Owners Manual
Pete Riggle Stand Alone Altec N800F Circuit Crossover
Pete Riggle Stand Alone Altec N800F Circuit Crossover
This manual is for a self contained (not enclosed within the speaker box) version of the Pete Riggle Altec N800 circuit crossover.
The Altec N800F Circuit:
Below is a circuit diagram for the 16 Ohm nominal Altec N800F. In this form of the network the tweeter level is controlled by a rheostat, which is simply a potentiometer with the ability to dissipate a significant amount of power. Although not shown on the circuit, the nominal speaker impedances are 16 Ohms for the woofer and for the tweeter. It is noteworthy that the N800F circuit provides reasonably uniform frequency response for various combinations of 8 and 16 Ohm woofer and tweeter impedances.:
The Altec N800F Circuit:
Below is a circuit diagram for the 16 Ohm nominal Altec N800F. In this form of the network the tweeter level is controlled by a rheostat, which is simply a potentiometer with the ability to dissipate a significant amount of power. Although not shown on the circuit, the nominal speaker impedances are 16 Ohms for the woofer and for the tweeter. It is noteworthy that the N800F circuit provides reasonably uniform frequency response for various combinations of 8 and 16 Ohm woofer and tweeter impedances.:
The following image is the circuit for the L-pad controlled Pete Riggle Altec N800 crossover. Note that I substitute a 5 uF capacitor for the 4 uF specified by Altec, and a 10 uF capacitor for the 10.5 uF capacitor specified by Altec. The calculated crossover electric response curves with the substitutions are slightly better than the response curves with the original values. The 30 Ohm resistor represents the 20 Ohm resistor of the original schematic plus 10 ohms of the 25 Ohm rheostat resistor. The 15 Ohm resistor represents 15 Ohms of the 25 Ohm rheostat resistor. The 16 Ohm L-pad combines with 16 Ohm tweeter to provide a 16 Ohm load on the filter network:
The two images below show a pair of N800F crossover networks with finished front and rear panels and with the optional covers to enclose the electronics. The left image shows the crossovers in the horizontal configuration, without labels. The image to the right shows the same crossovers with laminated labels applied and in the vertical configuration.
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The image below shows the same crossovers with the covers removed to show the internal construction:
The crossovers in the above photos use an early version of optional wood covers. An alternative option for crossover covers is shown in the following photos. This new version of the cover uses 3/4" thick wood side panels that have dados cut at the top and bottom. The intent is to use a smoked acrylic cover to drop into the top of the crossover box. The photos below show a version of the N800F crossover which includes the optional capacitor blocked supertweeter circuit. The circuit includes a 2 uF blocking capacitor, supertweeter output terminals, and a front panel switch that allows the supertweeter to be switched into or out of the circuit.
The photos immediately below show these crossovers with the smoked cast acrylic covers in place. The covers are also available in clear or gloss black cast acrylic.
Using the N800F crossover circuit for speakers with various woofer and tweeter impedances:
Altec used the N800 circuit with the 811 horn for the A7-800 VOT speakers, as well as Valencia, Flamenco, Capistrano, and other speakers with 16 Ohm woofer and tweeter impedance, as well as the Malibu with 8 Ohms woofer impedance and 16 Ohm tweeter impedance.
Altec succesfully used the 16 Ohm N800F crossover with the Malibu speakers which have a 16 ohm tweeter and a pair of Altec 414 12 inch, 16 Ohm woofers connected in parallel, giving a woofer load of 8 Ohms. Response curve simulations of the 16 Ohm N800F circuit with a 16 ohm tweeter and an 8 ohm woofer provide a very satisfactory response curve. The crossover is at 890 Hz, with a broad 2 dB dip centered at 900 Hz.
Altec used the N800 circuit with the 811 horn for the A7-800 VOT speakers, as well as Valencia, Flamenco, Capistrano, and other speakers with 16 Ohm woofer and tweeter impedance, as well as the Malibu with 8 Ohms woofer impedance and 16 Ohm tweeter impedance.
Altec succesfully used the 16 Ohm N800F crossover with the Malibu speakers which have a 16 ohm tweeter and a pair of Altec 414 12 inch, 16 Ohm woofers connected in parallel, giving a woofer load of 8 Ohms. Response curve simulations of the 16 Ohm N800F circuit with a 16 ohm tweeter and an 8 ohm woofer provide a very satisfactory response curve. The crossover is at 890 Hz, with a broad 2 dB dip centered at 900 Hz.
Here are calculated electrical response curves for the Altec N800F circuit 16 Ohm crossover with 16 Ohm resistors representing the woofer and tweeter, using an L-pad for tweeter level control. The first figure below has tweeter set by the L-pad t0 the same sensitivity as the woofer. The second figure below has the tweeter set 4 dB above the woofer. The third figure below has the tweeter set 4 dB below the woofer:
Using the 16 Ohm nominal N800F with mixed woofer and tweeter impedances:
Altec succesfully used the 16 Ohm N800F crossover with the Malibu speakers which have a 16 ohm tweeter and a pair of Altec 414 12 inch,16 Ohm woofers connected in parallel, giving a woofer load of 8 Ohms. Response curve simulations of the 16 Ohm N800F circuit with a 16 ohm tweeter and an 8 ohm woofer provide a very satisfactory response curve. The crossover is at 1 kHz, with a broad 2 dB dip centered at 900 Hz.
Altec's use of the 16 Ohm N800 circuit with an 8 Ohm woofer load and a 16 Ohm tweeter load suggests considering all combinations of 8 and 16 ohm woofers and tweeters with the 16 Ohm N800 circuit. Therefore I did studies which reveal that the 16 Ohm version gives a desirable frequency response with mixed or matched 16 Ohm and 8 Ohm drivers. In all of these cases the response is reasonably flat through the crossover region, with less response curve variation than the 3 dB response variation one would find with a Butterworth second order crossover. This suggests that, although I could provide an 8 Ohm nominal version of these networks, it is not clear that I should. The 8 Ohm nominal version is a bit more expensive to build. At present I offer the 16 Ohm version which works very will with 8 Ohm loads or mixed 8 and 16 Ohm loads.
For a 16 Ohm network loaded with 16 Ohm drivers, or for an 8 Ohm network loaded with 8 Ohm drivers, the crossover point is 1135 Hz, and the response variation is + 1.5 dB.
For a 16 Ohm network loaded with various combinations of 8 and 16 ohm woofers and tweeters the crossover point and response variation are as shown in the following table:
Woofer Tweeter Crossover Point Response Variation
Impedance Impedance
16 16 1135 Hz +1.1/-0.4 dB Valencia Speaker
8 16 890 Hz +0.0/- 2.6 dB Malibu Speaker
8 8 900 Hz +0.0/-2.7 dB
16 8 900 Hz +1.3/-1.2 dB
Altec succesfully used the 16 Ohm N800F crossover with the Malibu speakers which have a 16 ohm tweeter and a pair of Altec 414 12 inch,16 Ohm woofers connected in parallel, giving a woofer load of 8 Ohms. Response curve simulations of the 16 Ohm N800F circuit with a 16 ohm tweeter and an 8 ohm woofer provide a very satisfactory response curve. The crossover is at 1 kHz, with a broad 2 dB dip centered at 900 Hz.
Altec's use of the 16 Ohm N800 circuit with an 8 Ohm woofer load and a 16 Ohm tweeter load suggests considering all combinations of 8 and 16 ohm woofers and tweeters with the 16 Ohm N800 circuit. Therefore I did studies which reveal that the 16 Ohm version gives a desirable frequency response with mixed or matched 16 Ohm and 8 Ohm drivers. In all of these cases the response is reasonably flat through the crossover region, with less response curve variation than the 3 dB response variation one would find with a Butterworth second order crossover. This suggests that, although I could provide an 8 Ohm nominal version of these networks, it is not clear that I should. The 8 Ohm nominal version is a bit more expensive to build. At present I offer the 16 Ohm version which works very will with 8 Ohm loads or mixed 8 and 16 Ohm loads.
For a 16 Ohm network loaded with 16 Ohm drivers, or for an 8 Ohm network loaded with 8 Ohm drivers, the crossover point is 1135 Hz, and the response variation is + 1.5 dB.
For a 16 Ohm network loaded with various combinations of 8 and 16 ohm woofers and tweeters the crossover point and response variation are as shown in the following table:
Woofer Tweeter Crossover Point Response Variation
Impedance Impedance
16 16 1135 Hz +1.1/-0.4 dB Valencia Speaker
8 16 890 Hz +0.0/- 2.6 dB Malibu Speaker
8 8 900 Hz +0.0/-2.7 dB
16 8 900 Hz +1.3/-1.2 dB
Here is the calculated electrical response curve for a 16 Ohm Altec N800F circuit crossover using an L-pad for tweeter level control. This is a special case calculated for the Altec Malibu speaker or other speakers with a 16 Ohm nominal tweeter load and an 8 ohm nominal woofer load. The curves shown below are calculated for the case where the tweeter with its L-pad is set to the same sensitivity as the woofer.
The Effects of Woofer/Tweeter Time Alignment:
The curves presented thus far in this owners manual show the measured on-axis loudspeaker response measurements we would get with a perfect woofer and tweeter located coaxially and time aligned, with no cabinet effects, in an anechoic environment. The N800 is a second order crossover. It is characteristic of second order crossovers that if the woofer and tweeter are time aligned, or spaced with the diaphragms one wave length apart at the crossover frequency, then we need to play the tweeter in reverse phase from the woofer. If the woofer and tweeter are half a wave length apart at the crossover frequency, we would need to play the tweeter in the same phase as the woofer. The crossover is intentionally wired with the tweeter phase reversed from the woofer phase. If the tweeter diaphragm is time aligned with the woofer diaphragm, or at the crossover frequency is one wave length behind the woofer diaphragm, the user should connect the plus (red) terminal of the tweeter to the plus (red) terminal of the crossover. The user should connect the plus (red) terminal of the woofer to the plus (red) terminal of the crossover. Altec speaker designs with horn tweeters tend locate the diaphragms in phase at the crossover frequency (as in the A5 and A7 speakers) or about one wave length apart . For more recent Altec drivers the terminals are marked in red and black, red being the plus terminal and black being the minus terminal. For older Altec drivers the terminals are marked with a 1 and a 2. For woofers 1 is the plus terminal. For compression drivers 2 is the plus terminal. The following figure for a 16 Ohm N800 crossover shows combined responses with the tweeter time aligned and wired with the tweeter in and out of phase. Out of phase is preferred. This is the upper of the two combined response curves.
The curves presented thus far in this owners manual show the measured on-axis loudspeaker response measurements we would get with a perfect woofer and tweeter located coaxially and time aligned, with no cabinet effects, in an anechoic environment. The N800 is a second order crossover. It is characteristic of second order crossovers that if the woofer and tweeter are time aligned, or spaced with the diaphragms one wave length apart at the crossover frequency, then we need to play the tweeter in reverse phase from the woofer. If the woofer and tweeter are half a wave length apart at the crossover frequency, we would need to play the tweeter in the same phase as the woofer. The crossover is intentionally wired with the tweeter phase reversed from the woofer phase. If the tweeter diaphragm is time aligned with the woofer diaphragm, or at the crossover frequency is one wave length behind the woofer diaphragm, the user should connect the plus (red) terminal of the tweeter to the plus (red) terminal of the crossover. The user should connect the plus (red) terminal of the woofer to the plus (red) terminal of the crossover. Altec speaker designs with horn tweeters tend locate the diaphragms in phase at the crossover frequency (as in the A5 and A7 speakers) or about one wave length apart . For more recent Altec drivers the terminals are marked in red and black, red being the plus terminal and black being the minus terminal. For older Altec drivers the terminals are marked with a 1 and a 2. For woofers 1 is the plus terminal. For compression drivers 2 is the plus terminal. The following figure for a 16 Ohm N800 crossover shows combined responses with the tweeter time aligned and wired with the tweeter in and out of phase. Out of phase is preferred. This is the upper of the two combined response curves.
Conclusion:
We wish you many hours of happy listening with your Pete Riggle N800 crossover network. Contact Pete with questions or concerns: email: peteriggle@msn.com telephone: 509 582 4548
We wish you many hours of happy listening with your Pete Riggle N800 crossover network. Contact Pete with questions or concerns: email: peteriggle@msn.com telephone: 509 582 4548
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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.