DavidEM

Skibumm, My only recommendation on the enclosure is that HDPE is difficult to bond and seal. Make your life considerably easier by limiting HDPE to the bottom pad. Try to keep it simple. David

Skibumm, With all that space I think your sub enclosure plan is a walk in the park. You can always build a facade to cover the enclosure and all mounting. The 1/2" thick polymer (ABS, HDPE, other non-wood-based composites) mounting pads would hardly show in any case. You have the right idea about building shallow enclosures in the gunnel cavities to house a 6.5" speaker. A little baltic birch, polyester resin, and marine carpet plus an insulating polymer base if resting on the sole, will get the job done. Now all the 6.5" coaxails are essentially infinite baffle. So they will sound much better if the net internal displacement of the pods are or approach 1.0 cu.ft. It may not be possible but that's your target. David

skibumm, A picture is worth a thousand words. I must admit I had a different vision. Bass-reflex (ported) gives you deeper bass extension plus greater output over a sealed enclosure. Think of it this way. A woofer one size down in a bass-reflex enclosure will slightly edge out a woofer one size up in a sealed enclosure. But the enclosure could be as much as 75% larger than the sealed version for the same woofer. It appears you have the cavity size to do anything you want. However, the limited insertion height would practically eliminate the use of a 15" or 13.5" woofer. Let's do this step by step to narrow it down... Cut the 34" depth to 24". You won't need all that depth. Maintain the 22" width. Cut the 14" insertion height to 13.5" to allow the enclosure to sit up on polymer mounting pads to allow for drainage and evaporation. Besides, you don't want to create a mold and mildew trap by setting a large enclosure footprint on top of carpet. The above would yield an enclosure of over 4 cu.ft. external displacement. Most 12-inch bass-reflex woofers will require an enclosure with an external displacement of 3 cu.ft. or less. That's a really big woofer in a really big box and you are not coming close to the available space. I would say you have little to no restrictions. Moving forward. Now if you are not a total basshead then there is not much point in the woofer over-driving and dominating the ability of the in-boat coaxials, although some extra reserve capacity keeps the woofer sounding tight. If the coaxials can't keep pace, then the bass tends to sound inarticulate and boomy. So for a total of four 6.5" cockpit coaxials mounted in a well-isolated manner, a sealed 12" or bass-reflex 10" would easily be in balance. Once the boat determines the woofer/speakers, the woofer/speakers dictate the amplifier power. Balance is important in allocating your budget. Investing too much in one component to the detriment of another component is counter productive. Again, balance results in the best performance. David

Yes, but you could tap the deep bass.

Well, you might get the REV10s to play lower if you had them in 10 gallon pods. How would that look? David

Skibumm, That is useful information. So the picture is becoming clearer. If the bulkhead underdash pretty much seals off the bow cavity then disregard my previous recommendations. The bulkhead should be sealed off the rest of the way, if possible, and the subwoofer should be on the cockpit side of bulkhead and right up against the bulkhead. Many contemporary sealed 10-inch subs only require (1)cu.ft. external displacement with 0.75" thick construction. So any three dimensions that arrive at 1728 cu.in. David

Skibumm, A closed bow is unique because of the giant under-bow cavity displacement. If you place the sub at your feet and aimed toward you, then the reflected radiation from the bow cavity will lack coherency with the woofer's direct radiation. It's not much of a concern with a small cavity like a split helm console of an open bow. There are two possible techniques to follow. One is to place the sub/enclosure far up into the nose of the bow with the driver pointed toward the transom. The other is too place the sub/enclosure at the dimising bulkhead with the driver aimed at the nose of the bow. In either case the woofer will be vertical. Don't get fancy with down-firing. The wildcard here, and what we can't see without good photos, is the bulkhead. If it is low and more of a kick panel or footrest then it's not an issue and changes nothing in the above directions. You asked, "would that mute the bass?" Not really the way low bass propogates and dissipates. The low bass would be muted by a solid obstruction which wouldn't appear to be the case here. The bow cavity is going to behave like a resonant chamber. We are trying to ensure that the woofer's direct radiation is coming from 'within' that chamber rather than on the perimeter of that chamber. This way we have ONE uniform phase response coming from the closed bow. The difference in the upper bass articualtion will be profound. Of course, you can experiment before commiting to a particular mounting location and orientation. David

Skibumm, One recommendation for the subwoofer/enclosure location. Place the sub far forward in the closed bow cavity. Or, at least orient the sub driver so that it is firing toward the forward bow. That's an awfully big cavity up there. Either of the two techniques will ensure that the direct woofer radiation and the reflected radiation from the bow cavity are uniform. David

Sorry, I meant to type "....seat closed, just cracked open and fully open."

Rhuntlll, The 'sole' is the subfloor and the 'coaming' is the interior return of the gunnel. These surfaces make up the cockpit bath tub so to speak. You will have much more acoustic leverage venting from the bottom of the bath tub than from the upper rim. The bigger the vent, the more output you will have and the more upper end bass transients and pitch accuracy you will have. With no vents or a couple of tiny vents you will have indiscriminant boat shaking but little to no musical bass making. The other thing to keep in mind is that specialized flat/shallow woofers (from any manufacturer) will be a little heavier, have less excursion/travel ability, and will be less sensitive. Things you wouldn't be as inclined to notice behind the seats in a tiny pickup interior with an enclosed cabin. In an enclosed locker, the woofer will have to travel four times as far and the amplifier will have to produce four times the power, at minimum, to equal the output of the same direct-radiating woofer. The best sounding woofer will ALWAYS be the one that operates the most conservatively to produce the same output. The asthetic challenge is that you don't want to turn your boat into swiss cheese. Please do this before commiting to cutting holes. Listen to the sub out on the water when underway with the observers seat open, just cracked open and fully open. Form your own perspective under real world use. Then make your decisions. David

Rhuntlll, "I'm thinking the sound leave the port hit the windshield and the windshield will create an amphitheater effect." Very true, but short lived. You are much better off venting the sub output from lower in the boat in order to benefit from the considerable boundary loading of the sole and coaming. Also, consider this...the port locker and adjoining gunnel cavity represents a very large and therefor very compliant air mass. With a couple of small vents there is little impetus for the bass radiation to exit the compartment. The larger the vent surace area, the less resistance, and the greater the ouput. David

Sure, that has the advantage of delaying a decision on a subwoofer. And if you added a moderate (keeping Mom happy) subwoofer at some point in the future then you could address the in-boat amplifier with the right model. David

Paycheck, The Syn6 is more of a beast despite the 14.4 volt ratings. It is regulated (on the supply side only) so it maintains power levels with a lower voltage supply. But as a Class AB amplifier, you will not enjoy the Class D efficiency of the HT-6. If budget permits, consider breaking the HT-6 into an HT-4 + HT-2. David

Paycheck, Of all the speaker choices you mentioned, one pair of Rev10s is the most cost/performance-efficient. Why? Because you are investing in a speaker with more pod displacement and more surface area. That means more output and deeper midbass extension. This would be in contrast to two pair of smaller speakers where much of your investment is going into redundant hardware such as pods and clamps that do not translate into audible performance. The initial thought would be to run a pair of tower speakers and two pair of in-boat speakers off a six-channel amplifier bridged into four channels = four channels bridged into two on the tower and two channels driving two pair of in-boat speakers in parallel. That would be the equivalent of a 2-ohm load on all six channels which is a serious load on any multi-channel amplifier's power supply, especially when running the system hard. And you wouldn't be getting Rev10s to run them easy. So this is where I would splurge a bit and break the six channels down into two compact amplifiers like an HT-4 bridged on the tower and an HT-2 on the four in-boats. Same collective six channels but a little more supply and a little more heatsink mass. I think this would make a difference. David

Dr, Class B has an inherent flaw. The separate positive and negative transistors do not match up and create distortion through the transition (simple version). Okay for a portable radio headphone amplifier but not okay for big power. Class AB places a bandaid on the problem by applying a constant voltage to both transistors. Now they are operating in their linear range and this cures the distortion. The opposing bias voltage cancels but in the process you waste considerable power and create a lot of heat. So a Class AB operates at a typical efficiency of 50%. It sounds good. Half of all the incoming wattage is wasted. Class H is essentially a Class AB output section. However, the power supply side now tracks the audio signal with great precision and responds by altering the supply voltage. The amplifier is wasting far less energy when absolute full power is not needed. Given the transient nature of music this is a very effective conservation scheme. You net a 40% efficiency increase over Class AB. Class D is an analog switching amplifier (not digital in any sense). It has a constant switching speed at an ultra high frequency that is modulated by the audio signal. The clock, so to speak, is filtered out well above the audio bandwidth to create a pure duplicate of the original audio signal. The result is 60% more efficiency than Class AB. David