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-   -   closed/vented in same speaker? (http://www.diyaudio.com/forums/multi-way/69510-closed-vented-same-speaker.html)

yertzl 11th December 2005 07:36 AM

closed/vented in same speaker?
 
hey im about to set out on making my first set of speakers. ive read Speaker Building 201 and summerise its formulas in2 a spread sheet. though this has raised a number of Q's.
i intend on building a TMWW prob a bit ambitious of me for my 1st but ill give it a try.

i can find the box volume for say 1 or 2 speaker of the same kind. but what happens to the volume if i have 2 different speakers in the same box.(how would i add the Volume of T,M and the twoW do i just add the volume of each speaker which i find from the formulas)?

adding to the question above i way thinking of have the TM is a closed box separated via a board in the entire box. and the WW is a vented underneath. i figured this way i could get better trasience response for the top and better bass from the WW. though does this cause implications for the crossover since Close:accoustic drop off of 12dB/octave and vented 24db:octave. and or any other implications?

wintermute 11th December 2005 07:56 AM

If the M doesn't have a sealed back (and most don't) then you will need to put it in a separate volume than the W's. using a partition in the box is one way, or building a separate small enclosure on the back of the baffle is another, a third option is to make completely separate boxes for the Woofers and mid/tweeter.

The different rolloffs of the alignments doesn't matter, as it is only the upper rolloff of the woofers (due to the low pass in your crossover network) that you need to worry about matching with the low end rolloff of your mids :) (due to the natural driver/enclosure rollof + the high pass component of the crossover network).

Tony.

yertzl 11th December 2005 10:27 AM

If the M doesn't have a sealed back (and most don't) then you will need to put it in a separate volume than the W's. using a partition in the box is one way, or building a separate small enclosure on the back of the baffle is another, a third option is to make completely separate boxes for the Woofers and mid/tweeter.

The different rolloffs of the alignments doesn't matter, as it is only the upper rolloff of the woofers (due to the low pass in your crossover network) that you need to worry about matching with the low end rolloff of your mids (due to the natural driver/enclosure rollof + the high pass component of the crossover network).

thxs tony. that clears a lot of things up. just 1 thing though. i havent looked at a lot of speakers but for the M and when u say sealed back you mean that the driver itself is sealed right. and are most tweeters like that?
and thats got nothing 2 do with this mag shield thing right.
oh yeah sorry this raises another Q. so are vented boxes normally closed/vented with just the W been vented.
last 1: the book i read said id need a subsonic filter for sealed. but it didnt elaborate on that. what do i need to do 2 add this.

can you get a decent set of speakers without using testing equip. i read somewhere you get like 90% using equations and the last 10% is the hard part. you reckon that how it works...

much appreshiated. geez it all seems so scary. but i guess i just gotta build them.

wintermute 11th December 2005 12:00 PM

yes by sealed back I meant the driver itself is sealed and yes as far as I know all tweeters are like this and don't need to have their own separate volume.

subsonic filter needs to be put at the input of your amp, typically they roll off everything below 20Hz.... I would have thought though it was more important for vented than sealed, and then it depends on the tuning freq of the box.

In my experience you can build a pair of speakers (without measurements) that you are happy with until you hear something much better :) provided you don't go listen to any really high end gear you can probably build something you will be happy with without test gear. However you really do need to try and match the drivers well before you try this, I've used a large range of drivers in my three ways over the years (and two different stock crossovers), and some combos were completely awfull!!

I've been living with said pair of three ways for years with stock crossovers, and I still think that they sound better than most sub $1000 speakers I have heard (and much better than a lot of them), but I'm sure they could be a lot better...... however I'm designing and building some new speakers from scratch, this time with measurements and a crossover designed specifically for the speakers.

I think it is pretty common to have sealed mid enclosures, but vented ones do exist, whilst maybe not the norm, there is really no reason you couldn't have a sealed W enclosure and a vented mid, it all depends on the design goals and the drivers in use :)

I've done things the exact opposite way to what's normally recommended (ie I've never built a kit or a tried and tested design), but that's mainly because most of my speaker dabbling happened before I found this site :) I think there is a lot to be said for just building something, as long as you are prepared to make mistakes and try and learn from them, it can give you very valuable experience!!

Tony.

yertzl 11th December 2005 11:50 PM

thanks tony, yeah i meant vented for the subsonic filter.

i think i might try and learn this Speaker Workshop prog which i saw you talk about in another post. at least then i can be somewhat more confident.

http://www.claudionegro.com/ i got this page from you already 2 learn about it :)

much appreshiated

jens


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