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Discussion Starter #1
So....I am have been an SPL guy most of my life and as thus have prioritized output over response. I currently run a Hutchison ETA8 in a 4th order. This is a very high quality Neo sub that will handle 1500rms all day. It does low 140s in my Durango but with a sharp roll off under 30 and over 60. The over 60 is not an issue as my 1800.3s will play down there no sweat.

I know I could build a normal ported enclosure tuned low and take care of that roll off. I could also go to a 6th order and gain a flatter response, especially with the 1800.3s ability to dig deep.

I am really looking at more of an SQ-ish build and want to prioritize response over a bandwidth from say 25-60 or so.

What direction should I go on an enclosure? Space is not an issue. And tips on port area or anything else that may help?

Thanks


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So....I am have been an SPL guy most of my life and as thus have prioritized output over response. I currently run a Hutchison ETA8 in a 4th order. This is a very high quality Neo sub that will handle 1500rms all day. It does low 140s in my Durango but with a sharp roll off under 30 and over 60. The over 60 is not an issue as my 1800.3s will play down there no sweat.

I know I could build a normal ported enclosure tuned low and take care of that roll off. I could also go to a 6th order and gain a flatter response, especially with the 1800.3s ability to dig deep.

I am really looking at more of an SQ-ish build and want to prioritize response over a bandwidth from say 25-60 or so.

What direction should I go on an enclosure? Space is not an issue. And tips on port area or anything else that may help?

Thanks


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Low tuned ported helps but from the sub you're using, I actually know a bit about it. I'd want something with a lower fs.
 

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So....I am have been an SPL guy most of my life and as thus have prioritized output over response. I currently run a Hutchison ETA8 in a 4th order. This is a very high quality Neo sub that will handle 1500rms all day. It does low 140s in my Durango but with a sharp roll off under 30 and over 60. The over 60 is not an issue as my 1800.3s will play down there no sweat.

I know I could build a normal ported enclosure tuned low and take care of that roll off. I could also go to a 6th order and gain a flatter response, especially with the 1800.3s ability to dig deep.

I am really looking at more of an SQ-ish build and want to prioritize response over a bandwidth from say 25-60 or so.

What direction should I go on an enclosure? Space is not an issue. And tips on port area or anything else that may help?

Thanks


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Hey Dacheatham. Unfortunately, when it comes to subs. Sq with 4-6th orders isn't really viable. The group delay is just horrendous and is nigh impossible to blend well with the midbass. I'd really focus on bandwidth. Sure your 7in midbass can go down to 60hz (maybe) but probably not at volume, with low distortion, and within excursion, at high volumes.

Simple ported or sealed is your best bet.

Bandwidth>Qtc> SPL.

Imo.

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Discussion Starter #4
Thanks for the thoughts; I definitely agree with much of it.

Can you (or anyone else) recommend a box designer that is more suited to these types of setups? All of the guys I have used either can about how loud the box can burp or how much air it can move at near subsonic frequencies.

QUOTE=Jscoyne2;5721873]Hey Dacheatham. Unfortunately, when it comes to subs. Sq with 4-6th orders isn't really viable. The group delay is just horrendous and is nigh impossible to blend well with the midbass. I'd really focus on bandwidth. Sure your 7in midbass can go down to 60hz (maybe) but probably not at volume, with low distortion, and within excursion, at high volumes.

Simple ported or sealed is your best bet.

Bandwidth>Qtc> SPL.

Imo.

Sent from my XT1710-02 using Tapatalk[/QUOTE]






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Thanks for the thoughts; I definitely agree with much of it.

Can you (or anyone else) recommend a box designer that is more suited to these types of setups? All of the guys I have used either can about how loud the box can burp or how much air it can move at near subsonic frequencies.

QUOTE=Jscoyne2;5721873]Hey Dacheatham. Unfortunately, when it comes to subs. Sq with 4-6th orders isn't really viable. The group delay is just horrendous and is nigh impossible to blend well with the midbass. I'd really focus on bandwidth. Sure your 7in midbass can go down to 60hz (maybe) but probably not at volume, with low distortion, and within excursion, at high volumes.

Simple ported or sealed is your best bet.

Bandwidth>Qtc> SPL.

Imo.

Sent from my XT1710-02 using Tapatalk





Sent from my iPhone using Tapatalk[/QUOTE]Box designer either hunter Martin (ezdb designs) or mark aka caraudiofabricator.com

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Since you are a former bass head you will probably want to go with ported enclosure. Tuning in 30s, make sure you have airtight enclosure, sides in golden rathio (0,62:1:1,62) round port diameter around 4-5 inches, a few damping mats on the interior walls, Foam on at least three sides (below the sub, on one side wall and on the let say back side - this will reduce enclosure ringing. Take care of port placement, which should be for at least of port diameter away from the enclosure walls and behind/in front of the port. Put some braces on enclosure walls and between the top/bottom/side to side of the box. Position braces on the walls asimetric - that way you will get two different areas each with its own resonating frequency.
Next thing is to position enclosure in the trunk in a way it will give you the best output (loading)
put somekind of gasket under the driver to decouple it from enclosure
Use speakon or similar connection posts - dont route cable trough a port
When designing enclosure opt for smooth impedance curve
aim for low air speed trough the port
use aeroport endings - shorten port tube for the 1/2 of height of EACH aeroport ending used to get very close to desired/calculated tuning
put the port on same side as driver is installed
.......
 

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And what EQ profile have you set up for the bass response you want? Hantatsu's house curve makes a great starting point, usually with a nice fat bottom end.


Transient response being what it is, sealed or ported is what I usually end up with.


I'm going to plop your sub in WinISD for a sec and see what's what....
ok so first thing I noticed, the sub doesn't "want" to be in a 4th order at all, it wants ported or 6th order.


Next, I compared the best response plots of this sub that I could against what I consider one of the sweetest subs I've ever owned when it comes to low frequency response vs. the cone size, the Acoustic Elegance AV10H-D2 (yes, my lucky ass still owns one.)



What I found out is this sub is quite peaky by default. I can get acceptable response by drawing out a "bass shelf" design, with a low tune in the 28-30 hz range and fiddling with the box size I can get it reasonably flat. There's still a response peak and trough to work out.

Using a single high-excursion, low cone area sub seems the wrong tool for the job to get where you want to go, efficiently. If you want to use it because its what you got, great go for it and see how it goes. But this sub seems to not fit the ideal SQ standard, without compromises to the response.

...aaaaand while trying to model I managed to divide by zero and piss the program off so I lost my numbers, but you get what I'm trying to say, right?


edit: I got back on, and managed to come up with a decent 6th order, and the response wasn't too bad. The problem is, I don't know if the enclosure is even build-able.



BUT:


rear chamber .124 ft^3

tun freq 54.31 hz


front chamber .819 ft^3
tun freq 25 hz


I got a pretty nice, mellow response that stayed flat within .2 dB or so, with a -3dB down at ~23hz, and again around 72hz



In doing so, the group delay is "ok" but not excellent up to about 32 hz. A ported sub is better from 100hz up to 32hz, but only by a few ms, so maybe not the end of the world. Phase is another matter, as expected. The response is inverted in phase from 60hz down, and slews heavily as the response drops. This is the part that makes me iffy about pursuing an SQ 6th order.



Just a question, since you have a Durango.... ever thought about cutting the bottom out and installing a set of 15-18" Infinite Baffle subs? Not for the faint of heart but it has been done in one (or was it a Grand Cherokee?), and I bet it sounded amazing.
 

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Discussion Starter #9
Thank you very much for all of that. I may need jo just move this sub to my Foxbody, maybe in a ported as it did not model well in a 4th. I can do without great quality in that car as the engine and exhaust trump the sound.

I am anxiously awaiting the SQL12 from Stereo Integrity but have also been eyeing the B2 Audio Reference 12 as it is currently on sale for $250.

And I briefly considered the IB idea after reading your build log but I plan to sell/trade the Durango in late next year so may not be the best idea.



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Thank you very much for all of that. I may need jo just move this sub to my Foxbody, maybe in a ported as it did not model well in a 4th. I can do without great quality in that car as the engine and exhaust trump the sound.

I am anxiously awaiting the SQL12 from Stereo Integrity but have also been eyeing the B2 Audio Reference 12 as it is currently on sale for $250.

And I briefly considered the IB idea after reading your build log but I plan to sell/trade the Durango in late next year so may not be the best idea.



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Skip the b2 crap
 

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Hey Dacheatham. Unfortunately, when it comes to subs. Sq with 4-6th orders isn't really viable. The group delay is just horrendous and is nigh impossible to blend well with the midbass.

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could someone give me an idea of what group delay is and how it affects sound? I ask because I hear about it often and even in some of the box designs I have, it was mentioned. I previously had a 4th order and remember the designer said the group delay was very minimal. I guess I dont know what I would listen for because I have had a few 4th orders and liked the sound. Just sounded like louder sealed to me
 

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could someone give me an idea of what group delay is and how it affects sound? I ask because I hear about it often and even in some of the box designs I have, it was mentioned. I previously had a 4th order and remember the designer said the group delay was very minimal. I guess I dont know what I would listen for because I have had a few 4th orders and liked the sound. Just sounded like louder sealed to me

group delay by itself isn't an issue, its when you consider that delay means to our ears whether something is "in time" or not with whatever else is playing. Different delays at different frequencies can smear the response, and if you're talking about delays in a frequency range where a crossover occurs, then it gets into all sorts of constructive and destructive interference patterns (comb filtering), and that sucks...plus its hard to fix.



If everything was delayed an equal amount, it wouldn't be a factor at all.



Simpler designs (IB, sealed, bass-reflex) usually have more fudge-factor in their designs as well, so getting the intended response is easier. Imagine if the published specs of your sub were off from the real specs by 20%, which is not too far off what we see in real life. That means that more complex 4th and 6th order boxes are also now mis-calibrated by that same factor, and it multiplies. Simple designs can absorb the differences with almost no audible output difference to the listener. Simply put, KISS wins.



A Stereo Integrity SQL 12 sounds absolutely peachy for what you want to do. It should serve you well in a nice ported box. I'd just ask Nick what box specs to set it to, and let it rip.
 

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could someone give me an idea of what group delay is and how it affects sound? I ask because I hear about it often and even in some of the box designs I have, it was mentioned. I previously had a 4th order and remember the designer said the group delay was very minimal. I guess I dont know what I would listen for because I have had a few 4th orders and liked the sound. Just sounded like louder sealed to me
Here are a few threads that might help.
https://www.diymobileaudio.com/forum/technical-advanced-car-audio-discussion/120342-group-delay-whats-really-good.html

https://www.diymobileaudio.com/forum/technical-advanced-car-audio-discussion/328218-what-does-phase-response-group-delay-mean-custom-box.html

https://www.diymobileaudio.com/forum/technical-advanced-car-audio-discussion/161045-ported-enclosure-group-delay-fix.html


Some time ago I stumbled across a "400" rule of thumb (from a presumably reputable source), wherein modeled GD (ms) is multiplied by the corresponding frequency at any point on the graph. A sum of 400 or less at any point above 40 Hz (or was it 30 Hz?) and you're golden ...IIRC, any amount of GD below 40 Hz (or was it 30 Hz?) cannot be heard.
 

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Hey Dacheatham. Unfortunately, when it comes to subs. Sq with 4-6th orders isn't really viable. The group delay is just horrendous and is nigh impossible to blend well with the midbass.
...
This is why those FIR based DSPs, and the DIRAC plug in for miniDSP exist.

It allows the group delay to be EQ'ed out and the nigh impossible become possible.
 

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I'd also want to point out that many of those discussions you were led to were about ported vs sealed. While extremely accurate (especially Andy's assessment, he's a smart guy so best listen IMO), they all eschewed any talk about 4th and 6th order systems. IMO, the cons of a higher group delay and phase inversion right in the middle of the midbass response would be a more topical point of discussion.
 

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I'd also want to point out that many of those discussions you were led to were about ported vs sealed. While extremely accurate (especially Andy's assessment, he's a smart guy so best listen IMO), they all eschewed any talk about 4th and 6th order systems. IMO, the cons of a higher group delay and phase inversion right in the middle of the midbass response would be a more topical point of discussion.
But ^that^ points back to the earlier mention of FIR based DSPs.
And almost all of the historic discussions of sealed versus ported either preceded FIR DSPs or have not included the Phase/group-delay EQ in the mix.

Transient response cannot be helped much comparing a sealed to a Nth order box... however the whole phase/group-delay can be largely EQ'ed out.

So one either goes sealed and a massive amp, or one has a big "spend up" on a DSP and EQing out the group delay.

Then the advantage of the sealed is transient response.
And the advantage of the Nth order is potentially lower distortion and less power.

The cons are power and amplifier cost with sealed, and DSP and tuning with the Nth order and FIR.

As an aside... in a 6th order one can use a passive radiator for the 23/25 Hz end, and that would be the longest and most volume consuming port... so it may help to keep the box from bloating in size.
The rest of the ports need to be tubes to unload at the low frequencies, so they can come out.

The whole topic of whether distortion is bad has been addressed as nasuem, but getting rid of higher order harmonics can help from pulling the sound to where ever the sub is located... so there is a potential sound benefit in higher order boxes... as well as a power consumption benefit.

Basically:
1) I would not think of using a 6th or 8th order without a FIR DSP.
2) If one is using a FIR based DSP, then chin scratching about the higher order boxes seems like something to really take time to consider.
 
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