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Multi-Way Conventional loudspeakers with crossovers

Questions about speaker building
Questions about speaker building
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Old 3rd July 2018, 12:04 AM   #11
Galu is offline Galu  Scotland
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Join Date: Apr 2018
Glad to be of help, but we are really starting from scratch here. You will need to do more research on how speakers are wired and how enclosures are designed etc etc.

But here goes:

1. Imagine the two woofers and the crossover lying side by side. Connect the positive terminal of the first woofer to the positive terminal of the second woofer and then to the positive woofer terminal on the crossover. Similarly for the negative terminals. This makes a parallel connection. You will need twin speaker cable, not too thick or it will make soldering difficult.
4. This depends on what type of terminals you have on the amp and on the speaker. It is common to use twin cable fitted with 4mm banana plugs at each end. What amp do you have?
5. Lots more information about the particular speaker drivers would be needed to answer that question. Which woofers are you intending to use?

You don't need two separate crossovers or extra terminals. The midrange cable from the crossover can be passed through a small hole in the midrange compartment. The hole is then sealed with silicone to ensure it is airtight. There is no need for the tweeter to be in the midrange compartment as the tweeter is sealed and cannot be affected by the woofers.

No crossover recommendation can be made without knowing which loudspeaker drivers you choose.

Use a compression horn for the tweeter if desired but, again, we need to know which one you choose.
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Old 3rd July 2018, 12:09 AM   #12
Galu is offline Galu  Scotland
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Quote:
Originally Posted by hollowboy View Post
If you haven't yet bought anything, maybe consider getting a kit. All the decisions / measuring / crossover stuff has already been done, so there is much less to learn.

I couldn't agree more!
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Old 3rd July 2018, 12:09 AM   #13
WillHoog is offline WillHoog  United States
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Thanks but I am no where near affording that, the project is for fun, high volume listening, and learning. I plan on using these $20 woofers and $40 mids.

I don't want to cause too much trouble for other people finding answers for me but those last few things I asked hopefully are it, I seem to understand everything else.
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Old 3rd July 2018, 12:44 AM   #14
WillHoog is offline WillHoog  United States
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Thanks again for your help

I know with my little hands on wiring knowledge I should buy a kit but with a future of producing music I want to do this from scratch. I can definitely do some more research on how the enclosure is designed, I am mainly here because I couldn't find any wiring tutorials.

The sub:
Amazon.com: GRS 12PR-8 12" Poly Cone Rubber Surround Woofer: Electronics

The mid:
Amazon.com: Lanzar Upgraded 12” High-Power Performance Midbass - 400 Watt Speaker 45-4.8kHz Frequency Response 80 Oz Magnet Structure 4 Ohm 2” Temperature Kapton Voice Coil w/ 94.50dB Sensitivity - Lanzar PROHEMID12: Electronics

This tweeter horn seemed to be the best choice

Amazon.com: Goldwood Sound 90 Watts 8ohm Piezo Horn Speaker Tweeter Black (GT-1025): Electronics

Currently I am using an 8 channel mixer instead of an amp so the choice for an amp is still open, amazon doesn't seem to have much choices though.

I am confused what you meant by the tweeter not needing to be in the midrange area because where else would it go? I would assume the cable for the tweeter would also go through the slim hole i would cut into the divider.
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Old 3rd July 2018, 02:20 AM   #15
hollowboy is offline hollowboy  Australia
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Aha. For a low budget, those seem like decent choices.

Tips:

1) Cost everything before you begin, to check that it makes sense - that is, if you'll need $300 in tools and $200 in plywood to build your cabinets, it might seem silly to spend only $20 on drivers.

2) check ebay / local sales / shops / forums / people near you. You might be able to get speaker shells ("unloaded" cabinets) that are cheaper than you could build.

Pictured are some near me.

The plastic ($Aus 40) speaker shell has an integral horn. Buying something like this & simply mounting suitable components could save you many dollars & hours, relative to buying a horn & plywood and building from scratch.

3) put a small (1 ohm?) resistor in series with the piezo. A piezo can be a difficult load and can damage some little / cheap amplifiers.
Attached Images
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File Type: jpg 40 dollar shell.jpg (10.8 KB, 219 views)
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Old 3rd July 2018, 03:47 AM   #16
WillHoog is offline WillHoog  United States
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I am a bit confused about the resistor and piezo stuff, I plan on buying a pre-made crossover and I can spend up to like $100 on a decent sized amp that would look good with my studio setup

Buying pre-made cases seems like a good idea but my mom said I could get plywood really cheap at our local hardware store (that being pieces around 22" by 60")

My dad has a work bench, random power sander, soldering tools and screws (I would buy the right sized ones at hardware store. I'm not sure if he has the right jigsaw but that seems to run $31 on amazon.

About the ventilation for the subs, I couldn't find any simple math tutorials on it, only programs where I punch in around 50 numbers that I don't know how to get and some output that I can't do anything with. Logically thinking I would assume just to put the vent in between the 2 woofers (that would be on the other side of course) If this would give good enough an outcome I would be fine with that
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Old 3rd July 2018, 06:49 AM   #17
hollowboy is offline hollowboy  Australia
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Quote:
Originally Posted by WillHoog View Post
I am a bit confused about the resistor and piezo stuff
A piezo works differently to normal tweeters. A normal 8-omh tweeter is driven by a wire voice coil, and should have at least ~5 ohms of resistance at any frequency (google "tweeter impedance curve" to see).

A piezo is driven by a crystal. It has the opposite curve - the impedance falls to nearly zero at high frequencies.

You can use them with no crossover at all... but this can break some amps. Hence I suggested adding a small resistor as a (very) minimal crossover, so that the impedance never falls to zero.

Quote:
Originally Posted by WillHoog View Post
I plan on buying a pre-made crossover
I forgot this bit. Probably best not to use a pre-made crossover with a piezo. See link.

blowing up piezo tweeters

Quote:
Originally Posted by WillHoog View Post
and I can spend up to like $100 on a decent sized amp that would look good with my studio setup
Use a class D amp, and it will be so small, how it looks is irrelevant

You can get them for much less than $100, particularly if you get one without a power supply.

Something like this:
TPA3116D2 2x50W Class D Stereo Amplifier Board with Volume Control

...is $9 and can be powered for free, if you can scavenge an 18 volt brick from an old laptop or other appliance.

Quote:
Originally Posted by WillHoog View Post
Buying pre-made cases seems like a good idea but my mom said I could get plywood really cheap at our local hardware store (that being pieces around 22" by 60")
Do what makes you happy

That's just the shortcut I'd take (for a 1st time, budget project) - filling in the holes in an existing, cheap box will probably be faster and cheaper and better than making a box from scratch.

Quote:
Originally Posted by WillHoog View Post
About the ventilation for the subs, I couldn't find any simple math tutorials on it, only programs where I punch in around 50 numbers that I don't know how to get and some output that I can't do anything with. Logically thinking I would assume just to put the vent in between the 2 woofers (that would be on the other side of course) If this would give good enough an outcome I would be fine with that
$20 woofers are cheap partly because they have tiny magnets.

A result of this is that they don't suit 'ventilation' (porting). Yuo need something with have bigger magnets (more motor strength) to suit a ported enclosure.

I'd use the $20 woofers in big sealed (non ported) boxes, or in open-backed cabinets (like guitar speakers).
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Old 3rd July 2018, 11:19 AM   #18
Galu is offline Galu  Scotland
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I suggest you rethink your choice of speakers.

Look for the best quality you can afford and keep it simple as shown below.

Per cabinet:

One 12" woofer (8ohm)
One 6" midrange driver (8ohm)
One horn tweeter (8ohm)

Note. That's a horn tweeter - avoid piezo tweeters altogether!

Search for these using the exact descriptions above. It would be best if you can obtain all three drivers from the same manufacturer eg. MONACOR. That manufacturer would nodoubt have a crossover network which is suitable for the drivers.

Once you have settled on a single bass driver, I can help you with a simple method of working out the reflex port dimensions.
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Old 3rd July 2018, 11:54 AM   #19
andreasmaaan is offline andreasmaaan
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Hi WillHoog,

Great that you're about to embark on your first DIY speaker, but I'm afraid I have to rain on the parade and advise you to step back and research and learn quite a bit more first, unless you want to build a speaker that is unlistenably awful.

First of all, it would be good to know what your objectives are. If you're hoping to make something better than equivalently priced commercially available options, or to learn something about speaker design, and/or to build listenable speakers, you have a lot more learning to do before you get going IMHO!

The main problem I see is to do with the crossover. You can't just buy an off-the-shelf crossover and then fit it to any set of drivers and hope you will anything like an ok speaker. Indeed, the effect of the crossover will be determined by the complex interaction between it and whatever drivers you choose, and determining what thee interactions will be involves a lot of measurement, both of frequency response and impedance response.

If you don't do these measurements and then design the crossover accordingly, you're guaranteed to end up with a speaker that sounds significantly worse than even the worst available commercial designs.

I'd be really happy to give you some further specific advice but thought that this dire warning should come before any other discussion

Cheers,
Andreas

Last edited by andreasmaaan; 3rd July 2018 at 11:57 AM.
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Old 3rd July 2018, 01:40 PM   #20
Galu is offline Galu  Scotland
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As you've stated WillHoog, the project is for fun, high volume listening and learning - plus you want to do this from scratch.

The best way to learn is by doing. As as long as you don't break the bank or expect perfection then you're on the right track.

Sounds like you're a young fellow about to start off on the wonderful journey into Hi-Fi DIY - I was that young fellow once!

My first loudspeakers were built long before access to crossover design software and I obtained quite satisfactory results. Besides, there's always scope to tweak the crossover as part of the ongoing DIY fun!

You are more likely to fufill your stated objectives if you keep it simple, hence my suggestion to rethink your driver choice.

Last edited by Galu; 3rd July 2018 at 01:45 PM.
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