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18" scaling? (Read 5810 times)
Jeremy
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Re: 18" scaling?
Reply #15 - 03/21/12 at 04:25:43
 
I put a third port in the bottom and found that it made me lose 3-4 decibels in the bottom range and gain 3-4 in the 50hz+ plus range. No good, 2x22" 4" ports is all the bottom box needs any more than that and you lose bottom end. I will keep posting the experiments as I go.

I currently have a 112db at 25hz and I am running off of the 120 15 amp outlet. The amp is clipping and I have to keep an eye on it not to over heat the speakers. Some sustained spikes in the 125+ db in the 30-35hz range. This really gets the house shaking nice. It is really deep bass that sometimes will have some subharmonics that hit hard and make things fall off of the shelf.
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Jeremy
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Re: 18" scaling?
Reply #16 - 03/22/12 at 08:16:27
 
Hmm this is not turning out like I would like. I can not get any more output out of the box without the upper speaker vented open air. I had read about this in this forum but thought this could be alleviated with proper port size and tuning. In order to give the upper chamber a chance in needs to be closer to 10 cubic feet and and a 40" deep port that is 10"x12". It looks like it will be back to the drawing board. The design has promise and I can still spend a couple more days with it before I take the circular saw to it.....
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Jeremy
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Re: 18" scaling?
Reply #17 - 03/23/12 at 04:05:42
 
Well.... I seem to have got something going with it. I kept my 8 cubic foot bottom, minus speaker and 22" of 4"abs ports. My upper 8 cubic feet minus  port volume of 24 3/4"wide x 4"high x 29"long. My center chamber is large enough but not critical. From 25hz to 85hz I am getting a 9db variation. With the gain turned up I am hitting 125-126 decibels all over that range and am right at the limits of my household wiring. I am popping the breaker box with extended run time. I can push 122db almost continuous. I am sure that with the wiring done and running my second amp I can push 130db at 45hz.

What is really nice about running center fire and 2 different ports is that you have different ranges that might conflict somewhat but begin to reinforce the harmonics of the building. In other words you get some huge rumble. My wife  could feel the bass in her chair watching tv in the next door neighbors house, not to mention they live 2 houses over and there windows where rattling to pieces.

I cant stress enough the need for a decibel meter. It is to easy to do something and not make an improvement and think that you did. I tested top and bottom speakers separately and combined using multiple variations of port size and number of ports. I really think that this is it and trying to get more output through dimensional changes would really sacrifice transition and balance.

Lining half the bottom chamber with foam got me 2db at 45hz and 3db at 50hz. The upper chamber it gained me 2-5 db. 2db from 30-60 and then went higher all the way up to 5db gain at 70hz. The upper box could have been bigger but I would have run into needing 3 sheets of 1"mdf for very little gain.

I have to go back in and radius some corners and glue the whole upper port together now that I know this design is a keeper. I need to finish beveling the edges of the center chamber which will stay open and mount my Lexan viewing port below the center chamber. Another days work ahead.

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« Last Edit: 03/23/12 at 04:30:37 by Jeremy »  
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Jeremy
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Re: 18" scaling?
Reply #18 - 03/25/12 at 23:05:13
 
Well I am now running a dedicated line to my Crown xls 5000. I popped the new 20amp breaker today showing off to the local stereo shop owner. I guess a 25 amp is in order.

He was impressed enough to offer me work and has a couple of custom jobs for me starting on Monday.... Cheesy

The gluing and beveling of all the port radiuses gained me 2-3db and I pegged my meter today at the 126+ db mark and did so hard. The shop owner commented on how he could feel the bass more than he could hear it until he got 40 feet away. Kinda strange, I think that maybe the sound waves could be so overwhelming close that the ear shuts down and at distance it becomes more audible because of separation of waves....?

I cannot use 2 crown amps because they will not each run 2.4ohm bridged, I tried and they shut down. I have to do some research and see if I can run 2 amps in parallel to double the wattage my speakers see. This in theory could allow me to run the amps at lower gain and increase my signal to noise ratio. However I assume this will lower the resistance the amps see and could cause me problems there. More research needed.

PS: Strike that last comment.... The crown amps will run 2.4ohm in bridged and do so running cool. I only ran them for half an hour at moderate levels but they did not get hot. With all settings staying at my baseline testing, the only change running bridged mono I gained as much as 8db. 3-5 db where it counts down low. The speakers showed no signs of over travel and now my 10 gauge wire running to them is getting warm so it is time for bigger wire. GOD be willing I should hook the 2nd amp up tomorrow and now I will need a a db meter that goes to 140+
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« Last Edit: 03/26/12 at 04:09:45 by Jeremy »  
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Jeremy
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Re: 18" scaling?
Reply #19 - 03/27/12 at 04:29:30
 
Well 2nd Crown xls 5000 hardwired in and I am no longer popping breakers. I think I may have come to the end of conventional exploring. Any questions feel free to ask them.

I have not reached 140 db as far as I know. I have pegged my meter and I am clipping both amps on 30 amp breakers and 12/2 wiring running directly to the amps and only them. I have to go larger wire to the speakers or double up my existing.

The local audio guys have been driving past me trying to show off their bass. I guess when they drive by the house when I am 80 yards from the road and their mirrors rattle they get impressed(or they hear the bass over their own).

I do have to say that the bass level are dangerous. Please resist the urge to stick your head in the center chamber, I tried it and my left eye wanted to pop out of my head and felt like it was going to. This is not something I would want to explain to my wife. Also 125+ dbs of 35hz and below causes all sorts of strange energy in the body. I felt levels of euphoria mixed with panic and pain all mixed together. It definitely hurts the ears, I mean it causes pain and I have to plug them when doing long exposure tests.

In order to go louder and deeper the box will need to be bigger and enclose better speakers and 220 volt amps running 7000 watts will be needed. I would have had to pay at least a $1000 a speaker to get more wattage and power output. And then my amps would not be enough. My pockets are not that deep so I will let the next guy do it, unless I win the lottery, or they go on sale Roll Eyes For now my home 12,000 watt entertainment center is done Cheesy
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Jeremy
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Re: 18" scaling?
Reply #20 - 03/31/12 at 02:07:57
 
Well it seams that not all is finished here besides cosmetics. I replaced my speaker wire with 4gauge from the amps all the way to the speakers themselves. I gained an absolutely unbelievable 13db at 15hz for a total of 109. I have 118db at 30hz, this is not a one hit wonder, this is continuous 30hz.

This I must add is at my test volume of minus -50db. I decided to make this my constant or control volume. This level keeps the amps running cool and max efficiency.


Like when a thunder clap strikes and the windows rattle and you are like wow that is awesome, this just keeps going and you expect it to end but it doesnt. I have a test cd that sweeps and it gets so crazy. The plates are now rattling off of the shelf's and  paintings on the walls are going crazy. The box is peaking with a continuous 50hz. I may have to sell something and buy the xxx18". They have nearly 3 times the vmax and it should get me more low db's.

I will keep updating and eventually post a spread sheet of various changes and db's gained from each change.
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« Last Edit: 03/31/12 at 19:24:37 by Jeremy »  
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Donnie
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Re: 18" scaling?
Reply #21 - 03/31/12 at 02:32:12
 
Jeremy, This is insane! You are my new hero. I say go for broke and build a second copy. If one is too much, two must be even better. I need a Housewrecker because I hate my neighbors, that would teach them to not build a house across the road from a madman.
Cudos!!
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Jeremy
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Re: 18" scaling?
Reply #22 - 03/31/12 at 04:39:27
 
Thanks, I unfortunately dont have the space or resources to have a second one. In reality it would gain me 4-6db and would cost a cool $2800. I cant justify it and times are to uncertain to spend the money.... But what I can do is have a boatload of fun with this one trying to extract every last db I can. Oh yeah and I am taxing the 200 amp main power lines from the pole to the house, I guess the power company could always upgrade it Grin

I had 2 people trespassing into my back yard a couple of days ago and I was bass testing. I think they thought a party was going on because I had the whole system cranked to Domino. Every word out of there mouth was f#%& I cant believe the bass. It was if they where following the Pied Piper.

I noticed around 2 hrs ago that it did not sound as good as it had been with my favorite track. The speakers have come to their limits and I had to turn it down. I lowered my crossover to accept only below 50hz and turned my low pass on at 25hz. It sounded good but is limited by the excursion and the amps and the speakers. Ugh.... I really do need better equipment,but... One of my closest friends reminded me that what I have is complete overkill for anyone and anything outside of a stadium and this I can rest easy with Huh

I will keep tuning Smiley
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gexter
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Re: 18" scaling?
Reply #23 - 11/06/12 at 22:21:55
 
Greetings
Just wondering how your HW played out for you and what you settled on after tweaks and mods.
I have built a couple of the Decware subs in the past.
Just curious how things turned out for you on this monster. Someone approached me to build a HT sub to fill a large room and I was going to go with a horn but this 18HW might fit the bill and use up less room.
I have always wanted to built a HW this big Wink

All the best,
Gex
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