Advice on improving quality of cheap disco speakers

[sajarvis]

Hi,

I have a pair of cheap XL 1350 speakers http://www.koolsound.com/materiel-sono-86-uk.php 175/350w

Each cabinet consists of: Bass driver / 4 piezo tweeters / 1 horn (piezo? No sure ). I am told that the bass driver is 175w RMS 8ohm. The build quality of the bass driver looks OK, but the tweeters really are cheap looking.

problem
The sound quality is terrible at high volume – really harsh and painful in the mid / high range, mostly because there are too many tweeters I’m guessing. I’m not looking for a miracle, just a reduction in the harsh mid / high end sound (which is painful / pretty uncomfortable to listen to). I've played about with a graphic equalizer but I just can't get away from the harsh, "overly loud" sound quality.

I have realistic expecations
These are cheap backup speakers and not worth spending much money on given that £50 on eBay would get a decent pair of 2nd hand speakers.

I am interested in what can be done for minimal cost (just for fun really ). Happy to invest in a crossover or a few caps and resistors (I’m OK with a soldering iron but I’m no crossover designer! I've read lots of posts and articles but talk of decibels, slopes and dropoff's leave me confused!) – I’m not too worried about damaging the speakers but I would be annoyed if I overloaded and fried my amp!

FYI - I Looked inside the cabs and found:
No padding / wadding (easily fixed if required)
No crossover – bass takes full frequency (Which I find surprising)
The 4 Tweeters and horn tweeter are all connected in parallel via a single 20W 51ohm Resister (the resistor is in series to the first tweeter in the chain.

None of the drivers have any markings / numbers / branding in any way. So any crossover would be trial and error / guesswork.

Possible Options
These are cheap speakers BUT I feel that it must be possible to reduce the harshness of these somehow. I don’t want to spend much money as these are just a backup pair. I guess my options are:

1 – Add a crossover. I have no idea what the sensitivity is of the bass driver (or other drivers), so it would be guesswork. But given that the full range is currently going to the bass driver, anything should be an improvement...

2 – remove some of the piezo tweeters – This is probably the easiest way to reduce the painful harshness, but do I need to consider the value of the resistor with respect to the load on the amplifier?

3 –Also.... I happen to have a pair of original (1985 ish) unused Motorola piezo tweeters (the square style) . I bought these in the late 80’s as replacements but never got round to using them - As I recall, these are good for 100Watts(?). I could remove (disconnect) all the unknown tweeters and incorporate a Motorola in each cabinet? But I would need some crossover help with this approach (Just replacing 5 cheap tweeters with one “decent(?)” tweeter might confuse the amp and cause problems)

 

[Keruskerfuerst]

1. Measure the frequency response of all driver units
2. Construct a good crossover.

 

[JonSnell Electronic]

Piezo horns don't use a crossover due to the electrical quality of the cell. The bass speaker will be such that there is no response above 5kHZ so not required there either.
I would purchase the £50 second hand stuff from ebay and use these as a door stop,

 

[sreten]

Hi,

Try wiring the top 4 tweeters in series/parallel instead of parallel.

rgds, sreten.

 

[jneutron]

Get a piece of cloth, like a washcloth.

Wash it very thoroughly using a good combination of dish soap, preferably Palmolive, then dry it using a really good fabric softener.

Get yourself a good roll of duct tape, the black color is best.

STUFF THE CLOTH RIGHT DOWN THE THROAT OF THE HORNS...DUCT TAPE OVER THE SUCKER TO KEEP IT IN PLACE.


There, done.

jn

 

[DrBoar]

I recently showed in an other that you can crossover a pietzo. A second resistor is set across the tweeter terminals say 8 ohms. The the piezo is then transformed to a 8 ohm resistive load and can then be crossed over using a serial capacitor.

With regard to the box. Covering the walls with 10 mm felt or sligtly thicker sheets of BAF will reduce midrange refections. Filling the box with wadding will substantially reduce the output from the bass reflex ports so that is to be avoided.

 

[nigelwright7557]

I bought a couple of 400watt disco speakers for about £80.
They were terrible, I couldn't get any decent volume out of them.

So I built my own, I built 2 cabinets with 2 off Fane Sovereign 250TC's in each.
The difference was amazing.

I just have a few basic tools for the job so its not like you need to spend a fortune on tools. B&Q DIY store even cut the plywood to size for me.

 

[sajarvis]

I recently showed in an other that you can crossover a pietzo. A second resistor is set across the tweeter terminals say 8 ohms. The the piezo is then transformed to a 8 ohm resistive load and can then be crossed over using a serial capacitor.

With regard to the box. Covering the walls with 10 mm felt or sligtly thicker sheets of BAF will reduce midrange refections. Filling the box with wadding will substantially reduce the output from the bass reflex ports so that is to be avoided.

Thanks - what power rating for the resistors and what voltage rating for the capacitors would you suggest?

 

[sajarvis]

Get a piece of cloth, like a washcloth.

Wash it very thoroughly using a good combination of dish soap, preferably Palmolive, then dry it using a really good fabric softener.

Get yourself a good roll of duct tape, the black color is best.

STUFF THE CLOTH RIGHT DOWN THE THROAT OF THE HORNS...DUCT TAPE OVER THE SUCKER TO KEEP IT IN PLACE.


There, done.

jn

I'm will try this! thanks

 

[sajarvis]

Thanks

Hi,

Try wiring the top 4 tweeters in series/parallel instead of parallel.

rgds, sreten.

Thanks - I will try this

 

[Max Headroom]

jneutron is taking the mickey, ignore his advice.

Frugal-phile | Piezo Tweeter Crossovers | J Risch

Dan.

PS - open the cabinets and draw a schematic of the internal connections, and give type numbers of the drivers used.

 

[seanny]

Maybe disable some tweeters. Next time buy a speaker with 4 woofers and a tweeter instead 4 tweeters and a woofer.

 

[jneutron]

jneutron is taking the mickey, ignore his advice.

HEY!!! I'm being serious.

I had two "house calls" to nightclubs where the sound was just downright horrible.

In both cases, my partner and I stuffed bar rags down the throat of the metal midrange horns, and the sound became bearable.

He did say cheap disco speakers..

jn

 

[DrBoar]

I would not dissable any twweters try connecting all four in series and hear if that is enough reduction in level. With regard to the resistor 30-40 in total should be plenty. I used a 5W resistor in my crossover but a single 8" woofer hardly works at disco levels so that lowered the expectstions on the tweeters.

 

[FrankWW]

HEY!!! I'm being serious.

I had two "house calls" to nightclubs where the sound was just downright horrible.

In both cases, my partner and I stuffed bar rags down the throat of the metal midrange horns, and the sound became bearable.

He did say cheap disco speakers..

jn

Yeah, I've done this with bad mid horns. Works a treat. Kills off horrible diffraction products and lowers SPLs a bit.

 

[Max Headroom]

I still say give us guys a schematic.

Dan.

 

[sreten]

Hi,

The schematic has been given. No x/o and a 20W
51R to the piezo mid and trebles all in parallel.

Pretty grim but simple. Not hard to manipulate
if you read up on piezo's and RC networks.

rgds, sreten.

 

[turk 182]

you may want to search the forum for "frankenpiezo" i believe Brian Steele (forum member) did some tweaks to piezo tweeters to improve their quality might be some info and tips you can use.

 

[Max Headroom]

Hi,

The schematic has been given. No x/o and a 20W
51R to the piezo mid and trebles all in parallel.

Pretty grim but simple. Not hard to manipulate
if you read up on piezo's and RC networks.

rgds, sreten.

Ok, ooops I missed that vital bit of info.
Ok, give the mid horn a network as per the link I gave, and bleed a tweeter/the tweeters in on another network as per the link.
A bit of stuffing around but might be a worthwhile learning experience for the OP.

Dan.

 

[sajarvis]

Thanks all for your input. Having read Frugal-phile | Piezo Tweeter Crossovers | J Risch I have sent off for some capacitors and resistors of varying values (2.2 - 5mf / 22 - 50 ohms) and will conduct a "trial and error" experiment on the premise that as long as I'm not overloading my amp, if it sounds better then it IS better. I've also got hold of some wadding too.

incidentally, I have purchased some proper speakers now, but I will keep these cheap ones to experiment with to help me learn about crossovers etc.

My plan is to keep one speaker unmodified and test (with my ears) different options on the other.

I have some questions about the (all be it simple) circuit design, so I'll post a simple diagram when I get my head around the article as mentioned by Dan.

Thanks again.