Block ports

[leif]

Hey folks,

SVS is selling subwoofers like hot cakes in Norway these days. And they seem to be very good, according to the owners.
One of the things some models offer, is variable port tuning.
One model has 3 ports, and if one block one or two of them, the tuning will be lower.

So my question is: Will that be the same thing with my sub? It has 3 ports. What will happen if I block one, two or all of them?

As said earlier on this forum, I miss floor shaking movements on low frequencies. Punch in my body when the bas drum kick in.
And I dont get that, even with a pair of 4430 and a B460 with plenty power. And I dont know why...


Leif
http://avforum.no/minhifi/show.php/imm

[Guido]

Don't mess with the B460 tuning!

You need an S1S-EX

[brutal]

on the built-in amp.

Awesome subs.

[yggdrasil]

I have forgotten what you are driving the B460 and 4430's with.

Are you sure the woofers don't work against each other? Overlapping frequencies and out of phase.

Both your systems should be able to give you what you want.

On the subject of blocking ports: Each port you block will give lower tuning frequency. Except when you block all ports, the tuning frequency will be higher.

Generally lower tuning frequency will give more shaking and less punch.

[leif]

I have tried to swithc phase. But the odd thing is that it is almost not possible to hear the difference. I have a feeling it is a room problem. But I have also tried with different placement, without any better result.

I think that one day when I have lots of time, I will try to hook up my system in a different room, to see what happens.
I have a feeling that the floor may be absorbing the low frequencies, I have no other explanation.

Powered with Nakamichi PA5e II (4430) and a bridged Adyton XP3d, a heavy duty PA amplifier, (widely used in big consert places in Norway, at places like Rockefeller, Sentrum Scene etc.).


Leif

[yggdrasil]

Your B460 is responsible for making the floor and everything else shake.

The 4430's should take care of the punching.

You'll probably have to do some systematic testing.

I would take the B460 out of the equation.

Then do some checking with only the 4430's. What did change?

Didn't you recone / refoam the 2235's a while back? It can't hurt to recheck the internal connections. My brother got a pair of 4333's very cheap a few years back due to wrongly wired internals.

If you suspect your room - a drawing with dimensions would be helpful.

[leif]

Yes, I refoamed both the bass speakers when I bought them.
Not many days ago, I bought a brand new 2235H and replaced one of them.
I took both speakers today and put them face to face, as close as I could get. Put on bass music, to see if the bass elements was in phase. They were.
I belive the room (and floor) is the problem. I have a pretty large floor, and it is a basement under. So when playing loud, the entire floor is shaking, and perhaps also absorbe the "punch". I will bring the speakers down in the tv room in the basement one day. A day I feel like doing some excersice. Lifting the 4430 and the B460 is not a easy job. Trust me!


Leif

[Ian Mackenzie]

Leif,

If you block off some of the ports it may cause audible chuffing with high velocity air movement in the port.

I suspect the room is the issue.

Ian

[Steve Schell]

Leif, your problem reminds me of the situation I had after I bought my house. I couldn't get decent sounding (or feeling) bass in the living room no matter what I did. At one point a friend had brought over four Tannoy Wildcat cabinets and we hooked them up. He asked what was going on, as we had four prosound 15s pumping and still little sensation of bass.

I eventually determined that it was a combination of a saggy floor and lack of room treatment. First I rebuilt the floor, securing the sub flooring to the joists at each junction with deck screws then gluing and screwing a layer of 3/4" plywood on top. That helped quite a bit.

Next I began adding as much absorptive material to the room surfaces as possible. I have continued to add more over the years and the bass has subjectively improved with each addition. It seems that if the room is too live the midrange energy recycles and has a slow decay, overwhelming the bass energy.

[opimax]

this sounds just like my house!!! I have my 460 powered by a bridged adcom gfa 555 seeing 600w. My Velodyne (2nd sub) is a 1200splr, 1000 watts 2000 dynamic. My 250 are powered by a Perreaux 300 per channel. the subs are being run by a velodyne SMS1

My system is run w/the bass +6db on the fronts and I can't guess how far up the subs are but they are probably up there, this sounds "normal", not bassy. I can get some low rumble w/movies but regular music just isn't right, it must be my house which is not well made to begin with!! I tried some homemade treatment piled in the corners, seemed better but not what one would think at all

Mark

[leif]

Yes, my room is lacking of absorbing things. Big hard surfaces, oak floor without carpet, and a large cieling that is all just flat.

I have 4 4628b upstairs at the guestroom. I will bring them down a day to see how that works. Never tried them in my livingroom. I use them for company party, and if I shall make a presentation of my aid work (My African Aid Organisation).

you can view my stuff here:
http://avforum.no/minhifi/show.php/imm

[Don C]

One of these inexpensive Rabos kits can help with measuring the room to see what's happening to your bass.
http://www.harmanaudio.com/search_br...%20KIT&status=