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Old 6th July 2010, 20:23   #1
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Default Time Alignment - Black Magic?

Gurus, and fellow members,

I have just completed my install and have a question about time alignment. At the moment, my install images beautifully - I can percieve the depth and the placement of some of the sound sources in the source material. However, given the placement of speakers in the door, the image is formed in the footwell.

I have done some reading on the subject and there appears to be a vast amount of information - confusing at times and at first glance it would appear that getting a nice stable image is closer to black magic than engineering.

Questions:-
1. would time alignment help form a coherent image? and what can I do with my exisiting set up in order for the image to appear somewhere in front of the dash?

2. can I obtain a satisfactory (subjective of course, but acceptable) sound stage given my existing install - without adding any more hardware? is this possible at all - just want to be realistic?

The install is in my Innova.
A quick list of the equipment follows:
1. Head Unit - Eclipse CD5100
2. Main Amp - Audison LRx 4.5
3. Door Speakers - Infinity Kappa Perfect - 2 Way components on all four doors
4. Sub - Infinity Kappa 124.7 - 12" - sealed 1 cu ft box
5. Sub Amp - Pioneer 3000 - 200 WRMS

Here is a complete write up of the install.

Any information, or help with regards to getting the best out of my current install is much appreciated. Am open to expermenting with the equipment as long as it doesn't hit my wallet.

Thanks in advance.
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Old 7th July 2010, 10:40   #2
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If you want to align the midbass to the tweeter you will have to go active. There is a 1 box solution (it has an internal 20W /ch amp) from JBL called the MS-8 that can offer yo enouhg channels of time alignment to cover these needs (with your existing HU). Alternately the Alpine 9887 offers you toe option of directing all the outputs to the sub and front channels only allowing you to get TA for the sub, midabss and tweeter.

Still you cannot compare the sound of your car system to teh coherence of your home system. The relative distance between you and your woofer/tweeter in the car is very different from what you have at home.
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Old 7th July 2010, 13:40   #3
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Navin, thanks for the recommendation. But this is one heck of a solution. The specs are great and some of the reviews are too. At USD 799/- my wallet nearly had a coronary!

Is there something else that I can do to lift the sound stage above my ankles, that doesn't cost money?
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Old 7th July 2010, 14:03   #4
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There is a simpler possibility - tilting the tweeter and midbass up by 15-20Deg, especially in large interior volumes like in Innova, Safari, Scorpio, Xylo etc.

@CJP, where are your tweeters mounted? ORVM pod or door?
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Old 7th July 2010, 15:25   #5
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Quote:
Originally Posted by CJP View Post
Is there something else that I can do to lift the sound stage above my ankles, that doesn't cost money?
For people who prefer coherence over being on axis I recommend installing the tweeter in the door instead of the OVRM.

My mom for example cant hear much over 12kHz and her msuic (western classical) demands coherent soundfield so the tweeters in her car were installed on the door. Sadly soon after we did that install (about a year later) she had a fall and broke her left arm and back and cant drive anymore but that is another story.

Hence we have now done the same install in the rear doors (where she now sits) and we padded the front speakers down about 6db (at the amp) so that the driver is not disturbed.
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Old 7th July 2010, 20:01   #6
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Quote:
Originally Posted by DerAlte View Post
There is a simpler possibility - tilting the tweeter and midbass up by 15-20Deg, especially in large interior volumes like in Innova, Safari, Scorpio, Xylo etc.

@CJP, where are your tweeters mounted? ORVM pod or door?
DerAlte - the tweeters are mounted in the door (non-stock location). The tweeters can be tilted and/or rotated in a limited range.

The mid bass units are mounted in the stock location, firing into the footwells.

After doing more research and lots of reading - I would refine my requirements as Navin has suggested - coherence.

Navin is right (of course!) true time alignment between the tweets and the mid bass units will require me to go with active xovers for all channels and I can't afford even the cheapest (Rockford Fosgate 3Sixty.2)

@DerAlte - you were suggesting that I tilt the drivers - could you please clarify in what direction? Will tilting the mid bass drivers by 15 - 20 degrees upward - firing toward the listener's ears work? The tweeters are positioned like this now, since they are closer to the listener - am experiencing the tweeters first and then the mids come on.

The mid bass drivers are mounted in the traditional mdf rings - I'll have to make some custom rings in case I have to tilt the axis of these speakers. Perhaps tapering off one side or adding material to the other or do both will tilt the mid bass drivers.
thanks very much

Note from the Team-BHP Support Team : Please use the "edit" button if posting within 20 minutes of the first post, instead of creating another back-to-back post.

Last edited by Technocrat : 9th July 2010 at 04:19. Reason: Please read the note in your post, thanks
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Old 8th July 2010, 10:56   #7
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Quote:
Originally Posted by CJP View Post
The mid bass drivers are mounted in the traditional mdf rings - I'll have to make some custom rings in case I have to tilt the axis of these speakers. Perhaps tapering off one side or adding material to the other or do both will tilt the mid bass drivers.
thanks very much
Many years ago I did this in a Zen. The Drivers were Vifa 5" and the famous D26NC. There are 3 parameters you can play with.

1. lower the Crossover point (to as low as 1500Hz - do not go lower than tweeter Fs x 2) and Q of the crossover (you need some software like LspCAD to do this).

2. Tilt the axis of the midbass by about 15 deg (any more and it will hit your leg when you exit from the car)

3. Cross the woofer at 6db/oct instead of the usual 12db. Is your midbass driver cone made from doped paper? I prefer these when shallow slopes are involved as they do not breakup badly at higher frequencies. Also a low loss rubber surround helps tame the breakup nodes. I am not a fan of the high loss rubber surrounds even though some drivers Vifa's famous P13 used in the Aerial DIY speaker for example have high loss surrounds.

Since i was starting from scratch (building my own crosovers) it was a lot easier for me as I had all the tech specs of the drivers.

You will loose the stock look in the doors. The tilted MDF rings will have to be integrated into the doors and the best way to do this is to make a thin fiberglass ring epoxy glue this ring toe the rear of the door panel and use lock nuts to ensure that the MDF ring does not rattle.
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Old 8th July 2010, 13:03   #8
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Quote:
Is there something else that I can do to lift the sound stage above my ankles
do some research on the CDT imaging tweeters - basically their method involves lowering the output levels of your door mounted tweeters and adding a set of tweeters highpassed at above around 14khz to raise the stage

it doesnt need to be the cdt tweeters specifically but they do need to be crossed over at a high point and you can reduce the level of your main tweeters a bit

with these tweeters closer to ear level it will definitely raise your soundstage ..... even if its only psycho-acoustics ie your ear is fooled by what your eyes see

unfortunately though this will cost money for some tweeters as well as the necessary items to construct the crossover and maybe some additional amplification (but in terms of amplification if you could build a proper high pass passive crossover you could power these from the front channels of the headunit

Last edited by naughty001 : 8th July 2010 at 13:06.
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Old 8th July 2010, 17:51   #9
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Navin and Naughty001,

First of all thank you for your inputs. Here is what I am going to do, in phases, so that I can evaluate if I am done and then move to the next level. Moving in phases also gives me some financial flexibility.

Time Alignment - Black Magic?-img_6634.jpg
Step 1
This is how the tweeters are mounted currently. They fire horizontally at the listener's ears. I'm planning to move this so that it fires perpendicular to the door. Hopefully, moving the tweeter off axis will solve the acute directionality.

Step 2 - Navin's & DerAlte's Recommendation
Quote:
Tilt the axis of the midbass by about 15 deg (any more and it will hit your leg when you exit from the car)

You will loose the stock look in the doors. The tilted MDF rings will have to be integrated into the doors and the best way to do this is to make a thin fiberglass ring epoxy glue this ring toe the rear of the door panel and use lock nuts to ensure that the MDF ring does not rattle.
I'll try this next, will get a pair of MDF rings machined/sawn at the correct angles and figure how much interference there is from the stock plastic grill on the door. Navin, as you rightly called out, I may have to make some modifications (big hole) to the stock grill in order to accomodate the mids firing upward.

Navin's Recommendation -
Quote:
lower the Crossover point (to as low as 1500Hz - do not go lower than tweeter Fs x 2) and Q of the crossover (you need some software like LspCAD to do this
I can figure building a cross over or source one from Madisound or Parts Express. I'll get to this after I've figured Steps 1 and 2.

Naughty001's Recommendation -
Quote:
do some research on the CDT imaging tweeters - basically their method involves lowering the output levels of your door mounted tweeters and adding a set of tweeters highpassed at above around 14khz to raise the stage

it doesnt need to be the cdt tweeters specifically but they do need to be crossed over at a high point and you can reduce the level of your main tweeters a bit
Good point, did some reading on the Internet. Makes sense, will need to plan some money. USD 200/- for another pair of tweeters plus a crossover. CDT have a whole range of tweeters that are specifically made for improving imaging.

Naughty001 - have you used these yourself? Any recommendations or feedback about which specific model etc?

Again, will hold this till I complete Steps 1 & 2.

Gentlemen, I appreciate your inputs and feedback, and thank you for being part of my journey.

Last edited by CJP : 8th July 2010 at 17:53.
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Old 8th July 2010, 18:30   #10
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Quote:
Originally Posted by CJP View Post
Navin's Recommendation -

I can figure building a cross over or source one from Madisound or Parts Express. I'll get to this after I've figured Steps 1 and 2.

Naughty001's Recommendation -

Good point, did some reading on the Internet. Makes sense, will need to plan some money. USD 200/- for another pair of tweeters plus a crossover. CDT have a whole range of tweeters that are specifically made for improving imaging.
Be careful with the crossover point. Our old timer friend must have had access to a lot of documentation before getting to putting together his crossover.

Manufacturers design stuff with very good reason. The kit in concern has a tweeter with a Fs of 1370 Hz. Although in theory, you could cross over at 2800 Hz with 12dB/ octave slope, it does not mean that the tweeter can be expected to play smooth if you lower the crossover point. There could be some break-ups etc which they are probably avoiding by cutting off at 3.5kHz and using a 24 dB slope. The manual for the speaker does not have a plot of the tweeter alone, without factoring in the crossover's transfer function, thus its hard to tell.

Image enhancers - It is a bit debatable as to how much the image can be elevated by raising the height of the source of frequencies 14kHz or so and upwards. That band has the least amount of information. And rather than spending so much on "workarounds", it would be better, in my opinion, to get a head unit that does TA, because all said and done, none of your exercises will address the problem of path length difference. Anyway, all the best!
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Old 9th July 2010, 02:46   #11
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Quote:
Naughty001 - have you used these yourself? Any recommendations or feedback about which specific model etc?
unfortunately i have not used specific CDT items myself since they are not available where i live - hence i was just pointing out their methods employed as a potential way to solve your problem so no i havent used any of the specific CDT models .... though i have tried out their methods with alternative equipment and gotten decent results after experimentation

Quote:
14kHz or so and upwards. That band has the least amount of information
it doesnt need to be 14khz specifically - you could make it lower but i prefer not to replicate too many frequencies all over the place because you may create phase problems - the idea is that due to the precedence effect you get to hear the closest speaker as a direct sound and then all other sounds seem as if they are just stretched bits of the original sound and then this will fool your ear into thinking that the sound originates from where you heard the initial bit of the note - and the highest speaker is obviously closest to you hence your brain interprets it as if the sound arrives from there

Quote:
it would be better, in my opinion, to get a head unit that does TA, because all said and done, none of your exercises will address the problem of path length difference.
agreed that specific path length difference between individual drivers is also an issue but the problem he has is of a more involved nature - he has the tweeters physically in the door and sadly even T/A wont make it seem like the soundstage is further forward in front of him ie at the windshield or even on top of the bonnet (top of the bonnet will require extraordinary speakers ..... those will be expensive)

instead his soundstage even with T/A applied will be closer to him much like a pair of headphones ie it will stretch wide but it will probably be more in-his-face and not away from him as if he were seated in the audience but more like he was a part of the performance and this is less accurate than him seeming to be a part of the audience

this is a reason why im not a fan of putting tweeters in a door - but nevertheless they are there already so theres not a lot that can be done about that unless he wants to move them

if he really doesnt want to use a secondary imaging tweeter then he needs to actually change the installed location of the tweeter - this could be to the kick panel and then pointed generally to the directions required OR even to move those to the base of the a-pillar so they are far forward and then applying that T/A for the path length differences (he will off course improve only one seat ie the drivers soundstaging in this manner and the passenger will be worse off but im sure most people wont care about that because most passengers dont know much about sound and they dont pay for the equipment anyway) - hence he wont spend on additional speakers and is then free to get a head unit that does have the necessary T/A functionality or alternatively a processor with that T/A functionality
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Old 9th July 2010, 11:04   #12
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I can figure building a cross over or source one from Madisound or Parts Express. I'll get to this after I've figured Steps 1 and 2..
No do not do this. These XOs do not have phase and impedance correction.

You need to get the tech specs (and I dont not mean just the T/S specs) of the tweeter and midbass to design a crossover.

Quote:
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Be careful with the crossover point.

Manufacturers design stuff with very good reason. The kit in concern has a Fs of 1370 Hz.
There could be some break-ups etc which they are probably avoiding by cutting off at 3.5kHz and using a 24 dB slope.

to get a head unit that does TA
B&T is right. If you do not have complete tech specs of the tweeter you can damage it. I used the D26NC and I had all the tech specs straight from Videbeak B&T knows me well.

If the current XO is 3.5k/24db there must be a goodreason for this. Without FRD curces, T/S specs, etc.. I cannot advise you as to how low you can go with this tweeter.

B&T, I just looked at my old notes. The tweeter I used was the D26NC05 not the D26NC55. They had been modified by enlarging their back chamber and removing that piece of foam that did more harm than good. The Fs of this modified version was 900Hz but they had an excellent suspension so even Xoed at 1800Hz/12db they survived the Zen and later the Opel Astra. Not bad for a tweeter that I paid DM 16.11 (DM 128.88 for 8 of them) for (including a wedged shaped housing).

A 9887 would be the simplest option. Definitely simpler than the CDT tweeters. But you dont learn by using the simpler options. I suspdect CJP wants to leanr more about speaker design. How often do you come across a person who demands coherence over everything else.

Last edited by navin : 9th July 2010 at 11:07.
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Old 9th July 2010, 11:07   #13
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Originally Posted by naughty001 View Post
it doesnt need to be 14khz specifically - you could make it lower but i prefer not to replicate too many frequencies all over the place because you may create phase problems - the idea is that due to the precedence effect you get to hear the closest speaker as a direct sound and then all other sounds seem as if they are just stretched bits of the original sound and then this will fool your ear into thinking that the sound originates from where you heard the initial bit of the note - and the highest speaker is obviously closest to you hence your brain interprets it as if the sound arrives from there
I have a differnt opionon here. The ear are more senstive in the midrange than the high freq section. And in a two way kit the major work is done by the midbass. Even if we use a tweeter which will give 10k+ freq will make the image shift a little above but that will not fully help in keeping the stage above the dash.

I am using compression horns drives which are installed below the dash, but with the Help of TA hu I am able to bring them up not on the dash but atlest close to the A/c vents. (I have a Suzuki Swift). For more better result I use the tweeter on base of A-piller with are installed on-axis to give better result, I normally cut them from 8-9 khz. With the help of TA one can achieve the BLACK MAGIC results.
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Old 9th July 2010, 17:24   #14
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Gentlemen,

This is a very interesting discussion. At this point, I don't see any disagreement about Steps 1 & 2. I'll get these done and revert with results.

In the meanwhile,
Quote:
I suspdect CJP wants to leanr more about speaker design. How often do you come across a person who demands coherence over everything else.
That was an insightful observation, Navin.

My home system is a 2.1, the main speakers are 8" P-Audio, BM 8CXA, Co-ax supported by a 12" Eminence Lab 12 Sub in a ported enclosure. The receiver is an Onkyo 90 WRMS per channel. The sub is powered by a plate amp that delivers about 150 WRMS.

Great sound stage, imaging, excellent coherence and musicality.

Since, I am continually comparing the two, the lack of coherence drives me up the wall when I am in car.

Naughty001, hit the nail on the head. I agree with the analysis. All that a TA capable HU will accomplish is the TA between channels, not the individual drivers. In order to accomplish proper TA between the individual drivers and the channels, I would need to expend a ton of money and go full active.

LBM's suggestion is intriguing
Quote:
I am using compression horns drives which are installed below the dash, but with the Help of TA hu I am able to bring them up not on the dash but atlest close to the A/c vents. (I have a Suzuki Swift). For more better result I use the tweeter on base of A-piller with are installed on-axis to give better result, I normally cut them from 8-9 khz. With the help of TA one can achieve the BLACK MAGIC results.
Sir, could you provide a little more detail, perhaps a pic or two to help?

Thank you gentlemen, for a very absorbing discussion. Am learning something here and I appreciate your help.
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Old 9th July 2010, 19:03   #15
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but the problem he has is of a more involved nature - he has the tweeters physically in the door and sadly even T/A wont make it seem like the soundstage is further forward in front of him
I'm sorry but I disagree here. I have had coaxials installed in the door panels provide a reasonably good image. Navin here has in fact heard one such setup of mine. There were a pair of dummy tweeters sitting on the dash. All of the people who heard that car could bet they were the ones playing.

Sure the doors are not the best locations for the tweets, but you can make them sound better than what can be achieved with no time correction.

Quote:
Originally Posted by CJP View Post
Naughty001, hit the nail on the head. I agree with the analysis. All that a TA capable HU will accomplish is the TA between channels, not the individual drivers. In order to accomplish proper TA between the individual drivers and the channels, I would need to expend a ton of money and go full active.
So, do you think the various drivers in your or any other home, 2 channel setup are reaching the ears of a listener in the sweet spot at the same time?

If not, would it not be more imperative to have the arrival time difference eliminated or minimized between the channels rather than the drivers?

Quote:
Originally Posted by CJP View Post
LBM's suggestion is intriguing

Sir, could you provide a little more detail, perhaps a pic or two to help?
He means something of this sort -

Time Alignment - Black Magic?-p1120054.jpg

Time Alignment - Black Magic?-p1120055.jpg

Time Alignment - Black Magic?-p1120059.jpg
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