KCMaxima98

iTrader: (4)

I know that if you have two 4 ohm SVC subs hooked up in parallel on one channel the amp sees a two ohm load. What about running two 4 ohm subs in parallel bridged mono on the amp? Is it still a two ohm load?
What about running one dual voice coil sub, with both voice coils hooked up to a bridged amp? Would the amp see a two ohm load there too?
I am trying to get the most out of my amp with the least amount of speaker in the trunk and need some help. I have an old punch 200x2 currently powering a P1 15" punch in bridged mode. Is this a four ohm load? RF claims that this amp produces 400 wrms bridged at four ohms. It doesn't sound like that much power to me but maybe I am used to it since I have had this amp since like '98. The sub is in a cheap, pre-fab, sealed box too, which may be part of the problem too.
Sorry to ramble, but when I was young, I would just hook up two subs in stereo and call it good cause I didn't know about all this Dual voice coil, ohm load, parallel wiring ect. jazz. Thanks

Robert_J

Yes it is. But the amp is working just as hard as if it were a one ohm stereo load.

Yes. To the amp, a voice coil is just a voice coil whether both are on the same sub is irrelavent.

Probably. I don't know the specs of your P1 sub. I know that RF made both four and eight ohm subs at one time. They also made single and dual voice coil subs.

How do you know what 400 watts sounds like? 400 watts fed into speaker A will sound twice as loud as 400 fed into speaker B if the sensitivity rating of speaker A is 3db more than speaker B. Besides speaker sensitivity, alignment (type of box), quality of the enclosure, size of the car, etc. all factor into the SPL.

There is SOOOOOO much more to it and it all starts with Hoffman's Iron Law.

-Robert

KCMaxima98

iTrader: (4)

Thanks so much for the help. BTW, the sub is a new P1 and it is a four ohm speaker. And I know it is hard to put a finger on what 400 watts "sounds" like but I am just basing it off of what I "remember" it sounding like before. Like the butt dyno, this is a bad way to measure, I know.
So from what you said running one dual voice coil speaker in parallel is the same as running two single voice coil subs in parallel right? And the amp would work as if it is a one ohm load in each case, correct? The reason that I ask is because I had problems with the amp shutting down because of heat or stress when I had two SVC subs running in parallel off of it on bridged mode. Now that I have just the one single voice coil sub running running in mono, I haven't had any problems. I was considering getting a dual voice coil sub to replace it but I don't want to run into that problem again. Now, I think that I will build a ported box for the one I have and call it good.
BTW how do the boxes with the slotted ports sound? I have only heard the ones with tube ports.

Robert_J

If the openings are the same size (in square inches), then there is no audible difference. Now we can get nit-picky about this since round ports have the least amount of surface area for a given port size so there will be less surface friction. Each one has other advantages. Slot ports are easier to build into the box construction. That way they can be longer and since they can be longer, you can make the opening larger. That will stop port noise. Round ports can be purchased with flared openings. Just cut a hole and bolt it in. The flares reduce port noise also so you can go with a smaller than optimal port.

Are you going with a published RF design or are you coming up with one on your own? If you come up with your own design, I recommend using UniBox if you have Excel loaded on your PC. If you aren't a MicroSoft Office user, then WinISD is the next best free design software.

-Robert

KCMaxima98

iTrader: (4)

Yeah, I think that I will build one to spec from my manual for the sub. It calls for a 4x9 inch tube port in a box that is 2.5 cubic feet, I think. I just have to find some place that sells a port though. Also, I hear you have to have a special blade on your saws to cut 3/4 mdf so it should be interesting. But I will feel better building it myself I think. Thanks for the help.

Robert_J

That would make it tuned to 33hz. Remeber, that is 2.5 net cubic feet. You need to take into account the port (treat it as a solid object), any bracing and the driver displacement.

PE Trim the center part to length. If you want to play with tuning, thin walled PVC pipe will work as a substitute for the center tube. Once you settle on a tuning frequency, you can trim the original tube to the correct length and glue it in.

Carbide tipped blades are recommended. Harbor Freight has a good selection of inexpensive blades. They work good for everyone except a professional cabinet maker. Get a good mask and eye protection. MDF dust is dangerous.

There are many different philosophies on box building. I use wood glue and clamps. Sometimes I'll add biscuits. Never screws or nails because they will get in the way when I round over the edges with a router. If you use screws, pre-drill the holes and get a counter sink tool so the MDF won't buldge and split. If you still want to round over the edges, you can remove the screws and not affect the strength of the box. The bond of the wood glue is stronger than the wood itself.

-Robert