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90Euro

2nd subwoofer crossover point

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90Euro

Always looking for something to do on the boat....

I already have a hull firing RF hx2 12" in a ported 1.8 cuft box. tuned to 33hz. Sounds good and loud but is very peaky because the box is on the small side, which is all I can fit at the drivers feet. I want to add a 2nd sub in a bow filler enclosure down fired. I want to have a flat response from the new sub. I plan to have the bow sub balanced with the entire system and have my ported 12" on a bass knob for separate adjustment. I am going to use an old alpine type r 12" swd 1221d for now in a 1.3 cuft sealed. I am wondering the best way to set the crossovers for the subs. Should the frequency overlap or not?

Edited by 90Euro

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Earmark Marine

My honest opinion is that doesn't make a great deal of sense. You are wanting to create acoustic soup. Mix it all up and hope for the best by averaging. Here are some fundamentals.

Two subs in separate locations with different boundaries and different distances from the perception point will have different phasing.

A sealed sub has a different phase rotation than a ported sub which has a different phase rotation than a bandpass sub.

Crossovers go through a phase rotation.

Any non-linear change in amplitude is accompanied by a phase rotation, such as EQ and filter slopes. The inverse is also true. The two can't be separated.

You don't necessarily care about the phase response of two speakers playing different regions but you really do care about the overlap where two speakers are playing the same material.

In order for a sub to sound musical you are highly dependent on the upper harmonic contribution from the coaxial midbass drivers. If the sub overdrives the midbass of the coaxials the sub will sound indiscriminant. Also look closely at how your coaxials are loaded and positioned.

If the sub isn't well matched to the coaxials in phase, in amplitude or due to poor crossover selections, the resulting gaps and peaks will create a peaky sounding response.

Adding more complexity could possibly average out the response but will certainly make it muddy.

My suggestion is to fix what you already have with a single subwoofer. Re-build the enclosure with a longer port or tune the enclosure a bit higher, etc. Make sure the surrounding boundaries are not too close to the woofer or port and changing the intended bass-reflex alignment. In any case, create a more linear sub. Select a different crossover point. Re-set the gains. Experiment with the polarity. Add a really good trunk mount EQ. Use test CDs. Use an RTA. Measure things. What measures correct usually sounds good and good tools can quickly replace days of trial and error.

David

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90Euro

Thanks, I will check what you mentioned. How important is it to use a double baffle board and internal bracing? I used neither on my 3/4" mdf, 24"x20"x12.5" ported enclosure. Is polyfill something I should consider too?

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Deephaven

Depends on the box and the sub. In general I always do it, but at the same time if fidelity isn't your ultimate goal you can make compromises.

As for the polyfill, generically I wouldn't recommend it for a ported box.

I couldn't agree more that fixing what you have is a way better option.

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Earmark Marine

Polyfill? Not at all necessary but maximum one layer of 1-inch polyester batting on the interior surfaces for bass-reflex. Never anything loose.

1-inch baffle. Only needed with exceptionally heavy and exceptionally deep woofers so you can use longer screws (or build a rear supporting cradle).

Internal bracing? Reduces and raises cabinet resonance. That's a good thing. Don't over do it. Two .75" X 1.5" with radiused edges is sufficient. Offset the enclosure size accordingly. Not necessary on small .75" enclosures but important on very large enclosures.

Baffles and bracing? It's important that the front baffle is the outer dimensions rather than the inner dimensions.

Btw, no reason the port has to be folded inside the cabinet versus outside the cabinet.

David

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CRF-Rider

I've installed 2 different subs on a boat. It's not easy to get right. The time alignment is incredibly difficult to overcome. It took a lot of modeling in winisd and trial and error before I was happy with it, I don't think it's worth the effort. Double check your filters (lpf and subsonic)

Like others said, I wouldn't put polyfill in your ported box.

A double baffle is the single best thing you can do for the strength of your box, regardless of size. It's easy to do, and if you flush mount the sub it doesn't add to your external dimensions.

If you have a slot port (L port) with a double baffle, bracing won't be needed. The L port acts as an internal brace. If you use a round port, like a precision port you'll probably want to add some braces. There is absolutely no point in radiusing brace edges (aka roundover edges), it will have no effect...if it did you'd see guys trying to put roundover edges on the voice coils of their subs. Roundover edges do help on port edges to reduce turbulance, aka port noise. A simple option for a brace is 2" oak dowel rod. Also, epoxy resin will add strength and marine proof it. Using a hardwood, and not MDF will help as well. All of these techniques help make your box more efficient. Just becareful about adding bracing to a box already built, you'll raise the tuning frequency.

The dimensions you mentioned is 2.5^ft net, I just built a ported box for a guy last week (pic below) with the same internal space (net). It worked out well. One thing I've noticed with most boxes on other boats, the focus is geared toward aesthetics, not performance.

SU1BRzA0MjcuanBn.jpg

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nuttyskier2002

I have a question similar to 90euro's above. I've been working on my sound system for my 06 Vride for almost a year now. Here's what I have so far....

1 pare of Polk MM691s - mounted vertically in the wall right under my rear seat firing forward

1 pare of Polk MM651s - in the stock dash location

1 JL 12W3v3 mounted in a ~1.9 ported box under the helm firing into the hull - followed specs supplied by Earmark

1 pare of Rev10s mounted on my Illusion X tower.

The MMs are powered by a 4 channel RF 450.4 Punch amp

The sub is powered by a JL 500/1

And the Rev10s are powered by a Polk 4000.4 bridged to 2 channels.

My head unit is a Pioneer DEH 80PRS. This system sounds very nice and clear and will get very loud. But it just doesn't seem to produce the bass I and after. I mostly listem to Classic Rock, some Country and Pop. Not too much into Hip Hop or Rap.

My friend's boat has way less (in terms of money) put into his sound system than mine. He has two 10" sealed subs (one mounted in each of his rear lockers. The bass that his system has is night and day difference than mine. I've been trying to get my system to sound more like his for some time. I don't want to put subs in my rear lockers.

If I build a ~2ft cubed sealed box a mount two 12's at 90 deg angles to each other........have one firing into the cabin space and the other firing into the hull........will I run into phase relation problems with my bass? Has anyone tried this (mounted under the helm). What do you think it would sound like?

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nyryan2001

Nutty- in my last boat, I ran 2 high end sealed 10" Orion HCAs on a ton of power.... Tucked away back in compartments.

After listening and learning from all the experts on here.... Most recommend 1 sub, well done, quality build, vented and firing into the cockpit.

I followed suit, and am glad I did. I went big on my setup, 1 massive 15" on 2500 RMS. But in comparison to the previous 2 10's sealed in compartments it's insane. I would estimate It would take 8-10 of those HCAs to match my current setup, music quality and bass output. Not even in the same ballpark.

So I am now a firm beliver, 1 big sub done right, vented and firing into the cockpit is the way to go. Lots of issues with dual sub setups.

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Earmark Marine

Nutty,

You're talking about a scenario similar to running one sub facing into the vehicle cargo area and one sub aimed forward at the occupants. Yes, you will have phasing issues. You will get an output gain but not have great tonal construction. Plus, most 12s require a little more than 1 cu.ft. net displacement. More woofer surface area matters. Larger woofers usually (but not always) have a lower resonance and deeper reach. One location is always better. If you go with more woofer you will need more amplifier.

But before making wholesale changes I would measure and re-check what you have now. Because there is a very good chance that you have overlooked something. The descriptions and comparisons you have given don't sound right to me.

What model of 500/1 amplifier do you have? There are several.

Which impedance of 12-inch sub are you running?

What DC voltage are you getting at the amplifier primary power terminals when the sub amp is at the threshold of clipping?

What AC voltage are you running at the amplifier speaker terminals when the sub amp is at the threshold of clipping at various frequencies?

What AC voltage are you getting at the RCA inputs of the sub amp at the threshold of clipping?

What is the lowpass and highpass crossover frequencies?

Have you done a phase check between the subwoofer and coaxials?

It's also worth double checking your enclosure math.

When you have an under-performing product combination you can speculate forever and waste time and money but measurements can be extremely revealing and easily/quickly uncover a problem or two or three that otherwise are masked. Measurements are the most objective analysis you can have.

You also have some of the best dealer resources in the country in Phoenix. Oftentimes a veteran can listen to a system and immediately identify problems.

David

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Earmark Marine

Nutty,

Your enclosure should be 2.97 cu.ft. external displacement, and 1.75 cu.ft. internal NET displacement 'after' the port volume, port wall and driver displacement is subtracted. Double check those numbers.

David

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nuttyskier2002

David,

Sorry it took so long to respond. Thanks for the advice concerning phasing and measurements to be made. This is what I have checked: The RMS voltage to my subwoofer driver is 45 vrms (digital multimeter set to AC). This was measured while playing a 60Hz test soundtrack at 3/4 volume from my head unit with the speaker disconnected. The speaker (JL 12w3v3) has a 4 ohm input impedence - single voice coil (verified with my multimeter). My amp is an older (discontinued) JL 500/1 Monoblock. So I'm guessing it's the first of the slash series amps (there are no revision characters after the 500/1). My cross-over freqs are set in my head unit at 80 (high pass for coax) and 80 (low pass for the sub). Phasing is default...it has not been changed. Also no time correction routine has been completed either. The Bass EQ switch on the amp is set to "off". The Infrasonic filter is set to ~ 35Hz. The Center Freq is set to ~ 60. I have not made any other AC measurements with any other soundtracks except 60Hz. I have not verified my DC power voltage at the amp but I will say my power leads are 4 AWG cable and are only ~ 4 ft in length. The battery is an Optima D31M which is kept charged by a Guest 2611 Pro Charger while the boat is parked and a 200 amp 12SI Delco dedicated alternator while running. And the battery stays charged. I know this because I have a digital DC voltage indicator connected to it at all times.

Now for the enclosure. I got the plan for the enclosure from Odin Mattes at Earmark. He sent an e-mail with an attachment of this plan after I ordered my JL 12w3v3 driver from you during last years Black Friday sale. The plan specs for a box with a total of 1.926 cu ft and a port length of 27". It gave exact dimensions of every side and included the dimensions of the pieces used to form the slot port. Included in the plan was a note that stated for best results a volume of 2.213 cu ft is needed. But due to my space limitations the 1.926 will suffice. I still have this e-mail and can forward it back to you for your review. Also I spoke with Victor who informed me that the port of the box is tuned to ~ 33Hz thus my Infrasonic filter (high pass) is set to ~35Hz.

Here's another question.....would this sub sound better if it were firing directly into the cabin area instead of side firing into the hull? If so....I could build a box closer to optimum size.

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Earmark Marine

Nutty,

First, I want to see your enclosure plans. Some of those specs sound foriegn to me. Woofers and enclosures can be similar in that you can design either for maximum linearity over a wider bandwidth or maximum output over a narrower bandwidth. But you can't do both to the extreme in the same product. It's very much like the trade-offs you make with a vehicle's differential or a boat's prop. And perhaps the enclosure design is correct for one application but doesn't fit your particualr objectives. Alot of that is optional in a bass-reflex design.

Next, your system is tuned as if it's an enclosed cabin of an automobile rather than an open environment of a boat. There are a number of other system set-up issues to discuss and this will get protracted.

I'm pretty confident you don't need to add to your equipment or the complexity of your system to see better results.

David

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nuttyskier2002

David,

I am forwarding you the email that was sent to me with the sub woofer specs attached. Please check your email. Thanks!

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nuttyskier2002

David, I didn't have your direct email address so i sent the spec to Odin in your sales dept.

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nuttyskier2002

David, did you get the email with the sub enclosure spec?

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Earmark Marine

Nutty,

Yes, I got it and sent you a book via email of my ideas.

David

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