Need Porting?

[daklander]

Hi gang.

The normal places I play are small enough I can get by without monitors but now and again it would be nice so I cut up an old pair of hi fi speakers for use as stage monitors.

I used a 10" woofer and a dome tweeter and an unknown crossover I had laying around. I cannot find the TS information.... The internal volume is now approximately 2214 cubic inches with internal dimensions of 12.5x12.5x15.5 before the angle cut. I've put one together temporarily and hooked it up to my garage stereo and it sounds pretty good.

The questions...

Should I port it? What size diameter and a good starting length? Will it make that much of a difference? Should I just seal it?

Where should I place the batting?

What do you think about pickup bed liner material for covering it?

I still have to install the grill, carry handle and maybe a pole socket.

[el_tonto]

I wouldn't port it. It's a bit hit-and-miss without the speaker params, and porting is really only for tuning and increasing the bass response, not for overall volume. A sealed enclosure will have tighter bass, and you probably don't want too much bass in a monitor anyway IMO.

[daklander]

 

I wouldn't port it. It's a bit hit-and-miss without the speaker params, and porting is really only for tuning and increasing the bass response, not for overall volume. A sealed enclosure will have tighter bass, and you probably don't want too much bass in a monitor anyway IMO.

 

 

OK, Thanks. I was leaning toward doing without the port 'cause the thing as pretty good bass as is. Certainly good enough for my acoustic needs and seems like it'll handle my Porch Board pretty well too.

 

I plugged it into my PA and fired up the acoustic guitar through it. It's going to be too harsh on the top end for the acoustic guitar. Will the batting help tone down the high end? I temporarily placed a regular tweeter in place of the dome tweeter and that helped the upper end but I'd like to keep the dome tweeter if the batting will tame it.

[Doctorx]

You might want to replace the tweeter with a piezo tweeter. Parts Express has high powered ones that cost around $12. It would be more efficient and more suitable for live music.

 

About the bass response, how much do you need, really? If you are just running vocals and maybe some guitar there are no frequencies low enough there to need amplification. I built a couple of mini monitors with 5 inch speakers for vocals that work great.

 

good project. good luck,

 

Regis

[Slaymoar]

If your goal is to get a massive specific frequency low-end boost, then porting is the answer. I don't think porting is necessary in your situation. I think ported boxes never sound right, but thats just my opinion.

 

Using a sealed box seems better, since you will get a natural sound with plenty of mids on tap. I'm not sure how your tweeter is built, but if you go for a sealed enclosure, make sure your tweeter is isolated from the 10" sub.

 

-D

[isaac42]

I agree with those who say not to port it. I don't see how that would help in your situation.

 

I strongly disagree with Doctorx. Piezoelectric tweeters are efficient, but very harsh, especially when not crossed over corrctly, and it's a good bet that the generic crossover you have is not designed for a piezoelectric. If your problem is that the high end is too harsh, switching to a piezoelectric is likely to make things worse rather than better.

 

It's possible that the harshness in the high end is coming from the woofer, not the tweeter. If this is the case, then stuffing the box might help. In any event, it's highly unlikely to hurt, and is easily reversible. Give it a try.

 

You're in SoCal. Lots of knowledgeable, experienced speaker folks there. You can find them through DIYSpeakers.net. My guess is that you're going to have to tweak the crossover, and you'll need help with that, more than you're likely to get here.

[tedmich]

 

I agree with those who say not to port it. I don't see how that would help in your situation. I strongly disagree with Doctorx. Piezoelectric tweeters are efficient, but very harsh, especially when not crossed over corrctly

 

 

I agree but Piezos often don't require crossovers as they roll off fairly well at low frequencies. They are helped by an added resistor to give the amp a more stable impedance. Their high frequency performance can be downright dangerous! There are stories of piezo's producing near ultrasonics (>20kHz) at levels which can damage ears, so a low pass can be prudent.

 

The dome tweeter sounds best, although it can't handle much power typically its efficiency is usually way higher than the woofer, so a cheap L-pad (from Partsexpress) is nice to dial in HF.

[isaac42]

 

I agree but Piezos often don't require crossovers as they roll off fairly well at low frequencies. They are helped by an added resistor to give the amp a more stable impedance. Their high frequency performance can be downright dangerous! There are stories of piezo's producing near ultrasonics (>20kHz) at levels which can damage ears, so a low pass can be prudent. The dome tweeter sounds best, although it can't handle much power typically its efficiency is usually way higher than the woofer, so a cheap L-pad (from Partsexpress) is nice to dial in HF.

 

 

Again, I disagree. I know that piezos roll off, but they do so at a frequency lower than they should. To be used well, they need a crossover to limit the low end to 4K or higher. Just because they can be run without a crossover doesn't mean that they should be.

[daklander]

Thanks for the help so far guys. I'm going to pad the box later today, isolate the dome tweeter and give it another test. If that's still too harsh I'll use the standby tweeter for now.

[tedmich]

 

Thanks for the help so far guys. I'm going to pad the box later today, isolate the dome tweeter and give it another test. If that's still too harsh I'll use the standby tweeter for now.

 

 

 

You may just need to dial back the tweeter!

 

Most tweeters are too efficient compared to woofers, some can be ~100dB/watt while the woofs are closer to 90dB/watt thus the high end often needs taming. This can be done with 2 power resistors , one parallel one in series, known as an attenuation network with a fixed attenuation (3/6/9 db are common) OR a simple Lpad which is adjustable. Partsexpress has these for ~$10, just match the tweeters impedance (8 or 4) and pick one which will handle the power (50w usually OK) then you can dial in the HF; more for a carpeted room/bass, less for a tile floor/accoustic guitar.

[daklander]

 

You may just need to dial back the tweeter! Most tweeters are too efficient compared to woofers, some can be ~100dB/watt while the woofs are closer to 90dB/watt thus the high end often needs taming. This can be done with 2 power resistors , one parallel one in series, known as an attenuation network with a fixed attenuation (3/6/9 db are common) OR a simple Lpad which is adjustable. Partsexpress has these for ~$10, just match the tweeters impedance (8 or 4) and pick one which will handle the power (50w usually OK) then you can dial in the HF; more for a carpeted room/bass, less for a tile floor/accoustic guitar.

 

 

Hmmmm, I have a pair of three way crossovers that are adjustable. Could I run both low and mid to the 10" woofer and the high cross to the tweeter?

Thanks for the information on the Lpad. That may be the key.

[Doctorx]

The reason I suggested using a piezo is that it looked like the OP was trying to keep the budget low. Plus, it looks like he is using a hi fi tweeter, and if so it won't last long in a live sound situation, no matter what the crossover.

 

I've used piezos for years with great success. You can put a cap inline with them to pad them down and a resistor to limit the high end. Here is a detailed essay from Parts Express about piezo applications, it is very useful.

[daklander]

 

The reason I suggested using a piezo is that it looked like the OP was trying to keep the budget low. Plus, it looks like he is using a hi fi tweeter, and if so it won't last long in a live sound situation, no matter what the crossover. I've used piezos for years with great success. You can put a cap inline with them to pad them down and a resistor to limit the high end. Here is a detailed essay from Parts Express about piezo applications, it is very useful.

 

 

You nailed it. This project, at this time, has to stay within what I have on hand. No money.

It is, number one, a learning project and secondly will get me something I can use as a stage monitor when needed. I am using hi fi tweeters and the woofer was designed for use in automotive audio systems. Power going in won't be and issue since these gigs are solo acoustic gigs in small venues or outside within a limited area. If the tweeters fail I have more on hand. Later, when funds become available I can always go a different way or even just scrap these and make a purchase if I can't get the boxes to sound as good as I want. Actually I think it's pretty close.

 

Thanks again for the thoughts and suggestions guys. It's all a huge help.

[WRGKMC]

For a solo gig you may want to go with hi fi components. Unlike a rock band where they need to cut through the mix with horns, a full Frequency design may be the ticket to getting a fuller sound. It may aid the adjustment of your PA and fill in some reflective sounds the PA alone doesnt produce.