Hello Joker. Unfortunately, Foxx510 is correct. As JPW doesn't seem to be insanely popular (I have 2 pairs of floor-standing JPW Millenium series that have been boxed up for years, haven't been able to sell them...they were my father's before he passed away in 2004)...I doubt you'll be successful at obtaining Thiele/Small parameters this way. I'd say the easiest way would be to get your hands on a 'Woofer Tester', or something similar. However, yeah...the woofer in your JPW's will most likely work best in a sealed enclosure, and probably have a mid Q. You COULD try contacting Audio Group International, and attempt to get them that way, but I wouldn't be surprised if they weren't able to provide you with parameters on specific drivers. But I THINK they do use their own drivers in their loudspeakers, or at least they used to...but I'm not exactly positive about that...
http://www.jpwspeaker.co.uk/docs/contact.htm
http://www.woofertester.com/
Goodluck,
~ Brandin
http://www.jpwspeaker.co.uk/docs/contact.htm
http://www.woofertester.com/
Goodluck,
~ Brandin
Even if it was appropriate to modify the speakers to be ported instead of sealed, you're obviously running the risk of it going wrong (and damaging them) and also changing the sound characteristics - some midrange usually leaks out of the port, unless steps are taken to prevent it.
A better suggestion in terms of time and risk would probably be to buy a subwoofer to augment the bottom end. If you have an AV receiver, this would also allow you to use its crossover, which would stop low frequencies going to the main speakers, which in turn gives them an easier time when reproducing the rest of the music. Something to consider anyway...
A better suggestion in terms of time and risk would probably be to buy a subwoofer to augment the bottom end. If you have an AV receiver, this would also allow you to use its crossover, which would stop low frequencies going to the main speakers, which in turn gives them an easier time when reproducing the rest of the music. Something to consider anyway...
How determined are you to do this? You might consider the value of the speakers for resale (private sale), and take that money and apply it to some new speakers.
I don't see 'gold' monitors on the JPW website, if they still make your speaker, could you give us a direct link to it, so we can see what we are dealing with.
I don't think you need that T-S parameters, the cabinet is already built and matched to the speakers; the size is fixed, the drivers are fix. What you need to do is determine the internal volume of you cabinet. If it is a small cabinet, then you want to approximate the volume of the woofer itself.
Here are some Port Size calculators. You can uses 1.5" or 2" (or 1" if you can find it) PVC pipe from the building supply store.
Linear Team Port Calculator - (makers of WinISD speaker modeling software)
http://www.linearteam.dk/default.aspx?pageid=ventcalculator
Make sure you are using the right units-
Steve Ekblad's free Audio Software-
http://www.audiogrid.com/audio/
Scroll down a bit to the port calculator. The first time it calculates, it's kind of slow but it's fast after the first calculation.
Now you have to decide on what frequency you want you cabinet to resonate at. Ideally, it should be the same as the (fs) Free Air Resonance of the existing woofer. Without knowing the free air resonance, you can choose between 20hz and about 40hz. Again, it would help if you knew what you existing woofer was.
The parameters you want to ender are -
Vb = volume of the box
Fb = desired resonance frequency
number of ports/vents
diameter of vents
The calculator at Steve Ekblad's site will do circular, square, or rectangular ports
The calculator will then give you the depth of the port/vent.
For 1 inch ports, I would suggest that the port length be no less than 2" and no longer than the overal inside length minus 3 inches.
Try ONE or TWO 2 inch ports, and ONE or TWO 1 inch ports, or the equivalent in metric, if you prefer.
If you can come up with a workable port length relative to port diameter and quantity of ports, then you might be on to something.
Again, how small are these cabinets, and how much room is available for a port opening. Note: that there is probably less room inside the cabinet than you might think due to the braces that the cabinet front is screwed to.
An example,
- Assuming 1 cu.ft interior volume
- Assuming a desired resonance of 30hz
- Assuming 2 ports of 1 inch diameter
The resulting port length is = 3.969 inches long (for each port).
There is something to be said for tuning the cabinet resonance to be either higher than the woofer resonance, lower than the woofer, and exactly right on the woofer resonance. Though I am only guessing, I think tuning the cabinet above creates a sharp low frequency peak and a fast die off. Tuning it right on the resonance frequency creates what most purists would call a flat response, and I believe tuning it below the resonance creates a gradual sloping roll off of frequencies. Each has their own merits and demerits as well as supporters and detractors.
In your case, without the specs, you'll just have to guess. The woofer resonance (Fs) could be any where from 20hz to 60hz for a woofer. But since there is nothing you can do about that, you just have to choose are reasonable low resonance for the cabinet and work from there. I would run a range of numbers, partly so you get used to how each parameter changes the port length.
Just remember, that once you cut the holes, they remain cut forever, and if you don't like the result, it's difficult to plug up the holes and make the speakers sell-able.
I'm struggling with the same question, though my cabinets are already ported, they are ported wrong, and I have to find a way to improve them.
It is possible to test the resulting speaker combination to determine exactly what frequency it is resonating at, but it requires a 10 to 100hz signal generator (could use your PC) and a sensitive AC voltmeter. The voltmeter has to be capable of accurately measuring a range of voltages all less than 1 volt AC. (an oscilloscope would do)
For what it's worth.
Steve/BlueWizard
I don't see 'gold' monitors on the JPW website, if they still make your speaker, could you give us a direct link to it, so we can see what we are dealing with.
I don't think you need that T-S parameters, the cabinet is already built and matched to the speakers; the size is fixed, the drivers are fix. What you need to do is determine the internal volume of you cabinet. If it is a small cabinet, then you want to approximate the volume of the woofer itself.
Here are some Port Size calculators. You can uses 1.5" or 2" (or 1" if you can find it) PVC pipe from the building supply store.
Linear Team Port Calculator - (makers of WinISD speaker modeling software)
http://www.linearteam.dk/default.aspx?pageid=ventcalculator
Make sure you are using the right units-
Steve Ekblad's free Audio Software-
http://www.audiogrid.com/audio/
Scroll down a bit to the port calculator. The first time it calculates, it's kind of slow but it's fast after the first calculation.
Now you have to decide on what frequency you want you cabinet to resonate at. Ideally, it should be the same as the (fs) Free Air Resonance of the existing woofer. Without knowing the free air resonance, you can choose between 20hz and about 40hz. Again, it would help if you knew what you existing woofer was.
The parameters you want to ender are -
Vb = volume of the box
Fb = desired resonance frequency
number of ports/vents
diameter of vents
The calculator at Steve Ekblad's site will do circular, square, or rectangular ports
The calculator will then give you the depth of the port/vent.
For 1 inch ports, I would suggest that the port length be no less than 2" and no longer than the overal inside length minus 3 inches.
Try ONE or TWO 2 inch ports, and ONE or TWO 1 inch ports, or the equivalent in metric, if you prefer.
If you can come up with a workable port length relative to port diameter and quantity of ports, then you might be on to something.
Again, how small are these cabinets, and how much room is available for a port opening. Note: that there is probably less room inside the cabinet than you might think due to the braces that the cabinet front is screwed to.
An example,
- Assuming 1 cu.ft interior volume
- Assuming a desired resonance of 30hz
- Assuming 2 ports of 1 inch diameter
The resulting port length is = 3.969 inches long (for each port).
There is something to be said for tuning the cabinet resonance to be either higher than the woofer resonance, lower than the woofer, and exactly right on the woofer resonance. Though I am only guessing, I think tuning the cabinet above creates a sharp low frequency peak and a fast die off. Tuning it right on the resonance frequency creates what most purists would call a flat response, and I believe tuning it below the resonance creates a gradual sloping roll off of frequencies. Each has their own merits and demerits as well as supporters and detractors.
In your case, without the specs, you'll just have to guess. The woofer resonance (Fs) could be any where from 20hz to 60hz for a woofer. But since there is nothing you can do about that, you just have to choose are reasonable low resonance for the cabinet and work from there. I would run a range of numbers, partly so you get used to how each parameter changes the port length.
Just remember, that once you cut the holes, they remain cut forever, and if you don't like the result, it's difficult to plug up the holes and make the speakers sell-able.
I'm struggling with the same question, though my cabinets are already ported, they are ported wrong, and I have to find a way to improve them.
It is possible to test the resulting speaker combination to determine exactly what frequency it is resonating at, but it requires a 10 to 100hz signal generator (could use your PC) and a sensitive AC voltmeter. The voltmeter has to be capable of accurately measuring a range of voltages all less than 1 volt AC. (an oscilloscope would do)
For what it's worth.
Steve/BlueWizard
Hi joker6211,
You should reconsider your plans for two reasons.
1. A ported box is always larger than a sealed box for equivalent system Q. Boxes are almost always too small to reduce shipping costs.
2. The port unloads the woofer below the system resonance. You really don't want to do this.
The good news is that the TS parameters are easy enough to measure if you have some equipment. I suspect you will find that the math agrees with what I have said. Besides, ported is not always better. I like ported for big speakers, but not for small boxes.
-Chris
You should reconsider your plans for two reasons.
1. A ported box is always larger than a sealed box for equivalent system Q. Boxes are almost always too small to reduce shipping costs.
2. The port unloads the woofer below the system resonance. You really don't want to do this.
The good news is that the TS parameters are easy enough to measure if you have some equipment. I suspect you will find that the math agrees with what I have said. Besides, ported is not always better. I like ported for big speakers, but not for small boxes.
-Chris
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