Inverted subs
12-14-2007, 01:06 PM
#26
Less Weight = Better RX8
I think everyone is partially correct.
Car audio subwoofers designs fall into two camps. The first type relies on acoustic suspension of an enclosure for optimal performance. The second relies on the mechanical suspension of the woofer itself (Read infinite baffle) for optimal performance. In the early days of speaker design most woofers fell into infinite baffle type. Today, the majority of subwoofers rely on the enclosure for optimal performance.
Does it matter if you invert the woofer inside in an enclosure? The answer is it depends. Since we are talking about the enclosure type of speaker, we need to look further into their design.
Woofers optimized for larger size and vented (ported) enclosures generally speaking have more symmetrical suspensions systems and motor structure magnetic fields. Without getting into too much detail, it means the speaker works the same in both directions. So mechanically, it does not matter which way the speaker is positioned in the enclosure.
The advantage to inverting a woofer is cosmetic (personal preference) and enclosure volume. The amount of airspace a woofer consumes increases with the diameter. In other words, a 6” subwoofer will not take up too much space but a 15” woofer can take half to even a whole cubic foot of airspace. From a weight factor, an enclosure with the woofer inverted can result in an overall smaller enclosure that can reduce weight. (A good thing for RX8 owners). The disadvantage is increased mechanical noise. The spider and tinsel leads on the back side of the woofer does generate noise as part of its operation. Also, the air flow around the frame and through a vented pole piece of the woofer can also generate some noise. However, unless the woofer is particularly noisy, this is not a huge problem. Also it should be noted that some woofer designers believe the contiguous surface of the woofer will couple with the listening area better generating a more predictable performance. (You can classify this under hearing grass grow.)
Woofers optimized for small sealed enclosures may potentially have another situation. In small sealed enclosures, the airspace generates significantly more force over the woofer than larger enclosure. The backstroke of the woofer can require more effort than the front stroke. Some woofer designers take this into consideration in their woofer design. They make the magnetic field or suspension stronger in one direction to compensate for this effect. (Usually this means the magnetic field is increased on the opposite direction as the suspension increase). Only a handful of woofers are optimized in this way. Most are not. The irony is small sealed enclosures benefit most from inverting the magnet. Generally, it allows you to get the correct airspace in a less than optimal installation area. The negatives are basically similar to larger enclosures.
Bottom line. With the exception of increased mechanical noise, most of us cannot hear the different of a woofer mounted either way. It makes sense to invert the woofer when, it doesn’t fit the other way, or the enclosure you have is too small when to take into account the displacement of the woofer. Otherwise, a slight performance advantage must be given to a non-inverted woofer application.
PS. if you are looking for an enclosure calculator, below is a link to my website. There is also a link to an explanation of enclosures. For everyone’s information, I used to be the Product Manager for a big car audio company (I designed several speakers and subwoofers) as well as written many technical articles and product reviews for CarSound Magazine, Performance Auto and Sound Magazine and Automedia Magazine.
Box Calculator
Enclosure Design
Calculation Enclosure Volume
Car audio subwoofers designs fall into two camps. The first type relies on acoustic suspension of an enclosure for optimal performance. The second relies on the mechanical suspension of the woofer itself (Read infinite baffle) for optimal performance. In the early days of speaker design most woofers fell into infinite baffle type. Today, the majority of subwoofers rely on the enclosure for optimal performance.
Does it matter if you invert the woofer inside in an enclosure? The answer is it depends. Since we are talking about the enclosure type of speaker, we need to look further into their design.
Woofers optimized for larger size and vented (ported) enclosures generally speaking have more symmetrical suspensions systems and motor structure magnetic fields. Without getting into too much detail, it means the speaker works the same in both directions. So mechanically, it does not matter which way the speaker is positioned in the enclosure.
The advantage to inverting a woofer is cosmetic (personal preference) and enclosure volume. The amount of airspace a woofer consumes increases with the diameter. In other words, a 6” subwoofer will not take up too much space but a 15” woofer can take half to even a whole cubic foot of airspace. From a weight factor, an enclosure with the woofer inverted can result in an overall smaller enclosure that can reduce weight. (A good thing for RX8 owners). The disadvantage is increased mechanical noise. The spider and tinsel leads on the back side of the woofer does generate noise as part of its operation. Also, the air flow around the frame and through a vented pole piece of the woofer can also generate some noise. However, unless the woofer is particularly noisy, this is not a huge problem. Also it should be noted that some woofer designers believe the contiguous surface of the woofer will couple with the listening area better generating a more predictable performance. (You can classify this under hearing grass grow.)
Woofers optimized for small sealed enclosures may potentially have another situation. In small sealed enclosures, the airspace generates significantly more force over the woofer than larger enclosure. The backstroke of the woofer can require more effort than the front stroke. Some woofer designers take this into consideration in their woofer design. They make the magnetic field or suspension stronger in one direction to compensate for this effect. (Usually this means the magnetic field is increased on the opposite direction as the suspension increase). Only a handful of woofers are optimized in this way. Most are not. The irony is small sealed enclosures benefit most from inverting the magnet. Generally, it allows you to get the correct airspace in a less than optimal installation area. The negatives are basically similar to larger enclosures.
Bottom line. With the exception of increased mechanical noise, most of us cannot hear the different of a woofer mounted either way. It makes sense to invert the woofer when, it doesn’t fit the other way, or the enclosure you have is too small when to take into account the displacement of the woofer. Otherwise, a slight performance advantage must be given to a non-inverted woofer application.
PS. if you are looking for an enclosure calculator, below is a link to my website. There is also a link to an explanation of enclosures. For everyone’s information, I used to be the Product Manager for a big car audio company (I designed several speakers and subwoofers) as well as written many technical articles and product reviews for CarSound Magazine, Performance Auto and Sound Magazine and Automedia Magazine.
Box Calculator
Enclosure Design
Calculation Enclosure Volume
12-14-2007, 01:32 PM
#27
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PSonoda must be short for Paul Sonoda! Orion Team Extreme! We got drunk together at IASCA World Finals in Greenville I think around '97. (you, me, Jeff Green, and the girl you were dating from Eclipse) I think you were the one driving the van when you dropped me back off at the Embassy Suites that night in the rain. You skidded to a diagonal stop under the awning at the displeasure of everyone standing there! Any of this sound familiar?
12-14-2007, 01:48 PM
#29
PSonoda must be short for Paul Sonoda! Orion Team Extreme! We got drunk together at IASCA World Finals in Greenville I think around '97. (you, me, Jeff Green, and the girl you were dating from Eclipse) I think you were the one driving the van when you dropped me back off at the Embassy Suites that night in the rain. You skidded to a diagonal stop under the awning at the displeasure of everyone standing there! Any of this sound familiar?
I'm frankly surprised you even remember this much...
12-14-2007, 02:08 PM
#30
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That was a good time that night. After getting back to the hotel I went to a room party with Greg Davis and the guys from Kicker. There were alot of Kicker people at that hotel. we were in a room on about the 5th floor or so but we were being pretty civilized. In a room on the 9th floor (directly above us but a few floors up), some of the Kicker people thought it would be funny to throw a water balloon down into the lobby. Remember this is an Embassy Suites so the interior is open to the lobby. The water balloon these guys used however wasn't your average type. It was a trash bag that they filled up in the bathtub! They dropped this thing over the edge into the lobby below. I remember hearing a whooshing sound as it passed by the room followed by a crash and lots of laughter. I remember Greg saying "nothing good can come of this". He was right. The cops came and anyone out roaming the halls was kicked out of the hotel. There were over 100 people kicked out that night! I wasn't one of them. We turned out the lights and stayed quiet till it all died down.
Good times!
Good times!
12-14-2007, 02:17 PM
#31
Heh...at defcon this one year...we dumped god knows how many bottles of liquid dish detergent into the hot tub...suds as far as the eye could see...
then there was the "f**k shipley" thing...hundreds of little balsa planes with "f shipley" written on them and tossed en mass at shipley when he went up for his presentation...
the drunk dudes who got busted by the cops trying to flush a golden payphone down the toilet...
my $50 limo ride around the block...
and tons more...just in a single day...
Good times!
then there was the "f**k shipley" thing...hundreds of little balsa planes with "f shipley" written on them and tossed en mass at shipley when he went up for his presentation...
the drunk dudes who got busted by the cops trying to flush a golden payphone down the toilet...
my $50 limo ride around the block...
and tons more...just in a single day...
Good times!
12-14-2007, 02:25 PM
#32
Less Weight = Better RX8
PSonoda must be short for Paul Sonoda! Orion Team Extreme! We got drunk together at IASCA World Finals in Greenville I think around '97. (you, me, Jeff Green, and the girl you were dating from Eclipse) I think you were the one driving the van when you dropped me back off at the Embassy Suites that night in the rain. You skidded to a diagonal stop under the awning at the displeasure of everyone standing there! Any of this sound familiar?
12-14-2007, 02:29 PM
#33
12-14-2007, 04:07 PM
#36
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Wow... this thread is going in a whole different direction then I thought it would have...
Also... that would've been pretty funny if it wasn't the same guy you're talking about RG...
Also... that would've been pretty funny if it wasn't the same guy you're talking about RG...
12-14-2007, 09:54 PM
#39
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Air space is affected a little bit which is why this volume is usually stated with the thiele/small parameters. You need to take that into account when designing a box.
Theoretically they don't hit harder this way. However, there is one reason they might though. Many modern woofers have humongous magnets. When you mount these woofers in a box, it's not uncommon to have little room for air to get from the back of the cone, around the frame and magnet and into the box. The thicker the face of the box is, the worse this can get. You can radius the inside of the cutout to relieve this somewhat.
Yes you can do it but it isn't necessarily any louder. It's not impossible though. If a woofer is downfiring or upfiring other things come into play. You need to be sure the mass of the cone won't ultimately sag and affect performance. There is a calculator that allows you to figure out whether or not your woofer is a good candidate for either up or downfiring. I need to find it.
BTW: I worked as a custom car audio installer for 10 years. I've won both the IASCA and USAC WORLD finals and my final hoorah in the industry 6 years ago was building a show van for Rockford that went around the south for several years. I last saw it 3 years ago at Texas Heat Wave in Austin.
Theoretically they don't hit harder this way. However, there is one reason they might though. Many modern woofers have humongous magnets. When you mount these woofers in a box, it's not uncommon to have little room for air to get from the back of the cone, around the frame and magnet and into the box. The thicker the face of the box is, the worse this can get. You can radius the inside of the cutout to relieve this somewhat.
Yes you can do it but it isn't necessarily any louder. It's not impossible though. If a woofer is downfiring or upfiring other things come into play. You need to be sure the mass of the cone won't ultimately sag and affect performance. There is a calculator that allows you to figure out whether or not your woofer is a good candidate for either up or downfiring. I need to find it.
BTW: I worked as a custom car audio installer for 10 years. I've won both the IASCA and USAC WORLD finals and my final hoorah in the industry 6 years ago was building a show van for Rockford that went around the south for several years. I last saw it 3 years ago at Texas Heat Wave in Austin.
12-15-2007, 12:04 AM
#40
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Yeah but his wild days are over...RG's settling down! 
Back to on topic: I don't like the look of inverted or the fact that you have bared live wires held by just a binding post in your trunk. Then again, I probably feel this way because I have a MMATS D300HC - grounding ~40VDC does not sound like a good idea to me.
Back to on topic: I don't like the look of inverted or the fact that you have bared live wires held by just a binding post in your trunk. Then again, I probably feel this way because I have a MMATS D300HC - grounding ~40VDC does not sound like a good idea to me.
12-15-2007, 04:04 PM
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Ha.. a friend of mine actually owns, or I should say use to own, his own little audio shop, and I went to see how he was doing and maybe to see what he would say. Well, long story short, he gave me a free sub and amp.
Granted they're REALLY old stuff... but hey I'll take free anytime.
The sub is an Infinity Kappa 100.1se
The amp is actually super old, an Autotek
What I think is funny is that these are both brand spanking new! He had a bunch of them. Also, remember back in the day Super Blues... the subs that everyone had because they were so cheap... and no matter how much power you put to them, they wouldn't blow (well at least for me).. Yeah, he had a bunch of those too... brand new.
I'll use the sub till after Christmas then go buy a new one, and I may hook up the amp just to see if it'll bump it... but I just might give it to a buddy of mine who needs an amp for his 6x9's.
Granted they're REALLY old stuff... but hey I'll take free anytime.
The sub is an Infinity Kappa 100.1se
The amp is actually super old, an Autotek
What I think is funny is that these are both brand spanking new! He had a bunch of them. Also, remember back in the day Super Blues... the subs that everyone had because they were so cheap... and no matter how much power you put to them, they wouldn't blow (well at least for me).. Yeah, he had a bunch of those too... brand new.
I'll use the sub till after Christmas then go buy a new one, and I may hook up the amp just to see if it'll bump it... but I just might give it to a buddy of mine who needs an amp for his 6x9's.
12-17-2007, 12:35 PM
#42
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Paul, I spoke to Joanna Duncan and Art Belvin this weekend. They both say hi. Art thanks you for all the help back then with the Concept 97-1 and the support you gave us.
Back to our regularly scheduled program...
Back to our regularly scheduled program...
12-18-2007, 04:38 PM
#43
Less Weight = Better RX8
There are not any real choices for speakers for the RX8. It is quite an odd design with the 8" speakers in the front and 6x9 in the rear. I have even thought about designing some speakers specifically for the RX8. All the subwoofer solutions I have seen take up so much room and weight. We should be looking for ways to cut weight from the car not add it.
Do you think people would be interested in some high performance subwoofers that fit in the 6x9 location in the rear?
12-18-2007, 09:31 PM
#45
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Perhaps something like these?
http://www.partsexpress.com/pe/showd...number=264-837
http://www.partsexpress.com/pe/showd...number=264-864
http://www.partsexpress.com/pe/showd...number=264-837
http://www.partsexpress.com/pe/showd...number=264-864
12-19-2007, 07:49 AM
#46
Less Weight = Better RX8
I saw the speakers from TangBang. (Sounds like an asian porno film)
I was thinking more like a high excursion 6x9. Stamped metal frame for weight. I do have a set of Genesis 6x9 subwoofers for evaluation. I was original planning to do this or a single JL8w7 Through the Ski hole. Any thoughts?
I was thinking more like a high excursion 6x9. Stamped metal frame for weight. I do have a set of Genesis 6x9 subwoofers for evaluation. I was original planning to do this or a single JL8w7 Through the Ski hole. Any thoughts?
12-19-2007, 08:29 AM
#47
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A single 8" in the center there would be nice. It wouldn't be too hard to build an enclosure that could just easily bolt in between the seats. Something like a JL Stealthbox if they had ever made one for the car.
12-19-2007, 11:50 AM
#48
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That's what I am making for my car. An eclosure to fit in the passthrough. I don't know what the stealthbox is, but I'll post mine when I'm done with it.
I work from 8 to 7, then I'm at the gym from 730 till about 1030... I started on it Sunday night, and I've been coming home and working on it for about half an hour a night.. cause I still need to eat, and shower, and get ready for the next day. Hopefully I'll be able to finish it this weekend.
I work from 8 to 7, then I'm at the gym from 730 till about 1030... I started on it Sunday night, and I've been coming home and working on it for about half an hour a night.. cause I still need to eat, and shower, and get ready for the next day. Hopefully I'll be able to finish it this weekend.
12-19-2007, 12:00 PM
#49
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"Focal 13KS" FTW!
That's what they put in high end Porsche installs.
If you have lots of money then "Focal 13WS"...Utopia line.
Both are 5" subwoofers and both are compact and high quality (you stated that it was what you were looking for).
Not sure what inverted mounting implications are for SQ but I know that Focal magnets look amazing so it's worth a shot just for the bling factor.
Imagine two of these in the center area!!!!
http://www.focal-america.com/
That's what they put in high end Porsche installs.
If you have lots of money then "Focal 13WS"...Utopia line.
Both are 5" subwoofers and both are compact and high quality (you stated that it was what you were looking for).
Not sure what inverted mounting implications are for SQ but I know that Focal magnets look amazing so it's worth a shot just for the bling factor.
Imagine two of these in the center area!!!!
http://www.focal-america.com/
12-19-2007, 12:11 PM
#50
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When I worked at Expressive Audio several years ago, we had 2 cars that competed in the Expert class in consecutive years as each other. They were called Reaper (which won) and Reaper II (2nd place). The Reaper was a Dodge Intrepid and the Reaper II was a PT Cruiser (Piece of Trash Cruiser). The Intrepid had 4-5" subs in the top of the dash in sealed enclosures. Two on each side. The PT had 8 of them. 4 under each seat in bandpass boxes. They worked out very well and sounded very nice. They were only used for sound quality as they just don't put out enough for spl purposes. Yes our primary sound quality sub setup was a bandpass!!! Road noise vs sitting still in a judging lane are two totally different things. I wouldn't personally use them as the primary subs in the RX-8 unless you plan to use 4 of them. You just can't change the laws of physics. Low frequencies need to move air and to get loud enough to overcome road noise means a fair amount of air will need to be moved. It would take several 5" subs to do this. Even if you had the total cone area with multiple 5" subs, you still lack the excursion capabilities of a larger sub.