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6th Order bandpass build

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Forum Name: New Projects Forum
Forum Description: Forum for new speakerplans projects, in memory of Tony Wilkes, 1953 - 2014
URL: https://forum.speakerplans.com/forum_posts.asp?TID=32873
Printed Date: 29 March 2024 at 1:09pm
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Topic: 6th Order bandpass build
Posted By: deepss
Subject: 6th Order bandpass build
Date Posted: 19 November 2009 at 10:11pm
Hi to you all,
 
   Thought it was bout time to post pics etc of a new cab me and a few have been playing with. The plan was to replace our 4 X  single loaded k-bin style subs with 2 X twin loaded subs.(Fane 18xb's). The idea was to try to create a cab that was more efficient and took up less space,(obviously). Been playing around with a few ideas and came up with these final 2 ideas.
 
After getting advice from forum members,went with this design:
 
  So,with heaps of tech help from some of you guys,decided to build a mdf (cost issue) prototype last sunday. I think it turned out well. Really nice sound and a vast improvement over our exsisting subs:
[/IMG]
 
 
There were a couple of issues with our central chamber port lengths,(have to ask Doober what software he used to spot them on his sim/laptop stuff),but sorted it out by just removing small sections of the port at a time untill we got it right....(Not the pic below cos thats got no port in)
 
 
Did the same with the wadding,took sections out etc,actually didnt seem to make that much difference in the enviroment we were in.
  We did angle the baffles and front sections to reduce/increase the cab size to fit with and under our HD215. Still got some tweeking to do to get it just right,or,have a go at building new horns to sit above these subs,but I doubt i'll do that.(need to give the missus some 'quality' time!!Embarrassed
 
  However,we did have a dip in dB's at about 38hZ. So far the suggestion is that its probably to do with the space we were in,not ideal. Any other ideas on this?? 
  For us now,the next stage is to brace the hell outta the cab,drag it outside and test it all again. Because it was just a prototype and we new we'd be taking it apart to adjust/trim/tweek/maybe throw in the bin,we never glued any joints and put in limited screws. And yesterday for our sins,we cranked it up and it blew itself open in certain areas! Kinda interesting where it did that,in places we least expected it!!
 
   The most important thing to me is that it sounded really good,much tighter and clearer than our old subs,AND a great use of this forum and its resources!!!Smile
 
   Cheers
 



Replies:
Posted By: fuzzylogic
Date Posted: 19 November 2009 at 10:27pm
Looks fantastic,top job!

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NEIGHBOURHOOD SOUNDSYSTEM
Infinitely baffled.



Posted By: cravings
Date Posted: 19 November 2009 at 10:51pm
really does!


Posted By: tomschute
Date Posted: 20 November 2009 at 12:06am
looks great - love to see some plots in 'good' environment.

Well done that man Wink


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Out to lunch... stableaudio@hotmail.co.uk
www.stableaudio.co.uk
Speaker Building Services


Posted By: pfly
Date Posted: 20 November 2009 at 2:28am
Why can't I spot access panels in rear chambers? Confused


Posted By: deepss
Date Posted: 20 November 2009 at 7:30am
Originally posted by pfly pfly wrote:

Why can't I spot access panels in rear chambers? Confused
 
This was just a prototype cab,so if the outdoor plots looks good and we build it,there will be access panels in the back. We made it so the top could come of easily,giving us quick access to change front and rear port sizes.
 
   Base box pro and winisd both predicted similar rear chamber port lengths,but front port lengths were different by bout 50mm,(winisd saying it was 50mm longer than BBP),Turns out,on the impedance plots taken on the day,BBP was nearer to what the sims said it should be. There could easily be mistakes somewhere with my sims,(which is highly possible). The front port was a bit fiddly,took a bit of arsing about to sort out air velocity,but think we got there in the end.
   We really need to brace it,put heaps more screws in it,drag it outside and convince Doober to bring all his testing kit to our workshop (again!)and do it all again. Then we can put up some accurate plots for inspection and refining from you guys!!!
 
Cheers
 
(There are stables where we have our workshop,so there is a huge open air sand school that all the nice horsey girls use.....which is nice to watch..eerrrm....I mean,which is a good place to test our cabsWink)


Posted By: mashgwan
Date Posted: 20 November 2009 at 8:44am
hello
we are currently looking for some dedecated sub bins to run under 8x es18bphs 
i was wondering what frequency range were you designing the cab for
 
thanks
 
nick


Posted By: deepss
Date Posted: 20 November 2009 at 9:13am
 Hi,
  Hopefully, they will run from 30hz to 65-70hz. But,no sure just yet how/or what range there gonna run in the real world. But they were simmed from 30hz 65 hz...
Cheers


Posted By: mashgwan
Date Posted: 20 November 2009 at 10:46am
cool, thats about the range we are looking for


Posted By: MusicXtra
Date Posted: 20 November 2009 at 11:12am
It looks....BIG!!!
What are the dimensions?
And is the air velocity not to high in the front ports?


Posted By: pfly
Date Posted: 20 November 2009 at 11:23am
As nice and neat it looks I am also wondering the size, mainly the height. Is it going to fit through doors? To me it looks like something well over 70cm high.


Posted By: deepss
Date Posted: 20 November 2009 at 12:54pm
Yeah,your right...it is big! Kinda concerned me too. The dimensions from memory are, H -710mm,W -1220mm,D -800mm(roughly)  Oddly enough,yesterday we were  looking into adjusting the chamber dimensions to bring the hieght down,which will prob result in it having more depth,but hey,you gotta start somewhere!
   Cheers


Posted By: deepss
Date Posted: 20 November 2009 at 12:57pm
and maybe move the side ports away from the side or the cab. The wadding is virtualy touching them. Dont know exactly how much difference it would make,just seems a sensible thing to do.


Posted By: doober
Date Posted: 21 November 2009 at 9:02pm
Having heard this cab I can say it does sound great. It sounds very smooth and goes hideously low, we managed to find those low notes on Avril Lavignes 'sk8r boi' (I had previously thought that was a wind up- apologies to whoever suggested that tune!). It moves some serious amounts of air.

I won't bother posting the plots we did as they were not in a suitable environment and could be well out. The interesting thing about the plots is the very steep notch at around 38hz, this is hopefully a function of the building we were in. We definitely need to try some more plots outside. The waterfall plot revealed some odd behaviour around this area.

The other measurements were impedance plots with LIMP to check the tuning frequencies were as planned. The lower ports were a couple of hz lower than predicted, no big issue really, could be due to the ends being close to the sides of the box. The front chamber was tuned way too low with the longer port, and ended up needing to be around a quarter of the predicted length- again the interaction with the top and bottom panels probably caused this.

I had originally thought the dip at 38hz could be due to the front chamber being tuned too low. It would seem logical to me that if the tunings are too close there will be a cancellation at a point halfway between them as surely the two sets of ports radiate sound of opposite phase? I could be quite wrong here.

Get it stuck back together and we'll have a go with it outside.

Kieran

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Blahblahblah


Posted By: axeman91
Date Posted: 23 November 2009 at 2:07pm
Looks mean!  How would it compare to an X1?


Posted By: deepss
Date Posted: 23 November 2009 at 6:40pm
Hmmmm...Lets not go there with that question! At the mo,its still work in progress. The thought of comparing it with anything is still a ways off. I am still new to this game so the chances of it all going to plan on this first attempt is a total long shot. But,more importantly,I'm learning heaps(slowly), and I'm totally enjoying myself.......and thats what its about for me just nowSmile
Cheers


Posted By: MarjanM
Date Posted: 24 November 2009 at 1:17am
Originally posted by axeman91 axeman91 wrote:

Looks mean!  How would it compare to an X1?



http://forum.speakerplans.com/x1-versus-b2_topic26788.html


-------------
Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713


Posted By: mstep77
Date Posted: 27 November 2009 at 6:13pm
Very nice mate, looks wicked


Posted By: james folkes
Date Posted: 27 November 2009 at 7:00pm
Originally posted by deepss deepss wrote:

a great use of this forum and its resources!!!Smile

amen to that, that's what this is all about...

james.


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mardy hippy.


Posted By: wafflesomd
Date Posted: 27 November 2009 at 11:02pm
Cabinet looks sick.  Wish I could hear em.


Posted By: deepss
Date Posted: 28 November 2009 at 12:16am
Just waiting for a break in the weather and then get it outside. See what it really does. We were going to have an attempt today,but the rain was blowing sideways.....again! So instead,spent the day in the workshop,blitzing it in the hope that this cabs got legs and I get to build a couple before Christmas.  (Even managed to get festool gear sent off for servicing and new blades).....What ever happens,I'm gonna have to build something.......probably an ark.,(with ports of course)Smile


Posted By: Gonzo-4-bidden
Date Posted: 05 December 2009 at 8:37pm

great work, have you considered changing the mouth of the cab to an open mouth type horn instead of (the dual letterbox type design?) excuse my retarded terminology but im on a learning tip myself, noticed this http://srforums.prosoundweb.com/index.php/t/51159/0/ - http://srforums.prosoundweb.com/index.php/t/51159/0/ on psw  which is very similar, just wondering if the different horn mouth design could cure your low frequency dips around 37hz? please correct me if im well off as any education in this would be greatly appreciated! great work!

 


Posted By: deepss
Date Posted: 06 December 2009 at 8:31pm
Yep,we looked at that but not yet that advanced to work that out just yet. Still waiting for a decent test though. In the meantime,I've decided to build a couple of X1's. I figured it would be good to have a couple. Have materials,kit,empty(and now tidy)workshop,and time.Need to build something so keeping in flavour with things sub,why not,be good experience!
   BTW,just spent past 15mins reading that link you sent. I'm not familiar with the prosoundweb forum. They get pretty heated over there!Tongue


Posted By: deepss
Date Posted: 09 December 2009 at 9:09pm
So..... At last,got the chance to get it outside and test again!
  The pic is really surreal,in fact it was really surreal doing that. Got some strange looks from the horsey folk..
 
 
Sorting out the plots now. Will post soon. (havin probs with photobucket Angry)


Posted By: deepss
Date Posted: 09 December 2009 at 10:00pm
  The problem we were having at 37Hz before,did turn out to be the building we were in. luckily!
 
  The winisd plots have an input power of 1000w.
 
cone excursion
 
 
Rear port velocity
 
Front port velocity
 
Impedance
 
 
 
And this is what was recorded outside today:
 
 
 
 
As of yet,I dont have a total grasp of all the above plots,its still a learning curve,but, Kieran (doober) was with me today to help out,so any questions I cant answer,I'm going to shamefully shove his way!!
 
   I dont have heaps of experience when it come to listening to various types of cabs/designs etc,but,I was really happy with how this sounded........which is nice!
 
Cheers
 


Posted By: MarjanM
Date Posted: 10 December 2009 at 9:27am
Is this a true 1m sensitivity?
With a calibrated microphone?

If it is, then it is not much better than a simple double 18 BR box. Not better at all.


-------------
Marjan Milosevic
MM-Acoustics
www.mm-acoustics.com
https://www.facebook.com/pages/MM-Acoustics/608901282527713


Posted By: doober
Date Posted: 10 December 2009 at 4:30pm
The measured frequency response plot is not calibrated and is not at 1m. The purpose of it was to check smoothness of response in an open space, as previous measurements indoors showed a huge dip around 37hz.

The plot may have looked even flatter if it had been done with a reasonable microphone. Unfortunately I didn't realise I had no phantom power for the measurement mic until we had dragged a huge speaker into the middle of a muddy field. We ended up using the output from my cheap spl meter to do the plot. This meter only has A or C weighting available. C weighting was used for that plot, which may explain why the line drops off at around 3db/octave as the frequency lowers.

We may well have another go at measuring it next time there is a dry day without too much wind, and I'll use a flatter mic next time. I can't do accurate 1w/1m measurements due to not having a decent spl meter to calibrate the software with, although I hope to be able to do some comparative plots with the same setup in the same location against some other cabs (punishers and various reflex boxes) to establish relative differences in efficiency.

The box certainly sounds good. Being a horn fan and not very experienced with bandpass I was amazed at the attack of this cab, It doesn't sound boomy or one note at all, very clean. And deep.

Kieran

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Blahblahblah


Posted By: Strange Daze
Date Posted: 10 December 2009 at 4:39pm

Very well done.

:)



Posted By: james folkes
Date Posted: 10 December 2009 at 10:58pm
fantastic plots, they really tie the project together. it's interesting that the impedance peaks, which were pretty evenly weighted in the model, are even more balanced in real life. the output plot is really, really smooth and demonstrates the cab's whopping great usable range, i too look forward to seeing one done with a flatter mic.

very interesting comments re attack kieran, very interesting. 8th order is supposed to be even better...

james.


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mardy hippy.


Posted By: Elliot Thompson
Date Posted: 14 December 2009 at 1:45am
That is a very nice response you have there. If you decide to add an equaliser, you can achieve a flat response from 40 – 100 Hz if you raise the 31.5 Hz slider by 3 dB.

Best Regards,


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Elliot Thompson


Posted By: deepss
Date Posted: 16 December 2009 at 10:28pm
Originally posted by Elliot Thompson Elliot Thompson wrote:

That is a very nice response you have there. If you decide to add an equaliser, you can achieve a flat response from 40 – 100 Hz if you raise the 31.5 Hz slider by 3 dB.

Best Regards,
 
OK,were starting to get somewhere with this.
This plot was taken today with a flat response mic.
 
 
We tested a few other cabs just to compare with.
K-bin hybred,
Punishers,
HD215, 
18" bass reflex
and a couple of 'off the shelf' cheepies,(berry 18" and peavey 15")  
The punishers were very impressive!  http://forum.speakerplans.com/punisher-plots_topic33742.html - http://forum.speakerplans.com/punisher-plots_topic33742.html


Posted By: 38HzQ2
Date Posted: 07 September 2011 at 12:33pm
did this project get taken any further? more cabs built?


Posted By: deepss
Date Posted: 14 September 2011 at 10:05pm
Yep! We just built the 1 (a second is still in flat pack) and its been out and about to back up our bass when we need it. Always a pleasure to listen to but its such a big cab. Really enjoyed going through the whole design process with lots of help from forum members. 
  Working on something new and different at the mo,have sworn Markie and Doober to secrecy but will post when its finishedSmile



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