Twin 18 P-Audio cab help

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   Here are some alternative simulations I knocked up (after having my own
long argument with WinISD Pro, it's got some horrible bugs, have gone
back to Beta).  

If you are willing to go for the added complexity and size of a 6th
order bandpass, there is some definite gain to be acheived. They'd
certainly give you plenty of low bass, maybe lacking definition though.

Personally I'd go for a reflex enclosure of about 200litres tuned to
around 40Hz.  While that seem a large enclosure, I use a lot of
similar single 18" bins (B&C 18PZB46 loaded) and with well placed
handles they're managable by one person.  Good general-purpose
subs for all music.

Since this is your first excursion into cabinet design, from experience
I'd recommend a simpler cab, reflex boxes are more forgiving on the
tuning and much easier to build.  Test boxes out of MDF could be a
good plan, see what works/what you like the sound of.

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ceharden Members Profile Send Private Message Find Members Posts Add to Buddy List The 10,000 Points Club Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11851	Post Options Post Reply Quote ceharden Report Post Thanks(0) Quote Reply Posted: 11 August 2005 at 8:20pm
	Here are some alternative simulations I knocked up (after having my own long argument with WinISD Pro, it's got some horrible bugs, have gone back to Beta). If you are willing to go for the added complexity and size of a 6th order bandpass, there is some definite gain to be acheived. They'd certainly give you plenty of low bass, maybe lacking definition though. Personally I'd go for a reflex enclosure of about 200litres tuned to around 40Hz. While that seem a large enclosure, I use a lot of similar single 18" bins (B&C 18PZB46 loaded) and with well placed handles they're managable by one person. Good general-purpose subs for all music. Since this is your first excursion into cabinet design, from experience I'd recommend a simpler cab, reflex boxes are more forgiving on the tuning and much easier to build. Test boxes out of MDF could be a good plan, see what works/what you like the sound of.

semtexsystems Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 10 August 2005 Status: Offline Points: 31	Post Options Post Reply Quote semtexsystems Report Post Thanks(0) Quote Reply Posted: 16 August 2005 at 8:31am
	Hi o.k. im nearly there! im think im gonna build a 6th order box working with the above volumes, and as you suggested i will build a test box out of mdf first. my next querry is the vents, looking at winisd i think i need the following ports using a port diamiter 64mm Front chamber = 4 x 72mm = vent match 0.05 Rear chamber = 4 x 28mm = vent match 0.02 i think this will be ok as the vent i read the vent match should be below 0.16 in order to avoid whistling. could someone please confirm that im working this out correctly thanks in advance Ben
	www.semtexsystems.co.uk

ceharden Members Profile Send Private Message Find Members Posts Add to Buddy List The 10,000 Points Club Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11851	Post Options Post Reply Quote ceharden Report Post Thanks(0) Quote Reply Posted: 16 August 2005 at 3:40pm
	I get the same when I use your port sizes. The box volumes I suggested are quite large, gonna be a pretty big cab but you'll find out whether it's managable when you build the test box. There might be some scope to make it smaller at the expense of a bit of low extension. What WinISD beta can't tell you is whether you'll have problems with driver excursion. The Pro version can, but the bugs seem to stop me inputting all the parameters.s Glad the image works, I can't test it myself as it's hosted on my own server in the house.

semtexsystems Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 10 August 2005 Status: Offline Points: 31	Post Options Post Reply Quote semtexsystems Report Post Thanks(0) Quote Reply Posted: 16 August 2005 at 5:29pm
	thanks alot for your help! as i say im gonna go for it and i'll post back in a week when i have got round to building it and let you know how it goes.. but before i do what do you mean by driver excursion?
	www.semtexsystems.co.uk

ceharden Members Profile Send Private Message Find Members Posts Add to Buddy List The 10,000 Points Club Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11851	Post Options Post Reply Quote ceharden Report Post Thanks(0) Quote Reply Posted: 16 August 2005 at 5:45pm
	Excursion: How far the coil moves in the magnet from its mean (no signal) position. The P-Audio you're using has an X-max of 6mm which means it can move that far in either direction before the coil moves too far out of the magnet. If you drive the loudspeaker such that the cone is moving more than xmax you will first start to get non-linearities in the sound wave it produces. If you drive it even harder you can damage the loudspeaker by trying to push it further than the suspension will allow and in some cases the coil may hit the inside of the magnet in one direction. Basically the cabinet should be designed such that in normal operation the excursion of the driver does not exceed Xmax. Make sense? Edited by ceharden

Centauri Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 29 November 2004 Location: Newcastle Aus Status: Offline Points: 1792	Post Options Post Reply Quote Centauri Report Post Thanks(0) Quote Reply Posted: 16 August 2005 at 8:13pm
	Had a play with WinISD Pro myself (new version DOES have a few issues). First problem is the specs on the link above are INCORRECT - see P.Audio's official site . The specs here work fine in Pro. The above tuning suggestion will run out of excursion at 51 Hz at 400W, and it looks like the port diameter of 64mm will be too small - 102mm should be ok. The ported box is also excursion limited at 60Hz to 417W. In both cases, increasing the lower tuning to 50Hz will increase the power capabilty to 600W excursion limited - you trade off low extension for a bit extra volume. Cheers Graeme

semtexsystems Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 10 August 2005 Status: Offline Points: 31	Post Options Post Reply Quote semtexsystems Report Post Thanks(0) Quote Reply Posted: 16 August 2005 at 9:00pm
	hello mmmmthanks. Just when i thought id got something sorted! O.K. To increase the lower tuning to 50Hz will i need to change the box volume? or do i do this by just changing the vents? thanks ben
	www.semtexsystems.co.uk

ceharden Members Profile Send Private Message Find Members Posts Add to Buddy List The 10,000 Points Club Joined: 05 June 2005 Location: Southampton Status: Offline Points: 11851	Post Options Post Reply Quote ceharden Report Post Thanks(0) Quote Reply Posted: 16 August 2005 at 9:33pm
	I'm not sure the european P-Audio specs are purely wrong, comparing with the official site shows a large difference between the two drivers, they even look different in some respects. We need to be doing the calculations with the drivers Ben actually has. So, Ben, where did you buy the drivers, and do they look more like the pics on the UK site, or the official (international) site. You'll need to alter both the volume and port size but lets check we're using the right driver params first.

Centauri Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 29 November 2004 Location: Newcastle Aus Status: Offline Points: 1792	Post Options Post Reply Quote Centauri Report Post Thanks(0) Quote Reply Posted: 16 August 2005 at 9:43pm
	The specs on the UK site just don't gell - the correlation between Fs, Sd and Mms for instance is incorrect. Makes all the other specs a little suspect. It could well be that they have upgraded the driver recently, but accurate figures would be nice. In my sim I just adjusted port tuning (both front and rear), which shifted the response curve upwards a little in exchange for decreased excursion. Cheers Graeme

LunchieTey Members Profile Send Private Message Find Members Posts Add to Buddy List Young Croc Joined: 06 February 2005 Location: Australia Status: Offline Points: 934	Post Options Post Reply Quote LunchieTey Report Post Thanks(0) Quote Reply Posted: 17 August 2005 at 2:35am
	Not sure how much this will help BUT... I use the p180/2241(different I know) in a 6th order cab of 120ltr/41hz rear and 70ltr 90hz front. The sims show it's not excursion limited until 36hz at 600wrms. 200ltr rear chamber seems mighty big for a single driver enclosure? My boxes are 200 total and seem quite big in person that's for sure. The plus side of these boxes is they sound great and are particularly adept at rattling some roof sheeting given more than 750wrms each(even 1.5k isn't a big drama-30hz highpass and slight eq dip on 20/25/30hz sliders(-3db)) Even with the 2242,low end extension won't change much at all if you knocked at least 50ltrs off the rear chamber.
	Speaker addict

semtexsystems Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 10 August 2005 Status: Offline Points: 31	Post Options Post Reply Quote semtexsystems Report Post Thanks(0) Quote Reply Posted: 17 August 2005 at 4:23am
	I had no idear that building a box would be such a pain! The subs where purchased from ebay so not to sure if there uk spec or not. There is some paramiters on the box they come in however i dont have them here, there at a friends house, i will ask him to post the deitails from the box when he finnishes work at 3pm (uk) thanks ben
	www.semtexsystems.co.uk

semtexsystems Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 10 August 2005 Status: Offline Points: 31	Post Options Post Reply Quote semtexsystems Report Post Thanks(0) Quote Reply Posted: 17 August 2005 at 11:16am
	HI there Here are the specs for the drivers we have. Many thanks Peter Edited by semtexsystems
	www.semtexsystems.co.uk