Hi,
I'm planning to use active (digital) crossover for my DIY 3-way speakers, and is looking for suitable DIY power amps as well.
My speakers:
2x 8" bass in parallel; 4 ohms / 90 dB sensitivity
2x 3" midrange in series; 8 ohms / 89 dB sensitivity
1" tweeter; 6 ohms / 92 dB sensitivity
After some browsing I believe that LM3875:s for mid and tweeter and LM4780 (in parallel configuration) for the bass could be a good choice. Does this seem reasonable?
I don't have much experience of electronics so I'm looking for suitable kit solutions. There are several kits available on the internet, and since I can't judge about the design I'd like some recommendations/options on what to get (both for amps and PSU:s).
Best regards
I'm planning to use active (digital) crossover for my DIY 3-way speakers, and is looking for suitable DIY power amps as well.
My speakers:
2x 8" bass in parallel; 4 ohms / 90 dB sensitivity
2x 3" midrange in series; 8 ohms / 89 dB sensitivity
1" tweeter; 6 ohms / 92 dB sensitivity
After some browsing I believe that LM3875:s for mid and tweeter and LM4780 (in parallel configuration) for the bass could be a good choice. Does this seem reasonable?
I don't have much experience of electronics so I'm looking for suitable kit solutions. There are several kits available on the internet, and since I can't judge about the design I'd like some recommendations/options on what to get (both for amps and PSU:s).
Best regards
Yes !!!!
One amplifier to one speaker driver.
There is nothing to be gained by paralleling a pair of chipamps to drive a pair of paralleled speaker drivers.
Crumboo,
what are the impedances and sensitivities of the individual speaker drivers?
eg.
One amplifier to one speaker driver.
There is nothing to be gained by paralleling a pair of chipamps to drive a pair of paralleled speaker drivers.
Crumboo,
what are the impedances and sensitivities of the individual speaker drivers?
eg.
Is that 92dB/W @ 1m, or 92dB/2.83Vac @ 1m?
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Hi, I rechecked the driver specs:
Tweeter is 94.1 dB/2.83V @ 1m and nominal impedance is 6 Ohm
Midrange is 88 dB/2.83V @ 1m and nominal impedance is 4 Ohm
Woofer is 87 dB/2.83V @ 1m and nominal impedance is 8 Ohm
Measurements that I did actually showed that the sensitivity is actually about 89-90 dB/2.83V for the midranges though...
I obviously connected the woofers in parallel in order to increase the sensitivity, and connected the midranges in series (in parallel the impedance would be too low).
I figured that LM4780 in parallel mode should work fine for the woofers, since it would work with 4 Ohm impedance speakers. Also, I believe that LM4780 would give more power than a LM3875 or LM3886?
Do you think LM3875 would be powerful enough for driving the midranges? I like to play music loud...
By the way, the crossover points are at about 400 and 2500 Hz, with very steep filter roll-offs.I found Peter Daniels page, and this looks good since both LM3875 and LM4780 kits can be ordered there. I suppose he ships overseas?
If i'd use the LM3875 kits for driving tweeter and midranges, would dual-mono (using separate PSU:s) be preferred over the stereo config? Is it wise to use a common transformer for all three channels (tweeter, mid and woofer), of is it better to use separate transformers for each amp?
Any other/more suggestions?
Best regards
Here is a zoom in the XY PCB nearly inspired of Aguilabrava project.
An externally hosted image should be here but it was not working when we last tested it.
Peter Daniel makes a top class product and is a great guy to deal with.
I have purchsed several pcb's from him in the past, so yeah he is happy to ship overseas.
Just pay by paypal
In reality it's 3 stereo amps with a dual transfo power supply. What's wrong Andrew?
There is nothing wrong. He is congratulating you on your decision to triamp.
Nothing wrong.
But not about Tri-amp.
It's about one amplifier to drive one speaker.
I see in post5 the same mistake being repeated.
Drive each 8ohm bass driver with it's own 8ohms rated chipamp.
But not about Tri-amp.
It's about one amplifier to drive one speaker.
I see in post5 the same mistake being repeated.
There is absolutely nothing to be gained by driving a paralleled pair of speakers with a paralleled pair of chipamps.
Drive each 8ohm bass driver with it's own 8ohms rated chipamp.
I see now how you mean! The reason for the wiring is that the speakers previously (and still) have passive crossovers, and in that case it makes sense to parallel the woofers to get higher sensitivity.
Would it work to have a single LM3875 amp for each driver, i.e. 5 amps for each speaker in my case? How does this do with 4 Ohm drivers (the mids)?
Would it work to have a single LM3875 amp for each driver, i.e. 5 amps for each speaker in my case? How does this do with 4 Ohm drivers (the mids)?
On the other hand, it may be a problem to rewire the speaker drivers inside the speakers... So, even if nothing is gained by driving paralleled speaker with paralleled amps, there isn't anything wrong by doing so?
Maybe using LM4780 for both mids (in bridged mode) and woofers (in parallel mode) in order to deal with the mids lower sensitivity?
Maybe using LM4780 for both mids (in bridged mode) and woofers (in parallel mode) in order to deal with the mids lower sensitivity?
The two bass units can each be driven with a 68W into 8r0 8ohms capable chipamp.
The treble unit can be driven by by another 68W into 8r0 8ohms capable chipamp.
The problem with the mid drivers is their 4ohms rating.
You can either series connect them and use a 68W into 8r0 8ohms capable chipamp to allow ~34W to be delivered to each mid driver. Or drive each mid driver with a pair of paralleled chipamps that can operate from the same power supply as the other chipamps.
I would go for the simpler alternative, one chipamp into the series pair.
Now to peak output from each driver. 68W is equivalent to +18.3dBW
The bass units will reach a nominal 87+18.3 = 105.3dB from each. A pair will get an extra 3db due to the doubled power and a further 3dB due to the doubled Sd over a narrow frequency range. That frequency range is determined by the distance across the furthest spacing of the cones. The max SPL will be ~111dB
The treble unit will require the amplifier input to be attenuated by ~6dB.
The max SPL will be ~94+18.3-6 = 106dB, if the treble drive can accept 17W of maximum input as a low duty cycle transient.
The mid units will reach a nominal 88+18.3-3 = 103.3dB. A pair will be 3dB higher due to double the power. However some of the 3dB available due to the doubled Sd cannot be realised due to the distance across the two mid driver cones. Expect ~106dB
From this you can see that the drivers achieve 106dB maximum and a bit extra from the bass before they start to roll off.
In summary arrange attenuation of the treble amplifier and series connect the mid drivers.
All can now be driven by 68W chipamps. No paralleling (PA100) and no bridging (BA100) is necessary.
BTW,
your high efficiency treble driver could be driven with a 20W low noise amplifier, but this would need to be a discrete amp designed for low noise in comparison to the normal chipamps.
The treble unit can be driven by by another 68W into 8r0 8ohms capable chipamp.
The problem with the mid drivers is their 4ohms rating.
You can either series connect them and use a 68W into 8r0 8ohms capable chipamp to allow ~34W to be delivered to each mid driver. Or drive each mid driver with a pair of paralleled chipamps that can operate from the same power supply as the other chipamps.
I would go for the simpler alternative, one chipamp into the series pair.
Now to peak output from each driver. 68W is equivalent to +18.3dBW
The bass units will reach a nominal 87+18.3 = 105.3dB from each. A pair will get an extra 3db due to the doubled power and a further 3dB due to the doubled Sd over a narrow frequency range. That frequency range is determined by the distance across the furthest spacing of the cones. The max SPL will be ~111dB
The treble unit will require the amplifier input to be attenuated by ~6dB.
The max SPL will be ~94+18.3-6 = 106dB, if the treble drive can accept 17W of maximum input as a low duty cycle transient.
The mid units will reach a nominal 88+18.3-3 = 103.3dB. A pair will be 3dB higher due to double the power. However some of the 3dB available due to the doubled Sd cannot be realised due to the distance across the two mid driver cones. Expect ~106dB
From this you can see that the drivers achieve 106dB maximum and a bit extra from the bass before they start to roll off.
In summary arrange attenuation of the treble amplifier and series connect the mid drivers.
All can now be driven by 68W chipamps. No paralleling (PA100) and no bridging (BA100) is necessary.
BTW,
your high efficiency treble driver could be driven with a 20W low noise amplifier, but this would need to be a discrete amp designed for low noise in comparison to the normal chipamps.
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Thank you for a very informative response Andrew!
A couple of follow-up questions:
What nominal SPL could be achieved for the mids when using a bridged amp instead? Are there any drawbacks, except for price and complexity to build?
Are there any differences using parallel amps for the paralleled woofers instead of driving each woofer with a single amp (it would be nice to avoid rewiring the internal cables in the speakers if it can be avoided)? Any apparent downsides?
Do you know of any such kits available for a novice DIY:er?
Depending on amp configurations: can all amps be installed in a single box (thinking about the grounding)? Can all amps share the same PSU? Transformer?
Best regards
A couple of follow-up questions:
What nominal SPL could be achieved for the mids when using a bridged amp instead? Are there any drawbacks, except for price and complexity to build?
Are there any differences using parallel amps for the paralleled woofers instead of driving each woofer with a single amp (it would be nice to avoid rewiring the internal cables in the speakers if it can be avoided)? Any apparent downsides?
Do you know of any such kits available for a novice DIY:er?
Depending on amp configurations: can all amps be installed in a single box (thinking about the grounding)? Can all amps share the same PSU? Transformer?
Best regards
This setup will drive a normal passive crossover speaker and can use very short speaker cable, with longer interconnect. Remember the ~-6dB of attenuation for the Treble amplifier.
Alternatively, one can add active filters and appropriate EQ and turn this into an active set of speakers, or at some later date.
One slight problem. The bass drivers may run from just one section of 4ohm low pass filter. That would need to be modified to become two identical passive 8ohm low pass filters, one to each bass driver.
My preferred solution to this slight problem. Use one active low pass filter in front of the two bass amplifiers. Cheaper and probably easier than converting the 4ohm passive, to a pair of 8ohm ohm passive.
Alternatively, one can add active filters and appropriate EQ and turn this into an active set of speakers, or at some later date.
One slight problem. The bass drivers may run from just one section of 4ohm low pass filter. That would need to be modified to become two identical passive 8ohm low pass filters, one to each bass driver.
My preferred solution to this slight problem. Use one active low pass filter in front of the two bass amplifiers. Cheaper and probably easier than converting the 4ohm passive, to a pair of 8ohm ohm passive.
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Hi and thank you again!
It will be all active digital crossovers; that's the only reason for abandoning my present integrated stereo amp. The amps will be fed by a Buffalo III dac (8 ch).
The only thing that worries me now is that the mids (connected in series) won't be able to play loud enough when using a single chipamp (because of the low sensitivity). But it seems that you vote against using two amps bridged in this case?
And for my other question above: using a two amps in parallel for my paralleled woofers are equivalent to using a singe amp for each driver?
It will be all active digital crossovers; that's the only reason for abandoning my present integrated stereo amp. The amps will be fed by a Buffalo III dac (8 ch).
The only thing that worries me now is that the mids (connected in series) won't be able to play loud enough when using a single chipamp (because of the low sensitivity). But it seems that you vote against using two amps bridged in this case?
And for my other question above: using a two amps in parallel for my paralleled woofers are equivalent to using a singe amp for each driver?
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