Car amplifier for specific speakers (Bose SE 151)

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Car amplifier for specific speakers (Bose SE 151)

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I am trying to sort out a possible configuration for a sailboat, and am getting confused.  Any advice would greatly be appreciated.

I am looking for a system to go on a sailboat, 2 speakers in the cockpit, 2 speakers down below in the galley.  Because this will be on a sailboat, often used with no engine running drawing straight from the battery, I have to be mindful of energy consumption.  I will have 2 group 27 batteries in the house, each battery at 12V, approximately 100 amp hours each.

A marine company named Navipod sells the nicest cockpit speaker mounts I've seen yet, mounting the speaker underside each of two stern perch seats (seats on the railing at the back of the boat).  I like these speaker mounts because they position the speakers well, out of the way, with minimum drilling/cutting into the fiberglass, and allow wires to be routed easily through the stern railing .  You can see a picture of these mounts at https://newcontent.westmarine.com/content/images/catalog/full/9521378_3_FUL.jpg

Unfortunately, these mounts only work with speakers Bose 151 SE, which I believe are 8ohm speakers.  From the manual (https://www.bose.com/en_us/products/speakers/stereo_speakers/151-se-environmental-speakers.html): "Compatible with amplifiers or receivers rated 10 to 100 watts per channel at 4 to 8 ohms; 50W IEC continuous power handling at 6 ohms".

I figured it was best to use the same speakers in the cockpit as down below in the galley, but am open to different speakers in the galley, if it helps better find an amp.

Since these speakers appear to be 8ohm, and car amps are usually rated for 4ohm, I am getting very confused trying to find a decent 4 channel car amp that would produce enough RMS power for these speakers, that would also not drain the batteries on usage.

I've thought about hooking up 2 speakers each in parallel, thus bringing the ohm down to 4, but if I understand correct that would prevent me from using the head fade to only play speakers in the cockpit vs only play speakers down below in the galley.

These speakers appear to have good reviews for outdoor quality, and I really like the cockpit mount.

My head will have 4 channel pre-outs.

Will these speakers work on a car amp? If so, since they are 8ohm speakers, what RMS watts per channel should I be looking for in an amp?  Any amp suggestions that won't drain the battery?  Or is this just a bad idea and should I be looking at a different set of speakers?

Thanks for any help and/or advice.

All Replies
  • The amp and speakers and headunit need to all be marine certified.

    GLH Geeked

  • What sort of budget have you?

    Crutchfield lists them as 8 ohm, but the "50W IEC continuous power handling at 6 ohms" suggests they are 6 ohm to me.

    Yeah, they are, ""Compatible with amplifiers or receivers rated 10 to 100 watts per channel at 4 to 8 ohms". Sure, that's probably easier to say than 50RMS 6 ohm when no one lists car or marine amplifier power at such an impedance.

    An amplifier rated for say 100RMS@4 ohms, would present less power to a 6 ohm load. An amplifier rated for 100RMS@8 ohms would present more than 100RMS to a 6 ohm load. However, the impedance of the driver will be changing continuously as it plays music and will rarely drop down to 6 ohms.

    With your situation, you'll likely be wanting to go with a more efficient class D amplifier.

    It kind of depends on just how loud you like to crank your music as to how much power you'll need/want. Obviously, the more power you have on tap the better (for performance), but the quicker it'll drain your batteries.

    I am NOT familiar with boats, but I thought they have a battery solely for the engine as well, which when running will charge the other reserve batteries. Again, don't know boats or proper terminology.

    There's no sensitivity rating listed for them, so I don't know how efficient the speakers are, however, I'd like to believe that even 20RMS would get them playing fairly loud.

    I'd probably opt for a 50-75RMS@4 ohm amplifier, that should be capable of roughly 37.5-50RMS@6 ohms.

    While a marine amplifier wouldn't be required, they are designed to handle such an environment much better and would be a wise route.

  • OIC, those speakers are marine rated for boats.

    GLH Geeked

  • @GLH: why would the head and the amp need to be marine rated?  I understand that might be optimal, but both the head and amp will be down below in galley where it should be dry.  One pair of speakers will be in the cockpit, completely exposed to elements, but theses Bose 151 SE are their outdoor model.

    @Weigel21: My budget is reasonable.  Ideally, I'd like to keep the amp under $400, if possible.  But if I have to go over, I can.  I contacted Bose direct, and they claim these speakers are 8ohm, but the wording in the manual on the specs leaves me pondering their ohm rating.  Crutchfield sales rep says they are 8ohm.  Boat battery wiring can get confusing very quick.  But basically I would have a dedicated starting battery and a dedicated "house" battery (everything else), with a switch for either battery or both.  One thing I failed to mention is I will have a solar panel rated 150W, pumping some charge back into the batteries during day.  And I was already homing in on class D amps for their efficiency.  Speakers don't need to be banging loud, as they don't need to drown out an engine.  Moderate volume is the goal.  So you think a  50-75RMS@4 ohm amplifier would be decent to drive these speakers?  And basically, these speakers would be ok?  Again, my attraction to them is no fiberglass has to be cut into for mounting in the cockpit.

    Thanks to all for the advice.

  • Quite odd that they'd even list, "; 50W IEC continuous power handling at 6 ohms". If they are not 6 ohm, but 8 ohm, they'll never present a 6 ohm load, so why even list a 50W power handling @6 ohm.

    Whatever, it's Bose logic I guess. Never been a fan of theirs anyway.

    If they are in fact rated to handle 100RMS and present an 8 ohm load, then to be capable of feeding them 100RMS, you'd be looking for an amplifier capable of 200RMS@4 ohms, as power output would be nearly cut in half when presented an 8 ohm load.

    A 200RMSx4@4 ohm amplifier sure won't be cheap, but at the same time, it's unlikely you really need to be capable of feeding them rated power.

    A Rockford Fosgate M400-4D could be had for under $300 and is rated for 75RMSx4@4 ohm. That'd amount to around 40RMS to the speakers. I mention this amplifier as it's sure to be under rated (capable of more than 75RMSx4@4 ohms and looks to be more efficient than many of the others under $400 since it only calls for a 40AMP fuse when others have a higher total fuse rating.

    And if you buy it from Crutchfield, you have 60-days to find out if it's enough for you or not.

  • My experience with boats (quite a lot) includes the fact that when the boat is on the water all night and day, the moisture level is high inside and out. If it is on saltwater, there will be salt fog getting to everything. The galley is not airtight.

    GLH Geeked

  • @Weigel: again, many thanks for advice.  I will take a look at this Rockford Fostgate.  If I understand you correct, the Bose 151 SE could be matched to a 4 ohm amp, but if they are rated at 8 ohm, pairing with a 4 ohm amp effectively cuts the watt output in half from the amp to the speak, correct?

    @GLH: I failed to mention this boat will be freshwater only (Lake Michigan), and won't be in as corrosive of an environment as saltwater.  Although, with the price of some of the amps I'm considering, I am now leaning towards marine rated amps due to moisture levels down below in the cabin.  I am not as concerned about having a marine rated head, as the heads I'm looking at are very affordable.  And I've had boating friends on Lake Michigan use non marine rated heads in their cabin for years of use with no troubles.  Thanks for your input too.

  • Yes, in theory, power output would be cut in half when running at 8 ohms, though in reality, it's not quite so.

    Also, the Rockford amp I listed is marine certified.