I'm planning a build for both a 3way speakers system with active crossovers and the amplifier. Now I need some help with the basic thinking.
With a passive crossover you match the drivers to the input with all kinds of messy ways to level the db/impedance differences. Now with an active crossover setup you don't waste any wattage. What the amplifier send to the drivers goes straight into them. So if a driver has a max of 80watts, I can't feed it any more than that. But how do you get the three drivers on the same db? So my list of drivers I want to use is this:
All from SB acoustics
So not to blow up the drivers the max I should use for the mid and the tweeter is 70watt. But the tweeter would be 4db louder.
The active analog crossovers I want to use do have adjustable gain of -9dB to +8dB (https://sublimeacoustic.com/products/k231-stereo-3-way-active-crossover)
So that would fix the mid/tweeter mismatch
The difference between bass and the rest is roughly 50%
Closest I came is with ice power:
Twice/4 channels mid/high
ICEpower 80AM2 2 x 80watt @ 4 ohm
https://www.soundimports.eu/nl/icepower-80am2.html
https://shop.icepoweraudio.com/product/80am2/
(edit: two extra ICEpower 80AM2 for the bass in mono 80watt @ 8ohm
so 4 the same modules, 2 in stereo, two in mono creates 6 channels with very close SPL results, enough to fine tune with attenuation)
Once/2 channels Bass
ICEpower 100AS2 2 x 100watt @ 4 ohm / 50 watt @ 8 ohm = 75 watt @ 6 ohm (5 watt short/mismatch)
https://www.soundimports.eu/nl/icepower-100as2.html
https://shop.icepoweraudio.com/product/100as2/
I'm going to do both digital and analog pathways, so the digital pathway could fix all this with the input, but I think I should get it as close as possible,
Am I all thinking wrong about this issue? Any tips?
With a passive crossover you match the drivers to the input with all kinds of messy ways to level the db/impedance differences. Now with an active crossover setup you don't waste any wattage. What the amplifier send to the drivers goes straight into them. So if a driver has a max of 80watts, I can't feed it any more than that. But how do you get the three drivers on the same db? So my list of drivers I want to use is this:
All from SB acoustics
- Tweeter TW29BNWG-4 4ohm max 80watt 97db
- Midwoofer MW19TX-4 4ohm max 70watt 93db
Basswoofer SB42FHCL75-6 6ohm max 300watt 93db(edit found an 8 ohm which is exact double so I can use the amp modules in mono and they will match closer: SB34NRXL75-8 8ohm max 200watt 91db)
So not to blow up the drivers the max I should use for the mid and the tweeter is 70watt. But the tweeter would be 4db louder.
The active analog crossovers I want to use do have adjustable gain of -9dB to +8dB (https://sublimeacoustic.com/products/k231-stereo-3-way-active-crossover)
So that would fix the mid/tweeter mismatch
Closest I came is with ice power:
Twice/4 channels mid/high
ICEpower 80AM2 2 x 80watt @ 4 ohm
https://www.soundimports.eu/nl/icepower-80am2.html
https://shop.icepoweraudio.com/product/80am2/
(edit: two extra ICEpower 80AM2 for the bass in mono 80watt @ 8ohm
so 4 the same modules, 2 in stereo, two in mono creates 6 channels with very close SPL results, enough to fine tune with attenuation)
ICEpower 100AS2 2 x 100watt @ 4 ohm / 50 watt @ 8 ohm = 75 watt @ 6 ohm (5 watt short/mismatch)
https://www.soundimports.eu/nl/icepower-100as2.html
I'm going to do both digital and analog pathways, so the digital pathway could fix all this with the input, but I think I should get it as close as possible,
Am I all thinking wrong about this issue? Any tips?
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I have a 3-way 6-channel stereo and it's rather easy to setup with a DSP crossover.
In my case, the three-way consists of hybrid ESL speakers and a pair of Ripol subs, all driven by three Carver TFM-25 amps. The woofer is a pro model with much higher efficiency than the stat panel but it's not necessary that they match-- the DSP takes care of that with the channel gains.
The hybrid ESLs are vertically bi-amp'd (woofer on left channel & stat panel on right channel of same amp).
The two subs are horizontally driven by the third amp.
The crossover is a DBX Driverack Venu 360 (the PA2 model is good too), with microphone. The interface is an app loaded on my iPad. All adjustments and tuning can be done in real time from my listening position.
The first step is setting the crossover filter type, frequencies and slopes (very easy from the menu).
In my ESLs the panel is physically about 3" forward of the woofer's voice coil so my next step is time-aligning the woofer and stat panel by applying a 0.3ms delay on the panel. I determine the delay precisely by feeding in a sine-wave test tone matching the crossover frequency, and then I adjust the delay on the panel until the RTA screen shows max SPL (i.e. max constructive interference).
The third step is adjusting the channel gains. This is quite easy: Feed in pink noise and adjust the (3) crossover gains up or down until they all show approximately the same SPL on the RTA screen.
I then select the Auto EQ tab and choose one of the reference response curves from the menu (flat, bass shelf, or treble shelf). A diagram pops up on the screen to show where to place the microphone for each of three frequency sweeps. Hit the "Start" tab and the Auto EQ does a frequency sweep. The Wizard does two more frequency sweeps and then computes the results.
Following the frequency sweeps, the Auto EQ automatically overlays multiple parametric EQ's to match the response to the pre-selected reference curve.
I do the final tuning by ear using the 31 band graphic EQ. ESLs can be a bit harsh, so I first play the tune "Holiday" by Erin Bode to test for harshness. Erin has a clear piercing voice that will cut diamond if the system is tuned hot. Typically; applying a -3db cut at about 3kHz (a.k.a. the "Gundry dip") will take the edge off Erin's voice. After that, nothing else I'm likely to play will sound harsh. I then follow up with Dave Brubeck's "Take Five"-- and if Morello's high hat is still crisp, then I know I haven't taken too much off.
It may sound complicated but the Driverack's interface is so intuitive and simple, it's all rather easy and takes less than 30 minutes to get the setup and tuning perfect.
I'm so spoiled now, I would never go back to passive crossovers again.
In my case, the three-way consists of hybrid ESL speakers and a pair of Ripol subs, all driven by three Carver TFM-25 amps. The woofer is a pro model with much higher efficiency than the stat panel but it's not necessary that they match-- the DSP takes care of that with the channel gains.
The hybrid ESLs are vertically bi-amp'd (woofer on left channel & stat panel on right channel of same amp).
The two subs are horizontally driven by the third amp.
The crossover is a DBX Driverack Venu 360 (the PA2 model is good too), with microphone. The interface is an app loaded on my iPad. All adjustments and tuning can be done in real time from my listening position.
The first step is setting the crossover filter type, frequencies and slopes (very easy from the menu).
In my ESLs the panel is physically about 3" forward of the woofer's voice coil so my next step is time-aligning the woofer and stat panel by applying a 0.3ms delay on the panel. I determine the delay precisely by feeding in a sine-wave test tone matching the crossover frequency, and then I adjust the delay on the panel until the RTA screen shows max SPL (i.e. max constructive interference).
The third step is adjusting the channel gains. This is quite easy: Feed in pink noise and adjust the (3) crossover gains up or down until they all show approximately the same SPL on the RTA screen.
I then select the Auto EQ tab and choose one of the reference response curves from the menu (flat, bass shelf, or treble shelf). A diagram pops up on the screen to show where to place the microphone for each of three frequency sweeps. Hit the "Start" tab and the Auto EQ does a frequency sweep. The Wizard does two more frequency sweeps and then computes the results.
Following the frequency sweeps, the Auto EQ automatically overlays multiple parametric EQ's to match the response to the pre-selected reference curve.
I do the final tuning by ear using the 31 band graphic EQ. ESLs can be a bit harsh, so I first play the tune "Holiday" by Erin Bode to test for harshness. Erin has a clear piercing voice that will cut diamond if the system is tuned hot. Typically; applying a -3db cut at about 3kHz (a.k.a. the "Gundry dip") will take the edge off Erin's voice. After that, nothing else I'm likely to play will sound harsh. I then follow up with Dave Brubeck's "Take Five"-- and if Morello's high hat is still crisp, then I know I haven't taken too much off.
It may sound complicated but the Driverack's interface is so intuitive and simple, it's all rather easy and takes less than 30 minutes to get the setup and tuning perfect.
I'm so spoiled now, I would never go back to passive crossovers again.
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You'd need to consider the gain of the entire signal chain that is, preamplifier/processor and power amplifier included.
You need to match up SPL, not electrical power into the three units. And level matching is carried out by adding attenuation (minus dB) to the more efficient sections as opposed to adding gain to the less efficient ones. Thus, your overall SPL would be that of the least efficient of the three sections, usually, the LF woofer.
The power on the tweeter is not very important as most of the energy resides at lower frequencies that is, less than 300-400Hz.
That unit translates an analog signal do digital, dsp processes it and translates it back to analog. That's not the way I want to go! I do appreciate your explanation though!! And I probably can use some of it if I set up the digital path way. That doesn't need external hardware beside the 8 channel topping dac since you can do the crossover within software linked to Roon. For the analog crossover I still need to match the amps in some way
As for the SPL story, yes I understand.
"You'd need to consider the gain of the entire signal chain that is, preamplifier/processor and power amplifier included." well the signal at preamplifier/processor level is still balanced in all frequencies. The power amplifier I'm building, so that's where my question is at.
I understand it's about spl. But spl is the result of all the info I gave right? Isn't your target db?
Db sensitivity, wattage, amperage. So I still need to find amplifier modules which kind of roughly level out so I can fine tune with attenuation. The crossover has attenuation for a max of -9db.
"You'd need to consider the gain of the entire signal chain that is, preamplifier/processor and power amplifier included." well the signal at preamplifier/processor level is still balanced in all frequencies. The power amplifier I'm building, so that's where my question is at.
I understand it's about spl. But spl is the result of all the info I gave right? Isn't your target db?
Db sensitivity, wattage, amperage. So I still need to find amplifier modules which kind of roughly level out so I can fine tune with attenuation. The crossover has attenuation for a max of -9db.
I think the easiest way is to use identical amps for all the channels. Then you know they all have the same gain and sound quality.
And you mentioned, the XO has +8 dB to -9 dB of adjustment on all channels, which is 17 dB of range, plenty of room to match the driver levels.
I've built two similar systems with my own multi channels amps and the ART CX311 analog active XOs. They can be a bit challenging to dial-in for both the best XO frequencies and the levels, but well worth the effort.
And you mentioned, the XO has +8 dB to -9 dB of adjustment on all channels, which is 17 dB of range, plenty of room to match the driver levels.
I've built two similar systems with my own multi channels amps and the ART CX311 analog active XOs. They can be a bit challenging to dial-in for both the best XO frequencies and the levels, but well worth the effort.
This is a very informative thread. I have heard of Roon but I'm not read-up on it and had no idea it had crossover capabilities.
I too was concerned about having multiple AD & DA conversions in the signal path, so omitted the analog preamp and I'm streaming Tidal high-res directly from a Logitech Transporter into the DBX Venu 360's AES digital input.
The Transporter's digital preamp uses about 2bits of its 24bit resolution for volume control, but it's still higher res than a 16bit CD. Omitting the analog preamp eliminated one D/A and one A/D conversion, and leaves just one D/A conversion in the signal path, coming out of the DSP.
I don't know whether I would have heard a significant difference anyway, but I do like the idea of having just one conversion in the signal path. The downside is that the Transporter has no inputs for a turntable or TV connection, but I can live with that.
The Transporter hasn't been produced in many years and it's no longer supported so I wouldn't recommend it over newer streamers-- but I LOVE mine. It's still a very high quality device and I have a spare.
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"I'm streaming Tidal high-res directly from a Logitech Transporter into the DBX Venu 360's AES digital input" that sounds good!
The crossover is not exactly in Roon itself, but either as an extension or just in windows. I'm not there yet. Either way, no need for extra hardware on that side. My Roon uses Tidal, so it's pretty much similar.
Thing is I don't want to change my plans on that side. Just looking for amp boards which kind of match up. I just find it odd that all these drivers have differences, even if you go for 1 brand, but there is no way to finetune the amp boards for an active three way. Or dedicated amp board for that situation. I started to see how passive crossover worked and I do not ever want o build anything with that, what a mess.
The crossover is not exactly in Roon itself, but either as an extension or just in windows. I'm not there yet. Either way, no need for extra hardware on that side. My Roon uses Tidal, so it's pretty much similar.
Thing is I don't want to change my plans on that side. Just looking for amp boards which kind of match up. I just find it odd that all these drivers have differences, even if you go for 1 brand, but there is no way to finetune the amp boards for an active three way. Or dedicated amp board for that situation. I started to see how passive crossover worked and I do not ever want o build anything with that, what a mess.
Which amp board did you use?
All the same wouldn;t work if two are 4 ohm and one is 6 ohm. So you think it's wise to look for a 4 ohm bass woofer and keep them all the same?
No. There are advantages to keeping a reasonable gain structure (where and how much gain and attenuation you use), but first you want to know how it works. The details can come later. An example would be that if you use much attenuation or you put it in the wrong place, the small signal falls closer to the noise floor. If you have a problem with that you'll know and can do something about it.
The amp is an 8 channel of my own design using the Apex Microtechnology PA12 power opamp chip, which you can see at the link below.
https://www.diyaudio.com/community/threads/chip-amp-photo-gallery.79303/post-6664855
My subs are 4 ohm, mids and tweeters are 8 ohm and I have no trouble matching levels.
Certainly wouldn't hurt to have all drivers the same impedance but I don't think you'll have trouble with what you have.
Driver impedance is a nominal value and varies with frequency anyway. It's not really an issue with active crossovers since you have a direct amp-to-driver connections.
You could work back from the output to the input. For example, you need a target SPL of 75dB at 4 metres (LP). With a 93dB/W/m woofer, this would require 0.25W. However, assuming a 20dB crest factor, the peak power could go up to 25W.
Now, 0.25W into 4, 6 and 8 ohms require 1V, 1.25V and 1.414V respectively (RMS). For peak SPL conditions, multiply the voltage by 10 (for 20dB peaks) to get 10V, 12.5V and 14.14V respectively (RMS). Multiply by another 1.414 to get the peak amplifier voltage. Also use this voltage swing to calculate the power supply rails for the amplifier, after adding a reasonable margin to it.
Assuming your analogue signal has a 2V peak, you could calculate the required minimum gain of the power amplifier as 7, 8.8 and 10 V/V respectively for 4, 6 and 8 ohms. However, if only a minimum gain of 20V/V is possible (due to stability margins or whatever) you could easily drop a few dB on your processor to get back without any problems.
Modify the above example for your distance, SPL etc. to get a rough idea of the amplifier power and gain required. Remember that you also need to allow some headroom for equalisation etc.
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@raymondvanmil , I have a multichannel amplifier setup similar to what you are considering. The amplifier boards have different Pmax and Gain and different power supply voltages. My drivers have different impedances, different sensitivity, and different Pmax. It's all good. Everything can be adjusted to have the same sensitivity (SPL/volt) using either a) input attenuators at the amp, or b) output attenuators in the DAC. Some DACs have a built in digitally controlled analog volume pot, otherwise one can be placed at the input of the amplifier. I adjust the line level attenuation to equalize the sensitivity as measured by a mic, then apply the DSP filters and corrections to each channel. Pics at Amplifier .
I built 3 way active speakers with 2 woofers and used 4 identical amplifiers, thereby giving the low frequencies double the available power. The advantage here is that a single power supply feeds all the amplifiers saving cost and space. In practice of course the tweeter amp is rather over provisioned but it makes my configuration nice and simple and the level is correctly controlled by the trimmer in the crossover.
I used an analog crossover from Rod Elliot and this has trimmers to allow for adjustment for the sensitivity of the various drive units.
I used a measurement mic and REW to set the levels evenly by using single test tones within the pass band of each driver and then confirming with a sweep that I hadn’t equalized on a driver peak.
I would recommend that you get a microphone and software and then you can be sure that you are getting the right levels from your drive units and there is no guesswork or miscalculation.
Hifi Jim has a great thread going on a 3 way compact active speaker design and there are lots of very useful tips in that thread, well worth a read.
I used an analog crossover from Rod Elliot and this has trimmers to allow for adjustment for the sensitivity of the various drive units.
I used a measurement mic and REW to set the levels evenly by using single test tones within the pass band of each driver and then confirming with a sweep that I hadn’t equalized on a driver peak.
I would recommend that you get a microphone and software and then you can be sure that you are getting the right levels from your drive units and there is no guesswork or miscalculation.
Hifi Jim has a great thread going on a 3 way compact active speaker design and there are lots of very useful tips in that thread, well worth a read.
Not really. They're nice for sub woofers maybe, not what I'm looking for. A plate amp on a tweeter?
Thank you! This is what I will do. I just figured out bass woofers with exact the double amperage who I can give the same amp module in mono. So it will all match up almost perfect give or take 2 db. And indeed just an need for one power board... Will look into the Rod version, is it this one? https://sound-au.com/project148.htm
This went over my head. Why not use the listed SPL for the drivers? They're listen @ 1 meter, which is most of the time my distance since they will be on rolling platforms as my current speakers are. They are all within a 2 db range now. I'll have to measure to fine tune.