So how does this combination "sound" to you

Jethro

Originally posted by MrDHEJ
The information here on the Polk site in regards to box volume states: A smaller box will require more power, but produce tighter bass in the whole spectrum, where as a larger volume box will focus more on the lower freq. and be more boomy and louder at a sacrifice to the higher bass freq., but require less power.

That statement is not totally correct (with regard to sealed boxes, anyway). A sub with tight bass typically has excellent transient response without a lot of overhang or ringing. This is usually attained by using a sealed box alignment at or aroung .707 Qtc. "Boominess" is usually defined as too much upperbass emphasis - a characteristic found in boxes with .9 Qtc or higher (smaller boxes).

A smaller box will indeed require more power, but it will also have better power handling. When designing an enclosure for SQ purposes, you want a Qtc as close to .707 as possible, while keeping within the driver's excursion limits.

If you took the MM124's Thiel/Small Parameters.....

Electrical
Overall Frequency Response 20Hz - 200Hz
Nominal Impedance 4 ohms
Power Handling (continuous) 500 w
Power Handling (peak) 1000 w
Efficiency 87 dB
Voice Coil Diameter: Driver 2" (5.08cm)
Magnet Weight 66.00 oz.

---

Driver Mounting Depth
Top Mount 6" (15.24cm)
Bottom Mount 6-1/2" (16.51cm)
Cut-out
Driver Cut-out Diameter 11-1/8" (28.26cm)

---

Theile/Small Parameters
Recommended Enclosure Sealed or Band Pass
Resonant Frequency 27.5 Hz
Qms 13.06
Qes 0.476
Qts 0.46
Vas 81.12 L / 2.865 cu ft
Cms 221 Micro Meters
Bl 14.45 Tesla Meters
Sd 511 sq cm / 79.21 sq in
Xmax (mechanical) 1.0
Le 1.92 mH
Mms 151 g
Driver Weight 15.8 pounds
Pe 500w

.....and entered them into WinISD Pro, you would find that it could take 600w RMS in 2 cu ft sealed without exceding the 25mm Xmax (Qtc would be .717).

1.25 cu ft would get you a Qtc of .83, which is on the upper limits of what is considered an SQ alignment.

.88 cu ft would yield a Qtc of .93, which would have great power handling, but would be a little boomy for SQ purists, unless you had an EQ to tame the boost in response between 60 and 100hz.

For more information on this, check out The Loudspeaker Design Cookbook by Vance Dickason. The newest edition even has a section on how a car's interior boosts (aka transfer function or cabin gain) the lowest octaves, and how that transfer function varies from vehicle to vehicle.

Jethro

Originally posted by sntnsupermen131
Jethro, wouldnt by increasing the box size the SQ go down
im wondering because if it has more air, the sub can not control itself as well b/c its "backbone" is not supportive enough?
-Cody

If you go too large, then yes, power handling will be decreased to a point that SQ will suffer due to over-excursion (typically with Qtc's lower than .577, depending on the driver). But, enclosure size is relative - some 12's work well in 6 cu ft+, other 12's work well in less than 1 cu ft.

For a better explanation than I could ever give, follow this link:

Sealed Box Tutorial

MacLeod

Nostalgia bump! Hard to tell with the new forum and deleted posts/threads but I think this was one of the first threads I ever posted in here after buying my first set of Polk Audio speakers, MMC690 6x9's for my 2002 Dodge Ram at Circuit City in Temple, Texas in November 2003.

For some reason I was thinking about this place today and the good times we had 15 years ago. There was about 9 or 10 of us regulars that knew just the basics but were constantly looking for new things to learn. I bet we each started a new thread here every day for every little new thing we learned LOL. This went on for like 5 years!

Man I wish we could do some kind of reunion for all of us from 15 years back. Cody, Vinny, John, Neo and whoever else, first beer's on me!

TopperDude

Hey MacLeod hows it going! I remember reading a lot of great posts from you ages ago. You still competing in car audio? Curious to know how your system has evolved these last few years.

MacLeod

TopperDude wrote: »

Hey MacLeod hows it going! I remember reading a lot of great posts from you ages ago. You still competing in car audio? Curious to know how your system has evolved these last few years.

I never "stopped" competing because I always plan on going back but I haven't been to a show since 2015. Working 2 jobs really put a damper on it. I had Tang Band 3" drivers in the A pillars, on axis running 250 Hz and up and my trusty old SR 6.5's in the door of my 2012 Accord. I had 2 Polk MM12's in the trunk all running off a Rockford Fosgate 5 channel tune by my Pioneer P99. It was the best sounding system I ever had.

I traded my Accord back in '16 for a F150 and haven't competed with it. I went with a Morel Hybrid 6" component kit, 6's in the doors and the tweeters in the pillars. I used the old PVC end cap trick to make some pods and have the tweeters mounted on axis and aimed at the opposite C pillar. Im using a single JL 10 powered by a JL RD900/5 with a JL Twk88. For a head unit I did a Forscan hack where you can go in make the speaker outputs of the stock head unit low level and defeat the factory EQ. Then you just crimp or solder on some RCA end caps and you've got RCA outputs from your factory head unit that plugs right into your processor and you retain your factory controls and features. It worked really well.

TopperDude

Cool! Hows the F150 sounding compared to the Accord? any tweaks and upgrades you still got planned or is it finished?

MacLeod

TopperDude wrote: »

Cool! Hows the F150 sounding compared to the Accord? any tweaks and upgrades you still got planned or is it finished?

I've always thought bigger vehicles like trucks sound better but that could just by my personal preference. That said, my Accord sounded better. It's the best sounding system I've ever had. Those Tang Band 3's are the perfect car audio speaking in my opinion. Only speaker I know that will play from 250 Hz and up if they're on axis and sound awesome while doing it. I am REALLY considering taking out those Morel tweeters and putting some TB 3's in my F-150. It's not the most integrated look as they have to be mounted on axis and that makes them stick out more but man it's worth it to me.

Jstas

Bigger vehicles sound better because there's more room. That means your mounting locations are farther away from your listening position(s) which means the sound takes longer to get to your ears. Since every speaker has differing off-axis response fields, the more distance between you and the drivers, the more chance those sound fields have an opportunity to intersect and create a congruent sound stage. Cars exacerbate this because tweeters are often mounted very far from woofers and it can take a good deal of space to get the sound stage even without being able to locate any specific driver in the sound stage.

If you still had the Accord, I'd tell you to measure distance from drivers to the area where your head is and compare it with the same measurements in the F-150. The F-150 is likely a longer distance.

This was also why those kick panel pods were all the rage in SQ competitors for a while. That was about as far away from the listening position as you could get. For competition where there's nothing but a microphone in the car, that works great. But for every day use they were pretty stupid because not only do they get beat up but stuff like bodies, backpacks, groceries, etc get in the way of your sound stage.

But another reason that trucks tend to have better imaging is because the cabin is taller with a more upright greenhouse. You get less reflections at odd angles in a truck than you do in a car. Car windshields, front and rear, often have steep angles or odd curves or both and are bordered by large support pillars. These can create a sort of sound trap where reflections can cancel out program info or cause sound to be reflected away from the listening position. In a truck, it's more upright and square. Closer to a living room listening environment which has predictable reflection patterns and it's easier to tame those reflections.

Additionally, you'll notice stuff like better bass response because, while a typical mid-sized sedan might have a longer cabin space, the truck is typically half a foot to a foot wider and 1-2 feet taller with a more uniform cabin space (no sloping roof lines, not pinched cabin space at the top, etc). A truck cabin will be more square in all 3 axis where a sedan will basically have trapezoids or rounded diamond shapes on all 3 axis. That means that the truck has more airspace in the cabin. It's harder to pressurize all that extra air space but at the same time it gives bass frequencies room to extend a full wavelength at lower frequencies. That means you hear more of your low end response instead of having it vibrate body panels or extend outside of the cabin because the wavelength is longer than the cabin space.