16 replies to this topic

[eek]

Hi, after completing my stereo three days ago, I've grown to hate it's complexity, weight and impractical dilemmas I face with storage, reduced fuel economy and weird handling characteristics.

Vehicle is a Mercedes C200 sedan, and my plan going forward is to remove everything, construct a fiberglass enclosure in the spare wheel well, and mount the sub in the floor, facing upwards. I currently have a 30L enclosure with the woofer facing directly backwards into the boot lid. It isn't very loud, however seems to be waaay too loose for my liking. Very different from what I expected from a 10" in a sealed enclosure. Doesn't play as low as my old DD2515 in a ported box though

Still planning to construct a sealed enclsoure, as a ported one in a wheel well is too much hassle to get correct. I've punched the TS parameters into WINISD for a looksy, and this is what I have come up with for gain and group delay plots. Any thoughts? I need someone to bounce ideas off.





Any thoughts on the plots? Changes and improvements to be made here?

Considering the fact that I am not building a ported enclosure, I'm not expecting big SPL numbers, but at least a woofer with a bit more dampening/control. From the group delay plots, it seems.....fine, haha. Then again, are there any known issues for firing a sub vertically upwards into the top of your bootlid/parcel shelf?

The area is sound deadened, and I will lose my spare wheel, replacing it with a can of foam So paranoid. I think the second i finish this stereo, I will have a puncture. *touch wood*

[claor]

why are you so against going ported the hassel will be worth it, a sub that nice should go in a ported enclosure,

Wait for DG phil, to post, he will help you out,

jason

[eek]

claor, on May 6 2009, 11:33 AM, said:

why are you so against going ported the hassel will be worth it, a sub that nice should go in a ported enclosure,

Wait for DG phil, to post, he will help you out,

jason

Well, getting the volume correct when building a fiberglass enclosure in the spare wheel well is difficult. Too much fussing around for my liking. When you have to factor a port, it's length, cross sectional area and volume discplacement of woofer and port............I don't think it's worth the hassle I know, a well designed ported box will give me a similar response to a sealed box, with the benefit of slightly efficiency, but eh...gotta weigh up the effort required to design and construct against the results. Oh, and a port in the boot floor just means stuff will fall in.

My box was constructed out of 32mm MDF, I will need to use it again to create the baffle for the spare wheel well box...or the sub may fall through, since it weighs about 30kgs.

[br85]

How do you plan to get the sound into the cabin? If it's having trouble coming through the back seats now, I'll bet that's the number 1 cause of the "looseness" you're experiencing.

[DG Phil]

What year model is the woofer?

[claor]

i tried to find out the same thing
there must have been only very few XXX 10's ever made,

[DG Phil]

XXX10s were available pre '08 before RE changed to the new custom basket and went 12, 15 and 18" only.

[eek]

DG Phil, on May 6 2009, 09:30 PM, said:

XXX10s were available pre '08 before RE changed to the new custom basket and went 12, 15 and 18" only.

Phil, yes, I think it's from '04 or '06, definitely not the current range that are available. I have the specs of the woofer on the screen captures in my first post.

As for the 'looseness' of the sound, I believe it could be caused by the fact that the cabin is quite well sealed off from the boot area. There are a few holes and gaps here and there between the cabin and boot, though nothing substantial, it's not air-tight by any means. I am hoping if I remove the parcel shelf speakers, it will help my cause.

Any thoughts on the winisd plot?

[data_mine]

Sticking it in a ported box is well worth the effort. As plotted by you, the -3db cut off is over 50Hz, no good for SQ at all.

Ported in the same size (25L as you specified), you can get it down to 28Hz. Much better. Ideal ported size is only 19L too.

I'd make that effort for the significant extra low end reproduction.

[DG Phil]

eek, on May 6 2009, 09:48 PM, said:

As for the 'looseness' of the sound

The box is under-damped, Qtc of 0.53 is too low for my liking. For sealed boxes in car, I normally aim for over the "magic" .707

[~Spyne~]

Quote

Qtc around 1.0 is fine

is about right, isn't it Phil?

[DG Phil]

~Spyne~, on May 7 2009, 09:14 AM, said:

is about right, isn't it Phil?

For me yes, but it's all down to personal preference.

[eek]

Okay, so I did a quick little spreadsheet to calculate QTC. Considering the magical 0.707 seems to work. Using goalseek in excel, I've now come up with a net volume of 14.84L, which yields a 0.707 QTC.

Putting these values into WinISD, and come up with the following curve



Should I be concerned with the group delay chart?



Response looks quite linear to me, except for a tiny peak at around 50Hz. Other than that, if it can do down to 32Hz, then I'm happy with it. It's only a 10" after all.

Also, what's the G-O with the vents? I seem to need really LONG vents, if I am to have a cross sectional area with a low vent mach. Is there something wrong here?

[Luke352]

The above response will end up with a massive peak around 50hz due to cabin gain and to me that group delay looks horrid. Whereas your first response image you posted in your first post would actually work better in car as with cabin gain you'll end up with a much smoother response. I'll put it like this an IDMAX which is highly regarded as a very nice SQ woofer with great low end ability has an F3 of 52hz vs your XXX having an F3 of about 57hz, but down at 30hz the RE is only 8db down vs the IDMAX being 10db down.

People get all worried about needing a low F3 when in reality it isn't necessary, anywhere between 50 and 60hz in a sealed enclosure is actually ideal for in car use. What is important is the roll off, a nice shallow roll off is what you want which is why with a F3 in the 50's to 60hz range combined with a shallow roll off will give excellant in car response, obviously though a 55hz F3 with steep roll off isn't going to work, but this is uncommon with most good subs.

My JBL W Gti has an F3 of about 42hz and it has a large peak around 50hz which i've had to EQ out, but the low end response is excellant in car it's flat to 25hz, which is due to the very shallow roll off, and that is with a Qtc of .936

[eek]

Luke352, on May 7 2009, 09:55 PM, said:

The above response will end up with a massive peak around 50hz due to cabin gain and to me that group delay looks horrid. Whereas your first response image you posted in your first post would actually work better in car as with cabin gain you'll end up with a much smoother response. I'll put it like this an IDMAX which is highly regarded as a very nice SQ woofer with great low end ability has an F3 of 52hz vs your XXX having an F3 of about 57hz, but down at 30hz the RE is only 8db down vs the IDMAX being 10db down.

People get all worried about needing a low F3 when in reality it isn't necessary, anywhere between 50 and 60hz in a sealed enclosure is actually ideal for in car use. What is important is the roll off, a nice shallow roll off is what you want which is why with a F3 in the 50's to 60hz range combined with a shallow roll off will give excellant in car response, obviously though a 55hz F3 with steep roll off isn't going to work, but this is uncommon with most good subs.

My JBL W Gti has an F3 of about 42hz and it has a large peak around 50hz which i've had to EQ out, but the low end response is excellant in car it's flat to 25hz, which is due to the very shallow roll off, and that is with a Qtc of .936

Hi,

Few mixed opinions in this thread already. So it seems like if it was in a vented enclosure, due to cabin gain, the response would be somewhat peaky at approximately 50Hz. This isn't something winISD can pick up. In addition, the group delay looks a bit intense for my liking as well.

So I think it's back to the sealed enclosure design. On the topic of dampening, in a 9L enclosure, QTC is 0.7217, and in a 11L enclosure, 0.678. Is the general consensus here that I should keep this value quite high, preferrably over the 0.707 figure?

Yellow is in a 11L enclosure
Orange is in 9.5L enclosure
Green was the ported enclosure as mentioned before



I think the 9.5L (orange) plot drops slightly steeper around the 50-60hz range compared to the 11L (yellow).

Group delay looks much better in the sealed enclosures



So what do you think the conclusion is boys? Go with the 9.5L sealed enclsoure?