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Rob255

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Joined 2009
#1
Hi there.

Im planning on building myself some speakers, If I run my plans past you, you can tell me if im heading in the right direction as in doing my research for this project I found speakers aren't as simple as I first thought!

So what I propose is MDF Boxes, (I Reckon 18mm?) Running 15" drivers for bass, 10" For mids. Does that sound ok?

Im unsure what my options are, as far as tweeters o. What are the pros/cons of bullets or piezo horns?

Can I use a shop bought 3 way crossover to seperate the signal between the speakers?

Should I port the boxes for better bass?

Is there anything I can do to help get the best from the drivers I buy, e.g soundproofing or something?

Cheers, Rob.
 
#2
Hi Rob

I like big woofers so I have no problem with you using 15 inch for bass duties.
What you are asking though is a set of inter-related questions the answers to which are dependent on the driver selection.
Personally I like sealed boxes with relatively high "Q" drivers for sub-woofer duty.
Ported boxes need a bigger box to perform well and usually use a driver with a lower "Q" and there are drivers which can be used in either type of box
10 inch mid-bass and mid-range is do-able although the usual approach would perhaps see a compression driver taking over very low.
The classical approach would probably see a 6 inch mid-range crossed over quite low and using a tweeter from about ( and these are fuzzy figures) 2500Hz

NO to the shop bought XO and I don't like piezoelectric tweeters (others do)
There is always things you can do to improve the performance of the combination of box,driver and crossover, starting with adequate bracing acoustic damping and using good components in the XO and good driver selection.
I would suggest that before you delve any further into the question you do some research, read some books and read thruogh a few of the threads on here.
Go to a local HiFi store and see/hear what you can get for your money and set a budget.
Most people here are willing to help, but not every-one has the same opinion and we need you to provide as much relevant information as you can.
Even the question regarding MDF as a box material can open a can of worms, do a search for the threads on what makes the best box, it runs for hundreds of posts and dozens of opinions.
I have used different materials for boxes most based on cost, MDF is OK so is a combination of MDF and other materials.
Read the threads and be prepared for a lot of trial and error

Simple NO!!
Fascinating & addictive YES!!!

Regards
Ted
 
#4
You are facing a number of difficulties, adapting pro drivers fore domestic use

Active crossover is really not my cup of tea, but it might be your best shot to make it work

Use 18" woofer
B&C 18PS100 in 150liter BR would work
Double Eminence Alpha-6A might work with a "slot" tweeter
Or maybe better consider a "ribbon" like Hivi PLANAR RT2-pro
 
#7
Cheers for the help,

I'm looking forward to this as i have access to a carpentry workshop over the weekends.

the music the speakers will mostly be playing is drum and bass, Hence the need for Huge bass sounds without distortion

Tempted by some 24" drivers haha! If i was made of money....
 
#8
Reading Undefinitions FAQ'S I realise the cabinets & crossovers are better being designed around the drivers.

being a (Trainee) electronics engineer, I have no problem designing and making cicuits, have built high / low pass filters, and Im sure I could tackle a 3 way cross-over after the appropriate research.

My question is, how do I calculate the corner frequency i need in relation to the drivers I buy? how do i know if the Q value is enough to justify ported boxes?
 
#9
Rob255 said:

Im sure I could tackle a 3 way cross-over after the appropriate research.

how do i know if the Q value is enough to justify ported boxes?
Click to expand...

I dont mean to be rude, but you seem have reversed the demands
Crossover is the hard part and will never get easy
To evaluate the driver is the easy part

Sim a lot of drivers and you will soon find what specs you need...or simply invent a driver and change its specs, and see what happens
And you may quickly realise that the driver you want, doesnt exist
 
#10
Rob255 said:

being a (Trainee) electronics engineer, I have no problem designing and making cicuits, have built high / low pass filters, and Im sure I could tackle a 3 way cross-over after the appropriate research.

My question is, how do I calculate the corner frequency i need in relation to the drivers I buy? how do i know if the Q value is enough to justify ported boxes?
Click to expand...
Well, the fact that you understand filters will certainly help. I'm no EE so I had to learn the stuff in a more roundabout way. However, speaker crossovers are really ... um, nebulous? Being able to calculate component values based on XO frequency and filter Q is only step 1 (out of like 20). I mean, I usually do start with "textbook values," but the resulting filter is anything but usable. So then I start adjusting values until the Frequency Response flattens, then I look to see how the acoustic phase is lining up, and adjust components to keep the flat FR but line up the phase better. Then I have to adjust components to keep the impedance in a safe range (while still keeping the FR and acoustic phase in-check) THEN, I finally hook up some components and start listening... 99% of the time, the XO still needs more tweaking to sound "good."

Now, I respect that fact that you're a drum & bass fan (from England, no less. The land of the best electronic music on the planet!). (BTW: you'll notice that I've written quite a bit of my own drum & bass if you look around my site) You would probably have a blast desinging your own sub as a first project. It's an excellent way to get the hang of tuning an enclosure.

Yes, you can tell from a driver's Qts whether it will work better sealed or vented. And using some free box modeling software, you can find out how large of a box you'll need to get your desired F3 (or if the woofers you've chosen can even reach the level of bass extension you think you can). You'd be surprised to find out that you can pretty much get down to subterranean depths (we're talking 20 Hz here) using only a 10" woofer--in the properly tuned box. In fact, some 8" woofers can also get you down into the mid 20's without much trouble. So basically, the advantage of a really big woofer at that point is simply that it has more surface area and can "move more air" and thus deliver more SPL; but it won't necessarily go any deeper. Also, the bigger the woofer, the larger the required enclosure needs to be.
Here are the two most commonly used box modeling programs. Plug in the T/S values for your desired woofers and play around and see what kind of bass extension you can get:
unibox (my personal favorite): http://audio.claub.net/software/kougaard/ubmodel.html
WinISD: http://www.linearteam.dk/default.aspx?pageid=winisdpro
 
#11
Hi Rob, all
First of all you should chose your main driver. (Do you have the time to go slow/better, or do you have a time frame?). Next and at the same time tell us how is the market for you, for brandnames, can you afford buying all them (I don't mean expensives ones but available ones, wich shop is that you buy from - like from abroad or is there any problem with postage for you,?). This is very important because is going to make you decide for the best main driver for you (price, et all). Last, I want to tell you that a good xover (3way) for one enclosure can cost you more than one 100 (£$€), so be prepared. Good that you have a carpenters shop :checked: that is very, very good. Give us some feedback and then we go from there.
Cheers.
 
#12
Im going to need to buy a book or something because Its not the sort of thing you can understand after asking a few questions on forums!

And on behalf of britain, I'd like to thank you for your compliment of our music scene.

I might look into importing my drivers after seeing these in parts express

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-336

They seem incredible value for money, I haven't found anything like that in the UK. Will they be rubbishfor that money?

Im not under any time constraints, Just my own impatience!

I'll sort out some drivers, and simulations, And I'll be back!

Cheers again for all your help.
 
#13
Rob, 4 Ohms means a short lead attached.
Now, for a serious driver (not that (yours) is bad but I can't find anything on it (no specs/no factory-measurements->losing time/no miracles), and so for a moving/road speaker (light) or standard Hifi (home use) I have two serious proposals that deserve some attention, after you mention a 15", that is a very good choice.

15"SELENIUM WPU1509-SLF - 8,25Kg (home-use quality) or,

15"SELENIUM 15W12P-ND-SLF - 2,4Kg (good for the road).

*slf means no logo.

Now this is why?!, because they are going to give you the mid-bass frequencies to 2kHz and up (1.5/1.6kHz or other xover frequency) what another driver doesn't do and you don't need a MID driver. That's why you need to look at a frequency/output chart. Their polar response is also good (both, better with the first).
Look at it like this (you can build a 3-way or a 2-way) you are going to spend serious money on the carpenters shop (plus xovers), so better having a running mate speaker and not spending money on trash. (?!) You know what I mean. ...And if you want to build a 3-way you don't start with the woofer like you are doing but w/ the main driver or mid-bass, that's why I said that, because I know where you'r going.
Cheers.
 
#14
 
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