Are all filters assigned a slope??

[m R g S r]

I called alpine tech support with a simple question and got a bs answer basically.

Me" hi I have an alpine pdx 1.600 and was wondering what the numerical value of the subsonic filter slope is (in db/octave)?

Him: what size speaker are you using?

Me: I'm using a 3015lf which requires a STEEP slope at 30hz

Him: what size is that?

Me: it's a 15" but that's irrelevant

Him: I would just leave the filter off then

Me: I'm not asking that, all I want is the slope of the filter

Him: the subsonic filter will not let any frequencies below that point into the speaker.

I don't believe that. All I asked was for a simple answer and he couldn't give it to me. Unless I'm wrong and the crossover isn't assigned a slope and actually does in fact filter out ALL frequencies below that point?

Please help! Should I call tech support again?? I want to keep my 3015lf in one piece!!

[sofaspud]

To answer your question... yes. But I don't recall ever seeing "assigned" as part of the terminology. Sounds kinda arbitrary.
When you said "STEEP slope at 30Hz" you weren't being very precise either.

[Shaun]

variable low-pass filter (50-200 Hz, 24 dB/octave)

From Alpine PDX-1.600 Mono subwoofer car amplifier 600 watts RMS x 1 at Crutchfield Signature

[m R g S r]

That's the low pass filter not the subsonic which is selectable between off 15hz or 30hz.

And sorry for not being more specific but I did tell him that the speaker I'm using required a 48db/octave slope at 30hz and his final answer was I wouldn't use the filter with that size speaker. I guess he thought I was using it in a car audio app with a 15" sub with 30mm xmax :/

[Shaun]

Pity he can't answer you question, but it seems as if the specification is not available. I'd guess that it would be 6 or 12dB/oct. The steeper the slope, the more the component count. If it does indeed have a steep slope, you can be sure the manufacturers would no overlook listing the specification.

But then again the support guy has a point: why do you need such a steep filter? Your system will have high group delay at the low end.

[18Hurts]

You can test it with a frequency program on your computer, a resistor and an amp meter

It would be easier to call the guy back and tell him the amp will be used on a boat for a beach party driving two PA subs that require at 48dB filter. I'm sure the guy is used to calls from kids all day asking if the amp will drive 12 subs. Tech "Is that all in parallel or series-parallel?" Customer "Huh?"

[m R g S r]

I need it because the music I will be playing may have content under 40hz and the amp can put out more power than it takes to exceed xmax at 30hz. So I want to make sure i won't be blowing the sub if I turn it up (and it will be turned up the majority of the time it's in use)

[sofaspud]

IMO and generally speaking, customer service is like chasing rainbows... an exercise in frustration. You could call them back and explain you need real engineering tech support, not an applications rep.
Otherwise you might try opening the case and finding the subsonic filter section, passing along the schematic to the forum members via pics and/or a detailed description.
"...required a 48db/octave slope at 30hz" seems quite unusual to me. How was that calculated? 2Bhonest I'm inclined to think the 30Hz setting will work for your speaker.

addendum: I was looking at the amp and speaker on other tabs while composing this.

[m R g S r]

If you guys feel that any slope filter at 30 hz is good enough than I'll just run it as is. My concern is that this is being used on a beach radio and I'm not the only one controlling the volume. When some drunk idiot turns the volume all the way up on a track with heavy bass notes, I don't want my subwoofer to blow then be out of a sub and $. I basically want a bulletproof setup, hence the need for such a steep slope.


Also, on the eminence 3015lf spec sheet it says "use a steep high pass filter at 30hz" (going off memory but I'm pretty sure the wording was very close to that)

[18Hurts]

The 30Hz filter will be 3 dB down at 30Hz,

I think he is using such a steep slope requirement to make up for a sub requiring a higher frequency filter. The Fs for the 3015LF is 42 Hz so could be run in a ported or horn box down to 30Hz tuning. I'm assuming it is tuned for 40Hz for size considerations and that is were the filter should be. Did he run a program to calculate excursion with his box?

What subwoofer type are you using? Ported for ?? Hz, horn or bandpass?