DIY Speaker system

[Picarro]

Hi audiophile people

I am new to this forum, but you lot seem very knowledgeable!

I am in the process of building a speaker powered by car batteries for outdoor use.

I already have a 12 volt amplifier, the AMP9-BASIC from 41hz.com. It's a 4 channel 4x50 watt amplifier, but I only plan to use 2 of those channels.

The speaker system needs to be home made, and I have the following components to put in it.

2x 15" Cerwin Vega Subwoofer, CS2030
4x Unknown midrange speakers, 2 are of the same type
2x Cerwin Vega Tweeters, with the markings C5, 8ohm and 8043
2x Unknown Tweeters, with no markings

All these were pulled from an old huge Cerwin Vega speaker which someone had clearly molested (it saddened me to no end).

This speaker is being build on a BUDGET. The aim is not audiophile quality, the aim is to actually get it to play music AT ALL.

My plan was, and do correct me since I am probably wrong, to take one of the 15" subs, the 2 midranges of the same type, and the two, possibly four, tweeters and link them up in a box of about 50x50x70 cm's (175 liters). In this box would also be some pieces of electronic, but at most a liter or so.

I would build my own crossovers, with a band pass of 100-500 hz for the sub, 400-4500 hz for the midranges and a high pass of 4000 hz for the tweeters. I was thinking of bridging the subwoofer to two of the 4 channels in the amp.

The reason I do not want bass below 100hz is because Saturnus, who made The Boominator, states that most if not all of the bass is lost below 100 hz when playing outside.

The whole thing would run of multiple car batteries in parallel and music would be supplied with an iPod.

Remember, this is NOT build for audiophile sound quality. It's build to play somewhat loud, but most of all to play decent music for a couple of days in a row.



My system last year consisted of a 4x50 watt car radio, two batteries and two B&O speakers. But since the speakers were only 2-way, there were next to no bass. (Nevermind the fact my parents hated me for bringing their precious speakers to a festival). This system could play for 7 days straight, around 8 hours a day at reasonable volume.
I want my new system to do the same, but since I am a bit a tech-head I want to do all of it on my own!

I can supply pictures of all of the drivers I plan to use if required.


What are your thoughts?

[wintermute]

I would certainly not filter the bass at 100Hz!!

Outside the baffle step will be more pronounced (probably the full 6db) but all that means is that you should add more baffle step compensation in check out this link Baffle Step Compensation if you are doing an active crossover you can add in Rod's simple baffle step compensation circuit and get back your "lost" bass

Apart from that I don't know anything about the particular drivers. If you can do measurements of them that will be the best. as text book crossovers generally will not work as expected. At a bare minimum, impedance measurements (or traces from manufacturers curves) will help to determine crossover components, somewhat better than a pure text book circuit.

look at the manufacturers curves for the speakers to see whether they overlap well for your selected crossover points.

You will need an active crossover for the subs, and based on the fact you have four channels on your amp you will need to do a passive for the mid/tweeter (unless you want to get another amp).

This actually works out reasonably simple as you only need to do two "two way" crossovers one active and one passive, and don't need to worry about a bandpass crossover.

I guess the main thing to check will be whether the mid's will play ok up to the 4000hz range. if they will then you can probably make a relatively simple passive crossover (perhaps 2nd order electrical) and get an ok sounding speaker (you should always design for an acoustic slope but that needs real measurements). That's overly simplifying things, but for what your stated goals are I think it is reasonable

Tony.

[Picarro]

Yeah so .. My head just imploded from that post.
I have no way to get the measurements. I tried contacting Cerwin Vega directly, but their reply was "we know the measurements for the speakers, but not for the individual drivers". And besides - the drivers are a MESS of mixed units with no information written on them :-/.

For the crossovers, why would I need an active crossover for the subs? And is it a question of "textbook crossovers will not work" or "textbook crossovers will work, just not great"?

Testing the mids up to 4000 hz - is that simply a question of hooking them up to my amp and start rolling off sounds increasing to 4000 to listen whether they stop sounding properly?

Unfortunately, I don't have any electrical equipment at hand to measure the drivers. The stuff I have is a simple headset microphone, and assorted workshop tools..


I know that this must hurt your audiophile part deep down, but .. Sorry..

[Richard Ellis]

I had done something similar once upon a time...
Pictures of all the drivers will help immensely......chances are someone might know of them. The best approach IMO, would be to replicate the CV loudspeakers........Having two enclosures, one would have the battery/amp unit the other would not , an interconnect between, say a thirty foot plain zipcord ....14 gauge or so. Thirty foot would give you some degree of sound-stage.
Dual batteries will make for a TOO heavy unit. An on-board battery recharger would clean things up....Putting one battery for each enclosure might work but you would have to run a second interconnect to supply power....even if you had 'divided' your amp, you would still need signal.
Pictures please, so we can move forward with your project.

__________________________________________________ _____Rick..........

[sofaspud]

If you have the old speakers, can you have a look at the crossover CV used? If you can get some component values there, we'll all have something better to work with. I believe this is (part of) the approach Richard mentioned also.
What about 2 channels driving the bass, and 2 channels driving the mids/highs? 100W is 100W, whether it's from 2 channels or 4.

[Richard Ellis]

Great idea 'Spud' !!! That eluded me.....of course the woofer amps will be drawing the Lions share of power....
In effect it will be Bi-amped........

__________________________________________________ ____Rick......

[Picarro]

@Richard

Doing seperate units is a nono - I have to be able to transport in a single piece. For that I would use a standard trolley. The kind you buy at hardware stores that can lift a couple of 100 kg's .. Not that I want it to weigh that much in any way.

@sofaspud

I do have the crossovers and I'll get some pictures of the drivers+crossovers.


I really do appreciate you guys helping me. If you ever need a helping hand at computers, visit bit-tech.net - I roam the forums as Picarro too, and I know a fair bit more about computers than speaker systems

[Picarro]

The markings on the parts of the crossover are (left to right): 40 MFD, 75v - 2.5 UFK, 200VDC - 2.5 UFK, 200VDC
The little brown box at the bottom of the picture says: 47 (ohm) 18% 5W

The other crossover have slightly different components: Between the 2 small white capacitors on the above crossover, there is a larger 7 UFK, 200VDC capacitor. There is also no yellow capacitor like on the above picture.

I know these crossovers are a hack-job. They look like someone basically shat on them with wire and a soldering iron..

The front of the crossovers look like this:

[sofaspud]

I can't get the pics as anything but a thumbnail. It's the last 2 I'm most interested in.
Re: the 4-channel idea... simple to just capacitor the tweets and build an active filter to split highs and lows for the amp inputs. The you could set the amp input sensitivity for a desired max current draw from the battery.
And I may take you up on the offer. If you can help me get some DOS stuff fixed on Vista (or Win7) I'd be eternally grateful.

[Picarro]

These images should be the correct size now. Stupid Imageshack resizing -.-'

Re: the 4-channel idea... simple to just capacitor the tweets and build an active filter to split highs and lows for the amp inputs. The you could set the amp input sensitivity for a desired max current draw from the battery.

If I understand that correctly I should build a high-pass filter for the tweeters, and an active filter? for the sub. The amplifier doesn't have separate inputs, just a single jackstick for an iPod. That signal is then distributed to 4 50 watt channels.

This is the amp: AMP9-BASIC

For something like that you should ask in here:
Software - bit-tech.net Forums