Horn sub with HT sub driver (AV12) - diyAudio
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 30th November 2004, 06:50 AM   #1
diyAudio Member
 
paulspencer's Avatar
 
Join Date: Sep 2003
Location: Melbourne, Australia
Lightbulb Horn sub with HT sub driver (AV12)

How feasible is it to design a horn sub with a HT driver? In particular with my dual AV12 high excursion 12" sub drivers. I can live with an F3 around 30 Hz as with room gain and a little eq I can still get down low for HT. I had a play with hornresponse some time ago with my drivers and it seemed that the excursion would likely not be exceeded, which means I could easily use some eq boost down low where the ear isn't so sensitive to distortion.

In a 30 Hz horn how does the output at 20 Hz compare with a sealed sub?

I'm thinking of placing the horn behind the couch, as it's the least obtrusive option and interacts with room modes the least.

Width 1.1m
Height 0.8m
Depth 0.4 - 0.6m

Parameters are:
SD 498 cm2
CMS 0.25 mm/N
Mms 228 g (don't know what MMD is)
Re 2.97 ohm
BL 15 Tm
Rms 6.848 kg/s
LeVC 2.95 mH

Thanks for your help guys
  Reply With Quote
Old 30th November 2004, 07:25 AM   #2
diyAudio Member
 
paulspencer's Avatar
 
Join Date: Sep 2003
Location: Melbourne, Australia
Bandwidth is 20 - 80 Hz max, might cross as low as 60 Hz.

While I have managed to model my drivers in Hornresp before, I haven't been able to make sense of the dimensions it works out.

What are some of the critical design parameters in a horn sub?

It's not so much that I have bought these drivers to do a horn sub, but rather I have them and have wondered what a horn sub would be like for them. I haven't had the pleasure of hearing a horn sub yet. (Anyone in Melbourne have some horns?)
  Reply With Quote
Old 30th November 2004, 07:27 AM   #3
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
HI,
I'm still new on this horn theory, so please excuse any misconceptions.
Your question should be; how will the response and spl vary in the octave above Fc - a small mouth and short horn will not perform at all evenly.
Below Fc the speaker reverts to box loading without the horn to give reactance. This appears to happen over a very short octave range.
Once the horn is not functioning you will find that driver Xmax will be exceeded for very small acoustic outputs, try putting numbers into hornresponse, iterate various voltages & extract maximum spl over a range of frequencies below FC using xmax at chosen frequency as your limit for each voltage. You will not be impressed.
By the way how did you manage to achieve an Fc of 30Hz in such a small box?
regards Andrew T.
  Reply With Quote
Old 30th November 2004, 07:47 AM   #4
diyAudio Member
 
paulspencer's Avatar
 
Join Date: Sep 2003
Location: Melbourne, Australia
Quote:
By the way how did you manage to achieve an Fc of 30Hz in such a small box?
I didn't

The Lab sub has 2x12" drivers, it's a 27 Hz horn and only slightly larger than I have in mind.

Quote:
Once the horn is not functioning you will find that driver Xmax will be exceeded for very small acoustic outputs, try putting numbers into hornresponse, iterate various voltages & extract maximum spl over a range of frequencies below FC using xmax at chosen frequency as your limit for each voltage. You will not be impressed.
I currently have them in 70L sealed boxes and their output is quite impressive already. The excursion is 46mm P-P and I have a combined VD of 4.6L, barely less than the Tumult.
  Reply With Quote
Old 30th November 2004, 03:06 PM   #5
BAM is offline BAM
diyAudio Member
 
Join Date: Sep 2001
Location: Carmel, IN; West Lafayette, IN
Send a message via AIM to BAM
Lab Subwoofers only work their best when you have four of them. A horn sub that you're talking about would need to be built into the floor. Just stick with direct-radiating subs for home use, I say. The AV12's Fs is too low, also.
  Reply With Quote
Old 1st December 2004, 06:40 AM   #6
diyAudio Member
 
paulspencer's Avatar
 
Join Date: Sep 2003
Location: Melbourne, Australia
I'm certainly not going to get another driver for this. This is just a thought experiment that I might build ...

My driver isn't that different to the Eminence Lab12 driver, which is designed specifically for the Lab sub. Qts, fs, BL are quite similar. The VAS of the Lab is a bit higher (not sure if that's significant).

I modelled my drivers in the Lab sub and the result didn't look good.

I modelled both of mine in a box that measures 1.1 x 0.8 x 0.6m and what was strange was that two model better in a box that size than one. The mouth area was 0.8 x 0.6m. With this size I managed to get a Fc at around 40 Hz or a bit lower using as much power as I can get without coming close to the drivers excursion limits. However, the rolloff is so sharp that even with another 8db of headroom below Fc, it doesn't do much to get any more depth.

How do you judge a horn in terms of simulated performance prior to building it? How do you know whether it is a good design or not?

If Adire can get a 30 Hz horn for the Tempest, then surely I can make one for my drivers to at least get to 35 Hz without it being too much bigger!
  Reply With Quote
Old 1st December 2004, 10:29 AM   #7
BAM is offline BAM
diyAudio Member
 
Join Date: Sep 2001
Location: Carmel, IN; West Lafayette, IN
Send a message via AIM to BAM
I, personally, am going to advise against this, because if you want a horn that won't fill up the room, you're going to lose a lot of the AV12's low end, and then you'll also have trouble getting flat response. I enjoy the low bass that my AV12 puts out. You should go ahead and build those sealed subs you were looking at in the beginning. If you horn load the AV12, its low FS means that below the horn's flare cutoff, the driver will still be trying to put out sound with no help from the horn, and the kind of EQ it would take to equalize that lowered level back up to the rest of the horn loaded output would be huge, and the driver probably couldn't take it. Horns can be fun, but they have their limitations and tradeoffs just like any other speaker enclosure. These are the things I've learned through the course of the design of my very own PA bass horn design, and I've learned them from reading material from very knowledgeable people (in particular, a well-known individual named John Sheerin who evidently lived down the street from me back in my hometown a few years ago) and soliciting their opinions on my design.
  Reply With Quote
Old 1st December 2004, 01:54 PM   #8
diyAudio Member
 
paulspencer's Avatar
 
Join Date: Sep 2003
Location: Melbourne, Australia
You may well advise against it, but this is a "thought experiment" right now. I'm going to toy with the idea whether or not you think it's a good idea ... I still intend to build small sealed subs as I can most probably only live with them in the room.

Looking at it another way, I'm not losing low bass but gaining higher output / or lower distortion in the midbass, where distortion perception is more significant. I just modelled using hornresp with a larger rear chamber. The rolloff was not so dramatic and it was possible to get 110 db within xmax limits at 20 Hz. Above this the response rises up to 130 db and above with more power if 20 Hz signal isn't present. I could then use eq to get the response flat to suit preferences. Seen this way I don't lose extension so much as gain low distortion midbass. Down lower I have to rely on excursion, hence higher distortion, but it's then not so critical as this would be LFE.
  Reply With Quote
Old 1st December 2004, 04:09 PM   #9
BAM is offline BAM
diyAudio Member
 
Join Date: Sep 2001
Location: Carmel, IN; West Lafayette, IN
Send a message via AIM to BAM
What I'm saying is you'd probably overdrive the woofer if you EQ'd up the lower ranges to match what the horn is doing to the upper ranges.
  Reply With Quote
Old 2nd December 2004, 05:25 AM   #10
mike.e is offline mike.e  New Zealand
diyAudio Member
 
mike.e's Avatar
 
Join Date: Sep 2004
Location: NZ
Send a message via ICQ to mike.e Send a message via MSN to mike.e
I most definately would NOT use a driver below its horn cutoff frequency on horn. Typical measurements into the double digit THD percent.

IF your getting 104db/1watt at the frequency you desire,with sensible design,yes it will be good!

if you still want low end,youl need another sub for bottom octave-and it will never be able to match the horn output.
  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
Single Driver Horn Base Port from Frugal Horn EmergencyDpt Swap Meet 0 26th October 2008 01:24 AM
which single driver/horn? garymck Full Range 1 25th May 2006 02:39 PM
Driver for BK-16 horn VadimB Full Range 8 12th January 2006 05:23 PM
FS: AV12 MKII 12" sub driver Rklepl Swap Meet 7 2nd October 2004 12:10 AM


New To Site? Need Help?

All times are GMT. The time now is 07:44 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2