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I dont doubt you guys, I just prefer the sealed sound, and I get just the low end thump I desire an expect, and more so than I did with the ultra I had.

As long as we're all happy, thats the main thing :T
I'm in agreement. Sealed boxes may be less efficient but there is far better control of the driver due to the box being sealed. Instead of a 24Db octave (or greater) rolloff below the box tuning frequency that goes out the window, instead you get 12Db/octave & far less group delay :T
Dan,

Agreed matey. Thats the important thing defo. The one thing I was going to say was even though my sealed sub had a high qtc, once EQd doesn't that pretty much go out of the window.
Not really no. To get a critically damped system Qtc needs to be around 0.5, anything above this will result in a slight "overhang" on any low bass note being produced. Just EQing won't get rid of that but you can get rid of it via some electronics. What you'd need is a Linkwitz Riley filter network, this can actually not only equalize the enclosure to a much lower frequency, but also get rid of that overhang in the driver response.

When i say overhang what i mean is the driver doesn't instantaneously respond to the signal applied & does stop as soon as the signal ceases. With some subtle electronics it can be made to do so :clap:

Qts of a driver is determined mostly by the strength of the magnetic field surrounding the voice coil. Low Qts drivers have a much better control over driver motion simply because the amplifier can act as an electronic brake or accelerator. With a high Qts or Qb the amp has less control & the driver can do what it likes in certain respects.

I always think about it in a way like cars. British cars tend to (sorry no offence meant at all) have good damping & do what they are told so react pretty well to changes (just like we'd like our speakers to do :D). American cars on the other hand appear to wobble for a good 5 seconds when they stop, something like a waterbed & this is the same kind of effect that an underdamped (high Qts or Qb) driver will display (though not as badly - it's just to give you the idea). To some extent reflex enclosures whether they are low of high Qts drivers will exhibit the same effects. Better by far to use a driver in any reflex enclosure with a Qts of 0.38 or lower. Any higher & you'll get the waterbed effect, with it getting vastly worse the higher the driver Qts.

Lower Q will result in a faster more precise response & better musicality, lower phase shift & group delay will also promote the very same. You can go too far though in which case you end up with aneamic bass :whistling:


Nice build by the way :bigsmile: Hope it all goes to plan!
 

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Elite Shackster
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I would just like to add that my drivers have a Qts of .36 :T, and my estimated QTC value is about .695, right where I want it :clap:. I did cost me more to use 2 drivers and go push/pull, but I really believe in the result. Its a personal choice thing though.

Graham, cant wait to get some feedback from 2 of those in your room, movies are certainly going to be powerful.
 

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I would just like to add that my drivers have a Qts of .36 :T, and my estimated QTC value is about .695, right where I want it :clap:.

Graham, cant wait to get some feedback from 2 of those in your room, movies are certainly going to be powerful.
Powerful, no kidding :yikes: I doubt you'll ever need to hit full volume with one sub, let alone a pair :D Remember we are talking UK front rooms here :rofl:

Just had a quick peak at your sub build Moonfly, nice indeed. The drivers being driven in phase that way will result in lower distortion due to cancellation of certain harmonics. 0.707 Qb would be regarded as good with a sealed box, i'm sure it sounds great!
 

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Elite Shackster
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Cheers for the comments.

Ive actually built a second one for a friend and it certainly is an animal, and runs clean at reference level. Like Graham though, he is bass nut (meant affectionately :D), and wants 2 in is room.

FYI, The push-pull alignment was a very deliberate choice :T, but we digress . . . . . . .
 

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Discussion Starter #65
Guys,

I will have another play on Wednesday and EQ the one sub. I played with some filters and got it pretty flat. I am obviously limited on position but I wonder if the second sub may even out that dip at 55hz. I can reduce the peak easily enough. I am very impressed with the bottom end I now have which is great. My main problem with doing another sealed sub is that I would never have got down any where near a qtc of 0.7 unless I put the sealed sub in a 28 cu ft box but then you go over max excursion very easily so the ported route based on my drivers is probably the best way to go.

I will probably have some questions over the weekend when I EQ both the subs.

cheers

Graham
 

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Elite Shackster
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I'm glad to see that going ported fixed your low bass wants.
Speaking of smoothing out graphs; hopefully I can order a AntiMode 8033 tomorrow or something for my room :bigsmile:
I'm anxious to see if it will make a big difference or not.
Ive heard a lot of good thing about the antimode, but when I demo'd one I found it didnt make a whole heap of difference for me, either on the graph or audibly. I felt it made the timing of my then sub a touch better, but not enough to discount placebo.

I think the main reason for this was that I already had a good in room response, plus I was already using Audyssey. From that I decided that if you have a decent room, and already have eq in place resulting in a good response, its probably not really needed. If however non of that applies its probably a very good tool.

Just my ten pence.

P.S, nice build BTW.
 

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Discussion Starter #69
Mike,

I will put up a pic when I get home. I did do it last night and there was alot more bottom end. I think it had a similar peak and null although my ported sub was slightly more I think. I haven't played around with positioning yet though. Probably best to wait until wednesday.

cheers


Graham
 

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Discussion Starter #70
Mike,

Here's the sealed and ported un EQd graphs. I still need to have a play with the sub facing into the wall or how it is now. I did try it facing into the wall quickly but the bass was over powering. Blue is ported and red is sealed.

cheers
graham
 

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Ive heard a lot of good thing about the antimode, but when I demo'd one I found it didnt make a whole heap of difference for me, either on the graph or audibly. I felt it made the timing of my then sub a touch better, but not enough to discount placebo.

I think the main reason for this was that I already had a good in room response, plus I was already using Audyssey. From that I decided that if you have a decent room, and already have eq in place resulting in a good response, its probably not really needed. If however non of that applies its probably a very good tool.

Just my ten pence.

P.S, nice build BTW.
Well, I noticed on Put On by Young Jeezy (I don't listen to rap; it was just a test) that on the second to the highest tone, I had to turn it down 4dB on that tone, then turn it back up 4dB for the rest of the tones on my receiver's sub channel to have it sound the same as the rest of the tones in the song. I'm crossing over at 80hz. I'm guessing that is my room boosting that frequency, or is that just how the recording is? Can someone test it that has a flat response to tell me if they have the same result with that frequency being louder than the rest of them??
(I don't mean to thread jack...)

I haven't tried having my sub face the wall yet. Maybe that could help somehow...
 

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Dylan,

I am going to EQ my single sub tonight and re run Audyssey to get a flat response. Can you give me a link to that song and let me know how many minutes in it is that you hear this difference and I will let you know how it sounds on mine. I tried Anti mode on my PC13 ultra I had and didn't noticed a real difference in sound. I didn't run any graphs but sound wise it wasn't worth it for me.

cheers

graham
 

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Well, I noticed on Put On by Young Jeezy (I don't listen to rap; it was just a test) that on the second to the highest tone, I had to turn it down 4dB on that tone, then turn it back up 4dB for the rest of the tones on my receiver's sub channel to have it sound the same as the rest of the tones in the song. I'm crossing over at 80hz. I'm guessing that is my room boosting that frequency, or is that just how the recording is? Can someone test it that has a flat response to tell me if they have the same result with that frequency being louder than the rest of them??
(I don't mean to thread jack...)

I haven't tried having my sub face the wall yet. Maybe that could help somehow...
I play Put On on repeat all the time! As soon as I got homke tonight! The 2nd lowest tone is a dead zone, the sub moves but you don't hear it as loud anywhere in the house... listening position 1, 2, the suck out zone (center of the listening room) or anywhwhere. But I LOVE that low tone!
 

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Elite Shackster
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Mike,

Here's the sealed and ported un EQd graphs. I still need to have a play with the sub facing into the wall or how it is now. I did try it facing into the wall quickly but the bass was over powering. Blue is ported and red is sealed.

cheers
graham
With headroom to eq in the bottom end, I have to say I like the look of the sealed response better, but here I go again :doh:. If the sealed sub is at its limit and you cant eq the bottom end up then the ported is the only way to go.

As before, the biggest point of note for me is that the sealed is considerably more expensive.
 

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Discussion Starter #75
Dan,

The biggest problem with the FI Q drivers which is where they differ from yours so much is that because the qtc is high the bottom end does need boosting alot. The advantage with the ported is I don't need to boost the bottom end as I have tonnes of it. I just need to EQ the peak and dip which I have already worked out the filters for with the BFD. If I could get a 0.7 qtc with a 8 cu ft box using the Q drivers then bingo but I need a 28 cu ft box to get to 0.7 qtc for a sealed sub.

I would say that the both graphs show exactly what the sealed and ported sub are meant to do. The peaks and nulls as we know are just the room.

I am going to re do Audyssey and EQ tonight so I will post some graphs for just the one sub. And then I will re do them both on Sunday (hopefully).

cheers

Graham
 

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Elite Shackster
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Yeah I know Graham, (I did offer to import some of my driver for you, but you just wanted bigger :D). The ported sub will have the opposite effect on what would be QTC in a sealed sub, so it will sound clean and deep, but the upper bass quietens off somewhat.

The whole aim of you build was to avoid this because of how you felt the Ultra was. It'll be interesting to see if these drivers are delivering that upper bass in a ported sub for you, especially knowing how critical you are.
 

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Discussion Starter #77
Dan,

From what I have heard so far it does. It sounds better than when I had just the one driver in the sealed box with ALOT more low end. I will let you know a bit later how it sounds once I have EQ'd it and re run Audyssey. One thing with the drivers is that characteristics is that they are very musical drivers so I am guessing that even in ported form they still will be.

cheers

Graham
 

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I play Put On on repeat all the time! As soon as I got homke tonight! The 2nd lowest tone is a dead zone, the sub moves but you don't hear it as loud anywhere in the house... listening position 1, 2, the suck out zone (center of the listening room) or anywhwhere. But I LOVE that low tone!

LOL. I'll have the bass balanced for what I like with the mains, then when that second highest tone kicks in, I gotta turn it down about 4dB to have it sound the same as the rest. Are you hearing the same thing Ryan? (The lowest tone REALLY moves my room around)

I hope the AntiMode will fix this. I think its a room problem because when I listen right next to my sub, every drop in the tones sounds exactly the same.

Graham,

I don't know if you already said this or not, but do you have the second sub finished also? Or are you still only running one?
 

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I'm the other way around... it has 3 notes then 4 notes... cycles back and forth. With the 4 notes, the highest one is quiet cuz my amps must have a small LPF slope starting low but gently rolling off. The 2nd highest is really loud cuz I have a nasty terrible 45Hz bass boost so that one just radiates. The 3rd tone just dies... empty... but the sub moves pretty good... port cancelation? A port resonance out of phase with the driver? Cuz it's not a room node/null/void... it's dead everywhere. Then the bottom note... love. Bliss. Excitement.
 
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