# First speaker box construction



## aRavingPigeon (Jun 4, 2012)

Hello, I am new to the forum and am interested in building speakers. 
My first project will be an 18" sub for the boot of my car. I have located a bass speaker on ebay which I will be ordering it soon, however, I cannot find the speaker resonance frequency or the speaker displacement which I believe are key to designing the enclosure. 

I am also unsure as to what type of enclosure to build. Do vented enclosure have to be a specific size?
The dimensions of the enclosure I wish to build are:
Width - 35"
Back height - 15"
Front height - 7"
Depth - 19"
I will then fit the speaker in the slanted front of the enclose.

The speaker I have located is a QTX Sound 700w 18" Low Frequency Bass Driver
I know they are probably not the best quality, but I am on a relatively tight budget.
I will also be building enclosures to add onto this enclosure for 8" or 10" High/Mid range speakers.
I will be constructing the enclosures form either 12mm or 18mm MDF, whichever is more suitable?

The width of the sub enclosure may want to be less wide so to allow for room to fit the 8" or 10" speakers either side, I wish to fit these at an angle facing into the boot from either side.

Also, if the enclosure is vented, could the vent be covered in speaker grill to make for a cleaner look.
Matthew


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## BD55 (Oct 18, 2011)

All enclosures definitely need to be sized correctly to work. I am not nearly experienced enough to give you better info on sizing, and hopefully someone more knowledgeable can jump in here and give some better advice, though I do know there are many subwoofer building calculators online and subwoofer manufacturers put out sizing info often as well.

What do you mean by adding enclosures onto the sub box?

Thicker MDF is always better because it stops energy from your amp going to vibrating the enclosure walls. I've seen quite a few builds here with double layered ¾" MDF.

IMO you can always add a grill! I would definitely recommend one for the simple fact that your sub is going in your trunk and could be damaged by whatever goes back there.


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## fbov (Aug 28, 2008)

You're looking for "T/S parameters" for your speaker. They are not that hard to measure, if you have some equipment and an impedence bridge. There are also puprose-made testers like Parts Express' WT3. 

If you can get T/S parameters, you'll be able to use box simulators like Unibox and WinISD to predict the response from any size box and alignment. 

Have fun,
Frank


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## aRavingPigeon (Jun 4, 2012)

*Wiring up the speakers to an amp*

I have figured out the size of my enclosures etc.. and am now ready to buy the drivers and an amp.
The drivers I will be purchasing are:
1 x 18" 700w max, 350w rms at 8ohms
2 x 10" 200w max, 100w rms at 8ohms

And possibly a few 4" or 6"/6.5" full range drivers in door liners etc...

What size amp should I buy? Should I buy my amp so as the total rms wattage is over that of my amp, or the max wattage?

So will a 1000watt amp do as the current max wattage total is 1100 watts?

Cheers


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## robbo266317 (Sep 22, 2008)

Do you know the model number of the 18" QTX Sound driver? I found this one which is a 450 W RMS - model 902.559UK.

You need to model the driver before choosing a box to get the best out of it. Let me know the model number of the driver and I can check it for you.


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## aRavingPigeon (Jun 4, 2012)

I have decided to use 2 x 12" drivers instead. I will attempt to figure the rest out myself. Thank you for the advice.


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## aRavingPigeon (Jun 4, 2012)

This and the next post are just to allow me to have posted 5 times and so be able to paste links etc..


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## aRavingPigeon (Jun 4, 2012)

This and the previous post are just to allow me to have posted 5 times and so be able to paste links etc..


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## aRavingPigeon (Jun 4, 2012)

I have decided for the ease of things I will use 2 x Skytronic 902.222 12" 300W drivers as appossed to the 18" driver as I have the specs for these. 
The specs are as follows:

Power max:
300W
Power rms:	
150W
Voice Coil:	
6.25 cm (2.5")
Diameter:	
30cm (12.0")
Frequency response:	
20Hz - 6kHz
Magnet weight:	
1.4kg (50oz)
SPL @ 1W/1m:	
91dB
Re:	
7.1 Ohms
Fs:	
29 Hz
Qms:	
1.62
Qes:	
0.71
Qts:	
0.53
Sd:	
346 Cm2
Vas:	
49 litres
Cms:	
288
Mms:	
59g

I assume that when putting 2 drivers in one enclosure you add the relavant specs of the two drivers together, in this case the same drivers, when entering them into enclosure calculators etc?

Finally, could someone recommend the best enclosure size calculator to use as some I have seen are quite confusing.


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## fbov (Aug 28, 2008)

Yep; those are T/S parameters. Now download Unibox, if you have Excel, or WinISD.
http://audio.claub.net/software/kougaard/ubdwnld.html (Unibox)
http://www.linearteam.dk/default.aspx?pageid=winisd (WinISD)

I use Unibox, an Excel spreadsheet. You enter the driver data into the Dbase tab, then select your driver from the pull-down on the first tab. You will find a box below that where you choose number of drivers and wiring configuration. 

Below the entry area are analysis areas for sealed, ported, passive radiator and band pass alignments. Each is independent, and each has a charts tab. You can start with recommended values, or just enter Vbox and Fbox yourself. Then you can play!

HAve fun,
Frank


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## aRavingPigeon (Jun 4, 2012)

cheers Frank, i'll download unibox shortly.


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## aRavingPigeon (Jun 4, 2012)

fbov said:


> Yep; those are T/S parameters. Now download Unibox, if you have Excel, or WinISD.
> http://audio.claub.net/software/kougaard/ubdwnld.html (Unibox)
> http://www.linearteam.dk/default.aspx?pageid=winisd (WinISD)
> 
> ...


Cheers Frank, sadly I do not have excel but have downloaded WinISD and it is working well for my needs


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