Comparing Hiraga and Altec 800 N Crossover Circuits
The Hiraga Circuit:
The Hiraga circuit crosses over at 525 Hz. The Altec 800 N circuit crosses over around 980 to 1140 Hz depending on how it is loaded. There is a roughly 1 octave difference in the crossover frequencies. An objective of the Hiraga circuit is to cross over at a fairly low frequency. This objective would be based on the premise that the octave between 500 Hz and 1 kHz will be better served by the tweeter than the woofer. Of course this depends on the chosen woofer and tweeter components.
Hiraga designed his circuit around the Altec A5 speakers with multi-cellular horns going down to about 500 Hz. Hiraga's circuit is acclaimed in this role. So if one is focusing on an A5 application, the Hiraga network is a good choice. Hiraga included a notch filter in his design. The notch filter causes a shallow equalization dip in the electrical response. This dip begins around 800 kHz, reaches a maximum of 4 dB around 3.5 kHz, and rises to the baseline level around 9 kHz. Beyond 9 kHz the response continues to rise, which can help to offset a falling response above 10 or 12 kHz. I would surmise that Hiraga included his equalization dip to compensate for a surplus of sensitivity at the center of the multicellular tweeter midband. In this case the tweeter was an Altec 1505 multicellular horn.
I have adapted the Hiraga network to my Altec A7-500-8 speakers, which use the 511 tweeter horn and the 802-8D compression driver. In my early experience with these speakers, I was using electronic components in my system that could be a bit hard sounding. Hardness is mitigated by the dip provided by the Hiraga circuit. The 4 dB dip of the Hiraga network helped to mitigate the hardness I sometime experienced. I have added switchable adjustments to the Hiraga notch filter allowing the dip to be 0 dB, 2 dB, or 4 dB deep. Recently I have ended up with less hard sounding electronic gear, and possibly more compromised high frequency hearing. I find myself playing the Hiraga crossovers in my system with the switches set to 0 dB. This is an advantage to my configuration of the Hiraga network. The switchable adjustments of the notch filter can be a benefit when taming a system.
For quite a few years now the Hiraga circuit networks have provided wonderful sound with my Altec A7 speakers. These networks will remain in my system for the foreseeable future. However I am also very pleased with the Altec N800 circuit crossovers with the A7 speakers. Therefore, over time, I will be doing extended listening comparisons of the A7 speakers with both the Hiraga circuit crossovers and the Altec N800 circuit crossovers.
The Altec N800 Circuit:
Several years ago I built my version of the 16 Ohm Altec N800 circuit (with L-pad control of tweeter volume) for a pair of Altec Valencias. The results were extremely gratifying. At present I am completing another pair of 16 Ohm nominal N800 circuit crossovers for a customer with Altec Malibu speakers. Because Altec used the N800 circuit in crossovers for a wide range of products, including the 16 Ohm Altec A7 with the 811 horn, I decided upon listening tests with my Altec A7-500 8 Ohm speakers. My goal was to simulate the impedances of Altec Malibu speakers which have two 16 Ohm Altec A14 woofers in parallel for an 8 Ohm woofer load, and have a 16 Ohm tweeter load. Because my A7 speakers are the 8 Ohm version, I placed an 8 Ohm resistor in series with my tweeter, to get a 16 Ohm tweeter load, and drove my A7 speakers through the 16 Ohm nominal N800 circuit crossovers. I am gobsmacked by the results. I had not expected the woofer to be able to handle the octave between 500 Hz and 1 kHz as well as the 511 tweeter horn. The truth is that there is no sense of the woofer being beyond its capabilities up to 1 kHz.
This experience led me to do SPICE calculations of electrical frequency response of the 16 Ohm N800 for all combinations of 8 and 16 Ohm woofer and tweeter loads. All of the resulting response curves are credible.
I very much enjoyed the N800 circuit crossovers with my Altec A7 speakers.
When choosing whether to leave a piece of gear in a system it is wise to play many records over a long time period before reaching a decision. Therefore, in the future I will build a pair of N800 crossovers for extended listening in my system. Only time, quite a bit of time, will tell whether I end up with the Hiraga circuit or the Altec N800 circuit. Both circuits do a great job with the Altec A7 speakers.
The Hiraga Circuit:
The Hiraga circuit crosses over at 525 Hz. The Altec 800 N circuit crosses over around 980 to 1140 Hz depending on how it is loaded. There is a roughly 1 octave difference in the crossover frequencies. An objective of the Hiraga circuit is to cross over at a fairly low frequency. This objective would be based on the premise that the octave between 500 Hz and 1 kHz will be better served by the tweeter than the woofer. Of course this depends on the chosen woofer and tweeter components.
Hiraga designed his circuit around the Altec A5 speakers with multi-cellular horns going down to about 500 Hz. Hiraga's circuit is acclaimed in this role. So if one is focusing on an A5 application, the Hiraga network is a good choice. Hiraga included a notch filter in his design. The notch filter causes a shallow equalization dip in the electrical response. This dip begins around 800 kHz, reaches a maximum of 4 dB around 3.5 kHz, and rises to the baseline level around 9 kHz. Beyond 9 kHz the response continues to rise, which can help to offset a falling response above 10 or 12 kHz. I would surmise that Hiraga included his equalization dip to compensate for a surplus of sensitivity at the center of the multicellular tweeter midband. In this case the tweeter was an Altec 1505 multicellular horn.
I have adapted the Hiraga network to my Altec A7-500-8 speakers, which use the 511 tweeter horn and the 802-8D compression driver. In my early experience with these speakers, I was using electronic components in my system that could be a bit hard sounding. Hardness is mitigated by the dip provided by the Hiraga circuit. The 4 dB dip of the Hiraga network helped to mitigate the hardness I sometime experienced. I have added switchable adjustments to the Hiraga notch filter allowing the dip to be 0 dB, 2 dB, or 4 dB deep. Recently I have ended up with less hard sounding electronic gear, and possibly more compromised high frequency hearing. I find myself playing the Hiraga crossovers in my system with the switches set to 0 dB. This is an advantage to my configuration of the Hiraga network. The switchable adjustments of the notch filter can be a benefit when taming a system.
For quite a few years now the Hiraga circuit networks have provided wonderful sound with my Altec A7 speakers. These networks will remain in my system for the foreseeable future. However I am also very pleased with the Altec N800 circuit crossovers with the A7 speakers. Therefore, over time, I will be doing extended listening comparisons of the A7 speakers with both the Hiraga circuit crossovers and the Altec N800 circuit crossovers.
The Altec N800 Circuit:
Several years ago I built my version of the 16 Ohm Altec N800 circuit (with L-pad control of tweeter volume) for a pair of Altec Valencias. The results were extremely gratifying. At present I am completing another pair of 16 Ohm nominal N800 circuit crossovers for a customer with Altec Malibu speakers. Because Altec used the N800 circuit in crossovers for a wide range of products, including the 16 Ohm Altec A7 with the 811 horn, I decided upon listening tests with my Altec A7-500 8 Ohm speakers. My goal was to simulate the impedances of Altec Malibu speakers which have two 16 Ohm Altec A14 woofers in parallel for an 8 Ohm woofer load, and have a 16 Ohm tweeter load. Because my A7 speakers are the 8 Ohm version, I placed an 8 Ohm resistor in series with my tweeter, to get a 16 Ohm tweeter load, and drove my A7 speakers through the 16 Ohm nominal N800 circuit crossovers. I am gobsmacked by the results. I had not expected the woofer to be able to handle the octave between 500 Hz and 1 kHz as well as the 511 tweeter horn. The truth is that there is no sense of the woofer being beyond its capabilities up to 1 kHz.
This experience led me to do SPICE calculations of electrical frequency response of the 16 Ohm N800 for all combinations of 8 and 16 Ohm woofer and tweeter loads. All of the resulting response curves are credible.
I very much enjoyed the N800 circuit crossovers with my Altec A7 speakers.
When choosing whether to leave a piece of gear in a system it is wise to play many records over a long time period before reaching a decision. Therefore, in the future I will build a pair of N800 crossovers for extended listening in my system. Only time, quite a bit of time, will tell whether I end up with the Hiraga circuit or the Altec N800 circuit. Both circuits do a great job with the Altec A7 speakers.
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Pete Riggle Audio
2112 S. Olympia Street, Kennewick WA 99337, USA
shop phone: 509 582 4548 email: peteriggle@msn.com
VTAF™ Trademarked. U.S.Patent No. 7630288.
Website content Copyright © 2021 Pete Riggle Audio, All Rights Reserved.
Pete Riggle Audio
2112 S. Olympia Street, Kennewick WA 99337, USA
shop phone: 509 582 4548 email: peteriggle@msn.com
VTAF™ Trademarked. U.S.Patent No. 7630288.
Website content Copyright © 2021 Pete Riggle Audio, All Rights Reserved.