JBL GTO sub bass project

[JBL 4645]

Well after the chit chat on the (stereo sub bass) I looked at two nominees at Halfords which is the nearest placed to buy some JBL car audio. Well it’s not going in to be used for (vroom, vroom car) its going in, my living room, end of story.

I’ll try it out later to see how it fairs (yes in the Eltax enclosure) I’ll run a few frequency response sweeps to see where it stands.

I’ll have to start buy buying as many and at £49.00 I’m not complaining.

pdf brief description on the GTO series
http://www.convoy.com.au/downloads/product-files/Owners%20Manual%20-%20GTO1002D_a9d2.pdf

I plan to get as many as possible within reasonable limits. I don’t want to have to climb over speaker enclosures to get to the sofa.

[JBL 4645]

Sooty was sniffing the new JBL for 5 paw approval. Maybe he should be sniffer cat at airport security.:D

[JBL 4645]

(It won’t fit) :D the basket is the wrong shape no mater, I’ll wait and wait and get few more, and get some boxes knocked up. I flipped it upside down it’s slightly wider by a few extra (mm) millimetres.

Well I have the specifications

12"(305mm)

Cut-out diameter
11-3/16” (284mm)

Outer diameter
12-7/16” (316mm)

[JBL 4645]

I kinder cheated with towel :D (looks like something out of Total Recall “wrap wet towel around your head”) LOL and (few dust cloths) tucked around the inside of the basket to give it a near close sealing with the enclosure. A bit impractical and risky but I managed to get this frequency response at the front of the room.

Similar issues of nulls at seating location it’s the right front that is good for certain frequencies and lousy for other frequencies.

If I had placed it on left side of the room it would be different and same goes for rear right corner or along the rear wall it beefs up the 50Hz to 60Hz range

If I get few boxes made to size to give optimum maximum performance I’d be happy with that.

I did notice the slight rise in the 40 to 50Hz range as well 90 to 100Hz range. I guess if the seal is 100% it would be bit tighter in the lower 20 to 40Hz range. Well I can hang on there’s no rush.

[JBL 4645]

Well the “nulls” can be seen (or gaps between) the in-room frequency response (SPL db metre placed on the sofa) a scene from Star Trek “Balance of Terror” where the space station gets blown to “kingdom come” has few good lows. The lows shown here is left and right front sent to sub though the mixer the centre low end is less on the Dolby5.1 mix. The LFE.1 track doesn’t cut in till later on in the show and is only used now and then to add extended low end jolt.


I could plot the room out with the Eltax loaded back in its enclosure and test each and ever single 15” square box size along the sidewalls front and rear wall to get a rough guess where the strongest areas are and weaker spots. Wow that will take up whole day of testing.

[JBL 4645]

I’ll pick up another GTO1202D tomorrow and store it till I have around x16 of them, to start the project next year.

[JBL 4645]

I’ve just momentarily picked up a second JBL GTO1202D only x14 more to go now.

The guy in the store told me they need to order more in. “How many do you need?” (About x14 more) :p “16!”

[pos]

Crazy project you have here! 16 subs!
How are you going to amplify them?
With so many woofers, and the EQ gears you have, I would not worry too much about box tuning, and just put them in small sealed boxes spread around the room (and also at different heighs) to counter room modes problems (that clearly show in your measuremets)

With that many subs (and providing you have enough amplifier power), you do not even need to have separate eq per sub: the frequency response is likely to be quite smooth. Just make sure everything is wired as it should (global Re, and polarity), measure, eq, and you are good to go!

But are you really planning on installing 16 of these subs?

[JBL 4645]

Crazy project you have here! 16 subs!
How are you going to amplify them?
With so many woofers, and the EQ gears you have, I would not worry too much about box tuning, and just put them in small sealed boxes spread around the room (and also at different heighs) to counter room modes problems (that clearly show in your measuremets)

With that many subs (and providing you have enough amplifier power), you do not even need to have separate eq per sub: the frequency response is likely to be quite smooth. Just make sure everything is wired as it should (global Re, and polarity), measure, eq, and you are good to go!

But are you really planning on installing 16 of these subs?

Evening pos

What can I say the room is bitch! LOL She is life sucking frequency null in certain spots and I just want to cut around that once and for all without ever having to hump sub boxes around.

No they will get a stereo amp for each few pairs per side left and right stereo channel of the amp.

So hopefully I get away with four stereo amps.

Yes, it is crazy LOL but I’d sooner have a sane smooth frequency response rather than going crazy mucking around with a single sub to find the best place in the room.

So you would say (sealed) rather than ported then!

Can you enter the T-S-P into the Win program because there is some parts of the specifications that are not listed on the link here that was required and I think I might have miscalculated the data entered.

Stuff the link I can’t find the specifications! Here’s the T-S-P from the spec sheet I have.

Diameter: 12” (305mm)
Sensitivity: 93db
Power handling: 300wRMS 1200Wpeak
Frequency response: 23 – 400 Hz
Normal impedance: 1 or 4 ohms
Voice-coil diameter: 2.0” (51.0mm)

Dimensions:
Mounting depth 5-1/6” (129mm)

Cut-out diameter
11-3/16” (284mm)

Outer diameter
12-7/16” (316mm)


Voice coil Dc Resistance Revc: (ohms) 1.00
Voice coil inductance: @1 kHz: Levc (mH) 0.71
Driver radiator area: Sd (in2) 82.46
Sd (M2) 532.00

Motor force factor: Bl (tm) 7.71
Compliance volume: Vas (FT3) 3.45
Vas (litters) 97.80

Suspension complianc: Cms (um/N) 242.00
Moving mass, air load: Mms (grams) 189.00
Moving mass, diaphragm Mmd (grams) 182.00

Free-air resonance: Fs (Hz) 23.50
Mechanical Q: Qms 7.14
Electrical Q: Qes 0.47
Total Q: Qts 0.44

Magnet-gap height: Hag (in) 3/8
Hag (mm) 9.00

Voice-coil height: Hvc (mm) 9.00
Hvc (in) 1-5/16
Hvc (mm)34

Maximum excursion Xmax (in) 1/2
Xmax (mm) 12.50


I’ve looked and looked I just can’t find where the specification sheet is hiding?

Cheers pos :)

[pos]

something between 40L (Qtc 0.8) and 60L (Qtc 0.7) will be good. You will have to eq anyway.

with 18mm walls a 40L box could measure 59x38x25cm (winISD's optimum ratio, but any ratio will do for such a small box used as a sub)

Will 16 of these fit into your room? :eek:
That's almost 1 cu meter in total with exterior dimensions!

[JBL 4645]

something between 40L (Qtc 0.8) and 60L (Qtc 0.7) will be good. You will have to eq anyway.

with 18mm walls a 40L box could measure 59x38x25cm (winISD's optimum ratio, but any ratio will do for such a small box used as a sub)

Will 16 of these fit into your room? :eek:
That's almost 1 cu meter in total with exterior dimensions!

Cheers on the feedback pos

LOL I guess that now depends on the size of the enclosures doesn’t it!?

Yeah I’ve kinder over looked that fact! LOL The smaller Eltax A12R sub is 15” square and if a box of that size will suit these JBL GTO 1202D, then so be it 15” square I can get 16 in easily along the sidewalls front and back walls.

I’m not looking for high over the top SPL db that ruptures the ear drum! I’m just after an even-smooth frequency response that can play at sensible SPL db levels.

Oh, bugger cm you guys work in cm I need to convert that to inches?

I’ll go to a calculator conversion for the size-up.

I was going to buy car Hi-Fi box today and the JBL GTO1202D didn’t fit it was out by at least 5mm on the cut-out hole on the box. No I don’t fancy sanding it down LOL.

[JBL 4645]

pos

I assume that is the order for height length and depth?

H 59 centimeter = 23.228 346 457 inch
W 38 centimeter = 14.960 629 921 inch
D 25 centimeter = 9.842 519 685 inch

I don’t want to mess this up!

So you strongly think that sealed will be the best option here as I read in the owners manual JBL advised that sealed will be good without too much trade offs in the lower octave below 40Hz.

How many enclosures can I get out of a 4x8 18”mm sheet of MDF?

So go for rectangular shape that sounds good because the depth will take up less floor space, it’s the height that I’d have to get used to.

Room size is
15 feet length
10 feet 4” wide
7 feet 8” high

[pos]

15"x15"x15" is 40L with 18mm walls (don't know how many quarter of which finger that will end up to be in your strange unit system ;)).

I am not sure this dirver will be ok if facing down, like your eltax sub.

[pos]

Sealed is the best option here.
Any shape will be ok, as long as it is 40L, or around 55L exterior with 18mm walls.

Are you going to build the boxes yourself?
With that many subs calculating the dimensions to maximize your MDF sheets is a good idea indeed!

[JBL 4645]

pos

Oh, I’ll ask the chap at the timber yard how many sheets I can get out of it. As long as I have rough size that’s good enough.

(I’m guessing I can get x2 boxes out of 4x8 sheet of MFD at specific cut size.)

I think it was 2 sheets for the other JBL diy box, 13 years ago. The cost was around £45.00 for the MDF. V.A.T might have gone up a few bob since the budget this year!

The Etax sub is, on its side it fires outwards into the room. So the JBL will be facing front and forwards!

Can I take the size up a few litters and how badly will that affect the performance?

You know I have “Images” JMJ playing only on the L/R stereo only no sub bass turned on and I can hear the engine of the bus across the road at 35Hz! It smoothly blends in with humming, humming sound!

Anyway what of taking the litter size up a tiny notch is your formula sound!

I might just play it by ear and see how it progresses over the time if I can see a rapid improvement in frequency response smoothness and can do it for less than x16 then so be it, x2 won’t get near x4 might start to see some progress, maybe? It’s an odd room to sort out!

[JBL 4645]

Sealed is the best option here.
Any shape will be ok, as long as it is 40L, or around 55L exterior with 18mm walls.

Are you going to build the boxes yourself?
With that many subs calculating the dimensions to maximize your MDF sheets is a good idea indeed!

pos

Sigh I guess I’ll have too! The timber yard might charge twice the amount the build. I think even for hole cut they charge not sure if its £5.00 or 20.00 pounds with the (router drill bit), so I have to phone before going down to the yard and find out what the hole size cuts cost.

I’ll make the box myself with timber battens placed around the inside and countersink the holes on the outside, glue and screw it up tight and run some extra sealant around the inside to make sure it’s (air-tight).


Also the GTO is fitted with (Parallel or Series connections)

Which is the best option to get two GTO to run at 4 ohm load because I don’t think the Alesis RA500 which I plan to get might not like what it sees as its rated down at 4 ohms, I don’t want to start causing (popping sounds) because its been ran in the wrong order of wiring.

I would like to run a single amp on each sub but the cost of the amps will be skyrocketing in cost! Plus I have to get another DCX2496 to add the crossover slopes and few LP filter added.

[Ruediger]

In Thiele's paper there is alignment #10, a B5 alignment: f3/fs = 1.0, Vas/Vab = 1.0, Qt = 0.447.

That means: f3 = fs = 23.5 Hz, Vab = Vas = 98 liter.

You need a passive filter as well. See the Thiele paper. It is in the "General Audio Discussions" forum here at Lansing Heritage in the "Technical References" thread.

Ruediger

[pos]

Try not to go much smaller than 40L. On the other hand you can go larger without problem.

[pos]

In Thiele's paper there is alignment #10, a B5 alignment: f3/fs = 1.0, Vas/Vab = 1.0, Qt = 0.447.

That means: f3 = fs = 23.5 Hz, Vab = Vas = 98 liter.

You need a passive filter as well. See the Thiele paper. It is in the "General Audio Discussions" forum here at Lansing Heritage in the "Technical References" thread.

Ruediger
That means a box more than twice the size of the sealed one, plus dealing with the vent...
The sealed box is the easy option, very forgiving with errors in box size, and predicatable in load to the amplifier, and in excursion. With 8 or 16 subs to build, mainly with the goal of smoothing the response across the room (and not max SPL), the sealed option looks like the way to go IMHO.

[JBL 4645]

Cheers pos / Ruediger ;)

Okay I’ll keep to those the perimeters.

Just been chatting to my dad about how many cuts I can get out of 4x8 sheet.

I need to get the MDF sheet cut in half and then get the rest of the cuts out of it as the saw is most likely 4mm thick and most the cut sized MDF won’t be at the same size. I guess this why it took my friend so long to do the other sub bass box it was mostly sanding it down to shape the box.

Roughly where do you see the (excursion) occurring at, what frequency? Not that it worries me I doubt I’d be running it at Earthquake levels! LOL It would take a lot of subs to do that to make the town rumble!

I have the Crown power calculator that shows me how much is required for given distance at 85db.

Every time I run the other JBL sub and due to room nulls dips and peaks from its location to sofa, at times its running far too high which sends the neighbours barking mad! LOL Well it can’t worse than listening to dog barking for some 12 hours none-stop in the day!:banghead:

It’s when I’m playing a certain part of the low end frequency under or around +100dbc I get an polite knock on the door.:D

So I’ve got more frequency SPL db at the front corner of the room and less of it is reaching the sofa at given distance away! Therefore I have to push it many db higher for the frequency loss! So more subs around the room will require less power yet they might producer purer stronger tones at less power!

[pos]

with sealed boxes you do not have to worry about excursion that much. The driver are never unloaded like in a reflex box under the tuning frequency. You will simply have an increasing excursion as you go lower in frequency (4 times the excursion when going 1 octave lower, if you eq to get a constant SPL at all frequencies).
You will most probably be limited by your amplifier.

You better buy a multimeter to test your wiring (Re), because with 16 dual coil woofers you better knwo what you are doing when plugin something into your amplifier (don't knwo if the alesis has good protections).
Also a battery to test polarity (one woofer out of phase will be difficult to notice)

[JBL 4645]

pos cheers for the resonances. :)

That’s more or less what I read somewhere a few days ago about (air compression) or the box being tighter seal the cone when pressing on it is stiffer rather than having bit of flex.

Okay so sealed it is. I’ll call up tomorrow and get an estimate on the size cuts and the hole cut out.

Oh, I’m not replacing the other JBL sub that still stays!

Oh yes good point tip I’ll check with 1.5v battery to make sure.

I have an analogue volt meter.

The Alesis are rated 4 to 8 ohms.

The JBL GTO 1202D are rated 1 to 4 ohm

I read that is a way of wiring the 4 ohms speakers to give an 8 ohm resistance?

I’ve hardly used the volt meter it has X1K and X10 which setting should I select?

I see the green scale on the volt meter that runs from 0 ohm to 200 ohm it’s not a good picture I’m afraid. Its a KINZO 18D265

I’m afraid I agree about the EQ and limiting the amps power but I hope it needs less if I can get smoothness as even as possible with less demand from the PEQ (parametric) that will be good, but I’ll have to see how each one progresses I might run into a few snags or difficulties.

[Ruediger]

I wasn't aware of the low impedance of these speakers. Wiring them in series has a bad influence on the resulting Qt. Forget about the Thiele alignment. Or get an amp which can handle 1 Ohm loads.

Ruediger

[JBL 4645]

I wasn't aware of the low impedance of these speakers. Wiring them in series has a bad influence on the resulting Qt. Forget about the Thiele alignment. Or get an amp which can handle 1 Ohm loads.

Ruediger

When I stuffed into the Eltax sub and warped a towel around the edges to make it tight as possible it played without any issues (that is without any issues that I couldn’t see).

A 1 ohm amp, I wonder how much that will cost?

[JBL 4645]

I almost I almost forgot about the terminal plate for the back of the loudspeaker!

I’ll get these

http://www.maplin.co.uk/module.aspx?TabID=1&criteria=usb&ModuleNo=1086&C=SO&U=Strat15
http://images.maplin.co.uk/300/jk18u_new.jpg
Loudspeaker Lever Terminals
only £1.49

Then again these for tighter grip!!

http://www.maplin.co.uk/Module.aspx?ModuleNo=1077
http://images.maplin.co.uk/300/jk24b.jpg
Twin Terminal Post
only £3.39

I’m not really fused about which ones, but on budget the spring load terminal plate will be bit flatter and I get it near to the wall.

I’ve got to make a few trips now!!

[Hoerninger]

A 1 ohm amp, I wonder how much that will cost?
It might be a choice to buy 16 pieces of 50 Watt amp kits with one sufficient power supply.
>What is the intension of your project :confused:
___________
Peter

[JBL 4645]

Morning Peter

I’ve got to make a few trips!

I was just doing the size up and about to pop out. The intention is nuclear meltdown! :p just kidding. Car amps will do it! But need transform to run them and the cost I can see it being enormous!

There has to be cheaper means around this, there has to be?

See you in jiffy

[hjames]

Of course, if you need a a bunch of 50 watt amps, you could look for an Adcom GFA-2535.
Its got 4 channels at 60w/ch. Plus, one pair can be bridged to roughly 150w ... so its versatile.
I've got one of those for my 2 surrounds and center - its a good amp with a good sound.
Get a pair of those and you have 8 channels at 60w/ch - if you wanted 50w/ch, 60 will certainly do!


I know Rotel made some 5 channel amps of about the same wattage for home theatre use ...

There are others, but those are good quality, yet old enough to be reasonable priced on the used market.

But if brand and quality isn't important, there are a lot more possibilities.:D

[Hoerninger]

The intention is nuclear meltdown!

See you in jiffy
War with some neighbours? :hmm:
Und tschüß :)
____________
Peter

[Ruediger]

I checked the description on the net (www.jbl.com). The 1202D is a Dual-2-Ohm-Voice-Coil Subwoofer with an impedance of either 4 Ohm or 1 Ohm, depending on the wiring. So no problems.

Ruediger

[JBL 4645]

Ruediger / Hoerninger / Heather

I’ve just got back from the day of spending most of it around a friends while we went down to the harbour so that he can jet-ski and release tension!

I later had some Mulled Wine for the first that time that his girlfriend made WOW best delicious drink I’ve tasted in years!

We spoke about the design of enclosure and he thinks that I should go with (ported) and even another friend agrees (ported).

He has agreed to make the cuts on the enclosure including the cut out for the driver and the terminal plate which I managed to buy x2 yesterday, as its now today Saturday!

I had to travel all over town to get a pair of spring load terminal plates.


I checked the description on the net (www.jbl.com). The 1202D is a Dual-2-Ohm-Voice-Coil Subwoofer with an impedance of either 4 Ohm or 1 Ohm, depending on the wiring. So no problems.

Ruediger

Also the wiring of the speakers should be series to give a 4 ohm load that will work with an Alesis RA500.

He’s a fully qualified teacher in electronics and explained why the low resistance of 2 ohms, (so no I won’t be playing it insane levels).

There was talk on how the box should be done with the pieces to hide as much of the rough edges as possible.

So the thing is, I can get x2 enclosures out of 4x8 MDF 18mm sounds good.

The thing I need to know pos is the volume size with ported and tuned to give the lowest loudness. What would be the optimum lowest best point for the JBL GTO 1202D?

wow that Mulled wine was sure taste when warmed up with all the fruit and stuff WOW what a day.


War with some neighbours? :hmm:
Und tschüß :)
____________
Peter

Peter no war with the neighbours. Least not with the ground floor one! The neighbour below me has more hassles with the ground floor neighbour now because he’s fucking hamming on the walls at 1am!



Of coure, if you need a a bunch of 50 watt amps, you could look for an Adcom GFA-2535.
Its got 4 channels at 60w/ch. Plus, one pair can be bridged to roughly 150w ... so its versatile.

I know Rotel made some 5 channel amps of about the same wattage for home theatre use ...

There are others, but those are good quality, yet old enough to be reasonable priced on the used market.

But if brand and quality isn't important, there are a lot more possibilities.:D

I think I know the one your talking about it. I saw a model around late 90’s that had 5 channels but the output was rather low.

[pos]

Have your friend entered the T/S values for this particular driver? Some drivers are made for closed box.

WinISD wants 130L and a 21Hz port.
80L, 20Hz still looks acceptable. You will also have to add the volume taken by the port (depends on the size you choose).
With this ported design you gain ~4db from 20 to 40 Hz, but you have to add a high pass under 20Hz to protect the driver where the box does not. Group delay is already quite high (32ms at LF), and this will be higher with the high pass.

With this ported design you can use half the numlber of boxes you planned to use witht the closed deisgn, and get almost the same SPL.

But:
- the box is twice the size
- construction is more complex (albeit not twice more)
- you will have huge group delay
- you will have to add a high pass filter
- you will have less spacial smoothing than with twice the number of subs
- any mistake in the box construction (walls dimensions, filling, port size, etc.) will change the response in a much more severe way than with a closed box (much more forgiving)

All and all, I would stick with a sealed design if I were you, given SPL is not you primary objective, but that's just me and ported designs, when carefully executed, sure have their advantages

[JBL 4645]

Have your friend entered the T/S values for this particular driver? Some drivers are made for closed box.

WinISD wants 130L and a 21Hz port.
80L, 20Hz still looks acceptable. You will also have to add the volume taken by the port (depends on the size you choose).
With this ported design you gain ~4db from 20 to 40 Hz, but you have to add a high pass under 20Hz to protect the driver where the box does not. Group delay is already quite high (32ms at LF), and this will be higher with the high pass.

With this ported design you can use half the numlber of boxes you planned to use witht the closed deisgn, and get almost the same SPL.

But:
- the box is twice the size
- construction is more complex (albeit not twice more)
- you will have huge group delay
- you will have to add a high pass filter
- you will have less spacial smoothing than with twice the number of subs
- any mistake in the box construction (walls dimensions, filling, port size, etc.) will change the response in a much more severe way than with a closed box (much more forgiving)

All and all, I would stick with a sealed design if I were you, given SPL is not you primary objective, but that's just me and ported designs, when carefully executed, sure have their advantages

Morning pos

Do you have the correct T-S-P details that should be entered into WinISD as I’m unsure about a few and was mealy guessing on, the ones circled in red.

Diameter: 12” (305mm)
Sensitivity: 93db
Power handling: 300wRMS 1200Wpeak
Frequency response: 23 – 400 Hz
Normal impedance: 1 or 4 ohms
Voice-coil diameter: 2.0” (51.0mm)

Dimensions:
Mounting depth 5-1/6” (129mm)

Cut-out diameter
11-3/16” (284mm)

Outer diameter
12-7/16” (316mm)


Voice coil Dc Resistance Revc: (ohms) 1.00
Voice coil inductance: @1 kHz: Levc (mH) 0.71
Driver radiator area: Sd (in2) 82.46
Sd (M2) 532.00

Motor force factor: Bl (tm) 7.71
Compliance volume: Vas (FT3) 3.45
Vas (litters) 97.80

Suspension complianc: Cms (um/N) 242.00
Moving mass, air load: Mms (grams) 189.00
Moving mass, diaphragm Mmd (grams) 182.00

Free-air resonance: Fs (Hz) 23.50
Mechanical Q: Qms 7.14
Electrical Q: Qes 0.47
Total Q: Qts 0.44

Magnet-gap height: Hag (in) 3/8
Hag (mm) 9.00

Voice-coil height: Hvc (mm) 9.00
Hvc (in) 1-5/16
Hvc (mm)34

Maximum excursion Xmax (in) 1/2
Xmax (mm) 12.50

I’d have to introduce him to the program I doubt he’s ever seen the program before, (but he’d soon catch on with how it functions).

He mentioned yesterday about a speaker building paperback book and I know what book he was talking about as I have the same book.

It was published by Radio Shack or Tandy Realistic during the mid 1980’s. I’d have to get that book out of the cupboard.

Might be useful in assisting with the project!

Well a future (another DCX2496 install) can handle the Low-Pass filtering.

Is there any particularly location for where the ported hole should be fitted?

What should the hole diameter size be as well as length of the port tube should I use (flared port type or regular port)?

What would the size of the enclosure be for this type of box?

Guess there goes getting two boxes out of x1 sheet of MDF, LOL

Cheers pos :)

[pos]

Hi

you asked me by PM to post the box and port dimensions on this thread.
The only thing I can do is give you the numbers that winISD proposes.
If you simulate a 80L box tuned to 20Hz in winisd (with any driver, it does not matter, even if the simulated response cruve looks wrong we know that it will be ok with the GTO) you will be able to play with the box dimensions (no particular ratio to respect, even a square box will do) depending on your boards dimensions (optimization) and thickness. The same goes for the ports: you can simulate the length for different diameters and choose depending on what dimensions you can get locally.

How many boxes are you going to build?
Do you have a rectangular room?

[JBL 4645]

Hello pos aftenoon

The thing I have noticed about port size is the box highlights in red at certain size parameter now is that bad? I guess its at best when its highlighted in green I’m guessing is correct with green depending the amount of ports or single port of larger size.

All I can see is port diameter where does it indicate length of port?

Room is rectangular and x16 is round number if I can succeed at 4 I might stop at four if I need to go further I’ll go to 6 and if I’m not satisfied with 6 I’ll go with 8, it’s a guessing game it depends on the room what it likes and doesn’t like.

If only the walls can talk to me I’d have some idea on what sub bass lows it like and doesn’t like.:D

Do you have the precise T-S-P because I was unsure about one detail? Tell you what you knock up the size and I’ll go with that because, I trust you.

Its best for rectangular shape box to keep it slightly narrow in depth for placement around the room too deep I’d be climbing over them LOL.

So a narrow box on the (depth) but same volume size for ported use to give the max at best within a close tolerance of its function.

So what would be the best height of the box, under or over 30”?

cheers

[JBL 4645]

Well I started yesterday after ordering a pre-made enclosure that has worked out fine. All I need to do soon is get new DCX2496 and amps. At present I’m using the amp from Eltax to power the sub. I also changed the sub in the Gale with the second JBL GTO1202D to see how it holds up.

Delivery came just before Atlantis STS-135 launched for the final time yesterday afternoon and after the launch I started opening the box up.

I read though the manual and started to solder the cables up to the binding post screwed the plate into the side and loaded up the box with the JBL GTO1202D and tested it with Avatar on the open to see how the bottom end handled.

I ran a frequency sweep and its better on the lower end but still the room wins with that shallow sloping dip in the middle off to the sides its no problem and won’t be once I get a cluster installed to get around Mr. Null and his sub sucking bass.

[JBL 4645]

Opening the box up item was nicely packed for transport.

[JBL 4645]

Removing the sub from cardboard box looks smart enough and it smells nice and fruity almost good enough to eat I don't know what the smell is but it smells like a Christmas cake? :D

[JBL 4645]

The JBL GTO1202D fits like a glove. All other pre-made boxes I looked at last year was shy of a few millimetres and I can't be asked to spend an hour sanding it down when the size should be universal. Well I'm going with these boxes I'll get another soon and a few more GTO1202D because I want the sub bass uniform as possible with smoothness...

[JBL 4645]

Sooty showed the usual curiosity as to what new item has come. I go out the living room to get the soldering iron and there’s Sooty standing on the sub sniffing it out for 5 paw approval.:D

[JBL 4645]

Sooty has this habit when I’m in the living room he jumps up on top of the subs I guess he’s a bass head. :D

[JBL 4645]

Soldered up the cables screwed the binding post plate to the side.

[JBL 4645]

Nice cables that was provided.

[JBL 4645]

I quickly tested it out then afterwards ran a few frequency sweep graphs that I didn’t bother saving because its going to be different over the many weeks and moths ahead and I know what the room is good and bad at I don’t need to see another frequency graph right yet. I’ll post them once its all finished.

Avatar the opening on left and right front outputs had deeper low end that if I can remember goes below 30Hz with short high peak. The centre low end has the usual nice low end when it come in, sounds neat on the Foley when Sully runs across the top of scorpion while pulling the pins out of the hand-grenades. I can feel the footsteps clunking nicely along with score and choir.

[JBL 4645]

I moved the other sub out way because of the magnetic force on the CRT slightly discolouring in the upper top right corner of the screen. Placement will have to be critical when I put more of then in at the front I can’t place them too near.

LCD screens don’t get issues of subs pulling at the colour I think the same is with plasma screens. I might think about an LCD prices have dropped like stone for 43” even 50” plasma the price is realistic. If I do I’d fit the flat screen so its right in front of the baffle wall or below where the JBL control 5 are placed, but flat screens is far from being on the list as of yet.

Currently playing STAR TREK II The Wrath of Khan region2 DVD first edition I moved the Gale around at the back too near to right wall was drawing low end attention it wasn’t uniform over my ears like it should be. I then placed it to middle of the rear back and that sorted it! Its loaded with JBL GTO1202D for trail tests.

Once I get another sub The Loudest I’ll place it at the centre back rear of the room. All the other subs that follow I’d spread them out and any peak I’d just EQ it down its higher upper peaks that tend to make you look to left or right all the time if the sub is misplaced. The lows ideally should surround you uniformly with low end strength.

[JBL 4645]

Khan, you bloodsucker! You're gonna have to do your own dirty work now, do you hear me? Do you?

STAR TREK II is defiantly the best STAR TREK hands down.:bouncy:

[JBL 4645]

I also faced the sub in the opposite direction for the meantime.

During the simulator test at the start of the film the rear doors open behind and should have deep or uniform low end that give the doors weight as the latch goes CLUNK!

With smaller JBL control 1 its not possible for them to play the low end at high SPL db without damaging the loudspeakers. The low end from the sub to full range surrounds seems unnoticeable.. At times it sounds like an Earthquake in outer space. :D Maybe space has low end that NASA has been keeping to themselves.:p

The floor doesn’t appear to be even! Well in some spots it’s a little uneven the sub was ratting and jolted a few times and that was due to the enclosure tapping or buzzing against the concrete titled flooring. I place a few dust cloths underneath the sub, because that is all I have on hand on a Saturday afternoon and sorted the problem with 0 rattles.