low on cash, need advice on driver selection etc. please.

[Kram]

Hi everybody

Not so long ago the speaker cones on my dads speakers broke (old age i think) and ive been wanting to find some replacements.
what i require advice on is erm, everything basically.

I had origanally planed on just replacing the driver but upon inspection of the speaker i found that the cross over consisted of a 3uF capacitor only, and after reading on this site about speaker design i began to think that just one capacitor just didnt seem very good so now i want to build a cross over as well, then i thought that i may as well buy a new tweeter too.

Now the question is can anyone recomend a decent sounding mid/bass driver and a tweeter that will cost between 20-30 UK Pounds each and roughly the same for crossover components too.

By the way i am looking to keep the cases we allready have which has an 8in cut out for the mid/bass driver.

any help appreciated.
thanks.

 

[kelticwizard]

Can you give us the dimensions of the speaker? If you don't want to mess with inside dimensions, just give us the outside dimensions-minus any overhangs-and the thickness of the particle board.

Do you prefer a sealed or a ported design? Does it make a difference?

 

[bostarob]

That cap buffers low frequecies from entering the tweeter. The simplest crossover there is, but not the worst. If done well, it can sound quite good. Chances are, if you buy new drivers, you would need to design a crossover taylored for those drivers anyway. 8" cut out, eh? A typical 8" driver would not fit. The HiVi F8 ($60 US from partsexpress.com) is an 8" speaker with a huge mounting flange. It should fit.
Before one designs a xo, one chooses drivers.
We need cabinet dimentions, or volume if you can multiply.
-andy

 

[Thatch_Ear]

Before you do anththing are the speakers blown out ,or is it just the paper breaking uo around thr edges.If it just blown foam edging sets can buy sets with glue, surrounds and insructions, but if the paper is shot or threre are places where the coil(s) rub you wikk need a complete rebuilding
Is thre any chace that the drivers are painted a bright bleu and have a golf sticker with name Frazier. Those you rebuild.

 

[Kram]

speedy replies, thanks guys

Thatch_Ear
The drivers are well and trully dead but thanks for the idea any way.

bostarob
You seem to think I have mesaured the size of the driver wrong and you are probably right, so can some one tell me how to measure the driver eg from where to where do i measure?

Ok, the internal dimensions of the box are, height 16in, width accross the front 9in and frount to back are 8in which if im correct works out as 1152 cubic inches which = 0.666cubic feet.

The box is not ported and i really dont want to have to make them ported because i dont have a router but if you think it will make them sound much better then i could always see about buying/hiring one.

What do you think about Audax speakers?
There is a shop near me that sells them which would mean i wouldnt have to pay postage and packaging like i would if i orderd from the net.

Final question, how much on average do the parts for a crossover cost?

thank you.

 

[kelticwizard]

Unless you plan on using a subwoofer with these 8's, I suggest a ported design. The ported design allows the speaker cone to move less while producing bass, which gives a clearer sound throughout the midrange.

Danish-made Peerless is always a good place to start your search for a woofer. As a rule, I find that they usually incorporate design items that frequently are only found on more expensive speakers.

The Peerless 850136 is an 8" woofer that has relatively smooth response up to 5,000 Hz. They recommend that you cross over to a tweeter at 3000 Hz. Below is a frequency response chart for an unenclosed 850136. If put into your box, it will be 3 dB down from the midpoint at 55 Hz.

It has a magnetic structure that allows linear movement in a bass reflex enclosure-not every speaker does that. Very low distortion near resonance.

It costs $45 at Madisound in America-but I guarantee you, it is available in England. Probably at a similar price. I mean, they are made in Denmark. So that would be what-about 30 pds? That is within your guidelines.

To find an English dealer, Email the following address:
E-mail: [email protected] Peerless is owned by Dansih Sound Technology. Or perhaps one of the English members here will tell you where he gets his Peerless from.

 

[kelticwizard]

Just for the heck of it, I ran the simulation for this woofer in a box your size on WinISD. In a .66 cu ft box tuned to 47 Hz, (a 3 in diameter pipe of 10.5 inches length), the speaker is 3 dB down from midpoint at 51 Hz.

I can run the same program with metric sizes, if you tell me what metric sizes are available.

The blue line is the midpoint, the green line the -3 dB line.

I am not saying that absolutely this is the speaker for you. By the way, it is 4 ohm-is that a problem? I am just giving you an idea of what is possible. I think this woofer is a good choice, but it need not be the ony one. I am sure that other members have other good choices for you to consider before you buy.

 

[bostarob]

you may not need a router, a hole saw would work fine, assuming you know someone with a drill press. PVC pipe works great for ports.

I don't think you measured wrong, but maybe you were not specific enough. Is that an 8" diameter hole in your box, or an 8" diameter driver? If the latter, I would second the peerless. A fine choice.

A crossover that i would design for this would cost 20 or 25 dollars a speaker. I don't know what that is in pounds, maybe 10-15? This crossover would be a 2nd order topology, (easier than other topologies to make and design, at least to my knowledge) slopes are of 12 dB per octave. It is likely you have no idea what I just said, but we'll talk you through it, be not afraid to ask.
For a simple xo, I would do a basic 2nd order centered at 2k to 3kHz.
Actually, the peerless rolls off nicely at 4.5kHz, so you could simply put a cap of correct value (youll have to experiment)in line with your tweet. As I said before, this can be very good (and cheap!). But your off axis performance will suck(sweet spot speakers).

If I wanted to get a little more complicated, I would consider the 3dB bump in the peerless's response around 1500 Hz. A first order (6dB per octave) low pass centered at 1500 would take care of that. The actual -3dB point would be closer to 2.25kHz. Then for the tweeter, a 2nd order high pass centered at 2.5 to 3kHz (again, you'll have to experiment). I think this would be the best solution.
-andy

 

[kelticwizard]

Yes, deciding what size hole goes to what size speaker can be deceiving, since the hole is often surrounded by an indented groove in which the speaker frame rests.

Complicating matters is the fact that the cutout can vary for different model speakers rated the same size-8 inchers, 10 inchers, or whatever.

For what it is worth, the Peerless 850136 requires a cutout of 184 mm or 7 3/8 inches, minimum. It can be a tad larger than that for ease of installation-the centers of the mounting holes are 206 mm, or 8 1/16 inches, apart. So the hole cutout should be okay if it is between 7 3/8" and 7 7/8" diameter.

One British pound is currently equal to $1.42 American. Mentally, I've always just rounded it off to "about $1.50".

 

[SteveG]

Kram,
I'm not trying to discourage you, but I have experience with what you are doing, and now I know better than to attempt it. It is a difficult way to go to get a good sounding speaker!
If I were in your place, I would consider starting over completely- especially if the speakers are older than 15 or 20 years. If you look at the cabinets, what are they made of? If they are made of plywood, or thin material (less than 3/4") they really aren't worth putting new drivers into- this is even more true if you have to go cutting on them make them fit anyway! It is very unlikely that you will find a direct drop-in replacement that will sound good. All I'm saying is that it is money better spent on something else. You would be amazed at the quality you can achieve if you have a design that uses drivers that really work together, which is much easier to do if you don't have other limitations imposed on you from the beginning.
If, on the other hand, you are interested in keeping the cabinets and you can do a little simple woodworking, I may have another route for you. Cut out the old baffleboard (board where the speakers were mounted) and replace it with a new one made of 3/4" medium Density Fiberboard. Cut braces and brace the cabinet up internally to stiffen it. This gives you more versatility in what drivers you can work with- all you have to contend with is a known cabinet volume. If you're going cheap on the crossover, I would consider finding a mid/woofer with a nice and smooth natural rolloff, and consider running it without a crossover. That way, you can just build a crossover for a tweeter to match it- very simple and has been used in tons of designs over the years (usually with just a cap, as your speakers were).
Also, If I am remembering right, the cabinet volume you have would fit a Vifa P17WJ pretty nicely, and it is a really easy woofer to work with. The only problem may be the price, which is about $35-40 US, but worth every bit. You will also find 10000 crossover designs for this woofer on the 'net.
Just a few thoughts.
Steve

 

[kelticwizard]

With all respect, Steve, I must disagree. Although the standards for speaker boxes have gone up slightly the past 25 years or so, a well-made box is a well-made box.

For a 16" X 9" X 8" box, 5/8" material is certainly adequate. It will be at least as strong as a 2 cu foot box built of 3/4" material. Smaller boxes are intrinsically more rigid than larger boxes. If Kram has a well-made box, and the cutouts fit, I think it is perfectly okay to go with it.

Now if he has crummy little box with thin walls, then yes, putting new drivers in is a waste of time. I think Kram, though, knows a "real" speaker box when he sees one.

 

[bostarob]

My uncle retired an old crappy pair of speakers with rotten foam surrounds. I gutted them, glued a sheet of 3/4" MDF over the existing baffle, and proceeded to put new high quality drivers in. Before, the box was ok, now it's rock solid. This way, you can use any driver you want.
This is a possibility, not a suggestion. First, Let's see what we're working with, the wizard is probably right, we may not need to do any woodworking at all.
-andy

 

[Kram]

Hi,

Ive made some more measurements of the driver cut out, this time in metric as ive never really used inches to measure anything before.

the diameter of the hole is184mm, the width of the rim is 15mm and the width of the rim and the hole together is 214mm. I hope this will sort out any confusion about the size of driver the case will acept.


the boxes are strong, quite heavy and the walls are thick.

Now im sorry to tell you that im going to have to lower the amount i can spend to 20-25 as i can not really afford 60 pounds on a pair of drivers.


now i feel i must tell you that these speakers are not for any specially designed listining room, just a normal living room so i dont think they will have to be absolutly perfect but obviously i dont want them to sound bad.

again any help appreciated,
thanks.

 

[kelticwizard]

Well, let's get our goal right. You can spend 25 pds for each of two woofers, or 25 pds total for the two?

And tweeters-can you spend extra for them, or are they included in the woofer price?

Just give me an idea of what the limits are of the project in total pds. Bearing in mind that one British pd = $1.42 American for American contributors to this thread.

Incidentally, that cutout would fit the Peerless 8" woofer perfectly. Oh well. I'm sure it would fit most 8 inch speakers just as well.

 

[sianturi]

Kram,

I've checked Peerles 850136 price. It is Euro 42.55/each in www.audiocomponents.nl (excluding shipping & handling charges-- ship from netherland). I don't know if it fits your budget, but they usually give discount if you pay in advance (such as telegraphic transfer). Hmmh... I checked the freq response curve for that driver... very nice.

 

[sianturi]

Oops sory... I didn't notice Keltics has attached the freq resp. curve. Got very slow connection here....

 

[Kram]

kelticwizard

I am willing to spend around 25 pds each for the drivers. As for tweeters i would like to pay less, around 15-20 pds each and 10-15 for the crossovers if thats possible.

42.55 Euros = 27.50 UK pounds according to www.xe.net/ucc/

I would be willing to stretch to 27 pounds for the peerles drivers but as yet have not recieved an e-mail back from them to say how much the postage charges will be. If its too much i will have to look for another driver so please keep you suggestions rolling in

someone mentioned putting a port in the speakers case, this would not be a problem as i can get access to a drill press and hole saws. but i would like to know how big a port should be and where does it go?

thank you.

 

[kelticwizard]

Kram:

The port can be anywhere between 2" diameter to 3" diameter. That is between 50 and 75 mm. Let me know what the inside diameter of the pipe you choose is, I will run it through WinISD and tell you the proper length.

You can put the port pretty much anywhere you want. Most people prefer to put it low, either in the front or the back. It really does not matter.

 

[bostarob]

Go with a 75mm port, if it isn't too long. Bigger is better, in this case.
Can you get 3" inner diameter pvc piping?
This works great for ports and will fit tightly in a 3.5" hole.

Can you afford the peerless? It is the best choice. If you get this, maybe we could get cheaper tweeters.
What size is the tweeter hole?
Vifa D19TD is cheap, among other vifas. Also look at audax, and peerless.
Seas has a tweeter for $17 at partsexpress
-andy

ps-a no name brand tweeter would probably do you fine.

 

[kelticwizard]

Bostarob:

I 'm afraid that Parts Express, as good as it is, doesn't do our UK audiophile friends much good. Someone else called up about a subwoofer amplifier, and by the time he got done with shipping, Value Added Tax and whatnot, the price was jacked up quite a bit.

Might be worth it if Parts Express is selling a closeout for something like $12. Short of that, I don't think it will make Kram's budget.

By the way, Kram, here are some UK mailorder houses that might do you some good.

Wilmslow Audio
http://www.wilmslow-audio.co.uk/
and
https://secure.wilmslow-audio.co.uk/acatalog/Wilmslow_Audio_Drive_Units_2.html

Maplin
http://www.maplin.co.uk/

BK Electronics-HIGHLY RECOMMENDED
www.bkelec.com

Wilmslow has the Peerless, but at a high price. It also has Monacor, more about that later.

Maplin has some Audax, one model looks sort of passable.

BK Electronics is highly recommended by people I have talked to over there. They don't have anything that can help this project, but check them out and remember them for the future.

A possible cheaper alternative is the Monacor SP-215. Wilmslow has it as 25 pds or so, but since the Peerless is expensive at Wilmslow, maybe the Monacor can be had cheaper somewhere else in Britain.

Finally, if Kram can find a good deal on an 8 inch , either locally or on the net, let us know and we can tell him if it will suit his needs or not. We can find the important info on most speakers on the net, if you know where to look. Maybe someone will put something up on special. He mentioned a local Audax dealer.