Ricci

Excellent. Please post some pictures after paint. I'd recommend some foam lining placed strategically in the back chambers to knock down HF garbage. 

FYI Maglito...Frame OD on this is 21". It'll be tough getting it into 22.5" height with feet. Not impossible though. I believe my home cabs are about 22.5 x 22.5 on the driver baffle but they do not have feet. 

The driver was tested in about 4.5ft sealed after driver displacement and bracing. Test cab was 23x23x20". At home I have them sealed in roughly the same amount of volume per driver. 

They work great. Bring the EQ and the POWER. Adjust to taste.

One thing to be aware of is with a moving assembly that weighs 1Kg these can shake the hell out of a small enclosure at war volume. That's a big part of the reason mine are dual opposed. You'll need some mass and grippy feet to hold them in place. 

Bravo! Very well executed. 

BB holds screws better as well. In general I avoid MDF or HDF when possible, especially on larger cab sizes. For things like small monitors and car subs it isn't a bad choice to save some money. 

I have never heard of them. A few internet searches may be in order. 

Hello Abraham...It depends.

The usage and material being put through the subs make a big difference. If we consider that the B&C rating is 1700w continuous and the min impedance will be somewhere around 5.5 to 6 ohm in a cabinet, it seems like a starting point of about 100v would be suitable. This may need to be adjusted up or down depending on the specific use case, but this seems a reasonable starting point. I'd advise watching the video from Bennett posted above. 

As previously mentioned a strict peak voltage limiter isn't the best for this type of job. 

With four 4" fullrange drivers covering most of the frequency range how are you planning to deal with comb-filtering, HF beaming, off-axis power response, etc?

Pretty much all ports can be made to chuff and compress. Yours seems to have generous flaring which would help. The amount of bends may cause a lot of turbulence and the length looks really long, so watch the pipe resonance. Also the tuning would be difficult to judge with the end terminations and so many 180deg turns. This almost seems like it could be made into a TL variant. 

If it were me I'd probably move the vent to the bottom somewhere to prevent the possibility of something falling in. I'd try to minimize the bends in the vent as well. Just somethings to consider.

Nice renders BTW. 

It's  complicated to answer. It really never is as simple as labeling something 500 watts. Audio signals vary constantly. The speaker impedance and diaphragm excursion vary with frequency. Voltage and current vary into the impedance of the speaker. The key consideration is usually duration of the signal as far as burning coils goes. The other is the peak signal possibly causing mechanical damage to a driver. Most speakers will handle extremely high power inputs at certain frequencies if the duration is very short. At other worst case frequencies they may be cooked with far less power than the rating if the duration is long enough. 

The answer is it depends. 

16 hours ago, peniku8 said:

 Even 400W at 5Hz probably produces no meaningful output 😅

Sure it does, you just need a few hundred cubic feet of volume for the sub cabinets!

8 hours ago, Dionysus88 said:

Quick question. Will top loading these 21s on oak floor and the 32 on the concrete floor improve sound? I was thinking of using double granites/marble on top weighing them down. 

This is another question that really cannot be answered without more details of the setup, cab alignments, room and measurements. It depends...

Note that the xmax on these is 18mm and that's at 50% BL...Plenty for 30Hz and up work but once you start trying for 16Hz or lower cinema bass it could use a bit more. 

I would certainly expect about $10K if not more for a finished retail version of the sub. 

If DIYing it perhaps you could get that number down to the $7K range if the components were purchased well under msrp to offset the cost of the cabinet. The amount of hardware used to professionally finish a cab like this adds up quickly. Wood, Duratex or similar, handles, lining, wire, screws, casters, grille, skid rails, etc...Lot's of labor hours too. 

I've heard of a few M-Force units being burned up. I wonder if they have got a handle on that. The motor/ coil system is really beefy and it's very efficient but the M-drive is capable of generating a ton of heat in it over time. 

It's hard to advise what is correct without more details. Measurements of the responses at the listening positions would help. 

The 21's appear to be vented or possibly a TL variant? Do you know what the tuning is on these? 

2 hours ago, ChikoRomantiko said:

The frequency response is taken from the original pdf 451 and 551

Looks like the conditions for those measurements are completely different. The response will be dominated by the enclosure alignment anyway. I would ignore these.

Either driver should work well in the Skram. I would suggest the 551 due to a little bit of extra power handling and functional xmax. 

Nice build! 

Ok. I had a look in HR. It had been awhile. 

I'd recommend a 3rd order BW at 24Hz or a 4th order LR HPF at 21Hz. This is for operation with all vents open. 

4th order LPF adjusted to taste for blending with the mains. Somewhere between 50-120Hz. 70-100Hz is probably what would work for most. 

The response looks quite good with just the high and low pass added. 

This is the response with the 21SW152-4. Most of the other recommended drivers are going to be close to this as well. 

If you want to take it a bit further You can add a single band of PEQ at about 195Hz to beat down the first out of band response spike. This would be best if measured and tweaked accordingly but as a start these specs are probably close enough for gov't work. 

This would be the final with the HP, LP and single band of cut EQ up top. 

Lots of good information on the behavior of some of the Hypex models. Thanks guys. 

On 1/4/2021 at 5:26 PM, peniku8 said:

I'll be posting some measurements of the Hypex FA123 soon. I'll also update my tests to streamline the process a bit.

What frequencies would ppl be most interested in? I thought of doing 1k, 60Hz for bass performance and 20Hz for sub-bass performance. I don't wanna take too many measurements, since everything multiplies so a 4 channel amp into 3 different loads with 3 different frequencies already makes 3^3=27 tests (1ch 2ch 4ch; 1khz 60hz 20hz; 8R 4R 2R).
I might as well drop the 1ch measurement for 4 channel amps as an edge case like that doesn't make much sense.

Sounds like a good plan to me. I know this stuff isn't quick or easy so whatever makes sense to you...

Thanks for putting in the effort and sharing the results. 

Oh look an update! Looking great man. Have you been listening to the first one all this time? Thoughts?

On 12/30/2020 at 7:47 PM, jay michael said:

Hey Josh. Curious if you would be willing to make a recommendation for high and low pass filters with recommended slopes your Skram design. It’s been a while since I’ve had mine out with the pandemic and all, but I’m planning a day at our studio tomorrow to get everything plugged in and spend some timing tuning and tweaking. Planning to get the measurement mic out and spend some time dialing in the system so I don’t get rusty haha. I’ve been happy with the setting I’ve been running which I don’t remember off hand but I’ve got some different amps on hand so willing to try some new things. Another goal for tomorrow is to try and get some comparison data between the Cvr 3002’s and the powersoft k-10. 

I'm pretty sure I posted some rough starting filters somewhere in this thread. I'll have to try and find them. 

Great pic of the sunset. Looks like a good time!

Whatever works...LOL! No judgment here. 

No offense to RF as they do have some sharp guys but the whole, driver optimized for sealed / vented / BP and don't use it in another alignment, is for the most part antiquated thinking from back before modern signal processing. There are drivers that are better suited to some jobs than others make no mistake, but this is not one of those. Usually the reason you will hear that drivers are not suited for sealed is the qts is too low (IOW too efficient) and without EQ it will be bass shy because the top end gains sensitivity quickly and overpowers the low end without EQ. In this case RF is assuming that these drivers are going to be used for car audio SPL comps and the like and ported will be way louder than sealed and will also handle high power inputs longer. I can see why they would recommend this for their statement competition driver but if the app is not putting up big scores in a Tahoe it's one of the top high power sealed drivers available. 

It's 2020 and unequalized frequency response is much less of a priority than it was 30 years ago. 

As far as testing goes. There is nothing happening right now and for the immediate future. I've had to turn away a bunch of companies and projects since this time last year and I'm still sitting on a whole summers worth of testing from well previous to that. I'm not planning to be done completely, but after 10 years my priorities and other life goals have shifted and I can't find the hundreds of hours to put into testing, and publishing every year, like I once did. 

On 11/14/2020 at 1:06 AM, SME said:

I think @Ricci's M.A.U.L. uses a 12" pipe.

Yep