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What should we be testing next? How should we be testing it?

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We want to know what gear you want to see put under the microscope, whether it be a powered subwoofer for home theater, a big pro sound bass bin or a raw car audio driver. I can't promise that we will get to everything or even half of it but as we eventually work through the current back log of tests we will have to acquire new stuff. There might be something that is particularly popular among a certain crowd or that is really intriguing due to technology claims or plain old hype.

 

Personally I am eventually going to do one of those 8th order band pass Bose bass module for fun.

 

Tell us what you want to see on the bench.

 

On the other side of the coin if you have ideas for a new measurement that could tell us something that the current ones don't don't hesitate to suggest it. We welcome ideas on ways to improve our measurements, procedures or whatever. Got ideas for the site or content bring those on too!

 

We will be adding a dedicated discussion thread for each system and driver that has been evaluated so that they may be discussed and some other random thoughts may be added.

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I believe that we are looking into adding that calculation to the parameters. Although that assumes that the xmax spec from the manufacturer is an accurate indicator of useful displacement from a driver. Some over achieve and some greatly under achieve in that area.

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I think we really want to collect the coil vs gap dims. This won't render a curve... a curve is really the true indicator of BL performance, but we can at least speculate a bit more if we know the physical dims. Unfortunately someone has to either decone their driver or we need to get the mfr to cough up the numbers.

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Some drivers I would like to see on the bench:

 

Aurasound NS18-992-4A

AE AV15H, X

AE TD18H+

 

BMS 18N862

BMS 15N850v2

Faitalpro 18XL1600

Faitalpro 15XL1400

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I'd definitely like to see the AE AV15 and TD18 measured but they seem to be pretty hard to get currently. Especially the AV series. The Aurasound NS18 would be sweet too and I think they just got back in stock. I'm pretty tired of most of the Fi stuff cuz they seem to be more of the same from each other. However, I would like to see the SP418 measured. That one seems cool.

 

I'm still interested in sending over some of the lower priced drivers such as: Dayton DVC15 and RSS380hf. Those are pretty popular and it would be interesting to see them measured up against the competition.

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I'd like to see some numbers on Nathan Funk's new underhung 18. Maybe he can be convinced to send one your way?

 

Also, a JBL W15GTi would be cool. (Alas, I don't have the box for mine, and I'm afraid of UPS-itis).

 

I'm less concerned about "knowing" xmax, honestly, and how it's derived, because xmax is only useful to make inferences about output capability, which is what you're measuring. If you have comparisons of ultimate output capability, that's better than excursion. But, one thing I think would be interesting is a comparison of several drivers with the same claimed (or even Klippel-measured) Vd. It doesn't really matter which ones: could be, say 12mm xmax 15's, 15mm xmax 12's, or 30mm xmax 18s, or 6mm xmax 8's.

 

I suspect that there will be a surprising variance in output capability from drivers one would expect to have ~ the same output.

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How about a set of DIY test guidelines?

I don't expect that I can do the entire suite you guys do, but I would like my tests to be at least somewhat correlative to yours.

 

I do have calibrated equipment now, but it is still most certainly DIY-level.

 

Only reason I ask is that I have a few builds on deck, and a couple test days coming up.

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I'd like to see some numbers on Nathan Funk's new underhung 18. Maybe he can be convinced to send one your way?

 

Also, a JBL W15GTi would be cool. (Alas, I don't have the box for mine, and I'm afraid of UPS-itis).

 

I'm less concerned about "knowing" xmax, honestly, and how it's derived, because xmax is only useful to make inferences about output capability, which is what you're measuring. If you have comparisons of ultimate output capability, that's better than excursion. But, one thing I think would be interesting is a comparison of several drivers with the same claimed (or even Klippel-measured) Vd. It doesn't really matter which ones: could be, say 12mm xmax 15's, 15mm xmax 12's, or 30mm xmax 18s, or 6mm xmax 8's.

 

I suspect that there will be a surprising variance in output capability from drivers one would expect to have ~ the same output.

 

Good points.

 

One thing we're trying to collect is the gap and coil length. This won't alone tell us the BL curves or much less symmetric issues etc, but we can speculate curves and maybe even do calculated predictions without real world FEA B fields.

 

For example, a tall gap overhung will have a more gradual slope that is not very flat for very long. Where a very short gap w/ a long overhung coil will be flatter and then fall off more quickly past xmax. Underhung will have more constant B in the gap and then fall off outside based on the same gap vs coil ratio properties of the overhung... etc etc. We could FEA like 10 basic shapes and just interpolate between them to come up with BL curve predictions based off very raw numbers like the gap/coil.

 

That's all down the road. Right now we're focusing on more large-data-set entry and generating live SPL curves rather than having static images like we do now.

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Thanks for the replies...

 

There are a bunch of tests and more drivers in the works...I am in on the AE group buy for some TD15M's and TD18H+'s All with the Apollo upgrade so those tests are just a matter of time. Probably later rather than sooner though. After I finish up some of the current stuff the W15Gti is on my short list. I want to get an Alpine Type R too.

 

To some extent I agree with DS-21 here. The xmax figure is good for modeling but if you have actual test data that shows that a driver gets really mechanically noisy, distorts like mad or runs out of headroom at a certain point in testing that obviously trumps the xmax figure. Still it does help to be able to model things. The big issue that I am wrangling with lately is in fact accurate modeling and how to go about it. Complex inductance related effects have to be involved but even an LE,L2,R2 model can be off sometimes. Simply model an Ultra 5400 in a sealed box with the inductance then compare to the real measurement and you will see what I mean. You also have the rated xmax versus actual useful excursion issue. Yet another issue recently mentioned to me by Deon B. is over inflated SD specifications. Some drivers have a rated SD much larger than another but when physically comparing both the advantage is actually the other way around. Obviously that is not right. we will now be measuring SD for all of the drivers which will include 1/3rd of the surround. The measured spec might not be accurate to the final square cm but at least it will be relative between the drivers on Data-Bass.

 

LilMike,

We are hoping to eventually get some other contributors so yeah... I guess I could put together a post about it. Truthfully you don't need a bunch of expensive equipment for most of this. All of the software that I am using is either free or very cost effective such as REW or ARTA. The exception is CEA-2010 which does require an investment (Unfortunately that seems to be the test everyone wants to do). Budget gear like an EP amp, one of the <$100 calibrated mics, free software and a SPL calibrator can cover 80% of it really.

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LilMike,

We are hoping to eventually get some other contributors so yeah... I guess I could put together a post about it. Truthfully you don't need a bunch of expensive equipment for most of this. All of the software that I am using is either free or very cost effective such as REW or ARTA. The exception is CEA-2010 which does require an investment (Unfortunately that seems to be the test everyone wants to do). Budget gear like an EP amp, one of the <$100 calibrated mics, free software and a SPL calibrator can cover 80% of it really.

 

Cool. I have a decent calibrated mic, an EP2500, and I can get my hands on a calibrated meter without too much trouble.

 

Just have a couple measurement days coming up in the next week, and want to do measurements that will be useful for comparisons.

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Cool. I have a decent calibrated mic, an EP2500, and I can get my hands on a calibrated meter without too much trouble.

 

Not a calibrated meter. An SPL calibrator would be a much better buy. An ND9 is decent and about $110. If you don't have an SPL meter I have a Galaxy CM-140 that I do not use anymore

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Not a calibrated meter. An SPL calibrator would be a much better buy. An ND9 is decent and about $110. If you don't have an SPL meter I have a Galaxy CM-140 that I do not use anymore

 

Well, round one of those measurements has been cancelled. My most recent build (pic in my avatar is also plywood) was full of fail. Trying to sort it out today. Hope I can find some answers.

 

I can borrow the calibrated SPL meter from work. I just use the calibrated meter to cross-check mine. I verify that one (internal cal), then fire up a mid in a baffle and set a 1 KHz tone to 94 dB, then check my meter with the mic at the same location. Also have an OmniMic now, but I am still learning how to use it as well as get meaningful information out of that software. Prefer REW for bass measurements, mainly cause I am familiar with it.

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Well, round one of those measurements has been cancelled. My most recent build (pic in my avatar is also plywood) was full of fail. Trying to sort it out today. Hope I can find some answers.

 

I can borrow the calibrated SPL meter from work. I just use the calibrated meter to cross-check mine. I verify that one (internal cal), then fire up a mid in a baffle and set a 1 KHz tone to 94 dB, then check my meter with the mic at the same location. Also have an OmniMic now, but I am still learning how to use it as well as get meaningful information out of that software. Prefer REW for bass measurements, mainly cause I am familiar with it.

 

What happened? Something did not turn out as expected I take it? I feel your pain man, I've been there many times.

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What happened? Something did not turn out as expected I take it? I feel your pain man, I've been there many times.

 

You've got mail

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Fantastic site!!!

 

I would love to see an updated test of a sealed lms 5400 ultra 18" (close to building one), eventually one of the popular PR versions with two 18" vmp's.

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I'd be interested in you putting the JBL W15GTI Mk.II,... just very curious about it's magnetic design's actual performance. JBL/Harman performs so much R&D, this is their subwoofer tour de force, so it's only logical it should be explored by a third party to determine if their pro transducer technologies translate to a full tilt enthusiast HT subwoofer application. No better third party than Data-Bass B)

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After reading a bit of yet another "which is better, sealed or ported?" thread at AVS I decided to suggest the onset of a database of component frequency responses.

 

The point I didn't want to waste posting in the AVS thread is that there never has as of yet been a true 'sealed vs ported' listening session, so the question just cannot be answered by citing commercial subs and the slew of cliches that are always brought up in these debates.

 

Several ID companies have offered the statement of performance that goes something like "Our sealed subs have a true 2nd order roll off" Implying "no HPF". This is, of course, a patently false statement without the qualifier of stating a bottom frequency.

 

All EQ circuits and amplifiers have blocking caps to prevent DC offset. The values of those caps determine the F3 and order of roll off, which would be additive to the sealed subs 2nd order roll off.

 

When you include the typical DVD/BR player and AVRs analog SW output roll offs as well as any external PEQ post smoothing hardware, you begin to quickly realize that the sealed sub that is supposedly an unadulterated 2nd order sub is really down -30dB at 5 Hz (or 8 Hz or 10 Hz or 16 Hz or 20 Hz) with a virtual brick wall roll off below 10 Hz.

 

To illustrate, the Epik Empire and the JL Audio are sealed subs and the PB Ultra-13 in 10 Hz tune is a ported sub. FR and roll off are everything and, in this case, ported or sealed is irrelevant.

 

The typical AVR is a Marantz, Denon, Yammy or Onk and there is also a fairly short list of typical players. The miniDSP, Berry, SMS-1, etc., also represents a fairly short list of EQ devices.

 

If we had those loopback graphs, it would be simple to accurately calculate any combination of those FRs to predict the signal chain roll off.

 

The amplifier is a bit more difficult, but not impossible to nail down as well.

 

There is no doubt in my mind that the whole "most guessed wrong at sealed or ported at the blind listening G2G" is the result of much more similar FR and GD than a WinISD model predicts.

 

For some devices (like my external sound card/interface) you want to measure the digital output vs the analog output because they are almost invariably different and the sound card is connected digitally, not by analog out. So, the typical loopback measurement and subsequent correction file may be skewing the results.

 

To measure a players FR we burned a perfectly flat sine sweep to disc. Many players are connected via HDMI and/or digital coax (and no longer even have an analog out), so the sweep should be taken from a reference AVRs SW out and the AVRs roll off subtracted.

 

I still enjoy SACD multi-channel music, so I measured both the digital out of the BR and the analog out of the OPPO SACD player.

 

Since I'm a firm believer in my in-room tests of comparing the direct feed SpecLab of a scene to the mic'd at the LP version of the same scene, I wanted to explore the roll off differences in the signal chain in both cases, since the graphs go to DC and they're directly compared for evaluation of in-room sub performance.

 

Player===>AVR===>Sound Card (no correction file)===>SpecLab

vs

Player===>AVR===>EQ===>Amplifier/Sub===>Mic (correction file)===>Sound card (correction file)===>SpecLab.

 

The results were very interesting and it led me to think that a database of hardware roll offs would be a pretty important part of evaluations of many a posted so-called in-room FR and "this sub is [ ] than that sub because blah, blah, sealed vs ported".

 

Just a thought. I've done every combination of my own system (otherwise, I would not have had the impetus to extend the response as I have), so it's no big to me, but it's irksome this far into HT technology to hear people praise or condemn an alignment based on a FR that in no way resembles the alignment they're praising or condemning. Having the signal chain chart to quickly predict your systems roll off would be awesome. I'm sure we could put together a simple calc program that showed the resultant anechoic FR by simply clicking on the components in your rack and your sub.

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Hey Dave...Good to see you.

 

There are some good points in there especially about the effect of the electronics signal chain on the ultimate shape and effective limit of the bottom end. In my personal experience it takes a decent amount of homework to identify equipment that can provide a response without attenuation to even 10Hz let alone an octave lower. I have a bunch of electronics measurements from just these sorts of investigations. It would be helpful to have a catalog of saved measurements from various electronic devices commonly used by DIYers in their bass endeavors. As you mention it can be difficult to get accurate measurements though as depending on the type of signal and connections used in can affect the measurement.

 

Are you planning to set-up a blind, sealed versus reflex comparison (Subjectiveness of ULF present vs not)? I thought I recalled that you posted about maybe having a GTG at some point. That would be a very interesting if you were.

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I would like to see the 15" drivers tested in a bigger box. While it's fun to see what they do in an extremely small box I don't think anyone will every use one in a box that small in a home environment.

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I agree with this. I'd like to see drivers tested in enclosures people would use them in. Personally, I'd like to see 15" drivers tested in 5 cubic feet (or larger) ported enclosures.

 

As far as drivers to test...I'm interested in the Alpine SWR-1522D. I just bought one for my car, and I plan to put it into a 4.5 cubic foot ported enclosure. Not sure if I should port it to the computer program's suggested 21Hz or something else like 27Hz. Driver parameters are Qts 0.41, Fs 22Hz, Vas 100L. Anyway, I'd be curious how it would measure quantitatively and subjectively. The 20.7mm Xmax, 70mm peak-to-peak, and $199 price tag are what drew me plus the fact that Alpine won 2nd place in this comparison.

 

http://car-subwoofer...tenreviews.com/

 

Which leads me to mention that since the magazine Car Audio and Electronics has disappeared, there aren't many doing subwoofer comparisons anymore. When I was looking for a sub, I could hardly decide between JL Audio, Sundown and Alpine. In the end I picked the Alpine because of its T/S parameters (and 2nd place scoring in the comparison above). Not many 15" drivers play flat to 20Hz in a 4 cubic foot ported enclosure. I almost went with Sundown but I don't know anything about their sound quality. Everyone on the net seemed to like Sundown. They even did a 6000 watt burp to a single SA-15 to achieve a 158.1 dB score! Can a sub like that be good for sound quality? I wish someone that knew could tell me =) I noticed that there is a Sundown SA-15 test here BUT it is in a 1.25 cu ft sealed enclosure! Who on earth would do that? =)

 

I hope I didn't make the wrong choice by going with Alpine.

 

BTW, I just discovered this website (data bass), and I like it a lot. Found it mentioned in a review for the Dayton HO 18 at Parts Express. I'm really looking forward to seeing the database grow =)

 

 

I would like to see the 15" drivers tested in a bigger box. While it's fun to see what they do in an extremely small box I don't think anyone will every use one in a box that small in a home environment.

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