Ported Doors
07-27-2005, 04:48 PM
#11
following up from the other post, with that .6 cubes was there any tests done with sealed enclosures? and is that all the space you could get behind the panel, or is that what the driver needs?
thanks, Mark
thanks, Mark
07-28-2005, 04:04 AM
#14
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The SQ with sealed boxes is quite nice, but the power handling , and efficiency drop off a lot, especially in the 60- 90 Hz range.
Part 3 of the write up on the doors:
The hardest thing to achieve in an SQ system is the bass "up front",,,,since the subs are always in the rear, and most front speakers can't play too low. To get low bass, you have to move a LOT of air. Either with a large driver, or a small driver with a very large excursion, and a ton of power. Most 6" door speakers will bottom out way before they get loud at low frequencies.
There are two types of power handling with any speaker....thermal, and mechanical. Thermal power is the amount of heat a given speaker can stand before it melts or burns. This is the rating used by the manufacterers. If your sub says 500 watts, that means it can get as hot as five 100 watt light bulbs before the voice coil will melt.
Mechanical power handling is a variable number that depends on the note being played, and will change from one box size and type, to another. The manufactures can't publish this number, because it depends on too many variables.
As the notes get lower, the cone has to move farther, and at some point the voice coil will hit the end of the magnet, or some part of the suspension will fail.
For example that "500 watt" sub, may only handle 75 watts at 20 hz, in a box of "x" cubic feet.
Ported boxes behave differently. Around the tuning frequency, the extreme pressure in the box actually stops the cone from moving. Almost all the sound is coming from the port at those notes.This allows the woofer to play to it's full thermal handling ability, rather than being limited mechanically.
Below the tuning frequency, the mechanical power handling drops off to a very low number, so it's important to have a filter to prevent low notes from getting to the driver. The best sound quality in a ported system is "usually" at or above the resonant frequency of the driver, which in the case of the Powerplant 6's is 64Hz, so that's where I tuned em, and crossed em over.
Most door speakers with a bit of power going to them are basically "flapping in the breeze" so to speak. Because the door is not pressurized, the woofers quickly run out of room and "pluck" unless the bass is filtered out below around 100 hz.
The door panels on the Cav, being ported and tuned low, can handle about 500 watts per door down to 60 hz. and they hardly move at all at that note.
We had them playing by themselves one Sunday, just to break em in, and people from a block away came by the shop and asked us to turn it down!!!
If you listen carefully to the bass in the Cav, not just to the volume, but from where it appears to come, it is much more "up front" than most cars. Most people don't care, as long as the bass is loud, but in a competition, there are points lost if the sound stage is not in front of the judge at all frequencies.
Part 3 of the write up on the doors:
The hardest thing to achieve in an SQ system is the bass "up front",,,,since the subs are always in the rear, and most front speakers can't play too low. To get low bass, you have to move a LOT of air. Either with a large driver, or a small driver with a very large excursion, and a ton of power. Most 6" door speakers will bottom out way before they get loud at low frequencies.
There are two types of power handling with any speaker....thermal, and mechanical. Thermal power is the amount of heat a given speaker can stand before it melts or burns. This is the rating used by the manufacterers. If your sub says 500 watts, that means it can get as hot as five 100 watt light bulbs before the voice coil will melt.
Mechanical power handling is a variable number that depends on the note being played, and will change from one box size and type, to another. The manufactures can't publish this number, because it depends on too many variables.
As the notes get lower, the cone has to move farther, and at some point the voice coil will hit the end of the magnet, or some part of the suspension will fail.
For example that "500 watt" sub, may only handle 75 watts at 20 hz, in a box of "x" cubic feet.
Ported boxes behave differently. Around the tuning frequency, the extreme pressure in the box actually stops the cone from moving. Almost all the sound is coming from the port at those notes.This allows the woofer to play to it's full thermal handling ability, rather than being limited mechanically.
Below the tuning frequency, the mechanical power handling drops off to a very low number, so it's important to have a filter to prevent low notes from getting to the driver. The best sound quality in a ported system is "usually" at or above the resonant frequency of the driver, which in the case of the Powerplant 6's is 64Hz, so that's where I tuned em, and crossed em over.
Most door speakers with a bit of power going to them are basically "flapping in the breeze" so to speak. Because the door is not pressurized, the woofers quickly run out of room and "pluck" unless the bass is filtered out below around 100 hz.
The door panels on the Cav, being ported and tuned low, can handle about 500 watts per door down to 60 hz. and they hardly move at all at that note.
We had them playing by themselves one Sunday, just to break em in, and people from a block away came by the shop and asked us to turn it down!!!
If you listen carefully to the bass in the Cav, not just to the volume, but from where it appears to come, it is much more "up front" than most cars. Most people don't care, as long as the bass is loud, but in a competition, there are points lost if the sound stage is not in front of the judge at all frequencies.
07-28-2005, 04:32 AM
#15
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This system was designed to use all Powerplant products, because that's what the customer wanted. With the exception of the X-Box, everything , from the deck to the subs is Fusion. With that in mind, I tried to design a system that could get the best SQ, at the highest SPL possible, within the limits of the products.
I have a meter on the way soon, and i'll be able to see just how loud this car goes, but I'm confident that the output in the mid-bass is considerably higher than any comparable sealed or IB type door.
There are cars with 4 or more drivers per door, that I'm sure would get as loud, but I'm not sure they'd have the same control and impact at the volume I'm getting. And in "sound per dollars" worth of components....The MSL of the whole front stage is well under $500, and we discarded 2 sets of passive crossovers!
The cars with subs up front will surely beat us in that category, especially since most true SQ designers would use the best products available for the design.
I have a meter on the way soon, and i'll be able to see just how loud this car goes, but I'm confident that the output in the mid-bass is considerably higher than any comparable sealed or IB type door.
There are cars with 4 or more drivers per door, that I'm sure would get as loud, but I'm not sure they'd have the same control and impact at the volume I'm getting. And in "sound per dollars" worth of components....The MSL of the whole front stage is well under $500, and we discarded 2 sets of passive crossovers!
The cars with subs up front will surely beat us in that category, especially since most true SQ designers would use the best products available for the design.
08-03-2005, 10:08 AM
#17
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Join Date: Aug 2003
Posts: 73
Great post. Very informative. Given the detailed descriptions and the pics, it should be filed for reference purposes.
I have been reasonably satisfied with the midbass in my Miata, but I now see the true solution for my search for ultimate midbass. I could definitely implement this kind of design.
You note that this is not your best SQ system. Is that due to the limits of the drivers themselves? Any other reason for the statement?
I have been reasonably satisfied with the midbass in my Miata, but I now see the true solution for my search for ultimate midbass. I could definitely implement this kind of design.
You note that this is not your best SQ system. Is that due to the limits of the drivers themselves? Any other reason for the statement?
08-03-2005, 01:18 PM
#18
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Join Date: Oct 2004
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There were several limiting factors. As far as the speakers, I think a single set, with more of a "point source" type install would be better. No way a single set could produce the SPL we're getting tho, so that was one trade off.
While the Fusions are quite impressive, especially considering that they are in the middle of the line-up, there are more accurate drivers available, albeit at a much higher price.
This system was set up to produce a lot of SPL, and it does, but for a pure SQ design, I would have traded off a lot of decibels for better imaging, transient response, detail, etc. Not saying this one is bad, in fact it's quite nice to listen to, but I have built a few cars that edged it out using IASCA rules.
While the Fusions are quite impressive, especially considering that they are in the middle of the line-up, there are more accurate drivers available, albeit at a much higher price.
This system was set up to produce a lot of SPL, and it does, but for a pure SQ design, I would have traded off a lot of decibels for better imaging, transient response, detail, etc. Not saying this one is bad, in fact it's quite nice to listen to, but I have built a few cars that edged it out using IASCA rules.
08-04-2005, 04:16 PM
#19
Car Trek, I am interested to know why you just didn't glass the whole panel from scratch... was it to save time, or that you liked the shape etc... I can't see the reason being that it would cost more money, given the caliber of the install itself.
Mark
Mark
08-04-2005, 06:00 PM
#20
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I was a bit concerned about having to form the top half which has it's own share of challenges.
for one, getting the part that clips into the top of the door right would have been tough....need a very straight, very thin lip there....and the extra work to mould around the door handle, made it easier to just do the bottom half.
The clips at the top of a Cavalier door hold it very securely, and that type of engineering is hard to beat.
I suppose from a technical viewpiont, a completely solid 'glass panel would have given a bit better baffle, perhaps audible, and maybe nicer looking, but a lot more time consuming than joining the two parts.
In retrospect, I think a brighter colour for the glass parts would have turned more heads...maybe a lime Fusion green. The way it is now, it's a bit subtle. I like it personally, but it doesnt jump out and make you see it all right away.
The customer is very happy with it, tho, and that's what counts the most.
On another note, two of the door speakers have come apart....the intense heat at the coils melted the cone/dustcap, and the cone seperated from the coils....I wasn't there when it happened, but he was playing it very hard.
The coils themselves are not siezed in the gap...in fact they still play fine....proof enough for me that the thermal limit, not mechanical, is the rule with this type of enclosure.
I was playing a bit with the new (old) meter today, and the front end puts out nearly 130 without the subs....I need to have the meter calibrated tho, so I could be off by 6 or 7, but it's still LOUD.
I'm going to try running the doors with the amp straight from the deck, and use just the high pass, and subsonic filter in the amp. I suspect it will be a bit cleaner, and louder without the crossover in the path.
Have a weekend long show tomorrow, so I'll have some time to play with it, and see what it can do with some tweakin.
for one, getting the part that clips into the top of the door right would have been tough....need a very straight, very thin lip there....and the extra work to mould around the door handle, made it easier to just do the bottom half.
The clips at the top of a Cavalier door hold it very securely, and that type of engineering is hard to beat.
I suppose from a technical viewpiont, a completely solid 'glass panel would have given a bit better baffle, perhaps audible, and maybe nicer looking, but a lot more time consuming than joining the two parts.
In retrospect, I think a brighter colour for the glass parts would have turned more heads...maybe a lime Fusion green. The way it is now, it's a bit subtle. I like it personally, but it doesnt jump out and make you see it all right away.
The customer is very happy with it, tho, and that's what counts the most.
On another note, two of the door speakers have come apart....the intense heat at the coils melted the cone/dustcap, and the cone seperated from the coils....I wasn't there when it happened, but he was playing it very hard.
The coils themselves are not siezed in the gap...in fact they still play fine....proof enough for me that the thermal limit, not mechanical, is the rule with this type of enclosure.
I was playing a bit with the new (old) meter today, and the front end puts out nearly 130 without the subs....I need to have the meter calibrated tho, so I could be off by 6 or 7, but it's still LOUD.
I'm going to try running the doors with the amp straight from the deck, and use just the high pass, and subsonic filter in the amp. I suspect it will be a bit cleaner, and louder without the crossover in the path.
Have a weekend long show tomorrow, so I'll have some time to play with it, and see what it can do with some tweakin.
