IB makeover..........

[Rodny Alvarez]

SteveCallas wrote:

****, you went for PVC? Nothing at all wrong with that, but as you commented, it's going to be significantly heavier than say 10" Sonotube. Collo's work shows that a 1.5" flare on a 10" port should keep you totally safe. I don't see any problems with having one flare larger than the other - currently my sub only has a flare on the outlet, so you should have no issues.

$20 for two!! to me that was a good deal, I cant find sonotube around here.

[Ilkka]

Rodny Alvarez wrote:

Ilkka, do you think that it matters if there different or not??

You're good to go with asymmetrical flares. I doubt the difference is even easily measurable, not to mention audible.

[SteveCallas]

Rodny wrote:

$20 for two!! to me that was a good deal, I cant find sonotube around here.

Yeah, that is a good deal - looks thick too.

[Sonnie]

Yeah... great deal! I thought I was gonna have to pay 80 bucks for 6" and then have to cut it with a hack saw... in the rain. Lucky me and good ole Bradley plumbing saved the day and 80 bucks...

[Rodny Alvarez]

Left side 80% done!!
I guess I need some batting material or something else??











This is at the listening position, the blue is SLLT and green IB.
I will do more measurements next week, its late and I need some sleep , tomorrow we are going to Atlanta
Maybe monday if we get home early I can watch some movies.
This is with the same power (325Watts on each sub), maybe Tuesday I get my other amp.

[Sonnie]

Wow... that's about a 10-12db gain from 10Hz up to about 15Hz. I wonder though, does this mean the sound is generally going to be the same on most material, since there's not a terrible lot below 15Hz anyway.... or will you really notice more of a difference when you crank her on up to normal listening levels. Should be interesting to hear your thoughts... and get more power on the drivers as well.

[SteveCallas]

NICELY done That is some significant low end gain, and with no EQ bogging up the excursion down low. Hopefully it works pretty well at blocking out the bass upstairs compared to the IB as well. Looking forward to some impressions with low bass movies.

Can you provide a measurement up to 200hz with the speakers in play as well? Now that I know Sonnie's demo when you guys got the dual RLp-15 LLT running with the Plus/2s was roughly 6-7db hot, the effect you may be after is running your sub a little hot too. With the increase in headroom and decrease in low end distortion the port provides, you can run it blazingly hot if you so desire

[WillyD]

Stevie got his wish! Someone finally "ported their IB". Who knows Steve, this may be the start of a revolution.

[SteveCallas]

I won't jump the gun just yet, I'd like to make sure his measurement is repeatable and he gets similar results with #2. Assuming he does, there will still be resistance from the "elders" who will talk about a rolloff in the single digits being desirable. Based on low end sensitivity however, logic tells us that in the infrasonic range, it is better to stay flat as low as possible and have a sharper rolloff with more headroom rather than rolloff sooner with a shallower one and less headroom. Then you'll still have the faction that believes ports are the devil

But if all goes well, those who value performance more than myth or hype will see the benefits in such a design.

[WillyD]

Then you'll still have the faction that believes ports are the devil

Without a doubt.

So far though, the results look very promising.

[SteveCallas]

Yeah, and it would seem that as long as one has enough displacement and volume to play around with, it can be tuned wherever the natural -6db point is, even if it's in the single digits.

[Rodny Alvarez]

Any ideas on acoustic material I need for the box??


I read Collos speaker stuffing....................................................... The walls are high pressure, low velocity zones, so closed-cell foam rubber sheeting can absorb some energy. I used the same rubber that I utilised for the speaker mounting gaskets.

[Sonnie]

Why not use what I used?

[SteveCallas]

Any impressions yet? Is it working at blocking some of the bass from traveling to the rest of your upstairs? Is the additional low end noticable? Is running the sub hot creating the impact you are after?

[Sonnie]

Yeah... Rodny... tell'em all what you told me on the phone today. It's juicy!!! I bet we have some people enclosing their IB's....

[Rodny Alvarez]

SteveCallas wrote:

Any impressions yet? Is it working at blocking some of the bass from traveling to the rest of your upstairs? Is the additional low end noticable? Is running the sub hot creating the impact you are after?

I played some movies and the noise in the living room is a lot better! (less noise), watched scenes from Jurassic Park 3 (Plane crash and the dinosaur fight) the bass has more........ punch...impact...feel.., however you can tell were the bass is coming from when listening to the SLLT, with the IB you can't , I don't know if the location of the SLLT, IB has something to do, because they are in opposite sides of the room (left and right)
When I listen to the IB to me it sounds like...... when you have a sub with not enough power,(like is to loose) I don't know if some of you guys agree with this or understand what I'm saying!!
To me a sub sounds a lot better with more power!! this is coming from my experience with car stereo, I'm little fresh on HT so this maybe different then car stereo.
Steve, I'm not running the sub hot, don't have the other amp,( I will tomorrow )

I need to do a house curve!!

Here is sweep with the mains....
NO/EQ


W/EQ


Nearfield 12" from the subs/port

Nearfield IB....


Nearfield SLLT sub.....


Nearfield SLLT port.....

[SteveCallas]

Rodny wrote:

I played some movies and the noise in the living room is a lot better! (less noise)

That's good to hear

Rodny wrote:

the bass has more........ punch...impact...feel

Excellent.

Rodny wrote:

however you can tell were the bass is coming from when listening to the SLLT, with the IB you can't , I don't know if the location of the SLLT, IB has something to do, because they are in opposite sides of the room (left and right)

Hmm, maybe you do need to line that enclosure space with some batting or foam. I'd imagine that would do the trick.

Sonnie wrote:

Rodny... tell'em all what you told me on the phone today. It's juicy!!! I bet we have some people enclosing their IB's...

So I take it so far that it is a noticable improvement?

[Rodny Alvarez]

So I take it so far that it is a noticable improvement?

Its all good!!!!! can't wait to do the other side and add the other EP 2500
I need to do the flares and add some acoustic material.

[collo]

Hi there Rodney,

I just responded to your PM about closed cell foam.

Your cred got an instant bump once I realised you were the dude doing the IB > ported conversion.

This is just the type of before and after analysis that furthers the science for all of us.

Coming in late as it were, I missed the discussion about inner and outer flare sizes. As it happens, I recently did some testing and found:

For speeds below 70% of the core limit, the radius of the inside flare can be 15 - 20% smaller than that of the outside flare

Admittedly this was only tested on small ports, but I think it should extrapolate fairly well to larger ports. The resulting sizes are in line with what you find in the commercial offerings.

I had hoped for a larger difference, but I guess the inrush of air can only mask so much turbulence. I also read a B&W white paper, which apart from the marketing spin, suggested that air that is too turbulent can be sucked back in on the next half cycle, triggering further turbulence.

My experimental notes here

The B&W paper here

regards
Collo

[Rodny Alvarez]

Just finished installing the amp mono to the SLLT, there was about 6db gain, this is with only one side, maybe this weekend I can do the other side.
Look at the dip at 97hz, you guys think I should worry about it or just ignore it until I do the other side?

This is with the mains...............crossover set to 80hz and the mains set to small.

[WillyD]

God that is a nice looking FR.

[Sonnie]

Yes... one to dream for.

Rodny, I would wait until you get the other one done before worrying about that dip at 97Hz. You can probably adjust the bass tone control on the receiver to compensate for it.

[SteveCallas]

If that response is natural without any EQ, I wouldn't even consider adding EQ to the chain to fix that dip. You can experiment with subwoofer distance in your processor to try and level it out a bit, as all that really does is adjust phase - I had to change my distance to level out my crossover region, the end result is not the real distance of the sub, but it gives the flattest FR. If that dip is with EQ in the chain, then I don't see any reason not to fix it. I'd focus on getting the second one done first though.

This project is looking like a huge success, you not only are getting more headroom, lower distortion, a flatter and deeper extending natural FR, and more impact, you are also minimizng the bass spillage into the rest of your home. Hopefully some will take the concept more seriously now

[SteveCallas]

brucek wrote:

Are you saying that conventional IB just isn't the way to go, because from the results here, it sure looks like it?

My point of view is that unless you live in a smallish sealed concrete bunker, a sealed driver is gonna start rolling off at some point, even with a lot of EQ. Unless the enthusiast listens at pretty tame levels or has drivers by the dozens, bringing down everything above 10hz to keep the response flat seems like a big compromise. The better solution, in my opinion, is to port it and tune it where the natural sealed response has dropped off quite a bit. You gain all the advantages I listed in my previous post. You get a sharper rolloff below tuning, but if you were already -15db at 5hz or something like that, does it really even matter? Is being -15db at 5hz or some equivalent worth more than the advantages you gain from porting? My guess is that the majority of enthusiasts would say no. When we are talking about the infrasonic range, it would seem to make much more sense to be flat and very strong to some frequency X than it would to start rolling off at X+10hz with a shallower rolloff.

In more audible regions, like 30hz or so, a sharper rolloff has legitimate consequences, as there may be audible ringing when a frequency below the tuning is asked to be reproduced. When we're talking about a tuning like Rodny's, the cycle times of such low frequencies are high to begin with (in relation to higher bass frequencies) and the reproduction is tactile, not audible. So I'm saying the difference created by more clean headroom and a deeper, flatter FR from a <15hz tuning on up will be significantly more noticable than any effects from a sharper rolloff in the single digits.

And keep in mind that the more drivers and larger an adjacent space one plans on using, the lower the tune they can get away with.

[brucek]

My point of view is that unless you live in a smallish sealed concrete bunker, a sealed driver is gonna start rolling off at some point, even with a lot of EQ. Unless the enthusiast listens at pretty tame levels or has drivers by the dozens, bringing down everything above 10hz to keep the response flat seems like a big compromise. The better solution, in my opinion, is to port it and tune it where the natural sealed response has dropped off quite a bit.

Yeah, I gotta say I agree. Back when I first heard about IB and all the drivers required and the EQ to make it flat, etc, etc, I just thought I much preferred the big old water heater and a port. It just seemed more sensible. Ugly, but sensible.

The below tuning protection is a problem with that, but I like your low tune theory to remedy it. I still think with much of todays electronics though, the stuff goes close to DC in its response, so people have to be careful to get a low enough tune to not run into the problem (or they'll need a HPFilter of some sort). I know you said the electronics will handle the rolloff, but I wouldn't count on it. The BFD has a flat response down to 5Hz and is only off a bit at 2Hz.......

brucek

-----------------------------
ADMIN NOTE:

POSTS were moved from this thread to HERE.

We were hijacking the thread and thought it best to talk elsewhere.

brucek