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BaBaLoO

2Nd Sub Placement.

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BaBaLoO

I have 2 12"rfs, one under the helm and one in the ski locker in a ported box. Was thinking of putting the one in the ski locker behind the rear bench. Has anyone done this and would I expect a decrease in sound quality? I dont care about when we are moving but when we are floating. Im thinking of putting it in a smaller ported box angled in the front a little bit to fit right behind the seat. I know it will be muffled and not an ideal space just would like to know if there will be any difference good or bad. Thanks

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Earmark Marine

Okay, seat cushions are thick and dense. Fiberglass structures are thick and much denser. So, you are going to have serious losses in bass output in any case until you open a hatch. The boat will still shake and vibrate as much of that radiation will still transmit through. But you are left with more of a tactile bass rather than an audible and musical bass. When you open a hatch you minimize the loss. I could go into the problems with efficiency and phase coherency issues with mutliple sub locations that are loaded very differently, but, I won't unless requested. I understand what you are after and here may be a solution for you. IF, and its a big 'if', you can build a bandpass enclosure that has the port totally exterior to the enclosure you can place the sub enclsoure into the rear storage locker next to the engine and run the port mouth under the rear bench so that it vents directly into the cockpit. This would give you 6 dB more output than a sealed enclosure, equivalent to four times the amplifier power, and escape all the losses from being concealed.

David

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nyryan2001

David, so what you are saying, is a well built vented enclosure where the speaker and the box vent directly into the cockpit, will be equal to 2-3 sealed subs powered the same, but hidden behind fiberglass, seat cushioons and compartments.

That direct access into the cockpit is that important compared to adding another sealed or hidden behind compartments sub. So most all of your reccomendations would mostly be aimed at improving the underdash enclosure and sub setup? most bang for your buck there?

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Earmark Marine

Ryan,

Your questions are very much different from the OP's so let me make that distinction. He is already committed to a certain path for listening at rest. A bandpass is a unique solution because ALL the sub radiation can be funneled directly into the cabin through a small opeining. Its a challenge from a direct shot standpoint and from the port length standpoint but its a possibilty that has worked well in other boats with similar challenges.

So Ryan, if we are looking at general system design from the beginning then I would have to say you would focus on the most optimum and unobstructed single subwoofer location. And in most towboats that would be under the driver's helm console. There can always be an exception when someone is trying to accomplish something a little different. But this will be the most efficient location with the least acoustic problems. As for losses, just imagine how effective the rear engine compartment hatch and rear bulkhead is in attenuating engine noise. I would say its actually much more effective than 5 or 6 dB. The losses created by concealing a sub in a sealed ski locker are not going to be linear (meaning all frequencies will not be impacted equally). You'll still get the shake, vibration and indiscriminant rumble surviving but most of the upper bass that contributes to the tonal qualities, transients and attack will be severely filtered. That brings into play another issue. If you listen to a subwoofer by itself with all coaxials off you will find that all subwoofers sound soggy and muddy without the contribution from the fullrange coaxials. Its the midbass contribution from the coaxials in combination that provide much of the final pitch accuracy and bass definition. So when you place a subwoofer behind a sealed compartment you are creating a hole in the response between the sub and coaxials that is hard to bridge and its just lacks musical coherency. So unless you are trying to do something totally over the top and/or are just looking for pure bump (nothin' wrong with that if thats the goal) don't place your subwoofer in a sealed trunk. You may be able to hear the bass a block way but the bass coming from that sedan sounds awful just outside of the closed trunk. Its an analogy that most of us have already been witness to.

David

Earmark Marine

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BaBaLoO

David,

Yea I see what your saying that was a concern for the rear trunk of the boat. I was thinking of doing a long port but having it in that location leaves a big chance of water running up it if I dip the nose of the boat. Ideally I wanted to have it under the passenger seat with a port facing the back but it seems to complicated and expensive to do so. Looking for anything I can do to maximize sound quality without breaking the bank which I know in some cases cant be done. Would like to seal and port the sub under the help aswell without spending too much on a box. Will i notice that huge of a difference. I would want to be blown away if I where to do it.

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Earmark Marine

BaBaLoO,

Its hard getting into any more of a concise discussion until I see exactly what you have in mind so send some photos of what, where and how.

David

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Murphy8166

Is there not an option to put two under the dash?

double.jpg

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BaBaLoO

Is there not an option to put two under the dash?

double.jpg

are those 10s or 12s??

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Bobby Light

You can fit two 12" subs under the dash of the 23, just have to get creative and think "outside" the box.

Edited by Bobby Light

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BaBaLoO

You can fit two 12" subs under the dash of the 23, just have to get creative and think "outside" the box.

Do you have a heater as well?

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Iron gator

I also had dual 12's in a sealed box under the helm, mine were forward firing and hidden behind the wall. They sounded great.

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Bobby Light

Do you have a heater as well?

Yes I have a 3 outlet.

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CRASH

Yes I have a 3 outlet.

Who needs a Heater? Oh never mind your Summers still require a sweatshirt :rofl:

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BaBaLoO

So deciding to try to build a box that will have both subs under the dash but dont want to give as much leg room up as the picture shown. Is this possible with 12s and a heater? Was thinking of doing a normal box (still unsure if I should port or not) but having the lower part of it elongated to get the cubic feet that I need. Has anyone done this? any comments or concerns I should be considering?

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Bobby Light

There will be nothing normal about the box when you're all done, there will be many angles and possibly compound angles to make it work with a heater and two 12" woofers. Porting it isn't impossible but takes the difficulty up a few notches. Build whatever you want out of cardboard or 1/8" birch first to see if it will fit in the space. Have to be able to get it in the space, that's one thing people don't think about. What I mean is usually there isn't as much space as people think due to the opening to get the box in. Just because a space has the room doesn't mean you'll be able to get the box in that space. Your box can be almost any shape you want to make it work, within reason.

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BaBaLoO

There will be nothing normal about the box when you're all done, there will be many angles and possibly compound angles to make it work with a heater and two 12" woofers. Porting it isn't impossible but takes the difficulty up a few notches. Build whatever you want out of cardboard or 1/8" birch first to see if it will fit in the space. Have to be able to get it in the space, that's one thing people don't think about. What I mean is usually there isn't as much space as people think due to the opening to get the box in. Just because a space has the room doesn't mean you'll be able to get the box in that space. Your box can be almost any shape you want to make it work, within reason.

Yea I was going to make a paper template first to see what shape I would need to do and how much cubic feet I would have to get what I want to accomplish. In your opionion and I know everyone is different would you go with a ported or sealed box regarless of difficulty.

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Bobby Light

For me I like ported better as long as its done right and you have a good mono sub amp with proper crossover adjustments. A good ported box sounds every bit as good as a sealed but has all the additional benefits of the ported design. If you can get well over 4 cu ft from under there you should be able to do it but you'll have to get creative with box design to take advantage of all the useable space under there. Should be a fun project.

Edited by Bobby Light

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BaBaLoO

For me I like ported better as long as its done right and you have a good mono sub amp with proper crossover adjustments. A good ported box sounds every bit as good as a sealed but has all the additional benefits of the ported design. If you can get well over 4 cu ft from under there you should be able to do it but you'll have to get creative with box design to take advantage of all the useable space under there. Should be a fun project.

I was reading that I would need around 3.5-4 cu ft for a ported box, you think I would need over 4??

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Bobby Light

Figure about 2.0 cu ft for each 12 plus sub and port displacement. That puts you way over 4.0 cu ft, much closer to 5. There are some June that are designed to do better in smaller ported boxes. Maybe that's the way you should go?

Edited by Bobby Light

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BaBaLoO

Figure about 2.0 cu ft for each 12 plus sub and port displacement. That puts you way over 4.0 cu ft, much closer to 5. There are some June that are designed to do better in smaller ported boxes. Maybe that's the way you should go?

june?

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Bobby Light

Sorry phone auto correct, meant subs.

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Earmark Marine

BaBaloO,

This can get a little confusing because oftentimes the displacement that is provided for a bass-reflex enclosure excludes the port volume and port wall volume. So for the purpose of the design I always find the true internal displacement 'with' the port and then convert that to an external displacement. Initially I am most concerned with the total external displacement because that is what I am going to have to fit into the boat. And it can get complex to calculate with odd shapes, angles and even compound angles so I want to simplfy the process as much as possible with an external set of dimensions. Also, as mentioned above, what will fit the caviity and what will fit through the access and get into position may be two very different things. Generally you have to angle an enclosure into place which expands its insertion dimensions.

Don't get too caught up in the woofer(s) maximum surface area alone at the exclusion of the optimum enclosure. Surface area will determine the peak output that is available above the frequency region where the box has a major impact. But past a certain point it will be the enclosure size and type that will have the most affect on lower bass extension and lower bass output. Your personal priorities and expectations as to what type of bass you want should shape your decisions.

A fairly compact 12-inch bass-reflex enclosure will have an external displacement of 2.75 cu.ft. per each with a woofer that has a low Qts and a lower resonance. Another woofer of the same size may require a much larger enclosure. A fairly compact enclosure for the right small box woofer might be 1.85 cu.ft. external displacement while another driver might require more. So at minimum consider 5.5 cu.ft. external for dual 12s in a bass-reflex and 3.70 cu.ft. external for dual 12s in a sealed enclosure.

A bass-reflex enclosure will not give you an increase in output above 100 Hz as compared to sealed which is not an area of concern. However, with bass-reflex versus sealed you can expect a solid 3 dB of extra output through the bottom octave of bass and you can expect another 8 to 10 Hz of deep bass extension before you reach the half power point. So to put this in perspective you can get more output gain and extension by going from sealed to bass-reflex than you can by stepping up to the next size of woofer in most cases. This is why I like to start with the maximum enclosure that will fit the boat and then select a combination of woofer and enclosure that will best perform in that available size. Forcing a larger woofer(s) into an undersized enclosure is counter-productive.

David

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shawndoggy

Do you have a heater as well?

Man, if you are going to all this trouble to get two subs in the boat, have you considered moving the heater? There are definitely alternative places to put the heater core.

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BaBaLoO

Man, if you are going to all this trouble to get two subs in the boat, have you considered moving the heater? There are definitely alternative places to put the heater core.

Thing is I already have 2 subs in the boat one under the helm and the other in the storage locker (ported car box from original owner) I want to be able to use the second sub more efficiently, my first idea was to put under the passenger seat and have a port facing the rear of the boat but apparently it isnt that good of an idea and im all out of them. who would thought having a second sub would be a headache!

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Earmark Marine

Even if you have to make a moderate compromise in the ultimate enclosure you are going to be way ahead not having a sub in the port side locker.

David

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