Design is wandering; slapping tweeter up top without due consideration and measurements is shooting blind.
OB forced close to wall begs undesirable early reflections.
Low order cross with 8" woofer at wide baffle spacing produces highly lobed response.
Speaker doubtless sounds best with 12P solo, and this is doubtlessly thin.
Without measurements and design tools it is all to 'taste' by ear, and will be OK, until you tire of how the speaker is stamping it's sound on everything played through it.
Within designed full range application and appropriate box type enclosure to augment/support lower end driver has potential to sound very good.
OB is tough territory for ultra light weigh, shallow depth diaphragm.
Good luck
OB forced close to wall begs undesirable early reflections.
Low order cross with 8" woofer at wide baffle spacing produces highly lobed response.
Speaker doubtless sounds best with 12P solo, and this is doubtlessly thin.
Without measurements and design tools it is all to 'taste' by ear, and will be OK, until you tire of how the speaker is stamping it's sound on everything played through it.
Within designed full range application and appropriate box type enclosure to augment/support lower end driver has potential to sound very good.
OB is tough territory for ultra light weigh, shallow depth diaphragm.
Good luck
I've had a bit of a ponder on this: essentially your saying at 20Khz the sensitivities of each driver is at maximum. The 10 Ohm tweeter is at 92db and 15 Ohm A12 is at 89db from spec sheet. That the impedance difference between drivers is irrelevant? Correct?This is simple enough I guess. But I'm not convinced it's as simple as that, just yet.
Have a think about how 8 Ohm and 4 Ohm, but otherwise identical woofers, the 4 Ohm version is nominally 2-3db more efficient.
Also note: the resistor value I've settled on for now is 5.6 Ohms. I didn't calculate this. I started with a 3.3, went up to a 4.7, then to a 5.6. Now it just so happens we have both drivers at roughly 15 Ohms don't we?
What about looking at a single driver. The driver is generally loudest, most efficient where the impedance is lowest. Your contention suggests that resistors are really only to correct for a 'sensitivity' imbalance between drivers. But what causes the imbalance? It isn't just 'efficiency'. I reckon somewhere there's an equation/formula to calculate for this. But my maths is terrible.
Have a think about how 8 Ohm and 4 Ohm, but otherwise identical woofers, the 4 Ohm version is nominally 2-3db more efficient.
Also note: the resistor value I've settled on for now is 5.6 Ohms. I didn't calculate this. I started with a 3.3, went up to a 4.7, then to a 5.6. Now it just so happens we have both drivers at roughly 15 Ohms don't we?
What about looking at a single driver. The driver is generally loudest, most efficient where the impedance is lowest. Your contention suggests that resistors are really only to correct for a 'sensitivity' imbalance between drivers. But what causes the imbalance? It isn't just 'efficiency'. I reckon somewhere there's an equation/formula to calculate for this. But my maths is terrible.
This is true enough. Some of this is subjective, I guess this is just a fundamental con of OB generally. On the plus, It gives a very live, present, engaging presentation. Everything sounds good. I'm cool with that, for now.
The 'fullness' or fatness of it is much better than I was expecting.
When I get tired of it, I'll just swap it over to something else. Some other 'boxed' project. I don't take it that seriously.
Didn't notice your last post. It is as simple as your first paragraph.
The 4 vs 8 ohm. They are 3db apart at 2.83V, but they are the same at 1 watt. That's the catch. One is not free SPL.
Your example of resistor choice is just a fluke, and not even valid without measurements.
Your last point about being loudest at the drivers lowest impedance is also not really true. Look at how effecient a woofer is at Fs. Or way up in the breakup region.
Have fun. I can't keep going on about this.
The 4 vs 8 ohm. They are 3db apart at 2.83V, but they are the same at 1 watt. That's the catch. One is not free SPL.
Your example of resistor choice is just a fluke, and not even valid without measurements.
Your last point about being loudest at the drivers lowest impedance is also not really true. Look at how effecient a woofer is at Fs. Or way up in the breakup region.
Have fun. I can't keep going on about this.
Cons of OB are need for high linear excursion and EQ for flat response; pros are much less baffle resonance, and no re-radiation of sound reflected in box, no energy storage in ports. These pros are some of the elements that make OB engaging, even without EQ and optimal baffle.
'by fanatics, for fanatics' and all levels of interest.
Enjoy!
You could get somewhat more bass by adding a series resistor to the Alpair (ie, make it properly full-range).
This might seem counter-intuitive, but the reasoning goes as follows:
- around Fs, the impedance of the speaker increases.
- a series resistor acts as a potential divider
- at Fs, the speaker sees much more voltage than at other frequencies, so the amount of power it gets in the LF region also increases (compared to the rest of the frequency range), so you get a bass boost at Fs, but not below (where excursion would be large due to the very low frequencies)
Try resistor values of 1ohm to 4r7.
Yes, you lose some power in the resistor, but in a home hifi situation, it won't be much.
Thank you for the suggestion/idea Chris661. I might try that, just as a temporary experiment. Report my findings. I'm not too keen on series resistors they are a necessary evil. IMO They have a side effect: they suppress micro dynamics. With the woofer engaged bass (lack of) isn't an issue. The full/fat-ness from A12 on it's own is surprisingly satisfying. It's good for me to be have a lean sounding option. The reduced bass impact is more comfortable for me in regard to my neighbours. I can get more use out of my system: watch TV less and listen to music more.
Ahhaaaaa! I THINK I can see what tuxedocivic was trying to explain to me. Voltage and wattage are different. Voltage can remain constant while wattage consumed by driver/supplied by amp will vary according to driver impedance. So an imbalance between drivers in watts doesn't mean an imbalance in output volume. I THINK. I was getting confused by a calculator I was using.
Assuming 2.83 = 1 watt at (x) Ohms
At 20Khz amp sees 6 Ohms from 2 x drivers in parallel. At 20 Khz the A12 is 15 Ohms and 89 db efficient. Uses 0.4 watt. At 20Khz the tweeter is 10 Ohms and 92db efficient. Uses 0.6 watt. We still can assume 1 volt input/output. Volume is related to input voltage. Watts is related to power consumed to achieve a given output/voltage.
Apologies for my noob/boof-headedness
Assuming 2.83 = 1 watt at (x) Ohms
At 20Khz amp sees 6 Ohms from 2 x drivers in parallel. At 20 Khz the A12 is 15 Ohms and 89 db efficient. Uses 0.4 watt. At 20Khz the tweeter is 10 Ohms and 92db efficient. Uses 0.6 watt. We still can assume 1 volt input/output. Volume is related to input voltage. Watts is related to power consumed to achieve a given output/voltage.
Apologies for my noob/boof-headedness
Update: A12P running without any filtering. For a reference/example of how low the A12P plays: take the Massive Attack track 'Angel' which has this intro that has a kick drum and click beat with a low, pulsing rumble (bass guitar detuned I think). You can clearly hear the upper 30 - 40% of this rumble through the A12. I was surprised! Fiddling with 2nd order filters on the woofer and super-tweeter. I believe this should give me 180 degrees phase against the unfiltered A12, no reverse polarities.
Timboz, Excellent, I'm a true believer as many know that if you can eliminate crossover parts in the chain the purity of the signal has a clarity that is unbelievable. This driver allows me to have an entirely separate subwoofer set up out of the way of the 12P's with a crossover point well out of the way of any critical area, truly seamless. Timboz, your correct in your assessment, the mid low strength of this driver is astounding. Although I must admit I have not felt the need to add a tweeter, quite happy with the extension, quite natural to my ears. Btw, I run OB configuration as well, and it's magical!
I recently played some MP3 sine waves (via iPod quickly flicking from to to another) at intervals of 10Hz at a fixed, fairly modest listening volume. I can't measure, only listen. I also have a XLBaffle 'sim' and now I can say that the sim actually seems pretty accurate, from what I can gather.
In it's current baffle set-up the A12P (no filtering) starts to roll off at 6db (I think) from around 250Hz, maybe a bit lower. A12 is just audible at around 70Hz. But barely audible at all by 60 - 50Hz. It's still useful/handy for quiet listening sessions by itself.
The woofer in sealed box plays audibly, 'usefully' down to about 60Hz or so. Not as low as I was hoping.
The output from woofer will overlap the output of the A12 at around 120 Hz judging by the sim. But I might aim the XO a bit higher to keep the values of inductors as small as possible. Maybe a 2nd or 3rd order at 150Hz kind of thing.
In it's current baffle set-up the A12P (no filtering) starts to roll off at 6db (I think) from around 250Hz, maybe a bit lower. A12 is just audible at around 70Hz. But barely audible at all by 60 - 50Hz. It's still useful/handy for quiet listening sessions by itself.
The woofer in sealed box plays audibly, 'usefully' down to about 60Hz or so. Not as low as I was hoping.
The output from woofer will overlap the output of the A12 at around 120 Hz judging by the sim. But I might aim the XO a bit higher to keep the values of inductors as small as possible. Maybe a 2nd or 3rd order at 150Hz kind of thing.
If anyone is still there
I've repurposed my Onken style cabinets for distributed mono bass, and put my 12P pair on small, stand mounted open baffles.
And I was unable to resolve hum issues from some pro audio active crossovers, so I'm now wiring things without a passive crossover, but using the digital crossover in a factory refurbished Arcam Diva AVP 700 digital processor.
(A pleasant surprise- must be a new chip, as it handles new bluray audio formats).
Anyways, this preamp has a excellent digital crossover, with at 40-130 hertz points, time alignment adjustable on the fly, by ear, for each speaker and sub.
It's also a very good sounding DAC, and was available for CDN $329 , free delivery, and a 12 month warrantee.
Life is much easier with this built in active crossover, and it turns out corner loaded Onkens with 15 inch woofers, and between the stereo 12Ps, a push pull pair of W frame 18 inch subwoofers/tv stand, produces punchy, pitch clear, bass , which easily blends with the Markaudio pair.
Couldn't be happier with this solution for an integrated DAC, 2.1 channel home theatre processor, bass management, preamp .
Oh, it also has digital bass and treble controls (defeatable) individually, for each channel.
Just saying, this sort of thing can put a lot of easy love back in your music projects.
I've repurposed my Onken style cabinets for distributed mono bass, and put my 12P pair on small, stand mounted open baffles.
And I was unable to resolve hum issues from some pro audio active crossovers, so I'm now wiring things without a passive crossover, but using the digital crossover in a factory refurbished Arcam Diva AVP 700 digital processor.
(A pleasant surprise- must be a new chip, as it handles new bluray audio formats).
Anyways, this preamp has a excellent digital crossover, with at 40-130 hertz points, time alignment adjustable on the fly, by ear, for each speaker and sub.
It's also a very good sounding DAC, and was available for CDN $329 , free delivery, and a 12 month warrantee.
Life is much easier with this built in active crossover, and it turns out corner loaded Onkens with 15 inch woofers, and between the stereo 12Ps, a push pull pair of W frame 18 inch subwoofers/tv stand, produces punchy, pitch clear, bass , which easily blends with the Markaudio pair.
Couldn't be happier with this solution for an integrated DAC, 2.1 channel home theatre processor, bass management, preamp .
Oh, it also has digital bass and treble controls (defeatable) individually, for each channel.
Just saying, this sort of thing can put a lot of easy love back in your music projects.
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Shooting blind,after seeing your idea.
I already had 4 12PW here, and wanted to try out easy frequency ranges for each pair on a baffle.
I put a 3/4" backing behind the two 12PW, which allows some baffle thickness after routering the main baffle for flushmounting them.
I started with one run full range, and the other uses an FMOD lowpass about 100 Hz, checked with test tones, and it's pretty close, so I lucked out with my power amp input impedance.
Next up was highpassing the top 12PW at 100 Hz with another FMOD.
This is probably one of the first time I've heard the benefits of reducing excursion so clearly.
Next up was going after a slight chesty resonance in some male vocals with an also already here change to a pair of 300 Hz highpasses, which worked barely a little more than I'd prefer.
I'm out of FMODs, but checking online, found they are still available, so I've ordered a pair of 200 hz lowpasses for these.
It could be expectation bias, but when I tried this with a 12P, the FMODs seem to lose some slight upper upper treble, and a bit of expansive soundstaging that goes with that, but it doesn't seem noticeable with the 12PW.
I think with the 3/16" gap between the full ranges, I'm about at the limit to avoid flat out driver to driver comb filtering, but there may be some from just having distance differences to my ears from each driver in a pair of drivers, but to me it sounds better even than I had hoped having two identical drivers doing near full range and bass and some midbass on a smallish open baffle.
It's small enough I did add a 5 inch deep wing on one side, but two brought back the chesty vocal resonance, so I stopped there.
Thanks for the idea. I intended using the FMODs until designing a passive crossover for use with a single amp, but this easy result was too good for me to leave behind.
It's exactly the harmonically alive bass I love hearing with music, and doesn't really need a sub for music, although for sci fi movies in my all in one mainly 2 channel system I will use a sub lowpassed at 40 hertz.
I already had 4 12PW here, and wanted to try out easy frequency ranges for each pair on a baffle.
I put a 3/4" backing behind the two 12PW, which allows some baffle thickness after routering the main baffle for flushmounting them.
I started with one run full range, and the other uses an FMOD lowpass about 100 Hz, checked with test tones, and it's pretty close, so I lucked out with my power amp input impedance.
Next up was highpassing the top 12PW at 100 Hz with another FMOD.
This is probably one of the first time I've heard the benefits of reducing excursion so clearly.
Next up was going after a slight chesty resonance in some male vocals with an also already here change to a pair of 300 Hz highpasses, which worked barely a little more than I'd prefer.
I'm out of FMODs, but checking online, found they are still available, so I've ordered a pair of 200 hz lowpasses for these.
It could be expectation bias, but when I tried this with a 12P, the FMODs seem to lose some slight upper upper treble, and a bit of expansive soundstaging that goes with that, but it doesn't seem noticeable with the 12PW.
I think with the 3/16" gap between the full ranges, I'm about at the limit to avoid flat out driver to driver comb filtering, but there may be some from just having distance differences to my ears from each driver in a pair of drivers, but to me it sounds better even than I had hoped having two identical drivers doing near full range and bass and some midbass on a smallish open baffle.
It's small enough I did add a 5 inch deep wing on one side, but two brought back the chesty vocal resonance, so I stopped there.
Thanks for the idea. I intended using the FMODs until designing a passive crossover for use with a single amp, but this easy result was too good for me to leave behind.
It's exactly the harmonically alive bass I love hearing with music, and doesn't really need a sub for music, although for sci fi movies in my all in one mainly 2 channel system I will use a sub lowpassed at 40 hertz.
Make your own. FMODs are highly compromised PLLXO.
https://www.t-linespeakers.org/tech/filters/passiveHLxo.html
dave
It is DIY, assembly is your job.
An FMOD has a terminating resistor which greatly compromises the filter. For the HP, if you use the actual input impedance of your amplifier instead of the terminating resistir should open things up (we are talking about a single cap). LP is less critical. The Rs are part of the filter, as opposed to the extra one in the HP to make them work at all.
Are yours 1st or 2nd order? 3nd order is not that good.
dave
An FMOD has a terminating resistor which greatly compromises the filter. For the HP, if you use the actual input impedance of your amplifier instead of the terminating resistir should open things up (we are talking about a single cap). LP is less critical. The Rs are part of the filter, as opposed to the extra one in the HP to make them work at all.
Are yours 1st or 2nd order? 3nd order is not that good.
dave
I apologize. I thought you could understand what I wrote. So in more detail for you, I used FMODs to get an idea of what cross over points I wanted to use. After actually listening to both the 12P and 12PW drivers with different sources, preamplifier's and power amplifiers in my actual room with an actual baffle, with and without FMODs, I decided I preferred the playback of the 12PWs, in combination or not conjunction with 12Ps.
Then I was surprised the differences I heard using them with 12Ps were not apparent with the 12PWs, so I decided not to proceed with making my own. The reason for this would be to avoid getting a speaker so awful sounding like my friend Martin's pair of walnut Onken style ones; they are so terrible he won't even raise their playback volume to the level of a whisper, even though they were largely designed by some guy and his software according to him.
So thanks anyways, I'll make my own speakers, use my own shortcuts, and leave you and Danny Richie to debate the applicability of capacitor and binding post differences to one another.
You added nothing except saying buy more parts and await delivery to see if they all arrive at once.
In that spirit, since you used the imperative form when stating I do something and it's my job because you said so, I return it to you and say- you posited it: you do it.
😅
Then I was surprised the differences I heard using them with 12Ps were not apparent with the 12PWs, so I decided not to proceed with making my own. The reason for this would be to avoid getting a speaker so awful sounding like my friend Martin's pair of walnut Onken style ones; they are so terrible he won't even raise their playback volume to the level of a whisper, even though they were largely designed by some guy and his software according to him.
So thanks anyways, I'll make my own speakers, use my own shortcuts, and leave you and Danny Richie to debate the applicability of capacitor and binding post differences to one another.
You added nothing except saying buy more parts and await delivery to see if they all arrive at once.
In that spirit, since you used the imperative form when stating I do something and it's my job because you said so, I return it to you and say- you posited it: you do it.
😅
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