Help needed with specific components, using Rockford 12" subs with Onkyo receiver. (1 Viewer)

[MikeRamsey]

Hello everyone,
I stumbled across this forum after hours of googling trying to figure out how to properly run subwoofers made for a car with my home theater system. I found this thread, which contained a substantial amount of great information, but unfortunately I couldn't really relate it to my situation.
I am using an Onkyo TX-SR607 7.2 receiver (the easiest place to find solid product info quick is amazon as far as I know, my apologies if that's against forum rules). So far I have only connected five speakers, but that seems largely irrelevant to what I'm trying to do. Two are massive Sony floorstanding speakers, two large Sony bookshelf speakers, and an admittedly weak Sony SS-CN5000 (I kind of got stuck as it's the only Sony center channel I could find at a decent price and I wanted to voicematch the very expensive set of four I was already working with). I'll probably just be wall mounting a cheap wireless pair of Sonys as any hard wiring to the rear of the room would be damn near impossible without it looking tacky.
Now, what I'm hoping to do is put to use an old pair of subs that has literally been sitting in my garage for the last two years. I thought it was going into one of my project cars, but that car ended up getting out of hand and I ended up building a fiberglass enclosure into the area meant for the spare tire, and these 12s were already in the enclosure... soooo... they pretty much fell by the wayside. Figured this would be as good a time as any to dust them off. They are Rockford Fosgate P3s, I believe I have linked to the right product but it's hard to tell as the box seems generic between the 500 watt and 400 watt models (it says 400 or 500 watt, 2 or 4 Ohms, etc...) so I really have no way to tell which they are that I'm aware of.
Will it be possible to connect these directly from their enclosure to my receiver safely? If pictures of the subs/enclosure would help I can upload those. I have tried to include as much information as possible, but if I've left anything out just let me know. I'm not really used to asking for help, I usually just kind of play with everything 'til it works, but I get the feeling that's the wrong way to go when we're talking about frying my system.
Thanks for reading and I'd really appreciate any help.

 

[Robert_J]

That thread is very relavent to your situation. Just filter out the extra stuff.

Just because all 3 of your front speakers are Sony doesn't mean they are timbre matched.

No it is not possible to connect your sub/enclsoures directly to the receiver. Your recevier's sub output is pre-amp level. You must use a separate amp to power your subs.

You didn't address this but it is extremely important - Your sub/enclosure combination may not be appropriate for home theater use. That can't be determined without using the Theile/Small parameters of the sub and the volume of the enclosure they are in. If they are ported then we need the Fb of the enclosure. Once we model them in WinISD or Unibox, then we can recommend an amp. We may also recommend new enclosures as well depending on the results.

-Robert

 

[MikeRamsey]

Appreciate the reply Robert. I did try filtering through that thread but my lack of technical knowledge (and thereby ability to interpret the jargon) severely handicaps me in my attempts to apply the information therein.
As far as your request for information about the enclosure, I'm afraid that's going to be very difficult for me to supply. I believe this is the enclosure I have them installed in based on an inspection of the enclosure and comparison to the specs listed. It has ports for red/black speaker wire behind each sub (resembling the inputs on the rear of a stereo receiver).
I have several sub amps made for a car, but I assume based on the thread I mentioned it would make more sense to purchase a new one that can be more easily powered by a 110v plug?

 

[Robert_J]

Amps were covered many times in the other thread. I use anEP-2500 http://pro-audio.musiciansfriend.com/product/Behringer-EuroPower-EP2500-Power-Amp?sku=480697 as an amp for my pair of 15's and a BFD http://pro-audio.musiciansfriend.com/product/Behringer-Feedback-Destroyer-Pro-DSP-1124P?sku=182467 to equalize the in-room response. Is this overkill for your system? I don't know. I still need the Theile/Small parameters for your subs. They should be available from the Rockford Fosgate web site. And after seeing that enclosure, I'm going to bet that it will not be a proper home theater enclosure.

Besides pro amps, a lot of guys build their amps into the enclosure using a plate amp http://www.parts-express.com/wizards/searchResults.cfm?srchExt=CAT&srchCat=505&CFID=1075286 . This is just a smal sampling of the models available.

Terminology - Those 'ports' you mention are called terminal cups. There are dozens of types http://www.parts-express.com/wizards/searchResults.cfm?srchExt=CAT&srchCat=417 . While ports are really Hemholtz Resonators. They come in all sizes and shapes - http://www.parts-express.com/wizards/searchResults.cfm?srchExt=CAT&srchCat=143&CFID=1075286 .

As I mentioned earlier, we can't proceed without the T/S parameters. Please find them from the information that came with the drivers or from the RF web site.

-Robert

 

[MikeRamsey]

Robert,
Again appreciate your assistance. The plate amp appears to be far out of my range of expertise so I believe I'll be tabling that option. From the link you provided with relation to terminal cups, this appears to be closest in appearance to mine (aside the fact that the "Logic" branding is absent).
The Theile/Small parameters for my sub model can be found here. The exact model I have is the P312D4.
Based on this what would you recommend?

 

[Robert_J]

It isn't perfect but your sub/box comination will actually work for home theater if your room is small to average sized. Stuff each enclosure cavity with 1 pound to 20oz of polyester fiberfil (pillow stuffing available at Wal-Mart. Wire your subs so that the voice coils are in series (8 ohm operation) and install them back in the enclosure. Use the A-500 http://pro-audio.musiciansfriend.com/product/Behringer-A500-500W-ReferenceClass-Studio-Power-Amplifier?sku=480780 to power them. You will need a Y adapter to take your single LFE/sub output of your receiver and split it into 2 outputs.

-Robert

 

[MikeRamsey]

Robert,
I may be misunderstanding you, but if you're recommending the Y-adapter for use with the Onkyo it is a 7.2 system and appears to have two sub outputs build in. Am I incorrect in this?
I assume the stuffing of the enclosure should be a fairly simple process as long as I can figure out how to crack open the enclosure and put it back together, so that should bear no more explanation.
As to re-wiring the subs I have absolutely no idea how to do that. Is it a fairly simple procedure I could figure out through google/trial and error? I checked the owner's manual and couldn't find anything that appeared to be an explanation on how to do this. Is the re-wire being done to accomodate the cheaper amplifier? Could this be avoided by simply purchasing the EP2500 as you initially recommended (or the EP4000 which is nearly the same price)? I assume that would provide better sound quality anyway and accomodate better components at a later point in time.
Also having this seperate amplifier for the subs, will I simply be running a cable from the amp into the receiver? I know this may be a stupid question, I'd just like to cover my bases.
Again, I apologize for my ignorance here, but as I said advanced audio is most definitely not my area of expertise.
Thank you.

 

[Robert_J]

I know nothing about your Onkyo so if it already has dual LFE outputs then you are OK. But the .2 is just marketing. 7.1 means there are seven individual channels of audio plus an LFE channel. .2 is really .1 with dual outputs. I've had 6 subs connected to a 5.1 system so in marketing terms that would be 5.6.

You don't crack the enclosure. You remove the sub.

I assumed that since you installed a multiple sub system and knew fiberglassing that you knew the difference between series and parallel wiring speakers. That should be one of the basics if you install more than a single sub. Each sub should be wired like this http://akamaipix.crutchfield.com/ca/learningcenter/car/subwoofer_wiring/1DVC_4-ohm_mono.jpg

I'm not sure how your curent subs are wired. Series will give you an 8 ohm load and parallel will give you a 2 ohm load. The A-500 won't drive a 2 ohm load so that's why I suggested 8 ohm. Also, these subs only need about 150w to reach full excursion. Using the EP-2500 or EP-4000 (really an EP-2500 with a different name) with these subs would destroy them through over excursion during the first action movie. If you want a larger amp, then you can power both subs with a single amp channel. I'd still wire the individual subs in series and then series wire both subs for a final load of 16 ohms. Use one of the amp's channels to power both.

-Robert

 

[MikeRamsey]

Sorry to bump such an old post but I want to make sure I'm doing this properly. I lagged for a while making the decision because I couldn't get over the thought that I might be better off just picking up a PA-120 or VK-12 or some other entry level home theater sub and being done with it, but after hearing those along with some others I decided it simply wouldn't be enough bass for me. I assume this configuration with the P3's will produce substantially more. I decided to take Robert's advice and go ahead and use the dual sub enclosure I have with my P3's. I ordered the A500 and it should be here tomorrow, along with a ream of 12AWG speaker wire. I'm going to grab the pillow stuffing tomorrow for the box as well. My question is, instead of the afformentioned wiring configuration I assume I'll be using this one correct? http://akamaipix.crutchfield.com/ca/learningcenter/car/subwoofer_wiring/2DVC_4-ohm_2ch.jpg

Also, the amp is rated for 230 watts per channel, the subs claim an RMS of 500 watts. Is it correct that this drop to the 150 Robert mentioned is due to the wiring? Also, is the reason for wiring in this particular fashion is to accomodate the weakness of the receiver I'm using?
Other than that I think I'm good. Appreciate all the help so far from Robert, and thanks in advance for any responses.

 

[Robert_J]

That is the wrong diagram. Even I posted the wrong one earlier. You need the one with the voice coils wired in series.

The amp will push about 160w max based on page 9 of the owner's manual - http://img3.musiciansfriend.com/dbase/pdf/man/m_480780.pdf

I recommended this amp and wiring the driver's for an 8 ohm load because 1. The A-500 can't drive a 2 ohm load. 2. Your subs can't handle more than about 150w at 20hz without bottoming out.

-Robert

 

[MikeRamsey]

My subs are currently wired thusly.
http://akamaipix.crutchfield.com/ca/learningcenter/car/subwoofer_wiring/2DVC_2-ohm_2ch.jpg


And yes I think I posted the wrong link, that wasn't series wiring. I meant to post this one.
http://akamaipix.crutchfield.com/ca/learningcenter/car/subwoofer_wiring/2SVC_8-ohm_2ch.jpg

Is this correct?

 

[Robert_J]

http://akamaipix.crutchfield.com/ca/learningcenter/car/subwoofer_wiring/2DVC_2-ohm_2ch.jpg

This diagram is better. It shows how to wire dual 2 ohm voice coils for a 4 ohm load. You are wiring dual 4 ohm voice coils for an 8 ohm load. Exact same wiring.

 

[MikeRamsey]

Interesting, so basically leave them exactly as they are? I believe you have linked to the exact diagram I linked to to show you the current wiring. I was under the impression that series wiring required wiring the subs to each other so as to give a single load to the amp.

 

[Robert_J]

I only clicked your 2nd link. I need to quit concentrating on work when I'm here at HTF.

No. Series wiring can be wiring 2 voice coils of the same sub. My subs are quad 2 ohm. I have pairs of voice coils wired in series for a 4 ohm load and then each pair wired in parallel for a 2 ohm final load that each channel of the amp sees.

-Robert

 

[MikeRamsey]

Aaah... makes sense. Alright. Well, appreciate the help so far, I'm on the last leg of this little journey (hopefully) and need one last bit of information. I don't know how I overlooked this but I don't have the right cabling around at all. I assume since I'm running two seperate channels into the Behringer I'm running two outputs to the dual pre-outs on the back of the Onkyo. The Behringer outputs through a 1/4" TRS cable if I'm not mistaken. Is there a male to male cable that will run directly from each of these 1/4" outputs to the pre-out inputs? Or am I completely on the wrong track here. I searched all over mono-price but didn't find anything that fit the bill.

 

[Robert_J]

Page 6 of the owner's manual that I linked to above has a picture and description of the back of the amp. Inputs are standard RCA (Item 6 on the description). Speaker outputs are binding posts that take bare wire (Item 10 on the description).

-Robert

 

[MikeRamsey]

Ah. I guess it wouldn't make much sense to use the output ports... sorry I'm half asleep at this point. Anyway, the unbalanced inputs of both 6 and 7 on afformentioned owner's manual are in fact standard RCA jacks. I assume there's no benefit to further pursuing a way to use the balanced inputs correct?

Also, I do use both 6 and 7 here in consideration of dual subwoofers correct?

So to sum up, run speaker wire from the subs to inputs one and two under 10 on the manual image (not using the bridged mono input), then this cable http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10218&cs_id=1021802&p_id=5575&seq=1&format=2 from unbalanced 6 and unbalanced 7 to sub pre-outs one and two on the Onkyo.

Is all of this correct? I keep getting this eerie feeling I'm about to blow something up. It's happened before, so forgive the paranoia.

 

[Robert_J]

Balanced signals only benefit you with both pieces of equipment use them. Your receiver uses an unbalanced signal so you would get no benefit.

Yes. Use both 6 & 7. That is the easiest way.

The connections labeled item 10 are OUTPUTS. Speaker outputs. Sound goes INTO 6 and 7 which are RCA inputs. Think of water running. The signal starts at your receiver and the final destination is your sub.

No. You aren't going to blow up anything. Even if you wired your speakers for a 2 ohm load, your A-500 would either go into protection mode or just overheat and shut down.

 

[MikeRamsey]

Perfect. Well after a quick run to Radioshack and some very sloppy preliminary wiring everything is hooked up. And semi-functioning. Everything comes on and seems to respond well, but the subs aren't kicking like I know they can. For the brief time I had this box in the back of a car it literally shook windows of nearby buildings. This set-up doesn't seem to have them thumping. I wired everything as you recommended, I have the volume for each channel on the A-500 set to about 75%. The Onkyo doesn't have much in the way of settings for a powered sub aside from the crossover (which is at 100hz right now just so I could see if the damn things work... I have no idea what I'll be moving them down to later, suggestions?).
So what gives? I'm using good wiring as far as the speaker wire goes. I'm totally lost on this one.

 

[Robert_J]

You get a LOT of natural gain down low with the small cabin of a car or a truck. That's why they played lower in the car. You were also sitting a LOT closer to them in the car. You have a 3db drop in volume every time you double the distance from your speaker.

The A-500 doesn't have volume controls, it has signal attenuators. They should be turned to "11" to let the full level signal from your receiver through. Also, what is LFE level on the receiver? What are you using for calibration measurements? Does your receiver have a mic with it? Do you have an SPL meter?

-Robert