| krammer |
Well I finally got around to trying a few things with the stock subwoofer or woofer or whatever it is.
I knew that I wanted to put in a low-pass filter. Having a full range of sounds trying to be pushed through the sub is not a good thing. After reading several posts concerning speaker upgrades I thought that I might need bass blockers on the door speakers. I ordered two pair from Crutchfield with a 150 Hz cutoff frequency. I therefore wanted my low-pass filter to have a cutoff frequency of 150 Hz. I went to Loudspeakers 101 and used a second order Butterworth filter with a 2 ohm impedance. After checking the Parts Express web site, the closest values they had were a 400 uF capacitor and a 3.3 mH inductor which leads to a 140 Hz cutoff frequency. Ideally, without the bass blockers, I'd want the cutoff frequency for the sub to be around 100 Hz, but I figured this should be good enough. As it turned out, the Kenwood eXcelon (in the front doors) and Infinity (in the rear doors) combination did not need the bass blockers, but I had already had the filter parts. (Door install info and pictures here and here.) |
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| krammer |
| I had also ordered 2 one pound boxes of poly fiber fill from Crutchfield to fill in the area behind the sub in order to try to reduce as much of the booming sound as possible. This seemed like the right amount as it filled the area nicely. I put as much in toward the front, back, top and bottom as I could as well as the area immediately behind the sub. I also stuffed some in the hole that the sub's tab fits into. |
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| krammer |
| I first soldered the capacitor across the input terminals on the sub. To connect the inductor, which is constructed of foil, I soldered a female connector onto one end. I had extra connectors from my door speaker install. The connector was a little too small, but I was able to strech it with a pair of needle nose pliers. On the other end I folded the foil lead to fashion a male connector. Both gave me a nice tight fit when I put the inductor in-line with the positive speaker wire and the input connector on the sub. I used electrical tape to insulate the foil leads. The inductor is rather large and heavy, so I wanted to support it. I put a piece of foam, for insulation purposes, between the inductor and one of the support structures on the sub and used a cable tie to hold it in place. |
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| krammer |
No more vocals coming from the sub. The booming also seems to be greatly reduced, maybe eliminated. It still doesn't have the punch of a true sub, one look at its constuction would tell you why, but after these modifications, it seems to be putting out a decent sound.
While the sound of the bass is greatly improved with the speaker upgrades and sub modifications that have been done, I still think that a true subwoofer is needed here. As soon as I find a good deal on a Polk GNX 10DVC (can be wired for 2 ohms and has a needed shallow mounting depth) and find a way to make an install spacer, I'll be getting one. The mods detailed here won't go to waste as the fiber fill and filter will still be needed and used for any sub that will go in here. |
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| edmondsmdx |
Krammer:
Thanks again for all of your patience and pix on the door installs. I was finally in town long enough to get it done this week- I copied your "final" install w/Excelons in front and Infinities in back...sounds great.
Do you (or anyone else) have instructions on disengaging the Twiddler? Did you do this? My next "attempt" will be to disengage the stock door tweeters, but I'm unsure about the twiddler.
I did a search on the forums, but came up with very little.
Thanks again for the advice. This forum is great! |
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| TheyCallMeBruce |
quote:
Originally posted by krammer
I had also ordered 2 one pound boxes of poly fiber fill from Crutchfield to fill in the area behind the sub in order to try to reduce as much of the booming sound as possible. This seemed like the right amount as it filled the area nicely. I put as much in toward the front, back, top and bottom as I could as well as the area immediately behind the sub. I also stuffed some in the hole that the sub's tab fits into.
I'm interested in knowing what the working theory is in reducing "boominess" by adding sound pressure dampening material in a first order infinite baffle design. Regardless of the fact that neither enclosure volume, nor venting characteristics can be calculated, or even estimated, with any certainty, I always thought the these materials were only used in sealed designs. After checking, the few speaker building catalogs I have on hand seem to reference poly fill exclusively for sealed designs as well. Where did you get the idea to do this?
Just curious, in case I've missed out on anything new since I've been out of autosound for a while now.
bruce |
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| xyzzy |
I've heard the same thing before (fill only in sealed enclosures), but I can tell you that I have seen and even owned ported speakers with fill in them (I currently have a set of Klipsch speakers that do this). From what I understand, the fill is just used to cancel any unwanted resonance or standing waves. Why they don't recommend this for ported designs I'm not sure since "unwanted resonance" could take on many forms.
Chris |
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| DaleB |
| Some question as to how much it helps, but apparently doesn't hurt..in most cases. |
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| krammer |
edmondsmdx:
To get at the twiddler, remove the cover by pushing it towards the front of the MDX and pull the back of it downward. The twiddler is held in place by four very tight screws that strip easily, match the philips bit to the screws carefully. I disconnected the connector and screwed the twiddler back in place. The cover should go back in by placing the three hooks in the front in first and then pushing the cover up and sliding it to the back while continuing to push up. It seemed much more difficult to reinstall than it did to remove.
bruce:
I got the idea for the fiber fill from somewhere on this forum. It sounded like a fairly inexpensive and easy modification to help improve the sound. I'm not sure of the acoustical theory behind this, I guess I should sit down and put my physics/engineering background to work on it (the old brain is getting a little rusty teaching people how to use excel, word, etc.)
Unfortunately, I didn't really use the scientific method in employing my fixes to the MDX's sound system. There was a good reduction in the booming after just replacing the door speakers. Some that may be a resonance in the front door cavity as the bass was much more emphasized by the Infinity's when they were in the front door. The Kenwood's don't have the bass response that the Infinitys have and the Infinitys sound much smoother in the rear doors than the front. The new speakers sound as if they are louder than the stock ones, so at the same apparent sound level, the volume level on the head unit would be less and therefore not pushing the subwoofer as hard. To tell you the truth, I'm not sure I can even hear the subwoofer from the drivers seat now! I'd like to get a more efficient driver back there.
When I took the subwoofer out, I did both the fiber fill and the low pass filter installs at the same time. Either one, or both, and/or the door speakers could be contributing to the better sound that I'm now getting. It still not a true subwoofer punch that I would like, but at least it's not that awful booming that even my wife (who readily admits that she's as good as tone deaf) would cringe at every time it would come through. |
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| DaleB |
I am using the 4 ohm Polk sub with a 100hz filter (ala partsexpress.com), and for the most part I am very pleased. I cheaped out with bypass caps on the Infinitys (150hz) but I am sure I am hearing much lower when the music requires it, but no boomy sound.
Of course, you should not be able to 'localize' the sub that easily, but in a car environment, less than stellar results can be expected depending on the interior design and speaker placement.
I am contmeplating Boston upgrades, possibly components in the front doors.
Not sure if upgrading the rear doors will really help that much for those sitting in the front.
Kind of cost-effective not to upgrade for 2nd and 3rd row passengers, who are not regulars anyway. |
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| TheyCallMeBruce |
quote:
Originally posted by DaleB
I am contmeplating Boston upgrades, possibly components in the front doors.
Not sure if upgrading the rear doors will really help that much for those sitting in the front.
Kind of cost-effective not to upgrade for 2nd and 3rd row passengers, who are not regulars anyway.
Dale;
I think this is a great idea. Fronts are all that really matters (aside from the sub). The music should be coming from in front of you anyhow, not behind, so you can just fade forward about a third and allow the rears to function as true rear-fill speakers, instead of competing for the soundstage. The head rests block direct passage of rear sound waves to the ears of both front positions and cuts down on the effect of the most important tones, the upper-mids and highs.
The only drawback is that once you move to high-end speakers, you will never be able to settle for standard units in any future vehicle, or even your other family vehicles. |
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| krammer |
DaleB:
I should be able to localize some sounds from the sub as the cutoff frequency is 150 Hz. To me it sounds as if most of the bass is coming from the rear Infinity's. I think that the stock sub is so inefficient that it's overpowered by the other speakers. Did you notice a big difference with the 4 ohm Polk over the stock sub? I'm thinking about getting the DVC version of the Polk so I can wire it for 2 ohms. Any suggestions for an easy way to mock up a spacer plate? I saw the pictures you posted of yours. You should sell some on the side! :D
Bruce:
How important is setting up a soundstage in an auto environment? With the speaker locations and related seating postions, I wouldn't think that it would be of great importance. I have the fade set in the middle. Most of the sound is coming from the front Kenwoods, but I am able to hear the Infinity's as well, most noticably the lows and the upper highs. I feel as if I'm getting better sound this way.
You're comments are right on about moving to higher-end speakers. I still miss the MB Quartz that I had in my old Porsche and am dying to rip out the stock speakers in my wife's Accord. |
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| renov8r |
I'll jump in here, but I'm eager to see Bruce's ideas too.
I think that when you get a vehicle pretty quiet or only have two occupants the whole notion of rear speakers is pretty pointless. In a large or noisy vehicle you need the rears for the passengers to hear anything. Auto sound, with rare exceptions, is just stereo. Would you put loud speakers BEHIND you in your home? Of course not. Unfortuantely the physical limitations of vehicles make it very hard to fit a bass driver anywhere other the rear of the vehicle. Doing so pretty much requires that ONLY low frequency sounds be sent to that driver. That is NOT what Acura has choosen to do. The marketing genusises at Bose can get away with just an acoustic resonance tube on the Bose Wave because it is an "all-in-one" with the impossibility of putting drivers anywhere but in one cabinet. The Bose home theater products do however rely on crossovers, something sorely lacking in the MDX Touring upgrade! :3:
There is a very poor sense of stereo in the MDX. I have heard better seperation and imaging from table radios that cost far less than $200 -- http://www.tivoliaudio.com/pM2TPE.htm While this radio does beat MOST vehicles, the gap between the MDX and say a Jetta is pathetic!
Upgrading the drivers alone helps signficantly tighten up the bass and even helps the midrange a bit and makes the highs slightly less strained. Unfortunately to improve imaging would require a much more serious investment in crossovers and external amp. To properly use external amps with the stock head unit, by extracting low level signal, is pretty costly.
quote:
Originally posted by krammer
DaleB:
I should be able to localize some sounds from the sub as the cutoff frequency is 150 Hz. To me it sounds as if most of the bass is coming from the rear Infinity's. I think that the stock sub is so inefficient that it's overpowered by the other speakers. Did you notice a big difference with the 4 ohm Polk over the stock sub? I'm thinking about getting the DVC version of the Polk so I can wire it for 2 ohms. Any suggestions for an easy way to mock up a spacer plate? I saw the pictures you posted of yours. You should sell some on the side! :D
Bruce:
How important is setting up a soundstage in an auto environment? With the speaker locations and related seating postions, I wouldn't think that it would be of great importance. I have the fade set in the middle. Most of the sound is coming from the front Kenwoods, but I am able to hear the Infinity's as well, most noticably the lows and the upper highs. I feel as if I'm getting better sound this way.
You're comments are right on about moving to higher-end speakers. I still miss the MB Quartz that I had in my old Porsche and am dying to rip out the stock speakers in my wife's Accord.
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| DaleB |
quote:
Originally posted by krammer
DaleB:
I should be able to localize some sounds from the sub as the cutoff frequency is 150 Hz. To me it sounds as if most of the bass is coming from the rear Infinity's. I think that the stock sub is so inefficient that it's overpowered by the other speakers. Did you notice a big difference with the 4 ohm Polk over the stock sub? I'm thinking about getting the DVC version of the Polk so I can wire it for 2 ohms. Any suggestions for an easy way to mock up a spacer plate? I saw the pictures you posted of yours. You should sell some on the side! :D
In all honesty, I can not hear a big difference. The filter does keep the other audio out of the bass which is always a good thing.
Bass being basically non-directional, the sub should work ok. But location is important for good bass coupling. And the environment of the MDX is an uknown in that regards. The sub can use a good amp with it and that might make the most difference. I might do that downstream. I believe mushman mentioned the 2 ohm sub made more of difference.
The spacers were bit of a pain, even for another shop to make up. But then you only need to do it once.
I am close to replacing the front door speakers with some recommended Bostons. I will let you know the outcome. |
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| TheyCallMeBruce |
quote:
Originally posted by krammer
Bruce:
How important is setting up a soundstage in an auto environment? With the speaker locations and related seating postions, I wouldn't think that it would be of great importance. I have the fade set in the middle. Most of the sound is coming from the front Kenwoods, but I am able to hear the Infinity's as well, most noticably the lows and the upper highs. I feel as if I'm getting better sound this way.
Soundstage;
front vs. rear. Let me put it this way. My most ambitious and successful project did not have any rear mids or tweeters, not even a rear fill speaker. A few installers and audio enthusiasts who have auditioned the system never even noticed that there were no rear midrange speakers, but did give positive feedback on various aspects of sound quality.
You want to feel as though the musicians are in front of you, not to your side, or behind you. There is no purpose in using rear speakers other than out of consideration for your passengers. Who usually don't want it as loud as front passengers anyway.
Imaging & stereo effect;
sucks in the MDX because of the positioning and poor aiming of the tweeters. The tweeters should be at the farthest part of the corner of the dash as possible. Because the midrange woofer should be an equivalent distance from your ears as the tweeters are, this requires that the midrange be located at the forward-botton edge of the door. Notice that in the MDX, the front door speaker is placed mid-level on the door panel, and therefore, the tweeter is located in the triangular window pod, instead of on the dash. Because the tweeters are not very far forward of you, they are not able to be properly "cross-fired." This term refers to the left tweeter being aimed directly at the right passenger's head, and the right tweeter aimed at the driver's head. When the tweeters are far forward enough, this cross-firing creates a perception of a distinct a left, middle and right side musical source. And, because the midrange speakers are equi-distant from the tweeters, there is a singular image reproduction between the tweeter and midrange, even though they may be far apart from each other. Properly arranged, blindfolded, you should not be able to tell that there is a separate tweeter and midrange, nor be able to pinpoint their locations. MDX tweeters are neither angled nor positioned for cross-firing. Hence, the lack of spatial realism.
Example of what I mean:
I'm very impressed with my wife's RX300's standard audio. The speakers aren't particulary high quality, but they are positioned and aimed for optimum effect. Visually, its disruptive that the tweeters are "out there" and "in your face," but wow the musical delivery is so excellent. That little 6" boxed subwoofer underneath the front seat is really neat too because even though it doesn't produce a lot of bass, per se, its in a location that enhances its presence and makes you think there is sufficient bass. |
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| XStatic |
| Wouldn't it be better to filter on the input of the sub amp so the amp isn't wasting energy on frequencies not needed? |
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| DaleB |
quote:
Originally posted by XStatic
Wouldn't it be better to filter on the input of the sub amp so the amp isn't wasting energy on frequencies not needed?
It probably would be. Considering the relatively benign changes discussed in this thread, I doubt if it would do anything remarkable.
If you are talking about a 'good' amp and driver combo, yes that would be another thing altogether. Some amps have an adjustable crossover built-in I think, or you can certainly add an adjustable and/or fixed one on the input and then you have truly taken care of 'bass management'. |
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