Upgrade 8's or add a 12/15?

Centmaker · 08-07-2016, 06:42 AM

Hey guys I have the Hi-Fi system and an Alpine mrp-m850 amp that I want to put to use, of course if it accepts balanced differential inputs because I read it has to be able to. I plan on upgrading every speaker but first I'm going to add some bass.

I have several questions:

Should I upgrade the two underseat 8's with two 400 watt infinite baffle subs or just add a bigger single enclosed sub in the trunk? I think the underseat 8's might be louder or sound better but can 8" subs still go as low as bigger subs?

Also I read the signal from the head unit is good but the small amp in the trunk processes the sound and it's desirable to unprocess the sound?

I want to only spend about $300 on the bass alone since I already have the amp, but I still want to maximize that $300.

Fundguy1 · 08-07-2016, 07:31 AM

I'd do a single 10" in the trunk and use the ski bag if you have it to port it to the cabin. Using similar subs, a 10" will give you way more deep tight bass than 8s infinitely baffled and I prefer a sealed 10 over ported or 12s as it is tight clean bass. 12s will not be as tight and probably be overpowered vs rest of the system. 8 not as deep. Infinite baffle works between a sealed trun and the cabin, not under the seats. And if you just wanted noise to boom you'd be doing twin 12s in a ported box. Sound like crap but it'd wake up the neighborhood.

Centmaker · 08-07-2016, 07:37 AM

No, between the trunk and cabin it would be a sealed encloser, infinite baffle is for speakers that don't need boxes such as under the seat.

Fundguy1 · 08-07-2016, 08:22 AM

Quote:

Originally Posted by Centmaker

No, between the trunk and cabin it would be a sealed encloser, infinite baffle is for speakers that don't need boxes such as under the seat.

Incorrect. That is a free air speaker. Here is a description I found that's adequate to explain. He wants free air under the seat. He called it infinite baffle. Infinitebaffle would be sealed between trunk and cabin using the trunk as the box. Ported would be an actual box with a port which is what comes oem and with aftermarket plugged into oem enclosures like earthquakes or a box in the trunk firing into the cabin. And sealed would be a sealed box, typically in the trunk firing into the cabin.

There seems to be a lot of misconception about an infinite baffle, so here goes my stab at it with a link to a forum that has a lot of dedication and experience to them.

What I have gathered:

A baffle is a board a speaker driver is mounted to.

When a speaker is not attatched to anything, and the front and rear wave are completely allowed to go around the driver and are not in any way isolated or coupled, it is free air.

When it is on a baffle, the sound waves are forced to travel further to intersect. The smaller the baffle, the higher waves (upper frequencies) are no longer cancelling out as the baffle separates them. As we increase the baffle size, the longer it gets, the lower the waves that no longer cancel depending on 1/4 wavelength and total wavelength.

The 1/4 wavelength for 33Hz is 8.5 feet, the total wavelength is 35 feet. For a driver to effectively recreate 33Hz without any cancelation and all the way up from there, the baffle would have to be 35 feet out from the driver, or a total of 75 feet in diameter.

An infinite baffle is a "sealed" ROOM with a minimum airspace of 25 times the drivers Vas, so that the driver does not "see" the enclosure. Anything less, and the air acts as a spring.

Fundguy1 · 08-07-2016, 08:29 AM

So that said. Your optons are:
8" ported replacements under the seats. Not loud, tight, or deep.
10" or 12" infinite baffle between trunk and cabin. Loud, not tight, saves space.
10" or 12" ported box trunk mounted firing into the cabin. Loud, tighter than infinite, need to build a big box that takes up space.
10" or 12" sealed box
Not as loud as other 2 two 10"/12" options but tight crisp bass and smaller box than ported. This is my personal preference but it's your car. You pick.

mathematics · 08-07-2016, 08:52 AM

Quote:

Originally Posted by Centmaker

No, between the trunk and cabin it would be a sealed encloser, infinite baffle is for speakers that don't need boxes such as under the seat.

The underseat woofers are in a ported enclosure..,

Fundguy1 · 08-07-2016, 08:58 AM

Quote:

Originally Posted by mathematics

The underseat woofers are in a ported enclosure..,

He's new. He's learning.

Centmaker · 08-07-2016, 02:31 PM

Quote:

Originally Posted by Fundguy1

He's new. He's learning.

Yes I'm new, and I'm having problems differentiating infinite baffle from sealed. If I mount the subs between the cabin and trunk then the trunk is the enclosure. To me I see no difference.

Fundguy1 · 08-07-2016, 02:46 PM

Free air means just that. In the open. Free.
Infinite baffle is like a box but infinitely large, separated from the playing area. In this case, the trunk is the infinitely large box, the cabin the playing area.

For bass there needs to be two separate spaces. Trunk, sealed box, ported box. Really tweets are the only effective free air speakers.

mathematics · 08-07-2016, 03:15 PM

Picture mounting a speaker to an infinitely wide and infinitely tall baffle so that the front and back of the speaker are not going to create destructive interference. That's the theory. In practice, that's it possible. In practice, it means make the enclosure as large as possible. There's a world of difference between a 1cubic foot enclosure and 25cubic foot enclosure. That's sealed vs infinite baffle.

Fundguy1 · 08-07-2016, 03:28 PM

A sub without this separation of one body of air on one side from s seconditions body of air on the other is virtually ineffective

stylin20 · 08-09-2016, 04:16 PM

Depends on what your sound tastes are. Mine is a nice tight bass with some rumble. But not your crazy ass shit you hear for miles. I like it to hit hard but crisp. I went with a 10" Dual voice coil Hertz that I wired to 2 ohms. Sealed enclosure Bassworx RP10 model I believe. It was suggested by the salesman and a Hertz Amp. Couldn't be happier. Those 8's are great for midbass, but if you want that bottom end. You need a sub. 12" will move more air and be louder, but not as "Tight". The box is just under 1 cubic Ft. So takes up virtually no room as I can still fit my golf clubs, shoes and a golf cart in the trunk.

Good luck

Fundguy1 · 08-09-2016, 05:25 PM

Quote:

Originally Posted by stylin20

Depends on what your sound tastes are. Mine is a nice tight bass with some rumble. But not your crazy ass shit you hear for miles. I like it to hit hard but crisp. I went with a 10" Dual voice coil Hertz that I wired to 2 ohms. Sealed enclosure Bassworx RP10 model I believe. It was suggested by the salesman and a Hertz Amp. Couldn't be happier. Those 8's are great for midbass, but if you want that bottom end. You need a sub. 12" will move more air and be louder, but not as "Tight". The box is just under 1 cubic Ft. So takes up virtually no room as I can still fit my golf clubs, shoes and a golf cart in the trunk.

Good luck

My thoughts exactly. A quality sealed box 10" with good power is a winning combo for deep tight bass.

08-07-2016, 06:42 AM	#1
Centmaker Banned 13 Rep 81 Posts Drives: 06' Red 325i Join Date: Jan 2016 Location: Notre Dame iTrader: (0)	Upgrade 8's or add a 12/15? Hey guys I have the Hi-Fi system and an Alpine mrp-m850 amp that I want to put to use, of course if it accepts balanced differential inputs because I read it has to be able to. I plan on upgrading every speaker but first I'm going to add some bass. I have several questions: Should I upgrade the two underseat 8's with two 400 watt infinite baffle subs or just add a bigger single enclosed sub in the trunk? I think the underseat 8's might be louder or sound better but can 8" subs still go as low as bigger subs? Also I read the signal from the head unit is good but the small amp in the trunk processes the sound and it's desirable to unprocess the sound? I want to only spend about $300 on the bass alone since I already have the amp, but I still want to maximize that $300.
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08-07-2016, 07:31 AM	#2
Fundguy1 Major General 2032 Rep 8,339 Posts Drives: 335 e93 Join Date: Aug 2014 Location: Orlando, fl iTrader: (0)	I'd do a single 10" in the trunk and use the ski bag if you have it to port it to the cabin. Using similar subs, a 10" will give you way more deep tight bass than 8s infinitely baffled and I prefer a sealed 10 over ported or 12s as it is tight clean bass. 12s will not be as tight and probably be overpowered vs rest of the system. 8 not as deep. Infinite baffle works between a sealed trun and the cabin, not under the seats. And if you just wanted noise to boom you'd be doing twin 12s in a ported box. Sound like crap but it'd wake up the neighborhood.
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08-07-2016, 07:37 AM	#3
Centmaker Banned 13 Rep 81 Posts Drives: 06' Red 325i Join Date: Jan 2016 Location: Notre Dame iTrader: (0)	No, between the trunk and cabin it would be a sealed encloser, infinite baffle is for speakers that don't need boxes such as under the seat.
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08-07-2016, 08:29 AM	#5
Fundguy1 Major General 2032 Rep 8,339 Posts Drives: 335 e93 Join Date: Aug 2014 Location: Orlando, fl iTrader: (0)	So that said. Your optons are: 8" ported replacements under the seats. Not loud, tight, or deep. 10" or 12" infinite baffle between trunk and cabin. Loud, not tight, saves space. 10" or 12" ported box trunk mounted firing into the cabin. Loud, tighter than infinite, need to build a big box that takes up space. 10" or 12" sealed box Not as loud as other 2 two 10"/12" options but tight crisp bass and smaller box than ported. This is my personal preference but it's your car. You pick.
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08-07-2016, 02:46 PM	#9
Fundguy1 Major General 2032 Rep 8,339 Posts Drives: 335 e93 Join Date: Aug 2014 Location: Orlando, fl iTrader: (0)	Free air means just that. In the open. Free. Infinite baffle is like a box but infinitely large, separated from the playing area. In this case, the trunk is the infinitely large box, the cabin the playing area. For bass there needs to be two separate spaces. Trunk, sealed box, ported box. Really tweets are the only effective free air speakers.
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08-07-2016, 03:15 PM	#10
mathematics Captain 69 Rep 994 Posts Drives: 08 328i e93 alpine white Join Date: May 2009 Location: Queens, NY iTrader: (0)	Picture mounting a speaker to an infinitely wide and infinitely tall baffle so that the front and back of the speaker are not going to create destructive interference. That's the theory. In practice, that's it possible. In practice, it means make the enclosure as large as possible. There's a world of difference between a 1cubic foot enclosure and 25cubic foot enclosure. That's sealed vs infinite baffle. __________________ iPhone 6 Plus (iTunes library/iTunes radio/Waze, etc) to Airport Express via AirPlay. Toslink out of Airport Express to Helix P-Six DSP. PHD AF 1.C tweeters, PHD FB 4.1 midranges. Jehnert Door Cards and mid-bass'.
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08-07-2016, 03:28 PM	#11
Fundguy1 Major General 2032 Rep 8,339 Posts Drives: 335 e93 Join Date: Aug 2014 Location: Orlando, fl iTrader: (0)	A sub without this separation of one body of air on one side from s seconditions body of air on the other is virtually ineffective
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08-09-2016, 04:16 PM	#12
stylin20 Private First Class 27 Rep 189 Posts Drives: 2011 328xi Join Date: Dec 2009 Location: vancouver iTrader: (70)	Depends on what your sound tastes are. Mine is a nice tight bass with some rumble. But not your crazy ass shit you hear for miles. I like it to hit hard but crisp. I went with a 10" Dual voice coil Hertz that I wired to 2 ohms. Sealed enclosure Bassworx RP10 model I believe. It was suggested by the salesman and a Hertz Amp. Couldn't be happier. Those 8's are great for midbass, but if you want that bottom end. You need a sub. 12" will move more air and be louder, but not as "Tight". The box is just under 1 cubic Ft. So takes up virtually no room as I can still fit my golf clubs, shoes and a golf cart in the trunk. Good luck __________________ Thanks Stylin20
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