silly sub question...

[treejohnny]

I have a JBL 12 sub with the plate amp non functional. I have a 7 channel 130w 2600 yamaha receiver. To run this sub as extra what crossover do I need ? Is the crossover more expensive than it is worth?

Right now i am using 5 channel and zone 2 ...but not the b side of mains.
There is only two wires going to the sub speaker and i am assuming it is single voice coil. Would i have to hook up right or left or can i use both with crossover some how like the lfe signal ?

 

[majorloser]

You could always replace the plate amp:

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=300-805

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=300-750

 

[treejohnny]

I know....what I am talking about is a little...or alot generic....but i dont think that this sub is worth putting $100 in. I do believe i will be making my own sub (leaning towards the perfect kappa) and I have friends sub to use til then. But i do have to do something with this thing....might be good to put in the garage if i can use a cheap crossover ?

 

[mtrycrafts]

Right now i am using 5 channel and zone 2 ...but not the b side of mains.
There is only two wires going to the sub speaker and i am assuming it is single voice coil. Would i have to hook up right or left or can i use both with crossover some how like the lfe signal ?

The problem I see is that you will not get the LFE channel in one of those mains unless you reset the receiver to 'no sub.'

But, not sure if that will mess up your impedance on that channel and go into protect mode.

 

[majorloser]

I guess if your receiver has some dedicated inputs for Zone 2 audio you could run an RCA cable from the Zone 1 LFE to Zone 2 "R' or "L" inputs and use that channel to drive the sub. It would require you to run both zones at one time and would probably be a real PITA to calibrate and control.

But this would all hinge on whether the subs driver is 8 ohms. A lot of subs use 4 ohm drivers. Could be a quick way to cook the receiver.

Don't use the B side of the mains to power the sub. This is the same "R" and "L" signal from the mains that is run in parallel. Also not very healthy for the receiver.

You could also pick up a cheap amp to power the sub from the LFE. By using the LFE channel you'll have better control and won't need a crossover.

 

[treejohnny]

Well I think I have come to a conclusion. I intend to build my own sub (using the perfect kappa vq) and i will be using the dayton 500w plate amp from parts express. I could get the plate amp now and use on the jbl box and driver, atleast til i fry the driver or get my home made sub finished.

 

[majorloser]

Might even want to look at the PE kit subs. They've gotten good reviews.

 

[treejohnny]

Do you think that the PE 15" kit would be better than following the perfect kappa build in this forum ?

 

[WmAx]

Do you think that the PE 15" kit would be better than following the perfect kappa build in this forum ?

I guess that depends - I don't know of any driver more suited to ANY application as compared to the Perfect VQ unit. It has very low distortion; a superb motor. But the real kicker is the highly variable Q, which allows IDEAL suitability to any application. So even if you change your mind down the line, this driver is still suited to any application you may want to use it for without any compromise in performance: small sealed, IB, small ported cab, large ported cab, bandpass cabinet, and probably even TL(though I have not tried to model it for this application).

-Chris

 

[treejohnny]

Ok, I have read alot on building a sub on this forum and the sub build with the perfect kappa. Is there someplace else i can go to read more ? I intend on following the build on this forum with the same cu ft and go ported, assuming that it is the best for ht/music in home. I am not entirely sure how well my slot port will turn out. Next question will be down(should there be a solid board under the sub or let the floor be right under, in this room, finished hardwood) vs forward firing. Assuming that 3/4 or 1" mdf board is best and using my 3/4 plywood for bracing, every 12"? The last question (for now) will be how to finish, would like to have a wood finish like oak.

 

[WmAx]

Ok, I have read alot on building a sub on this forum and the sub build with the perfect kappa. Is there someplace else i can go to read more ? I intend on following the build on this forum with the same cu ft and go ported, assuming that it is the best for ht/music in home. I am not entirely sure how well my slot port will turn out. Next question will be down(should there be a solid board under the sub or let the floor be right under, in this room, finished hardwood) vs forward firing. Assuming that 3/4 or 1" mdf board is best and using my 3/4 plywood for bracing, every 12"? The last question (for now) will be how to finish, would like to have a wood finish like oak.

Down or front firing, does not matter. Leave 4" or more if down firing, is my recommendation. You do not need a board under the speaker, but if you prefer to do this, it will not hurt anything. You can easily use a good hardwood cabinet grade 3/4" ply for the entire cabinet and brace it properly -- it will work fine and be lower in weight as compared to MDF.

-Chris

 

[treejohnny]

The next question will be on the port design. I am assuming that the interior design of the port must be uniform thought the length and bends ? I am contemplating making the sub enclosure 4'ish tall to allow me to use straight port(run diagonally). Is the slot port being 2x13x50 the optimum size ? At this time my best construction idea would be to get 2" pvc and rip in half for the curved parts of the port and securing to port board with an epoxy. All ideas are welcome as I can surely use the help.

 

[treejohnny]

I have come to the decision of making the downfiring sub with aprox dimension of 24"X24"X20" and will have 4" legs under it. It will be made of 3/4 oak plywood and I am thinking of having a piece of glass on top (isolated with some type of rubber?) of it to use for end table. It will sit on top of a hardwood floor (atleast for a few years). Any suggestions on what to use for the legs?

 

[avaserfi]

I have come to the decision of making the downfiring sub with aprox dimension of 24"X24"X20" and will have 4" legs under it. It will be made of 3/4 oak plywood and I am thinking of having a piece of glass on top (isolated with some type of rubber?) of it to use for end table. It will sit on top of a hardwood floor (atleast for a few years). Any suggestions on what to use for the legs?

Since you are planning a down firing sub be sure to estimate driver sag into your excursion equation as it is different for ever subwoofer and will minimize maximum excursion the sub will be capable of.

For the legs you could use wood rounds. Due to the weight of the sub and cabinet you will probably want a more dense wood, but it is possible to get 1" oak rounds (or make them). This would be more than sufficient.

For the glass tabletop you will definitely want to use some rubber to isolate the glass from the wood to insure no vibrations are transfered making distracting vibrations.

Ply is a great choice to work with it is more dense and lighter than most forms of MDF. As far as placing the sub on a hardwood floor you will want to use something to decouple it from the floor to keep resonance and vibrations out of the equation. You could use something like the auralex gramma pad or buy high density foam from foamonline and build a decoupling module - both will likely raise the sub a few inches.

 

[treejohnny]

How is your sub coming along ?

Since you are planning a down firing sub be sure to estimate driver sag into your excursion equation as it is different for ever subwoofer and will minimize maximum excursion the sub will be capable of.

I am using the same driver as you are. I wasnt aware of any changes I need to make to have it down firing?


For the legs you could use wood rounds. Due to the weight of the sub and cabinet you will probably want a more dense wood, but it is possible to get 1" oak rounds (or make them). This would be more than sufficient.

For the glass tabletop you will definitely want to use some rubber to isolate the glass from the wood to insure no vibrations are transfered making distracting vibrations.

I am sure i can accomplish this, with a little experimenting

Ply is a great choice to work with it is more dense and lighter than most forms of MDF. As far as placing the sub on a hardwood floor you will want to use something to decouple it from the floor to keep resonance and vibrations out of the equation. You could use something like the auralex gramma pad or buy high density foam from foamonline and build a decoupling module - both will likely raise the sub a few inches.

I have never seen any subs using any decouplers like these. Do you have any pictures? What will you be using on your subs?


Sorry I havent figured out how to do the quotes right....

 

[avaserfi]

How is your sub coming along ?

Great - I just need to make my cables (soldering them together), and place all the dampening otherwise its all done. I will have it fully functional by the end of the week. No questions.

I have never seen any subs using any decouplers like these. Do you have any pictures? What will you be using on your subs?

Temporarily, I will be using rubber feet from parts express. Once the upper portion is complete I will be using foam from the website I supplied by mounting it in between two pieces of wood. The picture in this thread is an example (below the speaker). This is likely an overdone version for your application. Rubber feet will likely work well enough for you in the end my speaker will weigh around 350lbs.

As far as driver sag it most likely won't become an issue (being no more than 5-10%), but I would rather allow myself all the headroom possible and mount the driver on the side.

 

[WmAx]

Rubber feet will likely work well enough for you in the end my speaker will weigh around 350lbs..

Rubber feet, of the common variety, are not going to have any appreciable de-coupling. The stiffness of the compound is too high in relation to the mass attached/sitting on it -- causing a resonant frequency of this spring system to be well above the passband you want to filter out.

-Chris

 

[treejohnny]

Well I have the correct title for these questions.
Has anyone checked into making a sub out of rock/marble/stone to see if cost effective?
For the de coupling, any sugestions for the sub weighing apox 130#? 4 racquet balls? I am assuming that the felt/foam wood floor protectors are not so good?

I have seen chris's speakers and i am wondering if all of the decoupling is for the main speakers and/or the sub? If the sub is important to decouple then why dont expensive subs look like they have that done to them ?

Is there any changes I should make with the sub being down firing? It is the best/cheapest design for what I am trying to achieve.



I know I have lots to learn, dont take offense to any silly sub questions in this silly sub thread.

 

[Highlander]

Down or front firing, does not matter. Leave 4" or more if down firing, is my recommendation.

What is the reasoning behind your recommendation of 4" or more?

 

[avaserfi]

Well I have the correct title for these questions.
Has anyone checked into making a sub out of rock/marble/stone to see if cost effective?

This would be complete overkill for the application in terms of removal of resonance. As far as making a sub out of these materials it is possible, but would be very hard to work with and weigh a ton. Also, it would cost a pretty penny.

For the de coupling, any sugestions for the sub weighing apox 130#? 4 racquet balls? I am assuming that the felt/foam wood floor protectors are not so good?

The racket balls probably won't work as Chris mentioned they will be too stiff. The foam on a wood floor is just fine, it is fairly soft and won't scratch the finish or anything. This would probably be your easiest alternative. I have one of these on wood floor with zero issues.

I have seen chris's speakers and i am wondering if all of the decoupling is for the main speakers and/or the sub? If the sub is important to decouple then why dont expensive subs look like they have that done to them ?

While decoupling is not 100% necessary it is required for achieving maximum sound quality. Yes, few commercial subwoofers come with a decoupling system built in. I think this so because it is often seen as the domain of room treatments and such - not necessarily needed on the sub itself.

The decoupling system I linked is for the entire system, but it is beneficial to the whole thing. Different amounts of material are needed depending on the types of frequencies being produced. Lower frequencies generally require more dampening to decouple them from the potentially contacted surface due to their wave length.