I'm running the 137 mids and 17MB woofers off an Alpine MRP F250 in bridged mode (100w per channel) This goes to the SPX 17MB crossover. The tweeters are running from a different amp.
The Processor is an Alpine PXA H701 with the cool RUX C701 display.
Current issues:
a) I'm experiencing some distortion on the MB woofers between around 80hZ. I'm thinking this is a result of my half-assed woofer enclosure. I'll be rebuilding it with a fiberglass one next week. I"m hoping this will solve the problem.
b) I'm not getting the "power" i want from the Midbass. When i first installed it, I got a nice powerful sound but tuned down the gains in an effort to reduce the "farting" distortion described above. I'm hoping i can bring the gains back up when the enclosure is re-built.
I used True RTA with pink noise to get the response as flat as i could, but until i fix the woofer enclosures, I'm going to be lacking in the midrange/midbass dept.
If it's farting, either its playing too low, you have too much power, or your gains are too high and your amp is pumping out distortion (probably this.)
many people run their gains way too damn high on their midbass because they hear the loud distortion as 'awesome midbass'
If it's farting, either its playing too low, you have too much power, or your gains are too high and your amp is pumping out distortion (probably this.)
many people run their gains way too damn high on their midbass because they hear the loud distortion as 'awesome midbass'
It only "farts" at a frequency range of about 15 Hz. Below or above that it's perfectly clean. I forgot the exact frequencies in question. I'll have to check.
So you have your front midbass playing at 15hz? Roughly a 6" cone?
Asking anything from that speaker below 63hz is asking for distortion and/or muddy performance. Most midbass' that size do best playing at 75-80hz and up. They just don't have the cone area to play below that generally (unless fully enclosed)
I am not that familiar with the voice coil and motor on that particular driver, but you may be getting into the mechanical limits as well /shrug
I am guessing that you have the passive handling the lowpass point only?
Ok makes more sense, you still may be asking for more than the 6.5" can deliver at the bottom end, and it likely clears up because the cone just can't move the air down that low.
One of the most interesting and educational things I did while getting my 3 way stage setup was to play around with different high pass and low pass points on the midbass to see how the midrange performance was affected. (often dramatically). And how the lower the midbass played the more muddy the sound became sooner (IE 63hz to 500hz was horrible, 63 to 350 was decent, 63 to 200 was great, ton more impact). Also I ran the same driver as high as 80hz to 5khz and backed it off incrementally to see how the midrange responded, and then snuck the high pass point up to say 350hz to see the difference it made without having to play any real "bass".
If you have the means and time I highly recommend an hour or so spent with familiar music playing with a midbass/midrange driver (1 driver) and lots of high pass and low pass points.
I recently discovered part of the problem may be the quality of the recordings. I was under the impression I was playing 320kbps when in fact it was 180 and sometines 128.
I've since discovered the wonderous joy of .flac files now giving me upwards of 1400kbps.
I'll try adjusting the LP front stage crossover points first before i tear into my doors.
Okay, don't ask what i was thinking cause i don't really know...
I had my front stage high pass crossover set at 63 hz with an 18dB slope
I had my subwoofer low pass crossover set at 200hz with a 12dB slope. I recently found out this is the very top of the subwoofers frequency response curve
For the time being (quick fix) i've made the following adjustments:
- set the front stage to 80hz HP
- set the Sub to 160 LP
For final adjustments, i'm going to raise the gains on the front midrange. I'm running about 30-40% gain at the moment trying to get rid of the woofer "farting" Now that I've adjusted the crossover, i can bring it back up to a healthier 50%+ Then do a complete system re-tune starting from scratch.
As far as I understand, tuning to the crossover points should be done first with pink noise to get the flattest response curve possible, then use the GEQ to smooth out the rest. Ideally, I should use the GEQ as a last resort to correct frequency response variations.
Question: How do you tune rear speakers for rear fill? I've just been lowering the higher frequencies on the rear channels for better staging.
Just remember, the gain is not a volume control. There is really only one right setting.
Aye. I had it perfect to start, but turned it down when I couldn't figure out why I was getting distortion. I didn't have the time then to sit down and figure it out so i left it alone until now.
....since i've managed to aquire a .flac version of pink floyd's concert "pulse" (which features my favorite version of "comfortably numb") I want to hear it in the highest quality possible....that means restoring my midbass.
160hz is asking a lot of a car audio sub. I would back that down to either 80hz or 63hz and see if that clears things up. IMO there is no reason to run your sub above 100hz at all, especially when you have a dedicated midbass driver in the system. That driver should work pretty well in the 80hz to 250hz range.
I would guess something similar to this chart should get you in the ballpark and you can fine tune from there:
Tweeters: As low as 4k as high as 7k depending upon your midrange performance. As low as 6db rolloff. 12db usually works pretty well utilizing "spaced" crossover points between the tweet and mid. Midrange: Depending upon the size of the cone, as low as 250hz and as high as 350hz for the HP point, and the LP point can be as high as the driver's performance warrants, but usually in the 4-5khz range Midbass: HP 63-80hz, LP as low as 200hz, and as high as 350hz depending upon the performance of the midrange. The lower the LP point, generally the better the impact Sub:100hz and down for almost every car audio application (pro audio is a whole different animal). With a dedicated midbass I would start at around 80hz and see if you can sneak it lower, possibly with a less steep slope to blend the sub/midbass together in the stage.
I would start: Sub 80hz 18db slope / Midbass 80hz 18db - 250hz 18db / Midrange 250hz 18db - 4khz 12db / Tweeters 5khz 12db. Mess around from there bro.
I was able to turn up the midrange gains to about 60% and got excellent clean power without any of the distortion. This will give me a good base line for fine tuning with the H701.
I'm going to check all my crossover points again as I don't think I adjusted them since i installed the active crossover. I was rushed installing it and all i was interested in was getting some sound out of the thing.
Thanks guys for your help. I'll post up pics of the RTA response curve when it's finished
okay that makes sense. I suppose it would be a good idea to make a crossover chart for all my drivers so I can see which speakers play what ranges and to prevent excessive gaps or overlaps.
This is what I mentioned in my posts with the "spaced" comment. You do not have to hardline crossover points to match. I have my DLS dome mids playing to 6khz with a 12db slope and my tweets picking up at 6.5k 12db slope.
Your sub and your midbass points as well as your midrange HP point are likely to be more toward 18 or 24db (if you have it) than they are to be 6 or 12db.
If you can find frequency response charts of your drivers they can give you a base line to work from and areas to look for for peaks and valleys in the system's response.
You can make headlights bro, you can handle this part easy
I reset the crossover points and aimed the Mic a little differently. I'm using the Mic that came with the PXA 701 for Auto Time-Correction.
I have a glass roof and mounted the mic with a suction cup holder originally designed for a radar detector. I faced the mic about 45 degrees off streight ahead depending on which channel I was working with trying to mimic the position of my ears.
I tuned the Eq with TrueRTA in 1/12 oct. mode. I set the generator for pink noise and tried to hit -40dB across the response range. Here were the results:
Front Left:
Front Left EQ settings:
Front Right:
Front Right EQ settings:
The rears were a little difficult to tune. The Right Rear has a passenger seat back in front of the tweeter and an amp rack in front of most othe woofer. The Left rear is....well pointless. They're good for rear fill, but that's all. In hindsight, i would have gone with less expensive drivers for the rear....or better placement options.
I also burned a new music DVD with ALL 320kbps MP3 files. I discovered that most of my music was 192 or less with some as low as 64kbps (back when i was using WMP ripper) The New music sounds significantly more clean and crisp. I LOVE it.
Kale/Fej: Thanks for you help
Sidenote: I've noticed certain artists seem to have MUCH better studio recording quality than others. Offhand, "hootie and the blowfish", some "Guns and roses" have supurb depth an clarity. I'll assume this is the work of expert sound engineers in the studio.
Corvette Store
Tedious Tuning (Active/passive 3-way front stage)
This is what I mentioned in my posts with the "spaced" comment. You do not have to hardline crossover points to match. I have my DLS dome mids playing to 6khz with a 12db slope and my tweets picking up at 6.5k 12db slope.
