Best value LLT

[avaserfi]

DS-21 wrote:

You and Andrew seem to spout this "perceptual research" line in every post, so how about this: would you be so kind as to direct me to a paper in a peer-reviewed scientific journal that addresses the audibility of inductance in subbass subsystems, be it facially or peripherally?

Given your weltanschauung, in the absence of such research how can you legitimately claim anything about the subject pro or con? After all, we are talking about a measurable phenomenon that is well-known to affect FR and transient response.

The reason for a constant reference towards credible research, both perceptual and non-perceptual, is due to the objective nature with which these studies are able to address various aspects of audio from audibility of various phenomenon to, with proper application, design of various speakers and room acoustics. Despite the rigor of properly conducted research it seems rare for the majority of the audio community (DIYers and professionals as well as those who are simply intending on purchasing audio gear) to gain a full understanding of such important subject matter if the goal is utmost accuracy in reproduction of live performances.

As previously mentioned there is a burden of proof found in science without which one cannot justifiably make any assumptions. Your anecdotes are a perfect example of such a case where, in your experience, high inductance drivers typically perform at a relatively lower level when compared to low inductance drivers. As I have said previously it is your prerogative to hold this belief, but as of now there is no evidence of it in any credible publication, of which I am aware, that would make this a sound generalization. Due to this I stand by my suggestion that you make this known when urging others to seek out low inductance drivers.

With regards to a specific article analyzing the benefits of certain inductance levels there is nothing that I am aware of which proceeds in this endeavor. This is due, in part to reasons as mentioned by Chris, but also for another reason. There have been studies that do compare listener preference to overall loudspeaker performance as it relates to measurement in controlled circumstances. Within these studies various characteristics of drivers can be deduced none of which are related to inductance for reasons stated above.

Hope this is civilized enough for you Jim. Also, do let me know what your thoughts are in regards to my previous suggestion of two smaller, higher tuned, units that would likely result in a overall superior response.

[WmAx]

WillyD wrote:

Thats not really true. Most of these drivers do have attenuation due to inductance within the relevant band. Even the SDX has 2dB by 80Hz, granted that is hardly significant. But take a driver like the TC-3000...it'll have much more attenuation by 80Hz.

And while the W7 may be higher inductance, lets look at how the FR of the F113 measured with the xover bypassed. Maybe .5dB of rolloff by 80Hz?

Folks used to argue in the past that the HSU subs were (or are) typically more 'musical' than SVS subs. I wonder why? Look at the FR in the relevant band. The SVS 20-39PC+ with the DB12.2. It is 3.5dB down from 50Hz to 80Hz, while the HSU Vtf-3 Mk3 is roughly 1dB down from 50Hz to 80Hz.

Fast forward to the much reknowned PB13. Its 'musicality' is highly praised, among other things. And what do you know, it and the LMS-5400 are two of the most recent (and only) drivers to have both high excursion/high-output and very excellent linear FR well through the relevant band and beyond.

I don't see how there isn't a connection there.

You point comes down to raw FR - which is easily calculated, and compensated in the xover point/rate used. Nothing more. Nothing less.

-Chris

[WillyD]

You point comes down to raw FR - which is easily calculated, and compensated in the xover point/rate used.

Easily calculated? What do you mean by this.

And at the typical 80Hz HT xover, it is not compensated for. One would have to drop the xover point quite low for it to have zero impact.

[cynical2]

avaserfi wrote:

Hope this is civilized enough for you Jim. Also, do let me know what your thoughts are in regards to my previous suggestion of two smaller, higher tuned, units that would likely result in a overall superior response.

Yep, this is civilized enough. Looks like a passionate debate, but still friendly. I just didn't want it to escalate into anything personal.

As far as the 2 driver solution recommended...as far as I can tell, it looked great (and like it would go beyond meeting my needs/expectations). I want to spend some time tonight modeling all of the different options and overlaying their response (if I can figure out how to do that). To be honest, when I look at any of the options mentioned, they all look to me (from the model, at least) like they will blow me away. But, I think I can more easily understand the differences by overlaying the plots.

One thing that I have to keep in mind is that I will not be able to use a particularly low x-over. I have some NHT L5's that I'm auditioning for the mains and center. I haven't decided yet if I'm keeping them, but even if I don't I'll likely use bookshelf speakers up front. So, either way, I'm probably going to want to x-over at 80Hz (and, possibly even higher).

[cynical2]

I'm trying to model the options listed in this thread, and can't come up with a reasonable port configuration for the IXL-18's...as I understand it, I want the port velocity < 17. I can't seem to get it below 22 or 23...and that's with 2 6" diameter 50" ports. Anyone else made it work with the 12.5cuft, 15Hz configuration? If so, would you be willing to attach your driver file, in case that's the issue?

[Jodean]

you have to limit your port to 36", the program should tell you this but it doesnt......i think the box is too small....see what it comes up with when you open that driver.....

[cynical2]

Jodean wrote:

you have to limit your port to 36", the program should tell you this but it doesnt......i think the box is too small....see what it comes up with when you open that driver.....

Well, the size box I was using was the one Mike P built...hopefully he can chime in.

I also modeled it as a member on another forum suggested...slightly larger box (14.2cuft) and lower (11.5Hz)...results in a 36" port that's 6" in diameter. For that configuration, a velocity of 17 is reached at about 15.5Hz, and the port velocity increases STEEPLY as the frequency goes down.

So...over what frequency range should I target port velocities < 17? Is it important throughout the frequency range, or only above some value (like 15Hz)? My apologies for the questions that everyone else probably already knows the answer to...

[Mike P.]

Mine are 12 cu.ft., 16 hz configuration. Ports are 3 - 4 inch diameter by 30 inch long. Each subs is powered by 360 watts, which is more then enough for me. Port speed is under 22 m/s at 15hz.

[Jodean]

Im just figuring out stuff myself so im just sharing what i learned.

My port velocity is 23 at 20 hz on the one i built. Thats probrably why i can hear it chuffing......but i have to put my head right next to it to hear it.

I havent yet heard or found info on port velocity so im awaiting someones reply as well.

[cynical2]

Mike P. wrote:

Mine are 12 cu.ft., 16 hz configuration. Ports are 3 - 4 inch diameter by 30 inch long. Each subs is powered by 360 watts, which is more then enough for me. Port speed is under 22 m/s at 15hz.

Thanks, Mike. That's what the difference is...I was using the full 800W rating for the signal. I guess in reality I shouldn't dwell on what the absolute worst case is...at 360W you're still in excess of 110dB (without room gain). And, I don't think I'd ever go that loud.

[Blaser]

Jim,

I have dual RL-P18 LLTs in my 1800 cu ft room. Don't be afraid to have a lot of headroom...It is alway a good thing, you might need it anytime.

[WmAx]

WillyD wrote:

Easily calculated? What do you mean by this.

You can easily calculate the attenuation at any given frequency with a simple mathematical model considering the impedance value at frequency vs. inductance value.

And at the typical 80Hz HT xover, it is not compensated for. One would have to drop the xover point quite low for it to have zero impact.

Just as when integrating ANY drivers, there is usually no perfect linear natural transfer function. You can use parametric band on the sub line level to compensate, shift the xover frequency of the sub slightly up, modify crossover Q, etc.. Of course, since you said 'HT xover', it should be known: I consider these HT xovers as typically found in HT receivers, largely useless if one wants to have ideal integration. A device such as a Behringer DCX2496 will allow virtually any integration desired with optimal results. And if you want to get picky: realize that the room effect on the subwoofer response will alter the transfer function far more than the inductance around a 80Hz crossover point will.

-Chris

[Jodean]

The sonosub works laying down.....but decreases output at listening position.....just seems to work better standing up. I dont have a meter to test.

Thats all i have.