That shouldn't be a problem as it'll need active bi-amping with a low XO - say 200 Hz.
The result may not be wonderful - yet will be better than the original Celestes - which is not difficult.
Active yes, just be aware that yours B139 is not very powerful, just 15W RMS.
Newer models are at least 50W RMS.
Newer models are at least 50W RMS.
This is a newer B139 from the 80s. Pay attention to the frequency range. It is practically useless above 500Hz, and the cut must be earlier, 300Hz max. Your B139 does not have to be like that, but there is no information anywhere on the net.
PS
If you combine them with a small FR driver, don't forget that FR must be in a separate box (1-2l for example) completely isolated from the B139.
PS
If you combine them with a small FR driver, don't forget that FR must be in a separate box (1-2l for example) completely isolated from the B139.
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@NIXIE62 this was the idea suggested by Dave. If it all goes badly then the separate FR box can be redeployed elsewhere - toilet, workshop - anywhere really. It would leave a large TL box specifically designed for a B139 - but at worst that could be deconstructed and the wood used elsewhere.
As you say the B139s are Mk2s - no proper measurements exist and they could well have changed over the years. So it's a gamble but there's nothing really lost by trying except my time.... and time in this part of Britain is flexible - it reminds me of Montenegro in that way. If you want something done urgently then the answer is 'prekosutra' (meaning, of course, some non-defined day in the medium future!)🙂
As you say the B139s are Mk2s - no proper measurements exist and they could well have changed over the years. So it's a gamble but there's nothing really lost by trying except my time.... and time in this part of Britain is flexible - it reminds me of Montenegro in that way. If you want something done urgently then the answer is 'prekosutra' (meaning, of course, some non-defined day in the medium future!)🙂
"prekosutra" = the day after tomorrow. 🤣
If we were closer, I would easily measure it. That's 15 minutes of work all together. It is impossible that there is no one near you from diyaudio.com who has some measuring equipment. Maybe some good soul will call you. 🤔
If we were closer, I would easily measure it. That's 15 minutes of work all together. It is impossible that there is no one near you from diyaudio.com who has some measuring equipment. Maybe some good soul will call you. 🤔
I have no idea if there is someone near. Believe me, we live in the **** end of the back of beyond - a very forgotten part of Britain with no trains, one bus a week and a school with 20 pupils. It's great if you like isolation - and most of the time I'm fine with that but it does mean that the nearest person who shares a common obsession may be 2 hours away!
Actually I'm thinking of getting measuring equipment next year ('sutra' in other words!!)
Actually I'm thinking of getting measuring equipment next year ('sutra' in other words!!)
Well, based on your description of the location, it's unlikely that there's anyone there with equipment. 🤔
For that matter:
https://www.parts-express.com/Dayto...udio-Component-Test-System-390-807?quantity=1
https://www.parts-express.com/Dayton-Audio-UMM-6-USB-Measurement-Microphone-390-808?quantity=1
For that matter:
https://www.parts-express.com/Dayto...udio-Component-Test-System-390-807?quantity=1
https://www.parts-express.com/Dayton-Audio-UMM-6-USB-Measurement-Microphone-390-808?quantity=1
The USB microphone is easy to use. Measuring TS parameters is a bit more complicated, but nothing terrible. When I mastered it, anyone can. 🤣
Besides there being no standards for poower ratings, so they cannot be directly compared.
Further, in most domestic hifi situationa power handling is irrelevant.
dave
You are right about standards, but the B139 power ratings of the various versions are from the same factory, I assume they use the same methods.
Power handling does not matter much for normal listening, where the average is a few W, except for parties. 🤣
Power handling does not matter much for normal listening, where the average is a few W, except for parties. 🤣
Power handling matters when it is very low like 15W (or 5W like the proposed wideband driver) because it limits clean transients and drivers operating near their power limits in use get warm, move away from their designed operating conditions and distort more. The new B139 has actually been modified (making it not strictly a B139) to raise the power limit to 150W indicating just how serious a limitation it was considered to be these days compared to the 60s with 10W amplifiers. In the OPs case the proposed wideband driver has even lower power handling so it is unlikely to be much of a constraint on the speakers overall power handling which will be very low compared to modern high fidelity speakers. Given the lowish sensitivity it will only be clean at quiet levels but likely not much worse than the original and so if that was OK in this respect in the OPs room then the new one likely will be.
Like tweeters and midranges, a small FR driver will be able to receive low power if low frequencies are fed to it, and the diaphragm travel will be too large. If you cut it off with at least a second-order crossover at a few hundred Hz, it will withstand much higher power. Distortions are also related to the movement of the membrane, so it will also be smaller.
As far as the heating of the coil is concerned, the average power supplied is important, and it is relatively small during normal listening. However, on stronger impulses, and music is exactly that, there will be an increase in distortion.
In the case of this combination, the B139 does not have the required range and has breakup modes in the low range, and the T15 mid/high driver is not up to the task of working with the B139, i.e. it is already cut too low. A small FR driver (2-3"), cut at 300-400Hz would certainly give a better result. Just that it's not too efficient, that it doesn't have to be damped by the L pad too much. In addition, the smaller FR driver has better dispersion at high frequencies.
Visaton B80 8ohm seems like a good choice to me, cheap, fairly linear on axis, with coated paper membrane and 85-87db 1W 1m efficiency. Ideally, the cut should be somewhere where there is also a baffle step transition. The rising FR range can probably be corrected a bit by damping in the box.
As far as the heating of the coil is concerned, the average power supplied is important, and it is relatively small during normal listening. However, on stronger impulses, and music is exactly that, there will be an increase in distortion.
In the case of this combination, the B139 does not have the required range and has breakup modes in the low range, and the T15 mid/high driver is not up to the task of working with the B139, i.e. it is already cut too low. A small FR driver (2-3"), cut at 300-400Hz would certainly give a better result. Just that it's not too efficient, that it doesn't have to be damped by the L pad too much. In addition, the smaller FR driver has better dispersion at high frequencies.
Visaton B80 8ohm seems like a good choice to me, cheap, fairly linear on axis, with coated paper membrane and 85-87db 1W 1m efficiency. Ideally, the cut should be somewhere where there is also a baffle step transition. The rising FR range can probably be corrected a bit by damping in the box.
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USB mics are most definitely not recommended, since you can't do a two channel measurements.
Which is needed to get a proper phase reference.
Just get a cheap 2 channel audio interface with phantom power.
For impedance measurement, you just need one simple 27 ohm (or so) reference resistor plus some wires to that audio interface.
Just find a 2nd hand amplifier somewhere.
Which is needed to get a proper phase reference.
Just get a cheap 2 channel audio interface with phantom power.
For impedance measurement, you just need one simple 27 ohm (or so) reference resistor plus some wires to that audio interface.
Just find a 2nd hand amplifier somewhere.
If you still think about 3-way, which would be my choice, Monacor SPH-135/AD is considered as best reasonably priced alternative for B110.
But taking into account you have older and lower powered variant of B139, smaller Monacor SP-100/8 might be a better match (and even more affordable). As midrange, SP-100/8 can work in very small closed chamber, 2 liters or even less.
Both are easily available in UK, latter one from Farnell for eg.
For crossover and taking into account low resonance of T15 tweeter and fairly smooth response of those Monacor drivers, I would go 1st order 3500-4000Hz, depending on midrange size.
Between B139 and midrange, 2nd order 400Hz.
Unfortunately, data for your drivers are scarce. All I manage to find is this brochure. It seems like your speaker was offered as kit too.
It says 15 Ohm impedance for both drivers, so at least you must do is to take a multimeter and measure DC resistance of drivers coils. Simple crossover can be made "by ear" but we must know correct nominal impedance.
If measures something like 12-14 Ohm DC, driver is 15 Ohm impedance. If 6-7 Ohms DC, than its 8 Ohm impedance.
But taking into account you have older and lower powered variant of B139, smaller Monacor SP-100/8 might be a better match (and even more affordable). As midrange, SP-100/8 can work in very small closed chamber, 2 liters or even less.
Both are easily available in UK, latter one from Farnell for eg.
For crossover and taking into account low resonance of T15 tweeter and fairly smooth response of those Monacor drivers, I would go 1st order 3500-4000Hz, depending on midrange size.
Between B139 and midrange, 2nd order 400Hz.
Unfortunately, data for your drivers are scarce. All I manage to find is this brochure. It seems like your speaker was offered as kit too.
It says 15 Ohm impedance for both drivers, so at least you must do is to take a multimeter and measure DC resistance of drivers coils. Simple crossover can be made "by ear" but we must know correct nominal impedance.
If measures something like 12-14 Ohm DC, driver is 15 Ohm impedance. If 6-7 Ohms DC, than its 8 Ohm impedance.
@Davor D , I don't know about the two microphones if they are really necessary. I have a DIY measuring system for about 15 years, which still serves me well. There is a Panasonic WM61A capsule, battery mic. preamplifier with two gain levels for nearfield/farfield measurements, small amplifier 10W - 8ohm, ARTA JIG for impedance and TS parameters, old laptop and external sound card (M Audio Transit). Because of the sound card, I still keep WIN7 on the laptop. I did a lot with it, both for myself and for others, making new speakers and remaking various factory speakers. Back then when I made it, there was no cheap ready-to-buy equipment like there is today. Still quite enough for my amateur needs.
The B139 has an impedance increase with frequency. It has to be linearized maybe before making the crossover. So impedance measurement is needed again. If it's nominal 15ohm, in the passive version it will be about 3dB quieter than the new 8 ohm mid/high driver just because of that. That could be solved by getting another pair of the same drivers and connecting them in parallel. Only the TL for two parallel drivers will be huge. 🤔
That's an approximation, the speaker is not a resistor. Twice the impedance means it draws half the power of a typical transistor amplifier he owns.
Kef says 8-16ohm impedance, don't know what that means until I measure.
Kef says 8-16ohm impedance, don't know what that means until I measure.
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Exactly, so this calculation doesn't say much.
Although the drivers efficiency is inversely proportional to the Re, the BL doesn't stay the same either.
Depending how a 16 ohm coil is made, the BL can actually be higher.
Since the efficiency is proportional to BL^2, it could be more.
Or sometimes the Mms will be different as well. Since that is also squared, there is no direct way of telling.
In practice, I have seen plenty of 16 ohm drivers that have an higher efficiency - > sensitivity.