I have always wondered why people put so many woofers in a speaker. I always thought it was for power handling. It is later that I realise it is for sensitivity especially in the bass region, very hard to get bass sensitivity up. If 2 x 4ohms will have and increase of 3db. 4 x 8 ohms in parallel series combinations will give you 6 db more.
Another approach is to run some of the midwoofers all the way and end some only bass. Can get very high sensitivity... I have heard this speaker before, the Uluwatu, the sound is actually really nice... one of the best bass I have heard...
Speaker Design Works
The Tectonic BMR drivers seem to be nice for wide bandwidth smooth dispersion use, except they seem to trade-off the sensitivity. For the treble, the power is lost flexing the membrane? For low frequencies it is natural to have low sensitivity for such small diaphragm. You could array them, but then it is back to phase issues due to physical size. Anyway, it is always fight against the physics, size being the most fundamental since the sound in acoustic form has varying size. If one has SPL/sensitivity requirement for a transducer the bandwidth is dictated by that, or the other way around. One can compromise both of course, or have requirements that can be met realistically, physics don't bend no matter how high the desire. Sorry about negative tone, I don't mean to put you down waxxx, hopefully you get a system you can enjoy!🙂
Some measurements on some tectonic transducer here and elsewhere by Googling
Tectonic Elements TEBM35C10-4 Miniature BMR(R) Driver Review
Some measurements on some tectonic transducer here and elsewhere by Googling
Tectonic Elements TEBM35C10-4 Miniature BMR(R) Driver Review
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Checked out few pro audio drivers from faital pro and some others, I'd imagine the numbers being something similar with the hifi brands. According to datasheets 4" drivers barely get near 90dB sensitivity at 400Hz and that is in halfspace so you need big baffle or flat against wall. Half a meter or so baffle could do it. Bigger drivers will do better sensitivity at 400Hz but inherently reduce performance at the top end of the bandwidth due to size. Pro drivers have a bit more sensitivity with the cost of ragged response, compared to hifi drivers (in general) so this is maximum what you get sensitivity wise I predict.
While the bandwidth requirement is the more important 4" is maximum size I'd look at and prepare to go smaller to find good balance on the bandwidth requirement. Toss the sensitivity requirement out of window, it is going to be what it is, closer to 80dB than 90 I would imagine. It is not too important since you weight the wide bandwidth more important anyway.
All in all, you might not find exactly what you are looking for but relax a bit and I'm sure there is fine compromise found. It is just matter of accepting the limits what can be achieved with current physical state of the (hifi) universe and get on with it. No point chasing unicorns. Cheerios 🙂
While the bandwidth requirement is the more important 4" is maximum size I'd look at and prepare to go smaller to find good balance on the bandwidth requirement. Toss the sensitivity requirement out of window, it is going to be what it is, closer to 80dB than 90 I would imagine. It is not too important since you weight the wide bandwidth more important anyway.
All in all, you might not find exactly what you are looking for but relax a bit and I'm sure there is fine compromise found. It is just matter of accepting the limits what can be achieved with current physical state of the (hifi) universe and get on with it. No point chasing unicorns. Cheerios 🙂
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Placed in parallel is +6dB, placed in series nets no voltage sensitivity gain.
Wolf
It will have 3db sensitivity gain versus an equivalent 8 ohm version of the same driver, if I am not mistaken.
Thinking about the design goal a bit more from other perspective, I've understood the goal as: avoiding phase problems on 400-3.5kHz bandwidth while retain some nice overall system bandwidth (30-15kHz for example) and SPL capability.
If we try to keep point source quality with multiple separate transducers you'll notice it is possible to have crossover roughly below 1kHz but soon above that the devices are too big for the wavelengths to get them close enough for 1/4wl c-c distance at crossover on a flat baffle. Only way to circumvent this is to have single transducer playing from the very top, down to frequencies that allow 1/4wl c-c spacing again. As soon as you try think it through you'll find two options, the multiple entry horn way or direct radiator from the top all the way down to the xo where 1/4wl c-c spacing is possible. Direct radiator has no way to control directivity at all, MEH starts to beam much higher in frequency, potentially constant directivity up to 15kHz with advanced waveguide and compatible 1" driver. Huge difference in SPL capability, and cost.
Is there any other options? The three way with wide mid band would have phase problems on the tweeter xo, only at higher frequency, and limited SPL capability by the mid driver size. Maybe it is fine enough. I'd do the two full range driver proto first (big and small drivers, crossover somewhere the 400Hz requirement), easy fast cheap prototype to check out if the project is worth pursuing further. Does it have enough SPL capability, or can the low frequency xo pushed further up without audible issues, or is it MEH time. The proto would be pretty close to single fullrange driver performance, except a bit better since there is now big and small transducers for big and small wavelengths 😉
If we try to keep point source quality with multiple separate transducers you'll notice it is possible to have crossover roughly below 1kHz but soon above that the devices are too big for the wavelengths to get them close enough for 1/4wl c-c distance at crossover on a flat baffle. Only way to circumvent this is to have single transducer playing from the very top, down to frequencies that allow 1/4wl c-c spacing again. As soon as you try think it through you'll find two options, the multiple entry horn way or direct radiator from the top all the way down to the xo where 1/4wl c-c spacing is possible. Direct radiator has no way to control directivity at all, MEH starts to beam much higher in frequency, potentially constant directivity up to 15kHz with advanced waveguide and compatible 1" driver. Huge difference in SPL capability, and cost.
Is there any other options? The three way with wide mid band would have phase problems on the tweeter xo, only at higher frequency, and limited SPL capability by the mid driver size. Maybe it is fine enough. I'd do the two full range driver proto first (big and small drivers, crossover somewhere the 400Hz requirement), easy fast cheap prototype to check out if the project is worth pursuing further. Does it have enough SPL capability, or can the low frequency xo pushed further up without audible issues, or is it MEH time. The proto would be pretty close to single fullrange driver performance, except a bit better since there is now big and small transducers for big and small wavelengths 😉
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No, two drivers in parallel will have +6db compared to one driver.
+3db for double Sd and +3db for half impedance
Doubling the effective speaker area is 3 dB.
Assuming 1x drivers then adding another
2x drivers = 3 dB
then if you wanted to double again it requires
4x drivers = 6dB
Which is a good point.
If you want the ultimate in midrange clarity / dispersion / and sensitivity
It would be the good old fashioned way of using multiple drivers.
Plenty of 4" 5" fullrange drivers will cover this, But...
If your really really concerned about beaming.
Your more likely looking at at least 3" or smaller 1.5" drivers
for superiority around 3 kHz to 4 kHz
Then again that will start imposing on your 300 Hz lower bandwidth
Would probably be looking at 3" driver
And for good sensitivity/ power handling
You would likely do a line array of 4 to 8 drivers.
Definitely steering away from a single driver solution.
But thinking the same thing myself for the ultimate midrange.
I keep going back in fourth between 2x = 4" drivers or 4x to 8x = 3" or 1.5" drivers
Main goal was similar to yours to have a high 3K to 5k crossover to reduce tweeter distortion.
likely have 2x tweeters to reduce distortion.
SPL not the concern for the tweeter.
But obviously when Using 3" or 1.5 " mids
sensitivity and multiple drivers
a must.
All though not a cutting edge design by todays standards,
The Marantz Imperial 8 or Marantz Imperial 9 is still a feasible concept.
Using multiple small mids and multiple tweeters for sensitivity / dispersion
and reduce distortion at high SPL.
Assuming 1x drivers then adding another
2x drivers = 3 dB
then if you wanted to double again it requires
4x drivers = 6dB
Which is a good point.
If you want the ultimate in midrange clarity / dispersion / and sensitivity
It would be the good old fashioned way of using multiple drivers.
Plenty of 4" 5" fullrange drivers will cover this, But...
If your really really concerned about beaming.
Your more likely looking at at least 3" or smaller 1.5" drivers
for superiority around 3 kHz to 4 kHz
Then again that will start imposing on your 300 Hz lower bandwidth
Would probably be looking at 3" driver
And for good sensitivity/ power handling
You would likely do a line array of 4 to 8 drivers.
Definitely steering away from a single driver solution.
But thinking the same thing myself for the ultimate midrange.
I keep going back in fourth between 2x = 4" drivers or 4x to 8x = 3" or 1.5" drivers
Main goal was similar to yours to have a high 3K to 5k crossover to reduce tweeter distortion.
likely have 2x tweeters to reduce distortion.
SPL not the concern for the tweeter.
But obviously when Using 3" or 1.5 " mids
sensitivity and multiple drivers
a must.
All though not a cutting edge design by todays standards,
The Marantz Imperial 8 or Marantz Imperial 9 is still a feasible concept.
Using multiple small mids and multiple tweeters for sensitivity / dispersion
and reduce distortion at high SPL.
Attachments
Four 3" drivers playing up to 3.5kHz would beam like single ~12" driver on the same frequency, on the stacking axis. The "beaming" problem is in the physical dimensions, need to keep small compared to wavelengths. If phase/beaming problems are to be avoided using multiple drivers sharing same bandwidth on flat baffle seems counterproductive, although might sound good enough. Develop and idea how to stack multiple drivers into small enough physical dimensions and you end up with MEH. MEH narrows the low frequency dispersion but is able to widen the high frequency dispersion. While it might be rather narrow nominal dispersion overall, the beaming can be avoided.
Beaming array brings my memory to CBT array, where shading is used to reduce beaming on the stacking axis. So the other option to tackle this design problem would be an array with shading, alright. There is thread in the fullrange forum by nc535 that had many array versions pondered but the array has turned into something that is aproaching MEH, trying to avoid being a MEH 🙂
Beaming array brings my memory to CBT array, where shading is used to reduce beaming on the stacking axis. So the other option to tackle this design problem would be an array with shading, alright. There is thread in the fullrange forum by nc535 that had many array versions pondered but the array has turned into something that is aproaching MEH, trying to avoid being a MEH 🙂
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Well, what i was affraid of happened, people try to push me in the direction i don't want to go. But the tread was still usefull as i got good pointers of what i can do and what pitfalls i need to avoid. I go study those now and see if can find a way how to do what i want (not what you want). I may post the result, but it will probally take a long time to get there as there are many aspects that need to be checked. Thanks anyway for all the remarks and thoughts and tips.
And i already have a lot of systems i love, mostly based on fullrange drivers, and i got more in the making. This project is more an experiment than trying to build my new system. But you never know...
And i already have a lot of systems i love, mostly based on fullrange drivers, and i got more in the making. This project is more an experiment than trying to build my new system. But you never know...
Fair Enough
Then again unless your laying on the ceiling, or laying on the floor
as your listening position.
Horizontal Dispersion, standing or sitting on the couch
is more a concern.
And typical arrays are more than good for normal listening.
Going back to a single driver solution
That is a great thing about todays world.
Lots of " fullrange" drivers that cover very wide bandwidth
So used as a midrange would be rather nice.
Even incredibly common 4" drivers like the
Dayton RS100
Dayton RS100P
Tang Band W4-1337SDF
DynaVox LY401F
all would work well as good midrange drivers.
Not only the overall size, but the depth of these cones
are shallow. Which helps greatly
with the beaming requirements.
As mentioned before, overall size is a good rule of thumb
for beaming.
But many other factors like surround and cone depth
play into beaming.
There is plenty of modern drivers which should
beam earlier according to the diameter theory.
But they dont because of other factors in the
overall design.
Then again unless your laying on the ceiling, or laying on the floor
as your listening position.
Horizontal Dispersion, standing or sitting on the couch
is more a concern.
And typical arrays are more than good for normal listening.
Going back to a single driver solution
That is a great thing about todays world.
Lots of " fullrange" drivers that cover very wide bandwidth
So used as a midrange would be rather nice.
Even incredibly common 4" drivers like the
Dayton RS100
Dayton RS100P
Tang Band W4-1337SDF
DynaVox LY401F
all would work well as good midrange drivers.
Not only the overall size, but the depth of these cones
are shallow. Which helps greatly
with the beaming requirements.
As mentioned before, overall size is a good rule of thumb
for beaming.
But many other factors like surround and cone depth
play into beaming.
There is plenty of modern drivers which should
beam earlier according to the diameter theory.
But they dont because of other factors in the
overall design.
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Also take a look at Kartesian, they have some nice drivers.
Here you can find some measurements of the Wom120_vMS 4.5"
The Mid120_vHE looks promising but is not yet for sale
Here you can find some measurements of the Wom120_vMS 4.5"
The Mid120_vHE looks promising but is not yet for sale
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waxx, sorry about preaching, thinking it through as I write and always end up with the MEH. Of course you can have system that you want, experimenting (building interesting system) is the most fun part! Remember to have fun!🙂
I am referring to why Juhazi is using 2 pcs of 4 ohm driver in series versus a single 8 ohm driver of the same model. Both are 8 ohm loads but one is 3db more sensitive than the other. It effectively doubles the driver cost though. This is the approach that many hifi speaker manufacturers uses, 2 X 6 inch driver versus 1 x 8". The issue is sensitivity is very critical because if your mids are 88db. Your woofers need to be about 94db to match the mids because of baffle loss. Hifi woofers don't reach 94db sensitivity... so this is the way to get around the issue.
Oon
Most 4R vs. 8R versions of same woofer have different nominal sensitivity (per voltage), 4R being more sensitive. Doubling those series or parallel will change net sensitivity, and impedance. https://geoffthegreygeek.com/multiple-speakers-share-power/
My personal case was renovation of active speakers and in each speaker other woofer had burned. So same impedance versions were bought. And, because of turning speakers to multiway DSP-controlled made it easy to use different mid and tweeter than the originals had.
Here my woofers Scanspeak 22W 4R/8R sensitivity 92,4/88,8 dB
I guess many of us have noticed, that many commercial 3-way tower speakers come with double 4R woofers parallel, and thus present a challenge to the amplifier.
My personal case was renovation of active speakers and in each speaker other woofer had burned. So same impedance versions were bought. And, because of turning speakers to multiway DSP-controlled made it easy to use different mid and tweeter than the originals had.
Here my woofers Scanspeak 22W 4R/8R sensitivity 92,4/88,8 dB
I guess many of us have noticed, that many commercial 3-way tower speakers come with double 4R woofers parallel, and thus present a challenge to the amplifier.
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Okay, that may be true, depending on differing driver specs. As I read your reply, you did not specify this as such.
Wolf
DMLs are all chaotic behaviour. The art of designing a DML is getting a flat distribution of resonances. Even a 4’x8’ DML has very good dispersion. One of teh reasons early on they were troaled as Tannoys in things like train stations.
dave
Another way of looking at it is since if you put 2 X 4R in series, power will be reduced to 1/4. So output is down 6db but having two of them, it is up 6db. So it is back to original sensitivity, except it is now 8R. Of course another way of doing it is just use a 4R speaker of course. I suppose nominal 8R is preferred for hifi purpose....
Wow the Magico drops down to 2 ohm. I wonder if what caused it to happen might now be two 4 ohms in parallel but having a 4 ohm with a capacitor in series to boost the bass?
Oon