1kW MOSFET amplifier

[AudioFreak]

OOPS! sorry about that. I just realised the error i'm not thinking straight at the moment (I had a 4 hour Maths exam today). All drivers should be wired same phase. Thanks for the head's up MrFeedback.

[mrfeedback]

Hello AudioFreak,
Forgive me if I am wrong, but my understanding is that to cause an output from the horn, the drivers need to be electrically in phase, so as to cause a net compression or rarefaction in the cavity that supplies the horn.
If the two drivers are electrically out of phase (inverted) then there will be no net compression or rarefaction in the enclosure, and no net horn output.
Quite simple really.
You can't get out of this one !.

Eric.

[mrfeedback]

Hi again AudioFreak, your apology is gracefully accepted.
You posted while I was composing, so mine got through needlessly.
Hope you did good in your exam.

Regards, Eric.

BTW - Whereabouts in Qld are you from - I have spent most of my life in Brisbane, and last 10 yrs here in Perth.

[Brett]

The horn at the top of the page won't work. You want a very small, not large enclosed cavity (throat). the energy output by the drivers will dissipate in the large enclosed volume and dribble out the horn appendage, which won't provide any acoustic "gain".

Look how an expert (Tom Danley) does it with a pair of 12" custom drivers. These are designed to be used as half space loaded horns in groups of 6 a side and put out 149dB.

http://www.prosoundweb.com/lsp/

The flare is truncated because it's designed to fit standard truck pack dimensions. Build it as it is, and then add another flare till you reach full mouth size, at a rate of double the cross-sectional area every 26"

This is probably the best large capacity bass horn in existence, driven by a magnetic motor. When I can get the motors, I think a pair (eq'd flat to 20 Hz) would be fine in my living room.

[peranders]

Excuse me... what are we talking about really (here at the end)? This thread is totally flipped out. (Am I boring?) Seriously, what are the topic? Is it the Holton amp or 7200 W amps, horns or what???

[mrfeedback]

Even Kilowatt is not sure what he is talking about !.

Eric.

[EnvisionAudio]

I can hear to about 17kHz, and I'm only 16, which always helps in the hearing department.

I stopped paying attention when my guesses that "he can't be older than 20" were confirmed. Most 16 year olds can do ANYTHING - no one can disprove them. They are just about to buy everything they need to do the job - and in mass quantities.

An easily identifiable trait.

Oh, and by the way, yes I was building amps at age 16 (I'm 26), but they weren't 7200W because I knew my limitations and I respected others' advice. Remember that, and you'll be respected as well.

Aaron

[Kilowatt]

Hey that's that LAB horn everyone was talking about. It's nice to have plans for it. The explanation of why I need a small cavity seems reasonable (I should have thought of it myself). How big should it be? Would it still do what I want it to?

Anyway, peranders, this thread is about my big hifi/PA system project. First, it envolved Holton high power amps because I was going to use that design, then it envolved high voltage 900W amps because that's what I wanted to use, then everyone tried to talk some sense into me at the height of that discussion. When that was resolved (I'm not going to use 900W HV amps, just 450W & 225W into 2 ohm amps), we started talking about speakers, now more specifically bass horns and ways to get car subs to work outside because of their sweet Xmax that I want. I never bothered to start up in the loudspeakers forum, but maybe I should and just use this thread for amps and general discussion about the system. It is getting quite long and hard to catch up with, after all. Quite confusing for some I imagine.

EvisionAudio, I'm not "just about" to buy everything I need, far from it, there's a lot of planning to do. Have you ever built a 450W amp? Thought so, that's what I'm doing too, I'm just building more of them. Do you think I can't? I'm doing it this way, because I can't "do anything" and I completely rethought this thing because it was rediculous, and I have limitations, just like everyone else, but even more limiting. If I didn't respect others' advice, I wouldn't have. What advice have I immaturely ignored?? They say you shouldn't have to lie to make friends, but with agists like you, I should have. I'd probably have a lot more respect if you thought I was 30, I'd probably get better help. I just want to build a 7200W outdoor hifi system, not so crazy if you think about it.
By the way, AudioFreak is only a couple years older than me, for example, and look what he's done. You'd think he was as old as you, now quit your stereotypical grumbling, I'm not trying to do the impossible (I bet you couldn't tell me why this is impossible, and people have one it before) just to prove you wrong, rather, I'm trying to work with people to get it done.

[trwh]

Hi Kilowatt

I’ve been following your thread with interest for a while now, and what you’re doing sounds very ambitious. Here’s my input - maybe you’ll listen to me because I’m nearer your age

[I’m 18 and I do some work for a local sound hire company (for beer money!) and I’ve been tinkering with HI-FI since I was around 14 - I love it!]

Here are my points:

1) 7200W is a HUGE amount of power. I’ve just negotiated a FOH sound engineering job at a blues/classic rock gig for 200 people, and we’re only using 2000W. All the systems I’ve helped set up, run, and strike have been modestly powered; the biggest I’ve been involved in was for a 500 person event at my school, and we only used 4000W. I was doing FOH that night too (a slightly less discriminating audience, though!) and I never felt short of power. Remember, with a properly set compressor/limiter you can run continuously a system near its limits and still get plenty of clean power. So where is this 1000 person crowd you’ll be playing to?

2) Unless you are insanely rich you don’t have the money to build these amps and speakers. I couldn’t save up enough money for a system of this scale if I didn’t go out for my whole time at uni! And how are you going to pay for the wiring looms / flight cases / transport hire / active crossovers / limiters / balanced audio source, etc? Have you even considered these things? (You _were_ going to use a limiter, right?).

3) I know you want to have a system to play loud and impress your mates. That’s fine - I have a “party” system that I built which I hire out cheaply to friends. It consists of a 100W per channel TDA7250 based amp with a Rod Elliott limiter, driving a pair of 100W 12” full range PA cabs I picked up cheaply as end-of-lines (equiv of about $150 each). The cabs are rated at 96dB/1W/1m, and, trust me are PLENTY loud enough to fill the largest of living rooms with really loud dance music (noise?). Maybe you should consider something on this scale, but whatever please don’t waste your money, and remember to have some fun!

4) Careful of your hearing. I used to listen to a lot of loud metal when I was younger, and I regularly go target rifle shooting. At only 18 I suffer from some hearing loss and intermittent tinnitus. So if you do get your parents to mortgage their house to pay for this system, please wear the appropriate ear protection! If you’re considering operating a large PA system regularly, (I don’t know what you think you mean by a “HI-FI PA”, BTW) you need a set of musician’s earplugs, which will involve a pair of custom ear moulds and various attenuator attachments. They’re pricey but definitely worth it, and hey, you’re obviously rich anyway

I mean this all in good faith. I hope I’ve helped make up your mind (hint: get some earplugs and build a low-cost modest and robust system for parties).

See ya,
TRWH.

[Kilowatt]

First of all, I listen to everyone here, age doesn't really matter, in fact, the older guys here are obviously more experienced and wiser.

I'm not rich, on the contrary, I'm almost the opposite. I probably won't be able to get enough enough money to build more than a few channels of this system any time soon, if that. It's bad enough paying for my Leach amp. I'm hoping that I will be able to raise the money for the whole system someday though. I'm figuring it will cost about $10,000, but it might end up being alot more. I have friends who make that in a couple summers and blow it all at once on dirtbikes and snowmobiles and stuff, but if worked like that I wouldn't have a spare second to work on anything. I make money by mowing lawns, building speaker boxes, and I'm going to start making car amps if I can find either ready-made or detailed plans for switching supplies. I'm thinking 4x modified project3A (w/current sourse, diff. degeneration resistors, protection circuit, etc.) Haven't figured out a cooling scheme for 'em yet. It won't be easy to get the money, but I just might be able to come up with it in the next few years.

Yeah, it's a bold project, but I'm in it too deep to escape now. For all you other young audiophiles, do something like this at your own risk; you'll be critisized, ridiculed, not respected, dismissed as a lunatic, but you can't give it up without looking like a quitter once you start talking about it. It's like joining the mob.
I have no choice but to press on. But it won't be a waste of money.

Earplugs are a must if I'm fairly close to this thing, of course. But no one will be THAT close at full volume. I'm not sure what 150dB does to someone, but it can't be good.

P.S. This ain't no party system, I've got my watercooled Leach amps for that