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Old 23rd November 2012, 02:20 PM   #1
djn is offline djn  United States
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Default What do you think if this driver???

I have two 2 cu ft cabs and two 300w plate amps and always figured drivers would come my way at some point in time. Well, I was at a friends house last weekend and he asked if I want two speakers. I assumed he meant speakers in cabs but instead he handed me to JBL GT1041D sub drivers new in the box.

They are car subs so I assumed they might not work in a home system. I did a WinISD this morning and found that they actually might work very well. Here is a screen shot of the Win results and the PDF for the drivers.

Your thoughts???
Attached Images
File Type: png JBL GT1041.png (104.6 KB, 162 views)
Attached Files
File Type: pdf JBL GT1041D PDF.pdf (101.7 KB, 35 views)
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Old 23rd November 2012, 04:21 PM   #2
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Those JBL GTO Drivers are nice !!
Some always say they won't do well but I see no reason why they wouldn't.
I have been wanting to get some of those in the 12" size.

What does the group delay curve look like?

jer
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Old 23rd November 2012, 04:32 PM   #3
djn is offline djn  United States
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Hi Jer. Here is a screen shot of the group delay taken from the PDF. I have heard the term Group Delay many many times but never paid attention to what it means. What does it mean and what is the affect???
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File Type: png GT1041 Group Delay.png (52.6 KB, 148 views)
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Old 23rd November 2012, 05:49 PM   #4
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If the Group delay gets to high it can give the low end a muddy or slow as some put it kind of sound.
I don't know exactly how low is good.

But, I typically shoot for 1/2 to 1/4 or lower ms than what the peak frequency is as long is it doesn't hurt my target lowest frequency much.
For 30HZ is 33ms so I try to get below 15ms to 7.5ms as long as the frequency response doesn't hurt to much at this end of the scale.
This is a very hard decision and requires a lot of compromise.

But you can also consider room gain to help compromise for the drop.

I built my 8" subs (optimus CWS-PRO800) in a small .67cu' box like a sealed but then I added a port tuned very low at bout 22Hz to 25Hz.
This added about 2db or so bump/shelve to the extreme low end compared to that of a sealed box.
In my car with the cabin gain this flattened out the response quite nicely and a pair of them really rocked
The bass was nice and tight with no boominess at all.
Kick drums and toms were Awesome!

Later on I used that same sub in my room with my little ESL panel and it matched up perfectly with it as well.
I tried that same little panel with various commercial Hi-Fi cabinets that I have around the house and they didn't match up well.
Including my little Sony 5 1/4" speakers until I sealed up the port and then the melded as one, I couldn't believe it.

Some like the sound of ported boxes and I used too back in the day when good deep bass was hard to come by.
Lately I am liking more the transient response that sealed box or what a small low tuned box has to offer.
Sort of like the dampening that TL's can offer as well, although I have yet to try one out.
Lately I have been studying up on the Aperiodic enclosures as well.

What Roger Sanders said in his paper made a lot of sense to me and I relate this to my own findings,

An Interview with Roger Sanders of Sanders Sound Systems - The Columns - Dagogo

It is always the subject of having a deep and low bass extension but for what cost when it comes to music?

In the plot you had posted by tuning it a bit lower you can reduce the group delay quite considerably to about 10ms at 40 hz and this might bring the peak of the curve at about 25hz to 30hz.

I will enter the data into Winlsd and check it out later tonight.
But I definitely think that you can have a really decent sub system with those drivers.

It had been quite a while since I have looked at the JBL website but these kinda caught my eye as impressive yet affordable as well,

GT5-12 | 12? single voice coil subwoofer | JBL US

this has a higher power handling as it cost more,

GTO1214 | 12? die-cast, 4-ohm voice coil subwoofer | JBL US

I think you scored a pair of really nice drivers there !!!


Cheers !!!

jer
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Old 23rd November 2012, 05:57 PM   #5
djn is offline djn  United States
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Thank Jer. Those two drivers look good. The GT5 looks like a great deal as a matter of fact.

I will take time tonight to read that interview.
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Old 24th November 2012, 05:10 AM   #6
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I was Messing with Winlsd and I must say that driver models nicely.
Here is what I have with it modeled in a 2 cubic foot ported box at 22.4Hz and 200 watts.
The port is set at a conservative 3.23" dia. and is 18.71" long as this would just fit in a box with 1' X 1' X 2' internal dimensions.

105 db at 20Hz and 110 db at 80Hz that is about a 2.5 db per octave slope....Nice !!!

It works nicely in a range of about 1.5 to 3 cubic feet for a ported and 1 cubic foot for a sealed.

Four of those would suit me very well as I do need to start building a new bass system soon.
My old drivers have now seen their better days...He,he,he,he!!!

Enjoy !!!

jer
Attached Images
File Type: jpg Box and Full Power SPL's.jpg (77.6 KB, 118 views)
File Type: jpg Transfer Function.jpg (93.0 KB, 114 views)
File Type: jpg Excursion.jpg (85.8 KB, 110 views)
File Type: jpg Group Delay.jpg (78.8 KB, 7 views)
File Type: jpg Vent.jpg (72.1 KB, 8 views)
File Type: jpg Port Velocity.jpg (83.1 KB, 7 views)

Last edited by geraldfryjr; 24th November 2012 at 05:22 AM.
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Old 24th November 2012, 01:12 PM   #7
djn is offline djn  United States
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Nice work Jer! Yep, It does model well and the are not really expensive either. I did notice that on my WinISD, it is a very flat line but on yours it is more of a hump. Did I not add something in the parameters that I should have?
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Old 24th November 2012, 02:15 PM   #8
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The slight drop is caused by a lower tuning in order to lower the group delay to 12ms at 30Hz.

Here is a comparison of three different tunings,
Winlsd's optimised= blue

My tuning = yellow

My tuning flat= orange

I should have added JBL's tuning for comparison as well.

The drop in response will be compensated by room gain and most likely will be quite flat when measured in the room if not a slight boost depending on the size of your room and its loss factor.

You can also have a more flatter response by increasing the box slightly to 2.3 cubic feet tuned to 27.5 Hz with an added .33 ohm series resistor as shown in the last two pictures in green.
This also raises the group delay considerably as well,almost double at 22.974ms !!
Remember that at 30hz a 33ms of group delay is a full wavelength of delay !!



jer

P.S all of the simulations are for the JBL GT-1041D that you originally posted and not the GT5.
Attached Images
File Type: jpg Transfer Function and ports.jpg (102.8 KB, 5 views)
File Type: jpg SPL's at 200watts.jpg (91.3 KB, 5 views)
File Type: jpg Group Delay 2.jpg (94.4 KB, 4 views)
File Type: jpg Transfer Function 3.jpg (118.4 KB, 6 views)
File Type: jpg Group Delay 3.jpg (103.7 KB, 6 views)

Last edited by geraldfryjr; 24th November 2012 at 02:24 PM.
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Old 24th November 2012, 02:35 PM   #9
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Quote:
Originally Posted by djn View Post
They are car subs so I assumed they might not work in a home system. I did a WinISD this morning and found that they actually might work very well. Here is a screen shot of the Win results and the PDF for the drivers.

Your thoughts???
I have a pair of these JBL GT1041D. I must say they are one of the best 10" "car" subs that work well for home hifi. Tested them in 25 Liters (0.9 cu ft) ported boxes. Great dynamic/punchy mid-bass. They do go down low too, so low bass is not a problem.

Quote:
Originally Posted by geraldfryjr View Post
It is always the subject of having a deep and low bass extension but for what cost when it comes to music?
It's always difficult to get the right balance. Often times, we get too caught up with either low bass extension or lowest F3. After building the speakers, we find that they sound lifeless. That's due to the lack of mid-bass. Nowadays, I would rather sacrifice a little bit of low bass in exchange for superior mid-bass.

Regards
Mike
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File Type: jpg GT1041D_25L.jpg (82.9 KB, 12 views)
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Old 24th November 2012, 02:42 PM   #10
18Hurts is offline 18Hurts  United States
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I like the JBL GTO series

Have a 12" version, the 1214 loaded in a 2.9 cubic foot box and a 18" passive radiator tuned to 22 Hz. It is not for music but corner loaded for the home theater.

Works well in a sealed box in the car and folks build 18Hz tuned tapped horns with them.
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