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Multi-Way Conventional loudspeakers with crossovers

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Old 12th August 2008, 03:04 AM   #1
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Default let me know if this is plausable...

I've been considering building a sound system for my bedroom. this is what i've been looking at recently. let me know what you think. oh yes, and i'm very much a beginner, so i don't expect the best. it is a 2.1 setup with two way satellites.
for the woofers...http://www.partsexpress.com/pe/showd...number=290-373 in a .08 cu ft enclosure
for the tweeters...http://www.partsexpress.com/pe/showd...number=270-182
the xover...http://www.partsexpress.com/pe/showd...number=260-174
the sub amp...http://www.partsexpress.com/pe/showd...number=300-805
i have a 120watt stereo amp as well
the subwoofer is two of these (isobarik) in a 1.5 cu ft box...http://www.partsexpress.com/pe/showd...number=290-357
i have a few questions, and i'll get a winisd pic up soon. just let me know if this is possible. i'll want to use it for listening to modern rock/alt. and soundtrack.
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Old 12th August 2008, 04:25 AM   #2
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k here's my questions. since i listen to rock, will the silk tweeter and poly woofers be um... not as good as metal? and does the plate amp have a highpass as well as a lowpass xover?
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Old 12th August 2008, 05:48 AM   #3
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One small drawback to the crossover, though I'm sure others will say there is more than one.

The crossover is only a high pass, in other words, it only acts on the tweeter. You depend on the natural roll off of the woofer to act as its crossover.

The Goldwood's look appealing, but there are no frequency response graphs for them, though you could try to get them from Goldwood. Without a frequency response graph, you don't know if there are any nasty peaks above the working range that are going to mess things up.

Actually, there is a graph for the 4" woofer as can be seen here -

http://www.partsexpress.com/pdf/290-373g.pdf

Notice the peak around 5,000hz to 6,000hz. If you don't want that peak to substantially color your output, then you need to make sure the crossover is low enough that this peak is insignificant when it occurs. I would say 2khz to 2.5khz, but that is just a guess.

In short, you can't use the crossover you selected.

You need something closer to this -

http://www.partsexpress.com/pe/showd...number=260-140

http://www.partsexpress.com/pe/showd...number=260-144

A more precise, but generic, crossover can be designed at the precise frequency you want to cross at.

Now we have the second problem, the tweeter has a rated low response of 2,000hz, so you need to crossover above 2,000hz. However, the tweeter also has a moderately high power rating. So that means you can probably get by with a 2.5khz crossover at 12db per octave.

Here is Part Express Crossover Selector Guide -

http://www.partsexpress.com/resource...tion-guide.cfm

Match the impedance of the speaker, the selected crossover frequency, and you will find the components you need. Though I don't think the low pass goes high enough for you.

So, we need another source.

Second Order (12db/octave) Two-Way Crossover -

- Linkwitz-Riley or Butterworth

http://www.apicsllc.com/apics/Misc/filter2.html


Next, just to educate yourself, you need to read this, -

http://www.partsexpress.com/resource...sover-help.cfm

and more importantly, this -

http://sound.westhost.com/lr-passive.htm

If you have WinISD, resist the temptation to tune the cabinets with a huge bass peak. That peak doesn't come without a price. A slight peak to bring you -3db response as low as possible is OK, but excesive peak in the bass will cause problems.

Before anyone freaks out about the generic crossovers, this is an economy system. The 4" woofers are $8 each, the tweeters are $10 each, and the subwoofers are $16 each.

Whoops, I just notice you selected DVC (Dual Voice Coil) subs, did you mean to do that, and why?

That is a level of complication you don't need.

Try this -

Goldwood GW-8028 8" Butyl Surround Woofer 8 Ohm @ $17.50 each
http://www.partsexpress.com/pe/showd...number=290-355

Frequency response: 35-2,500 Hz

which is better low response than the sub you originally picked.

There are more complications like L-Pads and Zobel networks, but let's leave those for later.

Steve/bluewizard
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Old 12th August 2008, 05:53 AM   #4
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Quote:
Originally posted by thatotherguy
k here's my questions. since i listen to rock, will the silk tweeter and poly woofers be um... not as good as metal? and does the plate amp have a highpass as well as a lowpass xover?
I would say you want to stay away form 'hard cone' woofers, they tend to have nasty break up above the working range that complicate crossover design.

Find woofers with the fewest complications possible.

If the plate amp has speaker OUTPUTS, then likely it has a high pass.

Steve/bluewizard
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Old 12th August 2008, 12:13 PM   #5
sreten is offline sreten  United Kingdom
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Hi,

Oh dear, nightmare waiting to happen.

The Goldwoods do not look appealing, they look appalling .....

For the speakers look no further than : http://www.zaphaudio.com/ZBM4.html

Noting you need an AV amplifier for proper filtering, the satellite
"filters" fitted to plate amplifiers do not work, to be avoided.

The plate amplifier is possibly too powerful for the application.
Consider :
http://www.mcmelectronics.com/product/50-6272
Good documentation and features, note continuous phase.

Silly's 1st Sub -- 8" MCM 55-2421
Cheapy Passive Sub?

Contains some useful information.

Avoid the Goldwood subwoofers, too much of an unknown quantity.

/sreten.
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Old 12th August 2008, 05:25 PM   #6
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kk thx for all the input... just remember as it fist was, it totaled $230 after shipping. this is very much a budget build. thats why i have the goldwoods and generic xovers. i do see the points though. i think i may be confused a bit about the sub, does the plate amp have single or two channel output?
so obviously im going cheapo on the xovers. i've noticed that buying the components separately can add up. what do you think about this one?http://www.partsexpress.com/pe/showd...number=260-144
i guess alot of this is beside the point, because i've about decided to spend my money on other stuff. (or save)

just to let you know my present sound system is a total mess. it sounds good, but technically its a mess.

thx for the info again. im still considering it, maybe just the sub(nice plate amp on sale!). any ideas?
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Old 12th August 2008, 06:13 PM   #7
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I too was thinking that maybe the Sub Amp was overkill for this system, but my posts tend to be so long and rambling, that I didn't want to deal with every issue in one post.

There is a 75% difference in price between the two (or $60), the Amp Sreten suggests has plenty of real power for a small system like this. And as he also points out, it is probably better documented. The website has links to a technical data sheet and an owner's manual in PDF format which you can view before you purchase.

As to the Goldwood speakers, that is a tricky business. I really want the Goldwood speakers to be good, and the fact that they are in business and stay in business is some small tribute to their speakers. Yet, it bothers me that they don't make a technical datasheets readily available for every speaker they make. I'm guessing if you email them, you might get something from them, but it shouldn't be that hard. The data should be readily available from sellers and from the manufacturer's website.

When ever I consider making speakers using Goldwood, I am always stopped by that fact that I don't have enough information to make a decision about whether this speaker will work for me or not - no datasheet.

In your case, for a low budget system, they will probably work fine. Your underlying design is pretty straight forward, and using the bass speaker as a sub means, we will only be using one small somewhat easy range for the speakers.

Don't be totally discourage because of our hesitance regarding Goldwood. They do make speakers and they will certainly work, and if your budget is really hopelessly strained, then they will probably work for you.

But, if you can stretch your budget upward, new and better possibilities open up for you.

For the crossovers, if you can't find one at a 2,500hz, one can be easily built from components.

You are going to need two coils for each crossover, and they are in the $5 to $8 each range.

Two capacitors for each crossover at $2 to $4 each.

Two resistor for each crossover @ about $1.25 each.

That's roughly $18 each.

So, $18xo + $8w + $10t = $36 each speaker without cabinets. If you could find the correct off-the-shelf crossover, you could maybe save $5.

The Zaph budget speakers suggested are about $40 each, though you would have to verify that at current prices.

But consider this as an alternative - Tang Band Full Range speakers. They are roughly $20 apiece and they only go down to about 100hz, but they are very flat from 100hz up to 15,000hz. So, that saves you the expense of building crossovers.

Some examples to look at -

These speakers are relatively flat across 65hz to about 15khz -

http://www.partsexpress.com/pe/showd...number=264-818

http://www.partsexpress.com/pe/showd...number=264-817

http://www.partsexpress.com/pe/showd...number=264-820

Plus, they look cool.

Don't be discourage, even for the experts, building speakers is always a struggle between seemingly infinite choices and decisions.

If you would like, give us a realistic budget estimate for the Fronts and the Sub (separately), and give us some time to think about it. We may be able to come up with a better solution that fits your budget.

Again, don't be discouraged. People here are usually spending a $1,000 or more on home-built speakers, but that doesn't mean we don't know what it's like to be struggling on a tight budget.

to your core question - is this plausable? The answer is Yes, with the changes I've suggested, and you can save $60 that can possibly go to better front speakers, if you get the plate amp that Sreten suggests.

Again, don't be discouraged.

Steve/bluewizard
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Old 12th August 2008, 06:15 PM   #8
sreten is offline sreten  United Kingdom
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Hi,

Given the time and effort it takes to make nice boxes saving a few
dollars on poor drivers and crossovers is a total false economy.

FWIW for a bedroom I'd forget about the subwoofer completely
and build a decent pair of $200 speakers for your 120w amplifier.

They will sound vastly better than your plans.

e.g. for ~ $175 : http://www.zaphaudio.com/BAMTM.html

The floorstander does not need a subwoofer.

/sreten.
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Old 12th August 2008, 06:36 PM   #9
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Here is another thought, I'm not much of a Subwoofer guy. I go for straight up stereo.

Consider as an alternative losing the Sub, and plowing that money into better main speakers. If your budget is about $200 to $300, that would buy some pretty nice and proven design MTM's (Midbass, Tweeter, Midbass). Look on the Zaph site for example. These are so popular that they are available in preconfigured kits with custom designed crossovers.

Example -

Dayton A532C Speaker Kit Cherry @ $169 each
http://www.partsexpress.com/pe/pshow...TOKEN=34716950

From my understanding this is a complete speaker ready to assemble and includes the cabinets in cherry, though black is also available. You can also get it with straight sides or curved sides.

Dayton A732 Speaker Kit - cherry/black/maple @ $189 each
http://www.partsexpress.com/pe/pshow...TOKEN=34716950

Dayton RS722 Speaker Kit - black/cherry/maple @ $219 each
http://www.partsexpress.com/pe/pshow...TOKEN=34716950

Admittedly that is pushing your budget, but the results are certainly impressive, and while the cabinets are not 'pixie' cabinets they are still reasonable compact.

Also, you could probably cut the cost nearly in half by building the cabinets yourself; keep that in mind. I think they all use the standard Dayton 1 cubic foot cabinet which is about $100 each.

Some of these are documented in the Parts Express DIY Project area, and I'm sure Parts Express would sell the complete kits including the crossovers minus the cabinets.

I'm just saying consider the possibilities.

Steve/bluewizard
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Old 12th August 2008, 06:42 PM   #10
peter_m is offline peter_m  Canada
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Silk or metal tweeter is really a moot point since design of the crossover is way way more important. Also in this case, quality of the tweeters you mention is problematic. The off the shelf x-over is also a no-no.

I second and strongly suggest you consider Zaph's ZBM4 design or his BAMTM design

Good luck,
Peter
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