Stuffed ports vs Variovent

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Gapx

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Stuffed ports vs Variovent
« on: 17 Jul 2020, 03:46 pm »
Hi guys,

as I added 2 Deephemp subs to my junior 8xrs I’m thinking about stuffing or exchange the ports for something like a variovent. Perhaps anybody has some insight as I already saw some people here stuffed their ports with nerf balls. So here is my thinking:

I think the ports deliver lower deep end which I won’t need with the duo subs but have a slight trade of in accuracy (?)
So my ports can go, now sealing the ports completely would lead to lower efficiency (afaik) which I don’t want, on the contrary more efficiency would probably help my set amp to work, and sealed speakers are normally not a good match for low watt triodes (afaik again ^^)

So I ended up with the question if just stuffing the ports with some kind of material (material suggestions are super welcome) is the best way to do this or if exchanging the ports for something like a variovent would be even better.

So if anybody has an insight on all this especially on variovent and materials would be super helpful. Otherwise I will just go down the rabbit hole of variovents and try things out. I just don’t want to mess up the frequency response or impedance curve.

So any insight is much appreciated, greetings Oli

AvsFan

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Re: Stuffed ports vs Variovent
« Reply #1 on: 17 Jul 2020, 04:26 pm »
Hi guys,

as I added 2 Deephemp subs to my junior 8xrs I’m thinking about stuffing or exchange the ports for something like a variovent. Perhaps anybody has some insight as I already saw some people here stuffed their ports with nerf balls. So here is my thinking:

I think the ports deliver lower deep end which I won’t need with the duo subs but have a slight trade of in accuracy (?)
So my ports can go, now sealing the ports completely would lead to lower efficiency (afaik) which I don’t want, on the contrary more efficiency would probably help my set amp to work, and sealed speakers are normally not a good match for low watt triodes (afaik again ^^)

So I ended up with the question if just stuffing the ports with some kind of material (material suggestions are super welcome) is the best way to do this or if exchanging the ports for something like a variovent would be even better.

So if anybody has an insight on all this especially on variovent and materials would be super helpful. Otherwise I will just go down the rabbit hole of variovents and try things out. I just don’t want to mess up the frequency response or impedance curve.

So any insight is much appreciated, greetings Oli

Hello Oli and welcome to AC and the Omega family! I PM'd you.

roscoe65

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Re: Stuffed ports vs Variovent
« Reply #2 on: 17 Jul 2020, 05:11 pm »
I don’t see why you would want to replace the ports with Variovents.  If you don’t like the solution you’ve permanently modified your speakers.

You can approach this in a number of ways:  Proac stuffed their ports with plastic straws.  Dynaco used fiberglass sandwiched between steel mesh.

Firstly, the vented box will not give you lower bass.  It will produce a higher bass peak, but actually roll off below the tuning frequency more quickly.  A sealed enclosure will not have as high a peak but will roll off much more gradually, often balancing room gain.  An aperiodic enclosure is a lossy sealed box, making the box seem larger to the driver since internal box pressure is reduced by leakage from the resistive port.  On the return stroke, the port actually slightly resists the driver movement.  If we stuff the port of the existing speakers, we are creating a hybrid between aperiodic and vented.  This can be used to our advanced to tune the enclosure.

I would start by stuffing the port completely to se how it sounds sealed vs. vented.  I would then remove the stuffing and slowly stuff a bit at a time until you like the tuning.

Another option is to cover the vent tube from inside the cabinet with a resistive fabric.  A square of fleece is stretched over the sport tube and held in place with a rubber band.  Listen to the result and add additional layers until you get the result you want.

Gapx

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Re: Stuffed ports vs Variovent
« Reply #3 on: 18 Jul 2020, 06:59 am »
Hi thanks for the help! I guess I will just start to expirement with stuffing the ports then. I thought that there could be a benefit of better airflow by using real variovents (diy’s) instead of stuffed tuned ports but wasn’t sure if that matters anyway.

Edit:
There is sadly not very much information on aperiodic design rules and calculations but I can imagine that there is no big difference between stuffing ports and using “flat stuffed discs” as there will not be much airflow anyway (?)

I take it that the whole thing seems to be matter of trial and error ^^

Btw.: I wouldn’t really need to alter the speakers permanently When using variovents as I could just unscrew the ports and fit some custom made discs instead, so pretty reversible.

Greetings Oli

roscoe65

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Re: Stuffed ports vs Variovent
« Reply #4 on: 18 Jul 2020, 11:50 am »
“Real” Variovents (no longer available) or resistive vents like you purchase from Madisound are just two plastic discs with resistive material (fiberglass) between them.  There is no magic.  You adjust the commercial vents by adding addtional vents to align with your enclosure.

Start with stuffing a rolled up sock, preferably New Zealand virgin wool, into the port first and see if you notice and like the change.

R

dB Cooper

Re: Stuffed ports vs Variovent
« Reply #5 on: 18 Jul 2020, 12:46 pm »
Dynaco used fiberglass sandwiched between steel mesh.

Firstly, the vented box will not give you lower bass.  It will produce a higher bass peak, but actually roll off below the tuning frequency more quickly.  A sealed enclosure will not have as high a peak but will roll off much more gradually, often balancing room gain.  An aperiodic enclosure is a lossy sealed box, making the box seem larger to the driver since internal box pressure is reduced by leakage from the resistive port.  On the return stroke, the port actually slightly resists the driver movement.  If we stuff the port of the existing speakers, we are creating a hybrid between aperiodic and vented.  This can be used to our advanced to tune the enclosure.

I would start by stuffing the port completely to se how it sounds sealed vs. vented.  I would then remove the stuffing and slowly stuff a bit at a time until you like the tuning.

Another option is to cover the vent tube from inside the cabinet with a resistive fabric.  A square of fleece is stretched over the sport tube and held in place with a rubber band.  Listen to the result and add additional layers until you get the result you want.

It seems like homebrew, seat-of-the-pants methods are unlikely to produce satisfactory, repeatable, channel-to-channel matched results. The results might be 'different', but 'better' is another matter.

I have seen it said that Dynaco adjusted their vents 'by ear'. They did not. They fed a low frequency square wave into the system and adjusted the damping while observing the output on an oscilloscope. I guess if you have an oscilloscope and a signal generator you could try it, but...?

All other things being equal, I would be reluctant to 'second guess' the designer of your speaker system if it was designed properly in the first place (especially irreversible mods that affect major variables like cacinet tuning). If it's easily reversible (like stuffing the port) then there's no real harm aside from the trickiy matter of getting both channels the same.

Gapx

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Re: Stuffed ports vs Variovent
« Reply #6 on: 18 Jul 2020, 02:52 pm »
Hi i get what you are saying my thinking was just that  the ports are designed to extend the low end which usually comes with a trade off and as I don't need the extended low end with my subs I thought I can omptimize things for my needs.

I have an osci and a linear mic but was looking for some insight of people who perhaps already tried this ;)

So with roscoe65 's input I  think I   will probably  start with stuffing the ports with wool and see what results I get.

Edit: for clarification: I am super happy with my omega speaker setup I just like to fiddle with things and read about ports and that there are multiple people here who stuffed their ports with a nerf ball when they added subs, I just wanted to optimize things and was looking for I input out of interest not of direct need ;)

Holygeezer

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Re: Stuffed ports vs Variovent
« Reply #7 on: 18 Jul 2020, 03:43 pm »
Have you considered emailing Louis directly and asking him what he thinks?

Gapx

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Re: Stuffed ports vs Variovent
« Reply #8 on: 18 Jul 2020, 04:05 pm »
Have you considered emailing Louis directly and asking him what he thinks?

Yup, did that but haven’t heard back for a while. Perhaps he’s in vacation or busy building beautiful speakers ;)

pstrisik

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Re: Stuffed ports vs Variovent
« Reply #9 on: 19 Jul 2020, 04:35 pm »
I simply stuff the ports with large tennis balls I found in a pet store.  The simple conclusion is that bass (mid-bass) is tighter and more defined while unstuffed is looser bass.  As I use Rythmik powered woofers and subs, both servo, the bass below the omegas is very tight and defined.  Stuffing the ports makes for a good match and much better sound in the low end to my ears.  It has also seemed easier to blend the bass units with the mains than when ports are open.





.......Pete (who is about to pack up my system this week for a move to WA  :o)

Gapx

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Re: Stuffed ports vs Variovent
« Reply #10 on: 20 Jul 2020, 10:31 am »
Ah that’s a nice idea, I already tried normal tennis balls but they were too small ^^

I did some frequency response measurements now with ports stuffed with wool and unstuffed and as there are some differences in the low frequency I still think i have to do some extensive listening tests with different stuffing configurations. It’s kind of hard to interpret as I would probably need to setup the sub again after stuffing and see what results lead to the best response curve with the subs on...

So thanks for stuffing material suggestions guys, I guess there is no easy solution but a rainy weekend with lots of time could bring the answer for me. Probably different in every room and setup too. So trial and error it is.

Greetings Oli

Gapx

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Re: Stuffed ports vs Variovent
« Reply #11 on: 20 Jul 2020, 05:57 pm »
No tennis ball but it’s soft (softly stuffed neoprene) and fits perfectly ;D

 Until I got more time on my hands I will listen for a while and see how the baseball sounds

Greetings Oli

planet10

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Re: Stuffed ports vs Variovent
« Reply #12 on: 20 Jul 2020, 11:42 pm »
Variovens are a cheap-ass way to turn a box sort of aperiodic. They work OK but rarely real well.

To push a vented box towards aperiodic, one can start adding some sort of damping to the vent. I ususally use fairly dense open cel foam, but drinking straws, polyfulff, fiberglass (will work but might puff out glass fibres — a variovent is simply some fiberglass squashed together by a mesh on either side.) even an old pai rof wool socks can be played with. Start will a little and add more until things are right.

If you can measure impedance you are looking to suppress the system resonance. There is also GM’s clik test (you’ll have to google that).

dave

Digi-G

Re: Stuffed ports vs Variovent
« Reply #13 on: 21 Jul 2020, 12:44 pm »
I simply stuff the ports with large tennis balls I found in a pet store.  The simple conclusion is that bass (mid-bass) is tighter and more defined while unstuffed is looser bass.  As I use Rythmik powered woofers and subs, both servo, the bass below the omegas is very tight and defined.  Stuffing the ports makes for a good match and much better sound in the low end to my ears.  It has also seemed easier to blend the bass units with the mains than when ports are open.





.......Pete (who is about to pack up my system this week for a move to WA  :o)

This was exactly my conclusion with my B&W 805's.  With the port open I got a bit deeper bass, but it was loose and I could hear it.  With the port stuffed the bass is tighter and sounds more controlled.  The 805s offer a foam plug to use, so it's not necessarily going against the designers intent.  Mine are paired with an SVS subwoofer, so squeezing those lower frequencies from my main speakers didn't mean much.

And like others have said, it's easy to try, reversible and doesn't cost much.  In my case it was an improvement.  YMMV.

Gapx

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Re: Stuffed ports vs Variovent
« Reply #14 on: 22 Jul 2020, 07:09 am »
Variovens are a cheap-ass way to turn a box sort of aperiodic. They work OK but rarely real well.

To push a vented box towards aperiodic, one can start adding some sort of damping to the vent. I ususally use fairly dense open cel foam, but drinking straws, polyfulff, fiberglass (will work but might puff out glass fibres — a variovent is simply some fiberglass squashed together by a mesh on either side.) even an old pai rof wool socks can be played with. Start will a little and add more until things are right.

If you can measure impedance you are looking to suppress the system resonance. There is also GM’s clik test (you’ll have to google that).

dave

I think i can build me a little diy probe to connect to my soundcard and measure the impedance with rew. Probably a good idea to include this when I do some more intensive testing, especially when dealing with flea power triode amps. Thanks for the hint.
Greetings Oli

Edit: my first impression of „Baseball-sound“ Is that it sounds quite nice! So definitely a good and really easy solution for the moment
« Last Edit: 22 Jul 2020, 11:20 am by Gapx »

doggie

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Re: Stuffed ports vs Variovent
« Reply #15 on: 25 Jul 2020, 11:32 am »
I have tried the supplied nerf balls with both sets of Alnico towers that I have owned, currently with the two driver HO's. I have used both speakers with a pair of SVS 12" subs.

Every time that I try it I find that it makes the sound congested with a loss of that remarkable Omega clarity.

Just my experience, in my room. Only one way to find out if you like it ...and a very cheap experiment.

YMMV :-)