Passive crossover design |
Post Reply | Page <1234 5> |
Author | |
odc04r
Old Croc Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 5482 |
Post Options
Thanks(0)
|
You sound like you have a pretty good idea of what you want. Conventionally the xover is the last part of the system to be built and installed but as you are at a premium with space I see why you are thinking about it now.
The best bet is probably keeping it simple. The bass driver already has a modest roll off due to its natural inductance. If you measure its impedance and do some simple maths you could double the roll off slope with an appropriately sized series capacitor. Your problem is going to be that steeper filters for good sub/high separation require more passive components and complex design. Is it possible to apply active filtering before an amplifier? That might solve a lot of your problems and with surface mount parts an active xover could be made very small. |
|
Modeller
Registered User Joined: 03 March 2016 Location: UK Status: Offline Points: 31 |
Post Options
Thanks(0)
|
That is correct Studio45, the sounds are industrial (engine and other noises) but what I have found on the previous model is that the bass driver has too much to do and colours the top end especially. What I plan to do is single out bass notes up to about 8kHz and have the mid/highs handle everything else.
The amp I am using is 3W at 4-8Ohm. The driver selection will depend on the final enclosure design which I will run by you here later, but I only have about 40mm width and no more than 60mm length. I'm looking at the height now, but will probably be in the order of 30mm or so. The sound unit will incorporate 3 small speakers (sub, 2x mono mid/high) from which I hope to design a good below 200Hz bass response, lower if possible at approx 70-80Db, which I think is achievable. I managed below 250Hz with a pair of 34mm round full-range speakers in a reflex enclosure, so with a 40x60mm sub in a similar enclosure I hope to achieve better results. At the moment I'm looking at a compact transmission line design, but I've not finally decided yet. I really want to crack the crossover and driver selection before I start on the enclosure. Thanks again
|
|
studio45
Old Croc Joined: 16 October 2007 Location: United Kingdom Status: Offline Points: 3864 |
Post Options
Thanks(0)
|
I think I'm getting a clue here....This isn't for a soundsystem, it's a scale model of some machine or other, and you're putting a very small set of speakers into it because you want it to make the same noises as the full-sized version?
If that's right, then this might be much simpler. You probably don't need high-fidelity speakers to reproduce machinery clanking or engine noise. Run that bass-mid driver full-range, and connect up the tweeter with a 1uF cap in series. Add a 4 or 8 ohm resistor before the cap if that makes it too bright. That will start bringing the tweeter in at about 15kHz assuming it's 8 ohms, which might seem high - but the response shape of most tweeters is far from flat and the effective acoustic crossover point will be much lower.
|
|
Studio45 - Repairs & Building Commotion Soundsystem -Mobile PA
|
|
odc04r
Old Croc Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 5482 |
Post Options
Thanks(0)
|
That's all fine but part of a relationship is being honest. So you should have said it was a semi commercial design with charity affiliations in your first post, people wouldn't have minded but engineers are a cranky bunch at the best of times. Anyways if your engineer knows what a Laplace transform is he can figure out a crossover. The design of plant control systems have a lot in common with crossovers in terms of a transfer function and its associated gain/phase. You will have to provide quite a bit more data on your drivers etc if you want serious answers. Edit: Because I can't spell sometimes Edited by odc04r - 25 April 2017 at 10:46am |
|
markie
Old Croc Joined: 31 October 2005 Location: Sunny Liskeard. Status: Offline Points: 4570 |
Post Options
Thanks(0)
|
You'll find people on here are very helpful, but you really need to give us more information.
1). How much room have you got to fit the amp and speakers. 2). How are you going to power it, mains or batteries. 3) What sort of sounds are you trying to reproduce. |
|
If it's got wheels or tits it's gonna cost a fortune
|
|
Modeller
Registered User Joined: 03 March 2016 Location: UK Status: Offline Points: 31 |
Post Options
Thanks(0)
|
No problem Earplug, if that's what it takes.
A previous question on this website helped us produce a debut model that won a lot of incredible reviews, so with that success in the bag I wanted the relationship to continue. As we produce models that give very generous donations to industrial heritage charities (£12,500 so far), we need to keep costs down as low as possible, so asking the right enthusiastic people for as little financial outlay as possible is our aim. We all have our specialities, but crossover design is not one of mine or my electrical engineer's, who is more geared toward drive and supply systems. In assisting (in more than just general terms) you will help donate over £10,000 to another charity preserving Britain's proud and pioneering industrial heritage, but I'm not forcing you to do that.
|
|
Earplug
Old Croc Joined: 03 January 2012 Location: Europe Status: Offline Points: 7216 |
Post Options
Thanks(0)
|
If this is going to be some sort of commercial product, maybe you really need to find/hire someone to design the unit for you and get it done properly, rather than flapping around when you don´t seem to understand the very basics needed to get going. You´ve already been given plenty of good advice on how to get this done. Maybe do some reading: http://forum.speakerplans.com/newbie-essential-reading_topic14681.html |
|
Earplugs Are For Wimps!
|
|
Earplug
Old Croc Joined: 03 January 2012 Location: Europe Status: Offline Points: 7216 |
Post Options
Thanks(0)
|
I´ve never actually used any of those, but I presume that they do come with the filters built in. The blurb seems to indicate that it does, but who knows. Maybe send the seller a question. Edited by Earplug - 21 April 2017 at 3:29pm |
|
Earplugs Are For Wimps!
|
|
markie
Old Croc Joined: 31 October 2005 Location: Sunny Liskeard. Status: Offline Points: 4570 |
Post Options
Thanks(0)
|
If you don't need high fidelity why not use a simple full range driver, which will eliminate the crossover entirely.
If you include a sub driver the necessary crossover components will inevitably be big. If you want some extra high end then use a mid driver plus a piezzo tweeter. Piezzos don't need a crossover, just a resistor in series. |
|
If it's got wheels or tits it's gonna cost a fortune
|
|
odc04r
Old Croc Joined: 12 July 2006 Location: Sarfampton Status: Offline Points: 5482 |
Post Options
Thanks(0)
|
There is no getting away from a little bit of measurement and maths required for best results vs least effort. Although just taking values directly from spec sheets would do it.
Read this page thoroughly first of all, it might answer quite a lot of your questions: http://sound.whsites.net/lr-passive.htm |
|
Modeller
Registered User Joined: 03 March 2016 Location: UK Status: Offline Points: 31 |
Post Options
Thanks(0)
|
Thanks Snowflake, but I'm afraid that means not a lot to me at the moment. If you could start from the basis I know nothing at all. I have designed my own cabinets in the past, but I've used off-the-shelf crossovers or salvaged units and bought drivers to suit. This is a ground up design and I'm free to choose components suitable.
I need an unpowered unit that is very small – to fit in a model – that can separate the bass frequencies from the mid/highs at the point where the mid/high drivers are effective. How do I work out which components I need depending on the switch to the next driver? If, for example, I need the switch at approx 8kHz, what do I need to achieve that and what would the wiring diagram look like? I can then get it produced at my factory. Thanks in advance and apologies for my total lack of knowledge. Steve
|
|
snowflake
Old Croc Joined: 29 December 2004 Location: Bristol Status: Offline Points: 3122 |
Post Options
Thanks(0)
|
if you aren't worried about high fidelity just run the mid driver full range - it will roll off by itself at some point and putting high frequencies through it won't do any damage. put a capacitor in series with the tweeter and change the value till the tweeter rolls off at approx the same place as the mids. even a decent polypropylene cap of the correct uF value will be pence rather than pounds. |
|
Post Reply | Page <1234 5> |
Tweet |
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |