Effects of cabinet size, and ported vs sealed?

[anm]

Very noob questions - and I should be reading some good speaker design book - but I am a little impatient so please bear with me and if possible answer.

If I have a speaker (for example N3 TL from GR research) and I just increase the volume of it by increasing its height - will the freq response be lowered, or I can screw up with anything else? I am assuming that crossover design is only dependent on freq at which you want to cross over, drivers involved and slope (order).

Secondly - I have a pair of sealed bookshelves. Will simply cutting out ports in the cabinet help in lowering the frequency response? How shall I calculate the diameter of the ports? Is the length of port pipe important as well?

Can I just plug the ports with some foam/ sock/ cloth etc to get back the original sealed design?

 

[GeorgeO]

rGenerally speaker drivers have properties called Theil Small parameters which are used to design enclosures. The enclosure design is optimised for performance-for example a woofer/tweeter pair can be used in a monitor or a larger floor stander and perform slightly differently,

http://online.physics.uiuc.edu/cour...Spring01/PPoongbunkor/Piya_Poongbunkor_TS.pdf

 

[doors666]

Very noob questions - and I should be reading some good speaker design book - but I am a little impatient so please bear with me and if possible answer.

If I have a speaker (for example N3 TL from GR research) and I just increase the volume of it by increasing its height - will the freq response be lowered, or I can screw up with anything else? I am assuming that crossover design is only dependent on freq at which you want to cross over, drivers involved and slope (order).

Secondly - I have a pair of sealed bookshelves. Will simply cutting out ports in the cabinet help in lowering the frequency response? How shall I calculate the diameter of the ports? Is the length of port pipe important as well?

Can I just plug the ports with some foam/ sock/ cloth etc to get back the original sealed design?

xo is dependant on the frequency, not box size. you can increase the volume to get more lower end. this can be done in limits though. each driver operates in a range of volumes, if you go outside of this, there will be issues. better download winisd and input the driver's t/s parameters and play around and see how it works. when you want to increase the volume, best bet is the depth. better to keep the baffle size same. key factors that should not be changed are baffle width, any of the positioning of drivers with respect to each other as well as the baffle or you will be redesigning the cross over. There are some speakers where baffle height also should not be changed (see troels gravesen's 3wclassic), but usually its safe enough to do this.

this is not advisable, usually ported speakers require more volume than sealed speakers. play with winisd and see if the drivers are happy in a ported enclosure of same volume. most probably it wont be, but you never know.

the t/s parameters published by most of the manufacturers are crap. you need to find somebody who's measured the drivers, zaphaudio, audioheuristics etc has published specs for many drivers. for grr drivers, you better contact danny ritchie to get these. if you can get the parameters as measured in the designed cabinet, nothing like this. and yes, you can plug the port to make it sealed again.

 

[miroflex]

...I am a little impatient so please bear with me ...

Hi anm,

We are willing to bear with you but you may find the sound from your speakers unbearable if you resort to sudden and drastic changes without considering the consequences.

Regards.

 

[arj]

Very noob questions - and I should be reading some good speaker design book - but I am a little impatient so please bear with me and if possible answer.

If I have a speaker (for example N3 TL from GR research) and I just increase the volume of it by increasing its height - will the freq response be lowered, or I can screw up with anything else? I am assuming that crossover design is only dependent on freq at which you want to cross over, drivers involved and slope (order).

Secondly - I have a pair of sealed bookshelves. Will simply cutting out ports in the cabinet help in lowering the frequency response? How shall I calculate the diameter of the ports? Is the length of port pipe important as well?

Can I just plug the ports with some foam/ sock/ cloth etc to get back the original sealed design?

adding on to the points already mentioned above

for a speaker design Speaker type, driver model, crossover, cabinet size/material are all considered before designing the speaker. playing around with any parameter is not something you should do unless you really know enough about speaker design. Any change is not "Local" it impacts the overall performance of the design.

So cutting a port in a sealed box may or may not increase the bass but it will definitely ruin the entire frequecy response from the original.

also plugging in a material into a port does not make it a sealed box. in the end the port is a "coupling mechanism" to your room and all these materials will only change the degree of coupling.

the better option for you is to readchoose a good DYI design and procure and build that...will save you far more time/headache and maybe even Money.

 

[anm]

Hi anm,

We are willing to bear with you but you may find the sound from your speakers unbearable if you resort to sudden and drastic changes without considering the consequences.

Regards.

these are a set of speakers I want to just play around with. Not my mains

 

[miroflex]

these are a set of speakers I want to just play around with. Not my mains

Hi,

It may be more fun to redesign the enclosures from the ground up, setting the design parameters as per your listening requirements, the drive units and cross over to be used and the area where they are to be listened to. You may like to set these out on a clean sheet of paper and then proceed further with your questions and wait for the answers to come.

Regards.

 

[grubyhalo]

...If I have a speaker (for example N3 TL from GR research) and I just increase the volume of it by increasing its height - will the freq response be lowered, or I can screw up with anything else? I am assuming that crossover design is only dependent on freq at which you want to cross over, drivers involved and slope (order)...

AFAIK, the N3-TL has internal dimensions that create a Transmission Line of a specific length to achieve a certain frequency tuning. Any change to the height or any other parameter would adversely affect the response of the speaker.

http://www.gr-research.com/pdf/Neo3box.pdf

Apparently, you should be able to hit lows in the mid-30's with this design. You can use the same components and the x-over network to make a sealed version of this model (N3S), which should give you a response of around 60Hz on the lower end...

 

[GeorgeO]

If you're willing to write it off, then by all means play with it.In fact many designers play around with enclosures modelling them differently, before arriving at the final one. Similarly some designers use active crossovers and then reverse engineer the passive crossovers.

To get a well designed speaker a lot of prototype work is needed.

 

[keith_correa]

If you're willing to write it off, then by all means play with it.In fact many designers play around with enclosures modelling them differently, before arriving at the final one. Similarly some designers use active crossovers and then reverse engineer the passive crossovers.

To get a well designed speaker a lot of prototype work is needed.

+1

Play around with different length's of cardboard tubes till you get one that floats your boat.

Here's something: A base length of cardboard tube in the port cutout and another cardboard tube of the same diameter and length inside that base cardboard tube. Then, slide that inner tube in/out to experiment with different lengths. If nothing else, should be fun doing this.