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Subwoofer for music design assistance requested. Subwoofer recommendations welcome as well. - Page 2

post #31 of 39
kind of like this: http://video.mit.edu/watch/physics-demo-lenzs-law-with-copper-pipe-10268/
post #32 of 39
interestingly, this inductance effect is used for positive purpose with crossover inductors (big ones of which are used for low pass filters to midrange drivers). you'll notice that there are two broad categories of inductors: iron core and air core.

with an iron core inside the windings this back emf effect increases the inductance and so not as many windings of copper are required for a given amount of inductance. copper costs more than iron, so these inductors cost less.

so why even both with air core inductors? because putting that slug of iron in there causes problems. again folks will debate that. enhanced perceived quality while upgrading to air core inductors may be a placebo effect to some, but to others it is worth the cost in audible improvement. so what would be the best case? remove the inductor and its inductance effects altogether with an active system. by using a digital crossover before amplifying the signal, there is no inductance effect. so how does it sound? ask the guy who designed the jbl Everest. when he switched his model to full active, the bass response became more punchy. i.e. it improved in the time domain which is exactly what one would have expected.

so how does this relate back to speakers? the coil around the pole piece is like a crossover inductor with an iron core. there are ways to shield, if you will, the iron core from the voice coil and cause it to behave more like an air core crossover inductor. but as you probably would guess, that is tricky and requires additional work and materials. the td18h approach is to put a copper sleeve over the pole piece. 2242h sticks a copper ring inside the gap between the voice coil and the pole piece. not as good, but still really good. the 18lw2400 has three rings, but i'm not sure where exactly they are located or what materials are used. tough to say, but probably works about as well +/- as the 2242 approach. the 18ps76 has nothing, but it still only uses dual layer voice coil and big magnets so that amount of material in the gap is minimal. not as good as the other approaches. the Dayton selects a smaller magnet to save cost, employs no inductance control technology, and worse, doubles up the number of windings in the gap to bring bl up to where it needs to be. so, there is no free lunch on this one or at least i'm not aware of it.

but, again, this is with respect to only one dimension of the driver and there are others to consider.
post #33 of 39
Thread Starter 
Badmansound- Hornsrep looks like fun to mess around with. Thanks for the link. As for the Daytons, I am going to pass on that idea. What is the lab 15 however?

Bassthathz- Wow that is ruler flat on the mains! What drivers are you running out of curiosity? And what kind of processing?
post #34 of 39
Thread Starter 
Thanks for the write up. I remember seeing that demonstration done before but I forgot how it applied to anything. Haha, A refresh is always nice.

At this point in time, I think I am ending up where I originally started off a month ago. With an AE driver. I was originally looking at a smaller driver but why not go with the 18". The TD18H+ seems to not have any of the drawbacks that some of the other drivers do. It looks to be an even better driver than the JBL at more than half the cost!
post #35 of 39
Quote:
Originally Posted by todd.brust View Post

Bassthathz- Wow that is ruler flat on the mains! What drivers are you running out of curiosity? And what kind of processing?

Mains:
http://www.diysoundgroup.com/waveguide-speaker-kits/other/bwaslo-15-kit.html

DAC:
http://www.oppodigital.com/blu-ray-bdp-105/
http://www.esstech.com/PDF/ES9018%20ES9012%20Product%20Brief.pdf

Pre-amp (Optional, but strongly recommended):
http://shop.emotiva.com/products/xsp1

EQ + XO:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=248-669

Main Subwoofers:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=293-666

Kick bins:
http://www.parts-express.com/pe/showdetl.cfm?partnumber=295-036

Amps:
Gruppen Clones for the mains and subs, and Crown iTech for subs, and a few "lesser" quality amps for others subs.
http://www.china-sanway.com/Product.asp?BigClassName=FP-new%20series%20Switching%20Power%20Amplifier
http://www.pssl.com/!ZrsStXPqOV1wZerlyMrOYA!/Crown-IT8000-Power-Amplifier-2100W-8-Ohms

Misc Power Quality products (optional):
http://www.psaudio.com/products/power/power-plant-premier/
http://www.cyberpowersystems.com/products/ups-systems/pfc-sinewave-series/OR2200PFCRT2U.html


If ONLY all these products had existed 7-10 years ago and I knew about them, I could have saved myself $13000 trying to find something of this quality. Oh well. redface.gifrolleyes.gifcool.gifwink.gif
post #36 of 39
the td18h should do well in an 8 cubic foot box (230 liters with port). you can even bridge your xti 1k and it'll take about all its got (well, 80 volts at least, of the 90 that the xti 1k can supply). good down to 30 hz, with a 27hz hipass.

it will give you a little more than a pair of Lab15s in 110 liter (with port) boxes will with the xti 4k. the Lab boxes would catch back up if you could bring them to xmax though (about 59volts).

http://www.parts-express.com/pe/showdetl.cfm?partnumber=290-575 (link to lab15)


AE claims their copper ring gives their 2.5" VC 2 to 3 times as much heat dissipating area than 3 or 4 inch coils. I hope thats true, as most 2.5 inch coils i have experience with (the lab 12 for instance) start running into power compression issue around half their rms rating, but the lab 12s were never known to dissipate heat well.

If and when you get it built. bring er up to war volume with this track please, I'd like to hear your thoughts on it.
post #37 of 39
nice track.

spectral content of that track, short sample, but it appears to be the same the whole way through. 30hz and 38hz are the bass lines.

post #38 of 39
yep, that matches the measurements I did a little after buying it, heres the wholes song average.

Image Resized at http://www.shrinkpictures.com

As far as *musical* bass is concerned, I find there is very little content under 30 hz in electronic music tracks (that sell over 100 copies). There will surely be the tail end of sweeps that extend down into the mid to low 20s, but as far as actual components of the bassline, thats where people usually draw the line, esp in in deep bass music like this, because the whole idea is to be immersed in bass, not imagining where the bass would be if those 12 dual 18s in front of you could actually play the notes wink.gif

Its actually probably not a good idea for you to blast your tune on the AE tdh18 in 8 cubic feet, as the heat of the bassline will be around tuning... meaning the cone will be moving verrry little, so even with its 2 to 3 times heat dissapating action... you might still turn this track into a woofercooker.


We're still wondering what type of music you actually listen to though OP! most of the designs have been sacrificing efficiency and output to get you a solid 30hz, because this is the floor for music, and the wheelhouse for HT.
post #39 of 39
"Its actually probably not a good idea for you to blast your tune on the AE tdh18 in 8 cubic feet, as the heat of the bassline will be around tuning... meaning the cone will be moving verrry little, so even with its 2 to 3 times heat dissapating action... you might still turn this track into a woofercooker."

that is what the 38hz is for. woofer cooling. :-)~
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