Can a ported design sound sealed ?

I'm wondering if anyone has ever been lucky enough to hear a slot loaded design such as this one , sound as fast and clean as a sealed design ?  I have a customer that longs for the extra output and bump of a ported design , but he wants ZERO overhang , perfect tone , and perfect transients ..... Sheesh !

[IMG]https://img.photobucket.com/albums/v112/SRTBlue/re6.jpg[/IMG]

I've heard some DAMN GOOD slot loaded enclosures , but never one as accurate or fast as a great sealed sub with lots of power on it .....
Thanks

Here's the pic I tried to upload ...

Steven Kephart wrote:

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Sure it can with a proper enclosure design.  It's just that most ported enclosures are designed to be a bit peaky in the response, especially to keep the enclosure size down to a manageable size.  But a well designed ported enclosure can sound incredible.

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Ok Steven ..... Will you be kind enough to supply me with some details ?  Maybe a cut sheet and enclosure specs for a certain subwoofer you have heard that sounds as good as a great sealed design ....  The subwoofer enclosure in the photo is one I built to EXACT specs for a Diamond Audio D6 subwoofer.  It was probably the single best slot loaded design I've ever heard in my 23 yrs of car audio , but still fell short of the accuracy and speed of my Boston Acoustics Pro LF 12.5s in a sealed enclosure.  I'd LOVE to have the best of both worlds ....

Thanks

coppellstereo wrote:

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I really liked my boston Pro LF 12.5 - I wish I had more advice for you with box design. I've yet to build a ported box. =(

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Yeah ... They are one of the VERY FEW subs that have a LOT of output and slam , but are ALWAYS accurate and fast.  They truly do seem to bridge the gap between sealed and ported enclosures. My customer wants sound like I have with my sealed Bostons ,  but with even more output and slam .....

I like to work with ported designs, and use them exclusively in my home sound system for all the woofers.  The sub in my car is sealed, but on my next one (if this one ever wears out!) I might work on a vented design for that, too. 

IMO, you can't use the manufacturer's data exclusively to build a ported box.  Some of them give some very detailed choices to choose from, and give you tested responses with each of them...which is great.  But most are very vague in the details and so you're left with some simple measurements to follow.  You have to ask yourself, "Who are they appealing to with this design?  Is it designed for high Q, more SPL, a noticeable peak in the response, to appeal to the majority of buyers who want more bass?

I will first look at a woofer's parameters to tell if it should be ported.  Look at Fs and Qes, and do the division Fs / Qes.  This gives you the EBP.  If the number falls in the range of 50 or lower, use the driver in a sealed box.  If it is a higher number in the 70's or above, use it in a vented.  For that gray area in between, work it up both ways in a box-building program, then use your own discretion on how to build it.  Personally, I will go with ported for any EBP of 60 or higher, and look at both ways between 50 and 60.

The reason you try to follow this rule is because 1. a woofer meant to be ported will lack in low bass response if put in a sealed box, and 2. a woofer meant to be in a sealed box will have an odd reponse curve and an extraordinarily long port if you try to work up a vented box for it.  This is just my opinion based on my own experience...I don't know if it's 100% technically correct.  The pic you showed above has an extraordinarily long port, with five 90 degree corners.  I would not build a box with more than one bend in the port...there should be another way to get around it.

The best SQ from a ported box will be a design that uses a straight length of port and has a response curve that has a very gradual curve, and not peaking more than 1.5 to maybe 2 decibles above 0.  To get this, start working with a very low tuning frequency, near the driver's Fs.  When you work it up and look at it, you'll note that the box itself will not be outputting a whole lot of sound through the port, but there will be some.  It will be several db's down from the normal range and the response curve will most resemble that of a sealed box.  It is the opposite of SPL, where the port is playing a big role in playing the loudest frequencies and the peak in the response is high in the 50-70 Hz range. 

When you're working on the design, the biggest obstacle is box air volume, or total box size.  You will always have to arrive at a compromise, but such is the case with car audio.

There are two free box building programs that I have gotten to know, and use them exclusively.  One is WinISD Pro and the other is Unibox. 

Here is an example that I found in the Unibox database of a ported response that is great SQ:  vb_response_soundstreamss-12.gif

The Fs of this Soundstream SS-12 is 32 Hz, the box Fb is 34 Hz, and it uses a port diameter of 6" (which could be configured as a slot instead) with a length of 7".  The box volume is large but reasonable at 5.6 cu ft.  With this example, you can see that you normally need a larger enclosure and will add more weight to the vehicle to get such a smooth response.  But the benefits are a short port length and, of course, SQ.  I don't know if this particular sub is even made anymore, but it does work well to show an SQ response in a ported box.

Excellent post stevdart.  A lot of good advice there, I hope people read that.

My main question for the original poster is why would you want to try and build a ported system that would "sound sealed"?  If what you want is a slow natural 12 db/oct low-end roll-off below Fc with minimal SPL peakiness and the most musical response with Qtc around .707, build a sealed enclosure.    The whole purpose of using a ported enclosure is to extend the low-end output by  creating a lower F3 with a rapid roll-off below Fb.  Now if what you mean by "sound sealed" is eliminating the peak normally associated with ported enclosures, simply design the system to minimize it.  There is really nothing magical about it...

srtblue wrote:

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DYohn] wrote:

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Excellent post stevdart.  A lot of good advice there, I hope people read that.

My main question for the original poster is why would you want to try and build a ported system that would "sound sealed"?  If what you want is a slow natural 12 db/oct low-end roll-off below Fc with minimal SPL peakiness and the most musical response with Qtc around .707, build a sealed enclosure.    The whole purpose of using a ported enclosure is to extend the low-end output by  creating a lower F3 with a rapid roll-off below Fb.  Now if what you mean by "sound sealed" is eliminating the peak normally associated with ported enclosures, simply design the system to minimize it.  There is really nothing magical about it...

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I'm trying to get a ported enclosure to have the same accuracy and speed of a sealed box , with no blurring of the notes. But still retaining the sheer output of a ported design ..... kind of a best of both worlds thing.

stevdart wrote:

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edited by moderators, see post above

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srtblue wrote:

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Thanks much for the help ....

I'm trying to get a ported enclosure to have the same accuracy and speed of a sealed box , with no blurring of the notes. But still retaining the sheer output of a ported design ..... kind of a best of both worlds thing.

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What you describe above is most likely caused from the peaked frequency response of the ported enclosure.  When a fundamental frequency is boosted so much higher than it's transients, it will sound boomy and bloated.  Try listening to a system using a sealed sub, and then turn off all the higher frequency speakers so just the sub is playing.  You will most likely find that it sounds similar to your above description.

stevdart wrote:

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IMO, you can't use the manufacturer's data exclusively to build a ported box.  Some of them give some very detailed choices to choose from, and give you tested responses with each of them...which is great.  But most are very vague in the details and so you're left with some simple measurements to follow.  You have to ask yourself, "Who are they appealing to with this design?  Is it designed for high Q, more SPL, a noticeable peak in the response, to appeal to the majority of buyers who want more bass?

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I TOTALLY agree with the above.  The problem is that a lot of manufacturers recommended enclosures are coming from the marketing department.  I actually ran into this at work recently when I needed to design a ported enclosure for a pair of MTX 8512's.  The guys were telling me to just use the manufacturers recommended enclosure.  When I modeled it up, I got a huge 7 dB+ peak at 52 Hz with a steep rolloff below that.  To get a decent response with the subs, the enclosure was going to have to be 6.5 cubic feet which was too big.  Good info Steve!

srtblue wrote:

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Steven Kephart wrote:

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Sure it can with a proper enclosure design.  It's just that most ported enclosures are designed to be a bit peaky in the response, especially to keep the enclosure size down to a manageable size.  But a well designed ported enclosure can sound incredible.

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Ok Steven ..... Will you be kind enough to supply me with some details ?  Maybe a cut sheet and enclosure specs for a certain subwoofer you have heard that sounds as good as a great sealed design ....  The subwoofer enclosure in the photo is one I built to EXACT specs for a Diamond Audio D6 subwoofer.  It was probably the single best slot loaded design I've ever heard in my 23 yrs of car audio , but still fell short of the accuracy and speed of my Boston Acoustics Pro LF 12.5s in a sealed enclosure.  I'd LOVE to have the best of both worlds ....

Thanks

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Here's one that comes to mind: https://www.guidetohometheater.com/subwoofers/704way/index1.html

Steven Kephart wrote:

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srtblue wrote:

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Steven Kephart wrote:

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Sure it can with a proper enclosure design.  It's just that most ported enclosures are designed to be a bit peaky in the response, especially to keep the enclosure size down to a manageable size.  But a well designed ported enclosure can sound incredible.

---

Ok Steven ..... Will you be kind enough to supply me with some details ?  Maybe a cut sheet and enclosure specs for a certain subwoofer you have heard that sounds as good as a great sealed design ....  The subwoofer enclosure in the photo is one I built to EXACT specs for a Diamond Audio D6 subwoofer.  It was probably the single best slot loaded design I've ever heard in my 23 yrs of car audio , but still fell short of the accuracy and speed of my Boston Acoustics Pro LF 12.5s in a sealed enclosure.  I'd LOVE to have the best of both worlds ....

Thanks

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Here's one that comes to mind: https://www.guidetohometheater.com/subwoofers/704way/index1.html

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Just as an FYI, if you want flat response from a ported design, it generally requires a decent size enclosure.  Here's a model of the system I am currently building, using one of the new Adire drivers.  It's 5 cuft, ported at 19Hz.  This SPL level is with a 100 watt amplifier.  I expect this will come fairly close to your "sounds sealed" ideal.  There are many ways to do this with many different drivers.