Cheap 2-way set of speakers

[TomJ]

I have been listening to music on a bush mini system any one from britan will know that this is one of the cheapest and worst makes so anything will be an improvment. The amp I am going to use is 60w @8ohms.

I have tools and wood working skills so making the cases wont be a problem.

I am going to use the Linkwitz-Riley Electronic Crossover.

High Pass - frequency is approx. 310Hz
Low Pass - frequency is approx. 310Hz

I would like the speakers not to be floor standers more like shelf speakers.

Does any one have some designs, as many poeple I am skint so I dont want to pay more than £100 if their are realy nice £150 (this dosn't include cost of wood, paint, skrews or anthing like that just the drivers).

[Bull]

I can't understand why in the first place why you would buy such an awfully made system,the speakers are made so poor,that they either fall apart very easily and blow up very easily.
Those cheap cabinets are made of hardboard,plastic and thin chipboard.With drivers which are so badly made you would normally find at a car boot sale or in old cars at the scrap yard.

Now to help you find some drivers for not much money.

2x Audax AP210Z0 8 inch bass/midrange,70w rms,8 ohms,29hz-6khz,sens 90db at 1w 1m. Cost £26 each inc vat

2x Motorola/CTS piezo horn tweeter KSN1165A 200w rms/400w music [includes built in protection circuit] £12 each inc vat
[No crossover is needed with the piezo tweeter]


If you decide to buy these,plus the extras[wire,grille cloth,terminals] go to www.maplin.co.uk these two products are from maplin electronics,either go to many of there shops or order and buy online.

[TomJ]

1. I id not want to buy such a bad system it was the first one I ownwed I needed it so I could listen to music and at the time i didn't realise there was such a big diffrence between sound systems

2 How do you hook up the tweeters with out a crossover

[Bricolo]

Originally posted by TomJ


2 How do you hook up the tweeters with out a crossover

wire the woofer in series with it's crossover components, ant this all in parallel with the tweeter

[calum]

Dude (tomj)
Your story/situation is exactly the same as mine!!!
cool. I dont feel so alone (sob, sob)
How far have you got with the speakers?
I have a sony portable stereo and it really sounds crap.
I also like the stylee of your budget, are you a student too?
If you have any progress please keep me posted (e-mail if you want) so I can get a pair on the go.

Take it easy folks
Calum

[planet10]

Originally posted by TomJ
The amp I am going to use is 60w @8ohms....I am going to use the Linkwitz-Riley Electronic Crossover @310Hz

Do you have a 2nd amp to use with the active XO?

If you are building a small 2-way and using this as the XO, then you should be looking at a 6 or 8" woofer and a 2 or 3" mid-tweeter (full-range). Fostex FE83 or one of the TangBands (lots of info on the forum about the W3-871s). Since you are in Europe there could well be some suitable Vistatons or Monacors. HiVi Research also have some this size.

You could also look on eBay for these kinds of mid-tweeters. I have some little Telefunken ovals that were used for this purpose, and have sold a couple other prs.

A little more off-the-wall would be a set of 25 or 35mm HK Odessey drivers (as found in iMacs/eMacs etc). These would likely have to be gotten as service parts (that is how i got my 25mm ones -- the 35mm came with my wifes Cube)

dave

[calum]

Bull
If I got those drivers you sugested (audax, motorola) what kind of box should I be making for those, what xo design and do ya reckon they will sound good?

I know its a lot to ask but i really dont have a clue. Am learning though.

Calum

[TomJ]

Calum,

I am a student as well at the moment, I have not started these speakers yet. When i do i will keep you posted on the progress.

[dooper]

Originally posted by Bull
<<SNIP>>

Now to help you find some drivers for not much money.

2x Audax AP210Z0 8 inch bass/midrange,70w rms,8 ohms,29hz-6khz,sens 90db at 1w 1m. Cost £26 each inc vat

2x Motorola/CTS piezo horn tweeter KSN1165A 200w rms/400w music [includes built in protection circuit] £12 each inc vat
[No crossover is needed with the piezo tweeter]

<<SNIP>>

Hello Bull,

I see you are still a regular here, so I'd like to seek your advice on the above drivers. Of course, other readers are free to post their two cents (tuppence? euros?).

I haven't seen an on-axis response curve for the CTS tweeters, but the Audax 8" looks pretty ragged above two KHz or so. I think that a 12 dB / octave LC filter in front of the Audax would help with this. Maybe two or three KHz?

The CTS piezo is rated at 92 dB sensitivity, a little more than two dB hotter than the Audax 8". Any specific recommendations on padding the piezo down a bit? Would the piezo benefit from any filter circuitry?

Specific question - if the LP filter in front of the 8" driver was constructed for -3 dB at 2250 Hz, what (if any) would be recommended to reduce the piezo's level and / or smooth its response.

Thanks all - I read all I can, but I always benefit from the experience of those who have actually gotten the slivers and the blisters.

dooper

[planet10]

Originally posted by dooper
The CTS piezo is rated at 92 dB sensitivity, a little more than two dB hotter than the Audax 8". Any specific recommendations on padding the piezo down a bit? Would the piezo benefit from any filter circuitry?

The piezo really does need an XO... they sound really hard without one. 4-5k is as low as i'd go with these.

dave

(cut and paste, most of the below information credited to JON RISCH)
The Parts Express catalog suggests putting a 20-Ohm resister inline with any Piezo tweeter to make it a more stable load for an amp.Will this not also attenuate the tweeter? If so, and if I need further attenuation, can I simply add more resistance? Is there a rule of thumb for how much attenuation I will get with further resistance, or a way to compute this number?

The recommended resistor is to help protect the amplifier from oscillating due to the raw capacitance that is a piezo driver. Adding resistance in series with a piezo will actually roll off the highs a bit, adding more will roll off the highs noticably. To attenuate a piezo, add a series cap, which creates a voltage divider with the capacitance that is the piezo drive element. Most piezo elements run in the 0.1 to 0.26 uF range, so a cap of the same value as the piezo element will attenuate it 6 dB.

Piezo's can be crossed over, and to great advantage. I have often thought that some of the bad rap piezo drivers have is due to the "you can use them without a crossover" fallacy. Yes, you _can_ use them without a crossover, but just because you can get away with it, does not mean it is optimal.

Since most piezo's are used in inexpensive systems, the cost of adding in "unecessary" components is often never even considered.

How to crossover a piezo:
Add a resistor in parallel, and the driver can be made to look like a current driven device to any outside components, such as a crossover cap. However, to keep costs and power dissipation down, 8 ohms is way too small of a value. The impedance of most piezo's is still quite high at 20KHz, so use a 22 ohm resistor, this makes any series crossover cap smaller and less expensive, and the resistor dissipates less energy. Use of an 8 ohm parallel resistor will also tend to lose you a little bit of output level.

For most piezos, use of a 22 ohm resistor, and a 4-4.7 uF cap will allow the response to be identical to what it was in stock form, but rolls off the lows at 6 dB/oct below 1 kHz or so. This actually increases the power handling of the piezo, as it is voltage limited. Exceed the voltage used to pole (polarize the piezo element during manufacture) the unit, and it will loose sensitivity, and eventually burn out. Most pro grade piezos will handle 35 volt transients, and 28 volts continuous, which are 150 watts and 100 watts into 8 ohms respectively.

Add in a capacitor and 22 ohm resistor, and the power handling could effectively be quadrupled, as the LF voltages are not imposed upon the unit, just the HF voltages.

Piezo's crossed over in this manner don't sound as harsh and spity, and tend to be quite a bit more reliable. Many of the piezo units have a mild peak just before they roll off in the LF, so making the series cap a little smaller can actualy flatten response, and provide even more protection and smoother sound. For the smaller piezo units that cut off at 4-5 kHz, a series cap of 1.5 uF will do the trick, larger units that go down to 3 kHz can use a 2.2 uF, and the large compression driver units meant to be mounted on a horn need about 5 uF, as they do not peak, and any higher would lose the sloping output even more.

Attenuation, HF roll-off AND the crossing over can all be done at the same time. To attenuate, place a cap in between the piezo and the 22 ohm resistor that is shunting across the unit, then if HF roll-off is desired, use a series resistor in this location too. Then the series crossover cap should be in front of the 22 ohm shunt.

Looking from the amp, first the series crossover cap, say 4 uF, then the 22 ohm shunt from hot to ground, then a series cap of about 0.15 uF for 6 dB attenuation, and then a series resistor of about 30-50 ohms to tame the very top end, then the piezo itself.