Mixing 16 ohm tweet with 8ohm woof?

[davidiliyn]

Hey all, new here and have learned so much from everyones posts.
I am however in a little bit of a pickle. Im a woodworker and wanna be diy electric guy.

I just finished building 4 custom boxes for a local bar. They are supplying the speakers and need me to get them up and running.

Woofer 12" 8ohm magnavox (583965)
Tweeter Electro voice 16ohm T35

My dilemma is building a crossover that will play nice with both speakers.
I have a few simple xovers from amazon goo.gl/Xr39iJ but don't believe they would be safe to run them on.
I would love any and all advice you guys have!

 

[bowtie427ss]

You have agreed to build a bridge, and apparently you don't know the first thing about bridges.

First problem i see is that the proposed speaker components have usable bandwidths that likely do not meet each other and will leave a hole in the mid-range, the most important part of music or speech.

The amazon crossover is total crap, they don't even list the crossover frequency, total crap.

The T-35 is probably one of my least favorite devices ever given the name "tweeter". The raspy, spitty sounding things need to be brought in high, 8khz or above. They don't have good upper extension like a tweeter should have. Most folks don't even know how to mount them correctly and position them in the horizontal aspect. If you like i can list many more negative attributes of them.

To build a "proper" box with "proper" tuning for the woofers, you really need to know their T/S parameters, and plug them into a box modeling program. That will give you a box volume and porting specs to work with.

Or, you can do what many still do, just wing it and build a box to stuff the components in, slap a 2.2 uf cap in series with the tweeter and call it good. Are they really going to know the difference in a bar that has this kind of budget for a sound system?

 

[elnaldo]

To make a proper crossover you need to measure your drivers, at least the freq response of your woofer, and see how they overlap. Many people run th ewoofer full fange, and cross the tweeter where the woofer starts to roll off. Then add a resistor to tame the tweeter output, to match the woofer output level.

 

[gdmoore28]

Welcome to the site, David. You've entered into a project where you cannot win. The owners have given you simple crap components to work with. Are they willing to spend any money to buy some components that will give you a fighting chance? Get them to buy this:

http://www.parts-express.com/eminence-beta-12cx-12-coaxial-driver--290-504

Add in the recommended horn driver:

http://www.parts-express.com/eminence-asd1001-1-hf-titanium-horn-driver-1-3-8-18-tpi--290-525

And the recommended crossover network:

http://www.parts-express.com/eminence-pxb2-2k5cx-2-way-speaker-crossover-board-2500-hz--290-635

Assemble in the boxes, wipe your brow, breath a sigh of relief, then start doing LOTS of reading before undertaking something like this. We've all been there, done that (no shame, no excuses), and this is what it comes down to. Save money, headache, and time, and do it right the first time.

(On the other hand, going at it like you are will provide tons of fun, frustration, learning experience, pride, and embarrassment. Your choice.)

In the meantime, go here (http://www.diyaudioandvideo.com/) and start your education.

Have Fun!!!!!

 

[drbiggles]

Hi David,

I echo gdmoore28's words x 9,000,000.

That being said, if you've already cut the baffles for the drivers and have them mounted? I would suggest running the woofer wide open and putting a 4uF cap on the T-35 and calling it done. Let them know that this is what the drivers they supplied sound like. If they'd like better, suggest gdmoore28's path to success.

We say these words to you because we've all been down this path.

Biggles

 

[davidiliyn]

Appreciate the honest responses. I needed that! The woofers are trash and of course their budget is non existent... I told him if this rig dies (which it will) we can always retrofit another system in the box and make a plate for the tweeter if we buy something different.
Thanks so much once again! I will keep you updated on the trash sound rig!

 

[sqlsavior]

You can think of, diagram, and even wire the crossover as two separate circuits, sharing a common input (+, -). So, just use the calculator or formula separately for each driver, based on its respective nominal impedance. I would put a 12 db/octave on the bottom of the tweeter however, to further limit excess LF energy to prevent diaphragm damage from over-excursion. The tweeter is likely much more sensitive than the woofer, so you will want to include a 16 ohm L-pad between the crossover and the tweeter, to be able to adjust the balance of bass and treble.

The main unknown to me are the woofers, so I don't know how the result will end up sounding.

Contrary to other's opinions, I'd say the T-35 tweeters, for a saloon, are just about PERFECT, and not at all "crap". They are rugged, will go plenty loud without strain, and nobody in the bar will give a crap about some audiophile's objections. T-35s are fine tweeters, especially considering the application.

 

[2020]

You have agreed to build a bridge, and apparently you don't know the first thing about bridges.

First problem i see is that the proposed speaker components have usable bandwidths that likely do not meet each other and will leave a hole in the mid-range, the most important part of music or speech.

The amazon crossover is total crap, they don't even list the crossover frequency, total crap.

The T-35 is probably one of my least favorite devices ever given the name "tweeter". The raspy, spitty sounding things need to be brought in high, 8khz or above. They don't have good upper extension like a tweeter should have. Most folks don't even know how to mount them correctly and position them in the horizontal aspect. If you like i can list many more negative attributes of them.

To build a "proper" box with "proper" tuning for the woofers, you really need to know their T/S parameters, and plug them into a box modeling program. That will give you a box volume and porting specs to work with.

Or, you can do what many still do, just wing it and build a box to stuff the components in, slap a 2.2 uf cap in series with the tweeter and call it good. Are they really going to know the difference in a bar that has this kind of budget for a sound system?

Bowtie, I have read many of your posts and greatly respect your opinion. I am curious what vintage horn tweeter you like? Seems like T-35s sell for less than $100 each. Anything in that price range?

 

[bowtie427ss]

When you start talking "vintage" and "tweeters", there are not a lot of options. T-35 was probably the first tweeter mass produced that was able to play at the sensitivity levels of the large, Iconic style speaker systems of the golden era. In it's day, it had few competitors. Maybe, the JBL 075, but i have never found a way to love 075's either. The T-35 is quite tamable, and some folks accuse me of being a bit more critical of them than i really am. Raspy and spitty they are. But, i don't think i've ever said they sound like a cheese grater. That sentiment would be reserved more for certain manufacturer's implementation of them(can you read this PWK?)

I always keep my eyes peeled for Coral H-1 and Calrad CT-4/Pioneer PT-2 horn tweeters, for now they can still be bought under the radar. But, threads like this have a way of bumping the price of this kind of gear and because of the scarce supply, and memorialized data, the price never seems to come back down.

For lower powered systems i still like the old style, aluminum, 2 x 6 horns made by Foster for Tandy/Radio Shack(40-1228). Not the last word in extension, but they are smooth and what they do, they do well.

 

[2020]

When you start talking "vintage" and "tweeters", there are not a lot of options. T-35 was probably the first tweeter mass produced that was able to play at the sensitivity levels of the large, Iconic style speaker systems of the golden era. In it's day, it had few competitors. Maybe, the JBL 075, but i have never found a way to love 075's either. The T-35 is quite tamable, and some folks accuse me of being a bit more critical of them than i really am. Raspy and spitty they are. But, i don't think i've ever said they sound like a cheese grater. That sentiment would be reserved more for certain manufacturer's implementation of them(can you read this PWK?)

I always keep my eyes peeled for Coral H-1 and Calrad CT-4/Pioneer PT-2 horn tweeters, for now they can still be bought under the radar. But, threads like this have a way of bumping the price of this kind of gear and because of the scarce supply, and memorialized data, the price never seems to come back down.

For lower powered systems i still like the old style, aluminum, 2 x 6 horns made by Foster for Tandy/Radio Shack(40-1228). Not the last word in extension, but they are smooth and what they do, they do well.

Thanks for the advice! I have a single Pioneer PT-3, but will keep an eye out for the ones you mentioned. Coral and Calrad never occurred to me at all.

 

[bowtie427ss]

Thanks for the advice! I have a single Pioneer PT-3, but will keep an eye out for the ones you mentioned. Coral and Calrad never occurred to me at all.

I Mistakenly implied in my previous post that the Calrad was a re-badged Pioneer, it's a re-badged Coral. I suspect the Pioneer was probably also sold under other names. Both tweeters were used in some OEM speaker systems as well as sold as stand alone add-ons with nifty little chrome stands.

The last two pics are the Pioneer.

 

[toxcrusadr]

Welcome to AK davidiliyn.

Great advice here...I think the simple capacitor for a crossover is a great way to start. Cheap, probably gets the most out of your drivers (such as they are) and helps smooth over some of the deficiencies. Not a lot to lose!

On what part of the planet might you be located?

 

[toxcrusadr]

Oh, for future reference, it IS possible to mix impedances but it does affect the crossover frequency. There are online calculators that allow you to specify the driver impedance and crossover frequency and get cap/inductor values. It's best not to stretch things too far (4 and 16 ohms for example) but the main thing is the relative sensitivity (output in db/watt) of the drivers. You want them to be fairly similar to keep the speaker balanced. Which brings us to: if the Frankenspeaker you're building sounds shouty or tinny, there are things that can be done.

 

[2020]

I Mistakenly implied in my previous post that the Calrad was a re-badged Pioneer, it's a re-badged Coral. I suspect the Pioneer was probably also sold under other names. Both tweeters were used in some OEM speaker systems as well as sold as stand alone add-ons with nifty little chrome stands.

The last two pics are the Pioneer.

I love those funky little stands

 

[davidiliyn]

Oh, for future reference, it IS possible to mix impedances but it does affect the crossover frequency. There are online calculators that allow you to specify the driver impedance and crossover frequency and get cap/inductor values. It's best not to stretch things too far (4 and 16 ohms for example) but the main thing is the relative sensitivity (output in db/watt) of the drivers. You want them to be fairly similar to keep the speaker balanced. Which brings us to: if the Frankenspeaker you're building sounds shouty or tinny, there are things that can be done.

Thanks mate! I am currently in Oregon. I will finish up the boxes and crossover and post results. Thanks.

 

[4343]

Why go Vintage at all? Just get some new tweeters and decent woofers when they eventually fry the stuff they have.

Personally, I'd go with the standard eWave kit, but that's just me that ran sound in so many bars that damp bar rags are more than I can take of the places. You learn after a while that those that frequent bars are not interested in bass or treble, they just want loud so that they can also get loud. With the right woofer, these could easily become Hi-Fi, but can also get loud enough for 50-100 rowdy alcohol enthusiasts to have a hard time hearing each other, which is all they want anyway.

Here's the waveguide:
http://www.parts-express.com/pyle-ph612-1-screw-on-constant-radiation-horn-1-3-8--18-tpi--292-2572

and the driver:
www.parts-express.com/selenium-d220ti-1-titanium-horn-driver-8-ohm-1-3-8-18--264-270

Build this crossover:
http://www.audiokarma.org/forums/index.php?attachments/econschem-jpg.83308/

Parts list (All from P.E.):
C1 027-422 1 4.7 Microfarad
C2 027-430 1 12 Microfarad
C3 027-406 1 0.47 Microfarad
R1 004-30 1 30 Ohms, 10 Watt
R2 004-16 1 16 Ohm, 10 Watt
L1 255-040 1 0.6 MH, 20 AWG
L2 266-552 1 1.5 MH, Iron Core
L-Pad 260-255 1 8 Ohm, 50 Watt

For a woofer, whatever the bar can afford now could work, at least till they blow it up, which they will if you don't get something with some serious power handling ability. Especially if they don't have a lot of power available to drive it, as the low power amp is the one that will kill speakers the quickest...

 

[davidiliyn]

Thanks for the info everyone. Like I mentioned its for a bar and their budget is non existent. I do think I can get some money out of them for some decent crossovers.
I have made a few quick crossovers and the rig sounded..decent...

The horn definitely needs around -3db of attenuation.
And the driver needs the top end cut off, its a pretty bad sounding speaker.
Sadly I wish they would fork up the money now for a better setup, but Im just banking on these blowing sometime soon...

With that, I would like to get a better 2way crossover for all 4 cabinets, something that might work later on if the rig blows. I like the setup gdmoore28 linked to, would that the crossover he mentioned be sufficient?
http://www.parts-express.com/eminence-pxb2-2k5cx-2-way-speaker-crossover-board-2500-hz--290-635

 

[Switchtech]

Hi David,

I echo gdmoore28's words x 9,000,000.

That being said, if you've already cut the baffles for the drivers and have them mounted? I would suggest running the woofer wide open and putting a 4uF cap on the T-35 and calling it done. Let them know that this is what the drivers they supplied sound like. If they'd like better, suggest gdmoore28's path to success.

We say these words to you because we've all been down this path.

Biggles

drbiggles> I have a question sir.
One last one I promise. I am hoping to install the Knight 820 speaker @ 8 ohms and the Utah H458-X horn @ 16 ohms into one cabinet. Can this be done with a 0.47 uF cap. The amp is a 4ohm amp that also runs fine at 8ohms, “Voice of Music VM 1404” The threads I have been able to research suggest it could be possible.

 

[drbiggles]

drbiggles> I have a question sir.
One last one I promise. I am hoping to install the Knight 820 speaker @ 8 ohms and the Utah H458-X horn @ 16 ohms into one cabinet. Can this be done with a 0.47 uF cap. The amp is a 4ohm amp that also runs fine at 8ohms, “Voice of Music VM 1404” The threads I have been able to research suggest it could be possible.

I think the long and short of it is no. At what frequency do you want to bring your 16ohm horn in? Horns want a second order crossover, no one cap will do.

Biggles

 

[bowtie427ss]

.47uf in series with 16 ohms will give a knee point above the limits of human hearing.

4.7uf would give a knee point around 2200-2300hz, way too low for first order.

If you want to keep it simple, and first order, aim for a 6000-8000hz knee point. 1.2 to 1.5uf will get you there.