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Originally posted over on SMD to answer a question - but I figured some folks over here may enjoy it as well : I need Bl/Bl Curve Explained - SMD Forum You will typically need a Klippel or DUMAX to measure the BL curve. You can assumme, though, that most overhung (long coils) at quite parabolic in nature... most under-hung have a flat spot in the center and then become parabolic. There are ways around this... Alpine flattens it out nicely in the new Type-R with some clever pole machine work: They machined in a bell shape inside the pole that flattens out the BL curve in the center -- here is an image from their patent: ---------- Some other examples below. First we have an overhung - the below is an approximation of the NS v.2 motor... very long gap / long coil design but still parabolic as it's overhung. As far as overhung goes the BL distortion is quite low as with the 71mm coil and 40mm top plate we achieve ~27mm linear one-way throw. * You see some of the coil sits outside the flux field and the flux is centered in the gap at highest level. ----- Next we have underhung - where you can immerse the coil in the peak flux field and it won't leave that area for some amount of stroke therefore giving you a small flat area before becoming parabolic. * One issue is the tall top plate and short coil tends to make the motors weak as there is poor flux utilization unless you use a giant magnet. ----- Now we have something really fancy called XBL^2 -- you have two gaps and the flux is steered around to immerse more coil than underhung and it also forces the flux out farther to extend the flat area of the BL curve. * Not the greatest example for SQ purposes as it's a big Neo SPL woofer... but you can see how the flux is broken up into two peak concentrations (dark blue areas) with some of the coil in each of those areas. The middle is no longer the strongest spot. As the bottom of the coil leaves the lower flux concentration it equally enters the top concentration so BL does not change for quite some time. These gaps can be stacked if necessary to achieve TONS of flat BL. ----- For the technical folks out there... I'm not attempting to fully explain any and all topologies -- just giving people a general idea of how they work. So lets keep the nit picking to yourselves. Feel free to add information if you like, though !

I'll start off by saying I had a shop do this for me. I usually don't shy away from installs but my wife works when I don't and I watch my 14 month old when she works so that gives me almost no time to do this. The car is a 1998 m3 with the stock HK system and factory amp. The midranges had been replaced by the PO with some 3.5" infinity’s. After listening to a set of HSK 3 ways and looking at the price I decided to go with the cheaper ESK 3 ways. The 163L comes with a higher excursion 6.5" (Higher than their normal ESK line), a 4" mid range and 3/4" tweeter. Linky to Hertz, which would replace the factory 5.25 in the kick, 3" infinity and factory 1" in the door. The whole album is here Install only took a day and they charged me a little over $400 for the speakers and install. Some people might cringe at the price, but to walk in, hand over the keys, and then leave with a nice sounding and loud system was worth it. Mid Comparison tweeter comparison Old Mid mount New mid mounting rings Old Mount for 5.25 New larger hole Speaker Mounted Random Shots So the mini review. I choose these because I was looking for a 3 way system to replace the factory 3 ways and there are not many options. The shop around the corner happened to carry hertz and I was confident with their ability to do the installation. I had the shop use the factory wiring. I've heard that the BMW wiring is decently beefy and read on forums that this is generally ok to do. The crossovers are also mounted under the back deck next to the amp. I run my crappy headunit with minimal eq. Treble is bumped up 1 from 0 (can go to +-8) and bass is at 1 also. The crossovers do have a -+2 attenuation on the mid and tweeter. Both are set to 0. These are powered off the front 2 channels of a sax100.4 crossed over at 50 hz. There is no rear fill. I find that these speakers sound good. I don't have years of experience in the industry or hours and hours of listening to different sets so I can't to talk about the tonal quality or other stuff like that. I know that I can turn it up as loud as I want and they play clear. I can turn them up louder then I want and they get a little harsh on the tweeter , but that is also a lot louder then I really want to listen to anyway so I don't care. I have the 6.5's crossed over pretty high so they aren’t getting the workout that they probably can handle but the set does present a high stage and my sub helps fill in the bottom that the woofers aren't getting to. I'm not missing the rear fill at all. I was worried about using a brand that has very little exposure at least here in the US. And I did have a tweeter *blow* which was quickly replaced under warranty. I think this must have been a factory defect as it happened real soon after I got the set installed. I believe these come with a 3 year so I should be covered going forward too. I do want to say that the shop did me right with this installation and that they deserve credit for doing a good job here. (I'm a satisfied customer) The shop is All Star Audio in Cumming GA. All Star Audio. They are a local carrier of Sundown too. John

Hey Jake Couple small things I'd like to comment on, these are all in good spirit ! Test the pre-finals (sorry, can't find the english term for them) and if they heat up too much move them either on the heatsink with the rest of the transistors or add some small heatskins. 5 degrees difference between them and the amp will not work right, they are crucial. Test the thermal protection circuit. Move the NTC on a small aluminum board and warm it up gradually. Too many amps have problems with this, some come with badly calibrated sensors from the factory. It's a Class AB, it runs warm by default. Change the transistor insulators to mica instead of the silicone. The difference is huge and the more heat you can transfer to the heatsink, the better Again, this is all in good spirit, I'd love such a big power 4 channel

Very well said Impious. It all goes back to the install. I tried the Hybrid stuff prior to hearing the Blues prototyes. I tried a L6, L1Pro setup (passive and active) followed by a L8, L4, L1 Pro setup (all active and active/passive combo) and just could not get the blend/sound I was looking for. I will say that I was also just not willing to really cut my truck up to get to L8 to work better. And I probably could have put more time into tuning to tweak things out. But when I heard the 1st set of Blues prototypes, I pretty much paid for them on the spot. And each time I heard them, they just got better and better. I have not pulled my hair out trying to tune them either.

All designs have their advantages and draw-backs which include but are not limited to the depth of the driver. Over-hung and split-coil designs tend to be the deepest designs -- so aren't as well suited for super shallow drivers. Under-hung can be quite shallow as you don't need alot of clearance behind the gap for the coil as BL drops off so fast afterward and the coils are short. XBL^2 tends to have the highest excursion to depth ratio possible -- I am not aware of a way to create more x-max with less depth.

I don't have the tools to show the graphs but you can also do "split coil" which results in a graph alot like XBL^2 but with alot bigger coil and more thermal power handling. You actually have two separate coil windings on the former. This has been utilized in several car audio drivers as well.

Most car audio woofers utilize over-hung for the simple fact that the coils are longer and typically handle much more abuse for that reason. A good overhung driver can also sound quite good despite have a higher THD than a flatter BL design. Many even prefer the sound generated by a driver with a parabolic BL curve as the parameter shift over excursion makes the sound "punchier" as excursion increases and the BL drops off, Qts rises, and your box gets a bigger peak in response which is often interpreted as "punch" Objectively, though, a well designed under-hung or XBL woofer (or any woofer with BL flattening tricks) will have lower distortion and is more accurate to the source... a drop off of 30% of the BL typically equates to 10% THD so we at Sundown and many other companies list x-max as the 70% BL point.

Based on listed parameters it has an inductive corner frequency of ~392hz. If you still intend on trying to use a 400hz crossover frequency, that may be pushing the envelope.

Hmm, I dont know if that was directed at me or the OP either way I dont care (and the following isnt directed to anyone in particular, to all in general). I've ran plenty of amps from mainstream to non, actually know how they work (beyond the typical understanding), and what goes into making them and I know a good amp when I see one. Some up and coming companies make great high quality amps, others do not. Dont judge a book by its cover. If you actually take the time to look into some of these mainstream amps and the technology behind them you will see what I am talking about. Dont let flashy lights and a chrome plate on the amp fool you. The MTX 4kw is the size of a typical 2kw amp for one simple reason. They do not do "through-hole" component soldering. They imprint the circuitry on TOP of the board giving them the ability to condense things much better, and group certain components together. They also have probably the best cooling mechanism I've seen. They dont just slap 2 big noisy fans on the end of it. They actually direct airflow directly over the hottest components before it makes its way past almost every component. Take Rockford for example. Nobody knocks their 4kw, hell it has awesome impedance rise adjustment capabilities. But its a mainstream amp. Where do all these mainstream companies start? the same way sundown, RE, hifonics, SSA, FI, etc. etc. etc. get started. So do you expect them to get to a large size then just shut themselves down because they are mainstream? Mainstream companies do one of 2 things: Fall off the ball and make crap products and try to let their name coast them by as long as possible before they eventually shut down. Or they continue to produce and push the market into better technology. And ask yourself, which mainstream company that is still huge makes total crap product? Almost none because they wont last. Some may have changed their vision and turned to producing more higher quality or SQ subs but its still high quality. Just because something looks simple and "hardcore" does not mean it is. I have a notebook of amp clamping results that back that claim up. Cheers! :drink40:

And of course a funky pup....

There's some truth to that statement, but how do you think a lot of these "Mainstream" companies started? From a little company catering to Audio Enthusiasts. What if (and I mean when) Sundown becomes mainstream will they be forever labeled as inferior? No, the main purpose of a company is to grow, to profit, and most of all get their name out to the public. Yes, indeed there are some shady companies, but the big names Kicker, MTX, etc all make very high quality amplifiers. It takes a lot of money for Research and Development, for products to be made in america, Etc. So the word "Mainstream" should not be something that is derogatory to a company, but shows how much work they have put into building a quality product. That ends my speech.

Gotta dust the subs a lil.

Well if you want to get louder on the same amount of power, then go for biggest cone area that you can fit with optimal volume. so how much volume do you have to work with? If you can't fit an 18" within optimal specs then a 15" would be better. Is space an issue for you?

That's how far we got before my dad had enough lol. Other two subs will be in tomorrow after I get back from the track.

I think, I took too many sub pics...Well, here we go lol.

My bundle. Long ass bit.

Amps going in. Messing with some of the wiring.

Amp rack/access to fuses and wiring. I decided to stop for tonight. I didn't have short screws and didn't wanna wake up the world with the grinder lol.

Starting on amp rack. Tore the paper out.

We don't make SPL subs fyi. They are all intended for musical applications..unless you select the "SPL" option which has ultra tight gaps on the BTL..which you cannot play daily because the coil will rub out. And HIGH QTS does not mean ONLY sealed..it means you can use it in both sealed and ported applications on the Q. If you intend on running it in a sealed enclosure, a "Standard" Q will not sound great...the High Qts version scrubs motor strength off and works much better for sealed alignments, but will still work fine ported as well.

My new jigsaw, it kicks all sorts of ass. First beauty baffle cut. My drivers seat. Primer The rain kinda stopped me, so I'll pick up from here tomorrow morning.

Ripped out some of the plastic under the box. Still more down there though. It was getting in the way so I'm just gonna put some more down tomorrow before I glue. Mounting hardware. Each sub will have four 1/4" x 5" through bolts, and four 1/4" x 2" lag screws. Lag compared to a Deckmate screw.

That is entertaining. Clearly you don't know what you are talking about. Reduction of the information down to 192 is a reduction of 7:1. Nobody can honestly believe that there is a ratio even close to 7:1 of information that you cannot hear in any recording. Try reading up on the subject.

4 ported is easily louder than 6 sealed. But if you're wanting to overpower the speakers so much (over 2000 watts per sub), you're barking up the wrong tree with the Q. You will fry them.

I see m5 hasn't been here yet. So I'll say it for him. 4-12's on 6k isn't SQ. If you really want SQ focus on your front stage. But if you want loud and clean I'd go with the 4 ported over the 6 sealed.

It's realy install dependent. The q's can definitly get real low in a seald box. I got a q 18 and it gets loud and low. But still in the end it is all about buildig a quality box to get the sound you want.

Go check the Fi website. But you want loud and low. BL's can do that.

Uncompressed audio as stored on an audio-CD has a bit rate of 1,411.2 kbit/s, over 4 times that of a 320 kbit/s MP3. Does this mean it is 4X as loud? Of course not. I am not sure what exactly it is you are trying to achieve with this one sided challenge of the difference in quality between an uncompressed format vs a compressed format. I would certainly prefer more accurate information as I set up my system. But really, it is up to the end user to decide what is best for them.

The Subwoofer DIY Page - 4th Order Bandpass Systems: Box Calculations

thats not too bad but still a little pricey how do they sound?? It is actually a good price.

Excellent choice on front stage. That is nearly exactly what has been used for two SSA vehicles, and possibly a third soon.