25 replies to this topic

[Matt VIP]

Hi gang

I'm currently thinking about building a centre channel using a Hybrid Audio L4 in the dash pointing directly up to the windscreen , with a tweeter at the base of the windscreen firing directly forward between the passanger and drivers' seats.

the mercedes dash has a spot for a factory 4x6 I think, although I havent yet pulled it apart to investigate. However, apparently you can fit 2 4" speakers in there with a bit of work.

Dash looks like:



Tweeter will be in similar pods as the ones on the L+R:

 raised pod.jpg   22.51K   5 downloads

Questions I have:

1. Given the centre driver will be 90degrees off axis to the listener, should I think about some sort of waveguide to help the 3.5kHz - 5kHz hole that is likely when the speaker beams? (assuming the L4 beams at about 3.5kHz...)

2. Should I put 2 l4's in there if possible? How will that affect off axis response if they are side by side?

3. What are the likely acoustical issues if the driver is mounted slightly below the dash, firing directly up into the windscreen? Does the refection become the point source for the listener?

4. Should I vent the rear of the enclosure into the dash, or should I consider some sort of aperiodic mat to reduce rattles inside the dash?

5. What are the other issues you can think of, and where would I start reading about them?

6. Has anyone developed any sort of acoustic lens technology for a 4.65" midrange? That would be awesome....


thanks gang!!

[data_mine]

You need to get some red leather dye.

What do you hope to accomplish with a centre channel? How will you create a centre channel? (do I sense a MS8 in your future?)

[Damo95]

I think you need to talk to Shiny_car Matty..

He's successfully done a centre channel in both Alfa's (old 156 & current GT)... used a single 4" speaker i think..

[Matt VIP]

data_mine, on 30 March 2010 - 10:31 AM, said:

You need to get some red leather dye.

What do you hope to accomplish with a centre channel? How will you create a centre channel? (do I sense a MS8 in your future?)

How do the above questions answer the questions I originally posted exactly?

And whats an MS-8?

[data_mine]

You should know by now, I'm anything but useful

I ask because, you seem to like doing out there complicated things, none of which have worked for you. Get the basics right first (I know, are you pot or am I?).

[Matt VIP]

3rd at nationals, 1st at ACT state final...things haven't worked out too bad I reckon...

Obviously this question is in the context of a processor that can derive (and in fact requires) a centre channel in order to deliver the best sound and imaging.

So, seeing as I don't yet have said processor in hand, I thought I'd do some preliminary thinking around how best to implement a centre channel.

Especially seeing as my car is actually built for one....

[shizzle]

Heya,

Not sure if you checked out Patrick Batemans multiple threads on DIY Audio? He may not give the exact answer, but he has a knack of explaining in terms one can understand, and has multiple threads to help broaden ones mind.

Again, I am sure you have checked these, but just thought I would put it out there

http://www.diyaudio....oacoustics.html

http://www.google.co...s=1269910949356

Cya

[268669♫]

Hi Matt,An acoustic lens for the L4 would be very big for the frequecies you are aiming for. I believe you may be able to EQ the L4 to fire directly at the windshield, however I would try and place the L4 right into the corner at the back of the dash and get it to fire towards the rear of the car as much as possible and use the windshield as more of a waveguide than a reflection. If you can cut out the area where the centre speaker grill is and make it a waveguide for the L4 to fire down you may just eliminate alot of reflections and get more on axis for each listener.I would also wait for the L3 pro and use it as a full band and not use a tweeter.As for the venting, can you vent out through the firewall into the engine bay and use some AP mats. Another option is to use the Dayton dom mids that are sealed. Very capable driver. Or any other sealed midrange, I hear the morels are good too.AntP.S. Did you find someone on DIYMA who will get you one? I think I've got someone who will help me.

[Luke352]

268669, on 30 March 2010 - 12:36 PM, said:

Hi Matt,An acoustic lens for the L4 would be very big for the frequecies you are aiming for. I believe you may be able to EQ the L4 to fire directly at the windshield, however I would try and place the L4 right into the corner at the back of the dash and get it to fire towards the rear of the car as much as possible and use the windshield as more of a waveguide than a reflection. If you can cut out the area where the centre speaker grill is and make it a waveguide for the L4 to fire down you may just eliminate alot of reflections and get more on axis for each listener.I would also wait for the L3 pro and use it as a full band and not use a tweeter.As for the venting, can you vent out through the firewall into the engine bay and use some AP mats. Another option is to use the Dayton dom mids that are sealed. Very capable driver. Or any other sealed midrange, I hear the morels are good too.AntP.S. Did you find someone on DIYMA who will get you one? I think I've got someone who will help me.

The part in bold sounds like the best plan and able to achieve the best results. Bury it right down at the base of the windshield firing back into the vehicle using the windshield and dash as the waveguide, with a smaller waveguide out to the sides. If you could find a ribbon that could play low enough it would work great I think, since when placed onto it's side you'd get great horizontal dispersion.

[Marc ♫]

data_mine, on 30 March 2010 - 11:00 AM, said:

You should know by now, I'm anything but useful

I ask because, you seem to like doing out there complicated things, none of which have worked for you. Get the basics right first (I know, are you pot or am I?).

Post of the week!

[data_mine]

Marc, on 30 March 2010 - 01:54 PM, said:

Post of the week!

Careful that makes it sound useful.

[syd-monster]

Matt VIP, on 30 March 2010 - 10:14 AM, said:

Hi gang

I'm currently thinking about building a centre channel using a Hybrid Audio L4 in the dash pointing directly up to the windscreen , with a tweeter at the base of the windscreen firing directly forward between the passanger and drivers' seats.

the mercedes dash has a spot for a factory 4x6 I think, although I havent yet pulled it apart to investigate. However, apparently you can fit 2 4" speakers in there with a bit of work.

Dash looks like:



Tweeter will be in similar pods as the ones on the L+R:

raised pod.jpg

Questions I have:

1. Given the centre driver will be 90degrees off axis to the listener, should I think about some sort of waveguide to help the 3.5kHz - 5kHz hole that is likely when the speaker beams? (assuming the L4 beams at about 3.5kHz...) - a wave guide will help. A center channel (from what little I know about them needs to concentrate on the 1Khz to 4Khz range.) More so though, you need to think about the length of the guide and how you can get it to mate smoothly with the windscreen/dash as the length of some of the waves will need to use the screen eventually. The smoother this transition, the better overall it will work. Any jaged or steep changes in transition cause unknowns/reflections.

2. Should I put 2 l4's in there if possible? How will that affect off axis response if they are side by side? - for now I recommend you stick to one.

3. What are the likely acoustical issues if the driver is mounted slightly below the dash, firing directly up into the windscreen? Does the refection become the point source for the listener?
- it froms a secondary reflection. Thus a second delayed, echoed or wakened source. This could be a benefit or a negative, pending on how it turns out or you tune.

4. Should I vent the rear of the enclosure into the dash, or should I consider some sort of aperiodic mat to reduce rattles inside the dash?
- If you band pass the L4 from 180Hz up then you should see minimal rattles. The L4 loves air so I would give it as much as possible.

5. What are the other issues you can think of, and where would I start reading about them? - see PB post on DIY as ant put up. But note that his own waveguided mids are still at the far ends of his dash, this was his best liked compramise. but that doesn't mean you cant experiment. See below for more though.

6. Has anyone developed any sort of acoustic lens technology for a 4.65" midrange? That would be awesome....
- for a start, a large cut down funnel gave me much benefit with my L3's and L6's. That is the funnel is cut at the small end to allow the drivers cone to sit up against it. Then fab a fixing system. See how did my tweet but in bigger scale.

thanks gang!!

Hi Matt,

Ive been doing a lot of waveguide experiments lately, but non for the L4.
But see above and I hope that helps. - Chris

ps, Im also curios what you are trying to achieve? a solid stable center image? If so forget a center channel and concentrate on those kick panel mids. Disconnect everything else and get it solid and centered with those two first (playing band pass of course), play with axis angles, distances and also cover the bottom of your dash. See SB's shot's of Black Betty on BHIF, *edit i stuck the relevant photo below, see how the under dash area transitions to the edge of the dash with those formed panels (they have slits for the pedals).
Also you have a proven technique, so think about your tweet pods on a larger scale to suit your L4's or waveguide them down there instead. As this also has better PLD then on the dash. Don't be lazy... you know that's what you need to do.

http://www.buwaldahy...file.php?id=810

Edited by syd-monster, 30 March 2010 - 06:24 PM.

[Pulse-R]

use the space under the vent to create your barrel.

as syd. said, you need to make the transition as smooth to the windscreen as possible.

also smooth to the dash would be good, like an aero port.


a tweeter may attract too much attention, audibly, so may not even be necessary.

[~thematt~]

1. Not really. Normally you should, but the windscreen will help more then you might realize. You just need to terminate perfectly.
2. No. If you're going to array, you should use a smaller driver. Like an Aura, or a Dayton. Cheaper, more effective in an array.
3. Yes. The 'reflection' becomes the point of 'perceived source'. It doesn't become a secondary reflection if the primary source is disturbed by burying the driver into the dash. Hard to do though.
4. Vent it. AP will be a nightmare.
5. The biggest issue will be getting the mids inside your dash, fabrication wise. Getting them wide is more important then getting them farther back. Maybe think about mounting them on a 45 vertical angle in the dash, firing out, and curving the dash into a waveguide itself. Complex I know!
6. If I was waveguiding, I wouldnt use a 4.65" midrange. Too big. Smaller would be more effective. Just IMO.

[zion187reigneth]

I would first discover your bandpass for the center, then use a driver that is equally good either side of the bandpass cutoffs.

This means using some data that someone else has already summed up .
Find your theoretical bandpass.
pick your speaker
design waveguide
Cut car up

You love the simple things don't you ?

Edited by zion187reigneth, 30 March 2010 - 11:28 PM.