Hello everyone! I've been in the need for a really good nearfield monitor speaker. I wanted it very compact and active. Also, it had to play at decent max SPL (around 90/93dB at 1 meter) in case I wanted it to fill my room. The FR had to be from 50 to 10000Hz (+-2dB) on axis.
For this reason my choice landed on the Dayton RS100-4 for its decent FR and good Xmax which is never enough for small drivers! The efficency is also decent with it being a 4ohm unit.
The FR doesn't quite meet the requirements but it seems like it can be EQd quite easily. I'll get a Sure JAB3-50 (it has a built in DSP) module to drive the speakers. Since I'm using DSP, I'll be making the speaker bass reflex because that way I can make an assisted alignment, also it's way more efficient than sealed.
3.6L net volume tuned to 55Hz with 2nd order HP filter (Fc=55Hz and Q=1,2) yelds to an almost perfect response. The SPL is also more than enough. This is the green graph.
But, in reality, tuning a small box so low is hardly feasible unless making a slotted port which comes with its own set of problems... mainly being much less efficient in terms of space and it also has higher losses thus lower efficency. If I use a round port I could make the box very tall and put the vent on the bottom, even if that wouldn't be very practical. Think about 11*14*25cm(3,85L). Even then I'd be limited to a 3,5cm port with a lenght of 24cm. This port has an airspeed of 31m/s (!!!) at 49Hz, with 30W input (not very realistic but I'd like to properly size the port), which is too high! I have to limit the power to 9W in order to stay at 17m/s.
So I started experimenting with passive radiators in WinISD, which also have their own sets of drawbacks, mainly the way lower efficency leading to a significantly lower max SPL (-2dB)!!! The two "best" radiators I could find for the price were the Dayton Audio ND140PR and the DSA135PR.
I put them in the same volume (3,6L) and tuned the enclosure to match the ported one (around 55Hz Fb).
The ND135PR required +18g (!) of added mass to tune at that frequency. I'm worried this might sag the suspension long-term. This is the blue graph.
The DSA135PR just +2g. With 30W input i'm VERY close to the 8mm Xmax for the DSA passive radiator but, between all the other problems, I could deal with this, if it wasn't for the massive loss in efficency. This is the red graph. I think this might be the best compromise, because even if I compare it with the ported version I'd be SPL limited way sooner because of that crazy high port velocity. Also I don't have to deal with chuffing.
The graphs do not include the filter.
How can I impove this design? Which one do you think is the best compromise? I would really like to keep the efficency of the ported enclosure without having to deal with the excessive port velocity. Do you think a slotted port would really help, even if it would make the box bigger? Thanks a lot!
For this reason my choice landed on the Dayton RS100-4 for its decent FR and good Xmax which is never enough for small drivers! The efficency is also decent with it being a 4ohm unit.
The FR doesn't quite meet the requirements but it seems like it can be EQd quite easily. I'll get a Sure JAB3-50 (it has a built in DSP) module to drive the speakers. Since I'm using DSP, I'll be making the speaker bass reflex because that way I can make an assisted alignment, also it's way more efficient than sealed.
3.6L net volume tuned to 55Hz with 2nd order HP filter (Fc=55Hz and Q=1,2) yelds to an almost perfect response. The SPL is also more than enough. This is the green graph.
But, in reality, tuning a small box so low is hardly feasible unless making a slotted port which comes with its own set of problems... mainly being much less efficient in terms of space and it also has higher losses thus lower efficency. If I use a round port I could make the box very tall and put the vent on the bottom, even if that wouldn't be very practical. Think about 11*14*25cm(3,85L). Even then I'd be limited to a 3,5cm port with a lenght of 24cm. This port has an airspeed of 31m/s (!!!) at 49Hz, with 30W input (not very realistic but I'd like to properly size the port), which is too high! I have to limit the power to 9W in order to stay at 17m/s.
So I started experimenting with passive radiators in WinISD, which also have their own sets of drawbacks, mainly the way lower efficency leading to a significantly lower max SPL (-2dB)!!! The two "best" radiators I could find for the price were the Dayton Audio ND140PR and the DSA135PR.
I put them in the same volume (3,6L) and tuned the enclosure to match the ported one (around 55Hz Fb).
The ND135PR required +18g (!) of added mass to tune at that frequency. I'm worried this might sag the suspension long-term. This is the blue graph.
The DSA135PR just +2g. With 30W input i'm VERY close to the 8mm Xmax for the DSA passive radiator but, between all the other problems, I could deal with this, if it wasn't for the massive loss in efficency. This is the red graph. I think this might be the best compromise, because even if I compare it with the ported version I'd be SPL limited way sooner because of that crazy high port velocity. Also I don't have to deal with chuffing.
The graphs do not include the filter.
How can I impove this design? Which one do you think is the best compromise? I would really like to keep the efficency of the ported enclosure without having to deal with the excessive port velocity. Do you think a slotted port would really help, even if it would make the box bigger? Thanks a lot!
The first alignment i do not like, but is often used (and makes people happy).
The second one is just ugly.
Power got shut off last nite, need to go downstairs and turn the sim computer back on. I’ll have a look at teh driver later.
dave
The second one is just ugly.
Power got shut off last nite, need to go downstairs and turn the sim computer back on. I’ll have a look at teh driver later.
dave
Thank you.
Forgot to say that the alignment I uploaded didn't include the highpass filter for the equalization.
This is the graph plotted with the filters included.
The green one has a 2nd order HP at 55Hz Q=1,2. The Blue and red one both have an HP with Fc of 56Hz and Q=1,3
If I want to make a squared slotted port, what would be a Ql value that best approximates the one of a finished port?
EQ on which alignmenht. I strongly suspect you wil hear the artifacts of the poor alignment. What does teh EQ look like?
If you are EQin why not just sealed?
If you are EQin why not just sealed?
Q l is a loss factor?
The slot vent is intended to have significant resistance so probably a lot of losses.
dave
The slot vent is intended to have significant resistance so probably a lot of losses.
dave
Adding a lot of mass to small passive radiators tends to decrease their output. It can cause excessive radiator excursion as well, so keep an eye on that.
The overall alignment/response shape may be significantly different from one passive radiator model to another. The passive has its own set of parameters that may or may not be synergistic with your design. I normally model multiple configurations before landing on one I like (on a project like this I would shoot for minimal added mass).
And as planet10 suggested, unless I have a good reason to deviate from it, I tend to shoot for a response curve that matches an optimal bass reflex alignment.
Unfortunately, I haven't used the driver you're interested in, so I can't give you any specific recommendations.
It's a custom alignment. It's not far off from an extended bass shelf (-3db) alignment, with slighly smaller volume and higher tuning frequency.
The EQ looks like this. This also serves the purpose of limiting excursion:
And this is the group delay of the entire system speaker+filter:
I don't want to use a sealed enclosure because since the driver is very small and I need a way to increase the efficency, and I also need a "brake" on the excursion of the driver... I can achieve this only with a bass reflex enclosure.
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Yes. I was worried about this. If I increases the losses on the bass reflex simulation the efficency of the system matches the one of the passive radiator so doesn't make much sense to go that way.
Thank you! The alignment I choose is very similar to an extended bass alignment. Do you think that there are any other passive radiators I can try in this configuration? The DSA135 seems to work pretty well but I could try some more configurations! I've also tried the SB Acoustics SB13PFCR-00 but it doesn't model as well as the DSA135.
And the EQ.
BR does not bring more effiicency, only greater gain at lower frequencies. The trade off for that gain is the unloading below box tuning.
dave
BR does not bring more effiicency, only greater gain at lower frequencies. The trade off for that gain is the unloading below box tuning.
dave
What you get from the losses is better quality bass, more finesse, less sensitivity to dynamic (& unit) T/S variations. Quality over quantity, i do. otlike PRs,, don’t use them.
dave
I meant that a bass reflex enclosure can make the same amount of bass with smaller cone movement compared to a sealed box, above tuning frequency. That's what I'm after. In this case, under the tuning frequency the speaker is protected by the high-pass.
Kind of like aperiodic enclosures! I love those, but for such a small speaker I think I'm willing to make the sacrifice in order to have some bass extension. If I do not like how it sounds I could also add more polyfill to increase the losses.
I just ran through a few on Parts Express, and the DSA135 seems like a better option than the others, so you may have already hit the sweet spot given the overall configuration. 👍
In my experience, sometimes passive radiators just don't do what you want them to. In very small enclosures they are often the only option though, so it can make sense to take what they give you. I don't consider 3.5 liters very small though.
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120 cm of 3” abs pipe in and offset entry TL with offset port exit stuffed , etc
i used 2 rs100s-8 mtm with a peerless tweeter. ugly fun with poop pipe
i used 2 rs100s-8 mtm with a peerless tweeter. ugly fun with poop pipe
You try to tune a driver lower the wrong way for in good sound i think. Planet10's design is way more reasonable. The best i can get out of it is this, a 5L cabinet tuned to 55Hz. The port is also a bit resistive which helps (just like Planet10's design) with the bass. Passive radiators are good for subwoofers, but not that high up in frequency. You can make it more resistive by putting some damping in the port to make the speaker act more as aperiodic, which may also help with the bass response. That is hard to sim, so it's more trial and error to get it right.
Hello! I realize I have caused a bit of confusion, I went too far and I've actually lost track of what my goals for this project were. I want an compact high SPL solution for a really tiny woofer that can also play low. Sometimes I get a bit carried away🙂
Since I'm using a DSP, in my eyes it makes sense to use to make a 6th order assisted alignment (like this). In order to achieve this, I'm willing to make some sacrificies. I think regular BR sounds fine to me, even the so called "underdampened" alignments don't bother me too much and this seem pretty good.
My design with the PR is less efficient and more expensive and it has less room for error than the one made by waxx which is great and meets all my requirements but it is too big. I agree, doesn't make much sense to use a passive radiator.
I'm looking to make a small speaker that I can put on my desk and take with me whenever I need to.
4L is already "big", but manageable.
However if I want to make a 4L enclosure, I have either to raise the Fb to 60Hz which yields to an F-3 of 55Hz to keep a flat response, or keep the Fb at 55Hz and assist it with a high-q 2nd order high pass filter.
This will give me an F-3 of 50Hz with the added bonus of reducing cone excursion below Fb. This is a 6th order assisted bass reflex alignment instead of a "regular" 4th order.
The only way to fit these "ports" is to make the speaker a small tower (size 11x44x15cm) and put a 47mm port on the bottom. It's less practical, but then I could still fit the speakers in my backpack if I need to.
The port could then be round instead of squared in order to have low losses. For this project I want to maximize the efficency to squeeze the most out of a small driver. Or there still are "better" ways to go?
Since I'm using a DSP, in my eyes it makes sense to use to make a 6th order assisted alignment (like this). In order to achieve this, I'm willing to make some sacrificies. I think regular BR sounds fine to me, even the so called "underdampened" alignments don't bother me too much and this seem pretty good.
My design with the PR is less efficient and more expensive and it has less room for error than the one made by waxx which is great and meets all my requirements but it is too big. I agree, doesn't make much sense to use a passive radiator.
I'm looking to make a small speaker that I can put on my desk and take with me whenever I need to.
4L is already "big", but manageable.
However if I want to make a 4L enclosure, I have either to raise the Fb to 60Hz which yields to an F-3 of 55Hz to keep a flat response, or keep the Fb at 55Hz and assist it with a high-q 2nd order high pass filter.
This will give me an F-3 of 50Hz with the added bonus of reducing cone excursion below Fb. This is a 6th order assisted bass reflex alignment instead of a "regular" 4th order.
The only way to fit these "ports" is to make the speaker a small tower (size 11x44x15cm) and put a 47mm port on the bottom. It's less practical, but then I could still fit the speakers in my backpack if I need to.
The port could then be round instead of squared in order to have low losses. For this project I want to maximize the efficency to squeeze the most out of a small driver. Or there still are "better" ways to go?
I built the TABAQ years ago with that driver. It sounds excellent, even with the less than stellar top end of the rs100. I’d consider the folded TABAQ as a viable option for your needs.