From Russia with love! :-)

ABT_Sportsline

Hi! I'm from Moscow, Russia. I got a question about MM2124.
1. What power must have amp for this sub...
What about MacAudio Z2200?

2. What volume need Single Sealed box.

P.S. Sorry for my English! :-)))

PolkThug

Welcome to Club Polk!

swerve

welcome - we love the Russia around club polk!

enjoy your stay!

-adam

AsSiMiLaTeD

I love how you answered his question...:-)

The pPolk site shows that the sub is 400 watts continuous, so an amp somewhere around there should be good.

You'll need .88 cubic feet on internal volume with a single sealed box, but I don't think that includes speaker displacement...so you'll need .88 cubic feet, but that's in addition to the speaker that's sticking inside the box...I think. Best thing to do is to use THIS box plan on the Polk site...

ABT_Sportsline

Can u tell me: what sound will be with volume 28 liters ???

swerve

I totally missed the question... atleast I was warmhearted

Jstas

OK, .88 cubic feet is 24.92 liters so a 28 liter box would be a tad too large. Infact, it would be a good 10-15% too large because 28 liters comes in at .9887 cubic feet on the dot.

You might want to find a smaller box for the subwoofer or build your own.

As far as how it would sound, well it would defintly be loud and "boomy" but, because of the larger volume of air, the subwoofer would tear itself apart eventually. That is because there would be insufficient pressure inside the box to control the movement of the cone.

For the amplifier, if I am reading the site correctly, the Z2200 puts out 600 watts RMS into 4 ohms. If that is the case, the MM2124 only handles about 400 watts RMS at 4 ohms. A closer match on teh Z series of amps would be that Z2100 but, not knowing what thier price point is, the best match for the MM2124 would be the Maximus 2.150 which is a much better match at 400 watts RMS at 4 ohms. The peak value is 1,000 watts but that is not nearly as important as they RMS value.

So, I would find a slightly smaller sized subwoofer box and grab that Maximus 2.150 amplfier if you are going with mac Audio gear. That will ensure that you will get the best performance from a Polk Audio MM2124 subwoofer.

Hope that helped! Wasn't easy getting those metric conversions down!

AsSiMiLaTeD

Based on the box on the Polk site, it looks like the .88 (or 24.92 liters) does not factor in the size taken up by the speaker in the box. The measurements of Polk's box come out to about .98 cubic feet of total internal volume (some will be taken up by the speaker), which is right around 28 liters...(I cubic ft is 28.316 liters, .98 cubic ft should be about 27.75 liters)

so if your box is 28 liters, if anything you have a bit more than needed. In this case, it's better to have too much than not enough air space.

I think that'll work good for you...

Jstas

Originally posted by Polkmaniac

so if your box is 28 liters, if anything you have a bit more than needed. In this case, it's better to have too much than not enough air space.

Not true. In the case of the MM2124, too much air volume does not provide enough air pressure to adequatly control the movement of the sub. It relies too heavily upon the spider and surround which will over extend them. This dramatically shortens the life of both and cause premature and often catastrophic failure of the speaker. It would be better to have too little air space because the box would then merely truncate the frequency response of the speaker. This is not entirely desirable either but a far sight better than shredding your speakers and is easier to band-aid with extra polyfil stuffing and bandpass crossovers to limit the signal sent to the speaker.

Also, with the large air volume, you can artificially change the impedance of the subwoofer which would cause a high current draw on the amplifier. While it is unlikely, it is possible to damage the amplifier by putting a speaker in a box that is too large.

It is honestly better to have a box too small than to have a box too large.

AsSiMiLaTeD

Jstas, I may be wrong, but I think your numbers are a bit off. If I take the measurements of the box here on the Polk site (17x15x9.625) and strip away the .75"MDF on each side, I should have internal measurements of 15.5x13.5x8.25, no?

Using those measurements, I get a cubic ft area of .98. This is bigger than .88, so I assume it is accounting for the space in the box taken up by the speaker? Or something else? Either way, it doesn't matter really why, assuming Polk knows what they're doing, they built the box that big for a good reason.

So that box comes out to 27.86 liters of internal volume...only a tad bit smaller than the 28 he's building...right?

I don't know squat about sub boxes, but my logic tells me that should be right...

If I'm wrong, explain it to me so I know...

AsSiMiLaTeD

Originally posted by Jstas
Not true. In the case of the MM2124, too much air volume does not provide enough air pressure to adequatly control the movement of the sub. It relies too heavily upon the spider and surround which will over extend them. This dramatically shortens the life of both and cause premature and often catastrophic failure of the speaker. It would be better to have too little air space because the box would then merely truncate the frequency response of the speaker. This is not entirely desirable either but a far sight better than shredding your speakers and is easier to band-aid with extra polyfil stuffing and bandpass crossovers to limit the signal sent to the speaker.

Also, with the large air volume, you can artificially change the impedance of the subwoofer which would cause a high current draw on the amplifier. While it is unlikely, it is possible to damage the amplifier by putting a speaker in a box that is too large.

It is honestly better to have a box too small than to have a box too large.

Okay...I was just going off what I was told...should know better than that.

But if the box is supposed to be 27.86 liters and it's 28 liters...how much of a difference does that really make???

ABT_Sportsline

I'll build my own box! 25 liters. Does it need some fill?

AsSiMiLaTeD

I'd hold on a minute...I wouldn't take my word alone on this.

Jstas is saying something different, and he know more about this stuff than me...so you may wanna stick around a bit and see how this unfolds...because we're telling you two different things...

swerve

I built mine to polks specs right out of the book. seeeeemed to work aight... lol

exalted512

holy crap youre right. and all this time ive been recommending .88ft^3. I did the math and it came out to be 0.98389ft^3, which is 27.861 L^3. The difference is equivalent to 0.005ft^3.

All in all, you're perfectly fine.
-Cody

Jstas

Originally posted by Polkmaniac
Jstas, I may be wrong, but I think your numbers are a bit off. If I take the measurements of the box here on the Polk site (17x15x9.625) and strip away the .75"MDF on each side, I should have internal measurements of 15.5x13.5x8.25, no?

Using those measurements, I get a cubic ft area of .98. This is bigger than .88, so I assume it is accounting for the space in the box taken up by the speaker? Or something else? Either way, it doesn't matter really why, assuming Polk knows what they're doing, they built the box that big for a good reason.

So that box comes out to 27.86 liters of internal volume...only a tad bit smaller than the 28 he's building...right?

I don't know squat about sub boxes, but my logic tells me that should be right...

If I'm wrong, explain it to me so I know...

I don't really care about the size of the box in the plans on the site. The recommended volume is .88 cubic feet and that is what will let the sub perform at its best.

Also, if these are plans from the "Sub Box Plans" section, then they are not always tailor matched to the current line of subwoofers. Some of the older subs utilized larger enclosures which is where some of the plans came from. If you look for the MM2124 in the Sub Box Plans section, you will find these plans:

http://www.polkaudio.com/car/toolbox/subboxplans/subbox_plan.php?id=58&mesurements=standard

That matches the .88 cubic foot measurement. When shopping for sub boxes, it has been understood that volume measurements are a rough estimate of what the box will be with the driver installed. The size of the box may show a larger volume when measured because it needs to allow for the driver size. Since so many of the buying public have severely inadequate math skills, it is easier for Joe Consumer to buy a .98 cubic inch box that is labelled as .88 cubic inches so that it fits thier application properly. Often times, you can get away with a <10% size difference without issue but go above 10% on the high end and you are going to damage your gear.

If it is different in Russia, I do not know but then again, how would I know if all my knowledge is geared toward dealing with the U.S. market which is geared for dummies? I can only offer advice on my realm of knowledge which is why I went for exact measurements based on sub specs. However, is the plans I posted are followed, they will yeild the optimum enclsoure for that subwoofer.

Now, if you are talking about the box that MM124 came in, that has one rouded edge which makes up for the .1 cubic inch difference in the overall internal measurements.

Jstas

25 liters should work just fine and an easier number to hit than the 24.92 liters that .88 cubic feet works out to. It is well within an error range that is entirely acceptable.

exalted512

No-they dont match the .88 dimensions. do the math:)
-Cody

AsSiMiLaTeD

Originally posted by Jstas

Also, if these are plans from the "Sub Box Plans" section, then they are not always tailor matched to the current line of subwoofers. Some of the older subs utilized larger enclosures which is where some of the plans came from. If you look for the MM2124 in the Sub Box Plans section, you will find these plans:

http://www.polkaudio.com/car/toolbox/subboxplans/subbox_plan.php?id=58&mesurements=standard

That matches the .88 cubic foot measurement.

John, those are the exact plans I referred to in my post, the right ones for this speaker. If you look at the measurements, they do NOT come out to .88 cubic ft, they come out to .983something.

That's was my whole point altogether - I think you missed it. Either that I am missing my ability to do simple math (possible).

The box that Polk is reccomending has an internal volume of .983 cubic ft, not .88...my thinking is that they're compensating for something (initial thought is the speaker itself).

What am I missing here?

AsSiMiLaTeD

Okay Cody, you and I seem to be on the same page here, so maybe you can help me understand why Polk build that box bigger than .88. My initial thought was to compensate for speaker displacement...but when I factor in the size of the speaker in comparison to the size of the box...it doesn't quite add up...

Any Thoughts?

Jstas

Originally posted by Polkmaniac
Jstas, I may be wrong, but I think your numbers are a bit off. If I take the measurements of the box here on the Polk site (17x15x9.625) and strip away the .75"MDF on each side, I should have internal measurements of 15.5x13.5x8.25, no?

See, the thing is that you can't take .75 inches off of each measurement. The size difference is greater for the side panels of the box. If you look at the picture, the side panels are indented a tad. That is greater than .75 inches on the lateral internal dimensions. Also, even if you take them as a flush measurement, they still don't add up to a .75 inc difference. More like a 1.50 inch difference. Also, the top and bottom of the box overlap and the front and rear are also mounted flush and teh distance there isn't a simple .75 inches either.

I fell into this trap on the first box I designed myself when I was 16 for a pair of 8 inch Kenwood subs. I needed a total of 1.2 cubic feet and because I did the funny math and didn't think about the design, I ended up with 1.56 cubic feet which was too big.

And Cody, use your brain and look at how the box is built. They will match .88 cubic feet, you need to consider not only how the box is designed (i.e.: external shape) but also how it is constructed. Unless you were to do 45 degree mitred cuts around every corner and make composite corners, you will not attain the desired air space by subtracting .75 inches from each extrenal dimension. Infact, you will be luck if your cube's panels even line up at all. I would also recommend against the mitred corners because they are not as strong as the butt joints or mortised joints that typical box construction lends itself too. Mitred joints are also more likely to leak.

exalted512

Thats also a generic picture used for all the mm2XX4 series. Theres also 2 different boxes listed, a q-logic and a subzone yet all the boxes are the same. The shape is also specified as rectangular. Well have to wait til thom, josh, or kim comes and lets us know whats going on.
-Cody

AsSiMiLaTeD

John, what picture are you looking at? Are you talking about the one towards the top of the page that's not the box being described in the measurements? I think that's just a sample picture to take up space, because the box being described is a rectangle, not what's pictured.

And, based on their measurements, I wouldn't even think of indenting the sides, their specs and measurements don't suggest that...

And I did factor 1.5 inch off each measurement, not .75. How does that not work? I know there's overlap, but shouldn't it not make a difference since we're talking internal measurement?

AsSiMiLaTeD

Originally posted by exalted512
Thats also a generic picture used for all the mm2XX4 series. Theres also 2 different boxes listed, a q-logic and a subzone yet all the boxes are the same. The shape is also specified as rectangular. Well have to wait til thom, josh, or kim comes and lets us know whats going on.
-Cody

I PM'ed Kim with the link to this thread, hopefully we'll get a response. I imagine John is right, I just can't figure out why...

Jstas

Here is a picture of your Q-Logic QLH-.8512SE



Do you see the sides of the box?

Also, here are the dimensions:

# for one 12" subwoofer
# 0.85 cubic feet internal volume
# dimensions:

* width: 16-15/16"
* height: 16"
* bottom depth: 12-3/4"
* top depth: 7-1/8"




Here are the dimensions for the Polk Audio box:

Overall External Dimensions
Width 17" (43.18cm)
Height 15" (38.10cm)
Depth 9-5/8" (24.45cm)

Pretty close in size and the Q-Logic box is listed as having an internal volume of .85 cubic feet. Which is 24.07 liters for those who are keeping track.

Jstas

Originally posted by Polkmaniac
John, what picture are you looking at? Are you talking about the one towards the top of the page that's not the box being described in the measurements? I think that's just a sample picture to take up space, because the box being described is a rectangle, not what's pictured.

And, based on their measurements, I wouldn't even think of indenting the sides, their specs and measurements don't suggest that...

And I did factor 1.5 inch off each measurement, not .75. How does that not work? I know there's overlap, but shouldn't it not make a difference since we're talking internal measurement?

Doesn't matter what picture is used, in geometry all rectangles are squares but squares are not rectangles. Rectangles have square corners but not square sides. Squares have equal corners and are equal sided and no measurements discussed so far are equal sided therefore, they are all rectangular enclosures. Even the ones with a trapezoidal shape have at least one side that is not square.

Also, you have stated that you factored in 1.5 inches for each measurement. You can't just take off a measurement for eacxh individual measurement. It is not that simple.

Bottom line, no one is thinking about this clearly and I cannot easily describe it without visual aids. So I will stop now and let everyone think I am ignorant and live in my blissful ignorance.

AsSiMiLaTeD

Originally posted by Jstas
Also, you have stated that you factored in 1.5 inches for each measurement. You can't just take off a measurement for eacxh individual measurement. It is not that simple.

Bottom line, no one is thinking about this clearly and I cannot easily describe it without visual aids. So I will stop now and let everyone think I am ignorant and live in my blissful ignorance.

We just built this exact box for my friend using 3/4" mdf, and the internal measurements came out to be 15.5x13.5x8.125.

Maybe I built it janky...but that's how it came out...

exalted512

I think it is supposed to be .88, but fact is, the dimensions on their site do NOT come out to .88, they come out to be .98389 like i previously said. The dimensions do not closely resembly the ones on polks site. They are meant to be two seperate boxes. Why else would it say the enclosure is .88ft^3 when its actually .85.
-Cody

MacLeod

I wouldnt worry about their dimensions. Just stick to the spec for recommended enclosure size which is .88 ft^3. Simpler that way!

Jstas

Look at the sub box plans again and look at the manufacturer and model numbers of the sub boxes that were used for reference. The model of the Q-Logic that is listed is the QLH-.8512SE. That is where the measurements I listed came from and that is what was referenced as a similar enclosure to the Polk Audio plans.