Go Back   Home > Forums > Loudspeakers > Subwoofers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 7th July 2010, 01:02 AM   #1
SOSx is offline SOSx  United Kingdom
diyAudio Member
 
Join Date: Jun 2010
Location: UK
Default 18 Sound 8NMB420 tapped horn

Hi,

At the moment I am designing a small system for friend as a side project.
I wanted a bass cab that was relatively compact, efficient, a width of 290mm and Flat for the octave covering 50-100hz.

I decided after reading a few threads on hear covering smaller tapped success stories I thought i would through a few numbers into horn response and see what came of it.

Firstly the main (full range) cab consists of 1 x 8nmb420 + 1 x 8cx400. I have designed it to be a three way cabinet, actively driven from 3 channels of TK2050 amp boards (amp + active crossovers internally mounted).
This means that there is 1 spare amp channel of around 50w 8r/100w 4r to drive the separate bass Cab (small speakon link out from the main cab).

Well enough digressing!! Here is the tapped horn i have come up with.
I would be interest in feed back/criticism or even alternate driver cab combination's that fit the brief!!

Click the image to open in full size.
Click the image to open in full size.
  Reply With Quote
Old 7th July 2010, 01:05 AM   #2
SOSx is offline SOSx  United Kingdom
diyAudio Member
 
Join Date: Jun 2010
Location: UK
Oh yes I Should note that the design has a 2.2 mh inductor in the design hence the 2.55mh Le.
  Reply With Quote
Old 7th July 2010, 06:33 AM   #3
diyAudio Member
 
TundraLTD's Avatar
 
Join Date: Dec 2009
I'm still trying to catchup with my understanding of the TH but, as far as I understand currently... Raising the inductance [adding an inductor, coil, whatever you want to call it] you are simple adding a 1st order lowpass filter. Since Hornresp doesn't allow ext. components as far as I know. Does this actually have a place in a real-world built design or is it null/pointless when using a real active filter?
  Reply With Quote
Old 7th July 2010, 09:23 AM   #4
SOSx is offline SOSx  United Kingdom
diyAudio Member
 
Join Date: Jun 2010
Location: UK
Just read through what i posted last night.
Do excuse the bad grammar and miss pelt words.
It was late!!

I should also add that the screen shot showing excursion is taken at 50w, 8r in half space, as is the spl graph showing 115db output in band.

TundraLTD

I am relatively new to Tapped horn theory myself (had always ruled it out for sound quality purposes). Maybe wrongly so? We will see soon! Also for this design compact efficiency is the name of the game.

As for whether adding the inductor to flatten response could be duplicated with processing is also a question I have been wondering?
Maybe some of the TH veterans will be able to shed light on this?
  Reply With Quote
Old 7th July 2010, 04:48 PM   #5
hm is offline hm  Europe
diyAudio Member
 
hm's Avatar
 
Join Date: Feb 2004
Location: near Hamburg Germany
Default sosx

Hello,
i constructed a double bass horn with this driver,
useful 34-200 Hz and the possibility of a 6 dB crossover,

have a look:

i think your approach will work not better than a simple BR for this driver,
but test it, down to 50 Hz is to much work for the enclosure.
Your max. SPL is a bit optimistic if you see the membran movement.
Attached Images
File Type: jpg dbh8-20-s3-2010web.jpg (130.8 KB, 394 views)
__________________
http://www.hm-moreart.de

Last edited by hm; 7th July 2010 at 04:55 PM.
  Reply With Quote
Old 7th July 2010, 11:31 PM   #6
SOSx is offline SOSx  United Kingdom
diyAudio Member
 
Join Date: Jun 2010
Location: UK
Default Hi hm

Hi hm,

Thanks for the reply.
I should point out again that they will only have
a maximum of 50w into 8r realistically. The peak displacement
at this power, peaks at 6.3mm at 57hz. In the real world
the displacement should be less (due to not applying a constant voltagensine wave). I would think very close to 5.5mm xmax. This has been shown both here and in my own reaserch in pro audio designs.

As for a br achieving the same! You could achieve the same output in this volume, but not without using twice the no of drivers and 1.5-2 times the amount of power! Which is not available. Also to achieve the f3 of 43hz means tuning the box well bellow drivers fs, which provides an uneven impedance plot and over extended (peaky) response from 45-70hz.

Your design it is a dual tuned rear loaded horn right?
Shurely this design must be an impedance and phase nightmare?
With the three different radiating surfaces all with different acoustic lengths!
I have personally never liked the sound of rear loaded horns!

Last edited by SOSx; 7th July 2010 at 11:34 PM. Reason: Was a little abrahsive and not meant like that
  Reply With Quote
Old 8th July 2010, 05:06 AM   #7
hm is offline hm  Europe
diyAudio Member
 
hm's Avatar
 
Join Date: Feb 2004
Location: near Hamburg Germany
Default sosx

"Shurely this design must be an impedance and phase nightmare?"

may be you donīt understand my double horns,
take a look on my HP,
and compair it with you Imp and membranmovement.
between 89-92 i worked in a disco the amps never turn over 5 !! W
as i see your simu you will have 5 mm at 1 W between 60-80 Hz,
but if you believe, test it an show us the dynamic compression, good luck.
__________________
http://www.hm-moreart.de
  Reply With Quote
Old 8th July 2010, 05:18 AM   #8
diyAudio Member
 
Join Date: Jul 2008
Location: Pacific Northwest
Quote:
Originally Posted by TundraLTD View Post
I'm still trying to catchup with my understanding of the TH but, as far as I understand currently... Raising the inductance [adding an inductor, coil, whatever you want to call it] you are simple adding a 1st order lowpass filter. Since Hornresp doesn't allow ext. components as far as I know. Does this actually have a place in a real-world built design or is it null/pointless when using a real active filter?
Series inductors do work to flatten a response, I have measured a tapped horn with and without. The added series impedance "puts the brakes" on the resonant peaks in a tapped horn.

Click the image to open in full size.

Red = inductor, Blue = no inductor. The peaks are cut more than the rest, so it is not a simple low-pass filter in this application. Parametric EQ could do the same, no doubt.

No free lunch though - what are you giving up to get that flat response?

Efficiency. There is an increase in series resistance - that's the difference between the red and the blue lines. There may also be transient response issues, but that is beyond what I can measure with my current gear. If I can't measure it, I try not to talk about it.
  Reply With Quote
Old 8th July 2010, 08:38 PM   #9
SOSx is offline SOSx  United Kingdom
diyAudio Member
 
Join Date: Jun 2010
Location: UK
Hi hm,
I think I may know where your confusion lies!
As I have stated a couple of times. The peak excursion/membrane
movement hs screenshot is with 50w nominal input. Maybe the way I laid
the screen shots out had confused you?

The excursion at 1 watt is bellow 1mm!!

I must say I am not clear what you are trying to achieve with the double rear
horn designs? I couldn't find any predicted or measured
plots for these cabs, do you have any? I understand horn theory well
and can only see major issues occurring! Maybe I am missing something?
But in the pro world these wouldn't ever get considered as an option!

Tinymike- thanks for the measured plots it is nice to see the theory in operation!

Does any body else on here have any coments/opinions or ideas on improving the design?
Are there any mistakes In the design?

Kind regards
  Reply With Quote
Old 8th July 2010, 08:43 PM   #10
SOSx is offline SOSx  United Kingdom
diyAudio Member
 
Join Date: Jun 2010
Location: UK
Strange that last post had all the line/word spacing jumbled up after I pressed post?
Maybe due to how my iPhone browser displayed it?
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Ciare sw 18 for tapped horn soundhead Subwoofers 0 27th December 2009 01:52 PM
Dayton Classic 18" DCS-450 - Tapped Horn? dolinux Subwoofers 15 4th December 2009 04:38 AM
Tapped Horn for 18" bass angeloitacare Subwoofers 14 28th March 2009 07:37 AM


New To Site? Need Help?

All times are GMT. The time now is 11:41 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright Đ1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2