Subwoofer search

[alfa147x]

can some one explain the use of a Passive radiator (speaker) ?
Is it kinda like a mix between a sealed enclosure and a vented box?

im doing some research for a potential subwoofer and was browsing the parts direct site and saw a couple of Passive radiators could someone please put this in simple terminology?

Thanks a bunch,
alfa

 

[PurdueRy]

A Passive radiator is a plain old speaker cone without the electrical components. That's why its passive. It serves as the mass-spring system which allows one to tune a box to a certain frequency. This frequency is changeable by changing the mass of the cone. Sometimes ports can be tough to place in a speaker box because they become long depending on the design and require more than one be used or an elbow joint internal to the box. This all takes away from the internal volume of the box that the main driver relies upon. Therefore, if one does a vented design, the box often ends up bigger partially due to the volume of air removed by the port.

 

[EvilYoda]

Originally posted by: PurdueRy
A Passive radiator is a plain old speaker cone without the electrical components. That's why its passive. It serves as the mass-spring system which allows one to tune a box to a certain frequency. This frequency is changeable by changing the mass of the cone. Sometimes ports can be tough to place in a speaker box because they become long depending on the design and require more than one be used or an elbow joint internal to the box. This all takes away from the internal volume of the box that the main driver relies upon. Therefore, if one does a vented design, the box often ends up bigger partially due to the volume of air removed by the port.

Well...that's about it.

I'm sure someone'll want to get into more technical terms though.

 

[vi edit]

Originally posted by: PurdueRy
A Passive radiator is a plain old speaker cone without the electrical components. That's why its passive. It serves as the mass-spring system which allows one to tune a box to a certain frequency. This frequency is changeable by changing the mass of the cone. Sometimes ports can be tough to place in a speaker box because they become long depending on the design and require more than one be used or an elbow joint internal to the box. This all takes away from the internal volume of the box that the main driver relies upon. Therefore, if one does a vented design, the box often ends up bigger partially due to the volume of air removed by the port.

Great post.

A 12" driver with a PR in a 1 cubic foot box would perform around the same as that driver in a ported 3.5-4.0 cubic foot box.

It's a massive generalization, but that's the gist of it. You can run the specifics through something like winISD to get more accurate results depending on the driver.

Their value really comes into play with larger drivers though. 15" and 18" drivers require very large enclosures and venting. A PR really helps cut down on size, at the expense of buying 3/4 of another driver instead of a $20 tube.

 

[alfa147x]

ok thanks a bunch

so it acts like a ported box but in a much smaller size
in a ported box the air acts like a spring but in this case the passive radiator creates the springiness

also how does one choose between a sealed and ported box?
also the room is 15feet by 12 feet if that matters any

 

[spidey07]

Originally posted by: PurdueRy
A Passive radiator is a plain old speaker cone without the electrical components. That's why its passive. It serves as the mass-spring system which allows one to tune a box to a certain frequency. This frequency is changeable by changing the mass of the cone. Sometimes ports can be tough to place in a speaker box because they become long depending on the design and require more than one be used or an elbow joint internal to the box. This all takes away from the internal volume of the box that the main driver relies upon. Therefore, if one does a vented design, the box often ends up bigger partially due to the volume of air removed by the port.

And you can also have multiple passive raditors for different tunes. Works well, but is complicated.

 

[EvilYoda]

Originally posted by: spidey07

Originally posted by: PurdueRy
A Passive radiator is a plain old speaker cone without the electrical components. That's why its passive. It serves as the mass-spring system which allows one to tune a box to a certain frequency. This frequency is changeable by changing the mass of the cone. Sometimes ports can be tough to place in a speaker box because they become long depending on the design and require more than one be used or an elbow joint internal to the box. This all takes away from the internal volume of the box that the main driver relies upon. Therefore, if one does a vented design, the box often ends up bigger partially due to the volume of air removed by the port.

And you can also have multiple passive raditors for different tunes. Works well, but is complicated.

Yah. I'd still like to have a go at building one some day. My Velodyne does quite nicely for now though.

 

[vi edit]

Originally posted by: alfa147x
ok thanks a bunch

so it acts like a ported box but in a much smaller size
in a ported box the air acts like a spring but in this case the passive radiator creates the springiness

also how does one choose between a sealed and ported box?
also the room is 15feet by 12 feet if that matters any

Ported Pro's:
- Better extension with less power (not as much amp needed)
- Rolls off better below tuning
- Typically cheaper for lower tuning (because of less amp reqs and is more efficient with driver)
- Isn't as picky about needing to be EQ'd for best performance

Ported Con's:
- Needs cubic volume and size to meet tuning and port demands making for larger cabinets
- Much easier to damage driver going past tuning if you don't have a LFE limiter that cuts the signal under a certain hz
- Poor ones sound worse due to port noise and ease of overdriving the speaker

Sealed Pro's:
- Smaller
- Typically "louder" at higher freq
- Easier to build due less size, calcuations, and port placement

Sealed Con's:
- Needs a lot more power (and/or driver size)to reach extensions similar to ported
- More expensive for better performing ones because of above listed reasons
- Rolls off quickly once you go past tuning
- Needs to be EQ'd to get dialed in better

-------------------------

For movie use, a ported sub is going to be cheaper, and play louder where it counts than a sealed of similar cost. When it comes to music, a small sealed sub will likely be a better fit because of their tuning characteristics and smaller footprints.

I'm not too big on sealed simply because I'm a value buyer and can't get as much for my money with them.

 

[Tiamat]

Passive radiator is a 4th order design just like a ported design. Below tuning frequency, the response falls at 24dB/octave. Ported speakers require large enclosure to fit the large tuned ports. Passive radiators tuning is based on their mass which is adjusted typically by weights.

Sealed speakers are 2nd order designs. The response falls at 12 dB/ octave below tuning frequency which is based on the woofer parameters and the size of the cabinet.

Sealed subwoofers typically use eq to flatten the response. If the driver is up to the task and you have enough power, you can apply a Linkwitz transform to boost the response of the subwoofer far below tuning into single digit frequencies. That way, you have the extension of the ported design with the upper bass output of sealed designs.

 

[Rubycon]

Originally posted by: Tiamat
Passive radiator is a 4th order design just like a ported design. Below tuning frequency, the response falls at 24dB/octave. Ported speakers require large enclosure to fit the large tuned ports. Passive radiators tuning is based on their mass which is adjusted typically by weights.

Sealed speakers are 2nd order designs. The response falls at 12 dB/ octave below tuning frequency which is based on the woofer parameters and the size of the cabinet.

Sealed subwoofers typically use eq to flatten the response. If the driver is up to the task and you have enough power, you can apply a Linkwitz transform to boost the response of the subwoofer far below tuning into single digit frequencies. That way, you have the extension of the ported design with the upper bass output of sealed designs.

It's fun to use a real speaker as the PR then feed it to an amp with processing for phase control and ballistics. It takes a very accurate and powerful amplifier to do this. Some very loud and low frequencies can be realized with such a set up.

 

[alfa147x]

with a semi low budget its seems as i will have to go ported
but i really hate that buzz kinda sound it gives off
kinda like BOOM FFFFFF

 

[spidey07]

That's port noise. Built correctly there should be none of that.

 

[alfa147x]

Originally posted by: spidey07
That's port noise. Built correctly there should be none of that.

the sub was built by Yamaha is it that the sub is just being pushed too hard?
Yamaha YST-SW21

 

[spidey07]

What you're probably hearing is the voice coil slapping. If so it's being overdriven.

A sub "farting" is the driver going too far or port noise.

 

[Rubycon]

There's several stages of undesirable operation of reflex speakers. First and foremost - find the tuning point of the system! Second make sure that it never sees significant program material below this point. No need for a brick wall HPF - 18dB/octave butterworth is just fine.

The first hint of overdriving and/or driving with frequencies significantly below the tuning point is a substantial increase in cone excursion. The bass will have a "looser" sound and generally sound inaccurate. At higher levels the voice coil will leave the gap completely (if the amp can push it this hard) and the sound will have a fluttering tone often with lots of first and second harmonics. At the onset of x-mech (again assuming adequate amp power OR extremely low frequencies well below the tuning point) the voice coil former may actually contact the back plate of the magnet assembly. This will make a very loud clattering sound and is damaging the speaker! Do NOT allow this to happen! If the former becomes physically distorted it can rub in the gap causing buzzing and audible distortion at all (most noticeable at lower levels). When this happens the driver needs to be replaced or re-coned.

Summary: listen carefully for telltale sounds of driving your system past its limits. Know the limits and keep listening levels well within them. If you're always approaching the limit you need to re-think your setup. (or listen at lower levels which never hurts your ears!)

 

[spidey07]

Originally posted by: Rubycon

Summary: listen carefully for telltale sounds of driving your system past its limits. Know the limits and keep listening levels well within them. If you're always approaching the limit you need to re-think your setup. (or listen at lower levels which never hurts your ears!)

Yeah! That's what I said!

 

[alfa147x]

Originally posted by: spidey07

Originally posted by: Rubycon

Summary: listen carefully for telltale sounds of driving your system past its limits. Know the limits and keep listening levels well within them. If you're always approaching the limit you need to re-think your setup. (or listen at lower levels which never hurts your ears!)

Yeah! That's what I said!

is it possible that i can use the amp from my old sub!

 

[vi edit]

Are you planning on building your own subwoofer?

It's hard to say if you could (or even should) salvage the amp in your current sub. You need to know the ohm rating (8 or 4?) and how much power it's really putting out(probably not much).

There isn't a lot of value in building your own sub for under the $250 mark unless you have some specific esthetic or size needs. The $250 BIC sub on Ebay and the $300 options from Elemental Designs will likely be equal performers and put together with factory precision.

If you are interested in building your own, you can get some ideas and helpful links from my build thread:

http://forums.anandtech.com/me...ght_key=y&keyword1=diy

I really wanted it to double as a table and wanted it to blend in as a peice of furniture. So that was part of the reason of going home built.

For value and performance, I really like the Shiva-X driver:
http://www.diycable.com/main/p...fo.php?products_id=653

Match it up to the Parts Express 240w plate amp and a precision port and then follow the build directions on the DIYcable site and that's a nice performer for under $300.

 

[alfa147x]

Originally posted by: vi edit
Are you planning on building your own subwoofer?

It's hard to say if you could (or even should) salvage the amp in your current sub. You need to know the ohm rating (8 or 4?) and how much power it's really putting out(probably not much).

There isn't a lot of value in building your own sub for under the $250 mark unless you have some specific esthetic or size needs. The $250 BIC sub on Ebay and the $300 options from Elemental Designs will likely be equal performers and put together with factory precision.

If you are interested in building your own, you can get some ideas and helpful links from my build thread:

http://forums.anandtech.com/me...ght_key=y&keyword1=diy

I really wanted it to double as a table and wanted it to blend in as a peice of furniture. So that was part of the reason of going home built.

For value and performance, I really like the Shiva-X driver:
http://www.diycable.com/main/p...fo.php?products_id=653

Match it up to the Parts Express 240w plate amp and a precision port and then follow the build directions on the DIYcable site and that's a nice performer for under $300.

the problem is that i need something that looks can fill my room
the room it's self is about 15 x 12 feet

but its connected w\o wall to a dinning and then kitchen once again no wall then its about 30 x 12

 

[alfa147x]

oh and how about using a sub (driver) meant for cars? any down sides ?

 

[vi edit]

Originally posted by: alfa147x
oh and how about using a sub (driver) meant for cars? any down sides ?

Sorry to hijack the thread into a subwoofer discussion. I don't know if that was your intent. But to give you a good answer on what you should do, what budget do you have in mind? And what are your primary uses for the system?

Also, does the room you are working with have access to an attic, crawlspace, or unfinished part of the house? If so, an infinite baffle setup may be an option.

 

[alfa147x]

Originally posted by: vi edit

Originally posted by: alfa147x
oh and how about using a sub (driver) meant for cars? any down sides ?

Sorry to hijack the thread into a subwoofer discussion. I don't know if that was your intent. But to give you a good answer on what you should do, what budget do you have in mind? And what are your primary uses for the system?

Also, does the room you are working with have access to an attic, crawlspace, or unfinished part of the house? If so, an infinite baffle setup may be an option.

its no problem thats what the intent of the question was

My budget is a around $300 +$50

There is a garage

In order from most listen to to the least:
tv shows, music, xbox, movies

Ill take pictures later but this is what i drew up:
http://img528.imageshack.us/my...?image=42773312mr2.jpg

 

[Adul]

I just finished my sub build.
exoduis audio 12" XBL^2 sub, 135
350 watt amp from elementral designs 175
27 bucks for a sheet of mdf.
Plus a couple of nice binding post to connect speaker wire. I opted not to integrate the amp since I may want to upgrade.
Box I built was tuned to 18hz with a 1" slot port.

here is some pics of my project

http://pics.allthatremains.org...hp/v/Speaker+Projects/

total cost was around 350 for me.


While I am not completely finished with my sub yet (turning it into end table), it is hooked up for listening purposes to make sure I am happy with design.

So far I am more that satisfied. I'll upload some pics later.

 

[alfa147x]

Originally posted by: Adul
I just finished my sub build.
exoduis audio 12" XBL^2 sub, 135
350 watt amp from elementral designs 175
27 bucks for a sheet of mdf.
Plus a couple of nice binding post to connect speaker wire. I opted not to integrate the amp since I may want to upgrade.
Box I built was tuned to 18hz with a 1" slot port.

here is some pics of my project

http://pics.allthatremains.org...hp/v/Speaker+Projects/

total cost was around 350 for me.


While I am not completely finished with my sub yet (turning it into end table), it is hooked up for listening purposes to make sure I am happy with design.

So far I am more that satisfied. I'll upload some pics later.

Looks sweet how did you come up with that design ?
any recommended links

oh and did you use 2x subs or is that the name of the sub?

 

[alfa147x]

also what does it mean when a subwoofer has dual 4-ohm voice coils? Should i look at something with less resistance? or more?