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Old 26th July 2011, 11:34 PM   #1
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Default Help understanding speaker design

Hi, basically im new to speaker building and its something ive wanted to attempt to do for a long time now.
Im looking to build a pair of floorstanding speakers much like these in a photo i found online,

Click the image to open in full size.

I was looking to use these for the mid/bass drivers

BM2500.5 Volt 10in 200W Mid-Bass Chassis

Im not sure what i would use for tweeters, any suggestions?

Also could somebody give a basic guide of how the inside of a speaker cabinet is designed and measured? Ive heard of a plan for the inside of speaker cabinets called transmission line, is that likely to be whats inside the cabinets i posted above?

I have a fully equip workshop as im a joiner so building the cabinets is not a problem.

Im completely new to this, would be great if someone could point me in the right direction. Everything ive written above is kind of guess work haha.

thanks,
Pete
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Old 27th July 2011, 12:14 AM   #2
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The boxes above are not Transmission Line but are Bass Reflex enclosures(as most speakers are). They have a longish tube (port) to extend bass response.

To help you design the boxes can I recommend WINISD (online version).

You just tap in the drive unit details (fs/vas/qts) and you can compare the bass response between drivers and optimum cabinet size. I think it gives the port length/size as well? I'm not 100% on this bit

Crossover design is the most important bit and something I am rubbish at. I can only say that even a simple 2nd order x/o for a 2 way speaker like this would be hard for a novice, even for me. The 10 inch volt will be tricky to match with a tweeter in a 2 way, if it is even possible..

can you go for something like a 6.5 instead?

PS Most Vifa tweeters are cheap and get good reviews.

Last edited by Bill poster; 27th July 2011 at 12:36 AM.
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Old 27th July 2011, 12:22 AM   #3
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Thread moved to multi-way.
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Old 27th July 2011, 02:13 AM   #4
gooki is offline gooki  New Zealand
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Quote:
Originally Posted by peter762033 View Post
Hi, basically im new to speaker building and its something ive wanted to attempt to do for a long time now.
Im looking to build a pair of floorstanding speakers much like these in a photo i found online,

Click the image to open in full size.

I was looking to use these for the mid/bass drivers

BM2500.5 Volt 10in 200W Mid-Bass Chassis

Im not sure what i would use for tweeters, any suggestions?
Looks good enough - PDF here:
http://www.studitech.ru/resque/manua...t_BM2500-5.pdf

Has a natural roll-off after 2khz. A BSC (baffle step compensation) circuit should be all you need to get it working well.

Loudspeaker Diffraction Loss and Baffle Step Compensation Circuits

A tweeter with a low FS (1400 htz or lower) and a sensitivity of 89db or more should match well with that woofer.
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Old 27th July 2011, 02:40 AM   #5
Loren42 is offline Loren42  United States
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Another path for the first time builder is a speaker kit or at least a pre-existing design. The kit is the best way to building a speaker that works instead of creating scrap wood and drivers. The latter would be a very good way to exit the hobby in disgust.

Regardless of your path, you need to sit down and determine what you want your speakers to be and what you are willing to spend to get there.

Maybe an even better thing to determine is what you expect to get out of the project (audio wise, knowledge, etc.) and how much you are able to spend to get there.

If you sit down and put that on paper, then post your answers here, there will be many people that can help you get where you want to be.

It is best to start with creating your vision of what you want before just diving in. Trust me.

Last edited by Loren42; 27th July 2011 at 02:42 AM.
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Old 27th July 2011, 03:13 AM   #6
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Loudspeaker design has two major elements, designing the box, and designing the crossover.
This site gives a good description of the design elements of each type of box,
Read the sealed & ported descriptions to start with:
The Subwoofer DIY Page

When it comes to crossovers, this site has all the basics:
Passive Crossover Network Design

and this page tells you how to do it the easy way
Introduction to designing crossovers without measurement
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 27th July 2011, 03:43 AM   #7
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Quote:
Originally Posted by Loren42 View Post
Another path for the first time builder is a speaker kit or at least a pre-existing design. The kit is the best way to building a speaker that works instead of creati
Worth repeating. A chance to experience all the things involved in building a speaker. Necessary background if you are going to start designing them.

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Old 27th July 2011, 04:02 AM   #8
tinitus is offline tinitus  Europe
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regarding your choise of woofer
looking at magnet size, and 95db for a 10", it looks more like a midrange oriented midwoofer

as said, it will as said take some years to learn how to deisgn a speaker
but nothing wrong in trying to have fun with some cheaper drivers

if your goal is to build a real good speaker, find a proven design
or maybe choose to go active
doesn't have to cost more than a passive design
sometimes it could even be cheaper

you may find cheap active PA crossovers
I expect it would do ok
or at least better than a randomly made passive
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Old 27th July 2011, 10:06 AM   #9
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Consider a closed box design. Most of the time just building a box that look well proportioned to the driver achieves a good q of 0.6 to 0.8 , or use a sim prog and manufactures specs. This way you will end up with a good sounding speaker as opposed to a bass reflex or transmission design which have more variables which need to be optimised.
Going active is also a good idea, plently of amps and active xovers on ebay, this way
you aviod passive xover design, just have to pick xover points/slopes.
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Old 27th July 2011, 01:10 PM   #10
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<$125USD for a MiniDSP. Painless crossover with EQ built in, live tuning, etc etc. A few hundred dollars for another amp and you're set. Note that with one 20watt amp running <300Hz and one running >300Hz you've got the voltage headroom of an 80 watt amp (in vague terms). Also the miniDSP will work just fine with systems capable of hundreds of watts and could cost less than a suitable passive cross.

MiniDSP will allow you to play willy nilly with different box alignments etc etc while you figure out what works and what else you need to know.

This is also not a 'until I learn how to do it properly' stop-gap. Active crossovers, multiple amps is going to dodge a lot of the problems and inefficiencies inherent in passive crossovers. Many say it's the best way.
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