Homemade Speaker Cabinet !

[The_Emard]

Since a little while I've wanted to get better speakers for my home theater system. Recently my mother gave me two speakers from an old RCA system. The tweeter on those speakers are blown and it's not very clear what the RMS power handling is exactly. I've been looking on the net to find it but I can't. So I decided to open them to take a look at the magnet. I also got to other speakers which are presently hooked to my receiver.

Here's what I know:

My receiver is a Yamaha HTR-6130. 100 W RMS per channel, 5 channel.

For the moment it is hooked to 5 Yamaha 100 W (Max, 35 W RMS) speakers.
Those speakers have an impedance of 6 ohm. (I always start the unit at -15 and never run the it over 0)

The speakers my mom gave me contains a 150 W (don't know if RMS but it is what is written on the magnet) 6 ohm woofer + a smaller one on which it is written 30 W (6 ohm) and a small (blown) tweeter (unknown everything).

The smaller speaker's got a capacitor on the positive wire as do the driver from the speakers presently hooked to my receiver. (I figured those could be mid-range driver and the capacitor would be the crossover or something)

From the title of the post I bet you've already understood that I now want to put all those together to form a new cabinet.

Here's the list of what I got (twice):

- 6.5 inch woofer (150 W unknown if RMS, 6 ohm)
- 2 inch mid-range (30 W unknown if RMS, 6 ohm) (with capacitor)
- 3 inch probably mid-range (30 W RMS, 6 ohm) (with capacitor)
- Blown pee sized tweeter unknown everything
- Plastic Port from old cabinet (LOL)

I would like to put all that together but the problem is that it must remain 6 ohm (since everything else hooked to the system is 6 ohm and the receiver is set to 6 ohm in the speaker setup menu)

Here's what I would like to know:

First, is it okay if I plug those different speakers together even though they are not rated for the same Wattage.

Second, should I keep the capacitors or not. Maybe I should add one to the woofer so that all the drivers get their own range of frequencies ?

Third, to keep all this 6 ohm I heard of the series/parallel method which would combine 4 speakers of the same impedance and return the total to the exact same impedance .They also say the power handling would be 4 times the power of one of the speakers. Since I don't have identical drivers would the power handling still be the addition of all the different power handling or would it just not work because they are not the same ?

Fourth, is the tweeter really necessary ? I don't know where to find one which would be 6 ohm and I don't want to look over Ebay cause I'd like to finish this today or tomorrow ! (Although it could be useful to have them since I only got 3 drivers and would most likely need 4 with the series/parallel method)

Fifth, anybody knows how to determine the RMS power handling of the 2 and 6.5 inch ones from the 30 W and 150 W written on the back of the magnet ? Could it really be an RMS rating ? I heard the RMS rating is often half the max input, which would make them respectively 15 W and 75 W (RMS). But I'm a bit skeptical since my Yamaha ones are more like 30 something percent of the max rating !

Last question:

There are two possible scenarios here, one in which the values are RMS and the other not.

a)Supposing the series/parallel method is possible to be used with different power handling and size of drivers (and the powers add together).

Scenario 1: I get a cabinet with a power handling of 210 RMS Watt !
Scenario 2: I get a cabinet with a power handling of 120 RMS Watt !

b)Supposing it won't work and the max RMS output will be the lowest power handling rating.

Scenario 1: I get a cabinet with a power handling of 60 RMS Watt !
Scenario 2: I get a cabinet with a power handling of 15 RMS Watt !

a) Will a 210 RMS power handling kill my receiver ?
b) If I get 15 W RMS I screwed (LOL)

Thank you very much for your patience !

 

[j_garcia]

Power handling isn't your issue. You need to know the response of the drivers. Without that info or the gear to measure what the speakers are doing, you can't really build a crossover for them.

 

[The_Emard]

But would it still work if I only removed the blown tweeter and use only the woofer and mid ? (I wanted to post a picture but they say I just have one post so I can't post links)

 

[j_garcia]

Yes, it should still work, but you will be missing the highs. If there is an existing x-over, it will filter out the highs above some point on the midrange driver. If there is no x-over (maybe just a capacitor on the tweeter?) you could pick up an inexpensive tweeter to get it functional or try to find out a part number for the one that is in there and see if you could locate some from somewhere like Parts Express: the #1 source for audio, video & speaker building components or Madisound Speaker Components: distributor of loudspeaker drivers and parts for speaker builders.

It is not uncommon for an inexpensive speaker to have no crossover for the bass driver, but the mid and tweeter usually do have some kind of filter to protect them from low frequencies.

 

[The_Emard]

Yes there seems to be nothing on the woofer but there is a capacitor on the positive wire that goes to the Mid-Range ! I hadn't seen anything on the wire to the tweeter ! My thought is that the capacitor is in series with the mid-range which in turn is in parallel with the woofer and thus making the capacitor parallel to the woofer (which supposedly would cut the lower frequencies from the mid-range and drive them to the woofer) But I haven't figured just yet what happens to the tweeter since it is also parallel to the mid-range ! I've made a drawing but can't post it... i suppose a could post 3 times more and then I could post my drawing !

 

[j_garcia]

Sounds like the capacitor is filtering for both the midrange and tweeter.

 

[The_Emard]

It's what I thought also... but wouldn't the fact that it is parallel to the tweeter make it play low frequencies ! The tweeter was completely blown.. maybe that's the reason why !!! But it would have been pretty stupid from RCA to make it that way... and the other cabinet doesn't have the blown tweeter ! In fact the other one is in mint condition ! (One more post and I can send my picture lol)

 

[The_Emard]

There you go:

 

[j_garcia]

Yes, that will work, but like I said, the highs will still be missing because the midrange driver cannot produce them as well. The three drivers were likely chosen because they have a natural roll-off that blends adequately, which is why there is no x-over handling each driver. Nearly all inexpensive speakers are built this way, with a single cap on the positive lead to the mid/high drivers. The cap is one way so it only filters in the direction it is oriented, which is why it has no effect on the woofer.

To use the same midrange without the tweeter, you would still likely want to use the same cap. Switching to the 2.2 will have unpredictable results without knowing what the operating range of it is.

 

[The_Emard]

You mean I could use my Yamaha speaker combined with the RCA woofer no problem as long as I keep the 80 micro farad capacitor on the positive wire of the mid-range ? And that wouldn't make the cabinet 3 ohm ? This is where I get a bit confused ! Why is that they say when you wire two speakers in parallel you half the impedance (if they are the same impedance naturally) but the total remains if you put a capacitor on one of the speakers ?

 

[lsiberian]

You could get a dayton woofer tester. To evaluate the drivers. If you have access to an open area outdoor testing the drivers could help get a range.

 

[The_Emard]

Sounds like a nice idea ! But I don't think I've got the money ! Thanks anyway !