Lets have an interesting conversation shall we?

[WmAx]

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?

Just thinking out loud here, but it seems obvious that the benefit to having the correction system in the central system processor is that you can correct the lower response of the main speakers along with the subwoofer for a more effective correction process.

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)?

There is no substantial complication introduced in a properly designed ported system. If you play content that has *substantial* levels under the port/radiator tuning freqeuency, *and* at the same time you are already using the ported/radiator subwoofer near it's limits in output capabilities, then a subsonic filter as Seaton earlier suggested would be needed to prevent possible damage and reduce gross distortion. If you are not driving the system near it's limits, then the result of not using such a filter is some wasted amplifier power and a little excessive driver movement[resulting in marginally higher distortion levels], but since you have substantial headroom in this case, it is not likely that you will encounter practical issues with performance. In either case, an appropriate HP filter optimizes the performance for such sound sources with very high amplitude low frequency content, such as movie soundtracks.

-Chris

 

[billnchristy]

You can tune a bandpass to be tight just as easily as you can tune a ported box to be a big floppy mess.

Its all in the design and drivers.

If you dont admit that the acoustimass woofer does a pretty killer job for what it is you are a little jaded IMO. I am not saying its a marvel or a wonder, but last time I saw one it was a 5.25 driver...pretty darn impressive.

 

[Mark Seaton]

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)?

John,

Maybe I was misunderstood, as I should have just used the term subwoofer equalization, but I was using the same term wafflebird had.

It sounds like you are referring to various forms of feedback and related distortion reducing efforts. That's not what I was talking about. My point was simply that subwoofer channel equalization will eventually be handled in the pre-processor or receiver and not by built-in equalization. Aside from the Velodyne DD series or something equivalent, the on-board EQ in most sub plate amps is mostly enough to make things "less bad" and rarely enough to address all of the problems we would like to.

 

[JoeE SP9]

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.

Check the Pass DIY website for a project to build a TL sub woofer. It's a very easy project. You can build 2 quite cheaply. Having 2 subs is better than just one!

 

[Johnd]

John,

Maybe I was misunderstood, as I should have just used the term subwoofer equalization, but I was using the same term wafflebird had.

It sounds like you are referring to various forms of feedback and related distortion reducing efforts. That's not what I was talking about. My point was simply that subwoofer channel equalization will eventually be handled in the pre-processor or receiver and not by built-in equalization. Aside from the Velodyne DD series or something equivalent, the on-board EQ in most sub plate amps is mostly enough to make things "less bad" and rarely enough to address all of the problems we would like to.

Mark (and WmAx): thanks for the clarification.

 

[wafflebird]

Ok..... another question

Do you think it is easier for a manufacturer to make a smaller high performance sub (like the supercubes, seismics, and lets say the new Mirage OMD-10) with passive radiators than ports? Obviously we know small is better with our better halves, but is it actually an easier way to get high performance with passive radiators?It seems like when they go small they go passive for the most part.

 

[Sheep]

Do you think it is easier for a manufacturer to make a smaller high performance sub (like the supercubes, seismics, and lets say the new Mirage OMD-10) with passive radiators than ports? Obviously we know small is better with our better halves, but is it actually an easier way to get high performance with passive radiators?It seems like when they go small they go passive for the most part.

If it was easier, SVS would have passive radiator subs. the easiest way is a big(good) box, and a big port(good drivers and amps help too).

SheepStar

 

[wafflebird]

But we are talking small cubes here.

Sheep so true, that’s why those monsters SVS etc. make are as good as they are, but I was specifically speaking about these really small subs everyone is coming out (well not everyone but you know what I mean) with. That is my question, are the passive radiators allowing them to do more, without trying to work a port into that small of an enclosure. If you look at the cutaway of the Seismic for example, there is just no room inside the enclosure for much of anything other than what is in there. So I guess it boils down to a sealed solid enclosure, or radiators.

I am guessing that if you gave a big driver a ton of wattage and no ports or radiators, in a smaller enclosure this could lead to the sub having a lot of potential enclosure resonance or the sub actually jumping around...........

Much like an Athena sub review I just saw recently....... I think you might know what I am talking about. Not that that sub has massive power but you see what I mean.

Anyway back to the point is small enclosure size leading manufacturers to go to the radiators for performance gain and room (inside the sub) restrictions?

 

[Sheep]

Sheep so true, that’s why those monsters SVS etc. make are as good as they are, but I was specifically speaking about these really small subs everyone is coming out (well not everyone but you know what I mean) with. That is my question, are the passive radiators allowing them to do more, without trying to work a port into that small of an enclosure. If you look at the cutaway of the Seismic for example, there is just no room inside the enclosure for much of anything other than what is in there. So I guess it boils down to a sealed solid enclosure, or radiators.

I am guessing that if you gave a big driver a ton of wattage and no ports or radiators, in a smaller enclosure this could lead to the sub having a lot of potential enclosure resonance or the sub actually jumping around...........

Much like an Athena sub review I just saw recently....... I think you might know what I am talking about. Not that that sub has massive power but you see what I mean.

Anyway back to the point is small enclosure size leading manufacturers to go to the radiators for performance gain and room (inside the sub) restrictions?

, The athena jumped around due to 1.) low weight (a monster amp and driver would weigh as much as that whole sub) and 2.) It's poor floor interface. If you have basic rubber feet (not plastic spikes) most any subwoofer will stay put.

Also, smaller cabinets are stronger, and need less bracing then large ones, so these tiny subs are quite inert. Add to that the mass of the big drivers, radiators, and the amp and you have a very heavy subwoofer (for its size).

Well, the velodyne SPL series has a large driver, with huge amounts of power, and a small enclosure, but they sure as hell don't jump around. They're actually fairly resonance free.

Also, Not all passive subs are equal to a decent ported one. Personally I don't think the seismic is a good example. The ultracube was quite boomy, sorta had that overhang affect. Passive rads. can supplement a port, but the enclosure still needs to have some size to it.

SheepStar

 

[Seth=L]

Check the Pass DIY website for a project to build a TL sub woofer. It's a very easy project. You can build 2 quite cheaply. Having 2 subs is better than just one!

Do you have a link? I would like to build a sub sometime, as I will have the tools to do it soon.

 

[wafflebird]

Those Velos are quite awesome too.......

I was checking out a SPL8-R not too long ago at Tweeter and I was indeed impressed with its' output. They are quite a bit of weight for their size as well.

My main reason for this post was to try to dig into this whole passive radiator theme we are seeing. It just seems while it is in no way new, it has definatly become more popular with companies lately for sure. Thus my questioning the reason they are doing it. Thanks for all of the responses.

 

[Mark Seaton]

Do you think it is easier for a manufacturer to make a smaller high performance sub (like the supercubes, seismics, and lets say the new Mirage OMD-10) with passive radiators than ports? Obviously we know small is better with our better halves, but is it actually an easier way to get high performance with passive radiators?It seems like when they go small they go passive for the most part.

No matter how hard you try, physics always wins. You either creatively work around the limitations imposed, or pay the price somewhere.

The best means to meet a given target is never a clear cut decision. If you want to get low and efficient with a large box, a vented solution is very cost effective. How capable the venting is for the enclosure is a large factor in the complexity, as more capability takes up more space and becomes larger and/or tougher to construct. If relatively high SPL capability is desired for a given tuning frequency the demands on a PR can get significant, and the required parts become more expensive, especially compared to a port. If the target box size is relatively small for the performance targets, then the size and complexity trade offs for a vented design become significant concerns, and PRs become more attractive.

One interesting consideration is that so long as you can build a PR heavy enough for the tuning in the desired box (there are practical and cost limits), the excursion from the PR required for a given SPL does not change with box size (only the mass to maintain the same tuning does). What we see is that if the performance targets are modest and/or the box size is small, a PR can be well justified and not very expensive. The PRs needed to get relatively high output from a larger box will be much more expensive.

The cost comparison to a sealed box is an interesting one. It really boils down to the linearity of the driver, it's ability to handle power/heat, and the cost of increased amplification/power in determining the strengths of each approach. If going from a 500W to 1000W amplifier isn't that great but you need exotic PRs to work in the design, two active drivers with more power can offer certain advantages over say a single driver and 2 PRs.

Within real world constraints and operation, the differences tend to be much mroe give-and-take than one being clearly superior over all others.

 

[JoeE SP9]

Do you have a link? I would like to build a sub sometime, as I will have the tools to do it soon.

The one from Pass Labs is so simple almost any person could make one.
http://www.passdiy.com/

 

[wafflebird]

Thanks Mark

That kind of sums it up I would say. And I was thinking because of the size constraints of some of the newer subs there had to be a benefit to going with the PR's. I also agree that two active drivers do have advantages over a single driver with 2 passive rads as well.

Like you said it all really boils down to cost for the manufacturer and what they are specifically trying to do with each offering.

Thanks again.

 

[billnchristy]

A TL is not a simple design, but I suppose if they did the work already and you are just cutting boards, any box is easy to build.