Phoenix Gold Phorum

hi guy
I just got 4 of these subs 8" (thanks again ttocs)
now i have to make a box for them. these are older so info is kinda hard to find.
i need someone that has a box making program help me out
i want to use all 4 of them(not a must) but they are 6ohm speaker
about 75w rms each
here is the info i have found so far

8" MB Quart subwoofers
125 Watt
6 ohm
90 db/1m
20-400 Hz
Polypropylene Cone with Butyl Rubber Surrond
Recommended Enclosure:
Sealed (Acoustic Suspension

Qts: 0.36
Qms: 3.13
Qes: 0.41
Vas: 54.4 l
Fs: 32.20 Hz
Spl: 88.50 dB

Re: 5 ohm
Pe: 125 W
Xmax: 0.005 m
dia: 0.203 m
Z: 6 ohms

Im not a bass head but would like some output. my amp is 4ohm bridgeable ppi pc2100 (400) and 2ohm stereo(200x2) with bass knob or i own a pc450 also rated 4x50
the car is very small car 1992 nissan nx2000 hatch back. i would like to make a faulse floor but not a must

let me know what you think would be the best box,size style ect with my gear(im not changing my amps)

or if someone want to trade something these make a great mid bass. this is a very low $$ build so i would like to try them but let me know

I just modeled it in WinISD and your looking at a ported enclosure (you just can't get low end extension in a sealed enclosure with these).

Best SQ enclosure looks like:

enclosure volume= 1 cu ft (per sub)
port= 3" dia x 12.5" length (per sub)
Tunning= 36hz
-3db= 41hz


If you wanted to save on space, you could do a pair of isobaric alignments. Total enclosure volume for all four drivers would then be 1 cu ft but with the output of only two drivers

Probably not what you were hoping for in terms of enclosure size, but hope this helps!

And oh ya... I would run all four drivers off of the PC2100 bridged into a 6 ohm load... perfect

shawn k wrote:And oh ya... I would run all four drivers off of the PC2100 bridged into a 6 ohm load... perfect

why not 3ohm?

nutxo wrote:

shawn k wrote:And oh ya... I would run all four drivers off of the PC2100 bridged into a 6 ohm load... perfect

why not 3ohm?

All four drivers, series/parallel = 6 ohm load

shawn k wrote:

nutxo wrote:

shawn k wrote:And oh ya... I would run all four drivers off of the PC2100 bridged into a 6 ohm load... perfect

why not 3ohm?

All four drivers, series/parallel = 6 ohm load

how wold you wire them series/parrel ALSO is not sq but just ok volume what size box

kg1961 wrote:how wold you wire them series/parrel ALSO is not sq but just ok volume what size box

Unfortunately bro, these subs need volume to hit any low frequency. These definitely seem to be more mid-bass oriented than subs. For instance... a 1/2 cu ft seal enclosure (per sub) yields an F3 of only 69hz

I don't recommend running subs in series, only voicecoils of the same sub.

With that said, two run in parallel on each channel should do the trick.

stipud wrote:I don't recommend running subs in series, only voicecoils of the same sub.

With that said, two run in parallel on each channel should do the trick.

Because?

shawn k wrote:

stipud wrote:I don't recommend running subs in series, only voicecoils of the same sub.

With that said, two run in parallel on each channel should do the trick.

Because?

With series loading, the signal arriving at the second woofer is affected by the impedance of the first. Since they are identical speakers, this shouldn't be that big of an issue, although small differences in the speakers will be "communicated" through the series loading. But because bridging also adds distortion, and parallel loading ensures an absolutely identical signal sent to both speakers, running two in parallel on separate channels is the best way "on paper". Now it's probably splitting hairs... whether you can hear the difference on subwoofers is another question.

stipud wrote:With series loading, the signal arriving at the second woofer is affected by the impedance of the first.

Actually bro, no. The "signal" is the voltage applied to the circuit (speaker voice coil). And Voltage is applied/measured directly across the positive and negative poles of the circuit, hence each coil sees exactly half (referring to 2 coils in series) of the total applied voltage.

For example. If you applied 10v ac to a pair of drivers which are wired in series. You would measure 10v ac across the total circuit (neg terminal of one driver and pos terminal of the other driver). You could also measure voltage across the individual drivers and you will see 5v ac across each one.

stipud wrote: But because bridging also adds distortion, and parallel loading ensures an absolutely identical signal sent to both speakers, running two in parallel on separate channels is the best way "on paper". Now it's probably splitting hairs... whether you can hear the difference on subwoofers is another question.

The distortion added from bridging an amplifier is very minimal and in no way will be detected by the human ear. We are talking about an increase of .5% distortion (undectable for humans) in the absolute worst case secenario and most of the time the distortion increase is much much lower than this! Furthermore, running the drivers in parallel on each channel will also increase the distortion equally as much as bridging the amp. Remember, the amp is ultimately being driven into the same load and distortion will be increase proportionally! The only difference is stereo vs mono output!


There's ABSOLUTELY NOTHING wrong with running subs in SERIES! Please take a look at nearly any manufacturer's manual for DVC subwoofers and you will see that nearly all of them will show different configurations for "series AND parallel"!

If you wanted to get REALLY tweeky. One could say that a series cofiguration is actually a more reliable circuit for the amplifier to drive! If just one of the voice coils happens to short, the amplifer will still see the load of the second good coil (hey it's better than a dead short right!?) On the other hand, when two coils are wired in parallel it takes only "one" shorted coil to short the entire circuit!

when I had them running I had a funky shaped box so I had two woofers sealed in an enclosure on each end both running 3 ohm stereo signal and loved them. tight and punchy yet with the4 woofers had the area needed to go a little lower then a single 8 would normally do.

ttocs wrote:when I had them running I had a funky shaped box so I had two woofers sealed in an enclosure on each end both running 3 ohm stereo signal and loved them. tight and punchy yet with the4 woofers had the area needed to go a little lower then a single 8 would normally do.

this is why im asking ttocs you said your box was about .4cub each and i read a post you and another guy had back in 2007 he was thinking .69cub
i think i might just trade them or sell them i really don't want to use 2.5-4 cub for 8" sub when i can get a single 10 and use .75 to have great output
3ohm stereo i waht i was thinkg of but now this has started a differnt idea problem ect for bridged

that was .4 cu per 2 woofers, .8 total for all 4.

ttocs wrote:that was .4 cu per 2 woofers, .8 total for all 4.

that sounds small i thought it was .4 per sub so 1.6 for all 4

no no no no. It was a little small but with two of them sharing the same airspace they did fine. There are a number of 10s that can do fine in .4-.5.

ttocs wrote:no no no no. It was a little small but with two of them sharing the same airspace they did fine. There are a number of 10s that can do fine in .4-.5.

i think i should just try a box .8cub for 2 use it and hope i like it. i would like anything above 40hz and it hit harder at 60hz would be my goal.
did you add anything in box?

.2 cu ft per sub yields a -3db of 81hz! I'm not saying someone wouldn't like the sound, but these are not true "sub"woofers. I'm sure they would make excellent midbass drivers however!

kg1961 wrote:i think i should just try a box .8cub for 2 use it and hope i like it. i would like anything above 40hz and it hit harder at 60hz would be my goal.
did you add anything in box?

.4 cu ft per sub yields -3db @ 70hz and -12db @ 40hz

Bro, isobaric!!!

shawn k wrote:

stipud wrote:With series loading, the signal arriving at the second woofer is affected by the impedance of the first.

Actually bro, no. The "signal" is the voltage applied to the circuit (speaker voice coil). And Voltage is applied/measured directly across the positive and negative poles of the circuit, hence each coil sees exactly half (referring to 2 coils in series) of the total applied voltage.

For example. If you applied 10v ac to a pair of drivers which are wired in series. You would measure 10v ac across the total circuit (neg terminal of one driver and pos terminal of the other driver). You could also measure voltage across the individual drivers and you will see 5v ac across each one.

stipud wrote: But because bridging also adds distortion, and parallel loading ensures an absolutely identical signal sent to both speakers, running two in parallel on separate channels is the best way "on paper". Now it's probably splitting hairs... whether you can hear the difference on subwoofers is another question.

The distortion added from bridging an amplifier is very minimal and in no way will be detected by the human ear. We are talking about an increase of .5% distortion (undectable for humans) in the absolute worst case secenario and most of the time the distortion increase is much much lower than this! Furthermore, running the drivers in parallel on each channel will also increase the distortion equally as much as bridging the amp. Remember, the amp is ultimately being driven into the same load and distortion will be increase proportionally! The only difference is stereo vs mono output!


There's ABSOLUTELY NOTHING wrong with running subs in SERIES! Please take a look at nearly any manufacturer's manual for DVC subwoofers and you will see that nearly all of them will show different configurations for "series AND parallel"!

If you wanted to get REALLY tweeky. One could say that a series cofiguration is actually a more reliable circuit for the amplifier to drive! If just one of the voice coils happens to short, the amplifer will still see the load of the second good coil (hey it's better than a dead short right!?) On the other hand, when two coils are wired in parallel it takes only "one" shorted coil to short the entire circuit!

I don't know about you, but I haven't seen manufacturers advertise running woofers in series in a long time. Voicecoils in series, yes, but rarely ever speakers. Certainly not since DVC became more common. In fact JL explicitly tell you not to do so on their website:
http://mobile.jlaudio.com/support_pages.php?page_id=161

The speakers in series would see the same signal if they were resistive devices rather than inductive. If you were to run two entirely different subwoofers in series, the impedance spikes in one sub would cause dead zones in the other one. Even the same speakers from the same company have minor inductive differences, which parallel wiring avoids completely by isolating the loads in separate circuits.

I agreed that bridging distortion is inaudible and impedance differences are likely not to be an issue, nor functionally "incorrect", but I stand by my point that a parallel stereo load is the best on paper

stipud wrote:I don't know about you, but I haven't seen manufacturers advertise running woofers in series in a long time. Voicecoils in series, yes, but rarely ever speakers. Certainly not since DVC became more common. In fact JL explicitly tell you not to do so on their website:
http://mobile.jlaudio.com/support_pages.php?page_id=161

Funny, I check the site and they refer you to the link "DVC tutroial" when regarding to "avoid wiring drivers in series at all costs" but then they NEVER explain why in the tutorial

stipud wrote:The speakers in series would see the same signal if they were resistive devices rather than inductive. If you were to run two entirely different subwoofers in series, the impedance spikes in one sub would cause dead zones in the other one. Even the same speakers from the same company have minor inductive differences, which parallel wiring avoids completely by isolating the loads in separate circuits.

Ok... I agree with you here and I see what you're getting at. Using two completely different drivers will cause eratic voltage swings between the two. However, using two of the same drivers, with good quality control, should not pose a problem. There would have to be something considerably wrong in the manufacturing process for two of the same drivers to be so far off that it would yeild unsatisfactory results. That being said, even "if" one were to run two different drivers, nothing catostrophic should occur.

stipud wrote:I agreed that bridging distortion is inaudible and impedance differences are likely not to be an issue, nor functionally "incorrect", but I stand by my point that a parallel stereo load is the best on paper

I agree, on paper... yes... in practice no

Good talk

does your calculator take into account (two subs in one shared enclosure) x 2?

ttocs wrote:does your calculator take into account (two subs in one shared enclosure) x 2?

Me?

Yes

show shawn if i made 2 box sealed what size would i make them? for the better maybe not the best sound i would not like a -12db at 40hz but i also would like not to use about 3cub for 8" subs

kg1961 wrote:show shawn if i made 2 box sealed what size would i make them? for the better maybe not the best sound i would not like a -12db at 40hz but i also would like not to use about 3cub for 8" subs

A 1 cu ft sealed box for two of your eights has a -3db of 69hz and -12db @ 37hz


Your "best compromise" option IMO is to utilize all four drivers in a compound isobaric enclosure!!!!! Here you're looking at just 1 cu ft (plus port displacement) tuned to 40 hz. I would recommend a subsonic filter for this ecnlosure! -3db is 41hz and actually has a smooth 1db bump centered at 65hz.

Let me konw if you'ld like to know more!