleased with the results. This crossover should work well with any 2-way loudspeaker system, or 2-way system with capacitor blocked supertweeter, capable of being crossed over as low as 525 Hz.
The Pete Riggle version of the Hiraga crossover circuit is calculated by the SPICE program to cross over at 525 Hz into constant 8 ohm resistances. Driver deviations from constant resistance will cause variations from said SPICE calculations. Nonetheless, the SPICE results are a good initial guide to the actual performance.
Switches are provided to allow the maximum notch depth to be set at -4 dB, -2dB, or flat in the region of the notch, which is between the 525 Hz crossover frequency and 9 kHz.
It is characteristic of a second order crossover to have a bump in output somewhere near the crossover frequency. For this crossover the bump is about 2 dB at 450 Hz.
Connect The Amplifer(s), Woofer, Tweeter, and Supertweeter (supertweeter optional)
The photo below shows the rear panel of one of the crossovers.
Connect the amplifier(s):
Begin by connecting the power amplifier(s) for each crossover network.
Operation with one power amplifier channel per speaker channel:
In the photo above the lower terminals (marked red) are the plus terminals. The upper terminals (marked black) are the minus terminals. The Bass Amp Input shown in the photo operates the low pass filter which drives the woofer. The Treble Amp input operates the high pass filter which drives the tweeter, and drives the supertweeter (if one is used). Many users will choose to drive each crossover with one power amplifier shared by low and high pass circuits. As shipped the Bass Amplifier plus input of each crossover unit is connected by a short wire to the Treble Amplifier plus input. Similarly the Bass Amplifier minus input of each crossover unit is connected by a separate short wire to the Treble Amplifier minus input. These connections allow each speaker to be driven by a single power amplifier, requiring two channels of power amplification, one for the left channel, and one for the right channel.
Operation with two power amplifier channels per speaker channel (biamping):
If the crossover is to be operated with a bass amplifier and a treble amplifier, the short wires discussed above will be removed and stored. The amplifier deemed to have the best bass response will be connected to the Bass Amp Input. The amplifier deemed to have the best treble response will be connected to the Treble Amp Input. The provision of separate inputs for bass and treble amplifiers does not reflect a judgement, one way or the other regarding the superiority of either single power amp operation or dual power amp operation.
Connect Woofer, Tweeter, and Supertweeter
Connect to the crossover output terminals as labeled. The lower terminals are plus (red). The upper terminals are minus (black). Connect the plus (red) wires to the lower terminals. Connect the minus (black) wires to the upper terminals. A supertweeter is not required. If you choose not to use a supertweeter, simply leave the terminals unused, and switch off the supertweeter with a switch on the front panel. It is characteristic of a second order crossover, such as the Hiraga circuit, to require a phase reversal between bass and treble drivers. This reversal is built into the crossover circuit and should not be made at the speaker connection terminals.
Controls
Controls are on the front panel as shown in the photo below. Three toggle switches are located on the front panel. The toggle switch to the right engages or disengages the supertweeter circuit. Toggle up is engaged. Toggle down is disengaged.
Begin by connecting the power amplifier(s) for each crossover network.
Operation with one power amplifier channel per speaker channel:
In the photo above the lower terminals (marked red) are the plus terminals. The upper terminals (marked black) are the minus terminals. The Bass Amp Input shown in the photo operates the low pass filter which drives the woofer. The Treble Amp input operates the high pass filter which drives the tweeter, and drives the supertweeter (if one is used). Many users will choose to drive each crossover with one power amplifier shared by low and high pass circuits. As shipped the Bass Amplifier plus input of each crossover unit is connected by a short wire to the Treble Amplifier plus input. Similarly the Bass Amplifier minus input of each crossover unit is connected by a separate short wire to the Treble Amplifier minus input. These connections allow each speaker to be driven by a single power amplifier, requiring two channels of power amplification, one for the left channel, and one for the right channel.
Operation with two power amplifier channels per speaker channel (biamping):
If the crossover is to be operated with a bass amplifier and a treble amplifier, the short wires discussed above will be removed and stored. The amplifier deemed to have the best bass response will be connected to the Bass Amp Input. The amplifier deemed to have the best treble response will be connected to the Treble Amp Input. The provision of separate inputs for bass and treble amplifiers does not reflect a judgement, one way or the other regarding the superiority of either single power amp operation or dual power amp operation.
Connect Woofer, Tweeter, and Supertweeter
Connect to the crossover output terminals as labeled. The lower terminals are plus (red). The upper terminals are minus (black). Connect the plus (red) wires to the lower terminals. Connect the minus (black) wires to the upper terminals. A supertweeter is not required. If you choose not to use a supertweeter, simply leave the terminals unused, and switch off the supertweeter with a switch on the front panel. It is characteristic of a second order crossover, such as the Hiraga circuit, to require a phase reversal between bass and treble drivers. This reversal is built into the crossover circuit and should not be made at the speaker connection terminals.
Controls
Controls are on the front panel as shown in the photo below. Three toggle switches are located on the front panel. The toggle switch to the right engages or disengages the supertweeter circuit. Toggle up is engaged. Toggle down is disengaged.
The two toggles on the left control the maximum depth of the response notch (in the region between crossover frequency and 9 kHz). The maximum possible notch depth is -4 dB, achieved by having both toggles down. One toggle up and one down (which is up and which is down makes on difference in response) provides a maximum notch depth of -2 dB. Both toggles up provides a flat response between the crossover frequency and 9 kHz.
Two L-pad level controls, labeled "AUDIO LEVEL" are provided. The control on the left adjusts the tweeter level relative to the woofer level.
The control on the right adjusts supertweeter level relative to tweeter level. The supertweeter volume control and the supertweeter are piggy-backed off the tweeter volume control. This causes the supertweeter level to move up and down with the tweeter level.
Supertweeter Effect
On the A7-500 8 Ohm Altec Voice Of The Theatre Speakers of Pete Riggle and Pete's audio wing-man, Stephaen Harrell, the effect of using a capacitor blocked supertweeter is stunning. The supertweeter model we have experience with is the Harman/JBL/Selenium ST400BLK 8 Ohm bullet supertweeter, which provides wonderful performance, and is relatively inexpensive. The effect of the supertweeter is to increase the depth, height and width of the sound stage, and, surprisingly, add a delicious nuance to the perceived bass.
Supertweeter Behaviour
It is common to implement a supertweeter by connecting the supertweeter in parallel with the tweeter, and blocking the supertweeter with a capacitor that puts the supertweeter about 3 dB down at 10 kHz. Surprisingly, I had not in my 65 years of audio seen a treatise on how the capacitor blocked supertweeter behaves electrically and acoustically; therefore, I did the analysis on the SPICE circuit analysis program. A discussion of the analysis and its results is presented at the following link:
Capacitor Blocked Supertweeter Behaviour, or cut and paste:
http://www.vtaf.com/capacitor-blocked-supertweeter-behaviour.html#/
The conclusion is that the capacitor blocked supertweeter works very well if the supertweeter sensitivity is about the same as the tweeter. These calculations were for a supertweeter implemented with an Altec N800F crossover circuit. At some point I will publish similar results for a crossover implemented with the Hiraga circuit.
Supertweeter Sensitivity vrs. Tweeter Sensitivity
It is typical and important for the tweeter be more sensitive than the woofer. This allows the tweeter sensitivity to be dialed down for compatibility with the woofer sensitivity. Likewise, if the supertweeter sensitivity above 5 kHz is greater than the tweeter sensitivity above 5 kHz, the supertweeter can be dialed down for compatibility with the tweeter. These adjustments are done with the level controls on the crossover front panel. If the supertweeter sensitivity is just a bit too low to get the desired supertweeter effect, it is possible to reduce the tweeter sensitivity at the tweeter terminals by using a power resistor in the hot line to the tweeter, and another power resistor connected across the tweeter terminals, as shown in the image below. Using the correct values for these resistors provides a fixed L-pad local to the tweeter, maintaining tweeter impedance to provide the proper load for the crossover network, while reducing tweeter output. We can go only so far with this. We do not want to reduce tweeter sensitivity so low that we can not dial the tweeter in to a sufficiently high sensitivity to work well with the woofer. Suppose the supertweeter sensitivity is 5 dB lower than the tweeter sensitivity in the band from 5 to 10 kHZ . In this case we could reduce the tweeter sensitivity by 5 or 6 dB and probably still have the tweeter able to play loud enough to work with the woofer. On the other hand, suppose the supertweeter sensitivity is 10 dB lower than the tweeter sensitivity. In this case it may be marginal to be able to reduce tweeter sensitivity to work with both the supertweeter and the woofer.
Two L-pad level controls, labeled "AUDIO LEVEL" are provided. The control on the left adjusts the tweeter level relative to the woofer level.
The control on the right adjusts supertweeter level relative to tweeter level. The supertweeter volume control and the supertweeter are piggy-backed off the tweeter volume control. This causes the supertweeter level to move up and down with the tweeter level.
Supertweeter Effect
On the A7-500 8 Ohm Altec Voice Of The Theatre Speakers of Pete Riggle and Pete's audio wing-man, Stephaen Harrell, the effect of using a capacitor blocked supertweeter is stunning. The supertweeter model we have experience with is the Harman/JBL/Selenium ST400BLK 8 Ohm bullet supertweeter, which provides wonderful performance, and is relatively inexpensive. The effect of the supertweeter is to increase the depth, height and width of the sound stage, and, surprisingly, add a delicious nuance to the perceived bass.
Supertweeter Behaviour
It is common to implement a supertweeter by connecting the supertweeter in parallel with the tweeter, and blocking the supertweeter with a capacitor that puts the supertweeter about 3 dB down at 10 kHz. Surprisingly, I had not in my 65 years of audio seen a treatise on how the capacitor blocked supertweeter behaves electrically and acoustically; therefore, I did the analysis on the SPICE circuit analysis program. A discussion of the analysis and its results is presented at the following link:
Capacitor Blocked Supertweeter Behaviour, or cut and paste:
http://www.vtaf.com/capacitor-blocked-supertweeter-behaviour.html#/
The conclusion is that the capacitor blocked supertweeter works very well if the supertweeter sensitivity is about the same as the tweeter. These calculations were for a supertweeter implemented with an Altec N800F crossover circuit. At some point I will publish similar results for a crossover implemented with the Hiraga circuit.
Supertweeter Sensitivity vrs. Tweeter Sensitivity
It is typical and important for the tweeter be more sensitive than the woofer. This allows the tweeter sensitivity to be dialed down for compatibility with the woofer sensitivity. Likewise, if the supertweeter sensitivity above 5 kHz is greater than the tweeter sensitivity above 5 kHz, the supertweeter can be dialed down for compatibility with the tweeter. These adjustments are done with the level controls on the crossover front panel. If the supertweeter sensitivity is just a bit too low to get the desired supertweeter effect, it is possible to reduce the tweeter sensitivity at the tweeter terminals by using a power resistor in the hot line to the tweeter, and another power resistor connected across the tweeter terminals, as shown in the image below. Using the correct values for these resistors provides a fixed L-pad local to the tweeter, maintaining tweeter impedance to provide the proper load for the crossover network, while reducing tweeter output. We can go only so far with this. We do not want to reduce tweeter sensitivity so low that we can not dial the tweeter in to a sufficiently high sensitivity to work well with the woofer. Suppose the supertweeter sensitivity is 5 dB lower than the tweeter sensitivity in the band from 5 to 10 kHZ . In this case we could reduce the tweeter sensitivity by 5 or 6 dB and probably still have the tweeter able to play loud enough to work with the woofer. On the other hand, suppose the supertweeter sensitivity is 10 dB lower than the tweeter sensitivity. In this case it may be marginal to be able to reduce tweeter sensitivity to work with both the supertweeter and the woofer.
Resistors for attenuation of tweeter sensitivity are listed in the table below. These resistors are for an 8 Ohm tweeter. Double the resistances for a 16 ohm tweeter. We would provide this tweeter attenuation only if we were able to obtain sufficient supertweeter output from a supertweeter we would like to try.
resistor in series resistor in parallel tweeter attenuation, dB
with tweeter, Ohms with tweeter, Ohms
1 60 1.2
2 25 2.5
3 15 4.0
4 8 6.0
5 5 8.4
A Favorite Supertweeter
A favorite supertweeter for me is the Harmon JBL branded Selenium ST400BLk, an 8 Ohm bullet supertweeter, which is a super performer at a price of $140 to $160 USD per pair, shipped to the US, at Parts Experss, Amazon, or ebay. I use these supertweeters with great satisfaction. This supertweeter has sufficient sensitivity to work with a tweeter consisting of the Altec 802-8D compression driver on the Altec 511 horn and with the Altec 416 woofer in an Altec A7-500-8 speaker. See the following photo.
resistor in series resistor in parallel tweeter attenuation, dB
with tweeter, Ohms with tweeter, Ohms
1 60 1.2
2 25 2.5
3 15 4.0
4 8 6.0
5 5 8.4
A Favorite Supertweeter
A favorite supertweeter for me is the Harmon JBL branded Selenium ST400BLk, an 8 Ohm bullet supertweeter, which is a super performer at a price of $140 to $160 USD per pair, shipped to the US, at Parts Experss, Amazon, or ebay. I use these supertweeters with great satisfaction. This supertweeter has sufficient sensitivity to work with a tweeter consisting of the Altec 802-8D compression driver on the Altec 511 horn and with the Altec 416 woofer in an Altec A7-500-8 speaker. See the following photo.
If the user has an exisiting pair of supertweeters and is interested in employing them, please contact Pete Riggle for an evaluation of the mating the supertweeters with Altec tweeters.
Supertweeter Installation on Pete Riggle's Altec A7 Speakers
We currently have been running Harman/JBL/Selenium ST400BLK supertweeters installed with the supertweeter axis 14 inches above the tweeter axis, and located so that the distance of sound travel to the ear from the supertweeter diaphragm is the same as the distance of sound travel from the teeter diaphragm. This puts the back of the supertweeter tweeter unit roughly 1 inch forward of the rear of the tweeter comprssion driver . The mounting arrangement Pete Riggle has been using is shown in photos below. Yes, that is a gray painted brick at the front of the supertweeter sled, placed there to prevent rearward overturning. I should probably move the brick a bit rearward.
Supertweeter Installation on Pete Riggle's Altec A7 Speakers
We currently have been running Harman/JBL/Selenium ST400BLK supertweeters installed with the supertweeter axis 14 inches above the tweeter axis, and located so that the distance of sound travel to the ear from the supertweeter diaphragm is the same as the distance of sound travel from the teeter diaphragm. This puts the back of the supertweeter tweeter unit roughly 1 inch forward of the rear of the tweeter comprssion driver . The mounting arrangement Pete Riggle has been using is shown in photos below. Yes, that is a gray painted brick at the front of the supertweeter sled, placed there to prevent rearward overturning. I should probably move the brick a bit rearward.
Another Supertweeter Mounting Stand
See the photos below for another supertweeter mounting stand designed and built by Pete Riggle for Pete's audio wing man, Stephaen Harrell. Two mounting stands were built in mirror image configuration.
See the photos below for another supertweeter mounting stand designed and built by Pete Riggle for Pete's audio wing man, Stephaen Harrell. Two mounting stands were built in mirror image configuration.
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Another Supertweeter Mounting System
A more simple supertweeter mounting system for A7 speakers is depicted in the sketches shown below. This system currently under construction. The first sketch is a side view. The second sketch is a rear view. What you see is a 3/4" x 17" pine board with a half-circle saddle to ride atop the tweeter compression driver and be clamped to the tweeter compression driver with a 1/2 inch wide 304 stainless steel worm drive hose clamp. These clamps come in kits that have 12 feet of the stainless steel strap and several worm drives. Go to Amazon and search on the words "stainless steel hose clamp assortment kit DIY." The mounting board is braced front to rear with a rigid link connected to a mounting feature on the top of the Altec 511 horn.
It seems likely that we will at some point offer a mounting kit product, possibly 3D printed, for the JBL ST400BLK supertweeter tweeter to be used with Altec 511 horns.
A more simple supertweeter mounting system for A7 speakers is depicted in the sketches shown below. This system currently under construction. The first sketch is a side view. The second sketch is a rear view. What you see is a 3/4" x 17" pine board with a half-circle saddle to ride atop the tweeter compression driver and be clamped to the tweeter compression driver with a 1/2 inch wide 304 stainless steel worm drive hose clamp. These clamps come in kits that have 12 feet of the stainless steel strap and several worm drives. Go to Amazon and search on the words "stainless steel hose clamp assortment kit DIY." The mounting board is braced front to rear with a rigid link connected to a mounting feature on the top of the Altec 511 horn.
It seems likely that we will at some point offer a mounting kit product, possibly 3D printed, for the JBL ST400BLK supertweeter tweeter to be used with Altec 511 horns.
Just in case we haven't beaten a dead horse . . . Paul Slad's supertweeter instlallation: Below please see a supertweeter installation by Paul Slad, one of our crossover customers. This is a JBL model 175 tweeter. Another inventive mounting approach.
Circuit Diagram; 8 Ohm Hiraga Crossover with Supertweeter Circuit
Important Note: The circuit diagram below shows the supertweeter piggy-backed off of the tweeter. The idea behind this arrangement is that the user would adjust the supertweeter relative to the tweeter, after which adjusting the tweeter level would handle the entire treble adjustment. This was a reasonable idea, but I have found that the supertweeter sounds clearer if it is driven directly from the amplifier + input of a single amplifier crossover or driven from the treble amplifier + input of a biampable crossover. Until I make time to publish a modified circuit diagram, here is the change that is needed: Disconnect the supertweeter switch from terminal 2 of the tweeter L-pad and reconnect the switch to the power amplifier + input of the crossover for a single amplifer installation, or to the treble power amplifier + input of a biampable crossover.
Important Note: The circuit diagram below shows the supertweeter piggy-backed off of the tweeter. The idea behind this arrangement is that the user would adjust the supertweeter relative to the tweeter, after which adjusting the tweeter level would handle the entire treble adjustment. This was a reasonable idea, but I have found that the supertweeter sounds clearer if it is driven directly from the amplifier + input of a single amplifier crossover or driven from the treble amplifier + input of a biampable crossover. Until I make time to publish a modified circuit diagram, here is the change that is needed: Disconnect the supertweeter switch from terminal 2 of the tweeter L-pad and reconnect the switch to the power amplifier + input of the crossover for a single amplifer installation, or to the treble power amplifier + input of a biampable crossover.
Pete Riggle Audio
2112 S. Olympia Street, Kennewick, WA, USA
shop phone: 509 582 8419 email: peteriggle@msn.com
VTAF™ Trademarked. U.S.Patent No. 7630288.
Website content Copyright © 2022 Pete Riggle Audio, All Rights Reserved.
2112 S. Olympia Street, Kennewick, WA, USA
shop phone: 509 582 8419 email: peteriggle@msn.com
VTAF™ Trademarked. U.S.Patent No. 7630288.
Website content Copyright © 2022 Pete Riggle Audio, All Rights Reserved.