Ported to sealed enclosure conversion calculation

[nastynick]

Hi, I've got some bookshelf speakers I'd like to use as rears. But they're pretty big, so I'd like to convert them to sealed in smaller boxes. Is there an easy way to convert the cabinet volume if I don't know anything about the drivers?

 

[fpitas]

That's pretty tricky, but most likely they'll work ok if you just block the port.

 

[nastynick]

Thanks. I've seen port plugs, never played with them. I'm building enclosures I want to match, since I'm doing so I wanted to shrink these. They're not anything special just SS-CS5s. I'm trying to not spend much money.

But it seems like something that requires knowing the driver specs. Ya?

 

[DVDdoug]

It's generally safer to make a "random" sealed speaker than "random" ported speakers.

But assuming the current design is optimized a smaller box (ported or sealed) is going to degrade bass response.

There is a tester for a little over $100 USD, or you could buy new woofers with known parameters. Then you can get speaker design software to optimize or model the new design. WinISD is free, but if you buy the tester and run the software it might just tell you that a sealed box is the best you can do with the smaller cabinet.

IMO - Rear speakers aren't as critical as front speakers. It's better to compromise the rears than the fronts...

I have "floor speakers" hanging from the wall above my couch as my rear speakers. Somebody gave them to me and they don't match my front speakers.

 

[nastynick]

It's generally safer to make a "random" sealed speaker than "random" ported speakers.

But assuming the current design is optimized a smaller box (ported or sealed) is going to degrade bass response.

There is a tester for a little over $100 USD, or you could buy new woofers with known parameters. Then you can get speaker design software to optimize or model the new design. WinISD is free, but if you buy the tester and run the software it might just tell you that a sealed box is the best you can do with the smaller cabinet.

IMO - Rear speakers aren't as critical as front speakers. It's better to compromise the rears than the fronts...

I have "floor speakers" hanging from the wall above my couch as my rear speakers. Somebody gave them to me and they don't match my front speakers.

Thanks, ya imo the rears are less than 10% of what I hear so I'm fine with less bass, etc. I'm making really nice matching LRCs and I don't want to spend much more atm. I have plenty of material and skills for building cabinets tho.

 

[Duke]

Hi, I've got some bookshelf speakers I'd like to use as rears. But they're pretty big, so I'd like to convert them to sealed in smaller boxes. Is there an easy way to convert the cabinet volume if I don't know anything about the drivers?

Thanks, ya imo the rears are less than 10% of what I hear so I'm fine with less bass, etc.

As a ballpark guesstimate, I think you can probably get away with 1/3 the internal volume.

If it's boomy then cut a small hole in the box and cover or fill the hole with open-cell foam, creating a "pressure relief" box which will have less bass than the same-sized sealed box.

 

[alex-z]

You can measure the woofer parameters cheaply if you have a PC soundcard and pair of resistors. Dayton Audio Test System does the same job, they just package it for user convenience.

Measure Thiele Small parameters using free software - Audio Judgement

Learn how to measure thiele small parameters, or just a speaker impedance measurement using your sound card. Software used: Room EQ Wizard.

audiojudgement.com

Then you can easily calculate the optimal sealed cabinet using VituixCAD enclosure tool.

 

[nastynick]

You can measure the woofer parameters cheaply if you have a PC soundcard and pair of resistors. Dayton Audio Test System does the same job, they just package it for user convenience.

Measure Thiele Small parameters using free software - Audio Judgement

Learn how to measure thiele small parameters, or just a speaker impedance measurement using your sound card. Software used: Room EQ Wizard.

audiojudgement.com

Then you can easily calculate the optimal sealed cabinet using VituixCAD enclosure tool.

Hey Alex-z! Whoa this is wild! Doesn't seem like something so simple would give good measurements. But I've got all the parts so it might as well try! Thank you for sharing.

 

[alex-z]

Hey Alex-z! Whoa this is wild! Doesn't seem like something so simple would give good measurements. But I've got all the parts so it might as well try! Thank you for sharing.

All T/S parameters can be determined via two calibrated impedance sweeps, the driver diameter, and a single known parameter, such as a fixed mass, or fixed air volume. If you have resistors with 1% precision, your results should be similarly precise.

However, this method is not sufficient for large signal parameters, which describe how the motor strength, inductance, and suspension compliance change with driver excursion. Those details are what justify more expensive drivers, and you need a laser vibrometer to measure them properly. Too expensive for DIY.

 

[Rick Sykora]

Lots of good advice here, but unless you want to learn speaker box design, the measurement approach is a lot of work for this (cheap) speaker…

If you check the review thread of this speaker, @Dennis Murphy made a run at improving it and may have some measurements or advice. Given the cost of these, if I was devoting time and money to building a nice new box, pretty sure I would invest in new drivers.

 

[Plcamp]

If the existing ‘big boxes’ are also sealed then I think that…

Reducing the volume will increase the -3db frequency and cause some response peaking just above that frequency. The smaller the box, the bigger the effect.

If you have equalization you can cancel that (peaking and loss of bass) effect, but need more amp power for a given spl at bass frequencies.

 

[abdo123]

Thanks. I've seen port plugs, never played with them. I'm building enclosures I want to match, since I'm doing so I wanted to shrink these. They're not anything special just SS-CS5s. I'm trying to not spend much money.

But it seems like something that requires knowing the driver specs. Ya?

just glue some MDF to the entrance of the port after you stuffed it.