I just got my hands on a set of Ciare 15 NDH 4S.
They will be used as subwoofers, covering up to 200 Hz.
The rest of the speaker system is placed directly on top of the subwoofers.
Normally, I prefer closed enclosures, but this time, I will go for a ported system.
I assume that a 10 cm port is needed, but do I need one or two, to avoid port noise?
Will there be any disadvantages, if I place the port(s) in the front…..it will make things easier for me.
An alternative is bottom fired ports.
Does anybody have an idea about cabinet size, port dimensions/length? I get variouse suggestions, depending of the calculation program used.
Greetings from Denmark, and thank you all very much in advance for your inputs.
Michael
They will be used as subwoofers, covering up to 200 Hz.
The rest of the speaker system is placed directly on top of the subwoofers.
Normally, I prefer closed enclosures, but this time, I will go for a ported system.
I assume that a 10 cm port is needed, but do I need one or two, to avoid port noise?
Will there be any disadvantages, if I place the port(s) in the front…..it will make things easier for me.
An alternative is bottom fired ports.
Does anybody have an idea about cabinet size, port dimensions/length? I get variouse suggestions, depending of the calculation program used.
Greetings from Denmark, and thank you all very much in advance for your inputs.
Michael
Is this for home use or live sound? What are your tops? How low do you want it to go? How loud do you want it to get? What size enclosure can you live with?
This is my home system.
The tops are going to be replaced, but currently 2 x 5” Audiotechnology midranges, and a Scanspeak Beryllium tweeter.
They will be replaced with a 10” mid driver and a 1.4” top.
30-35 Hz will be enougjh for me, in 70-80 liters, du to limited space.
The tops are going to be replaced, but currently 2 x 5” Audiotechnology midranges, and a Scanspeak Beryllium tweeter.
They will be replaced with a 10” mid driver and a 1.4” top.
30-35 Hz will be enougjh for me, in 70-80 liters, du to limited space.
Depends very much how loud you want to drive the speakers.
I suggest to make one big port instead of two smaller ones (maximise cross section but keep surface low for minimal noise).
Rectangular ports are ok while they also increase surface slightly.
The port edges (ends) are the main source of noise. So include big roundovers.
And have a look at my port noise and resonance thread:
https://www.diyaudio.com/community/...-port-resonance-absorbers.388264/post-7488331
More information will be updated soon!
Edit: i had very low (no) port noise with a flared, flanged port with roundovers, smooth interior surfaces and airspeeds below 12% of mach1 in the port center and below 5% mach1 at port ends. Detailled results in my thread - will follow during the next days!
Hornresp can simulate airspeed for straight tubes. Simulate for min. and max port cross section surface to check airspeeds. By the way mach1 = 340 m/s (on sea level)
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Here is about what you can expect with 80 liters (plus a little more for wood) with a 32Hz Fb (box tuning)
near Xmax:
Going to 140 liters gets more bottom with less power (about 522 watts compared to 722watts):
Thanks a lot, Weltersys!
I only got 200W available, from my Lyngdorf TDAI2200, and i assume, we are fair from dmaging the driver.
I have a setup with 3 TDAI 2200, running with electronic crossovers.
What port diameter/length did you get?
I only got 200W available, from my Lyngdorf TDAI2200, and i assume, we are fair from dmaging the driver.
I have a setup with 3 TDAI 2200, running with electronic crossovers.
What port diameter/length did you get?
The Hornresp input screen shown in Art's (Weltersys's) post gives you the vent cross sectional area as "Ap" and length as "Lp"; so 160cm^2 = 14.27cm diameter, and 53.2cm long. That will assume "standard" end correction, meaning it's valid for a port having one end flush with the outside of the box and the other end well away from any internal wall or panel inside the box.
As you will find if you do any modelling yourself, tuning a small box low very rapidly results in a port that is long relative to the box dimensions. This may require bending the vent, changing to a corner or shelf style vent or even moving to a passive radiator instead of a vent.
As you will find if you do any modelling yourself, tuning a small box low very rapidly results in a port that is long relative to the box dimensions. This may require bending the vent, changing to a corner or shelf style vent or even moving to a passive radiator instead of a vent.
A little bit more information……
I made some rough cabinet drawings, and I need to stay within 90 litres of volume.
The requested tuning frequence should be 35 Hz.
As menationed, i get various results, depending of the SW used to calculate the port.
Speakerbuilder 2.0 gives a length of 18 cm/diameter 10 cm.
I am fully aware that I might need some test, of course.
I plan to place the port down, towards the floor.
I made some rough cabinet drawings, and I need to stay within 90 litres of volume.
The requested tuning frequence should be 35 Hz.
As menationed, i get various results, depending of the SW used to calculate the port.
Speakerbuilder 2.0 gives a length of 18 cm/diameter 10 cm.
I am fully aware that I might need some test, of course.
I plan to place the port down, towards the floor.
Putting the port down towards the floor will lower the tuning unless the cabinet is sitting about double the port diameter off the ground. That's a waste of space that could be used inside the undersized (for a 32-25Hz Fb) cabinet. A slot port on the bottom of the cabinet with an "L" going up would work well. Slot ports can be flared to reduce noise with a roundover or a 45 degree angle.
With only 200 watts a 10cm, (only 4") diameter port may not chuff, but going with a larger port volume will allow around 6dB more level if you upgrade your amp at some time. At 35Hz that would sound about twice as loud to your ear.
With only 200 watts a 10cm, (only 4") diameter port may not chuff, but going with a larger port volume will allow around 6dB more level if you upgrade your amp at some time. At 35Hz that would sound about twice as loud to your ear.
This is actually a really good idea….I did not think about that!
If I calculate 90l/35Hz, with port diameter of 15 cm, I get a length of app 37 cm.
I guess, I just re-calculate the area of the port, and re-calculate the square are of the slot.
If I install the slot port below the driver, I can adjust/slide back/forth, and find the optimal length after tests.
If I calculate 90l/35Hz, with port diameter of 15 cm, I get a length of app 37 cm.
I guess, I just re-calculate the area of the port, and re-calculate the square are of the slot.
If I install the slot port below the driver, I can adjust/slide back/forth, and find the optimal length after tests.
OK, finally, I found some time for this project……
I decided to go for a slot port, but I have doubts about the dimensions?
Do we have a rule of thumb, regarding the ratio between with and hight the port?
I was told that I will need a port, which is about 15 cm in diameter (round port) to avoid too much port noise.
This equals a slottet port of i.e. 7 cm x 25 cm. Length depends on the size of the box.
What do you think about this?
I have limited space, and cannot exceed 80-90 liters of enclosure volume.
It is difficult for mee, to figure out, what is the consequence of the box volume, as long as the length of the adapts to the volume?
A smaller box will, of course be cheaper to build, and easier to handle.
What do you think?
My plan is therefore as follows:
Box volume: 80 liter net.
Port diameter: 7x25 cm
Port length: 30 centimeters.
Cross over 200 Hz, electronic via my Lyngdorf Amp.
How does it sound?
I decided to go for a slot port, but I have doubts about the dimensions?
Do we have a rule of thumb, regarding the ratio between with and hight the port?
I was told that I will need a port, which is about 15 cm in diameter (round port) to avoid too much port noise.
This equals a slottet port of i.e. 7 cm x 25 cm. Length depends on the size of the box.
What do you think about this?
I have limited space, and cannot exceed 80-90 liters of enclosure volume.
It is difficult for mee, to figure out, what is the consequence of the box volume, as long as the length of the adapts to the volume?
A smaller box will, of course be cheaper to build, and easier to handle.
What do you think?
My plan is therefore as follows:
Box volume: 80 liter net.
Port diameter: 7x25 cm
Port length: 30 centimeters.
Cross over 200 Hz, electronic via my Lyngdorf Amp.
How does it sound?
A higher aspect ratio (wide, thin) port will tune a bit lower than a circular port of the same length.
Port end correction factor “K” value increases from a standard value of 0.732 when a port is not located some distance from cabinet side walls. When a side, or sides of an enclosure are used as a port wall in square, rectangular or triangular ports, the port length is effectively made longer by the additional mass of air adjacent to the walls, so a port centered on one wall has a higher “K” value than if it were away from all walls, adjacent to two walls, higher yet, three walls still higher.
I think the larger (around 175 square cm compared to 160), shorter (30cm compared to 53cm) port in an 80L net box will result in an Fb (box tuning) of ~42.4 Hz, quite a bit above your 30-35 Hz goal previously stated.
Response will be around -3dB at 48Hz.
The higher Fb results in a flatter response, but around -5dB less output at 30Hz:
30Hz would sound less than half as loud with the 42Hz as it would with the 32Hz tuning.
Art
Attachments
Thanks for this valuable information!
It is a bit triggy to calculate…….
I have the possibility to make an adjustable port, and “slide” it in the cabinet.
This probably makes sense, since internal volume might differ, depending on the internal bracing, damping material etc.
I plan to order a Dayton Dats v3 to check the system.
I need to stick to 25cm with of the port, due to reasons, impossible to explain here…..pictures will come later ☺️
Do I understand you correct: you recommend a slighly smaller diameter (6,4 cm hight, instead of 7 cm), and a longer port, 53 cm versus 30 cm??
I may come pretty close to the back wall inside the cabinet, but I can make it a bit deeper, if needed.
It is a bit triggy to calculate…….
I have the possibility to make an adjustable port, and “slide” it in the cabinet.
This probably makes sense, since internal volume might differ, depending on the internal bracing, damping material etc.
I plan to order a Dayton Dats v3 to check the system.
I need to stick to 25cm with of the port, due to reasons, impossible to explain here…..pictures will come later ☺️
Do I understand you correct: you recommend a slighly smaller diameter (6,4 cm hight, instead of 7 cm), and a longer port, 53 cm versus 30 cm??
I may come pretty close to the back wall inside the cabinet, but I can make it a bit deeper, if needed.
The port will tune to almost the same Fb if it's length, in or out of the cabinet remains the same.
To make a variable tuning port, it would have to be constructed like an old fashioned telescope, sliding sections of itself in and out.
I didn't actually make a recommendation, just pointed out that you trade low frequency output for upper using a higher Fb.
Using an undersized cabinet reduces the low frequency output available from your amplifier power, and requires longer or smaller cross section ports to tune low.
The larger the port cross sectional area, the longer the port has to be to tune low.
The smaller the cross section, the more port noise.
Up to you to choose what is most important for the cabinet size you have decided on, and what you listen to.
Art