Need some guidance

[BlackHatBrigade]

I've been lurking around the DIY forum and have really liked what I've seen. I think I got the DIY bug after building a car system for my 240sx. Amazing how something can start out as a $40 stereo upgrade and end up being a $800 project. At any rate I'm hooked on it and after stumbling across DIY audio for home systems I think I'm gonna be in trouble.

I'm interested in making a couple setups for my parents. I've got one Living Room setup to do and then one outdoor kitchen area to do. I've got to be a little price conscious, however I've already got the visual part figured out (Linux MCE setup for the win :T ). Now I've got to figure out how to make the audio really impress them. The only thing I have so far is a S/PDIF which has the audio from the MCE setup. The projector is being run by a HDMI cable. Pretty much everything from the receiver to the speakers needs to be figured out.

I've looked over the MTM setups and like the price point on them. I figure that will probably have all the audio quality I'd need and be a great way to start. I also looked over the suggestions on receivers and like the Onkyo 605, both for price point and being able to support HDMI and S/PDIF. I don't believe the extra features will mean much for me because the source will only be able to do Dolby Digital (not DTS). But if I'm wrong on that being the only benefit due to extra features, please let me know.

Now, the questions. Going back to the DIY MTM setup. I have searched and read more highly technical speaker info than I really cared to (I may have to check and see if my eyes are bleeding now) and I can't find anything about how to power a DIY array? (is that the right word for it?) I'm also not terribly sure if the crossover changes the resistance of the speaker to the point where I need to factor that in. I sat down and tried to figure out how you'd hook up something like the MTM setup to the Onkyo and the only thing I can figure out is that I'd need an amp. Unless I'm missing something really basic here. But it seems to me like that would be a big waste. an Amp only really needs a small signal right? Why run it through a nice receiver, which should be able to power smaller setups just fine, to an amp which doesn't need that strong of a signal? Any help on how you go about powering a DIY setup like that would be greatly appreciated (or even a link to a good writeup on it).

That was really a pretty open question, and I apologize for that. I'm just used to working with car setups which don't have fussy receivers that can't deal with a change in ohms.

The other question is if someone can point me in the right direction for a 5-7.1 system that would fit the bill of about $1000-1500. I also have a outdoor kitchen area to build for, but I think if I can make it through the living room setup I'll be better able to decide how to do the outside one :scratchhead: Like I mentioned, I'm thinking the MTM setup would fit the bill. Provided I don't have to do something obscene like buy a bunch of amps on top of the receiver to power them. I'd like to do something a little special with a sub, but something tells me I'm going to run out of money before I get to do anything special with that

[BlackHatBrigade]

Maybe somebody can clarify a little detail that is escaping me. I keep insisting I'm just missing something basic and I'm aggravated I can't figure it out on my own.

I'm going to take the MTM DIY setup as an example (I looked over that thread several times and couldn't find my answer there). I'm going from memory, but I think the speakers were 2 of them at 100w @ 8ohms and a tweeter 70w @ 4ohms. I believe those were RMS specs. Now, with my car audio I would try to figure out what I need to power that. Since I'm looking at the Onkyo 605 I have 7 channels 90w @ 8ohm each. (I think it has 7 channels) Since I want surround sound I'm thinking that I'd only want to spare one channel to run that setup (starting to think that's not possible, or at least ill advised). So to get that speaker setup to 8ohms I was thinking of doing the 8ohm speakers in parallel then making the tweeter in serial with the 8ohms.

The 8ohms would turn into 100w @ 4ohm when in parallel (right?)
Adding the tweeter in serial would make the power needs 170w @ 8ohm (right?)

Which means the end power requirement would be 170w @ 8ohm for the MTM? I have no clue how the crossover affects this, if at all. I really didn't want to get into speaker/cabinet design. I like the idea of being the "monkey see, monkey do". But I also want to make sure I'm powering the setup well enough.

Of course, I have no clue if I'm just turning this into something way more complicated than it actually is, or I'm just not grasping it. I noticed the MTM setup already has a wiring diagram which seems to manipulate the resistances going across the speaker anyway (I'm guessing that's how a crossover does it's magic). Which leaves me back at square one... confused

[BlackHatBrigade]

This must either be a really stupid question or a really tough one...

[draganm]

The other question is if someone can point me in the right direction for a 5-7.1 system that would fit the bill of about $1000-1500. I also have a outdoor kitchen area to build for, but I think if I can make it through the living room setup I'll be better able to decide how to do the outside one :scratchhead:

Seems like your questions would be better answered if you spread them around in different area's? I doubt anyone here in the "starting block" is going to know anything about building speakers or matching amps to them.
AFA simply buying a nice 5.1 set-up, one my favorite places is Audioadvisor as they sell some nice mid-fi stuff at deep discounts and close-outs. Usually you can save at least 50% off retail. A pair of the Athenan LS-300 towers, the LS-110 center, a pair of surrounds, and a Cambridge receiver will be a nice match-up and set you back no more and $1100.

http://www.audioadvisor.com/prodinfo.asp?number=ATLS500

http://www.audioadvisor.com/prodinfo.asp?number=ATLSC100

http://www.audioadvisor.com/prodinfo.asp?number=ATASR1.2

http://www.audioadvisor.com/prodinfo.asp?number=CA540RV2

[BlackHatBrigade]

Thank you so much for the advice. I'm actually starting to lean toward something like that. Also, I greatly appreciate the site referral. I've been having trouble find a good home audio site.

I guess I just thought since no one mentioned it in the DIY section that it was something that was stupid easy and someone should know about it before even looking at building a setup like those. I did notice that the setup you recommended does not take the wattage up to the speakers rating. Is that common for home audio? I know in my car audio setups I always try to amp the speakers right up to their max rms rating. That would probably explain some of my issues in understanding the home audio amp situation.

[draganm]

I guess I just thought since no one mentioned it in the DIY section that it was something that was stupid easy and someone should know about it before even looking at building a setup like those..

I have looked at DIY set-ups but truly superb uadio in a home environment is insanely complicated. While quite a few folks could easilly handle building a nice cabinet and putting pricey drivers in it the magic of a basic 3-way speaker is in the cross-over behind it. It has to do wtih timing, phase coherence, linear frequency response, an impdeance response that's as flat as possible, etc. I think you could easilly earn a 2 year college degree on just sepaker design if they actually offered it. Most beginners who tackle this will usually use someone elses crossover butthe rpoblem for this IMO is you don't really nkow what your gettitng until you turn it on. I have lost money in the past buying speakers sight-unheard and will never do that again without a live demo.

I did notice that the setup you recommended does not take the wattage up to the speakers rating. Is that common for home audio? I know in my car audio setups I always try to amp the speakers right up to their max rms rating. That would probably explain some of my issues in understanding the home audio amp situation.

This is ideal if you can afford it, but stand alone amps that can truly put out a continous 150 wats per channel are going to cost $500. each and that's used. I'm running a pair a Monarchy audio SM-70 pro's I bought used and my solution was to still have receiver in my system and uses the mono-blocks for the mains only. Reason being is that with Denon driving all 5 (large) speakers and volume set high I actually clipped the LEFT/front one night pretty badly.
However, if your setting this up for your folks I doubt they will ever crank this system up the point of actually needing stacked amplifiers. Another possible alternative to the receiver is a stand alone pre-amp/multi -channel amo combo from Emotiva audio but even then your lookng at $K for just the pair.

[Paul H]

BlackHat,

Firstly, the extreme vast majority of speaker designs in the DIY section of this forum can be powered directly by an amplifier, or a receiver - which has built-in amplifiers. This is because the speaker designs typically use passive crossovers, similar to the crossovers in the extreme vast majority of retail speakers.

The wattage ratings for individual drivers are not terribly important for home use. This is because most home speakers will be too loud (at typical home listending distances) and/or distorted long before they exceed their wattage rating.

You are correct in that two 8 ohm speakers in an MTM connected in parallel will result in a 4 ohm nominal load, but this is oversimplifying as the resistance (impedance actually) varies with frequency.

The speaker rating is not a "need" but rather a measure of how much continuous wattage the speaker can take.