rich20730

Got some new toys in the mail today:



I bought the Studio Six Audiotools app suite a while back for my iPhone and iPad and have been fooling with it for the last couple months. The software is really good, but its usefulness is crippled by the filters in the iPhone/iPad's internal mic. After doing some research I decided to step my game up and try a more accurate, calibrated setup to get a better assessment of my in-car response. I figured I'd post a thread for anyone considering using an RTA to help fine tune their system.

If you have an iPhone/iPad I think it's pretty hard to beat in terms of price, portability, accuracy, and software capability.

Here's what you need:

1. iPhone/iPad

2. Audio Tools from Studio Six Digital $19.99 http://www.studiosixdigital.com/audiotools.html

3. iPhone/iPad Camera connection kit: $29

4. ART Dual Pre USB Interface: $69

5. Dayton Audio EMM-6 Measurement Microphone $48

6. XLR Mic Cable: $8

stevemk07

I love science and music but what do you shoot for in terms of your response graph? Is there some optimum response curves or is it just make sure the components and octaves transition smoothly?

rich20730

That's a very good question. I've been reading up about that as much as I can. I have this thread from DIYMA bookmarked:

http://www.diymobileaudio.com/forum/...curve-car.html

If you ask 10 people that question you may get 10 different answers. Either way it can't hurt to try different response curves so you can figure out what sounds good to you. It helps me a lot to be able to visualize what I'm hearing.

Initially, I'll probably shoot for something like this:

Andy Wehmeyer: "+9dB from 20-60Hz, smooth transition from 60 to 160. Flat from 160-about 3K, gentle slope downwards from there (adjust this slope and the amount of bass for personal preference). I've used this for nearly 20 years and no one has ever complained. "

Trunk Monkey

iTrader: (1)

Very cool rich! Would love to have something like this sometime. I think I'm about to offload the 3sixty.2 and pick up an MS8, Bit.1 or wait for the Arc PS8 if it's truly coming soon. The cool thing to do would be to get your response on the RTA with the calibrated mic and then take one with the Iphone4 mic and compare them. Be cool to see if the IP4 mic misses out on 40hz and below, 12kHz+, etc.

Steve...and anyone else that might want it, I'm at work right now but I'll post up a very nice frequency graph that I found later when I get home. You can put your mouse over it and it'll tell you what that frequency range is responsible for, what it sounds like if it's too boosted or cut too much, etc. VERY helpful if you're just starting out or if you're a novice.


One more question, what's the need for #3? I just happened to get a $100 gift card to Amazon for graduation.......

rich20730

The only way to bypass the iPhone/iPad internal filters is to hook up through the dock connection. You need the camera connection kit to connect the usb to the dock connector.

I haven't gotten the chance to do a side-by-side comparison using the same tune yet, but the iphone mic rolls off pretty steeply in the lower octaves.

Here's an older snapshot using the internal mic:



Here's one from last night with the EMM-6:



You should get it! If you already have an iPhone and the Audiotools apps, it's really not much more for the rest of the setup. Plus you can use the mic and the usb interface with a laptop and TrueRTA or REW.

You'll definitely want a good RTA if you get the BitOne. I wouldn't hold you breath on processors that are supposedly coming out soon. Look at the 3Sixty.3. It's been almost two years and it's barely about to come out... maybe

I think the RTA is going to cause me to buy a better processor. 3 bands of parametric EQ just isn't enough

Trunk Monkey

iTrader: (1)

Well the H800 looks nice, but it sucks you have to have the RUX (head unit) to control it. Maybe Jerry has more info about when the PS8 is set to release and if they're actually going to make that date or not. The Bit.1 test just okay on diyma when put up against the H800. And yeah, that 3sixty.3 will never come out it seems lol. I know the admin over at Steve Meade (i'm assuming that's his name) got his like last week...so maybe they're close!

If I were you, I'd look into more power before swapping processors. I'll likely put my 360.2 up soon as I want to try something else

rich20730

Yep, I have the H660. I like it and for ~$200 it's pretty hard to beat. Yes it has an autotune which is pretty much the same as the Audyssey technology used in home theatre setups. Same microphone and everything. (I have a Denon receiver with Audyssey)

According to the literature, the autotune uses spacial averaging based on up to 8 measuring locations and then sets an inverse filter using 512 points of equalization. A lot of mumbo jumbo, but the result sounds pretty good. Imaging and staging are spot on and good tonality.

After running the measurements, it gives you a choice of target curves to choose from. All the target curves are pretty similar and mainly just allow you to choose how much bass you want.

Adjustability after the tune:

Crossover points: You can adjust the crossover points, but you are stuck with 12db/octave slopes except on the sub which gives you the option of 12/24.

Time alignment: You can adjust time alignment for each channel in 0.1ms increments. I can't remember exactly how much you are limited to total, but it gives you a pretty wide range.

EQ: 3-band parametric. One for Bass, Mid, and treble. +/-6db and Q from 0.5-2.0

Overall, it's a pretty good processor, but I wish it had at least a 5 band parametric EQ with +/-12db rather than just 6db and more adjustability for the Q

As far as the H800, it looks to me like the H660 on steroids. From reading the comparison with the BitOne it has as much adjustability as the BitOne, but also has an autotune and surround capabilities. I also haven't seen many complaints on DIYMA from people who own it. Based on that and my positive experience with the H660 I would probably get the H800 if I upgrade.

I think on the H800 you have the option of 10 band parametric or 31 band graphic with +/-12db of adjustment and a wide range of Q widths. 10 band PEQ would be sweet!

I believe there are others from Alpine. 701 & 990 maybe, but I don't know much about them. I don't know much about the MS-8, but it would be a major pain in the ass to run a new tune every time you adjust anything.

stevemk07

Good information in that link from DIYMA. I read the whole thing and looked at the graph. I thought it was interesting that the magic response graph they were talking about showed a peak at 60Hz and a slope down from there towards either side. It confirms to me that a big sub is not necessary for music SQ (of course this is all just opinions). I adjusted my sub setting and at this point I do not think I need to upgrade anything else except deaden the doors a little bit.

I will try to take some measurements and post them. I have a Zoom H2 microphone which I have used for recording big meetings (minutes) and for putting in front of my guitar speaker to record guitar tracks with my tube amp cranking the tones. It does a good job at both but I am not entirely sure how accurate it would be for RTA purpose. I have audiotools on my Xperia X10 and use it supply the pink noise. According to the audio response test results posted on Sony's site with the upgraded OS of the x10 the pink noise should be fairly accurately output.

I love this stuff and I guess this makes me an audiophile in training.

I am curious to see how close (if at all) my response is to that graph (and yours).

rich20730

I agree. If only I could find my job this interesting. Looking forward to your results.

On another note, check out this Craigslist score I picked up today for $100:



- Image Dynamics CTX 6.5cs
- Boston Acoustics GTA 400M (400x1 @2ohms)
- Cadence ZRS 1502 (150x2 @4ohms)
- Eclipse 10" Sub w/ sealed box
- Monster Cable RCA's

All in mint condition.

I have no use for any of this stuff, but still stoked about the deal

Trunk Monkey

iTrader: (1)

Wow! All that for $100...nice job! I'm sure there will be plenty of people willing to jump on those ID's on here. About to put my 360 up so maybe someone can build them a system

rich20730

Okay got a chance to do some side-by-side comparisons:

1. Here's what the frequency response looks like before running the Audyssey auto tune:




Iphone internal mic vs. EMM-6 (After auto tune):

EMM-6:



Iphone mic w/ compensation filters (Audiotools' solution to account for the roll-off of the internal mic):



Iphone mic with no compensation filters:







So in conclusion:

1. A processor can make a big difference

2. The iPhone mic and Audiotools is pretty accurate from 20khz down to 250hz, but below 250hz you might as well be guessing.

stevemk07

Whoah :-o
I took some measurements today but just figured out how to post images. Much like html I see. Will post tomorrow. I think my graph looks closest to the pre-auto-tuned one you posted. I would be interested to be able to adjust more frequency bands rather than have a processor do all the work and it does not seem people are pleased with the processors they have now. Know of any good equalizers that dont cost an arm? I have trouble seeing the benefit of time alignment with such short distances between anything in my car.

rich20730

A processor with an auto tune is helpful to give you a nice starting point to work with as long as you can make adjustments after it's done. The only real complaint I have about the Alpine unit is that it doesn't have a more powerful EQ that you can adjust after the tune.

I've actually been searching for a quality EQ at a decent price for a while and I haven't found a lot of options. The best one I came across was the Audiocontrol DQX. It has 30 bands of constant Q equalization and 2 bands of parametric EQ. I saw one on Ebay recently for $150.

The only reason I didn't buy it is because it doesn't do time alignment. The path-length differences in a car are big enough to ruin you sound stage and stereo imaging. It was not something I noticed until I started reading about it, and then it annoyed the hell out of me that all the music sounded like it was coming from the front left speaker.

stevemk07

Hmmm... Perhaps I just haven't thought it an issue because the TL system already has correct alignment and I would miss it if I bypassed the factory amp.

Anyone know if time alignment is done in the HU or stock amp?

stevemk07

Okay, here is a capture I took of an RTA I did just now. This is with bass at -3 and treble -1.

stevemk07

Here is another one with Bass at -4 and Treble at 0. Sub is at +2. I like the way it sounds with the stock amp and speakers. I think I just want to add more volume/power.

stevemk07

A note about the graphs above. If I could out how to show an average of the response it would likely look a bit smoother. Using a free progrm I downloaded called Spectral Audio.

rich20730

Yea, it might be a little easier to read if it has a 1/6 or 1/3 octave smoothing option. Maybe I'll try mine again using 1/24 octave and see how it compares. I think I remember reading that the stock system has a fairly steep roll off above 10k. Looks like that is true.

stevemk07

That was probably me who posted that data.

I thought it might be a little higher when I had the android upgraded and the software set up a little better. (It's got so many options that I do not understand yet)

It's probably a good thing though because of all the glass those frequencies could be bouncing off.