I’ve been experimenting with simulating an active/passive crossover. At this stage, this is just proof of concept activity. It has no real application to the final product, but it demonstrates to me that the concept of an active lower crossover combined with a passive upper crossover has merit.
I have not selected the drivers yet, but I know the woofer will be 8 inch. I assume the mid driver will be a 4 – 5 inch driver. At this point, I assume the tweeter will have a waveguide for best directivity control.
For simulation, I used measured acoustical and impedance data from earlier projects. I used data from an SB23MFCL45 in a 10” wide enclosure to represent the 8” driver. I used an SB15CAC30 in a 10” wide beveled enclosure to represent the mid driver. I used a Satori TW29BNWG to represent a typical dome tweeter with waveguide.
This crossover seems reasonable. The woofer is fully active, with one amp channel. The mid/tweeter has the other amp channel and has a blend of active and passive networks. I forced the driver sensitivity/gain to be compatible with each other, whereas in a real crossover I would need a resistor network on the tweeter as a minimum.
Of course, the actual drivers I select will have somewhat different directivity and frequency responses than this proof of concept simulation. But this exercise has convinced me that this approach is feasible.
I have not selected the drivers yet, but I know the woofer will be 8 inch. I assume the mid driver will be a 4 – 5 inch driver. At this point, I assume the tweeter will have a waveguide for best directivity control.
For simulation, I used measured acoustical and impedance data from earlier projects. I used data from an SB23MFCL45 in a 10” wide enclosure to represent the 8” driver. I used an SB15CAC30 in a 10” wide beveled enclosure to represent the mid driver. I used a Satori TW29BNWG to represent a typical dome tweeter with waveguide.
This crossover seems reasonable. The woofer is fully active, with one amp channel. The mid/tweeter has the other amp channel and has a blend of active and passive networks. I forced the driver sensitivity/gain to be compatible with each other, whereas in a real crossover I would need a resistor network on the tweeter as a minimum.
Of course, the actual drivers I select will have somewhat different directivity and frequency responses than this proof of concept simulation. But this exercise has convinced me that this approach is feasible.
Yes!
I have been doing this for years in projects were resources and/or budget are limited. It works extremely well and saves one extra amplifier.
You can even improve the noise from the amplifier drastically, when you attenuate the tweeter passively. Which is at least 6dB from the bafflestep plus the additional extra sensitivity tweeters have.
The bafflestep doesn't seemed to be modeled in here I think?
I personally would give the woofer a 4th order filter.
Thanks for your thoughts. I had not considered that aspect.
Actually, the NF response shape of this particular woofer has a natural 4 dB drop from 100 to 500 Hz, so it does not require the full 6 dB of baffle step. I am using a + 3db shelf at 200 Hz. A different woofer will need a different shelf.
SB23MFCL45-8, sealed box, Near Field
I was more talking about the tweeter, because I don't see any additional attenuation with the tweeter.
Which feels odd, although not impossible, because of the bafflestep as well as the higher sensitivity.
But anyway, like you mentioned, this is just some preliminary investigation (which I applaud btw!)
It is something to keep in mind for the real thing.
Btw, attenuating the tweeter will cost (a lot) more power and voltage from the amplifier.
Also something to consider.
Although the real power in the upper frequencies isn't that big plus you would have had the same issue with a fully passive filter anyway.
btw, depending how many resources (taps and instructions) you have left, you could also combine this with just FIR phase compensation.
Sometimes that will work out a bit more efficient than just doing all FIR filters.
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No need for a three way here giving your criteria….the new Dayton Sig225 8” woofer will get you to 40hz and plays ruler flat to 2khz……….cross to a 1” compression driver around 1.6khz and you’ve got a rockin two way with a near perfetc directivity index through the crossover region and above.
With only 4 drivers and less amp modules, you’ve got more $$$ to play with so a robust Scanspeak or SBAcoustics dome at 1.6khz isn’t out of the question either
With only 4 drivers and less amp modules, you’ve got more $$$ to play with so a robust Scanspeak or SBAcoustics dome at 1.6khz isn’t out of the question either
It is certainly true that some people believe that an 8" 2-way will do whatever an 8" 3-way will do.
Whether it is true or not, the primary goal is that the final speaker will be a "compact, active, 3-way with 8” woofer, with a total internal volume of 16-24 liters, with sealed box bass alignment."
Here are my thoughts on the value of a 3-way vs 2-way with nearly the same drivers...
https://www.diyaudio.com/community/threads/tall-thin-2-way-for-workshop-pc.402268/post-7427612
j.
Whether it is true or not, the primary goal is that the final speaker will be a "compact, active, 3-way with 8” woofer, with a total internal volume of 16-24 liters, with sealed box bass alignment."
Here are my thoughts on the value of a 3-way vs 2-way with nearly the same drivers...
https://www.diyaudio.com/community/threads/tall-thin-2-way-for-workshop-pc.402268/post-7427612
j.
There are some good points made here.
A 8" mid-woofer can be paired with an 1" dome tweeter.
MarkK did this almost 18 years ago with a 1" aluminium dome tweeter (RS28A (NLA), sans waveguide
https://web.archive.org/web/2010123...istics.org/projects_gallery/photo_gallery.htm
@Pida
did this recently, and much to his surprised, sounded very good (SS 21W/8555=10 + D304/6600 + WG)
https://pkaudio.webnode.cz/21w-6600-wg/
@A4eaudio also did one, again using the RS225-8 in isobaric configuration (great idea for reducing required box volume). Paired with the SBA Satori dimple dome TW29RN-B (8). + Passive radiator:
https://diy.midwestaudio.club/discussion/comment/40438#Comment_40438
Winner winner chicken dinner!
David Fred also did one recently, this time using the tried and trusted RS225-8, with a different tweeter R2604/8320 + WG + heavily optimised cabinet:
https://www.htguide.com/forum/forum...anspeak-d2604-833000-in-wg300-~42-litre/page2
He also won an award!
https://www.htguide.com/forum/forum...833000-in-wg300-~42-litre?p=946944#post946944
I for one, still haven't done a 2-way with the PTT8.0X drivers I have on hand, despite having them since release. Talk about being late to the 8" 2-way party...
I think it will be an interesting journey for hifijim. With straight forward rectangular cabinets, no after-market waveguides, I wonder if filler (mid) driver is necessary.
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I heard the @A4eaudio isobaric at the May event. There were two isobaric entries, and both of them had very smooth midrange, with good clarity and detail. I noticed imediately that those two speakers were different from all the other 2-ways being demoed.
I recently completed this speaker. 2-way with SB26CDC tweeter and SB17NBAC woofer. It sounds quite good.
In 2020 I made this speaker, with almost identical drivers... SB26CDC tweeter and SB17CAC as midrange, but with a 12" woofer... crossover was 200 Hz, so the midrange saw very little bass energy.
In terms of clarity, detail, dynamics, and sense of realism, there is no comparison between the two. The 3-way is in a whole different league.
Necessary? no. but very helpful in mitigating IM distortion, especially in a sealed box design with linkwitz transfer. There can be quite a bit of bass cone movement, and it is very beneficial to have a dedicated bass driver so the midrange is not affected.
I recently completed this speaker. 2-way with SB26CDC tweeter and SB17NBAC woofer. It sounds quite good.
In 2020 I made this speaker, with almost identical drivers... SB26CDC tweeter and SB17CAC as midrange, but with a 12" woofer... crossover was 200 Hz, so the midrange saw very little bass energy.
In terms of clarity, detail, dynamics, and sense of realism, there is no comparison between the two. The 3-way is in a whole different league.
You have complete concurrence with me on that one Jim.
as you know @5th element and I have done a deep dive on the SB12-SB23 in our quest to build a coaxial, and we are intimately familiar with it, having purchased different sizes, measured them, deconstructed them, put them back together, measured them etc…
The Kms symmetry is lacking, and cone area is relatively small, given the frame size. Class leading motor and cone, soft parts (surround and spider) on the other hand not class leading.
Everything below 150Hz can be done better with bigger drivers, or better 7” midwoofers. Eg. SS, Satori, current SEAS standard “Prestige” range…
as you know @5th element and I have done a deep dive on the SB12-SB23 in our quest to build a coaxial, and we are intimately familiar with it, having purchased different sizes, measured them, deconstructed them, put them back together, measured them etc…
The Kms symmetry is lacking, and cone area is relatively small, given the frame size. Class leading motor and cone, soft parts (surround and spider) on the other hand not class leading.
Everything below 150Hz can be done better with bigger drivers, or better 7” midwoofers. Eg. SS, Satori, current SEAS standard “Prestige” range…
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Interestingly, the Isobaric designs did pretty well this year. The other entry that you heard was Bill S. (4thtry) who placed 3rd at the Parts Express Speaker Design Competition in the Dayton Audio category. Also at InDIYana, but not in the theme competition, were jhollander's "Not Qualified", aptly named because his Wavecore tweeter was too big for the competition rules. He placed third at the Parts Express SDC in the over $300 category, using RS225P's in isobaric.
I think it was Linn that first produced the isobaric design... yes? I remember hearing the original Linn Isobaric.
After listening to your design and Bill S.'s fine speaker... I suspect the isobaric architecture does something special to preserve the midrange clarity... Great job on your speaker by the way.. we were only able to speak briefly.
After listening to your design and Bill S.'s fine speaker... I suspect the isobaric architecture does something special to preserve the midrange clarity... Great job on your speaker by the way.. we were only able to speak briefly.
That idea is not that far fetched.
Like double glazing for glass windows... perhaps it functions to "double insulate the front cone"... I wonder how this observation could be tested empirically...
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3-way has wide and smooth directivity and low IMD. Active sealed can be pushed to low F as far as Xmax allows
You cant buy active midsize 3-ways from a shop, unlike 8" 2-way monitors. Diying monitor sized 2-way actives is waste of time - eg. Adam audio T8V costs 250€ piece.
You cant buy active midsize 3-ways from a shop, unlike 8" 2-way monitors. Diying monitor sized 2-way actives is waste of time - eg. Adam audio T8V costs 250€ piece.
https://en.wikipedia.org/wiki/Isobaric_loudspeaker
Hi, isobaric woofer advantage for sound quality must be from some cancellation of some distortion mechanisms? On a speaker, where same woofer is responsible for bass and midrange, excursion due to bass signal will distort also midrange. In general, excursion changing motor and mechanical parts properties means the whole bandwidth gets changed properties, which means the whole bandwidth distorts.
For three way speaker excursion is greatly reduced for midrange as there is separate driver. Bandwidth of all transducers is reduced. On a small two way speaker reducing distortion by what ever means would improve sound because by necessity there is quite a lot of excursion with the woofer, also on the tweeter. On a big two way speaker excursion is still modest so perhaps not such an audible thing. Big three way would better both in this regard
small two way, use best drivers.
edit. tktran mentions "double isolation", sound leaking through the cone is reduced? Makes sense. Also forces to vibrate the box are distributed, originating from two different locations at the same time, perhaps averaging some of that out as well. So, in general isobaric seems to reduce noise in addition to allowing smaller box. Seems worthwhile, at least on small two way speakers, why not for small anyway speakers
Hi, isobaric woofer advantage for sound quality must be from some cancellation of some distortion mechanisms? On a speaker, where same woofer is responsible for bass and midrange, excursion due to bass signal will distort also midrange. In general, excursion changing motor and mechanical parts properties means the whole bandwidth gets changed properties, which means the whole bandwidth distorts.
For three way speaker excursion is greatly reduced for midrange as there is separate driver. Bandwidth of all transducers is reduced. On a small two way speaker reducing distortion by what ever means would improve sound because by necessity there is quite a lot of excursion with the woofer, also on the tweeter. On a big two way speaker excursion is still modest so perhaps not such an audible thing. Big three way would better both in this regard
small two way, use best drivers.edit. tktran mentions "double isolation", sound leaking through the cone is reduced? Makes sense. Also forces to vibrate the box are distributed, originating from two different locations at the same time, perhaps averaging some of that out as well. So, in general isobaric seems to reduce noise in addition to allowing smaller box. Seems worthwhile, at least on small two way speakers, why not for small anyway speakers
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This is going off on a wild tangent (hifijim feel free to report to moderator to remove this post)
But I was trying to figure out the unusual smell in a vacuum cleaner. My left leaning, hybrid driving, tree hugging, over-recycling spouse asked me to have a look at the vacuum cleaner. As the HEPA filter, exhaust filter and vacuum bag had recently been changed, it was odd that it would emit an malodorous scent through the exhaust duct.
This an Electrolux bagged canister vacuum machine, model range Ultrasilencer,
(precursor to the current Silentperformer) range.
It was a low-medium cost ($300) vacuum cleaner purchased about 15 years ago.
Anyway, to my surprise- it uses Dacron or other dense polyester type fibrefill material wedged deep, inside between the vacuum motor and external casing. Here are the photos for your viewing displeasure.
No wonder it is extremely quiet in use (imagine having a sleeping baby (or listening to music) and vacuuming in the same room, but stinks after a decade of use!
Now, from my mechanic, I know luxury cars (BMW, Mercedes) etc have, amongst other things, a LOT of sound deadening material. We are talking hundreds of lbs of it, just to keep the interior silent. Even the door seals are a different grade- to provide that reassuring “thunk” when people close the doors. Now this is the sound of luxury automobiles, at least in the internal combustion engine vehicles of the late 20th century.
So if you buy a base model Toyota- you get none of it. Keeps weight down and MPG up, Buy a Lexus, and you get it all factory fitted, by default, invisible to end user.
I just never expected this in a vacuum cleaner!
Excuse me for connecting the dots too loosely, but back to speakers… obviously whatever is going on the backside of the cone is emitted and reflected and absorbed and needs to be managed in a traditional cabinet speaker.
In an isobaric mounted configuration; there an air gap between the two cones.@A4eaudio
How leaky is the air gap? Would it provide an insulating layer between the sound behind coming from behind the rear cone, and the radiation through the front cone?
I wonder if this testing is something that @augerpro will be able to test in the (not too distant) future- effect of rear wave radiation through a cone VS isobaric cone…
But I was trying to figure out the unusual smell in a vacuum cleaner. My left leaning, hybrid driving, tree hugging, over-recycling spouse asked me to have a look at the vacuum cleaner. As the HEPA filter, exhaust filter and vacuum bag had recently been changed, it was odd that it would emit an malodorous scent through the exhaust duct.
This an Electrolux bagged canister vacuum machine, model range Ultrasilencer,
(precursor to the current Silentperformer) range.
It was a low-medium cost ($300) vacuum cleaner purchased about 15 years ago.
Anyway, to my surprise- it uses Dacron or other dense polyester type fibrefill material wedged deep, inside between the vacuum motor and external casing. Here are the photos for your viewing displeasure.
No wonder it is extremely quiet in use (imagine having a sleeping baby (or listening to music) and vacuuming in the same room, but stinks after a decade of use!
Now, from my mechanic, I know luxury cars (BMW, Mercedes) etc have, amongst other things, a LOT of sound deadening material. We are talking hundreds of lbs of it, just to keep the interior silent. Even the door seals are a different grade- to provide that reassuring “thunk” when people close the doors. Now this is the sound of luxury automobiles, at least in the internal combustion engine vehicles of the late 20th century.
So if you buy a base model Toyota- you get none of it. Keeps weight down and MPG up, Buy a Lexus, and you get it all factory fitted, by default, invisible to end user.
I just never expected this in a vacuum cleaner!
Excuse me for connecting the dots too loosely, but back to speakers… obviously whatever is going on the backside of the cone is emitted and reflected and absorbed and needs to be managed in a traditional cabinet speaker.
In an isobaric mounted configuration; there an air gap between the two cones.@A4eaudio
How leaky is the air gap? Would it provide an insulating layer between the sound behind coming from behind the rear cone, and the radiation through the front cone?
I wonder if this testing is something that @augerpro will be able to test in the (not too distant) future- effect of rear wave radiation through a cone VS isobaric cone…
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That's true Juha- I never bothered- Suppose I can buy 21W/8555 for €90 apiece. I'd rather two per side for twice the Sd...
But back when the RS225-8 was $40 a pop, someone probably bought a carton of them. And since they favour a minimum of 40L-50L ported, cramming two, for $80 of woofering into a 20L cabinet is a nice idea. At current prices I'm not sure it represents good value. But it is interesting, nonetheless what Jim observed, whether real, or perceived, I for one haven't read it being discussed/studied. All the discussion was about cabinet volume minimization...
But back when the RS225-8 was $40 a pop, someone probably bought a carton of them. And since they favour a minimum of 40L-50L ported, cramming two, for $80 of woofering into a 20L cabinet is a nice idea. At current prices I'm not sure it represents good value. But it is interesting, nonetheless what Jim observed, whether real, or perceived, I for one haven't read it being discussed/studied. All the discussion was about cabinet volume minimization...
I did some ISObasic subwoofer back in the day with surplus 12” NHT sub drivers in sealed boxes……two of them still reside in my personal home studio as the cleanest subs with the lowest group delay I’ve ever experienced. Gave away the rest to friends who still have them. Used Dayton 200w plate amps with built in bass boost. They dig deep for music and music production and in multiples could do HT.
But we digress on the topic of two way vs three way. For me on a personal level, the only REAL midrange driver that’s acceptable for home hifi and critical monitoring is the dome……cones just don’t excel in the 700hz to 2khz range IMO. Low crossed two ways are so well regarded against the typical woofer/tweeter as the dome brings that upper midrange clarity up front, where it belongs and retains that point source quality.
Others will differ with the above statement….and some will do so strongly….but to them I would say forget the lagging and loose aural memory and do a side by side if you get a chance….and tell me I’m still wrong.
But we digress on the topic of two way vs three way. For me on a personal level, the only REAL midrange driver that’s acceptable for home hifi and critical monitoring is the dome……cones just don’t excel in the 700hz to 2khz range IMO. Low crossed two ways are so well regarded against the typical woofer/tweeter as the dome brings that upper midrange clarity up front, where it belongs and retains that point source quality.
Others will differ with the above statement….and some will do so strongly….but to them I would say forget the lagging and loose aural memory and do a side by side if you get a chance….and tell me I’m still wrong.
There is no cancelation.
There is just less adding.
Cancelation would only occur when signals are out of phase.
They are not out of phase, they are just two separate sound sources in phase with each their own distortion profile. Which just adds up.
The front side of a woofer just distorts a little different than the back side.
Although with some really good performing speakers this is close to be symmetrical.
Just having two drivers parallel but mounting one backwards will do the exact same thing (from a distortion point of view that is).
I think this "cancelation" idea came from Linkwitz. I never understood why he missed this very important nuance.
Like I mentioned yesterday in the Hornresp topic, isobaric makes very little sense anno 2023 in an active system with DSP.
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