Mission HomeTheater

[ramchandra]

Hi Everyone

I am new to this forum and field. I am starting a project to build a complete home theater system. I have divide it in 3 phase: Phase 1 will be building speaker (5.1 initially). Phase 2 will be adding Projector and building screen. Phase 3 will be improving sound system by adding another 2 channel.

I have already stated reading some books on building speakers and forums for DIY projects but couldn't find anything that starts from basic. Therefore think to start this thread which will help lots of beginner to start and complete their first project.
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;b> Phase 1: Building Speaker ;b>
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I have decided to build 4 floor standing (3 way,1 tweeter,1 midrange,2 woofer) speakers, a center channel and a 12" subwoofer.

First thing is to select decent drivers. what should we looking for when we choose each type of driver.

[Hdale85]

Do you have any measurement equipment or knowledge of crossover design of any sort? Honestly you should pick a design already made and build that. Plenty of very good 3 way designs on this forum that would likely more then meet your expectations.

[oneplustwo]

I have exactly what you specify with my Zaph ZDT3.5 Left, Right, and Center plus the my 12" Dayton HF subwoofer. Would highly recommend this setup for not only HT but also your 2 channel. Although, to mix it up, you could try an open baffle 2 channel, which I also did... in the Sunflower XTs.

I imagine you may find that folks will recommend what they have! *ahem* So take my input for what it's worth!

[ramchandra]

I have looked at some completed diy projects but because I am in different country, I can't find drivers used in those projects. So I have to used other but similar spec drivers. Therefore I need to know, what I should be looking when choosing driver.

[Hdale85]

What country are you in, there are likely people here from the same country or know of companies that will sell the drivers you need and what not.

[---k---]

https://sites.google.com/site/undefinition/diy-faqs-provendesigns

https://sites.google.com/site/undefinition/diy-mfaq

https://sites.google.com/site/undefinition/diy-mfaq2

https://sites.google.com/site/undefinition/simulated-measurements

[limulus]

I have all the brand new drivers for the Dayton RS TMWW towers. I built the cabinets in 2007 and never finished them. I got tired of building speakers.

[Hdale85]

Tired of building speakers? Blasphemy!

[oneplustwo]

I'll take the drivers off your hands!

[ramchandra]

What country are you in, there are likely people here from the same country or know of companies that will sell the drivers you need and what not.

I am in india (City- Surat, State- Gujarat)

[ramchandra]

https://sites.google.com/site/undefi...-provendesigns

https://sites.google.com/site/undefinition/diy-mfaq

https://sites.google.com/site/undefinition/diy-mfaq2

https://sites.google.com/site/undefi...d-measurements

Not quite clear what you trying to say.

I am going use one of the existing proven DIY design for my project rather than creating my own. But I still need to have the knowledge of how I choose drive and most important how to read and build crossover from the schematic.


have found some good link for basic understanding of crossover

http://www.the12volt.com/caraudio/cross.asp

http://www.members.shaw.ca/loudspeakerbuilder.ca/crossover.html

[AdelaaR]

"proven design" & "choose driver" ... the two can not coëxist.
Why is it so hard to order drivers in India?
Tangband is closer to you than it is to me.

[Hdale85]

I have a friend in India and he did have to order his stuff from the states. It took months for them to arrive, and some of it was lost and customs are up there I guess. They don't have a large selection of OEM drivers over there apparently.

[---k---]

Not quite clear what you trying to say.

I don't mean to be a jackweed, but did you read the links provided? Have you spent time on this forum?

We're highly supportive of people learning how to design and build speakers. The traditional way to learn is to start with a pair of simple 2-way speaker with easy to work with drivers (read paper cone), model the box with Unibox, trace the manufacturer's FR plots, and use FRD to model the response. Designing a 3-way speaker and getting it to sound good is not a trivial task. Starting with an existing design and trying to modify it to work with completely different drivers is like starting from zero. Read the links provided and you will see this.

Building a proven design will teach you a lot of woodworking skills, crossover layout skills, and just general speaker building skills that are required. It is an excellent way to start. I'm more than willing to help with this. I can't help with designing a completely new crossover, but those that can will gladly help when they have time if you do the necessarily prerequisites.

I understand you're in another country and sourcing parts may be difficult. But throwing local available parts (which we don't even know which ones are available, so I don't know how we can recommend them) at an existing crossover and enclosure is a recipe for creating a child that only a mother could love.


There are nice people at PE's forum that will design simulate a completely new crossover. But, I'm guessing they're going to have problems knowing where to start also.

[ramchandra]

Does crossover linked with speaker brand (or something like that)? Doesn't it work in same way with any speaker as long as it has same spec?

I am trying understand how to read crossover schematic in order to build it rather than designing completely new crossover.

[BOBinGA]

Crossovers are built to fit the drivers, so you choose your drivers first and then make a crossover. You can't pick a crossover first and then just substitute any other driver you want. That won't work. There are some rare cases where you can substitute one driver for another, but driver specs are rarely close enough to do this. Only the crossover designer can tell if the differences are small enough to allow a substitution. Unless you have measurement equipment and have practice using it, I would not recommend changing anything in a proven design. That's why we are saying that you should copy an existing design exactly.

-Bob

[Bear]

Does crossover linked with speaker brand (or something like that)? Doesn't it work in same way with any speaker as long as it has same spec?

I am trying understand how to read crossover schematic in order to build it rather than designing completely new crossover.

To add-on to what Bob just said: it is not just the drivers, but the combination of drivers AND the enclosure/baffle. There are some parameters that you can change, but there are many, many of them that you can't. In some cases, particular manufacturing batches/series may not work exactly the same with a given crossover design due to variances in manufacturing tolerances and quality control.

You will get more depth in the links provided, above, to learn this.

Here is a quick summary of what you are basically assuming:
1) Textbook RLC circuits (highpass and lowpass filters) can be developed based upon some formulas from Wikipedia and the driver specs. Speakers made this way may sound good to you (the power of human psychology), but they really won't perform very well in an objective sense.

2) At some point, after you've failed with #1, you realize that you want to take real-world values into account. Congratulations, you now have to invest in measurement equipment and spend a fair bit of time learning how to measure. No, this is not a simple task. The good news, though, is that once you learn how to measure, the textbook RLC circuits come back into play and are more useful. You also start to become interested in HD, IMD and impedance curves. You may start to make decent, but not exceptional, sounding two-way speakers.

3) Having spent time playing with #2, you decide that you want to make the speakers from #2 better. You now start to pay attention to the target curves vs. the real-world measured curves of your completed speakers. HD, IMD and Impedance become more of an obsession. You start to learn about things like notch filters and shelving filters. Somewhere in here, you also learn about a guy named Siegfried Linkwitz.

4) Now you start going deep into the rabbit hole. You become obsessed with phase: phase alignment, minimum phase, poles and zeroes. Also, for some reason, your favorite letter of the English alphabet becomes the letter 'Q'.

5) Finally, you emerge from your chrysalis and realize that you can make make a coconut shell sound good if you just have enough parts. Unfortunately, you can't find said parts because all of your living space is consumed with test equipment, finished speakers, partially built speakers, speaker drivers, and your now beloved collection of exotic wood veneers.

The net effect: if you were really good in your undergrad circuits class, then you can probably look at the frequency response graph of the free-air and in-box drivers and the crossover schematic and start to work out what each leg of the network does without a meaningful dialog with the designer. Mostly. However, if you are not an analog-oriented EE, then you are essentially embarking on a variation of the maturation curve, above.

If you want high-quality sound reproduction sooner than the above, you really need to build a proven design. If you want help in selecting a design based upon your room and driver availability in your area, then this is a different question than asking how to read a crossover to help you select the drivers you want. They may seem like they are the same question, but really, they aren't.

[ramchandra]

Bob

Bear

Thanks, Understand, crossover is designed based on the speaker performance not exactly on spec.

Will try to find the same speaker but don't think i will find any.

BTW, have any one heard about "Bolton". I have heard that it's available in india.

[AdelaaR]

Some guy on here lives in South Africa and had all the parts delivered to him.
I don't know what it cost him exactly, but why isn't this an option for you?

[cjd]

I'm not sure the cost of importing, but I've ordered stuff from India and it's been reasonable cost-wise. Though it's mostly movies, and we usually have to order around 10 for shipping costs to be worthwhile.

Technically it *is* on spec, but you have to realize that spec is not ever flat. You might say "8ohm driver" but if you look at the impedance, it varies significantly with frequency - and, of course, frequency is not even close to being perfectly flat either. If two drivers had exactly the same frequency response, impedance curves, dispersion characteristics, size, you could interchange them.

You might be able to find some local component that happens to be manufactured at some brand-name plant - same stuff but sold grey-market locally... but it's not probable.

You might have better luck working with someone (friend, family) that either visits the US on business, or an someone working here visiting home... they can bring you some toys as a gift.

[ramchandra]

Some guy on here lives in South Africa and had all the parts delivered to him.
I don't know what it cost him exactly, but why isn't this an option for you?

It is a option if delivered by Fedex/DHL (or any international courier service) but that coast a lot. On PE ordering for dome tweeter (around 3kg) coast $80.