(4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

[Tin_Ears]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

Nice Practisix.

[nyt]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

Nice Practisix.

Close ;) pentacon six, with the cz jena zebra lens. That one is the wife's.

[Tin_Ears]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

Close ;) pentacon six, with the cz jena zebra lens. That one is the wife's.

The prism finder threw me. :D

[badman]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

Oh my, I don't even know where you get these ideas from to be honest. What do you mean by high energy drivers? Drivers don't have energy. Did you mean mass? Maybe excursion? You realize the wavelength of sound at 100hz is about 12 feet yes? The lowest resonant frequency of this box based on dimensions (longest interior side is 44.5") is over 150hz. On subs that are crossed at 80hz with a steep filter, this is irrelevant. But while we're discussing it, please tell me how an inch of damping material is going to affect a 7.5 foot sound wave. I would like to be enlightened on this subject, as clearly this is something I have not dealt with before as this is my first time designing, building, and measuring speaker enclosures.

Also, this is a ported enclosure, it's DESIGNED to have the air resonate. Fortunately for me, that resonant frequency is 15hz. I thought we covered this.

.... why? The bracing in place is functioning as intended. Do you honestly thing you can stretch a piece of 3/4" ply? As to adding MDF, the boxes already weigh over 200lbs without the drivers. You'd have to be crazy to add anything to it, especially something that will bring absolutely zero benefit.

An enclosure doesn't need a full wavelength to have a resonance. A quarterwave is plenty to have an extremely strong resonance.

The vent is a tuned resonant mass. That has nothing to do with enclosure standing waves, or shouldn't, in competent designs.

You don't need to "stretch" the panel to have vibrations. The balloon mode may be reasonably well dealt with in your bracing schemes, and other resonances potentially above the passband, but I wouldn't bet on it. Resonances, be they panel or standing waves, take time to dissipate, and don't show up very well on a simple FR measure, while impacting the performance of the sub.

Stuffing can be effective down into the lower registers- particularly when it comes to improving the decay behavior of standing waves, as the wave will encounter stuffing repeatedly and speed up the decay, lowering coloration.

[nyt]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

An enclosure doesn't need a full wavelength to have a resonance. A quarterwave is plenty to have an extremely strong resonance.

I calculated the lowest frequency 1/4 wave resonance in the post.

The vent is a tuned resonant mass. That has nothing to do with enclosure standing waves, or shouldn't, in competent designs.

As designed, the first resonance of the box is far enough out of the frequency range this will be used in for it not to matter. The first resonant frequency of the port is much lower than the box, coming in at 108hz.

You don't need to "stretch" the panel to have vibrations. The balloon mode may be reasonably well dealt with in your bracing schemes, and other resonances potentially above the passband, but I wouldn't bet on it. Resonances, be they panel or standing waves, take time to dissipate, and don't show up very well on a simple FR measure, while impacting the performance of the sub.

I wasn't talking about the panel, was talking about the bracing, since it was suggested to use 2x4s instead of the pieces of 3/4" ply.

Stuffing can be effective down into the lower registers- particularly when it comes to improving the decay behavior of standing waves, as the wave will encounter stuffing repeatedly and speed up the decay, lowering coloration.

While this is true, the effect is too limited to make me want to put the effort in. The first resonance of the enclosure (44.5" interior side) is over 150hz. Measurements show no ugly decay issues (spectrogram posted earlier).

And in other news, with the help of my wife I picked up some wood for cabinet #2 tonight. After having the first inside, and listening to it, I can't wait to upgrade the rest of my enclosures.

[badman]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

Try re-calculating what wavelength 4x44.5" is. It's absolutely not much higher than the first port resonance.

Also, the bracing can allow for deflection without "stretching", but you're right, I was talking panels while you were talking bracing.

I'm not arguing with your decisions, having subs like that be any heavier is not a treat, I'm only saying that there are legitimate concerns with your construction (which are definitely more applicable if you were running them higher up).

[nyt]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

Try re-calculating what wavelength 4x44.5" is. It's absolutely not much higher than the first port resonance.

Also, the bracing can allow for deflection without "stretching", but you're right, I was talking panels while you were talking bracing.

I'm not arguing with your decisions, having subs like that be any heavier is not a treat, I'm only saying that there are legitimate concerns with your construction (which are definitely more applicable if you were running them higher up).

Where are you getting 4 x 44.5 ? Resonances occur when a dimension is half of a wavelength.

44.5" = 3.7 feet. A 3.7 foot wave is about 302hz. Half of that is 151hz, the lowest frequency of the box.

I've built plenty of subs before, I've taken these things into consideration. There are no points on the box further than 10" from bracing. What I generally see on the forums are enclosures that are incredibly over braced, which is what the prevailing hive wisdom states. Many of us who experiment with these enclosures have come to the conclusion that complex bracing isn't necessary in cases like this, and what I've done here has proven more than adequate.

If I was running these higher up, the first port resonance would be the first concern, then the first resonant frequency of the box. If I was running them higher, I would include damping to combat the box resonances. Excluding it does not make any audible difference. You can actually see the box resonance discussed if you look REALLY close at the spectrogram posted. The port resonance is far more pronounced and isn't detectable. These sound fantastic.

[nyt]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

Two down, two more to go.

[Adam_G]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

Two down, two more to go.

....... Holy $#!t.....

[winslow]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

Kryptonite White passed a way? I wondered what happened to that guy...always had some far fetched car audio ideas.

[mattk]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

Two down, two more to go.

Did you use a forklift to place the upper one?

[nyt]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

Did you use a forklift to place the upper one?

Myself and 3 friends lifted it then slid it in place.

[winslow]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

This thread is so full of win it isn't funny. Love that HT setup...but I am from car audio and love bass.

[badman]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

The quarterwave I'm concerned with is excitation energy for the vent, but let's move past my concerns- which I'm sure don't matter much when your brain is melting

How are you using that 3722 PT horn? I keep meaning to snag a pair, then flaking since I have so many projects.

[nyt]

Re: (4) 2x 18" LMS Ultra 5400 in 15hz 27cube slot ported enclosure

The quarterwave I'm concerned with is excitation energy for the vent, but let's move past my concerns- which I'm sure don't matter much when your brain is melting

How are you using that 3722 PT horn? I keep meaning to snag a pair, then flaking since I have so many projects.

4722N (JBL network and not biamped) as L and R powered right off a denon 5308 w/ the upgrade. Amazing, to say the least. Running a 3677 in the center due to height limits. New they can be had for $1100 and $500 respectively.

I try to keep the amount of electronics in the signal chain and digital/analog conversions to a minimum. My source feeds the receiver via hdmi then direct to speakers. Incredibly sensitive speakers. MultEQ XT calibrates them down to -11db a full 13 feet away from the listening position.