95Honda

You will get more power running one on each amp (2 ohm load per amp) then all 4 on one amp (1 ohm load)... In your case, if those amps are 1/2 ohm stable, you would need to strap to possibly get the most out of the amplifiers... BUT, when strapping, you do so at poorer efficiency, higher distortion and less dampening... It isn't really worth it... If you had 8 ohm subwoofers, then I would consider it...

Build the box solid, no need for internal 45-degree corners with a sealed box...

There are no advantages to strapping at... Unless your system impedance is so high that you simply can't get power out of the amplifiers... But that is rarely the case, rarely...

God I bet that is loud...

Is that a joke? No deadlifting?

^^ That is a good example of why DIY is the way to go... For almost $3K you can build a set of subwoofers with amplification that is beyond insane... Hell, my pair of XXX18s, 5Kw RMS of power + processing and cabinets was only $2K...

Yes, the amplifier will produce different levels depending on the impedance it is driving, this is due to the "impedance curve" of the overall alignment. It isn't impedance "rise" as it goes up and down, there is no such thing as just "rise". When you model, look at the impedance. At it's lowest point, that is where you get maximum power out of the amplifier. If that lowest point is anywhere near the peak in your vent velocity, then you need to model for the max power of your amplifier. Most of the time your vent has maximum airflow at resonance, it also happens that this is also the lowest impedance point, or close to it...

That should work just fine. Only thing I would suggest is to add some type of brace between the drivers to connect the baffle to your removable panel. If that is 3/4" MDF, that is a huge panel to be left unbraced... That is the stuff that kills output... Even just a simple piece of MDF...

The room, as implied by M5 and Impious, is hugely responsible for the end response. If you aren't going to get the gear to measure and correct, I would build the sealed box first. That response will probably be really flat in your room. It is also really easy to get that sealed box right. You need some type of correction to get flat response, especially at certain listening positions, it is best to have a design that requires the least amount of correction to get there...

The driver has a fairly high Q. You are going to get a bump in response vented, post up your sealed graph...

Post the T/S parameters you are using...

I haven't modeled the subwoofer, so I cannot comment on that particular driver, BUT, here are a few things you can be certain about: - You are dealing with music that you want to hear accurately. This isn't going to be a time to experiment with complicated enclosures like a band-pass, you don't want to start changing your music because your playback system isn't linear. I wouldn't mess with a transmission line either, they need to have the stuffing adjusted for response. And I am not saying that these enclosures can't be linear, they are just harder to get to that point. - Build something that can be predictably modeled. Easiest is a sealed box, second easy would be 4th order vented. The sealed box is easy, I would just shoot for a Q of .7, that is nice and flat and will give you the most neutral output signature. If you were happy with the 8" ported, the 15 sealed will give you enough output. If you go 4th order, design for a flat response, no ripple and tune somewhere below 30Hz. The important part will be designing for no ripple. If you have even a few db of ripple the room may exaggerate it and you make change your music to compensate, exactly what you want to avoid. - When you build the cabinets make them solid. If you can only use 3/4" MDF you need to brace well. You need to stay conservative with the cabinet designs, not a time to experiment with weird shapes. Make sure you joints are tight and well sealed, any little variance in enclosure tolerances is going to result in annoying rattles and noises. If you use some type of material to make your vents other than wood, use a glue to bond them wherever they touch wood, and make sure it is a glue that isn't rock hard. I have build many subwoofer system for home audio systems, probably a hundred or so since the early 90's... The ones that have sounded the best were the ones that I built sticking to some of these guidelines. I have build more complicated designs, but I couldn't always get them right the first time. The sealed alignments and almost all of the 4th order alignments always turned out the way I modeled, if I built them right... Simple design, solid cabinets, and good room placement will be key...

Do you(they) already have the driver(s)?

Honestly, with the level of technology today, any LED/LCD readout DC voltmeter will be accurate enough for what you want, DC is easy to measure. I would have no problem using a $4 e-bay meter... I would just get whichever one looks the best and is easiest to mount...

I don't think it will be a problem, the low Fs doesn't always correlate to lower efficiency up high... I think he kept the moving mass lower, that is more important...

Glad you are OK.

That is the point, the equipment in the video wasn't that of a professional. It was mostly cheap, run of the mill, hobbyist grade stuff. Again, great stuff for troubleshooting, but not for trying to give accurate certification of claimed specifications. This kind of why most "clamp" tests are out the window. And, for the record, the equipment is out there to do proper testing, it just costs a lot more and isn't really justified for 99% of us... Who knows, that amp might make less power with the proper test equipment, but it is irrelevant... But this is falling on deaf ears, so I won't try and get you to understand this anymore.

Some of you guys are missing the point. It has nothing to do with the power made. Even if there is a retest and the results are different it is not a valid test, that is the point. If the amp would have made a gazillion watts I would have taken one glance at the test equipment and laughed... I have had brand new, un-calibrated other than factory cal, Fluke 97 IIIs that were off by 30VAC (while reading 120VAC)... These were true RMS, $500 DMMs... It isn't common, but it happens... Is the load non-inductive? Is it cooled? Is it rated for that kind of power? How much ripple is on the DC input? Then you throw in all the really cheap garbage test equipment that you can't really trust... The stuff is good for troubleshooting, but not for validating performance measurements... I could care less about IA's amplifier performance. But when I see tests that are obviously flawed, I think it is worth pointing out... Stop riding the internet bandwagon and use your brain...

The gain position is meaningless. It doesn't matter if it is all the way clockwise or counterclockwise... Have you designed/built your box yet? How do you know what size amp to get if you haven't?

Agreed.

Or just make sure everything is at the same ground potential, and you will never have noise if the equipment isn't broken...

The audio community as a whole has embraced RMS as an term for continuous power... It has stuck one way or another for the wrong reasons... I think you guys are splitting hairs here, we all know it isn't derived correctly. But, more importantly, to help the masses, we need to make the disconnect where it counts, and that is the incorrect correlation of RMS as a loudspeaker term for anything but a thermal rating...

The important thing is that, no matter how we define RMS, it doesn't correlate to anything but a thermal rating of the voice coil... Except in the case of DSS, of course...

The RMS rating is a thermal rating of the voice coil. That is it. It has no correlation to absolutely anything else on earth, seriously... Is it a power requirement? No. Will it tell you how powerful is subwoofer is? No. Will it tell you how loud a subwoofer will be? No. Will it tell you an output difference vs. another subwoofer with a different RMS rating? No. Does it tell you what size amplifier you should run? No. How useful of a specification is it? it is the least useful specification given by a manufacturer, behind all other T/S parameters...

Seriously, if you don't model you will never know the difference...