Need help understanding slope - system details noted

[kero48]

Gentlemen,

It's been a while since I have been here, hope everyone is well!! Sorry for the long post below but I wanted to be as detailed as possible with my system.

After many months of my sundown E8 ver.4 sitting in my apartment I finally got around to installing it.

Here is my current system, then I will ask my question

A slightly older pioneer head unit with (4) pioneer TS-G1644R speakers. 1 in each front door and 2 on the rear deck. All 4 speakers run off the head unit (no amp for these).

For the sub I have a JL Audio e1400d running (1) sundown E8 ver.4 sub. LPF is currently set to 80, base boost is off. We will get to slope down in the post. The gain has not yet been set the correct way so for now the gain is maybe a tad over 50%. I do plan on setting the gain correctly in the next week or two.

4ga power wire from battery to the amp with an in-line 40ANL mini fuse as recommend by the amp manual.

The sub is housed in a custom made ported enclosure fabricated exactly to Sundowns specifications which I took from their website. The enclosure is fabricated from 12 ply birch.

My H/U is current set at 80 +2 (I don’t know what the number after the 80 represents but a friend said to put +2 for the time being). Subwoofer #1 setting is to normal. Loudness is off. Base is set to +3, mid to +5 and high to +6

For the life of me after doing some research today, I can’t seem to come to an understanding about slope.

Picture of the back of my amp is here

http://images.sonicelectronix.com/images/148273/big/e1400d.jpg

My sub amp has the following settings: OFF, 12DB and 24DB.

Can someone please advise what setting the slope should be on based on my current system and sub size and why? I read today that people with closed enclosures tend to use 12 and people with ported enclosures tend to use 24. I don't know how accurate this is so I didn't put any weight on it.

How does slope affect how the sub performs or sounds? The stuff I read today really confused me.

If one uses a certain slope, does that mean the LPF should be set differently?

Any help would be very much appreciated as I am very confused or over thinking it.

Click to read more...

 

[wew lad 5,000+ posts]

a crossover is simply a roll off of frequencies below a certain threshold. a 12db slope would be 12db lower at the next octave. 24db would be the same thing just 24db lower at the next octave. i prefer 24db because you can get better roll offs and less phase issues

this picture makes it look pretty simple, various low pass filters set at 80hz

 

[kero48]

Thanks for the reply but can you put all the info into terms that I can understand, hahahaha. What you advised is pretty much I read today but I don't understand how it applies to how the sub performs, for better or worse, etc.

What does roll off pertain to and is it something a basic car audio guy would be able to discern from one setting to another? Does it affect anything about the amp and or strain on the amp, etc.

Should I be concerned about phase issues with my setup?

So, based on my system details, what would you recommend? Is there any info in my original post that is missing?

 

[wew lad 5,000+ posts]

set the lpf to 80hz and the hpf(subsonic filter) to 75% of your port tuning frequency, or turn it off if your sub is sealed.

actually, looks like your amp only has the lowpass so set it to 80hz and 24db

 

[kero48]

Correct my amp does not have HPF settings.

So if I set the slope to 24db, what benefit is there. I only ask as I not only needed the recommendation (thank you for that) but would like to understand why that setting in simple terms ROFL.

Am I over thinking this, I have a feeling I am but knowledge is power, no pun intended.

 

[maylar 10+ year member]

The slope refers to how quickly the filter attenuates, and how much output there will be at frequencies "close" to the setting.

Let's say you set the filter at 80 Hz and 12dB/octave. At 160 Hz (one octave above) power will be down 12dB, which is 1/16th power. With 24dB/octave it'll be only .004 times the 80 Hz power... basically nothing.

This means that the 24dB setting "kicks in" a lot faster, and 12dB still allows for a little output at frequencies above the setpoint. For a system with stock speakers and headunit power, I'd use the 12dB setting. It'll allow the sub to contribute a bit of midbass at the low end of where the speakers start to taper off.

If however you're doing a boom box system with mega watts of sub, you may find that the output at 100 Hz is unbearable. In that case, use the 24dB setting to limit the upper bass frequencies from the sub.

In systems with amped front stage it's nice to have that 24dB slope on the hipass. You can dial the low end down to get maximum bass from the speakers without hitting the mechanical stops.

HTH

 

[kero48]

so based on my op we know i have aftermarket h/u, aftermarket speakers, a decent amp and good quality sub. I would assume 24db setting would be better? oh by the way my h/u does not have a hpf.

i called sundown today and they advised it will be hard to set the gain on my sub amp since the h/u does not have hpf. is this accurate? they said something about my speakers will be playing while i try to set the gain on the sub amp and without the hpf the speakers (door and rear deck speakers) have no cutoff.

is there a way around this or set gain with the 50hz tone and dont worry about any possible damage to the speakers? they advised it would be best to set sub amp gain with the speakers unhooked (door and rear deck speakers). no way i am doing that lol.

i hope i explained that correctly

i am somewhat new to this so please bare with me, thanks

 

[VWBobby 10+ year member]

In plain English, it means that at 24db/octave, you have a lot "cleaner" bass from your sub.

At 12db/octave or less, you have a more "muddy" bass sound. Some of the higher frequencies leak through the crossover so you have a loose/muddy sound, compared to a tighter clamp down on the 80hz and below with a 24db/octave.

Compare the 2, and you will hear a difference //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[kero48]

VWbobby that you for explaining is more simpler terms, I will set to 24db.

Next have to make a new post about ground location.