No, -5 is not that odd. Different speakers in different vehicles create a variety of unique circumstances. So no big deal.
What you could try is cutting it 3dB like you said, but maybe try shifting the center freq to 6K and see how it sounds.
You may also want to bring the tweeter back up from the -4 to maybe -2 or 0 and then try adjusting the 4K or 6K center freq. There are a lot of combinations you can try so you'll just have to experiment to find the right combination.
Hope it's not too late to reply to this thread! I really got a lot out of all the replies and spent about two hours in my car last night doing some playing. It's a '93 Mitsubishi 3000GT with a Pioneer DEH-P6500 head unit, basic Alpine speakers front and rear (not sure of the model), and an Infinity Basslink (which I just installed, which is why I'm doing so much research). A modest system I realize, but I'm not looking for a world-beater; just a good-sounding system. Speaking of, my starting point before reading this thread was with all the EQ and loudness controls maxed out cuz I thought it sounded best that way! It sounded okay and wasn't distorting, but I was getting some decent hiss on the higher frequencies for sure. Also, this put my volume control on the head unit at number 10 (out of maybe 50)...
Anyway, I ran a test CD that I've had since like 1990 in my car and used my Radio Shack digital SPL meter to take some measurements. I was really surprised by what I found. First, I zeroed out all the EQ settings, turned off the loudness control, set the sub crossover on my HU to 80 Hz (with the crossover on the sub itself at 125 Hz to basically defeat it), the HPF on the HU to 80 Hz, and the subwoofer gain at it's midpoint. Before measuring I listened to some music this way and it sounded pretty decent... maybe lacking a little treble...
So I place the meter on a tripod on the drivers seat and I crawl in the back and start playing tones. I used the 1000 Hz tone to set the volume to register 80 dB, then started with 30 Hz. 30 Hz was around 90 dB, 40 Hz was like 95 dB, and 50 Hz was 99 dB! From there things went back closer to normal, between 75 and 85 dB up until 10k where things quickly dropped.
One thing I noticed was that the readings above 1000 Hz would change WILDLY depending on where my head was! If I moved my head just a few inches the dB would go up or down by 5 dB! At that point I re-oriented the meter so I could read the display from outside the car through the drivers side window. I got out of the car and re-measured. Again, the bass was super high, then things leveled out (although with a pretty good dip around 500-800 Hz), then rolled off sharply above 10k. At least the readings were consistent and stable with me outside the car.
I tried lowering the sub gain until the bass readings were closer to 90 dB and then listened to some music. It was so damn thin sounding, as if there was no sub at all! So.... I'm pretty sure my test CD is junk -- it must have the bass tones recorded at much higher levels. I ended up going back to my starting point, then added +1 on the treble on my 3-band EQ (set to 10k I think) and +1 on the other treble control (set to 8k I think). Also went to -1 on the midrange of the 3-band, set to 500 Hz. This gave me the treble I was looking for and everything was sounding good. Also, this put my volume setting on the HU for normal listening at around 25 out of 50 (it used to be 10 when I had all the settings maxed out :)).
So... I definitely feel like the system is set up better -- no more hiss, and nice smooth sound. Still, I'd like to get some accurate test tones and do a final check. Any suggestions?
It's OK to have a hump in the response below 100Hz. The size of your cars interior will reinforce certain low frequencies. This called cabin gain. The sweet spot in my TA is 55-60Hz. Most vehicles are between 40 and 80 depending on size. It also depends on what you listen to. I have an accurate setting on my EQ preset and then a couple more with varying amounts of bass centered around 60Hz. I only use the accurate setting when listening to classical (Telarc) or an audiophile CD that is recorded accurately. The bass isn't weak on those, but most other music is pretty weak on the bass so I use my bass enhanced presets for everyday listening.
I keep my EQ settings above 100Hz the same for everyday listening as I do for the audiophile recordings. I only alter the bass for the different music types.
It's good your using 25 of 50 as opposed to 10 of 50 on the volume. I'm guessing you have no amps and are powering the non sub speakers from the headunit? If that's the case then it's fine. If you had an amp on them I would suggest turning down the gain so you could make the max volume 40-45 of the 50. That will help to get rid of the hiss even more. The hiss is basically your noise floor. Soft music or sounds can be hidden by it, plus it's just not good to hear it.
If you can get your hands on any of the IASCA test CD's along with it's liner notes, they can really help out with tuning, but they won't have the 1/3 octave test tones.
Anyone still watching this thread, it's a bit old but I just found it.
I was wondering if this tuning should be done at speed instead of in dead quiet.
I realize the road noise at 70mph will be a huge 'problem' but if that's the environment that you're listening to music in the majority of the time, then wouldn't there be some logic to tuning at 70mph?
I have that RS meter and I was planning on using it to check out road noise and my system's characteristics before and after a noise barrier treatment. I haven't decided what exactly to use, but I've found some really great threads on the subject and I'll go from there. Plus, I'm adding a second sub in short order and I want to see the numbers on how things change.
One last question... are the terms dB and SPL interchangable? Like at a bass competition is the SPL they are trying to achieve just refering to a particular dB sound level for a given frequency? Like achieving 120 decibels for 80hz or something?
Thanks in advance!
I cannot recomend tuning while driving.
The ONLY way I would recomend it is if somoene else is driving, and even then, if you're going to tune like that, you're probably going to be tuning for the drivers seat, so you had better trust your friends ears.
Rather than go through all of that hastle, just tune sitting still. I'd say that 99.9999% of people out there do this. That will give you a base line. Once you start driving and hear some differences, stop and make adjustments.
SPL is sound pressure level.
dB is the measurement unit for SPL.
Now does anyone know of a handheld meter that is auto-range and has a better range? I'm already able to max this meter without trying and some background measurements I'd like are below the bottom threshold.
What about a software meter to run on the carpc? Surely that's been done, right?
trueRTA software+ Behringer ECM8000 mic + micpreamp and/or good soundcard + computer. Probably the next step up from the ratshack meter as far as simplicity and price.
You might want to look into TrueRTA and a mic for it.
Might be beneficial to you not just for SPL purposes, but for tuning in general.
OK, so I was looking for a handheld meter with a better range, but they all top out at 130. I think I found that they do that because 130 is considered deafening. Am I on the right track there?
I found the frequency range of TrueRTA, but not the decibel range... anybody know?
I realize this RS meter is a cheapie, but I'm over it's 120(126) limit easily and the volume is loud, don't get me wrong, but not deafening. Is this meter just that far out of whack that when it shows 130 I may actually be much lower than that? Or maybe I have bionic ears? I've continually beaten up my ears since high school but can still pass a hearing test with flying colors so it's not just me going deaf I assure you. *smile*
As an example, Linkin Park's "What I've done" at volume level 25(out of 35) easily peaks the meter and isn't nearly loud enough to be painful. Conversation is out, that's for sure, but ears aren't bleeding and there's no distortion yet.
Passing 30 on the dial starts to introduce distortion and starts to be uncomfortable. That's one thing I wanted to know the level of, but cannot find a meter that goes over 130.