| BassAwdyO |
In a quest for awesome bass, I've formulated this plan after some thinking.
Adire Tumult(old version which I have)
Adire ADA1200(which I just ordered last week)
Stryke18" passive radiator(perhaps 2 later, but we'll see how one does)
6cubic foot enclosure
I was going to simply use a ported box, but considering the length of port required to get infasonic tuning(between 10-16hz) I decided a passive radiator might be a better way to go even though it costs more.
I was looking at tuning right around 16hz in 6 cubic feet, but with a single passive it doesnt seem possible as the highest tuning allowed is 13hz. For two passives it is easily achieveable, but I dont exactly need 18liters of PR Vd! A single passive does run out of excursion at ~15hz with 1200watts of power, but considering how often there is content that low in the signal, and how often I turn things up all the way, I dont think it will be a problem.
So what I'm going to do is buy one passive radiator next friday. In the mean time I'm going to build a 6cubic foot sealed box which will house the Tumult and ADA amp for now until the passive arrives and I'll cut a hole to fit the PR. I think I'll eventually get a 2nd PR, but probably not for another couple weeks.
Construction will begin tonight and pics coming soon! Stay tuned
Any comments are welcome also |
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| Rademakers |
Do you use a lowcut and if so, how?
Wkr Johan |
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| BassAwdyO |
| quote: | | Do you use a lowcut and if so, how? |
I assume you mean a low pass filter. The ADA amps have Twin cascaded second order filters Q=0.707 adjustable from 35 to 110 Hz. The crossover network can be defeated, 2nd, or 4th order.
If you mean a subsonic filter, no I'm not planning to use one. |
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| Rademakers |
Lowcut = highpass
| quote: | | I'm not planning to use one |
Why, may I ask?
Wkr Johan |
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| BassAwdyO |
greater than 90% of the time I wont be going anywhere near full power. The other 10% of the time I'm not going to be playing anything with strong content below 30hz, much less 14hz where excursion reaches 34mm at 1200watts. It should not be needed
Simply put, I am careful not to abuse my speakers |
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| BassAwdyO |
I had a question... if anyone knows this it would be very helpful
What is the mounting depth on the stryke PR-18?
I emailed stryke a few days ago and havent gotten a reply yet. I'm guessing is probably not deeper than 6 or 7 inches, but its hard to tell from just a picture. I need to know so I can tell what kind of cutouts need to be done in the bracing. Does anyone know? |
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| simon5 |
| Try emailing Kyle at Acoustics Visions. He sells those too. |
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| BassAwdyO |
| I asked kyle, he didnt know, said to contact stryke... havent gotten a reply yet |
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| theduke |
| You can have a fold in the bassreflex channel, that does not harm very much. So you could build it out of wood and use the enclosure walls for it. |
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| BAM |
| I don't think John checks the old Stryke Audio email accounts anymore, but if you email him at sales@aespeakers.com then you might get a more expedient response. |
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| BassAwdyO |
| No ports for this one... A port with sufficient cross section will be very long and large. It will have a low pipe resonance frequency, and will also take up a good deal of room in the enclosure. The passive radiator approach will provide deep tuning without chuffing or pipe resonace while doing it in a minimal enclosure size |
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| nate |
Your sub sounds very cool!
Have you considered using the Linkwitz transform circuit that is built into your ADA1200?? I bet that you will still have more than enough power and then you could do away with the passive radiator and port.
nate |
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| BassAwdyO |
| i could use the linkwitz for sealed box, BUT if anything I'd probably just EQ it flat, and well I prefer the PR with ~7db gain in efficiency at 16hz and excursion reduction. And the 18" PR's look cool |
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| 454Casull |
| I wonder if anybody's ever measured the distortion of a PR. |
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| nate |
Absolutely. I was just wondering if you considered the LT. I've never tried it.
Best of luck!
Nate |
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| paulspencer |
I can understand why you are using a PR with the Tumult! Definately if it was to be a port, then not a slot port, that would just get too big. You would probably need a pair of 150mm vents, which would have to run external to get them tuned low enough.
One thing to keep in mind with PRs is that you don't want to use all of their VD, or even close. Remember a PR is a driver minus a motor, hence the output from the PR will have compression related to increased suspension stiffness with excursion. ie for a given PR, the more VD you have, the less excursion required and the less compression you will have. Unfortunately, the engineering of PRs will not normally match the Tumult with its flat BL curve and I believe also fairly flat suspension curve.
The VD of a passive is rated to the suspension limit, but do you think it's a good idea to be using them to their mechanical limit? Probably not a good thing for SQ!
Also consider things like having PRs in opposing pairs balances the moving mass. Mostly relevant to keep the box from moving, unless its so big that this won't be an issue.
To me this seems a bit ironic - you want a vented/PR alignment for the extra output, yet if this will be used for movies, not using a rumble filter will potentially lose you more output than using a sealed box with EQ will. If you are prepared to give up that much low end potential SPL, then why not just save the money spent on PRs and use a sealed box! |
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| theduke |
| quote: | Originally posted by BassAwdyO
A port with sufficient cross section will be very long and large. It will have a low pipe resonance frequency, ... |
That's right, 70cm will give sth like 200 Hz if I'm not totally wrong, you have to filter 4th order to get control of it. |
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| BassAwdyO |
Hey guys... dont be hating on the passive radiator approach
no matter how you look at it a ported or passive radiator is going to get me >7db @ 16hz. A sealed box of 6 cubic feet runs out of xmax before it even takes 1200watts at 16hz. A ported or passive radiator enclousre doent run out of excursion until 14hz with 1200watts.
The passive radiator should not suffer from linearity problems until below 30hz,... And well how much linearity below 30hz is required? Most subs have high non-linearity below these frequencys, so a passive radiator cant be smearing the sound any more really. The excursion reduction of the driver and low Fs of the pasisve would probably lower distortion? |
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| johninCR |
There are 2 problems I see.
1. Tuned that low it is likely to sound terrible for music, loose and sloppy and you can't stuff a PR like you can a port.
2. For HT the group delay is going to be so high that when you see the dinosaur step here on the video you'll hear, rather feel, the footstep like it was 10 or 20 meters further away. While it may feel cool and go unnoticed, it still won't be accurate.
Make some cool external ports, if cool is important. Then figure out a cool mechanism for closing them up.
Just my 2 cents. |
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| paulspencer |
BA, can you not see the contradiction here I mentioned?
You want the extra output so you spend money on a PR but you don't want to use a rumble filter because you don't need the extra output?!
If you have more output than you want, then why not save your money and use a sealed box?
If you want the ultimate in value for money, SPL and extension then use a very large low tuned vented box.
If you want the above but either can't achieve noise free ports, or want it smaller, then use at least a pair of PRs.
Convention seems to be to use a pair of 18" PRs for a single 15" high excursion driver, but my initial guess is that four might be appropriate for the Tumult.
I'd expect distortion performance to improve due to reduced excursion. |
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| BassAwdyO |
Paul, I can see the slight contradiction
but you said it best | quote: | | If you want the above but either can't achieve noise free ports, or want it smaller, then use at least a pair of PRs. |
Both noise free ports, and a smaller box are goals here
John, The group delay will be the same for the PR as a ported box would be. The peak is 46ms @16hz which quickly drops below 10ms at 17hz and doesnt do anything but get lower as frequency rises |
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| paulspencer |
I did some quick sims ...
Sealed 60L box with Linkwitz transform and 350w >>> 108db @ 20 Hz and with a rumble filter, xmax will never ever be exceeded
250L PR box with 2 x 18" PRs tuned very and 400w >>> 107db @ 20 Hz max SPL where <10 Hz will exceed xmax if you don't have a rumble filter
or 112 db @ 20 Hz if there is no signal below 11 Hz
if it were me, I'd be doing something more like this:
250L with 2 x 150mm ports with large flares tuned to 15 Hz >>> 115 db @ 15 Hz with a rumble filter where excursion below tuning will never exceed that above (fc @ 13 Hz, 6th order)
My main point is this: for movies, you only exceed the output of a sealed box by risking overexcursion, hence without a rumble filter you can't safely beat a sealed box. Why not go with a bullet proof design?
Hmmmmmm, I think you have a case of the "I just want to try it" factor with these PRs, am I right? Going with that theme, what would look really good is a reflective laminate on the PR. I've seen one which had a black high gloss veneer on a PR, it looked very good. |
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| simon5 |
| Nice, it looks like art, you gave you trouble with that complicated bracing hehe! |
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| BassAwdyO |
All I have to say is
Foxtrot, Uniform, Charlie, Kilo
That $600 amp is a peice. I got the box all done today, put in the sub, wired up the amp, put in a cd with some good bass... AND THE AMP WONT TURN ON! |
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| johninCR |
Since it's not up and running yet, I think you need very many air holes in your bracing. For someone worried about port noise, you sure didn't concern yourself with air moving freely in your cab. At least you have the big openings for the PR's giving you enough space to get in there and do something about it, but getting all the shavings and dust out is going to be a pain.
I think a change in signature is in order. |
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| paulspencer |
| I tend to agree with John, that the holes could be improved. To me they look too small. By forcing sound waves to move through such small holes, you may in fact alter the effective volume, or get some other unwanted effect. What you are trying to achieve is a compromise between structural rigidity of the bracing, and minimising the impact of the bracing, so that the braces occupy minimal volume, and the driver sees the entire volume as a single air volume. Add too much resistance through holes that are too small, and your box might start to behave like a smaller box. At which point this becomes a problem, I don't know. |
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| BassAwdyO |
I agree completely that those holes are small.... BUT my 3" hole cutter is more like a hole burner so I decided to just use the 1.25" bit. I'm fairly certian that there is a good deal of room in the box for air to move freely. If you look at the first and third pic I posted you can see that the middle section is very open and really needs no holes for air flow. Where the bracing is cut out for the driver there is also about 5"x 11" of open space on each side on the bracing panels you cannot see from the pics. Plus about 30 holes which should give a free space cross section of around 100in^2
It should be adequate.
The signiture stays.... It is indeed the golden rule(I didnt say I always obey it).
But, if you witnessed this enclosure in person, pushed it around a little bit, knocked on it, stuck your head inside and hummed a bit... I think you'd be satisfied... 1.5" thick MDF and all that bracing makes for one hell of a stiff, and heavy, box.
The amp is working. I feel like a moron really because the problem was a blown fuse. Who sends out brand new amps with blown fuses though anyway? Adire apparenly. |
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| johninCR |
Adequate on the sides, yes. From either side to the center, no. In fact your opening right at the driver has a greater crossectional area than the other hole in those 2 large braces combined. With that driver you're going to be moving alot of air, as will your PR's. I really do think you'll have enough resistance through the holes to cause the majority of the air to flow up through the opening at the driver, so we're talking about air flow from separate chambers, not acting as a single volume of air pressurizing and depressurizing.
Whether or not it's enough to make an audible difference is debatable, however, it's probably enough to affect your PR tuning. Who knows, maybe it will be beneficial and you invented a new kind of cab.
I understand the hole cutter was a "no way Jose". Much bigger and relatively few holes, freehand cut with a router or jigsaw is the way to go. Pretty internal braces isn't needed, a sledghammer won't break that cab apart. 1.5" mdf.....I hope you aren't planning a move any time soon and that it's supported by a concrete floor, the brace alone looks heavy. |
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| paulspencer |
| My initial impression is to agree with John on this one, however, looking closer I can see there appears to be a clear air path to all air volumes without having to go only through those holes. If I've missed something, and the only path to a pocket of air is through those holes, then you definately need to get the jigsaw and make them bigger. |
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| BassAwdyO |
paul,
I think you see it right.
I should have taken a picture from the side of the bracing and it would have been more easlily seen, but sorry, it happens.
1200 watts, and I still want something louder... maybe time for another driver or two, or three, or four |
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| paulspencer |
If you want louder, then perhaps you could consider something like what I'm planning - vented subs for LFE with midbass horns down to 40 Hz or so. This gives you more grunt for music, although to get down low you will of course still be displacement limited.
I still wonder if it's really worth tuning so low for your sub - you could get more output if you set a lower limit of 15 - 20 Hz |
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| johninCR |
Bass,
I'll give it one more shot for you. Your 2 biggest braces would create 3 lengthwise chambers in your cab if they had no holes and the 2 smaller side chambers will contain your PR's. You have a driver cutout and the holes which are the only way for air to pass between these chambers.
The big brace on the left has only what appear to be 1" holes, about 30-35 of them. Let's say it's 40, which is about 30sqin of area. Do you think that just three 4" dia holes would be sufficient? No way, yet three 4" holes is about 20% more area, not to mention that more holes equalling the same area have significantly more resistance than one larger hole. Since it's more like low 30s # of holes, you've effectively got TWO 4" holes, plus the space near the driver AND THAT SIMPLY IS NOT ENOUGH, PERIOD. You are forcing much more air to flow up around the driver basket.
I'm not being critical, just trying to help. Get the jigsaw out because I don't think you want to drill a couple of hundred more of the small holes. |
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| BassAwdyO |
John,
I appreciate your suggestion.
When I get the PRs I'm going to take the whole box apart to apply liquid nails and glue the 2nd wall of MDF to the first. I'll do something about those holes then.
My jigsaw is broken right now... which is why I didnt use it in the first place. I have two, but the one that works someone else has right now... I'll have to get it back soon.
Paul,
The "midbass" horns are a good idea. Its kinda PA style if you do it that way, but having a real sub below the horns makes it better. |
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| johninCR |
Don't take the box apart. Just 2 large rectangular holes in the center section of those 2 big braces is all you need. You've got the PR holes to work through, so don't let all that good work go to waste. Then it's a 20 minute adjustment plus some time to clean out the box instead of a rebuild.
I myself would measure results as-is, then cut the bigger holes. The effect may be able to be put to good use and learn something new, a box with aperiodic tuning of PRs. |
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| BassAwdyO |
It does sound like a usefull experiment to measure it both ways... Time to put that ECM to some use. I have done some recordings with it... and it is very dry
I need to take the box apart anyway to add liquid nails(to seal the cracks, although I havent heard a single airleak) and to also apply glue between the two outside panels. I'm doing double 3/4" mdf to make 1.5" walls and I only have screws holding the two boards together as of now, albiet very many screws. However I believe glueing the panels together will result in even more stiffness |
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| johninCR |
| I'm stumped is November "build it twice month" or do "Cubs fans always build twice"? |
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| BassAwdyO |
| November is not build it twice month, nor am I a cubs fan. Taking a box apart and screwing it back together is not difficult. it will maybe take an hour or two of my time. I have much time to waste. Designing and cutting out the panels is the hard part |
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| johninCR |
Bass,
With all that free time why don't you come down to Costa Rica for a couple of months? I've got a ton of audio projects that I'll gladly share. They range from things like ultra compact OB woofer cabs to testing whether cryo treatment and burnin of speaker cables make any audible difference. As an added bonus el cheapo room acoustic treatments that are better than the expensive stuff. |
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| BassAwdyO |
Costa rica does sound quite nice right now considering winter is rapidly approaching here, and hurricane season is over(I think).
Is there anything there that pays money or might advance my path to a career? |
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| Tom Danley |
Hi
You know, you could also build a horn for your driver.
I lean towards them myself.
If you want to try one, I’ll take a whack at some specifics for you since you’re a fellow Illiniosian who who’s prone to make saw dust.
You want to scare your self, a proper horn is how.
Cheers,
Tom Danley
How about the sox eh, man! |
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| BAM |
| A horn that would reach 27~25 Hz in corner loading has already been designed (you designed it), and while it's practical for pro sound use, for the performance gains in a small room like that, it's almost too big. This is subjective, I know, but it would take up almost 5-10% of any normal room! Unless you are planning on generating a DIY Tapped Horn, which would be something to see, just in general. I don't know if practicality would be one of BassAwdyO's concerns but he could just take a look at people who have done two LABHorns in their listening room and decide if he can part with that kind of square (or cubic) footage. |
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| BassAwdyO |
Thanks for dropping by Mr. Danley,
Yes, I would like to scare myself!!!
I actually had been considering building a horn for this driver in the past, but got sidetracked somewhere(probably around the design phase).
I definately am one fellow Illinoisian who will make some sawdust... and alot of it I may add(and probably not clean it up for, a little while).
What kinda size are we looking at here? Labhorn size seems acceptable. Bigger, might not go into my living room, but It could definately take up some space out in my 2 story 24'x24' garage!
MDF has also been on sale pretty cheap lately also. $12.99/sheet sure beats the typical $21.99 they had been asking for it. |
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| qi |
| quote: | Originally posted by Tom Danley
Hi
You know, you could also build a horn for your driver.
I lean towards them myself.
If you want to try one, I’ll take a whack at some specifics for you since you’re a fellow Illiniosian who who’s prone to make saw dust.
You want to scare your self, a proper horn is how.
Cheers,
Tom Danley
How about the sox eh, man! |
Hi Tom
I too would love to see a DIY Tapped Horn!
From what I have gleaned, it is not only a next generation LABhorn, but also a next generation acoustic cannon ... |
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| BassAwdyO |
OK so here's something VERY strange....
I can bottom out the sub easily at 30hz
Is WinISD just that far away from accurate on it's excursion calculator? it says with 1200watts I should be at right around 24mm one way @ 30hz... instead I'm past 34mm one way which it predicts at over 2500watts. Either WinISD is whack, or adire seriously under rates their amps... in either case I am scared for the life of my driver and I have employed drastic EQ cuts below 40hz.
If adire is under rating the amp by that much I'd be scared not only for the driver's mechanical stresses, but that the voice coil may fry!!! Of course the thermal rating might be under rated by that degree also, but I dont want to find out. |
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| paulspencer |
If it takes less power than simulated, perhaps there is more gain than WinISD predicts. It's also possible that the source itself has stronger than average content at 30 Hz which is effectively like getting more gain.
I can get more excursion than it seems to predict as well in some situations. This is even true with dance music with exaggerated midbass.
I have always suspected that you shouldn't rely totally on simulations to tell you how much power is required to reach xmax.
In your case this is a good thing and you have nothing to worry about. This is better than never getting close to xmax! It would be a waste to spend so much on 34mm xmax and only be able to use half of it!
| quote: | | If adire is under rating the amp by that much ... |
Now this is getting silly - be suspicious of the accuracy of a computer simulation system before something like this!
| quote: | | If adire is under rating the amp by that much I'd be scared not only for the driver's mechanical stresses, but that the voice coil may fry!!! |
That's like Bill Gates worrying he is going to spend all his money before he retires! :xeye: If you can't safely run a 1kw driver with 34mm xmax, then there is no hope for you!
| quote: | | Of course the thermal rating might be under rated by that degree also, but I dont want to find out. |
There is no reason to think this.
Adire website:| quote: | | all 3" diameter voice coil drivers are rated at 1000W |
Running a 1kw driver with a 1.2kw amp is very safe from a thermal point of view. You can easily use an amp rated at twice the thermal rating of the driver without cooking the driver as long as the continuous level is not running constantly four hours on end.
| quote: | | I have employed drastic EQ cuts below 40hz |
Knee jerk reaction perhaps?
I recall you saying you didn't need a rumble filter and now you want to cut back below 40 Hz?! You have designed an extreme EBS, hence you are giving up some midbass in order to handle more subsonic bass. If the midbass is starting to disapoint, then perhaps what you want is higher tuning. An EBS loses midbass output as the gain from the port is so far below the midbass. |
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| BassAwdyO |
Here's the strange thing though paul....
Doing a 10-100hz sweep I turn it all the way up. At 10hz xmax isnt reached, at 20hz the sub comes VERY close to XMAX, a bit above 20hz it goes beyond Xmax. I turn it down. Excursion INCREASES up to about 30hz and then starts to decline once again to a safe amount for full power once again at ~40hz. Now Maybe something's wrong with my soundcard or the signal generator and the reference level is going up and down, but something funky is going on here. Looking at the waveform of the soundcard output it shows no clipping through the entire sweep.
It seems like the excursion curve is resembling a BR although at this point I'm only using it as a sealed box. Maybe something funny is going on inside the box with those holes? |
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| paulspencer |
There must be less gain in those sweep signals.
Do you have the same strange excursions with individual sine wave tones? |
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| Tom Danley |
Hi
I have some time to play this week.
Which exact driver do you have?
I ask because the T&S parameters have changed on Dan’s drivers I think as time went on.
In fact if you have those for your driver please post them.
Tom Danley |
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| BassAwdyO |
I havent done extensive testing yet... It takes time.
I was thinking about a higher tuning... Higher tuning would add more midbass output, however I still want those infrasonic lows and it would kill that, so perhaps a 6th order bandpass would really be the ideal enclosure
Or a basshorn! |
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| BassAwdyO |
Vas 160L
Qts .36
Qms 4.3
Qes .393
Fs 19hz
Re 3.227ohms
Le 4.2mH (series wiring?)
Xmax 34mm
Z 4ohm(series wiring)
SPL 86.48db
Pe 1600watts
BL 18.5N/A
Dd 12.16
Sd 749cm^2 |
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| BassAwdyO |
Boy oh boy... This is getting me excited!
Thanks in advance Tom!
If you need anything else just say the word |
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| paulspencer |
Perhaps you could suggest what kind of size or dimensions are your limits. What size room is this going into?
Heck, a single 15" Tumult is a toy really, get another one and push pull mount in a 15 Hz expo horn I say! |
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| qi |
| how about 18" x 18" x 84" (hint hint hint) :D |
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| BassAwdyO |
| I will neglect dimensional constraints.... As big as it needs to be, is is big as it needs to be(I can MAKE SPACE) |
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| paulspencer |
| So 17m long is fine then? |
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| BassAwdyO |
| quote: | | So 17m long is fine then? |
I'm allowed to fold it right?
what are we going for a 10hz cutoff? I think a 20hz horn would be all that I could possibly need |
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| noah katz |
"I was looking at tuning right around 16hz in 6 cubic feet, but with a single passive it doesnt seem possible as the highest tuning allowed is 13hz."
I believe the diaphragms are just MDF, so you could thin it.
But I'd just get the second one.
"Remember a PR is a driver minus a motor, hence the output from the PR will have compression related to increased suspension stiffness with excursion."
Also remember that the suspension spring is in parallel with the air spring, which is stiffer than the suspension for any Vb less than Vas.
This reduces the total effective nonlinearity.
"1. Tuned that low it is likely to sound terrible for music, loose and sloppy and you can't stuff a PR like you can a port."
Actually the lower the tuning, the closer a vented/PR system's behavior is to a sealed systems in all respects. At Fb = 0 they're the same.
"2. For HT the group delay is going to be so high that when you see the dinosaur step here on the video you'll hear, rather feel, the footstep like it was 10 or 20 meters further away. While it may feel cool and go unnoticed, it still won't be accurate."
This has never been found to be the case in tests designed to show audible differences caused by group delay.
"For someone worried about port noise, you sure didn't concern yourself with air moving freely in your cab."
While ports have high air displacements and velocities, their much lower from the drivers and PR's because of the much larger areas.
"You can easily use an amp rated at twice the thermal rating of the driver without cooking the driver as long as the continuous level is not running constantly four hours on end."
Maybe seconds on end.
As Dan Wiggins said here
http://forum.carstereos.org/showthread.php?t=55762
"...the voice coil in a Tumult - 3" diameter an 1.6" long - reaches 200+ deg C in a matter of a second or two with 1000W of power."
And Tom could tell you a thing or two about speaker rated power vs. real power :)
Just consider what 1000 W does to the thick fan-cooled heating wire in a portable heater, and think about the same power applied to a voice coil confined in a small space, and the speaker all sealed up in a well insulated box.
I'm surprised speakers don't burst into flames with fair regularity. |
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| johninCR |
| quote: | Originally posted by noah katz
"1. Tuned that low it is likely to sound terrible for music, loose and sloppy and you can't stuff a PR like you can a port."
Actually the lower the tuning, the closer a vented/PR system's behavior is to a sealed systems in all respects. At Fb = 0 they're the same.
"2. For HT the group delay is going to be so high that when you see the dinosaur step here on the video you'll hear, rather feel, the footstep like it was 10 or 20 meters further away. While it may feel cool and go unnoticed, it still won't be accurate."
This has never been found to be the case in tests designed to show audible differences caused by group delay.
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Noah,
I guess we should just listen to sine waves at Fb=0 , so we can't hear the difference. Maybe there's no sonic difference at that frequency. I never bothered to test it. Ports and PRs are a great shortcut to higher SPL, but eventually we all grow out of that in the search for better bass. |
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| noah katz |
"...but eventually we all grow out of that in the search for better bass."
That's rather presumptuous (hint: speak for yourself). |
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| BassAwdyO |
| quote: | | Actually the lower the tuning, the closer a vented/PR system's behavior is to a sealed systems in all respects. At Fb = 0 they're the same. |
I very much share this view. One way to demonstrate this that will make things plain as day and night is to look at the group delay.
Sure there's a huge peak in group delay at resonance, but that's all the way down at 16hz and for music, there really wont be any effect(unless of course your music contains strong infrasonic output).
But even in the case where there is output that low and it suffers a large amount of group delay we must realize how insensitive the ear is to such low frequencys. Then you got to figure how noticeable a ~50ms delay is for things to start vibrating.
For HT the soundtrack is going with video and as I understand the human eye doesnt descriminate beyond 16frames per second which corresponds to one frame every .0625seconds. If you see the dinasaur's foot stomp down and one frame later(.05seconds corresponding to 50ms of group delay) you feel the impact it will probably seem pretty accurate. |
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| johninCR |
Bass,
Do yourself a favor and make the thing ported. Play some music with the port open and with it stuffed. Then come back and tell us there's no difference. You've been brainwashed by theory. In the real world there's a difference.
The designer of your particular driver used to have specific recommendations on their site regarding different ported alignments for their drivers and guess what? Big low tuned enclosures were recommended strictly for HT use and not music. Why? Could it be because there is a significant audible difference? Of course there is. |
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| noah katz |
The Tumult does have a highish Qts more suitable for sealed designs.
It would have to be tuned very low not to have a response rising above reference level in the rgion of Fb and above, which indicates resonance-augmented output aka ringing. |
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| simon5 |
| Yeah john, you're right, there's a difference, he'll see that ported is way better. |
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| johninCR |
| quote: | Originally posted by simon5
Yeah john, you're right, there's a difference, he'll see that ported is way better. |
Noah,
See, Simon5 is on his way to proving my earlier point. It also looks like the Computer Engineering curriculum in Canada is the same as it is here in Costa Rica and no real engineering courses, physics for example, are included. |
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| simon5 |
You're stating in plain that sealed is better and provide no proofs at all.
When I state in plain that ported is better and providing no proofs, you get frustrated, that's was exactly what I was looking for, what would you do if I do the same thing as you did hehe! ;)
Don't ***** Canada engineering, it's not that bad. We do have many pure physics courses and maths courses. It's about half and half. So we do two years of physics+maths and two years of engineering, with a few not useful courses in the way like everywhere.
Now, IMO, ported is better because the frequency response of a EBS tuned enclosure is flat in room. To achieve the same FR, you need to EQ the sealed enclosure quite hard, so you get almost the same group delay and you need way more power so might exceed the powerhandling of the driver. You'll also get way more distortion because the driver must work really hard to get on par with the EBS enclosure.
When tuned low with EBS (<18 Hz), the group delay at 20 Hz is usually under 25 ms (half a cycle behind), if you tune <16 Hz, then you get under 20 ms at 20 Hz. So that means you're about 0.02 second late on that 20 Hz tone which you'll feel more than you'll hear it. It's also about 2/5 cycles behind, it's not that bad. Then if you aim for 14 Hz tuning, you get under 15 ms, so that's less than 1/3 cycle behind at 20 Hz.
Of course a linkwitz transform for example would yield lower group delay, but at what cost? Seriously compromised SPL, way higher distortion, lots of wasted amplifier power, higher cost, etc.
So, in the end, IMO SQ is better for a ported enclosure versus a sealed enclosure at the same loudness.
Anyway, we have all a different opinion because this is audio, subjectivity rules! Who is right, who is wrong? Would it matter anyway? Play the music the way you like it! :D |
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| johninCR |
Simon5,
I'm sorry, I wasn't bashing Canadian engineering. It was more a poke at Costa Rica Computer Engineering, where they don't take ANY basic engineering courses. No physics and almost no electronics, so I don't understand how they can use the term engineering. Your curriculum sounds like it makes more sense to me and you won't end up a glorified programmer.
I'm not going to get into a sealed vs ported debate. I've moved on from both except in my HT where I still use an EBS Maeltrom, which is fine for HT and fine for music with the ports stuffed and the difference isn't what I would consider subtle in the bass region.
If you like an EBS sub for music, maybe you listen to music that contains a lot of very low frequency content, so the added low end is welcome. Have you even done any critical listening to compare the ports open and closed?
Noah made the point that GD effects are not audible. GD may not be the culprit. If not, then what is? Since ported helps control cone movement, maybe it is the forces inside the box that help control excursion that are detrimental to SQ. It's not my imagination and I don't think it's a matter of personal preference once someone critically listens and hears the difference.
Another thing supporting Noah's point is that dipoles don't exhibit this problem and it would make sense that the rear wave would be detrimental to SQ if GD is. The difference is that with dipole the cone operates freely vs more forces inside the box affecting cone movement with ported than with sealed. |
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| noah katz |
"GD may not be the culprit. If not, then what is?"
Have you compared the obvious - freq response?
It could be the differing responses of the ported vs. sealed, and/or that the ported version has more output at a room mode freq, which is a much bigger determinant of bass SQ than the difference between ported and sealed.
I'd sum the whole thing up this way: In any situation where you need more than moderate low bass output levels, a competently designed ported system will sound better.
The debatable disadvantage of more GD is nothing compared to a driver driven into nonlinearity and/or overload. |
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| simon5 |
It's really hard to really compare ported vs. sealed because they are so different.
IMO, you would need to compare a sealed LT and a EBS, then I think EBS would win if the sealed LT is designed to have the same frequency response in room. Distortion would be way lower. The box could be much bigger, of course. |
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| noah katz |
"It's really hard to really compare ported vs. sealed because they are so different."
Seems to me that makes comparisons a lot easier.
Anyway, GD is always mentioned as the reason ported is inferior, so to test that both should be EQ'd to the same freq resp to eliminate that variable.
Also, for most people the room will be a bigger determinant of bass SQ than the sub (ring times much longer than even a mediocre sub), so anyone who's halfway serious ought to have EQ. |
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| johninCR |
| quote: | Originally posted by noah katz
Also, for most people the room will be a bigger determinant of bass SQ than the sub (ring times much longer than even a mediocre sub), so anyone who's halfway serious ought to have EQ. |
Bass management processing is just a bandaid that masks the problem somewhat. It doesn't correct the problem. Anyone who's more than halfway serious ought to have physical bass treatments in their room. That why I constructed my room so that 50% of the walls and 100% of the ceiling are panel bass traps tuned to different frequencies and the long side wall of bass traps forms one very low tuned bass trap using the sealed airspace and wall behind that.
Using the rock music that I usually listen to, I think the EBS sub I used, which is tuned to 16hz if I recall correctly, has a pretty comparable response sealed or ported from 40hz up to the 80hz cutoff I use on the HT rig and that music doesn't have much content below that. Just because computer modelling predicts an equal response doesn't mean they sound the same. |
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| noah katz |
| You're correct, room treatments are the place to start. |
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| BassAwdyO |
John.... one question I have is this, Where is your first port resonance.
EBS enclosures Typically have LONG ports especially if it happens to be a smaller box with a larger driver(which is definately the case for Tumult). The high excursion of the sub only makes it worse because the cross section of the port has to be larger making it even longer for such a low tuning.
When you get a first port resonance at 80hz, even if you cross over at 40hz 24db/octave the port is probably going to muddy things up a bit at 80hz from the port. If you cross higher, the problem gets ALOT worse. As I understand passive radiators negate these effects, one reason why I opted to use them. |
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| johninCR |
Bass,
I'm not into ported enclosures and built the thing 2 years ago. Going from memory it's 360 litres (maybe 320L) with dual 4" x 17" ports. I think the straight parts are 15" and both ends are flared.
It's not a resonance or room modes. It's the alignment. I really can't believe that you guys really can't hear the difference. |
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| BassAwdyO |
where are you crossing at dude?
Having extremis midwoofers in my mains puts me down to about 42hz f3 and crossing below that isnt seriously detrimental. The sub's band is very small for music. Either it's not a critical portion of the frequency spectrum, or my ears suck, because I cant tell a difference(except in the intensity of infrasounds) |
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| noah katz |
" I really can't believe that you guys really can't hear the difference."
You haven't addressed what difference you're referring to.
Of course different FR sounds different. |
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