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View Full Version : BEATING A DEAD HORSE (sub questions?)



Nordwall
07-07-2006, 12:51 PM
I will first aplogize for resurrecting this horse, and then beating it down again.

1. Want to build a sub enclosure
2. I have (6) 2235's of which 4 have new surrounds

I realize that one 15'' driver should be in a enclosure roughly 5 cuft.
If I am going to use 2, what would be the enclosure size?
Is there any great advantage of using 4, or is there a point of diminishing returns?
Does the shape of the enclosre matter. Whether it is a rectangle or box or wedge or...
Sealed or Ported?
:blink:
Okay no more questions. Thanks for the advice and a great forum.

CJ Newbie

speakerdave
07-07-2006, 01:02 PM
Try this:

http://www.jblpro.com/pub/manuals/enclgde.pdf


I will first aplogize for resurrecting this horse, and then beating it down again.

1. Want to build a sub enclosure
2. I have (6) 2235's of which 4 have new surrounds

I realize that one 15'' driver should be in a enclosure roughly 5 cuft.
If I am going to use 2, what would be the enclosure size?
Is there any great advantage of using 4, or is there a point of diminishing returns?
Does the shape of the enclosre matter. Whether it is a rectangle or box or wedge or...
Sealed or Ported?
:blink:
Okay no more questions. Thanks for the advice and a great forum.

CJ Newbie

Steve Gonzales
07-07-2006, 01:21 PM
http://www.lansingheritage.org/html/jbl/reference/technical/1983-subs.htm

Sometimes it is better to have a pair of single subwoofers in your listening room. It enables you to place them at different positions in a room that has a problem with weird resonance peaks and nulls. As far as using all of those woofers in one room, that is your own choice. I would at least try to build a pair of B380 clones to start with. You might find the matching JBL BX63 electronic crossover on ebay or some other equivalent. I have personal experience with this setup and it is nothing short of awesome when it is properly set-up and integrated into a system. BTW, The 2235H is highly sought-after, if you were to find that just 2 B380 clones would be enough to satify your personal taste, you could sell the rest of them to fully finance the whole project. Welcome to the Forum and best of luck with your project, Steve G.

Mr. Widget
07-07-2006, 04:10 PM
Is there any great advantage of using 4, or is there a point of diminishing returns?I'd go along with the JBL recommendation and guidelines that Dave posted... in fact I have. I have built them and they work quite well... better than any of the systems that JBL used the 2235 in... IMO.

As for using multiples... how large is your room, how loud do you want to go, and will this be for music or movies?


Widget

Steve Gonzales
07-07-2006, 05:06 PM
I'd go along with the JBL recommendation and guidelines that Dave posted... in fact I have. I have built them and they work quite well... better than any of the systems that JBL used the 2235 in... IMO.

As for using multiples... how large is your room, how loud do you want to go, and will this be for music or movies?


Widget That chart says that the tuning of that enclosure is 30hz. Will it deliver substantial output below that?. Just curious.

Nordwall
07-07-2006, 05:45 PM
Room size is 20' x 14' and just about 9' ceilings.

The purpose of the system is for music, but it is a quasi surround sound system as well.
How Low?
I would love to be able to get down to 16hz, but I realize that these drivers were not designed for that.
How Loud?
I listen to all kinds of music, however organ music is where I am trying base this system around. Basically having the right components to recreate that bottom octave effectivley. I am not into petite "hide me" speakers. That's why I found you guys!

MJC
07-07-2006, 06:00 PM
Room size is 20' x 14' and just about 9' ceilings.
My room is 17.5'x20'x9' (mid level height vaulted ceiling) and I use 4 subs. Two sub1500s and two 12" subs connected to the main L/R to run the mains full range. All four are sealed units.
I've felt that room shake, and hear nothing THAT low. So it must be sub-sonic.

Mr. Widget
07-07-2006, 06:18 PM
That chart says that the tuning of that enclosure is 30hz. Will it deliver substantial output below that?. Just curious.You should never drive a bass reflex system too hard below it's tuning frequency. The system unloads and the distortion increases markedly. If you really push it you will break the woofer.


Widget

boputnam
07-07-2006, 06:23 PM
The purpose of the system is for music, but it is a quasi surround sound system as well. As I had posted - and then deleted - approach multi source VLF with some hesitation. VLF from multi-sources can overwhelm and be fraught with cancellations / resonances. In my live applications, I am continually surprised at the ability to reduce either the number of subs and/or their gain, and achieve a cleaner, more intelligible response with greater tonality. I focus a lot on the bass - when it muds, the show can suck. In some clubs, I send a L+R sum to one sub and leave the other idle. Works incredibly well (better than reducing the LF gain).

For music, I'd start with two subs, at most, and measure the room response. Get the VLF in-balance with the other bandpasses, and apply proper EQ. If the sound is not pleasing, then consider more. In this business it's always a "less can be more" approach, especially when seeking good tonality. Organs are a particular challenge.

Let us know how it goes...

edgewound
07-07-2006, 06:26 PM
You should never drive a bass reflex system too hard below it's tuning frequency. The system unloads and the distortion increases markedly. If you really push it you will break the woofer.


Widget
4th order enclosure will drop 24dB/oct....like a rock...below the tuning frequency. The woofer cone will flail away like a shark out of water while doing nothing but making a spectacle and nasty popping sounds before it potentially dies.

Mr. Widget
07-07-2006, 06:26 PM
I would love to be able to get down to 16hz, but I realize that these drivers were not designed for that.If you want any appreciable power below around 25-30Hz you will need a different woofer.

Widget

Steve Gonzales
07-07-2006, 06:27 PM
You should never drive a bass reflex system too hard below it's tuning frequency. The system unloads and the distortion increases markedly. If you really push it you will break the woofer.


Widget Thank you Mr.Widget, I suspected that. I know that sometimes a higher tuning can also deliver more pleasing real world results. If a system's targeted purpose is to reproduce the lowest octave a pipe organ can produce (16hz for the best ones), do you think that the 2235H is up to the task?. I've been very suprized in the past to find out that the actual low frequency notes in some of my favorite recordings was no were near 20hz but more like low to mid 30's.

Edit: your responses came while I was typing.

Steve Gonzales
07-07-2006, 06:35 PM
As I had posted - and then deleted - approach multi source VLF with some hesitation. VLF from multi-sources can overwhelm and be fraught with cancellations / resonances. In my live applications, I am continually surprised at the ability to reduce either the number of subs and/or their gain, and achieve a cleaner, more intelligible response with greater tonality. I focus a lot on the bass - when it muds, the show can suck. In some clubs, I send a L+R sum to one sub and leave the other idle. Works incredibly well (better than reducing the LF gain).

For music, I'd start with two subs, at most, and measure the room response. Get the VLF in-balance with the other bandpasses, and apply proper EQ. If the sound is not pleasing, then consider more. In this business it's always a "less can be more" approach, especially when seeking good tonality. Organs are a particular challenge.

Let us know how it goes... Bo, I think it would be cool if you posted a picture of your particular KT E.Q.'s. I know what you mean in regards to "muddy" bass. Nice, tight, controlled bass is something to behold and can be difficult to achieve.

johnaec
07-07-2006, 07:10 PM
Bo - at those hot outdoor gigs, just put a little more ice cream on your head - it does wonders for cooling down 220hz... :p

John

Mr. Widget
07-07-2006, 08:57 PM
Back on topic...

This graph shows the theoretical maximum SPL of three systems. There is no room gain taken into consideration... however in a large room without corner placement you will get results similar to these... putting subs in corners and shrinking the room will increase the available output especially at lower frequencies.

The magenta plot is a 2235H as specified by the enclosure guide.
The cyan plot is a JBL Sub1500 in a 3 cu ft sealed box.
The yellow plot is the same Sub1500 in a 5 cu ft box tuned to 20Hz.

It is clear that this last choice is the only one that will give you any power at 20Hz and will produce over 100dB at 16Hz.


Widget

Zilch
07-08-2006, 01:12 AM
I've been very suprised in the past to find out that the actual low frequency notes in some of my favorite recordings was no where near 20hz but more like low to mid 30's.Playing the LF tones on a frequency disc is certainly an illuminating experience.

The fundamental on Jennifer Warnes's "Way Down Deep" is ~60 Hz, and anything below 40 Hz is down 40 dB here.

I'm not saying it's ALL an illusory numbers game, but much of it certainly seems to be....

Steve Gonzales
07-08-2006, 02:45 AM
Playing the LF tones on a frequency disc is certainly an illuminating experience.

The fundamental on Jennifer Warnes's "Way Down Deep" is ~60 Hz, and anything below 40 Hz is down 40 dB here.

I'm not saying it's ALL an illusory numbers game, but much of it certainly seems to be.... The only disc I've heard that contain super LF are put out by Telarc. I wish the music contained in them was my cup of tea.