Amp powerful enough?

[megamuel]

How do I know if my amplifier will have enough power for the speakers I am building? I'm using the Dayton RS225S-8, Tang Band W4-654SE, and Dayton DC28FS-8 drivers and my amp is the NAD C 320BEE. I have a feeling I am going to need more power! Cheers!

[Gir]

It will be enough power for normal listening volumes, but nothing really loud. If we assume 80dB sensitivity, then with 50W you'll have roughly 96-97dB. If you know what kind of overall sensitivity you're going to get at 1W, then every time you double the power, you increase the volume by 3dB. So if your volume is 80dB at 1W and you increase the power to 8W, then you just increased by 9dB (2W, then 4W, then 8W, 3 dB each time).

Hope that helps

[jeff_free69]

not sure what the rating on that NAD is - 40 - 50 W/Ch? NAD always had a reputation for a good amount of headroom. eg +3Db for short peaks, giving significantly more power (I currently have the 100W/ch power amp, and used to have the receiver years ago - i think it was about 40 W/ch)

- so the question is how LOUD do you really need it?
in theory, starting at 86 db @ 1 watt (@ 1 meter) ,
My rule of thumb is to
Add 3db everytime you double the power &
Subtract 3db each time you double the distance

So 32W gets you to 101db @1 meter, or 95 db @4 meter, with plenty of headroom left - and thats pretty loud for a living room!

[Gir]

I guess it also helps to ask if there's a subwoofer it crosses over to and if you use this for HT or mostly music. If it's HT you might want a bigger amp if you really like the "full experience". If it's music you're fine. Also, reading some more on that amp it looks like it has some really good headroom for quick peaks, so running it at a high volume doesn't seem like much of a risk as far as clipping goes.

[megamuel]

[QUOTE=jeff_free69]not sure what the rating on that NAD is - 40 - 50 W/Ch?QUOTE]

Its 50W per channel. Thanks guys, I just wanted to make sure I wasn't going to blow anything thats all! I'm new to this speaker building and I haven't got a clue what I'm doing but I'm enjoying the whole designing, planning, problem solving aspect! Can't wait to start building now, I'm sure that will test my patience! I'm planning on using these for music use only but I've already started thinking about building a subwoofer next and then maybe some surrounds for a HT set up.... Oh no I'm getting carried away!

[servicetech]

High quality amps tend to handle peak loads really well. I remember way back in the 80's I owned a Proton D940 rated at 40w/channel. It blew away the 100W/channel Pioneer amp it replaced.

[megamuel]

Is mine a 'high quality amp'? It actually has a soft clipping feature that can be switched on to protect the speakers so I may try it with that switched on

[joecarrow]

From what I've heard,Nad's not bad, but whats the actual minimum impedance of your speaker? Depending on the crossover, you could damage the amp without even going loud- mostly if it presents extremely low impedance at some frequency. If it dips too low at some point, it'll limit how loud you can go before the amp is the weak link. It's about amp quality for short bursts, but also crossover characteristics for how easy they are on the amp.

[littlesaint]

His amp is stable to 2 Ohms. NAD builds some of the best amps out there when it comes to high current applications and dynamic headroom.

[megamuel]

I will actually be using a pre-assembled crossover from parts express:

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=260-152

Sorry!!! I know these aren't very popular around these parts but I think that designing and building a crossover is far beyond my skill level for the moment so I'm doing this project to try and learn a little as well as have some fun and I hope to build my own crossovers in the future! The pre-assembled crossover crosses at 500/4k. It was recommended to me by parts express so I hope it will at least be ok? I understand it won't be as good as a custom built crossover but hey.

By the way, parts express is great, but I think they should open up a branch here in the UK! There is nothing like parts express here which means I have to pay a lot extra for shipping! I just bought some parts for about £50 ($100), the shipping was about £30 ($60) and then I had to pay a customs fee of £28 (nearly $60) so spent more on getting the parts over here than the value of the parts! There are a few shops here but nothing on the scale or standard of parts express :M This is going to be an expensive hobby!

[Gir]

If you haven't already purchased the pre-assembled crossover's I highly recommend you don't. If you can stick a wire with a hot stick then you can assemble a crossover. Just use one of the designs from the Mission Accomplished forum. My friend had no idea how to read a schematic (didn't even know what the line were 8O), and he had no problem assembling the crossovers.

[megamuel]

Too late I bought them ages ago. Yes I could probably produce a crossover from a schematic but I wouldn't have the first idea of how to design the crossover. Where to cross them over and what components to use to do it? And I don't think anyone would want to design it for me! I'm quite happy doing it this way for my first project as long as the speakers actually work I'll be happy! I'll look into doing my own crossover next time!

[Xander]

Too late I bought them ages ago. Yes I could probably produce a crossover from a schematic but I wouldn't have the first idea of how to design the crossover. Where to cross them over and what components to use to do it? And I don't think anyone would want to design it for me! I'm quite happy doing it this way for my first project as long as the speakers actually work I'll be happy! I'll look into doing my own crossover next time!

The schematic being referred to is a schematic of the crossover, already designed for the speaker taking into account the driver characteristics, baffle configuration, and even placement in a room. That's why building a speaker already designed (like the designs in the mission accomplished section or from sites like Zaph's) is so easy. It's all done for you, most even have a complete bill of materials. The only designing you have to do is laying out the pattern on the MDF It's just as easy (or easier) then choosing your drivers and a prebuilt crossover, and the results are much better. Just something to consider next time. Have fun with your first build, you'll be doing more soon

Take a look at this site:

http://www.zaphaudio.com/index.html

Great designs for all budgets and goals

[Alaric]

NAD amps have mucho headroom , and are underrated for power. Just bear in mind , mathematical formulas don't tell where the distortion you can hear starts-and every speaker has it's own 'self-destruct' point. An 86db , theoretical , max is only on paper. You may be be able to go higher but probably should aim lower. My $ .02

[servicetech]

The main problem with premade crossovers is the don't compensate for individual drivers. The woofer very rarely will be at it's nominal impedance when running 500hz, it isn't unusual for an 8 ohm woofer to be 12 ohms @ 500hz. The crossover designed for an 8 ohm driver won't work properly. You could add a zobel to offset this if you know the woofer's specs. Another issue I've seen with them is they rarely use inductors with wire thicker than 18ga and the cheaper x-overs are still using electrolytic caps.

That all being said I'm still using the pre-built crossovers that I put in my speakers 15yrs ago. Back in the 90's crossover software didn't really exist and you had to calculate component values with a calculator or with a chart. Nowadays you can plug driver values into a software program and it will do the work for you. All my projects since then have had custom crossovers.

[megamuel]

Thanks for all the constructive criticism/advice. I understand what your all saying about the pre-assmbled crossover and I'll definately attempt building my own crossovers next time! If you guys were designing a crossover for the drivers I have chosen what crossover points would you choose? Or does this depend on many other factors not just the drivers? Based on the fact I will be using a pre-assembled crossover with crossover points at 500 and 4k are mt speakers going to sound awfull or just not as good as they could? Basically I'm just curious as to how much performance will be lost by choosing a pre-assembled crossover as to a custom built one? And from what everyone is saying I'm gathering that my amp isn't going to blow up or anything!!! By the way, where is 'CJD', he was nice to me last time

[joecarrow]

I'd say that the speakers will sound nowhere near as good as they could, but you still might be able to learn to love them. I'd advocate getting a good equalizer to correct for a few things. I had a horrible crossover that I designed myself, and I was able to get an enormous improvement with a software parametric equalizer. I was playing all of the music through my computer, though, so that's probably different from your situation.

[---k---]

Designing a crossover is about _MUCH_ more than just the "crossover points". Other things that the crossovers consider is zobels to adjust the impedance, sensitivities, and shape of the roll off.

I think the prebuilt is good for screwing around with. But, I wouldn't use it to impress your friends. With the quality of some of the Internet Direct (likely different in the UK), it is getting harder and harder to do 5x better for the $$ with DIY. I think will in-box testing and an optimized crossover, it isn't a problem. But the off the shelf parts don't go as far as they may have.

CJD is around.

[megamuel]

Nowadays you can plug driver values into a software program and it will do the work for you. All my projects since then have had custom crossovers.

Which program do you use? Are these very expensive?

[megamuel]

I'd advocate getting a good equalizer to correct for a few things.

Any suggestions? Do you have a link so I can see an example of what I should look for? Also by looking at the drivers and crossover are you able to make any predictions on where the speakers may be lacking, or is that purely down to listening and testing? Cheers.

[servicetech]

A good freebie

Which program do you use? Are these very expensive?

PCDC I'm sure there are better ones that have more options but I'm just using this free one for now. Easy to use, even for a novice and you can't beat it for the price :T

[---k---]

http://www.speakerworkshop.com/ -free, what CJD uses.