Connecting an extension speaker to a 15W output practice amp

Krtalaz91 · #1 03-25-2010, 01:25 PM

I was wondering about connecting this old Kenwood stereo speaker to my Fender BXR (45W input, 15W output) practice amplifier. We've had 2 of these big stereo speaker cabinets sitting around the house for a while because we have a new digital receiver and sound system set up for our TV. These speakers used to be hooked up to a multi-component (for lack of better terms) cassette/turntable/stereo system. Would it be possible to hook this up to the extension speaker port on my amplifier labeled: ext. spkr. 8 ohm, 15W ? The speaker, however, only has speaker wire terminals for the input so I'm not sure how I would go about it, but I do have some 1/4" cable jacks and some basic electrical/soldering skills.

Also, on both of these speakers, there are 2 woofers, 1 mid-range, and 1 tweeter, although the bottom woofer speaker cone is totally detached (the foam between the housing and cone seemed to crumble and fall apart). So, I'm not sure if missing one speaker cone would be detrimental at all.

Any advice would be much appreciated. This is not really a necessary project. I am not in a band or anything although I do occasionally play with a drummer friend at which time it's a bit hard to hear the bass with my small practice amp. I'd really like to learn a bit more about sound systems though. I've attached some pictures of one of the speakers.

BassmanPaul · #2 03-25-2010, 01:42 PM

Home stereo speakers do not a bass cab make. You'll end up destroying them.

Paul

riotorgun · #3 03-25-2010, 01:44 PM

wont work,itll sound awfull and most likely destroy the already feeble speakers.buy a bigger amp is my suggestion

LesS · #4 03-25-2010, 02:27 PM

It sounds like the Kenwood speakers are not being used for anything else, so you should try it. It's not the best idea to use home speakers for bass guitar, but you are going to use it only for practice.
Even though it can easily handle the BXR's power, take it easy with the volume and don't turn it up to the point where it distorts (maybe around 12 or 1 o'clock?).
Since your BXR is 8 ohms, you can hook up only one of the speakers.
You will probably need to re-foam the bad surrounds.
Sometimes if the surround is still there, you can repair it with speaker glue.
I think one of the 12 inch drivers in each cabinet is a passive radiator (probably the one mounted at the bottom) - I wouldn't bother to repair the passive radiator.

If the Kenwood speakers will never be used for anything else, here is plan B:
Cut a 5" x 12" or bigger hole in the right side of one and a corresponding 5 x 12 hole in the left side of the other, join the two cabinets together (so they are inter-connected, sort of like one big cabinet) with wood glue and several drywall screws.
Wire the two woofers in series (I would wire just the woofers and leave out the crossover and midrange/tweeter) and connect to your BXR. Now you will have a 3.8 cu ft 2x12 speaker which will sound pretty good for free.

BassmanPaul · #5 03-25-2010, 03:25 PM

Quote:

Originally Posted by LesS

I think one of the 12 inch drivers in each cabinet is a passive radiator (probably the one mounted at the bottom) - I wouldn't bother to repair the passive radiator.

A passive radiator with a hole in it essentially becomes a port.

Paul

Krtalaz91 · #6 03-25-2010, 04:02 PM

okay, cool. I wasn't planning on cranking the amplitude all the way up ( I usually don't even boost the practice amp past the 1 o' clock mark).

So, how could I connect the speaker to the extension port? could I just solder some speaker wire to a 1/4" jack and try plugging it in?

Also, what does the 15W specification for the extension speaker mean? is that just the minimum power requirement of the speaker or maximum output of the amplifier for that speaker. I know the 8 ohms is the impedance of the speakers themselves, but I'm a bit confused about the other specifications. Lastly, how could this speaker be ruined by my amplifier if very little power is being put out since it is only a weak practice amplifier? Thanks again.

**Thor** · #7 03-25-2010, 04:16 PM

It means that the output will put out 15 watts into a 8 ohm
speaker.

LesS · #8 03-25-2010, 04:31 PM

Yes - just connect some speaker wire to a 1/4 inch jack.
I would connect the "+" on the Kenwood speaker to the tip connection on the jack.

The 15 watts is the maximum output of the amplifier - for any 8 ohm speaker.

Even though the ouput is only 15 watts, if you crank up where it distorts, you could blow any speaker, even one with a high power rating.

LesS · #9 03-25-2010, 04:34 PM

[Quote: Originally Posted by LesS
I think one of the 12 inch drivers in each cabinet is a passive radiator (probably the one mounted at the
bottom) - I wouldn't bother to repair the passive radiator. ]

Quote:

Originally Posted by BassmanPaul

A passive radiator with a hole in it essentially becomes a port.

Paul

My point was that I wouldn't waste time trying to fix the passive radiator - you can get used ones on ebay for around $15.
A passive radiator is a port.
A passive radiator with a hole in it is a bigger port.

Krtalaz91 · #10 03-25-2010, 06:40 PM

Awesome. Thanks guys! I've got a good project to work on tomorrow after school then. I know this is no excuse for a good bass cab, but if it works, it beats having less volume.

On a related note, I kind of want to participate in my schools talent show and maybe play a song with my drummer friend, and possibly my other friend that can sort of play guitar (he played hotel yorba by the White Stripes and sang along quite well, but earlier this year, I had to teach him how to play the blues

). My options are to play some Rage Against the Machine cover song because both me and the drummer know quite a few of those songs, a song by Led Zeppelin because the guitarist seems to know some of those, or some blues/rockabilly rendition of mine since play alot of that type of music in my spare/practice time. This would be my first performance besides one time I played Jingle bells and blues at my aunt's elementary school. My other option would be to play everything I can do on a harmonica since I've been playing that for a lot longer (playing bass for a little over a year now).

I'm open to any suggestions and advice, thanks.

LesS · #11 03-25-2010, 06:54 PM

I think the key thing is practice. The three of you should practice all the songs and then decide on which ones sound best. Also you are going to need a larger amp - the 15 watter won't be enough - I would check out the Peavey Basic 112 (maybe used), Peavy Max 115, Fender Rumble 60, etc.

Krtalaz91 · #12 03-25-2010, 08:03 PM

We'll definitely have to do that. I'll have to check out those amps, but I'm not sure if I could get a new one in time. I think the school has some sort of PA system that we could hook up to, not sure though. If I could get the extension speaker thing working, that could definitely help. Thanks for all the help

Krtalaz91 · #13 03-27-2010, 01:08 PM

Awesome! the extension system works very well! The Kenwood really provides a nice deep sound which seems much more powerful than my practice combo-amp's sound. Doing the soldering was pretty fun yesterday since it was pretty cold outside (Michigan weather

) so I practically froze my hands working in my garage.

I'm still a bit curious as to how this speaker works. From what I understand and what I observe, the bottom bass speaker cone is called a radiator and it is not actually powered. So what does it actually do? Does it help drive the sound out more or is it just for tone, because I really like the tone of it with just the top cone attached (since the bottom has broken off)?

If it would help, should I try to reattach the bottom one with some material and special adhesive?

LesS · #14 03-27-2010, 01:37 PM

A passive radiator is "driven" by the powered woofer, and, if designed properly, can improve the bass response. It would be good if you repaired the cone of the passive radiator. Once the cone is fixed, you might hear an improvement in the bass.