Marine subwoofers (JL M10) ported versus sealed

[highfigh]

"Interesting. I'm not really super concerned about sound quality because I know what we define as good just isn't possible in that environment, I just want it to be an improvement, also by building a box I can use the box to hold up the seat...so it would kind of provide double duty."

Even more reason to not try to go that deep. Remember- the bass frequencies make the amp work harder than the rest, so if you have a speaker that can't reproduce them, filter them out. Power that can be used for nice, punchy bass and mid-bass is a better investment. I don't know if anyone is still doing it but some car audio manufacturers used to have a low frequency high pass filter, variable between about 20 and 60Hz. There's no point sending that to the amp if it'll never be heard.

"I'm going to investigate the bandpass box. I really like that idea, it seems like the sealed woofers would be better based on what you said about the low bass and that the bandpass would give it a little extra umph. Also that would be better for packaging and I could even maybe do something cool with the top (plexiglass?)"

There are thousands of bandpass enclosures out there and as a matter of fact, that removable panel makes it much easier to change drivers if they're damaged. You can go to a sign maker and have your logo laser etched or painted inside, too.

I have an Infinity Kappa Perfect system in my truck, so, I know what you mean about the venting with the windows. I'll play with WinISD in bandpass..

"At JL I can't remember who I talked too... I called tech support and spoke with someone there. Do you have someone you recommend?"

I talked with Ward and he's the one I mentioned. I did car audio for a long time and one of the dealers I worked for carried Boston Acoustics but the owners didn't want to pop for box design software, even though they bought an Audio Control RTA3050A and paid for the updates. Anyway, rather than design boxes the hard way (calculator and worksheet- done it and hated it) and since we didn't have the software or an Excel sheet, we would call the manufacturers and ask what worked best for their drivers. Ward was at Boston Acoustics at the time and then moved on to Nakamichi. I left and didn't know where he went but I needed to call JL a couple of months ago and when I asked who I was talking with, it turned out to be the same person.

 

[highfigh]

Tech support (regular "joe" techs anyway), especially at JL, will never give a response to something that may cause a higher rate of failure with their products. (Bandpass loaded woofers tend to have higher rates of failure due to the user being unable to hear the distortion clearly)

Most tech support depts. have become useless for the most part. There are a few that are still good though.

Bandpass is difficult to get right, let's put that out there to start. Wide bandwidth is difficult to achieve without the enclosure(s) getting quite large. The wider the bandwidth (typically) the larger the enclosure. Bandpass requires high degrees of accuracy for volume. .05ft^3 (in error) can change the tuning a fair amount and result in what sounds like a "one note wonder".

And this is why we use box design software. You ought to try designing a box without being able to model it. Empirical testing has its place but it takes a lot more time to get it right. With good modeling software, the results aren't as hard to achieve but the space where it will be used has a huge impact on how it will sound. Extreme bass extension in the box design won't work in a small car but in a moderate sized room, it does. On a boat like this, 40Hz-100Hz will work well and if the system has an EQ, minimizing peaks should be fairly easy- it's the dips that cause problems.

One note wonders are great for making license plates vibrate.

 

[MidnightSensi]

I will take a look for something passive, like maybe some RCA high pass filters or something? Like 45Hz and above?

I think that's a really good idea and might make more of a difference than anything else, because below 40-45Hz those drivers go crazy and its hard to make much noise in an open environment like that.

I'm gunna search around and look for something. Maybe buy a few 40, 45, 50 etc and then test them once in the boat with an SPL meter to see where I start to gain..

And this is why we use box design software. You ought to try designing a box without being able to model it. Empirical testing has its place but it takes a lot more time to get it right. With good modeling software, the results aren't as hard to achieve but the space where it will be used has a huge impact on how it will sound. Extreme bass extension in the box design won't work in a small car but in a moderate sized room, it does. On a boat like this, 40Hz-100Hz will work well and if the system has an EQ, minimizing peaks should be fairly easy- it's the dips that cause problems.

One note wonders are great for making license plates vibrate.

Yeah, I'm using WinISD and I've been playing with the bandpass boxes and they look really cool, especially for this application...except for one thing: size. Everything I model that looks like it would work well is really big.... where I could just stack sealed boxes.

That was always the arguement my friend would have with me when we were first getting into prosound stuff... I'd always like the scoops because of the output but he finally got me to realize we could just run more sealed boxes because they were smaller and get the top end output AND the low end output. Because for every scoop we could have three sealed (with the stuff we were using at the time, I know that doesn't always hold true). It's just interesting to see this pop back in.