Dear All!
This is first time I designed acoustic system for monitoring purposes.
Speaker is Dayton rs100-8, 4". It can handle 30watt rms max, and 60 watts at peak.
Also it has very good frequency response curve (dunno how close real speaker is to that curve).
Here is calculation of frequency response in cabinet at zero degrees:
So, to achieve better results, I decided to involve passive filters to flatten FR.
Filters from left to right - Notch filter around 3,3khz, baffle step correction, Notch filter around 17khz.
So the problem I faced - which power rating components to choose in this circuit. Maximum power intended to use here - 20watts.
Does it mean that resistors must have 20watt rating (or better more), and inductors to be 2.5A plus?
I really don't want to have burning and smelling monitors 🙂
I would appreciate any constructive criticism. For example I'm not sure if impedance characteristics are good, also High end of FR has that spikes, and not drops smoothly. May it cause unwanted harmonics or something else? (I understand it is above hearing range 🙂 )
This is first time I designed acoustic system for monitoring purposes.
Speaker is Dayton rs100-8, 4". It can handle 30watt rms max, and 60 watts at peak.
Also it has very good frequency response curve (dunno how close real speaker is to that curve).
Here is calculation of frequency response in cabinet at zero degrees:
An externally hosted image should be here but it was not working when we last tested it.
So, to achieve better results, I decided to involve passive filters to flatten FR.
An externally hosted image should be here but it was not working when we last tested it.
Filters from left to right - Notch filter around 3,3khz, baffle step correction, Notch filter around 17khz.
An externally hosted image should be here but it was not working when we last tested it.
So the problem I faced - which power rating components to choose in this circuit. Maximum power intended to use here - 20watts.
Does it mean that resistors must have 20watt rating (or better more), and inductors to be 2.5A plus?
I really don't want to have burning and smelling monitors 🙂
I would appreciate any constructive criticism. For example I'm not sure if impedance characteristics are good, also High end of FR has that spikes, and not drops smoothly. May it cause unwanted harmonics or something else? (I understand it is above hearing range 🙂 )
Nice work! The RS100 has always been what I considered reasonably flat from the factory and you have added a new level of flat to it. Thanks!
It’s a small full range so don’t worry about the ratings. The resistors for crossover are commonly sold in 10w and 12w ratings. It’s dissipation in the resistor that’s what is important. In your crossover simulator program look for a power dissipation prediction. I doubt anything is more than a watt. You could get by with 3W metal thin film non inductive resistors used in amplifiers.
If you got to Parts Express, their standard white cement filled unit is $0.59 and in 10W. That will work fine. For the inductor, depending on the DCR you need but 18ga or 20ga air core is fine.
It’s a small full range so don’t worry about the ratings. The resistors for crossover are commonly sold in 10w and 12w ratings. It’s dissipation in the resistor that’s what is important. In your crossover simulator program look for a power dissipation prediction. I doubt anything is more than a watt. You could get by with 3W metal thin film non inductive resistors used in amplifiers.
If you got to Parts Express, their standard white cement filled unit is $0.59 and in 10W. That will work fine. For the inductor, depending on the DCR you need but 18ga or 20ga air core is fine.
that is very nice - how does the prediction change say using Dayton 20 gauge air core inductor DCR values?
xrk971, thank you!
I just checked out Parts Express, and they have everything for this network.
Never thought that air core coil might cost that much, but it's ok 😀
I will do some tests, it should theoretically work good ( I'm not sure how THD % will raise). On other forum, I got suggestuion to use line level active filters.
It's more complicated, and will add unwanted noise. But the damping factor will not fall. It's interesting which solution will work best here.
I just checked out Parts Express, and they have everything for this network.
Never thought that air core coil might cost that much, but it's ok 😀
I will do some tests, it should theoretically work good ( I'm not sure how THD % will raise). On other forum, I got suggestuion to use line level active filters.
It's more complicated, and will add unwanted noise. But the damping factor will not fall. It's interesting which solution will work best here.
Line level filters need to be designed for a specific input impedance of an amp and cannot be used with other amps unless a buffer opamp stage is used to isolate it. I find LL filters more of a hassle and it’s much more convenient to keep filters with the speaker. Let’s you use it with any amp and anywhere. You might be be to use an iron plate core inductor to save volume and money. They can sound very good too. 1.7mH is not too big of a value.
Attachments
Slightly higher DC resistance you need to plug into your simulator. It will change the Q of each filter slightly. Always use the DCR in the simulator.
I would see what could be done with that 300 Hz hump. Just enough to be audible I suspect. Listening is the truth though. Personally, I would add a Zobel to take that top end under control.
I assume a ported cab by the impedance curve, so I might put a "rumble filter" in the preamp or a very large cap on the input to protect it from any large low freq signal. pretty small X-Max on it.
Nice little driver, but pay attention to the cone breakup. It may measure flat at low power, but the cone breakup gets manifested through IM to be plain old harmonic distortion down in the critical range.
I agree, too much nuances here, and high risk to get noizy circuit.
I prefer to specify actual dc resistance of component which will be used by the fact. It helps to see how it affects "ideal" or "project" specifications.
Yeah. By my opinion, if density of the frequencies segment above 500hz is approximately equal to density of that hump, it may not require correction.
At least I hope so 🙂 I can upload frequency response in CSV file here, if someone interested.
Right, this is ported cab design.
Thanks for suggestions! I decided to try all options available.
Thanks!
I will try it definitely.
Update!
We finished assembling these reference monitors.
Yesterday I did measurements using Sonarworks microphone.
The frequency response of whole Box+speaker amazed me. But there is strange dependence of non-linearities and distance from speaker.
When it raises, then responce curve goes more nonlinear. I think that happens because we measure it in real room - reflections and standing waves may affect signal, as result we're getting false readings.
Anyway, I think this project is successfull.
I attached graph to this post, which compares Project nonlinearities with real measurements.
Red curve - simulated response. Black - real. !!! Correction EQ not used in this setup !!!
20watt AB class amplifier was used during measurements, focusrite 2i2 usb interface, sonarworks mic.
Here is comparison with Tannoy Reveal 502:
Monitors still need to be improved. Correction EQ required to remove that two bumps. Linearity was our mission, and more is more? Right? I think we will made this project opensource, when I will re-measure precisely everything, and squeeze the maximum of it. What you think?
We finished assembling these reference monitors.
Yesterday I did measurements using Sonarworks microphone.
The frequency response of whole Box+speaker amazed me. But there is strange dependence of non-linearities and distance from speaker.
When it raises, then responce curve goes more nonlinear. I think that happens because we measure it in real room - reflections and standing waves may affect signal, as result we're getting false readings.
Anyway, I think this project is successfull.
I attached graph to this post, which compares Project nonlinearities with real measurements.
Red curve - simulated response. Black - real. !!! Correction EQ not used in this setup !!!
20watt AB class amplifier was used during measurements, focusrite 2i2 usb interface, sonarworks mic.
Here is comparison with Tannoy Reveal 502:
Monitors still need to be improved. Correction EQ required to remove that two bumps. Linearity was our mission, and more is more? Right? I think we will made this project opensource, when I will re-measure precisely everything, and squeeze the maximum of it. What you think?
Attachments
No, not necessarily. There is a limit to what you can do, and even need to do about your "apparent" room issues with EQ.
I agree. Room accoustics is very important. But why not implement correction network, If it would make this system little bit better?
I choose active correction ( low cost, more flexibility )
Our room requires serios accoustic treatment. But still...
Values on curves are not approximated. While response is better than commercially made, non expensive monitors. If I minimize deviation from mean value, It will bring our build closer to very expensive models on the market.
I choose active correction ( low cost, more flexibility )
Our room requires serios accoustic treatment. But still...
Values on curves are not approximated. While response is better than commercially made, non expensive monitors. If I minimize deviation from mean value, It will bring our build closer to very expensive models on the market.
Sure, some room issues are improved that way. You'll likely find the result isn't too bad. There's more going on than the straight line is able to tell you.
What Allen said.
The microphone does not have a brain, and while our brains frequently get in the way, they often adjust to a room's acoustics, at least partially.
We get a sense of what to expect a room to do to the sound, and many of the less violent changes are EQed in our heads, so we only need to work on the worst.
The microphone does not have a brain, and while our brains frequently get in the way, they often adjust to a room's acoustics, at least partially.
We get a sense of what to expect a room to do to the sound, and many of the less violent changes are EQed in our heads, so we only need to work on the worst.
Looks very nice. Generally I measure at 0.5m with speaker 1m above floor and 6 cycle frequency dependent window (FDW) to remove room reflection effects.
I generally like about a -5dB tilt down to the right. That is, 20kHz is about -5dB less than SPL at 100Hz. This gives a more pleasing and less harsh presentation. It’s what has been identified by Harman as pleasing to most listeners. I find that it is true. If a speaker is perfectly flat - it will sound too bright.
The easy way to do this to increase the BSC resistor. In your circuit, adjust the 5.6ohm that’s in parallel with the 1.7mH. Maybe 6.8ohm?
I usually just use 1mH and 6.8ohm (For 8ohm driver) and nothing else and it will apply the baffle step correction shelf to do what you need.
I generally like about a -5dB tilt down to the right. That is, 20kHz is about -5dB less than SPL at 100Hz. This gives a more pleasing and less harsh presentation. It’s what has been identified by Harman as pleasing to most listeners. I find that it is true. If a speaker is perfectly flat - it will sound too bright.
The easy way to do this to increase the BSC resistor. In your circuit, adjust the 5.6ohm that’s in parallel with the 1.7mH. Maybe 6.8ohm?
I usually just use 1mH and 6.8ohm (For 8ohm driver) and nothing else and it will apply the baffle step correction shelf to do what you need.