Alrighty, this place needs a spruce of technical talk I reckon.

When I start searching for speakers, I take consideration in gazing over some of the specs. From there, Ill shortlist and research, then find prices, the try to audition. If I like 'em, Ill buy them.

What Im after is, what sort of specs (give examples of something thats 'good') do you look for, and why? And from that, what do you think the specs mean, and how they contribute to the overall package?

Ill start with Subbass. I look for an Fs less then 25Hz, Inductance (Le) less the 2mH, Faraday Shorting rings, and (hopefully) a linear Xmax greater then around 6mm. Accompanying the low Inductance though, it needs a high BL. Fs would give me a low-end monster, Le will give me an incredibly quick response, the Faraday rings obviously to eliminate eddy's in the coils and lower heat generation, and linear Xmax for low linear distortion. The high Bl is simply to ensure a strong motor structure.

For Example, the Audiotechnology Flexunits 15 E 102 25 10 (is an underhung motor too....woot!).

Now for Midbass. I look for a higher Qts then my subbass, (stiff suspension is always good), large BL (strong motor), long linear strokes (high % of Linear Xmax to Xmech) and a healthy Cone Area (greater then 200cm2). For me, because the midbass doesnt need to go really high, inductance isnt really as much of an issue. Having it really low will obviously help with transients, but from what Ive seen, most midbass has a naturally low inductance anyway. I just accept it as a given.

An example of what I'd consider a great Midbass. Legatia L8.

Obviously listening will take preference with any speaker purchase, but thats not what this thread is about. This is about YOUR understanding of the T/S specs (and graphs if you like), and how you think they will help your system. So, fire away.

top thread mathew,,,

maybe you could outline what a few of the other things are, and what you look for in say a mid and a tweeters??

very informative about the subbass though

One of the reason why I jumped on the JBL W15Gti, when one came up, they have all those things, an Fs of 25hz, an Independantly measured Le of 0.4 (very low for a sub), faraday rings, Linear xmax of 20mm + - , and a strong Bl, all these combine to make a sub that has fantastic controlled low end, with low distortion, great transient response, and will play reasonably high for a sub aswell.

Luke

can you get those gti's in oz??

is there an oz dist???

iv like themfor a while, they look crape hot...

do you know the street price by any chance???

Yeah any JBL dealer should be able to get you one, RRP goes from $1000 for the 10" through to $1300 for the 15" I believe, street price I imagine a couple hundred less.

Luke

continue the talk.........cors

I don't get too technical when I look,

For subs I keep to anything less than 16mm xmax, the longer it is the heavier duty things become and slower and less transient capable, this is fine if you only play below 40hz tho.

I look for a very low mms (cone mass), But a cone that is very stiff also, I look for firm suspension.

Low FS + long excursion to me can often mean nice and low, but lacks articulation, speed and accuracy, and more often than not wastes tremendous amounts of energy because these things acompany poor efficency.

High effeciency is sought after, The more effecient my speakers, the less load on my power system.
Which also allows me to run with A/B or A Class amps, rather than having to reach for dirty D Class amps to save energy.

I've been through about 12 different subwoofers in the past 3 years, trying to find the right combination
of output, versus small box, versus energy effeciency. By Far the worst sub I had was the Eclipse SW8000 10", This had 38mm xmax (1 way), a 16hz FS and a claimed power rating of 625W, (1900W max) it played really deep in a tiny box.. no probs, weighted a ton. and Consumed my 800W Amp like it was nothing, my system went from a nice 50-60Amp Peak (20 amp average draw) to 200Amp Peak and 100Amp average system, with NO increase in output, and a dramatic loss in sound quality, This sub actually needed 1900W! My little focal 27KX with 9mm of xmax, and a smaller cone area, and 300W power handling blew the eclipse out of the water in every way, with the exception possibly of depth. (lower frequency capability). The downside is the Focal is about $200 more expensive and not suited to thrashers.

it became quickly obvious to me, that while more Xmax on paper = more output, And possibly better low end capability, in real life this isn''t neccessarily the case. In a mobile environment, pushing more air from a smaller area is only for SPL, for the rest of the time I want speakers that supply me quality sound and decent levels, without breaking my cars alternator apart. I'm a strong believer in effecient speakers where power consumption needs to be kept at a minimum, without having to make a compromise on amplifier quality or having to go to complicated and large ported enclosures. But still lets me play it loud and hard.

Juls

Just to throw a spanner in the works..



You can play UP to FS rather than down to.



What can TS parameters really tell us?



There main purpose is for enclosure design.

I prefer a low Qts design to allow me to adjust the "Q" to my desired liking.

Most car audio driver use quite a high Qts for the allowance of most, and their lack of enclosure understanding.Large motors have high inductance and there roll off earlier, they can be ideal if you don't require the frequency bandwidth. The lowest ohms I would consider using is 16 ohm. Voice coil heat is a precursor to power compression.



I have yet to measure a driver that complied with the manufactures specifications.

(hence my reason for custom built drivers)I think the specifications should be the limiting set for drivers you consider for your application. They do guide you into appropriate selections. (A high Qts is unlikely to useful in a small enclosure for example)

so you saying that no sub uv tested met specs ablo???

interesting, but not shocking,,,

what would be your pick of subs and enclosure, non custom, garden variety sub???

and what are its specs??

Thats a fair call Juls, but also a heavy generalisation!! I mean, some of the quickest subwoofers on the market have fairly large Xmax (not Xmech, but the one way linear stroke). Transient speed is related to inductance after all.

And if you are crossing over at around 50Hz (or lower for the ultimate), then 'speed' and 'transparency' are less detectable in the sub, and more detectable in the midbass. Get a great midbass, and you're laughing.

See, that IS interesting. Never knew you could do that before... Sounds fairly logical when you think about it, but how many subs exist with good 15-50Hz Frequency response (to maintain levels with your two 8" midbasses per side ) that has an Fs greater then 50Hz??

True. But they DO have more then one use. They can very accurately tell you quite a bit about the performance characteristics, hence why Im asking!!

Why am I not surprised??

If you use something other then T/S specs to gauge appropriateness of a speaker Abmo, what is it? I HIGHLY doubt you sat down one day and listened to every speaker you could, and settled on the Arvus. They must've had something 'technical' that twigged your interest first....

What is it, and why?

Mine do, I can't comment about other manufacturers. Generally speaking, FS is cone mass (If you use a cone material with "internal dampening", then it must also reduce transient response) so you either increase the cone mass (doping) and lower the FS (allows for a smaller enclosure but suffers from an efficiency drop), or you use a larger cone diameter (higher mass) requiring a larger enclosure.



The other way is to use high FS and run the subs below the FS, this allows the "best of both worlds", small enclosure and high efficiency IF you can match the inductance accordingly. It does suffer from mechanical xmax limitations (IE idiots push them into over excursion).





Possibly..

To be honest (a first?? ) , major performance is dictated by linear BL (Or a matched suspension to a curved BL) cone angle, rigidity and decoupling (surround design) None of these are normally published.



I did interview a VERY large number of drivers, before settling for my choices. I no longer recommend drivers to people, simply because it is a matter of taste and expertise (enclosure design etc). I could suggest certain drivers should not be used, but that is about as far as I go these days.Sub woofers are the least demanding of the drivers, transient response is a joke compared to group delay.The vast majority of the time, it is the mid bass to sub woofer integration that is at fault, not the sub woofer.



I would like to see the graphs of drivers at 20 watts @ 100 degrees Celsius, that would be quite illuminating.



It is MOST interesting the specifications are mostly discussed around sub woofers, not mid bass and mid range and tweeters.



Here is a point to ponder.



If drivers measure significantly different (same make etc), can you EVER obtain a stereo image?

for subbass, I can now recommend the Peerless XXLS 10" woofer 830842.
http://www.tymphany.com/datasheet/printview.php?id=28

smooth sound, and take a caning (played over 1kW per woofer on the weekend, with no obvious ill effects).

Nominal impedance Zn 4 ohm
Minimum impedance Zmin 3.9 ohm
Maximum impedance Zo 122.5 ohm
DC resistance Re 2.6 ohm
Voice coil inductance Le 4.2 mH
Resonance Frequency fs 19.2 Hz
Mechanical Q factor Qms 8.74
Electrical Q factor Qes 0.19
Total Q factor Qts 0.19
Force factor Bl 14.9 Tm

Moving mass Mms 133.8 g
Suspension compliance Cms 0.52 mm/N
Effective piston area Sd 352 cm2

Sensitivity (2.83V/1m) 88.4 dB

Voice coil height 33 mm
Height of the gap 8 mm
Linear excursion +/- 12.5 mm
Total useful flux 2.3 mWb

please expound this idea further.....cors

If you want to talk T/S lingo, then I'm gunna throw a dirty big spanner in your works matt!

When It comes to mids, tweets, "full range" speakers, then I let my ears do the picking. As you'd expect. To hell with the specs with these speakers. I listen, then look at size for fitment, cosmetics, brand and then finally price.

But your obviously want to talk T/S.. My experience is that T/S specs are mostly ball park. No speaker that I am aware of comes with a "birth certificate" that states this particular speakers T/S specs. You can read a brochure of an amp that says that it will do "100 watts x 2 at etc specs". But if the amp comes with a birth certificate that states that your particular example actually does "112 watts x 2 at etc specs".


The same can be said about speakers. One example of speaker may come with an example of fs 63 hertz and a Q of say 0.711 yet the manufacturers spec sheet may say fs = 59 hertz and q = 0.700.

So you can want a speaker with a certain characteristic T/S wise, but the speaker that you actually buy will not be that exact spec. So it is a ball park to narrow down your choices but at the end of the day, it will come down to your own listening choices as you pointed out.

So you buy the speaker, make a box to suit the brochure speakers individuals T/S specs, then plug another speaker into the box, and expect it to be the correct size for your speaker.

My take is that I use the T/S specs as a ball park. If box builder program says 1.25 cubic feet, then I build a "trail box" at 1.4 cubic feet, chuck the speaker into it into the car and then listen. Then using scrap wood size the internal box volume down at 0.05 feet and keep listening untill you find the best sound.

An example is my wife's car 12 inch subby. reccommended size was a foot. I made a box at 1.2 feet, found that it sounded best at 0.9 feet and then made a proper box to suit the back of her car (shaped box) at 0.9 cubic feet.

Another example is an american sound off champion's set up (not RC) who had a motorized variable box volume set up. At the touch of a dash control, he could vary the size of the box enclosure and change the sound of the sub on the fly. Like I said, champion. trailer of trophies.

Some people like to muck around with box builder version this and that to tell them what should sound best. I let my ears and circular saw tell me.

But that's just an old fuddy duddy like me's opinion.

having said all of that, I generally prefer to look for sub woofers with the T/S specs to suit free air (high qms typically) or sealed box which ideally should be around the "ideal" Q of 0.707 (not sure exact number, correct me if wrong)
FS, generally depends on the car it's going into. Low for a large solid car, 30 hertz or so, and 40 or there abouts for a smaller flimsy car, like the wife's mazda. This is basically due to mechanic rattle. Soeakers with a low Fs are generally very strong in the sub lows and you will have a lot more trouble with rattle prevention in such a car as opposed to a larger more solid made car. But again, it's a generalization. There is no real indication that the subs Fs will not change when boxxed unless you are punching the figures into a box builder program and seeing what the final Fs would be in the finished system.
Xmax? generally, That isn't really an issue as most subs designed for sealed and IB are low, only subs for ported designs generally have a high xmax, I would have thought. In general I don't really consider it.
I also look at the sub's sensitivity as that will tell me what I should be driving the sub with.

Another problem when trying to consider T/S specs is their availability. Some manufacturers, pioneer for one tend to hide or simplify their specs, giving you the sum of the Q specs rather than individually. Memory is hazy here, T is the sum of E & M?
But I guess if I am considering a speaker based on T/S specs, I shouldn't be considering pioneer then should I?

Morel Supremo's come with birthsheets! (or atleast the pair i saw did).

Quality manufacturers specs are generally pretty close to their product.
They take a sample and release the average of their sample as their t/s specifications.
If quality control is in order then a woofers specs should be within 3-5% of their published, and any minor differences wont effect enclosure sizes dramatically.

Not to mention we're playing with a car environment, where most consumers couldn't care less about the speakers specs, and just want something they can "plug and play" and that sounds good.

what if your speaker has a Q of .890 to begin with?...........cors

Those are some very good points Audible, and certainly worthy of consideration for those who are interested in shopping around. Also one of the biggest reasons why I started this thread. Get people talking about the numbers, whether they are accurate (and like Fury stated, a good QA/QC should ensure that they are within a certain tolerance level) and what everyone thinks they mean/how they effect the desired outcome. All opinions are good opinions!!

And Qts is the result of the product of Qms and Qes divided by the sum of Qms and Qes (because Im sure that one was bothering you!!). Plus, there really isnt much wrong with Pioneer gear, as it tends to do very well in the markets it sells in. The cheaper gear is some of the best in their class, and the ODR and PRS gear is really a head above almost anything else on the market (personal opinion coming through here...)

I havent seen anything with a Qts that high, but if it was it would be a unit designed purely for Infinite Baffle applications. There is nothing wrong with having a higher Qts spec, if the sound produced is exactly what you want from your sound.

I haven't read this thread until tonight so sorry for late-ish comment


I don't know much about T/S parameters but this is something I've quite often pondered.

It reminds me of tubes for a guitar amp. An amp performs much better with a matched set of tubes but they cost you. If you're lucky you might buy 4 regular ones that just happen to match, like a "freak" car motor that out-performs one thats been balanced and blue-printed

Maybe thats what's going on with speakers, why one set sounds better than another of the same breed...?

Just for the record, the only specs I went by (and knew about) when I bought my speakers was RMS. The general rule that higher power should be louder. Oh yeah that, and price!


EDIT: Yay I finally reached 250 posts!

price and sound are the only parameters i need

So 12 X12' mid bass drivers wuld suit you? (IE only 1mm of xmax)

as long as they sounded good and were reasonably priced...then yes

my point was that when i bought my new speakers i wasnt like "oh no they dont have enough (insert fancy sounding TS parameter here), i wont get those" and then slap the salesman in the face

it was like "this is my budget, this is what music i like, this is where my current/old speakers were lacking, what do you recommend?"

then its like "i really think this speaker would suit you, do you want to hear it in a car?" "you could spend more money and obviously get a better speaker, but given your tastes this is the best for you"

then i listen to it with a track or two i know well, "very nice, how much" (borat style), go home and install them

yes i could have waited about 3 years (till i had the money) and got a set of Focal Be's or something like that

at the end of the day.....TS parameters mean little to me, although some (dare i say it) more educated people will take those things into account

as it turns out i couldnt be happier with what i got - so am i wrong to set those parameters when im looking for a set of speakers for me?

point



Listening to drivers only gets you so far.

You NEED specifications (the main reason for theile and smalls thesis actually) to make them into a speaker (IE enclosure etc.)

Xmax, cone area (SD) are responsible for SPL, RMS for heat dissipation, FS for band width limitation, Ohms for power amplifier suitability, cone diameter for off axis response, etc etc



None of these listening will avail you.
Still if you like most people, producing a speaker is beyond their thinking.



If you look at inexpensive computer speakers, they have the cheapest drivers going. Yet they can extract a quality(?) that most of us would struggle to emulate. IE they have created a speaker.

Point

Choosing a driver is relatively easy, making a speaker is an art form.

Daah...You're messing with my mind!