my re8

neomagus00

Hmm... i've noticed a small issue with my new re8-enabled setup, namely that it hits late - to the point that I can feel the delay with my hand when i touch the sub. i haven't been able to find a low resistance air-wound inductor of the appropriate value for the xover i need to build (anyone know where to get one?) so i'm hacking my music in the following way - the sub is wired to the right channel, and the mains are wired to the left. every song i play is digitally redone such that the right channel is lowpassed at 80Hz, and the left highpassed at 80 (with some volume matching thrown in, and a little bit of eq). it's with a very good program, namely GoldWave, so i know that's not the problem; any reason that this should be happening? it shouldn't have anything to do with group delay, it's only a first-order system...

exalted512

what do you mean you can feel the delay?
no entiendo
-Cody

neomagus00

when i stick my hand on the sub, i can hear the kick (the higher notes of it at least) from the mains, then a split second later i can feel the sub jump... there's a definite delay...

exalted512

do you have some type of delay on the HU?

exalted512

ahh...and im not getting the re8 for $35 anymore...
im getting the 10 for the same price:D
-Cody

LittleCar_w/12s

Hey, honestly.. call every radioshack around and ask if they still have one of those 'optimus' sub coils... lemme look up the no. for you if you need... they'll cost $11 or something, and perfect for subs... I believe they are roughly 100Hz down for a 4ohm load, or 50Hz down for a 2ohm load..

neomagus00

jerry (i think) - i dont think they carry the coils any more, ive looked in several shops and online, and nothing like that exists...

cody - no hu, this is ht use ... but no, no delay, i checked it out... tis strange, no?

exalted512

has to be something with your reciever then no?
-Cody

neomagus00

that's what i've been assuming, but it's never done anything like this in the past... this weekend i'm going to take it outside and see if some strange resonance in my room is causing me to think it's hitting late... i dunno if that's not it...

LittleCar_w/12s

Good to know that that's not in your car... I think I would end up driving in circles or something strange if I had it rigged like that...
And the Optimus coils will be hard to find, they are disco'd. Never hurts to call and ask. A lot of radioshacks will have them lying around in the back along with all the other components (speakers, subs, tweeters, etc) that are disco. Not even the managers know what they have back there.. believe me I've worked there...

If not, you can call RSU (radioshack unlimited) at '1-800-the-shack' and ask for a 40-1326 (High-power choke coil)
See this page for specs.

This is rated at 200w, but will handle a good bit more... i've run over 300 through them.. R/S also has a pre-built crossover network that handles about 100w, but I don't know the number for that.

LittleCar_w/12s

BTW, "Optimus" brand at R/S: the passive components at radioshack are "realistik" brand, and the Active (receivers, etc) are made by "Pioneer"
So they are basically just b-models from good companies - good stuff.

neomagus00

cool, i'll look into it... so i've decided that maybe my box is at fault, cause it's not as perfectly fitted as I know i can make it, so i'm going to build a new one on sunday... a slightly bigger one to maybe take some boominess out, more bracing, sealing it right the first time... we shall see...

LittleCar_w/12s

I would think that increasing the volume would make the boominess worse, as it will lower the acoustic susension for the driver, and in turn it will have a less acurate response.

neomagus00

i'm hoping that it won't make it sloppy, but it's exceedingly tight right now, to the point that maybe the box is too small, causing boominess... i'm not gonna go crazy, maybe a 25% increase (it can't be any worse than my current box :rolleyes: ). plus i like getting it right, even the second time and the box is very small, so i have most of the sheet left over from this one, all i have to buy new is caulk & liquid nails...

neomagus00

so, i built my box, and it is a bitchin piece of equipment, if i may say so myself. i should have pix by late tomorrow, but i haven't tested it yet - waiting for the sealant to dry... listening reports to follow...

exalted512

ill be getting me RE10 that i got for $35 sometime soon...i have no idea what im going to do with that...i sold the momo sub that i got from CC to a friend for the price i paid for it, found an amp for him on sale at CAF and its in his truck right now....good stuff
-Cody

neomagus00

cool... well, properly installed, this little thing performs very well, especially considering it's an entry level 8"... only problem i've found is that it is very quiet... my mains are running at half again as much impedance as the sub, and they're at -20 dB relative to the sub right now (that's around 10% of the power going to the sub)... and this is with the whole setup in a fairly small, resonant environment...

btw, i noticed something strange with the new box - it's now quieter for a given volume input than with the smaller box... i thought larger boxes were supposed to be more efficient?

MacLeod

Smaller boxes are louder.

More proof? Go to any review of a sub in Car Audio & Electronics. They list max db at 2 different box sizes and the smaller box is ALWAYS the loudest albeit not by a lot, usually 2-4 db.

neomagus00

huh... i would have figured the opposite, but evidence can't be wrong...

MacLeod

This is some of the test results Im talking about:

Kenwood XW1300DVC (Dec 2003 issue)
.55 = 117 db
1.0 = 115 db

Orion H2 12.4 (The daddy) (Dec 2003)
.55 = 122
1.0 = 120

MB Quart PWE302 (Feb 2004)
.60 = 112
1.0 = 110

MA Audio 1200XL (Apr 2004)
.75 = 118
1.25 = 116

Pioneer TSSW12S4 (Nov 2004)
.65 = 111
1.0 = 109

JL Audio 12W6v2 (Mar 2004)
1.0 = 116
1.25 = 115

As you can see, the difference is very small but the smaller box is louder with the same power.

I love it when Im the only one thats right!

neomagus00

is this in car? or anechoic (sp?)? i think i understand why, at xmax, the smaller box is louder, but i'm trying to rationalize the larger box being louder at a given input voltage... but thanks for something to think about

MacLeod

From what I can tell, the output tests were done on indoors in a lab or something of the sort.

On a side note, the Orion H2 article had a graph for the BL curve in both the .55 and 1.0 box and the curve for the .55 box is drastically flatter than in the larger box.

exalted512

when building sub boxes, you dont want a straight line...the lower frequencies will be louder than the higher freqencies
-Cody

neomagus00

though i've never seen a bl curve, i am imagining it as being high on the left and then decreasing as frequency increases? or is it the other way round? and, you generally want a rolloff below a certain frequency, but that frequency depends upon the vehicle; at the extreme end of the spectrum, if we're talking about a convertible, we'd want a perfectly flat SPL curve... which brings up the question of how the bl curve relates to the spl curve in a given car and in an anechoic environment...

exalted512

in car---you want your frequency response to go down the lower the frequency you go...the natural effect of cabin gain will level it off
-Cody

neomagus00

yep; now the question is how the bl curve in-car relates to the frequency response curve, also in-car (which will vary slightly vehicle-to-vehicle, but that's not particularly important here)

BIG EDIT: see the 'divided boxes' thread, but to solve the problem... mac, are those maximum spl's or spl with the same input power? for the same sub in a differently-sized box?

Joelsbass

Originally posted by neomagus00
yep; now the question is how the bl curve in-car relates to the frequency response curve, also in-car (which will vary slightly vehicle-to-vehicle, but that's not particularly important here)

BIG EDIT: see the 'divided boxes' thread, but to solve the problem... mac, are those maximum spl's or spl with the same input power? for the same sub in a differently-sized box?

for what he said to be correct it's going to be spl with the same input power, keeping all else the same (signal, power etc...) a smaller box will be louder than a larger box...


btw, excuse me while i admit my ignorance but wtf does anechoic mean??? i'm guessin it's a fancy way of saying in car... but as i'm sure i'm not the only unfamiliar with it i'm gonna be blunt and ask

neomagus00

sorry i didnt define - anechoic means no reflections from a car or room or whatever and thus is the true unadulterated measurement of a sub/box system's response; usually this is approximated by a specially designed room that disperses the waves coming out of the sub so that you get extremely accurate measurements of the actual frequency response, without cabin gain or any such thing.

and, now that i read it again, he said maximum spl... i would assume that means xmax or pmax (maximum thermal power for the sub)... so it could very well be that the smaller box is louder at splmax, but only with more power... thus the larger box is indeed more efficient... mac, some clarification?

MacLeod

First, the BL curve has nothing to do with frequency response. The BL curve shows the motor strength of the sub as it moves in boths directions. It shows how symetrical the magnet and mechanical systems are to each other. The more symetrical, the less distortion.

Second, from what I can tell from the articles, the same amps are used for each box.

neomagus00

okay, so a bl curve is a relation of field strength to excursion, then? and has nothing to do with frequency?

ADD: okay, i just finished reading CA&E's W6v2-D4 test, and here are the relevant numbers:

1.00 ft^3: SPLmax = 116.5; Voltage = 100
1.25 ft^3: SPLmax = 115; Voltage = 90

while i'm not positive on the exact sensitivity calculation, because it's logarithmic, it seems obvious that the larger box is more efficient

MacLeod

Thats my understanding.

Disclaimer:
I have no education in electronics or physics. I read car audio magazines religiously and read other publications on the net and other forums and everything Im spouting is my interpretation of what Ive read so dont take me as an authority!