I would try a coax from Sica instead of a full-ranger, but the BMR is not a bad choice either (though it seems to divide people a lot).
You might also consider some small "subwoofers" instead of the SB drivers, depending on your goals
Creating a passive 300 Hz 2nd order crossover is possible, but of course it will require large inductor and capacitor values. Since you will not be using DSP, you will need a larger volume for the woofer, and it probably needs to be a vented enclosure. This woofer is not the ideal candidate for closed box design, unless DSP is used to adjust the bass response. For a vented box, I would start with a 30 l box tuned to 32 Hz. Another thing you need to consider is voicing: My passive crossover design (from mid to tweeter) contains very little response shaping, or voicing. I intend to tailor the response using DSP. In an all passive design, you will need to properly account for the baffle step in both the woofer and midrange, and properly adjust the tweeter level. My passive crossover can serve as a starting point, but if you try to use it directly, you may be disappointed.
Well, it is not done yet, so we don't really know if it is fabulous. It could turn out to be a failure. But the sims look really good so far...
I have made a lot of progress in the last two weeks. I made several sets of polar frequency response scans, each one with more resolution and a lower noise floor. For the final set of measurements, I was able to elevate the system quite high and get 5.5 ms gate window. I am quite proud of that, since I have never been able to get such a long gate before.
I connected the passive crossover components together, and tested the midrange and tweeter to make sure that the frequency response and impedance matches expectations (i.e. VituixCad simulation). I did this with the woofer removed so I had access to the wiring.
I assembled and installed the passive crossovers, and completed final assembly of the speakers. I have loaded the developmental preliminary DSP filter into the MiniDSP 2x4HD, and completed the frequency response testing to ensure that everything went together smoothly and the simulation matches the measured response.
My concerns about not meeting the bass extension target turned out to be no concern at all. Based on nearfield scans, I have an F3 of 38 Hz, and an F6 of 30 Hz.
After some initial listening, I made a small refinement in the region above 10k. Other than that, I am pleasantly surprised to find my initial attempt at the DSP filter sounds so good. I will listen for a couple of weeks and make refinements as I go.
I connected the passive crossover components together, and tested the midrange and tweeter to make sure that the frequency response and impedance matches expectations (i.e. VituixCad simulation). I did this with the woofer removed so I had access to the wiring.
I assembled and installed the passive crossovers, and completed final assembly of the speakers. I have loaded the developmental preliminary DSP filter into the MiniDSP 2x4HD, and completed the frequency response testing to ensure that everything went together smoothly and the simulation matches the measured response.
My concerns about not meeting the bass extension target turned out to be no concern at all. Based on nearfield scans, I have an F3 of 38 Hz, and an F6 of 30 Hz.
After some initial listening, I made a small refinement in the region above 10k. Other than that, I am pleasantly surprised to find my initial attempt at the DSP filter sounds so good. I will listen for a couple of weeks and make refinements as I go.
This is the first test of harmonic distortion. I used STEPS software with 24 data samples per octave. The distance was 12 inches, and the SPL was 90 dB. This translates to about 85 dB SPL at 1 m, so the level was not very high. I plan to repeat the test at a higher SPL later on. Still, I am pleased with the low level of distortion.
This is how I integrated the 2-channel amp into the speaker. I chose a KISS (Keep It Simple Stupid) approach which will hopefully make future maintenance or upgrades easy.
There is a pair of wires for the woofer, and a pair of wires for the mid-tweeter crossover which exit the back of the speaker through a hole. I packed the hole with foam. The wires lead to a ring terminal strip. The output of the amp also connects with ring terminals to the strip.
The amp is attached to the back of the amp with cable ties.
I have come to appreciate handles on any speaker which needs to get moved around a lot, so I put a simple handle on the back of this one. I might put some feet on the back so that the speaker can be laid down on its back without the weight being on the amp.
j.
There is a pair of wires for the woofer, and a pair of wires for the mid-tweeter crossover which exit the back of the speaker through a hole. I packed the hole with foam. The wires lead to a ring terminal strip. The output of the amp also connects with ring terminals to the strip.
The amp is attached to the back of the amp with cable ties.
I have come to appreciate handles on any speaker which needs to get moved around a lot, so I put a simple handle on the back of this one. I might put some feet on the back so that the speaker can be laid down on its back without the weight being on the amp.
j.
For the past several days, I have been doing an extended comparison with the TXT system. The TXT is the best wide-directivity, non-waveguide speaker I have, so it is a good basis of comparison to this LCCAM. I matched levels between the two systems with pink noise using an SPL meter.
My conclusion is that LCCAM is a very good speaker. It has excellent detail and clarity, and a smooth but detailed top end. Trumpet, sax, electric guitar, female vocals are very well portrayed. Bass is punchy and effortless, with drive and pace. Kick drum and electric bass sound dynamic and tight. String bass, bass clarinet, tuba, baritone and bass male vocals have detail and nuance. Piano sounds very good.
Compared to the TXT system, the LCCAM does nothing wrong. The TXT has just slightly more low level detail in the midrange, and this lets most instruments and vocals come through in a slightly more natural way, but this is only noticeable with a direct comparison and concentrated listening. The TXT has slightly better sense of space and depth. Percussive sounds, such as cymbals and tambourine, sounded more natural. I noticed it first on tracks where a brush was gently used on snare drum and cymbals. Once I learned what to listen for, I could hear a slight difference in how sounds decayed. Woodwinds had more air flowing through them. It was easier to hear the differences between acoustic guitars with the TXT. The TXT revealed the small echoes of the studio or hall in a more natural way. All these differences are very subtle, and were only revealed to me by listening to the same 60 seconds of music over and over again on each system… which is not exactly a natural way to listen to music.
If I compare the costs of the two systems, it is rather striking. Using 2023 prices, the TXT system would cost $2986 for drivers and electronics. This does not include the cabinets. The LCCAM system cost for drivers and electronics is $1041, again not including the cost of the cabinet. So, the LCCAM gets very close to the performance of the TXT system for about 1/3 the cost, and in a substantially smaller package. If I had included that cabinet costs, the difference would have been greater.
I am quite pleased with this Low Cost Compact Active Monitor. I met all my performance goals, and it sounds great.
My conclusion is that LCCAM is a very good speaker. It has excellent detail and clarity, and a smooth but detailed top end. Trumpet, sax, electric guitar, female vocals are very well portrayed. Bass is punchy and effortless, with drive and pace. Kick drum and electric bass sound dynamic and tight. String bass, bass clarinet, tuba, baritone and bass male vocals have detail and nuance. Piano sounds very good.
Compared to the TXT system, the LCCAM does nothing wrong. The TXT has just slightly more low level detail in the midrange, and this lets most instruments and vocals come through in a slightly more natural way, but this is only noticeable with a direct comparison and concentrated listening. The TXT has slightly better sense of space and depth. Percussive sounds, such as cymbals and tambourine, sounded more natural. I noticed it first on tracks where a brush was gently used on snare drum and cymbals. Once I learned what to listen for, I could hear a slight difference in how sounds decayed. Woodwinds had more air flowing through them. It was easier to hear the differences between acoustic guitars with the TXT. The TXT revealed the small echoes of the studio or hall in a more natural way. All these differences are very subtle, and were only revealed to me by listening to the same 60 seconds of music over and over again on each system… which is not exactly a natural way to listen to music.
If I compare the costs of the two systems, it is rather striking. Using 2023 prices, the TXT system would cost $2986 for drivers and electronics. This does not include the cabinets. The LCCAM system cost for drivers and electronics is $1041, again not including the cost of the cabinet. So, the LCCAM gets very close to the performance of the TXT system for about 1/3 the cost, and in a substantially smaller package. If I had included that cabinet costs, the difference would have been greater.
I am quite pleased with this Low Cost Compact Active Monitor. I met all my performance goals, and it sounds great.
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Thanks for the comments!
From the outset, I wanted this to be an active speaker, with DSP capabilities. I am a fan of sealed box bass alignment, especially when enhanced with a Linkwitz Transform, and with DSP, this is easily enabled. Although I do not currently use a room correction software such as Dirac or REW, many people do, and this requires DSP.
The options for 3-channel DSP with 3-channel amplification are rather expensive. I have used Hypex on my previous projects, and it is a great product. It is also $1100 for the entry level FA123 (pair). The cost of the Hypex is a barrier for some of my friends who would like to build a system. This project was meant as something they could copy.
Generic 2-channel class D amps are readily available, and a real bargain. The MiniDSP 2x4HD unit is also a bargain, with 2-in, 4-out capability. The availability of both of these drove my decision to make a 3-way speaker with a passive crossover between mid-tweeter.
Over the summer I built a small 2-way passive speaker, and I was reminded once again of the slow painful process to make small voicing adjustments to a passive speaker. Considering that, I don't think I would ever do a passive 3-way again. 2-ways, yes. 3-ways, no.
A passive 3-way crossover at 300 + 2.5k would probably cost $250/pair. In comparison, the cost of the MiniDSP and the passive 2-way crossover was $335. For the small extra cost, I get a lot of extra capability.
From the outset, I wanted this to be an active speaker, with DSP capabilities. I am a fan of sealed box bass alignment, especially when enhanced with a Linkwitz Transform, and with DSP, this is easily enabled. Although I do not currently use a room correction software such as Dirac or REW, many people do, and this requires DSP.
The options for 3-channel DSP with 3-channel amplification are rather expensive. I have used Hypex on my previous projects, and it is a great product. It is also $1100 for the entry level FA123 (pair). The cost of the Hypex is a barrier for some of my friends who would like to build a system. This project was meant as something they could copy.
Generic 2-channel class D amps are readily available, and a real bargain. The MiniDSP 2x4HD unit is also a bargain, with 2-in, 4-out capability. The availability of both of these drove my decision to make a 3-way speaker with a passive crossover between mid-tweeter.
Over the summer I built a small 2-way passive speaker, and I was reminded once again of the slow painful process to make small voicing adjustments to a passive speaker. Considering that, I don't think I would ever do a passive 3-way again. 2-ways, yes. 3-ways, no.
A passive 3-way crossover at 300 + 2.5k would probably cost $250/pair. In comparison, the cost of the MiniDSP and the passive 2-way crossover was $335. For the small extra cost, I get a lot of extra capability.
Great reasons for your choice.
A long time ago, I got two 2x4 miniDSP and was using one per channel for an active speaker. This was cost effective at $79 for each 4Ch miniDSP and two TPA3116 Class D amps. Could be up to 4 ways. The biggest pain was having to upload the settings twice to two separate DSP flash memories.
I have also built a pro audio speaker with a passive 2 way for the pole mounted tops (GRS planar and 6F100) and the sub used the other 3 channels since it needed delay between the drivers. That worked out well too.
A long time ago, I got two 2x4 miniDSP and was using one per channel for an active speaker. This was cost effective at $79 for each 4Ch miniDSP and two TPA3116 Class D amps. Could be up to 4 ways. The biggest pain was having to upload the settings twice to two separate DSP flash memories.
I have also built a pro audio speaker with a passive 2 way for the pole mounted tops (GRS planar and 6F100) and the sub used the other 3 channels since it needed delay between the drivers. That worked out well too.
Jim> how does the SB26STAC compare to other soft domes that you have heard? I'm trying to decide on using that or maybe the Scanspeak 8330 for a project. Unlike many people, I don't find silk domes "soft" necessarily, in fact when I've compared a tweeter family that had several diaphragm materials it was always the soft dome that ended being the one that misbehaved most with a little too much "sizzle".
Thanks for the comments !
The closest comparable tweeter I have recent experience with is the SB26CDC. I have used it a lot, and I like it. I would say the SB26STAC is very similar in sound quality. As far as I know they have the same motor, so it is not surprising they have a consistent sound.
It is important to remember that I use DSP EQ to make tweeters flat... This may be one reason I find the two SB tweeters so similar in sound.
According to the simulation, we hit Xmax at 40 Hz with a drive level of 12 Vrms, with an SPL of 98 dB. So your proposed amp would work. It does not leave a lot of headroom for all the music above 40 Hz, but it does offer some nice advantages.
I wish I had a basis of comparison for you. This is the first soft dome I have worked with in many years. The last one was a Vifa D27TG-35, more than 20 years ago.
The closest comparable tweeter I have recent experience with is the SB26CDC. I have used it a lot, and I like it. I would say the SB26STAC is very similar in sound quality. As far as I know they have the same motor, so it is not surprising they have a consistent sound.
It is important to remember that I use DSP EQ to make tweeters flat... This may be one reason I find the two SB tweeters so similar in sound.
Good day. You've done a great job, your approach to designing speakers is impressive. I myself have an active three-way speaker system with DSP, and I tuned it using a microphone, making adjustments to achieve a more acceptable frequency response in the listening area. Active speakers are a powerful tool, especially if you understand how to use a microphone. There are many advantages to active speakers, and after I set up mine and listened to it, I have no desire to go back to passive crossover systems.
Since you have many acquaintances interested in building active speakers, I'm curious to know the answer to one question.
In your opinion, how important is the presence of an analog input for active speakers in today's context?
Since you have many acquaintances interested in building active speakers, I'm curious to know the answer to one question.
In your opinion, how important is the presence of an analog input for active speakers in today's context?
That is a good question... It is important to me, mostly due to inertia, and my own reluctance to make the switch to all digital, all the time. I like having an analog volume control.
With the MiniDSP 2x4HD, it is easy to use a USB cable to provide it with 24 bit/96k data, and let the device be the DAC and the DSP. For now, I have been using a separate DAC, and feeding the MiniDSP an analog signal. That may change in the future.
With my other active systems which are based on Hypex FA253 DSP amps, I was not happy with the implementation of digital interface and setup, so I chose to feed the hypex with an analog signal.
With the MiniDSP 2x4HD, it is easy to use a USB cable to provide it with 24 bit/96k data, and let the device be the DAC and the DSP. For now, I have been using a separate DAC, and feeding the MiniDSP an analog signal. That may change in the future.
With my other active systems which are based on Hypex FA253 DSP amps, I was not happy with the implementation of digital interface and setup, so I chose to feed the hypex with an analog signal.
Can you provide more details on what exactly is inconvenient about their digital volume control interface? I haven't dealt with their modules, but as I understand, they have an additional module for remote volume control...
I hope discussing such issues in this thread is not considered off-topic? There is always some challenge in adjusting the volume in active speakers, especially when everything is installed inside the speaker, and the sound is transmitted through the air.
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One thing I would like to see on the Hypex plate amps is a USB input for digital signals. The only options are S/PDIF, or optical, or an XLR connector. That is a bit inconvenient for me with the way I would run my server.
I like the tactile feel of a volume control knob. Hard to explain, but it is my preference.
I like the tactile feel of a volume control knob. Hard to explain, but it is my preference.
Just as sidenote, I as well use only analog input with my actives using Hypex or minidsp. Dsp and amps have power on 24/7.
I use various sources and some kind of preamp as source switch and volume control. This make the whole system easier to use for the family, and I have no problems with hum and noise.
I use various sources and some kind of preamp as source switch and volume control. This make the whole system easier to use for the family, and I have no problems with hum and noise.
I'm using DJ mixer as front end, with generous labeling so the family could understand which knob to use if there is no sound. DJ mixers are great with lot's off RCA inputs, XLR outputs to interface DSP. Downside is there is now multiple chances to ef-up gainstaging and noise appears. System powers on with single button on a powerstrip or remote controlled receptackles if the mixer is somewhere else than the rest of it.
ps. electricity has been quite expensive on some days so took a power meter out. 6 channels of icepower amplification at normal listening level uses about 25W of power accorsing to the meter. Surprisingly, DSP and DJ mixer together draw another 25W. Perhaps the meter is broken
Anyway, roughly 35kwh per month if always on.
ps. electricity has been quite expensive on some days so took a power meter out. 6 channels of icepower amplification at normal listening level uses about 25W of power accorsing to the meter. Surprisingly, DSP and DJ mixer together draw another 25W. Perhaps the meter is broken
Anyway, roughly 35kwh per month if always on.
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Great project, I have been silently following it since the start Nice distortion measurements too!
Looking at the Vcad 'sixpack', I'm thinking it could be worth a try to tweak the DSP for time alignment/slopes between mid and woofer to align phase further on both sides of XO. This could give you nicer mid-bass. I'm picky with that, and find it usually makes a difference to align them well. It can go from 'good' to 'wow' Same goes for mid/tweet, but they seem pretty well aligned as is.
Keep up the good work!
Nice distortion measurements too!Looking at the Vcad 'sixpack', I'm thinking it could be worth a try to tweak the DSP for time alignment/slopes between mid and woofer to align phase further on both sides of XO. This could give you nicer mid-bass. I'm picky with that, and find it usually makes a difference to align them well. It can go from 'good' to 'wow'
Same goes for mid/tweet, but they seem pretty well aligned as is.Keep up the good work!