Center channel speaker design pet peeve.

[bootman]

Can some one explain to me why speaker designers still continue to rear port a center channel speakers considering where it is going to be placed >90% of the time?
Front ports or just seal it!

I honestly don't get it.

[DYohn]

What's not to get? It extends the low frequency response of the system and when designed properly rear ports function just fine. The port does not need to be facing the listener to work...

[bootman]

So rear ported when you put a speaker in another box is OK?
Curious why not just go sealed since aren't we just closing off the port in a tv cabinet at this point?
...and I know sealed would require a larger size and more power for a similar response of a ported design but this would apply in free air, no?

[DYohn]

Jan 2, 2016 12:27:07 GMT -5 bootman said:

So rear ported when you put a speaker in another box is OK?
Curious why not just go sealed since aren't we just closing off the port in a tv cabinet at this point?
...and I know sealed would require a larger size and more power for a similar response of a ported design but this would apply in free air, no?

"Putting it in another box"? Not sure I follow... The purpose of porting is to lower Fb (system resonance) of the speaker system, enabling more low frequency extension from the woofer (allowing use of smaller woofers in many cases to achieve desired response) and yes, to increase system efficiency. The direction of the port doesn't matter all that much in a typical home installation and when it is facing a rear wall the effect often results in higher perceived bass output than if the port is forward facing. There are many phase-related reasons why port direction can be important (especially in subwoofers) but bottom line is if the desired result is to get below 100Hz with, say, a 4 or 5 inch midwoof, then the direction of the port for a CC system is pretty meaningless. It just needs to be ported. Getting similar response with a sealed system usually requires larger woofers and/or more power handling (i.e. = more expensive system to manufacture.)

[Lsc]

Jan 2, 2016 12:01:30 GMT -5 bootman said:

Can some one explain to me why speaker designers still continue to rear port a center channel speakers considering where it is going to be placed >90% of the time?
Front ports or just seal it!

I honestly don't get it.

I don't get it either.

[knucklehead]

I get what you're saying. The problem is designing a speaker compact enough to satisfy the consumer and still get to 80hz which is the THX Audyssey and other standards for the crossover point. Many speakers just don't have the room for a front facing port. There may be something about rear porting the speaker that is cheaper to manufacture than finding room on the front side. Some of the better brands are rear ported but often come with bungs to plug up the ports so it can be placed on a wall or inside a cabinet. Sealed speakers or front ported are a better choice in such cased. I'm sure some consumers don't know and don't care about cabinet resonance. Any speaker mounted on or in a cabinet should have a pad to help absorb resonances.

[novisnick]

Jan 2, 2016 13:03:43 GMT -5 Lsc said:

Jan 2, 2016 12:01:30 GMT -5 bootman said:

Can some one explain to me why speaker designers still continue to rear port a center channel speakers considering where it is going to be placed >90% of the time?
Front ports or just seal it!

I honestly don't get it.

I don't get it either.

Yall know me as a peace maker, so let me try,,,,,,,,,,,,

My center channel is ported and sits beneath the TV, but is open in the back. Its about 28" off the wall.

That said, the 5.1 music that I do listen to on occasion sounds marvelous!!! Yes, I must be the exception vs the norm if 90% of all center speakers are used in an inclosed environment.

I do think the ported sounds better for deeper voices in HT also.

Theres my two cents folks! 

[LuisV]

Since most entertainment centers, consoles, etc, have an enclosed shelf for the center channel, that placing the center channel speaker with a rear port would not recommended as the ports are firing into a rear wall. If all centers were front ported, they would therefore be good for all applications.

[DYohn]

Ports don't "fire," by the way. That's a car audio myth. Ports resonate, like a soda bottle being blown across (look up Helmholtz effect.) So the only difference between a front port and a rear port or a top port or any other kind of port (or passive radiator) is the phase difference between it and the woofer. In a bass-reflex design the sound created by the port is 180 degrees out of phase with the woofer in the first place (no matter where it is placed) making it is actually an easier design to rear port than to front vent (front venting requires more critical enclosure size considerations to compensate for this phase difference.)

Now the effect of placing a bass reflex loudspeaker inside a small enclosed space (such as you are describing in a media center) can create unwanted sound due to the vent activating the enclosed space's resonant frequency. If the resonance is audible the likely result is a system with too much "boom." But there is no problem with a rear vent being very close to a rear wall - in fact it can increase the dbSPL of the vent if that is desired. The idea of closing a vent with a plug converts the system into an "sealed" enclosure, changing the system resonant frequency and roll off and most likely reducing the net low frequency output. This might be desirable for some center channels, I suppose.

[LuisV]

Jan 2, 2016 14:44:49 GMT -5 DYohn said:

Now the effect of placing a bass reflex loudspeaker inside a small enclosed space (such as you are describing in a media center) can create unwanted sound due to the vent activating the enclosed space's resonant frequency.

I believe that is what he was complaining... um... indicating is his pet peeve.      The rest as you described, I believe is understood...

[Perpendicular]

I've never owned a speaker that was ported to the front but have always liked the idea until yesterday when I watched The Home Theater Geeks Episode 281 with guest Jack Oclee-Brown from Kef where he explained why rear ports are better, overall, than front ports. Apparently, it helps to shield the 'colored' midrange coming through the port. He talks about why this is important and it can be found in about the last 3 minutes of the show. twit.tv/shows/home-theater-geeks/episodes/281?autostart=false

[bootman]

Jan 2, 2016 13:19:49 GMT -5 novisnick said:

Jan 2, 2016 13:03:43 GMT -5 Lsc said:

I don't get it either.

Yall know me as a peace maker, so let me try,,,,,,,,,,,,

My center channel is ported and sits beneath the TV, but is open in the back. Its about 28" off the wall.

That said, the 5.1 music that I do listen to on occasion sounds marvelous!!! Yes, I must be the exception vs the norm if 90% of all center speakers are used in an inclosed environment.

I do think the ported sounds better for deeper voices in HT also.

Theres my two cents folks! 

Look at many pics of folks HT setups and they tend to put rear ported centers in entertainment units with no open back.


Here is a few good examples:







And it is very typical of a customer installation.

[Gary Cook]

I agree with the premise, rear porting of a centre speaker appears, in a practical installation sense, to be a bit silly. But what are the alternatives, no porting, side, top, bottom or front? Side, top and bottom all have the same issue as rear, cabinet clearance, so that leaves the two options of no porting or front porting. No porting has frequency, size and power requirement limitations as well as socially matching what are most likely ported other speakers in the set. Whilst front porting has phasing issues. By choosing rear porting, over the alternatives, speaker manufacturers are selecting the lessor of the evils. I run an open back rack for that reason, previously I have cut a hole in the rear of enclosed cabinets to allow the centre speaker port some breathing room, which as DYohn has pointed out doesn't require a lot of space. Best to refer to your speaker manufacturer for their recommendations.

Happy New Year
Gary

[bootman]

Jan 2, 2016 18:07:03 GMT -5 Gary Cook said:

I agree with the premise, rear porting of a centre speaker appears, in a practical installation sense, to be a bit silly. But what are the alternatives, no porting, side, top, bottom or front? Side, top and bottom all have the same issue as rear, cabinet clearance, so that leaves the two options of no porting or front porting. No porting has frequency, size and power requirement limitations as well as socially matching what are most likely ported other speakers in the set. Whilst front porting has phasing issues. By choosing rear porting, over the alternatives, speaker manufacturers are selecting the lessor of the evils. I run an open back rack for that reason, previously I have cut a hole in the rear of enclosed cabinets to allow the centre speaker port some breathing room, which as DYohn has pointed out doesn't require a lot of space. Best to refer to your speaker manufacturer for their recommendations.

Happy New Year
Gary

How about a nice sealed design with drivers that can take the power needed to get to proper levels?

Too simple?

[Lsc]

Jan 2, 2016 18:32:26 GMT -5 bootman said:

How about a nice sealed design with drivers that can take the power needed to get to proper levels?

Too simple?

You should get a job at Revel .

That's what my C208 is...it's a big sealed center channel and my mains F208 are ported.

At one time I put the port bungs on the F208 and the bass tightened up a bit, but I later took em off bc they go lower.

[bootman]

Jan 2, 2016 18:55:40 GMT -5 Lsc said:

Jan 2, 2016 18:32:26 GMT -5 bootman said:

How about a nice sealed design with drivers that can take the power needed to get to proper levels?

Too simple?

You should get a job at Revel .

That's what my C208 is...it's a big sealed center channel and my mains F208 are ported.

At one time I put the port bungs on the F208 and the bass tightened up a bit, but I later took em off bc they go lower.

Yup, that to me (at least) is a great example of a center channel design.
It's performance won't be affected greatly by closed back cabinet placing.


I put this in the stupid question section not because I don't know the virtues of ported vs sealed, just why so many rear ported designs get placed so "incorrectly".
Yes we have room correction, but I just go "bleh" every time I see a new rear ported center design.
So this is my stupid question to my stupid reaction on these designs.

[Axis]

What is everyone's thought on this having a rear port. I would want to install it in a closed TV stand. May have to rethink.

Airmotiv C1 ($249 ea.): Three-way center channel loudspeaker with Airmotiv™ folded-ribbon tweeter. The C1 features a 3-way ported design, dual 5.25” woven Kevlar® woofers, one 3” woven Kevlar® midrange, and one 25mm x 32mm Airmotiv™ tweeter.

[copperpipe]

Jan 2, 2016 15:01:50 GMT -5 Perpendicular said:

I've never owned a speaker that was ported to the front but have always liked the idea until yesterday when I watched The Home Theater Geeks Episode 281 with guest Jack Oclee-Brown from Kef where he explained why rear ports are better, overall, than front ports. Apparently, it helps to shield the 'colored' midrange coming through the port. He talks about why this is important and it can be found in about the last 3 minutes of the show. twit.tv/shows/home-theater-geeks/episodes/281?autostart=false

Thanks for the link to that video; incredibly fascinating. I always thought the Blades were "reaching" a little, moving into "different for the sake of different" and designed to separate rich people from the money, but never realized why those speakers are shaped the way they are.

I love the emphasis on engineering that Kef has, they don't just shove a tweeter + driver in a box and call it a day, but they actually model it all using computers and understand exactly what they're doing and why they're doing it.

[novisnick]

Jan 2, 2016 16:15:09 GMT -5 bootman said:

Jan 2, 2016 13:19:49 GMT -5 novisnick said:

Yall know me as a peace maker, so let me try,,,,,,,,,,,,

My center channel is ported and sits beneath the TV, but is open in the back. Its about 28" off the wall.

That said, the 5.1 music that I do listen to on occasion sounds marvelous!!! Yes, I must be the exception vs the norm if 90% of all center speakers are used in an inclosed environment.

I do think the ported sounds better for deeper voices in HT also.

Theres my two cents folks! 

Look at many pics of folks HT setups and they tend to put rear ported centers in entertainment units with no open back.


Here is a few good examples:







And it is very typical of a customer installation.

I can't help those that don't know or refuse to configure there system property!
How much about audio do you think the designers of these racks really know ??
Proper configuration/implementation isn't always pretty!! Aren't we, audio enthusiasts, more concerned with sound then looks??

[Gary Cook]

Jan 2, 2016 18:32:26 GMT -5 bootman said:

Jan 2, 2016 18:07:03 GMT -5 Gary Cook said:

I agree with the premise, rear porting of a centre speaker appears, in a practical installation sense, to be a bit silly. But what are the alternatives, no porting, side, top, bottom or front? Side, top and bottom all have the same issue as rear, cabinet clearance, so that leaves the two options of no porting or front porting. No porting has frequency, size and power requirement limitations as well as socially matching what are most likely ported other speakers in the set. Whilst front porting has phasing issues. By choosing rear porting, over the alternatives, speaker manufacturers are selecting the lessor of the evils. I run an open back rack for that reason, previously I have cut a hole in the rear of enclosed cabinets to allow the centre speaker port some breathing room, which as DYohn has pointed out doesn't require a lot of space. Best to refer to your speaker manufacturer for their recommendations.

How about a nice sealed design with drivers that can take the power needed to get to proper levels?
Too simple?

Sounds simple, but having spent some time talking to my speaker guy (Edward at Adelaide Speakers) when we were deciding on the spec for my centre speaker, it wasn't as easy as it sounds (sic). Firstly there was the sonic signature, it is apparently very tricky to get a sealed enclosure design to sound the same as a ported design thoughout the frequency range. Since I already had transmission line loaded speakers in the other 4 positions as well as a dual ported sub, it was a no brainer to go with a ported design for the centre. Then there is the question of amplifier output, AVR's running out of grunt matching the non ported centre speaker with the ported others. This obviously doesn't apply in my case as I have plenty of grunt in reserve, but it may well do to the majority of potential customers.


Happy New Year
Gary