late night thoughts about DIY vs Comercial - Page 13 - AVS Forum
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post #361 of 682 Old 03-23-2008, 06:09 PM
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Air spring distortion!!!

That has to be a world first,who measured this distortion ? Even Bob Carver uses the patanted "Air Spring" in his subs. I think Bob Carver knows a thing or two about audio.


Commercial has caught up with DIY,value wise. Not a chance,as the designers,employees have to make money to live.

A few would be surprised to learn the actual cost of parts on the popular designs. A small fraction of the selling. Shady weekend sped up DIY done by someone with little know how and ill equipped in tooling is a grand waste of time,DIY done right with specific goals met beats commercial each time out.


I have subs ,very high quality commercial subs,my DIY equal or best them(equal in SQ and best in output with better extension) .

One thing I will not tackle at this time is full range as the crossover is a beast few master,a crossover makes or breaks speakers.Here quality from Dynaudio and TAD will do for now.

Ask yourself mortal , do you have as much displacement as me ? The answer is no unless you have a Windmere fan sub.
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post #362 of 682 Old 03-23-2008, 06:21 PM - Thread Starter
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I don't fully believe that to be the case, same subject matter but two different worlds IMO. I could happily exceed virtually any loudspeaker design on performance, looks and/or budget. Not so sure about subs though, there's some really strong designs available in commercial land from places like Epik, JL, ED, SVS etc and for reasonable money. It wasn't always like that but DIY subs still have a strong niche for the dedicated, creative, curious or power crazy. There's no doubt if you want ultimate and you've got the right sort of personality then DIY has a strong argument to offer.

Definitely two different worlds but those worlds do collide more then people think around here.

btw, I have DIY subs instead of comercial subs because I built them into the walls and ceiling when I buit the house 2 years ago, that is how I got around the whole monster sub taking up too much room problem.

Heck I just realized two days ago that the Castle sub is the same design (15" driver, 6" port, front firing) as my current TC2K 15" ported box. My box is 10" longer though.

Each of my TC2K boxes will cost me close to $500 in just parts alone. Build time and finish is ignored in the DIY world but if I was to place my $/hour I charge in my business that would be probably over $2000 in time costs. Obviously I can add that to my costs.

We do have to place value on the finish and size too because I think that matters to more people out there then just the DIYers here. Obviously this crowd doesnt really care about professional finish (although some are amazing!!) or size from the pics (and that is cool for them!! Im not bashing).


I care about finish and size. Meaning two subs side by side, If one performs better but its HUGE and UGLY. I will take the other one if the performance is still great but not as great. Too me having the BEST performance overall isnt great if its sticks out like a sore thumb in the room.

It is not "open-minded" to reject knowledge - Bob Lee
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post #363 of 682 Old 03-23-2008, 06:24 PM - Thread Starter
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power crazy

That is the other thing that makes me wonder.

I dont know the last time I played anything at reference level so all this Max SPL and so on is meaningless when we are just watching a movie at normal levels isnt it?

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post #364 of 682 Old 03-23-2008, 06:57 PM
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Originally Posted by Avus View Post

BTW I am thoroughly enjoying this debate.

I am too - aside for ssabripo's weak debating style - which is why I keep wasting time here.

Quote:
Originally Posted by TheEAR View Post

You need an optimal driver ,for IB use drivers are the cheapest of any suitable design. As the BL can be very low compared to what you need fora sealed and ported sub.

You do not just close it and port it...an IB driver used in aported box would be far from ideal.

EAR, this has been said about 5 times now by 3 different people - please post the name and parameters of some (more than one) IB drivers not suitable for large and low tuned ported designs. Otherwise, why keep bringing it up? I'm not upset at all, I just want to see some of these mysterious drivers.

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Originally Posted by ssabripo View Post

Really sad to see you still think it is just a big ol sealed alignment

Please explain how it isn't. The two posts you linked to (from this own thread none the less, oh boy), don't explain anything to the contrary. I'm not trying to be crude or rude at all, but each time you post you get further and further from making sense. Please don't respond with some weak insult, cause I'm trying to be genuine.

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Originally Posted by Avus View Post

I did gain bass extension. As you said a driver can only put out so much air. With my 2 RL's max displacement was ~13L. With my IB I will be pushing 29L of air...an increase of 123%! That ought to really pressurize my room nicely!!

The person you quoted was talking about using a driver in a smallish sealed enclosure vs an IB, you are talking about two different drivers in different quantities. Also, for the second time, nobody but YOU decided to switch from using two RL-p18s to 4 Fi Q18s, so why put the onus on the alignment? Nobody stopped you from building a quad Fi Q18 SLLT but you.

Quote:


This seems completely the opposite to me. My IB will run much deeper than the dual LLT's and offer more output everywhere except right at tuning.

In this quote, I was comparing a set number and type of drivers in an IB vs a SLLT, you are misreading and going down a side path with your responses.

Quote:


C'mon, different drivers are suited for different enclosures as everyone knows. The RL is over kill for an IB install IMHO. IB installs don't need that much motor force which enables us to get the drivers much much cheaper.

Same to you as I said to EAR, show me these mysterious drivers. You and EAR might be shocked to learn that a large ported design also doesn't need or want high BL, as the "large" enclosure means a lot of volume. You guys are off base in your assumption.

Quote:


The build materials don't cancel themselves out. The binding post and such do which is why I did not list prices for those but wood and the sonotube is much more $$ for the LLT than building a manifold out of some mdf and osb. Plus, the sonotube takes much more time to construct vs the manifold not to mention getting the damn tube home!

If you want to be fair, you should at least try to maintain the same build standards between the two designs, which is why I mentioned you'd need a really thick baffle to match the rigidity of a 3 layer endcap for a single driver. But even if I gave you that one, if you knew you had an adjacent space, nobody stopped you from going SLLT. Nobody said you had to use a tube enclosure, the adjacent space would have worked just fine.

Quote:


As for EQ, why do you think that the IB's somehow "require" an eq but LLT's don't?? I could say that an LLT needs it more to cut the lower freqs so they don't bottom below tuning. Seems silly.

For your first part, because it's the truth - IB will have a rolloff whereas a LLT will stay flatter longer. If you want to match the FR linearity of the LLT, you will need to boost the low end of the IB. For your second part, that is false, and has been a weak out some have used for a while. Nothing silly about it.

Quote:
Originally Posted by penngray View Post

Sorry that isnt true.. its costing me more to build two ported boxes then it did to build an IB. I originally built my IB with drivers that cost $90 each, 4 18" driver did cost $100 more then 1 TC2000 15". I upgraded too 4 Q18s for $1000 (new ones are EVEN cheaper). IB drivers are REALLY CHEAP. Check out the comparison chart....

Again, if you already had an adjacent space, you could have just gone SLLT - nobody is forcing you guys to build a discrete enclosure except for you. Then you are trying to use that as some type of reasoning. And now I say the same to you as EAR and Avus, show me these mysterious drivers that won't work in a ported application. It was you who chose the drivers, nobody forced you to pick driver X over driver Y, you could have used other, cheaper drivers. It's not really a good argument.

Quote:


a ported box.....ugh. Routing, re-inforced bracing, fitting the port, finishing the box and so on. Much more time. Also have to figure out port size and length, Box CF and so on. None of that is need in an IB.

I agree that if you want the simplest build possible in terms of actually having to do something (this is DIY isn't it?), an IB is pretty easy - and I think that's why a lot of people pick it. But if you spend a few more hours, you get more performance, and to me, that is worth it.

Quote:


You can not talk about cost unless you add this into the mix. I suspect you will ignore it like you do with any sort of cosmetic value but its there for the rest of us.

Maybe DIY isn't for you then, I dunno. Most other DIY owners tend to like working on such things. That's why you constantly see them working on one thing or another, even if they don't need it.

Quote:


BTW, you havent prove anything either you know so your Nothing to the contrary has been proven by anyone opinion holds no water WHEN EVERYONE else disagrees with you. The burden of proof is actually on your lap not ours.

What exactly do I have to prove? That porting creates lower distortion, more low end output, greater FR linearity, etc.? It's already been proven. You can find all the detaile dmeasurements you need over at hometheatershack from Ilkka. What else do you need to know?

Quote:


I cant believe there is actually an arguement here

You need to understand the basics first, then it will make more sense.

Quote:
Originally Posted by bosso View Post

Please show me Ilkka's test of any ported sub that shows 'greater FR linearity and lower distortion'?

You already know where to find it. TC2k ported is superior to TC2k sealed. If you care more about <10hz than you do >10hz, more power to you, but no need to ramble on about some left field concept.


As for the doubting of air spring distortion, it comes directly from Linkwitz, the guy who seems to be everyone's hero. The smaller the box and greater the displacement of the driver, the greater the air spring distortion. You can find it in his "closed box" spreadsheet here - he uses the equation: air spring distortion = 0.014*(Sd*Xmax) / enclosure volume.

Quote:


I need help with this one. Box coloration? Exactly what sort of coloration does a box contribute vs anchoring the baffle to a wood frame structure?

I agree with bosso here, as long as an enclosure is well built and braced, it will not impart much, if any, coloration. A 1.5" thick, ~78" x 22" IB baffle trying to maintain rigidity while holding four high excursion 18" drivers in array on the other hand, well, I wouldn't be so confident. If I were to mount 4 high excursion 18" drivers in array to a single baffle, that thing would be at least 4.5" thick before bracing.

Quote:


Close off the IB?

Reduce the rear chamber volume.
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post #365 of 682 Old 03-23-2008, 07:13 PM
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Originally Posted by SteveCallas View Post

I am too - aside for ssabripo's weak debating style - which is why I keep wasting time here.

then don't waste it buddy. If by weak you mean owning you every time and proving the point, then sure, my debating style is weak .

unlike yours of course, which is an illogical, fictional, irrational based, sugar coated in the good old SteveCallas "fact and logic" veil...........right?

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Originally Posted by SteveCallas View Post

Please explain how it isn't. The two posts you linked to (from this own thread none the less, oh boy), don't explain anything to the contrary. I'm not trying to be crude or rude at all, but each time you post you get further and further from making sense. Please don't respond with some weak insult, cause I'm trying to be genuine.

don't dish it if you can't take bud... I also tried to be geniune and trying to understand your position, but all I'm getting is the same nonsense cloated in the "it doesn't make sense", "you don't know basics", etc, etc.

I posted those links IN THIS THREAD on purpose...did you not get the point of that either? Very good info in them, so re-read. An infinte baffle is NOT a pure sealed alignment in a bigger "box"...there is more to it, so again, read those replies, go back to HTS-infinite baffle forum, the cult forum, google, etc, and tell me exactly how you can't grasp this.

i'm being geniune and trying to get back to intelligent debate here...
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post #366 of 682 Old 03-23-2008, 07:25 PM
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Please epxplain how it is not - I see nothing in those posts that does. Goneten was wrong on just about everything he said. Thomas didn't say anything explaining how an IB is not essentially a large sealed enclosure. Do you yourself even know? Please spend 2 minutes and explain it.
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post #367 of 682 Old 03-23-2008, 07:27 PM
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Quote:
Originally Posted by Steve Callas View Post

Again, if you already had an adjacent space, you could have just gone SLLT

For those who haven't followed the thread Steve always references when talking about converting an IB into an LLT/SLLT, here's Steve's "proof" about the 'superiority' of the LLT/SLLT.

Each plot is the output of a pair of RL-p15"s

Purple line is the SLLT, green line is the IB....

Looks like the SLLT plays a lot louder right? Not mentioned is the fact that the IB measurements were taken with 750 watts powering the IB, while 2400 watts were powering the LLT.




Below is Ilkka's sim for the IB to LLT conversion with the audible passband indicated in red. (note Rodney can't use a higher XO point, since he has a major problem with port resonances and no one posting on HTS has a clue how to tame them).



Again here are Rodney's measurements with the same passband indicated in red...Since the profiles of these plots are virtually identical the gains projected by the sim aren't there. REMEMBER the amplitude differences in the plots are a function of more than 3 times more power going to the LLT



So where are all the gains created by this conversion? The plots below show where the gains occurred, in the inaudible region from 15Hz-16Hz down = room shake. IMO a rather poor trade off for having a huge port resonance that forces the use of a 60Hz or lower crossover point...

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post #368 of 682 Old 03-23-2008, 07:32 PM
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Also, ssabripo, here's what your buddy Mark Seaton has to say on the matter:

Quote:


Originally Posted by Gertjan
I was wondering beyond which size a box would be considered an infinite baffle. I assume the absolute size depends on the driver, but is there some rule / formula based on the driver parameters? If i wanted to make a box with let's say two 12" Dayton DVC drivers (if that's even enough for an IB setup), how big should the box be for it to be considered IB?



MarkSeaton: That depends on who you ask or what the perspective is.

More recently the "IB" implementation in a home with drivers mounted to a baffle or manifold between the listening area and another large/open space has become the popular meaning. In this context, many seek to have the rear space provide a minimum air-spring to the driver and have a minimum impact on the free-air response of the driver. The common rule-of-thumb suggested to achieve this is 10x the combined Vas of the drivers used.

If you look at classic loudspeaker textbooks, they define things differently. Originally, the term Infinite Baffle was used for large sealed boxes. The concept was to simply not allow the rear output of the driver enter the listening space. They generally made the boxes as large as practical. In these cases, the box does modify the free air response, but the influence of the air-spring on the system was still lesser than the driver's own suspension. Acoustic Research was the first company to employ the acoustic suspension design. The basic concept was to replace the stiff and fairly non-linear suspension (spider & surround) of that era's drivers with very soft parts and use the small, sealed enclosure to replace this suspension force. It turned out that the air spring was more linear than that of the drivers, and in fact lowered distortion. This has been confirmed many times. The catch is that above some amount of % compression, the air spring became progressively less linear. Distortion generally starts to climb quickly as you pass 5-10% volume compression. In other words, the amount of air displaced by the driver is 5-10% of the total box volume.

In quantifying where a box becomes "acoustic suspension" the math shows that at around 1/3rd the driver's Vas, the restoring force is largely dominated by the air spring, and not the spider or surround of the driver. A classic definition of an acoustic suspension speaker is thus a speaker in a sealed box less than 1/3rd it's Vas. Many texts then refer to sealed boxes with greater volumes as infinite baffle designs. This older useage of the term in combination with the common useage I mentioned earlier sets up the confusion.

Really, they're all sealed boxes. The ratio of the Vas and enclosure volume determine how significant the air spring is in the system. Many claim there is a worthwhile difference when you get the enclosure volume past 10x the Vas. Personally I'm pretty confident that it's just the resulting frequency response that people like, especially when put in typical listening rooms. So long as you are not over compressing the air to the point of distortion, I doubt the frequency response and resulting low frequency sensitivity is what you should really focus on.

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post #369 of 682 Old 03-23-2008, 07:44 PM
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Originally Posted by penngray View Post

I care about finish and size. Meaning two subs side by side, If one performs better but its HUGE and UGLY. I will take the other one if the performance is still great but not as great. Too me having the BEST performance overall isnt great if its sticks out like a sore thumb in the room.

Are your saying in a roundabout way that you don't DIY because you can't or won't finish a cabinet to a high standard?

DIY doesn't have to be ugly. Its a golden opportunity to be creative and build something unique. Like yourself I don't suffer an ugly box or even just a well built pretty box. DIY, for some, can be very cool in this respect.
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post #370 of 682 Old 03-23-2008, 07:50 PM
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Originally Posted by Thomas View Post

Looks like the SLLT plays a lot louder right? Not mentioned is the fact that the IB measurements were taken with 750 watts powering the IB, while 2400 watts were powering the LLT.

Man, you love to distort the truth. During the comparison phase, at which point he had two RL-p15 drivers on one side of his room in IB form and two RL-p15s on the other side of his room in SLLT form, they were both equally powered. This is when he did his first round of comparisons. During the second round - the round in which people proposed movies and music for him to test with both systems hooked up, he had two amps, one for each set of drivers. He preferred the SLLT in BOTH situations, but that's not even what this discussion is about. And actually, now that I think about it, I'm pretty sure he didn't use two amps for the two IBs because he could already drive them to bottoming with just one, and he wasn't liking the results. Additionally, he has since gone back to one amp because one amp with the two SLLTs is more than he can handle.

It's one thing to debate with good arguments Thomas, it's another to distort the truth to try and make it seem like you have a point. That's extremely weak Maybe that's why you aren't welcome there anymore.

Quote:


(note Rodney can't use a higher XO point, since he has a major problem with port resonances and no one posting on HTS has a clue how to tame them).

You got that from this?
Quote:
Originally Posted by Rodny View Post

when I was inside of the box and you talk or scream can here a weird noise with a little echo, I think is the PVC pipe, change the crossover to 60Hz and it goes away!, I'm going to try Dynamat on the port to see if it kills the resonance, anybody with the same problem ??

The enclosure wasn't lined with anything and he opted for pretty long ports. I love how you interpret that as major problems


Let's see if you pull a Craig now and try to get this thread locked/deleted to cover that up.
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post #371 of 682 Old 03-23-2008, 08:04 PM
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Steve,

Thanks for the post with the quote,Mark has very interesting things to say. And this will be looked at when I model my sealed.




Shinobi,

Agreed again, DIY done right can be stunning,your creations are a testament to this. And best some of the finest production units.

I do not go as far but make sure my DIY looks good(yea that huge red box looks at me with an evil 18" eye! Still,DIY can look amazing,with tools,time and work DIY has nothing to hide.

Ask yourself mortal , do you have as much displacement as me ? The answer is no unless you have a Windmere fan sub.
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post #372 of 682 Old 03-23-2008, 08:26 PM
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Man, you love to distort the truth. During the comparison phase, at which point he had two RL-p15 drivers on one side of his room in IB form and two RL-p15s on the other side of his room in SLLT form, they were both equally powered. This is when he did his first round of comparisons.

The graph attached is from the first round you refer to. When I overlaid the response graphs to level match them, the truth became evident, as it matches what one would expect to see in such a comparison.

The ported version has a 6dB advantage at tune, but the sealed has a 12dB an octave below that.

No info was given as to the distance from the mic, the position of the mic, the accuracy of the mic and interface, etc., but a helluva lotta subjectives were being slung around in that thread with no regard to a consensus from less biased listeners, etc.

Really Steve, for the truckloads of grief you gave Craig, who did a much better job gathering subjective data than this Rodney guy came close to, you ate up Rodney's subjectives like a mule at feeding time.

Quote:


As for the doubting of air spring distortion, it comes directly from Linkwitz, the guy who seems to be everyone's hero. The smaller the box and greater the displacement of the driver, the greater the air spring distortion. You can find it in his "closed box" spreadsheet here - he uses the equation: air spring distortion = 0.014*(Sd*Xmax) / enclosure volume.

Hah. I had a feeling you had just gotten your education on 'air spring distortion' today from your usual one-sided gloss over of the information. It's good to see that you've come back with your source and explained that there is a formula (which those of us who are better versed in the sealed alignment already know) involved, but it's a shame someone always has to call you on this tactic to get to the whole story.

Saying a small sealed box causes air spring distortion is like saying porting a subwoofer causes a tuning above 30Hz.

Using box volume to provide a stiffer suspension reduces non linear distortions, protects the driver from over excursion and raises a low Q driver to the desired anechoic system Q. In a push pull configuration, distortion is reduced even further.

BTW, write Sig and ask him which of the two alignments he prefers, and why. His response will be short and sweet.

Bosso
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post #373 of 682 Old 03-23-2008, 08:28 PM
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Sorry, the graph...
LL
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post #374 of 682 Old 03-23-2008, 08:35 PM
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Quote:
Originally Posted by SteveCallas View Post

During the comparison phase, at which point he had two RL-p15 drivers on one side of his room in IB form and two RL-p15s on the other side of his room in SLLT form, they were both equally powered.

Oops your bad...

Here's the quote (post #99) from Rodney regarding the plot below because he can't understand what's going on...

Quote:


Finished my other SLLT, well not really I still need to build the front panels, the flare on the out side is going to be 1" 1/4 and the inside is 3/4, is this OK, or I need to do the inside like the out side ??
I've check all the settings on the REQ and the receiver, because it didn't look right, I said to my self this cant be right, is to much gain but after checking all the settings couldn't find any thing different , so this is what it looks like ..................

Two SLLTs purple and the two IBs green



Two posts later (post #101) Rodney clarifies how the subs are powered

Quote:


Just want to mention couple of things.........

The SLLTs has two EP 2500s bridge to 4 ohm load( one on two subs).

The IBs had one EP 2500 running 4 ohm stereo.

You don't have a clue what a port resonance is. Here's a hint it's NOT the port material itself resonating, although you think it is.....

Quote:
Originally Posted by Steve Callas View Post

Hmm, cardboard sonotube is a naturally more damped material than pvc, I'm thinking that would play a role. To fix the issue with the pvc though, I'm thinking you would want to add more mass to the port. Strips of cloth dipped in plaster of paris and then warpped around the port perhaps?

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post #375 of 682 Old 03-23-2008, 09:24 PM
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Thomas, you continue to distort. Every time he compared the IB to SLLT in his room, he compared them both set up at the same time and they had equal power. He preferred the SLLT under these circumstances. The SLLTs were powered by two amps only after the comparisons were done and he converted both IBs to SLLTs, as the SLLTs could actually handle two amps whereas he was getting some bottoming with two IBs with just one amp if I am not mistaken. A FR sweep of the SLLTs would have been unaffected by more power unless the single amp was straining in the first place - it was not. The FR you are posting is measured at his seat when both SLLTs were complete compared to both IBs measured at his seat. After converting both to SLLTs, it is insignificant how many amps he used, as he already gave both a fair shot with equal power.

If you are taking issue with the general ~13db increase between the two graphs, I wouldn't put a whole lot of significance in it - yes, he gains headroom and low end efficiency with porting, but that 13db difference in general levels is probably some type of level setting error. I don't think anyone is looking at that and thinking he gained 13db free headroom at all frequencies. The free, clean headroom he picked up starts to take shape ~25hz and lasts until ~6hz.

Post #55 shows a direct FR comparison between the IB (before) on one side of the room he replaced with a SLLT - he gained a hell of a lot of low end - equal power to both. After replacing the second IB, he got an extra boost centered ~11hz. After addingthe large flares, this boost gets centered ~10hz, as overall port length increased.

You think this infrasonic performance increase is insignificant - then on the other hand we have bosso who is obsessed with <5hz performance. You can't win against you two guys. The fact of the matter is that he gained a large amount of clean low end - his FR linearity improved, keeping him solid to below 10hz, whereas he used to tank below 18hz. His distortion in the ~7-30hz range decreased by a fair amount. No, he doesn't have any measurements of this (ssabripo), but it's common sense if you understand how porting works. Lastly, he can play at overall higher levels with a single amp, as bottoming won't prevent him from having to turn it down. Big improvements, fairly easy project.

Quote:
Originally Posted by bosso View Post

Saying a small sealed box causes air spring distortion is like saying porting a subwoofer causes a tuning above 30Hz.

Using box volume to provide a stiffer suspension reduces non linear distortions, protects the driver from over excursion and raises a low Q driver to the desired anechoic system Q. In a push pull configuration, distortion is reduced even further.

Did you actually refute anything regarding air spring distortion in what you just wrote? Even Mark mentions in that post of his I quoted earlier that after some point of air compression in an enclosure, generally 5-10%, the air spring becomes less linear.
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post #376 of 682 Old 03-23-2008, 10:10 PM - Thread Starter
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Are your saying in a roundabout way that you don't DIY because you can't or won't finish a cabinet to a high standard?

DIY doesn't have to be ugly. Its a golden opportunity to be creative and build something unique. Like yourself I don't suffer an ugly box or even just a well built pretty box. DIY, for some, can be very cool in this respect.


No doubt some can do a great job with the finish, I have seen your designs and pics. The finish is great, not a fan of the design at all but you like them and that is all that matters.

Having such a great finish takes lots of time and for me at some point time becomes money again so if DIY takes too long its not worth it to me.

DIY is something different to everybody, I DIY lots of things so its just not about a sub. For me DIYing is about getting the best price/performance out of anything and learning something along the way but I once its done I move on. Once I build my last 2 subs, I wont build again because Im not a tweaker with things. Well, if I build another house then I will build IBs into again.

Because IBs rule and Steve Callas is usually wrong!

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post #377 of 682 Old 03-23-2008, 10:16 PM - Thread Starter
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Maybe DIY isn't for you then, I dunno. Most other DIY owners tend to like working on such things. That's why you constantly see them working on one thing or another, even if they don't need it.

DIY is simply DO IT YOURSELF.

Everyone has a specific reason to do it. I dont believe in tinkering if I dont need something and I dont believe in building something that looks like crap either. We all do it for different reasons, its all our own reasons too so when I talk about value of something Im not just looking at the pure numbers, Im also looking at the esthetic value.

Simply put you can have your big ugly boxes or silos because they work for you, they dont for me or anyone I hang around with.

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post #378 of 682 Old 03-23-2008, 10:54 PM
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Originally Posted by SteveCallas View Post

whereas he was getting some bottoming with two IBs with just one amp if I am not mistaken.

Yep you're mistaken....again. Apparently everyone but you knows the RL-p15's are an inherently bottomless design. So driving a pair of RL-p15"s off one channel of a EP-2500 Rodney was hearing his amp clipping not bottoming.
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If you are taking issue with the general ~13db increase between the two graphs, I wouldn't put a whole lot of significance in it...... but that 13db difference in general levels is probably some type of level setting error. I don't think anyone is looking at that and thinking he gained 13db free headroom at all frequencies.

Didn't see any qualifiers posted by you regarding this....As a matter of fact you seemed to put a lot of significance to it. Here's your quote from post #100 before Rodney clarified the amp situation...
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Originally Posted by Steve Callas View Post

That is one heck of a natural low end response my friend - very, very nice......Remember, with great power comes great responsibility - your truly have a monster on your hands now

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Originally Posted by Steve Callas View Post

Post #55 shows a direct FR comparison between the IB (before) on one side of the room he replaced with a SLLT - he gained a hell of a lot of low end - equal power to both.

There are readily identifiable reasons for the differences seen in post #55 and they aren't all related to porting, but I'll save that discussion for another day....
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You think this infrasonic performance increase is insignificant - then on the other hand we have bosso who is obsessed with

Don't play games by trying to bring a discussion you're having with Bosso into the one your having with me.
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Big improvements, fairly easy project.

I'm sure Rodney would dispute the "fairly easy project" opinion, and no one believes the "big improvement" nonsense...

BTW, I want to thank you for this classic statement about Rodney's project, I fall out laughing every time I read it......
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Originally Posted by Steve Callas View Post

So the additional low end headroom and power Rodny will gain isn't something to take lightly, it's roughly the equivalent of adding 10-12 more RLp-15s in that range around the tuning frequency.

Oh and I need to ask again, have you figured out what a port resonance is, or do you need a few more hints?
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Originally Posted by SteveCallas View Post

You don't gain any deeper bass extension, only greater low end efficiency. A driver can only move so much air - the difference between an IB and a small sealed is how much power it takes to move the cone a certain distance.

The spring prevents the cone from moving which restricts it's deep bass extension. In an IB, the cone can move further to reproduce lower frequencies with less input power.

Quote:


Yikes. That restoring force you talk about is actually a form of distortion known as air spring distortion.

Your definition of "distortion" must be special then. The air spring damps the cone below resonance in a sealed box. This prevents over-excursion. Ported has no such air spring. The cone moves further without protective aid and the coil former will hit the back plate sooner.

Quote:


As to your second comment, the driver will not "run out of usable excursion sooner", as the excursion of the driver is fixed - at a given output level, the IB will produce slightly less distortion than a smallish sealed box (assuming it is well built) because less power is needed to achieve the same amount of cone travel.

You are very wrong. A box has a given amount of air inside that can be pressurized. It will take a given amount of force in a given period of time to pressurize that box. Larger the box the more difficult to pressurize given the amount of force per unit of time.

Pressurize a box and there will be a force imparted on to the cone. Resistance to motional force is greater in a small sealed box because the air resistance is higher.

Smaller enclosures will restrict cone excursion because, likewise, the air acts like a resistive load that prevents the cone from moving freely. This spring weakens as box size increases. Because the spring weakens, the cone can move further and it can then produce lower frequencies.

Now increase the box size even more and the cone can move even further with that same force. The cone will move further because the speakers own mechanical suspension is the dominating factor. Make the box infinite in size (to make the spring effect insignificant) and the cone is operating in free-air.

The cone will move further with less resistance and because of this can bottom out sooner than in a small sealed enclosure. Excursion will run out sooner because there is no protection; there is no air spring to control and protect the cones ability to move. The compliance of air has now taken a backseat and the cones mechanical suspension takes center seat.

The excursion is fixed. But it will be used up sooner (with the same force), distortion will rise. Less power is required in an IB because the system is far more efficient. The byproduct is very low thermal compression. Thermal compression is important but usable excursion is also important and it will be used up sooner for the reasons stated.

Why do you think more drivers are required in an IB than in a regular sealed box ? Put a single 15" cone (with moderate Xmax ability) in an IB and you'll understand that displacement is far more important in an IB than in any other alignment.

This also means that you, potentially, have the ability to out-displace any other alignment using multiple large high excursion drivers, very high Vd and very low power compression.

--Regards,
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post #380 of 682 Old 03-24-2008, 02:49 AM
 
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Goneten was wrong on just about everything he said.

Please cite all examples. Argumentation by assertion is not an argument.

--Regards,
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post #381 of 682 Old 03-24-2008, 03:06 AM
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Myslelf versus Commercial entities

i like me. i am capable of trying new things, and going 'all out' on experiencing things that the average joe wouldn't imagine.

a company that has a valid recipe for a speaker/subwoofer is pretty cool. If I want to buy that company's product, I am more than welcome to.

However, buying from a comercial vendor won't supply me with the excitment and pride that building a diy would provide.

It basically boils down to time, money, and performance. Buy some sick a$$ comercial speaks if you don't want to get your fingernails dirty. But if you want the same output and quality ( and have want to spend your spare time) then look into a d.i.y. design. not only for a sub, but also for your speaks.
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post #382 of 682 Old 03-24-2008, 03:13 AM
 
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Originally Posted by SteveCallas View Post

That porting creates lower distortion, more low end output, greater FR linearity, etc.? It's already been proven.

Distortion is only lower at and around Fb. Otherwise distortion levels should be similar if not identical, all things being equal. Below Fb, distortion will rise significantly. You still have thermal issues to deal with, port resonances, over-excursion below tuning, etcetc.

--Regards,
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post #383 of 682 Old 03-24-2008, 05:28 AM
 
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Originally Posted by SteveCallas View Post

Goneten was wrong on just about everything he said

I don't think you have any authority to make any declarative statements on this subject, quite frankly. Just because you've built a few subwoofers does not in any way mean that you understand how they work.

I like to stick to the physics, Steve, hence my usually long-winded posts on the subject so that I can make it painfully easy for people like you to understand. I also don't have an agenda here, unlike some.

For the record, I love ported design. Most of the subwoofers I've built have been ported, I've only ever built two IB's, one using four AV-15 Stryke drivers, the second using old Adire Tempests.

I've just ordered dual MFW-15's. However, no subwoofer I have ever heard has come close to the IB's I've built. The sense of scale, more importantly, the sense of weight is conveyed with an IB that no other alignment I've heard has come close to.

I attribute this to not only the very high Vd levels available and almost nonexistent power compression, but the absence of an air spring. I mentioned that there is no box coloration. Well, there isn't. There is an effortless quality to an infinite baffle that is difficult, at first, to pin-point.

I believe the absence of an air spring is one of the dominating factors, besides the numerous other benefits.

--Regards,
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post #384 of 682 Old 03-24-2008, 05:31 AM
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Alright. Good points made all around...though I don't know why this is still a debate?

-A port will always help increase output at and above it's tuning freq.
-A lack of port will always help an IB in the deepest of frequencies.

Also, why discuss how IB works, air spring effect, IMD, THD, single digit extension, and SPL?

Because there are so many variables, no one alignment will be the best at all of them. It's a give and take as everyone's mentioned and what's important to one, is not necessarily important to someone else. For me, ported is the winner as it better fits my needs, though once I own a house, IB it will be due to the stealth factor.

Bosso's right. His needs dictate single digit output is important and he's acheived that while still maintaning mobility of his subs.

Steve's right. EBS helps output in the ~13-80hz area (8+ for sLLT)

ThomasW's right. Cheap drivers can be had for IB and it will always play lower, louder than even an sLLT. Granted that may be down in the low single digits but it will ultimatly play deeper than any sLLT design.

Is there anything left to debate?

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Originally Posted by Steve View Post

You don't gain any deeper bass extension, only greater low end efficiency

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Originally Posted by goneten View Post

In an IB, the cone can move further to reproduce lower frequencies with less input power.

Yeah, that's low end efficiency.

YID DIY
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post #385 of 682 Old 03-24-2008, 05:46 AM
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Originally Posted by Looneybomber View Post

Alright. Good points made all around...though I don't know why this is still a debate?

-A port will always help increase output at and above it's tuning freq.
-A lack of port will always help an IB in the deepest of frequencies.

Also, why discuss how IB works, air spring effect, IMD, THD, single digit extension, and SPL?

Because there are so many variables, no one alignment will be the best at all of them. It's a give and take as everyone's mentioned and what's important to one, is not necessarily important to someone else. For me, ported is the winner as it better fits my needs, though once I own a house, IB it will be due to the stealth factor.

Bosso's right. His needs dictate single digit output is important and he's acheived that while still maintaning mobility of his subs.

Steve's right. EBS helps output in the ~13-80hz area (8+ for sLLT)

ThomasW's right. Cheap drivers can be had for IB and it will always play lower, louder than even an sLLT. Granted that may be down in the low single digits but it will ultimatly play deeper than any sLLT design.

Is there anything left to debate?




Yeah, that's low end efficiency.

You're not trying to sum this up are you ? How 'bout I buy the next super-large bucket of popcorn and you get two large Cokes and we sit back and enjoy the show.

I miss out on the mobility thing with my subs.

KG
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post #386 of 682 Old 03-24-2008, 05:49 AM
 
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A byproduct of using less power (due to the absence of an air loading effect on the driver) also means that the cone can move further to a lower frequency. Steve is claiming that IB's don't give deeper bass extension which is simply flat out false.

--Regards,
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post #387 of 682 Old 03-24-2008, 05:59 AM
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Originally Posted by kgveteran View Post

You're not trying to sum this up are you ? How 'bout I buy the next super-large bucket of popcorn and you get two large Cokes and we sit back and enjoy the show.

I miss out on the mobility thing with my subs.

KG

You just need to hit the gym. They'll be mobile once again with some phamacology.

Well if you're buying the pop-corn... Let's add some fuel then.

Who's to say you can't use multiples of the same IB subwoofers in giant 3-400ft enclosures tuned to 6hz? You can utilize that rear wave and keep all the nasty distortions well outside the critical listening frequencies. That should also net a good advantage (SPL wise) over an equal IB installation to 4hz?

Or what about large horn loaded enclosures in the attic?

YID DIY
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post #388 of 682 Old 03-24-2008, 06:01 AM
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Originally Posted by SteveCallas View Post

Please epxplain how it is not - I see nothing in those posts that does. Goneten was wrong on just about everything he said. Thomas didn't say anything explaining how an IB is not essentially a large sealed enclosure. Do you yourself even know? Please spend 2 minutes and explain it.

Good lord!
a) re-read the replies, and reread the intro on HTS and the cult. I'm sure it will dawn on you sooner or later.
b) exactly where is Goneten wrong? could you please be more specific? with proof of course!


Quote:
Originally Posted by goneten View Post

I don't think you have any authority to make any declarative statements on this subject, quite frankly. Just because you've built a few subwoofers does not in any way mean that you understand how they work.

Correction: he's build a pair of LLT's only and that's about it, at least with someone to corroborate that he did.









finally, I've read the thread on Rodney's ventures several times, and I'm afraid there is no distorting there Steve. He did "like" ( a subjective decision btw, which you usually frown upon so hastly) the SLLT better, but came at the cost of the Port Resonance he didn't like....which is fine for me, I don't see a big deal with that.
link

Lost in all your usual denial is this simple fact: Rodney used 4 RL-P15's, which work fine in both ported and sealed alignments. Cost of each: ~$300!!! Now, if he were to use 4 fi IB15's at a cost of $100/ea, he could either save nearly 3/4ths of the price ($400 vs $1200), or could have bought 8 IB15's for $100 and STILL come way ahead in terms of performance.

why do I bring that up? You know very well that the reason for IB drivers being cheaper is that they do NOT require the motor strength to perform, and therefore have usually a somewhat weak topology. Now, you continue to preach adding a port to an IB and turn it into an SLLT for "added performance"...............how do you think typical IB drivers will react now in a ported alignment at full strength given their motor topology???

so you see, it again goes to basics: if you want an SLLT, you need drivers capable of handling the mechanical limits due to the port, and you will pay accordingly................so back to square one we go: Performance on Dollar, what is best?
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post #389 of 682 Old 03-24-2008, 06:08 AM
 
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Hehe.

--Regards,
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post #390 of 682 Old 03-24-2008, 06:10 AM
 
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ssabripo, where the hell is the popcorn icon ?

--Regards,
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