audax home theatre front

[gpc]

Hi all, great forum

I am a bit of a newbie to building speakers this is to be my first project (done hopefully correctly)

I was thinking of changing the audax home theatre main speakers to a floorstander and need a bit of advice.

would i need to alter the original crossover design?

I have played with WinISD a bit could someone take a look at the transfer function

the port comes out at 8.2cm dia 7.99 length, the resonance is 2150.2Hz. What effect will this have on the sound? should i try to get a different resonance?

Ian

[kelticwizard]

Changing the bass/mid to a different box will not affect the crossover to the tweeter. Any change in box size, type, etc will be under 1,000 Hz, in fact under 500 Hz, so the tweeter crossover range is not involved at all.

It seems to me that a cubic foot and a half is a lot of volume ot get down to a 47 Hz cutoff, but if you are willing to use a box that size for convenience sake, go ahead.

The port resonance of 2150 will not be affected. Your port will have maximum output at 48 Hz, be 12 dB down 96 Hz, 24 dB down at 192 Hz, etc. By the time you hit the pipe resonance of 2150, you'll probably be well over 100 dB down from the midpoint!

So relax.

[kelticwizard]

Something is wrong.

Looking at your Thiele-Small specs in your graphic, I see the Qts is 0.397, and the Fs is 48.5.

Such a speaker would do well in a ported box approximately equal to it's Vas, and tuned to it's Fs, or close.

Instead, your box is twice the volume of your Vas. You should show a "boom" in the response. Yet, the response is flat.

Something is wrong. For flat respnse, your enclosure should be about 24 liters and the tuning should be about 48 Hz.

Let me check to see if your port would tune a 48 liter box to 48 Hz.

[pinkmouse]

Just a quick point, but if you haven't already got the drivers for these, check you can, as Audax have given up on diy sales in favour of mass market OEM sales. I would hate you to do all this work and not be able to build anything at the end of it...

[kelticwizard]

I use an older, simpler version of WinISD which does not deal with Transfer Function. So I will forego discussing that.

If you want to know about Transfer Function for a ported box, I will refer you to Thiele and Small's papers on the subject-there is a site where a diyAudio member, richie00boy, generously lets you download them for free.
http://www.richie00boy.pwp.blueyonde...pers/index.htm

However, going by the Thiele-Small numbers as listed:
Volume of box: 25 liters
Tuning: 48 Hz
Vent: 8.2 cm diameter, 21 cm length.

You have Thiele's "Classic" Bass Reflex, and it should serve you well.

[gpc]

thanks guys

Pinkmouse-Ipl acoustics in uk still have the drivers listed, i'll give them a ring on monday to check

kelticwizard- it seems if i just alter the box size in winisd the response stays quite flat upto about 60l

with this being an mtm does this mean that you can double the vas because of 2 drivers?

still intent on making some nice slim floorstanders would i be better off splitting the box into 2 halves to get down to 25l. the bottom half basically a stand

[kelticwizard]

Originally posted by gpc

Pinkmouse-Ipl acoustics in uk still have the drivers listed, i'll give them a ring on monday to check

By the way, what is the model number you are using? I'd like to model it myself.

Originally posted by gpc
kelticwizard- it seems if i just alter the box size in winisd the response stays quite flat upto about 60l

Going from 48 to 60 liters is a 25% difference. It should "boom" maybe only a decibel or two.

Did you model this using two drivers? That would explain the difference.

Originally posted by gpc
with this being an mtm does this mean that you can double the vas because of 2 drivers?

If WinISD or any program has a provision for number of drivers, you don't have to do that. If you use a different program and it has no provision for different numbers of drivers, then you must double Vas.

Originally posted by gpc
still intent on making some nice slim floorstanders would i be better off splitting the box into 2 halves to get down to 25l. the bottom half basically a stand

If the thing is an MTM, you will use the full 48 liters, so you won't have to do that. Slim floorstanders are nice, aren't they?

by the way, using two woofers will mean the vent should be originally as modelled, 8.2 cm diameter, 8 cm long.

[gpc]

the model no. is AP170ZO ipl sells these for £25 which seems reasonable

http://www.partsexpress.com/pe/pshow...number=296-165

yes model with two drivers the winisd im using lets you select upto 10 drivers

oh and the tweeter

http://www.partsexpress.com/pe/pshow...number=276-152

basically i wanted to start off with a kit that was already well designed for my first build, but then thought I wonder if these would work well in a tower lol.
I could then make the towers the right height etc.. for my sitting room

the kit is this one

http://www.madisound.com/audaxhometheater.html

[gpc]

had another play with winisd and 54l seems to look good aswell

Thanks again for your help
Ian