Front ported, Rear ported or Sealed speakers

[krisztoforo]

I have another thread going in the Setup forum, but this seems like a better thread for this question...I have a pair of rear ported bookshelf speakers (Infinity Kappa 200) that I want to use in our future custom wall-cabinet/shelf system. Now I understand that rear-ported speakers are a pain to get working right in such a location, but as I understand the port is designed so it will give you a bass extension around the tuned frequency and it doesn't do much above that frequency (is this true?). If it's true can I just use my sub to effectively take the burden of reproducing its lowest octave or so off of the Kappas thus taking the port out of the equation?
Thanks for your time.

 

[j_garcia]

You can simply plug the ports on basically all ported speakers. The downside being you lose that extension, but mitigate your problem of having rear ports. Raising your x-over point will not solve the problem, it will create new ones.

 

[krisztoforo]

You can simply plug the ports on basically all ported speakers. The downside being you lose that extension, but mitigate your problem of having rear ports. Raising your x-over point will not solve the problem, it will create new ones.

Cool, I can certainly do that. But for my understanding, why would raising the x-over create new problems? If I have a port tuned to let's say 60hz and I cross the speaker over (in the receiver) at 80hz or 100hz, then effectively I won't send any signals to the speaker that would "activate" the bass extension of the port. Or do I misunderstand the whole concept?
What does a port do in frequencies way higher than the tuned freq?

 

[j_garcia]

I should have said: if you have to raise the x-over too high, it can create new problems. If you have the ability to go with 80hz, you should be OK, but when you get the sub up to a x-over point of about 100-120Hz, you will usually start to have response issues and the ability to localize the sub - meaning you start to hear the transition between the mains and the sub as well as the sub becoming directional in the higher ranges. Also, since an X-over isn't an all or nothing deal, you will still get sound at the tuning point of the speaker - you would need to go more than 1 octave above the tuning point with a semi-steep x-over slope to effectively "remove" sound at the tuning point.

 

[krisztoforo]

I should have said: if you have to raise the x-over too high, it can create new problems. If you have the ability to go with 80hz, you should be OK, but when you get the sub up to a x-over point of about 100-120Hz, you will usually start to have response issues and the ability to localize the sub - meaning you start to hear the transition between the mains and the sub as well as the sub becoming directional in the higher ranges. Also, since an X-over isn't an all or nothing deal, you will still get sound at the tuning point of the speaker - you would need to go more than 1 octave above the tuning point with a semi-steep x-over slope to effectively "remove" sound at the tuning point.

OK, got it, thanks for your help!

 

[morkys]

In terms of the original question, I can relate. I was once a sealed speaker proponent. I have not been converted, but I now like ported too. I once had a pair of sealed Boston Acoustics A70 II's and they were 2-ways with an 8 inch woofer and fairly large enclosure for a "bookshelf" speaker. They had great bass, of course, I blew the woofers more than once. I now have a pair of PSB Image 6 T's and I like them more. Although I sometimes suspect they don't have quite the same low bottom end, they still sound better than the older bostons. I think I will upgrade to the new T65's because they go ever so slightly deeper and are a bit more efficient. At the same time I will likely get an outboard amp too. Anyhow, it's all about the individual speaker design, but I can say this. PSB Image tower speakers give you some of the most bass and are one of the most efficient speakers with a smooth sounding designs out there. They give you lot's of efficiency and bass per dollar spent. I know I love mine

 

[hemiram]

I have always preferred sealed over ported, at least in speakers I could possibly afford. The bass "tightness" is the reason, of course. It's easier to add power and a sub to make up the efficiency difference, and the low end extention. A friend of mine just bought a pair of NHT Classic 3 speakers and I really like them a lot, at least at his house. I'm going to talk him into letting me borrow them when he goes to Calif. to visit his and his wife's folks from the 24th to Jan 10th. If I like them as much in my room, I'm going to buy a pair and move the SVS SBS-01s I have in front now to the rear surrounds, then it will be new sub time. My only real big problem is my receiver having to be reset and wiping out hours and hours of tweaking and setting presets and levels, etc twice now. I may contact Yamaha on this, as it's getting really annoying.

 

[furrycute]

I don't recommend plugging up your rear ports, or your front ports, or any kind of open port for that matter. Those ports are there for a reason. If the speaker designer had a sealed enclosure in mind, he would have given you a sealed speaker in the first place, instead of designing a ported speaker.

The drivers in a ported design are designed to function in a ported environment. By plugged uping those ports, you are at risk of damaging your speaker drivers.

 

[tman]

Does porting affect damping of woofer?

Novice question, but does porting affect the damping of the woofer significantly?

My understanding was that sealed enclosure the compression of gas acts as a spring (acoustic suspension). If speaker was designed to be at the balance between over-damped and under-damped and you plug the port, will you move it toward over-damped or is the porting small effect vs. the fiber fill of the speaker? Taking it a step further if you think a speaker sounds too boomy, what would taping up (duct tape) some of the cross-section of air flow do to the sound?

 

[gmichael]

Duct tape? Most likely a flapping or buzzing sound. A rolled up sock may be a better way.
Why do you want to plug them?

 

[tman]

Just curious to do experiment to try to understand how speakers work.

I'm looking into buying bookshelf speakers. One of the manufacturers was kind enough to give detailed replies to questions. He mentioned his speakers are by design slightly underdamped and gave some reasons for this choice. I was just curious to do an experiment for my ear what damping does to sound character starting with slightly underdamped hopefully going to slightly damped. Duct tape was a glib statement-- sock is good, or I would think placement as well. I am just wondering what else you change other than the damping of the speaker and how much you change it with a sock or with something that changes the cross-section for air flow through the port.