Lets have an interesting conversation shall we?

[wafflebird]

First off I just love this website, lots of great information and a lot of great people helping each other out. Being a nut about this stuff as I am I would like as many of your inputs on this as possible as it seems the subwoofer industry is changing. I know that single driver, single or multiple radiator subs are not "NEW" but have you folks noticed the amount of companies starting to employ this configuration on their new equipment? You have the Definitive technologies Super Cubes (I know these are not NEW per say but bear with me) Mirage has just recently announced the OMD S10 1 active driver and two radiators, Klipsch on their newer line of subs are using this same configuration, Paradigm Seismic and the Ultra Cubes use this technology as well. I could list several others but I am sure you all know of them as well.

Now I know that this is not particularly "NEW" to some of these manufacturers (I know some of klipschs' older subs used this just to name one) but it seems like the newer model subs from a lot of the manufacturers are heading this way. What I would like for us all to chime in about and to discuss are the pros and cons of each type of sub. Generally speaking a sealed enclosure normally (not saying always) produces tighter bass. I also know to really get a sealed sub to go low and loud you have to be sure to give it some wattage and as you can see the manufacturers listed that are making their subs this way have generally upped their wattage for the same size drivers. Again I am not saying that they all have but for the most part this is a true statement.

And 1 more thing to throw in just for kicks, we are also seeing more and more "Servo" controlled subs as well as room EQ which we all know is a good thing. What is your take on this and at what price level should we start to expect to see these features on our equipment purchases?

So come on guys (and girls) lets give some input on this one.... please.

Thanks in advance.

 

[sivadselim]

A sub with a passive radiator is actually more like a vented sub than a sealed design.

 

[wafflebird]

Thats true but....

I agree with that BUT the air is still contained for all intents and pourposes inside the sub. It gives the main active driver a little "breathing room" for sure, but it is not really a port. Thanks for the response. I hope we can really get some more in depth input from the rest of you folks as well as in which do you like better, or do you like one type more for music, and another for HT etc.

 

[billnchristy]

Dont forget AV123s BMF with a single 15" 6th order bandpass with 3 18" PRs!!

I think we are seeing them more because they offer the + of a ported design without all the port huff below Fb, although you would probably get serious excursion issues, which is probably why they are being tuned so low...

 

[Sheep]

The main reasoin for passive radiators is you can have a small enclosure and still keep a low tuning point. With the ever increasing need for WAF friendly speakers, I would be surprised to see many sub-speaker company's using the large ported subwoofers any more(Well, for the married market at least).

Obviously there will be those that must have the big ported ones, and serves them right. It's the best way to get good bass, for cheap. Passive radiators have there fallies, including slapping, and still not having that "sealed" sound. I also believe they cannot produce the same amout of SPLs as a ported system(don't quote me on that).

As for servo's, I've heard many opinions, but the one that made me really think about their effectivness came from WmAx.

(Roughly)"A servo is only useful on a poorly designed driver. If the driver is capable of large amounts of linear movement, as well as low power compression and is implemented in a proper enclosure with sufficient amplification, the servo will not be very effective."

I personally agree with this, but I still think a servo is a good way to help a subwoofer out. I would like to see a servo implimented on a good quality driver, and see if there is a big difference.

Sealed subs have that sound. Even a poor quality driver can sound better in a sealed box. Obvisouly they don't play as loud as ported subwoofers, and they also loose low end extension (given the same driver in a box designed right for it's certain application be it ported or sealed. The ported version having the better extension).

But even with that, you can still yield subwoofer from every class that perform well. Velodyne makes very loud, low, and clean sealed subs. I've also seen poor sealed subs. It depends on the measures taken to build the box/drive/amp, and where (if any) the corners were cut.

SheepStar

 

[jonnythan]

I agree with that BUT the air is still contained for all intents and pourposes inside the sub. It gives the main active driver a little "breathing room" for sure, but it is not really a port. Thanks for the response. I hope we can really get some more in depth input from the rest of you folks as well as in which do you like better, or do you like one type more for music, and another for HT etc.

When you think about it, a ported sub only pushes a volume equal to its own surface area*linear movement out of its port. It then sucks the same volume right back in.

A passive radiator does a very similar thing.

 

[Sheep]

When you think about it, a ported sub only pushes a volume equal to its own surface area*linear movement out of its port. It then sucks the same volume right back in.

A passive radiator does a very similar thing.

Agreed. The tuning of the port adds the same resistance as a passive radiator.

SheepStar

 

[WmAx]

The main reasoin for passive radiators is you can have a small enclosure and still keep a low tuning point....

Obviously there will be those that must have the big ported ones, and serves them right. It's the best way to get good bass, for cheap.

A passive radiator is used in place of a port, and serves the identical function. The same size enclosure [not including the volume that the port consumes] stands for a given target function response. The saving in enclosure volume comes from the smaller internal volume that the passive radiator requires as compared to a large, long port[that some drivers may require].

Passive radiators have there fallies, including slapping, and still not having that "sealed" sound. I also believe they cannot produce the same amout of SPLs as a ported system(don't quote me on that).

The sealed 'sound' is a function of frequency response, at least this is the only conclusion that I can make based upon pre-existing perceptual research, as well as my own controlled blind tests. You can emulate the final target function response of a given sealed box with the appropriate ported/radiator system with an electronic line level curve correction/compensation, if so desired.

-Chris

 

[Buckeyefan 1]

Everyone should read up on this, "Enclosure Tutorials."

http://mobile.jlaudio.com/support_pages.php?page_id=148

I've always liked the single reflex bandpass design.

This is also good reading as far as Hz output goes.

http://mobile.jlaudio.com/support_pages.php?page_id=147

 

[Seth=L]

All my experiances with Bandpass have been boomy. I had a Paradigm PS-1000 bandpass with three noise resistant ports. I had to plug two ports to get any descent sound from it. If I could have any DIY sub, if I had unlimited resources and know-how, I would make a Transmission Line enclosure.

Bose Acoustimass is Bandpass, if you like those.

 

[Seth=L]

Hey Brian, How about the Paradigm Servo 15 or the Signature 15. I think those things are awesome, but expensive.

 

[Buckeyefan 1]

All my experiances with Bandpass have been boomy. I had a Paradigm PS-1000 bandpass with three noise resistant ports. I had to plug two ports to get any descent sound from it. If I could have any DIY sub, if I had unlimited resources and know-how, I would make a Transmission Line enclosure.

Bose Acoustimass is Bandpass, if you like those.

They need to be built to exact specs. Right now, I'm running dual 10's in a DIY double sealed enclosure under the rear seat in my truck. Outstanding bass, but it takes over 900 watts at 1 ohm to push them. It's a real workout for my alternator and cap. If you have the room and know how, it's a much better design - why else would Bose build them? Efficiency and cost. The problem is, not many know how to build them properly. Take that Bose design, and upscale it 4-5x with better drivers and amps.

 

[bumpyride]

Hey everyone, just recently got turned on to this site so here's my first post:

I just thought I'd point out that passive drivers and ports don't behave exactly the same. Both have mass (the diaphragm and the air in the port) but the driver also has compliance from the diaphragm's support (surrounds, spider, etc.). At lower frequencies, a good size port can be detrimental to the 'acoustic suspension' provided by the compressing air in the speaker enclosure. A passive radiator has its own suspension so it doesn't have that problem. It also obviously increases the active area of the speaker and, thus, its efficiency. However, it does add more mass to the system just like a port which makes for slower bass, though it can be better tuned and controlled.

That was all pretty obvious but I felt like adding and introducing myself.

 

[WmAx]

Hey everyone, just recently got turned on to this site so here's my first post:

I just thought I'd point out that passive drivers and ports don't behave exactly the same. Both have mass (the diaphragm and the air in the port) but the driver also has compliance from the diaphragm's support (surrounds, spider, etc.). At lower frequencies, a good size port can be detrimental to the 'acoustic suspension' provided by the compressing air in the speaker enclosure.

In practice, a properly designed ported system does not have substantial unloading issues with normal music[as opposed to special demonstration pieces or test signals]. LF artifacts such as turntable rumble and record warping may be an issue in some cases, at which point a line level subsonic filter should be used. Some low quality woofers may have issues with a ported enclosure, even if properly designed, however. This is related to a poorly designed motor with significant asymmetrical force when comparing excursion vs. incursion. In some extreme cases, you may actually see a speaker cone [when using a test signal under the port tuning frequency] move seemingly only in one direction, back to rest position, and back in the same direction again, without a visible full sine wave cycle.

-Chris

 

[bumpyride]

In some extreme cases, you may actually see a speaker cone [when using a test signal under the port tuning frequency] move seemingly only in one direction, back to rest position, and back in the same direction again, without a visible full sine wave cycle.

That's interesting. It's the type of thing you'd miss entirely just thinking in terms of lumped elements. I was happy with myself for considering the ports effect on the enclosed volume's compliance, but as you pointed out, that's not much of an issue.

 

[Mark Seaton]

So what IS up with these new-fangled passive radiator things?

Remember the ContraBass was around more than 15 years ago (long before the first Sunfire) with high excursion passive radiators tuned below 20Hz. The idea is nothing new, only the widespread use and adaptation of the option. This is due to many factors that have already been mentioned with respect to enclosure size and low frequency capability, but it should also be noted that advancements in materials, manufacturing and the overal design and excecution of reliable passive radiators has been another contributing factor. 10 years ago you were unlikely to find many sources for passive radiators with the ability to reliably handle 2" of P-P travel.

In practice, a properly designed ported system does not have substantial unloading issues with normal music[as opposed to special demonstration pieces or test signals]. LF artifacts such as turntable rumble and record warping may be an issue in some cases, at which point a line level subsonic filter should be used.
-Chris

While the specific design and its limiting factors are still major determinants of the need for high pass protection, the bass content in modern soundtracks almost mandates the use of high pass filtering with reflex designs (which includes both ported & PR). Even if damage is not a concern, without a high pass filter, there is a lot of waste effort in the system that will lower its useful performance limits.

 

[wafflebird]

Wheewwwww...........

Thanks for all of the responses guys. I was afraid I was going to watch this thread go down...down.... then onto the dreaded page 2 and then disappear. But every response is appreciated for sure. It is my understanding that bass actually is produced by the radiators as well, correct? Not the same amount as the main active driver but some right? Now does that help or hurt placement options? Look at the new triangular Klipsch subs. 1 active and two radiators. Is that a good thing for placement if you do not put it in a corner or not?

Also what about the room correction/tuning function we are starting to see on the newer subs? And I have seen tons of raving on the Velodyne SMS-1 system as well. Has anybody here used it besides the reviews and can really explain the difference it made for them?

Thank you again for keeping this alive.

 

[Sheep]

Thanks for all of the responses guys. I was afraid I was going to watch this thread go down...down.... then onto the dreaded page 2 and then disappear. But every response is appreciated for sure. It is my understanding that bass actually is produced by the radiators as well, correct? Not the same amount as the main active driver but some right? Now does that help or hurt placement options? Look at the new triangular Klipsch subs. 1 active and two radiators. Is that a good thing for placement if you do not put it in a corner or not?

Thank you again for keeping this alive.

The Passive radiator takes over at it's tuning point. If you measure the THD from the active driver, it will jump once it's at the passive rads. Fs. When you measure the subwoofer, you have to take measurements from both the active and passive driver.

SheepStar

 

[Mark Seaton]

It is my understanding that bass actually is produced by the radiators as well, correct? Not the same amount as the main active driver but some right? Now does that help or hurt placement options? Look at the new triangular Klipsch subs. 1 active and two radiators. Is that a good thing for placement if you do not put it in a corner or not?

While not a perfectly accurate analogy, you could think of the port somewhat like a narrow bandwidth woofer for a 2 way system. If you look at the individual responses of the port and the driver they seam together to give you the resulting frequency response. At higher frequencies the active driver produces almost all of the sound where as you move lower there will generally be some frequency (above tuning) where the port or PR and driver are producing equal output and is akin to a crossover frequency. Then as we reach tuning, the driver's production of sound is at a minimum and the port or PR produces the majority of the output. What differs from a crossover is the behavior below tuning, where the port/PR and driver begin to progressively cancel eachother's output as frequency lowers, which results in the steeper roll off to the low end as compared to a sealed design.

So far as placement, the more significant interaction with the room occurs at higher frequencies where the driver is usually producing almost all of the output, and all that really matters is the location of the driver, not the ports or PRs. There can be some difference in low frequency coupling to the room, but it isn't typically that significant unless the subwoofer dimensions are quite large.

Also what about the room correction/tuning function we are starting to see on the newer subs? And I have seen tons of raving on the Velodyne SMS-1 system as well. Has anybody here used it besides the reviews and can really explain the difference it made for them?

My own take is that subwoofer correction doesn't belong IN the subwoofer. If you are using multiple subwoofers this serves to only be redundant and possibly more complicated to set up. Where subwoofer correction DOES belong is inside your pre-processor or receiver. I would predict we will finally start seeing this happen over the next 3 years, as it is a logical progression with the first steps already being made with full range EQ.

 

[Johnd]

My own take is that subwoofer correction doesn't belong IN the subwoofer.

Is that to say you believe it difficult (or impossible) to correct (via port tuning or some other method) the innaccuracies prone in ported systems?

Or is it that it is simply best to leave a clean, sealed chamber alone and tweak it electronically? (Because of the complications introduced in a ported system)?