# Midbass slope for SQ?



## Rapture333 (Jun 9, 2013)

Hey guys, I've been playing with my crossovers lately and noticing how big of a difference they for midbass. I have Morel Virtus 6.5" woofers and a Morel Ultimo SC 12" sub. I had them crossed over at 71hz @ 36db slope, the midbass sounded clean but lacked some "presence" and "blending". I then dropped the sub down to 24db and alternated between 30db and noticed I liked how it sounds. I've been playing with a 24db for the subs and the woofer but sometimes I feel that it might be too overbearing for SQ, not sure. What do you guys recommend trying out for maximum SQ?


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## Rapture333 (Jun 9, 2013)

I've also heard that sealed enclosures have a natural 12db slope rolloff. So would I have to set my sub to a 12db slope to equal a 24db slope to match my woofers (and to be in phase?)


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## FG79 (Jun 30, 2008)

What kind of amps are you running? They play a big role in these crossover settings. 71 hz @ 12 dB with a 6.5" woofer is no big deal with the right amp. 

Don't worry about the math. Just experiment with points and go at it from there.

Drop down to 18, then 12. See what you like more.

I would match the sub to the midbass as far as slope. 

I'd also overlap the frequencies....have the midbass high pass set lower than the subwoofer low pass. Not much (say 70 hz & 90 hz) of a difference needed.


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## Rapture333 (Jun 9, 2013)

I'm running a PDX-F6 and PDX-M6 both alpines. I just set the woofers to 24db slope and the bass to 12db and so far I like how it sounds. What's the theory behind setting the woofer and sub slightly apart? Is that to account for the increase in sound at the crossover frequency? Thanks.


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## FG79 (Jun 30, 2008)

Rapture333 said:


> I'm running a PDX-F6 and PDX-M6 both alpines. I just set the woofers to 24db slope and the bass to 12db and so far I like how it sounds. What's the theory behind setting the woofer and sub slightly apart? Is that to account for the increase in sound at the crossover frequency? Thanks.


It has to do with getting the woofer to play more bass and push the illusion of bass upfront. 

Can be done without it, but harder to do. 

I had PDX amps....the authority on the low end is not quite what I like, but you should still be able to drop the woofer slope lower. 

Another underrated aspect is how big is your car/truck door? I had a big 2 seat coupe door, which helped with the low end.


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## Rapture333 (Jun 9, 2013)

I have a big 4dr Dodge Charger, so I suppose that helps a lot with the low end. 

Hmm, and I'll try what you said, I'll keep the woofers at 71 and bump the sub up to 90hz and see how it sounds in the morning.


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## therapture (Jan 31, 2013)

I might be doing it wrong....

But I have been able to get my "bass up front" very effectively running no under/overlap, using both HP and LP of the mid and sub at 75hz/24db.

I had both at 48db slopes and while I do not notice much difference in actual output, I definitely gained a better integration between the two by going down to 24db slopes.


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## Rapture333 (Jun 9, 2013)

After experimenting lately I've noticed the following: I've had my HPF/LPF of my mid and sub crossed over at 71hz at a 36/db slope. It sounded clean but the sub bass was easily distinguishable as a separate driver although it was harder to localize. I dropped the slope to 12/db slope for the sub and 24/db for the woofers. The bass sounded better but it didn't sound realistic. I set the sub and mid to 24/db slope and i have to say, they blend perfectly. I think the ideal slope for sound quality is either 18/db or 24/db based on preference and car size. I liked to crossover at the same freq as this minimized phase issues and blended better. Still experimenting whether or not I like 18/db or 24/db more.


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## Hanatsu (Nov 9, 2010)

Measure your system. Discussing slopes without knowing the real acoustic slope is meaningless.

Sent from my Samsung Galaxy 3 via Tapatalk.


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## therapture (Jan 31, 2013)

Speaking of measuring, Hanatsu, I have been "ear tuning" for a few weeks now, since I retuned completely a couple months ago. Using bandpassed pink noise tracks, all the ranges are _stacking very nicely _up the middle, with no obviously overloud ranges. I am quite happy with the response and integration.

Now it's time to get the mic back in and see where I have ended up. Although I am leary of using just the measurements since my left and right ear apparently hear somewhat different. Every time I match the curves closely via mic and plots, I get the left side too much in my face/too loud.

I feel strongly that I have cured the hole I had around the 70-100 hz range with the new 24db slopes and tuning by ear. I even ended up with the left side crossed at 80hz and the left at 75hz HP, and that seems to take the left side fatness down (like the bass gets trapped in my knees a bit on certain music). The sound is full and robust in the midbass and lower midrange, without bloating male vocals.


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## sqnut (Dec 24, 2009)

I like to crossover low and use steep slopes. My sub and midbass are crossed at 50hz, with the sub LP on a 48db slope and the mid HP on a 24 db slope. At the end of the day it has to sound right. Good integration between the sub and mid is as much about arrival times as it is about the overall response in the 40-160hz zone. For tight punchy bass your midrange response ~500-3khz, plays a big part. 

Acoustic Slope: With the sub LP at 50 hz on a 48db slope (12 db from the hu and 36db from the bit10), 100 hz should be 48dbs lower than 50 from the sub, right? But it isn't. If I play only the sub and measure the 50hz pink noise track at say 85db, then 100hz measures ~55db. So even with a 48db electronic slope, my actual acoustic slope is about 30db/oct. The car is a bass amplifier. 

On the other hand I'm running my midbass close to its Fs and the acoustic slope on the mid bass below ~60hz, is to the tune of 45db per octave. While the electronic xover is set at 50hz the actual acoustic xover is closer to 70. The acoustic slope plus the work at the eq ensures that the sub plays the 20-70 hz range and the mid takes over from there. 

Another reason for running the sub low is to avoid resonance issues. If you're looking at mic'd measurements for the 30-80hz region and you find a 5db bump at 50hz don't just cut 50hz by 5db. 40-50hz is good for the mass and rumble in your low end, tactile bass. Keep in mind that a 5db peak at 50hz is much less noticed than a 5db peak at say 1khz. That's just the way we hear. So temper what you're measuring against what you're hearing. If it doesn't sound right, it isn't. 

While there are no specific 'sq settings', you're using the xover points, slopes and the eq to tailor the overall response. Dialing in the correct response is 90% of the battle. Each car and instal will have its unique response signature for achieving good sound quality. But all these unique curves will have similar shapes. Measure to get a base curve going and then learn to use your ears to get it sounding good.


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## sqshoestring (Jun 19, 2007)

I agree you really have to go by ear and experiment due to all the variables. You can also run into issues if the MB can't handle going too low or just can't produce down there (one that can usually is nicer). All that said I prefer lower slopes of even 12 if I can get away with it, and then spread the xover points for less overlap usually (depending). But I also run IB subs so I don't have a rising curve on the subs like many sealed would have. Also note your phase can change for any slope change. I would have a much different xover setting for a sealed sub in fact found a PEQ is awesome as I hate rising curves on subs. I had a higher fs/lower qts sub IB and had the same issue the PEQ killed it so nicely. For me the sub localizes and I don't like that at all. I'm not saying you don't want high slope settings in some setups, sometimes that works best. I just feel if other things are right I can get a better sound with lower slopes, a smoother response/integration of the sub. I'll change drivers/setup/TA to help make it work that way. Some say high slopes are best but I've not had that experience above about 24db is high as I normally have used...but just my .02. I always say try lots of things first to see where you are at, and its always faster to tune in that way for me.


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## therapture (Jan 31, 2013)

Very interesting sqnut, the parts about acoustic slope and crossover points to avoid resonances in the sub...but would it stand to reason that in my case, only having 6.5s for mid bass duty, that it wouldn't work as well for me as compared to having a 8" that could run much lower?


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## MacLeod (Aug 16, 2009)

I cut my mids down low. I have my Polk SR 6's cut at 40 Hz @ 24 db and my sub is also at 40 Hz @ 24 db for competition but 63 Hz @ 24 db for daily driving. 

Itll depend on the type of music you listen to as well. I listen primarily to heavy metal so I need to dig down low on my mids and overlap with my sub in order to make up for the pretty weak midbass thats generally in metal recordings. 

Cutting both my mids and subs at 50 Hz @ 24 db is maybe the "cleanest" sounding but I get a little better up front impact with them digging down to 40 so its worth a little trade off in the cleanliness department IMO.


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## therapture (Jan 31, 2013)

I am wanting to have a "metal" tune on a preset...I listen to some stuff like In This Moment, Amaranthe, etc. And I am wanting a bit more impact for that as you noted. I will have to play with that a bit tomorrow.


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## sqnut (Dec 24, 2009)

sqshoestring said:


> Also note your phase can change for any slope change.


The relevance of phase shift due to steeper slopes is over rated. Can anyone describe what this phase shift sounds like? If at all you can hear this phase shift, you're only hearing it in the response domain. That's why you have an eq. 24db slopes work well on the mid bass and tweeters. But on the sub I would use a 100db/oct I could could . Steeper slopes keep the chaos of two drivers playing the same frequency, down to a narrower band. With some eq work, for me 24db/oct gives cleaner sound than say 12/db even with 31 bands of eq per driver, ymmv. Of course, it also depends on vehicle, install, equipment etc. 

[edit] It's not about the order of slope per se, but more about keeping a naroow bandpass for the region where two sets of drivers are playing. I don't subscribe to the theory of blending drivers over a wider band. For one it reduces the focus in your imaging, specially if the drivers are well apart. Second, blending the drivers over a narrow range seems to keep the sound cleaner. Maybe the two points are the same because tonality and imaging go hand in hand. If one gets better so does the other. 

So steeper slopes is my way to keep this 'blending band' narrow. [edit]. 



therapture said:


> Very interesting sqnut, the parts about acoustic slope and crossover points to avoid resonances in the sub...but would it stand to reason that in my case, only having 6.5s for mid bass duty, that it wouldn't work as well for me as compared to having a 8" that could run much lower?


I'm running 6.5" mids and the Fs on the Polk SR-6500 per it's white sheet is about 60hz. At 50hz the output is primarily from the sub. The mids output at 50 is only for some degree of presence upfront. I am not trying to match the sub and mids output at 50hz. That just ain't going to happen. Not with a 6.5" driver.



MacLeod said:


> I cut my mids down low. I have my Polk SR 6's cut at 40 Hz @ 24 db and my sub is also at 40 Hz @ 24 db for competition but 63 Hz @ 24 db for daily driving.
> 
> Itll depend on the type of music you listen to as well. I listen primarily to heavy metal so I need to dig down low on my mids and overlap with my sub in order to make up for the pretty weak midbass thats generally in metal recordings.
> 
> Cutting both my mids and subs at 50 Hz @ 24 db is maybe the "cleanest" sounding but I get a little better up front impact with them digging down to 40 so its worth a little trade off in the cleanliness department IMO.


Dude is heavy metal music, or noise? I listen primarily to classic rock and some 80's pop, I'm with you that 50-60hz seems to be the sweet spot for a daily drive, at least for our set of drivers.


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## Hanatsu (Nov 9, 2010)

I agree with sqnut, phase shifts related to steep slopes are of little importance in terms of audibility.

Sent from my Samsung Galaxy 3 via Tapatalk.


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## gregr1189 (Apr 29, 2013)

I think first and foremost maintain a flat consistent frequency response wherever you decide to set the crossovers. In my experience midbass door speakers start to lose some output below 100hz and continue dropping off. I set my crossover there first to limit excursion and reduce distortion. Then the sub fills the rest. The sub could be crossed over at 24 db/octave at 100hz, or 12db/octave at 80 hz, or even 6 db/octave at 50 hz, depending on it's response. I have found that worrying where you perceive the source of the sound in the 20-100hz area is inconsequential, as long as there is a nice full sound quality. Anything 24 db/octave and above probably don't make a huge difference as that is a steep slope. 
At lower outputs the midbass can probably sound fine from 50-100hz but at high to medium I start to have problems, it's just not an ideal place to play bass.
Using time alignment speakers at different locations can be overlapped in certain instances if necessary, but probably using the EQ works just as well if not better.


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## sqnut (Dec 24, 2009)

A flat frequency response is another of those forum myths that are blindly followed. If you're chasing a flatish curve, you will never get your car to sound like a 2ch home setup. 

Putting your sub on 50 hz at 6 db LP means 200hz on the acoustic slope is only down 6-8 db, yikes. Yes it will get loud, but it will sound muddy as hell. No amt of eq is going to fix that. Yes you can't locate source of sound in the 20-70hz range. The higher you let the sub play the greater the chances of resonance issues and _that_ will kill your stage presence.


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## Hanatsu (Nov 9, 2010)

sqnut said:


> A flat frequency response is another of those forum myths that are blindly followed. If you're chasing a flatish curve, you will never get your car to sound like a 2ch home setup.
> 
> Putting your sub on 50 hz at 6 db LP means 200hz on the acoustic slope is only down 6-8 db, yikes. Yes it will get loud, but it will sound muddy as hell. No amt of eq is going to fix that. Yes you can't locate source of sound in the 20-70hz range. The higher you let the sub play the greater the chances of resonance issues and _that_ will kill the your stage presence.


^^ 

Shallow slopes will simply cause more issues, that's my experience.


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## Alrojoca (Oct 5, 2012)

Subscribed, good information I most likely need in the future.


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