Home Theater Forum and Systems banner
1 - 17 of 17 Posts

·
Banned
Joined
·
1,074 Posts
Discussion Starter · #1 ·
I am totally lost. If I plot an 18" sub in over double the airspace sealed as ported to make up for volume lost by the port, I still get much more output especially down low even though the sealed box, 20 cubic feet, has a very low Qtc of .484 The ported sub is in 8.5 cubes to allow another 1.5 cubes to make 10 cubes... 1/2 the sealed box.

The ported sub smashes the sealed box... both 3000 watts (Maelstrom-X) sealed box HPF butterworth 20Hz ported butter 17Hz. Xmax limited.





 

·
Elite Shackster
Joined
·
7,142 Posts
Hi Ryan,

I get the feeling this one stems from the conversation I was having with Graham. I pointed out that his sealed sub probably sounded like it lacked bottom end because of its high QTC value.

QTC isnt really related to out and out performance figures and spl. Was it is related to it the sound characteristic you can expect to get from your driver(s)/sub. A high QTC will give you a very profound upper bass characteristic. This will give lots of audible bass, the real chest thumping stuff. A low QTC will subdue this sound and lean more towards this upper bass sound being much more understated in favour of a cleaner lower sound.

If the QTC is very high in room, it can become overpowering and even boomy, if its too low then you might find the sub seems to really rumble but you cant really hear it like you probably think you should. In each case the response graph for the sub will be quite similar (changing to reflect the volume of the cabinet), but the resulting sound will be quite different.

In relation to my preference for a sealed sub, you might recall I said I prefer the sealed sound, so if more output is needed I would rather add a second driver than a port. Attached is a model of the driver I'm using. One is a single driver ported tuned to 15 hz (basic untweaked model) and the other a dual driver sealed sub. Of course, my preference means I have to shell out on a 2nd driver and twice the amplification, but I feel the cost is worthwhile. Hopefully you can see the benefits of using a second driver instead of a port, although obviously at a cost. The benefits of porting are also obvious here, the chief of which for me would be the cost, especially as you dont gain the db increase higher up the range with ported.

In respect of what you have modelled above, increasing box size does alter QTC, but changes the working limits of the driver. The changed limits will usually result in xmax being reached with less power, so a loss in spl occurs. You'll lower the QTC for that deeper cleaner sound, but without the addition of more drivers and amplification, you also lose spl, which is where the port comes in.
 

Attachments

·
Banned
Joined
·
1,074 Posts
Discussion Starter · #4 ·
Moonfly... I was having trouble relating to what you were saying before, but now I understand. Also, I thought you were talking about lacking low end with the ported...not sealed. Thank you! I have new perspective :)
 

·
Registered
Joined
·
3,069 Posts
One thing I would say is that you are comparing a dual sub with twice the power to a single ported sub.
If you have two ported subs stacked on top of each other the ported sub would easily have more low end than the dual sealed sub. Two 5 cu ft subs stacked wouldn't be that big really. Its really only down to personal taste and not whether a sealed sub is better than a ported sub and visa versa.

With regards to my sealed sub, yes my qtc was high but it never sounded boomy at all. 10hz frequencies were not an issue at all but doesn't even compare to my ported sub. When I took one driver out it lost alot of mid bass punch when compared to the dual. It did sound slightly deeper which makes sense.

I would love to hear a low qtc sealed to compare to my ported in the real world. That would put to bed for me if in the future I decided to go for one or two maelstroms and whether to go ported or sealed.

cheers

Graham
 

·
Elite Shackster
Joined
·
7,142 Posts
One thing I would say is that you are comparing a dual sub with twice the power to a single ported sub.
If you have two ported subs stacked on top of each other the ported sub would easily have more low end than the dual sealed sub. Two 5 cu ft subs stacked wouldn't be that big really. Its really only down to personal taste and not whether a sealed sub is better than a ported sub and visa versa.

With regards to my sealed sub, yes my qtc was high but it never sounded boomy at all. 10hz frequencies were not an issue at all but doesn't even compare to my ported sub. When I took one driver out it lost alot of mid bass punch when compared to the dual. It did sound slightly deeper which makes sense.

I would love to hear a low qtc sealed to compare to my ported in the real world. That would put to bed for me if in the future I decided to go for one or two maelstroms and whether to go ported or sealed.

cheers

Graham
:) I concur. to me there is NO reason to seal
Like I said guys, I prefer the sealed sound. For me the extra cost of using a second driver and twice the amplification is one I am more than willing to pay, for what I feel are the audible benefits of a sealed sub.

If I wanted a second sub, I would pay the cost and get a second dual driver sub, which would out perform two ported subs. My personal opinion is that most of the argument for ported subs is one of cost, and given the savings a a DIY sub allows I feel I dont need to save more by using a single driver ported design.

Ported subs do sound lower (like a sealed sub of very low QTC, but without the spl drop), and if your after that really low sound, then ported is really the way to go. If musicality and upper bass prowess is also important then for me personally only sealed will do. Sometimes I feel the constant strive for very low clean bass has lead to people forgetting the upper sub bass regions a little, perhaps as subs are more about movies and less about music these days.

I know many will disagree, but you can feel free to demo my sub and critique it any time you wish :R.
 

·
Registered
Joined
·
2,431 Posts
For me the extra cost of using a second driver and twice the amplification is one I am more than willing to pay

If I wanted a second sub, I would pay the cost and get a second dual driver sub, which would out perform two ported subs. My personal opinion is that most of the argument for ported subs is one of cost, and given the savings a a DIY sub allows I feel I dont need to save more by using a single driver ported design.
Finally someone around here who feels the same way I do.


Don't get me wrong I'm not opposed to ported or horn subs at all. I have both of those too. The way I see it is each has strengths and weaknesses and are better suited to some applications over others. Plus that whole rag has been debated to death on 50 different forums at least. Neither is clearly superior to the other in the real world. I get tired of people saying that it's a waste to use sealed subs, or that ported can't sound good, or any number of other fallacies.

To each their own.
 

·
Registered
Joined
·
2,431 Posts
Ryan,

I still don't think you get where I come from with the sealed sub (or IB) thing. I'm sure most people wouldn't either.

If you want to maximize the potential of a single bass driver and get maximum performance for your dollar you'd use a ported alignment. (Technically you'd really want to do a giant horn or perhaps a huge 8th order BP, but let's ignore that.:sneeky:)

However...I don't care about the above at all. That's why my opinions are often at odds with many others.

What I do care about is maximizing the system performance using of the amount of space I have available for the bass system. By default this is not going to be a bang for the buck approach and will be more expensive.
 

·
Elite Shackster
Joined
·
7,142 Posts
I am with you Ricci. I can clearly understand and see the benefits of ported subs, and I know they can sound good and why they would be very desirable to many, especially for movies. I think its just a shame people overlook a sealed sub because they can see by implementing a cheap and simple port they get all that extra low down output, but then I can see why why they would go that way.

Horses for courses as they say :T

Graham, we'll certainly have to compare our subs one day, I think it would be very educational for us both, not to mention lots of fun :D
 

·
Banned
Joined
·
1,074 Posts
Discussion Starter · #12 ·
Ryan,

I still don't think you get where I come from with the sealed sub (or IB) thing. I'm sure most people wouldn't either.

If you want to maximize the potential of a single bass driver and get maximum performance for your dollar you'd use a ported alignment. (Technically you'd really want to do a giant horn or perhaps a huge 8th order BP, but let's ignore that.:sneeky:)

However...I don't care about the above at all. That's why my opinions are often at odds with many others.

What I do care about is maximizing the system performance using of the amount of space I have available for the bass system. By default this is not going to be a bang for the buck approach and will be more expensive.
I get there are laws. I get the trade offs. But what I am after is 18Hz on down. That is it. Maybe 8th order IS my thing? Maybe IB is my thing? Maybe I need to get 50 or 100 Shiva-X2 12's or Tempest-X2 15's, or 8 Fi IB3 18's and go IB if my basement is "large enough" for it. I can EQ and LPF 18Hz on up.

Talk me into it! I am OBSESSED with INFRA and I DON'T want flat.

I'm all ears Josh, and you know it! Ya I have my OCDs and misconceptions...but I will at least hear you out!

BTW.. I watched a few vids of the infra fan deal.. i didnt expect it to work as well as it seemed to... I even keep it in the back of my mind...
 

·
Banned
Joined
·
1,074 Posts
Discussion Starter · #15 ·
Will you be getting a Pro amp for your sub anytime soon? I'd really like to hear what your impressions are when you put some real power to your sub.
OH man am I excited myself, if I'm already getting out of this what I am... I was at Best Buy a cpl weeks ago getting Y splitters and I saw they added a pro/instrument shop since the last time I've been there..years ago. They had QSC, Mackie, Yamaha.. and I didnt realize how HUGE these amps are! Wow. They had an EP crossover or something so i almost asked for a price listing if they could special order... but I'm sure online will be the cheapest. I hate the 45Hz bass boost too.. how hard would they be to mod..take out?
 

·
Registered
Joined
·
2,431 Posts
I think first thing is for you to get one of the Behringer EP2500's. Look around for people selling theirs for cheap or other deals. $300 for a big amp. Tax return...Do it!. That should do a lot of damage with the sub you already have. You need to get some real power on it, that isn't boosted. Seriously I think if you got that amp and then maybe even another IB18 and re-did the enclosures that'd probably put one of these :bigsmile: on your face.
 

·
Banned
Joined
·
1,074 Posts
Discussion Starter · #17 ·
I think first thing is for you to get one of the Behringer EP2500's. Look around for people selling theirs for cheap or other deals. $300 for a big amp. Tax return...Do it!. That should do a lot of damage with the sub you already have. You need to get some real power on it, that isn't boosted. Seriously I think if you got that amp and then maybe even another IB18 and re-did the enclosures that'd probably put one of these :bigsmile: on your face.
I agree 100% I've been sayin all along to friends that love watchin me plot and play... "just watch, I get that amp and this 18 is just about enough or more"

no tax returns... child support :) and that's ok. but somethin else has been in the works for an eternity now... it's taking longer than hoped...but..but...
 
1 - 17 of 17 Posts
Top