A Speaker Dilemma, Please Help!

[MT Speakers]

OK, so I need some help but I do not seem to get much response here. And when i do, there is not much depth to the response. Are my questions to tecknical for this forum? Should I go to other DIY forums? I need you guys to help me out.

Now - I set up 2 speakers and attached the front baffel with masking tape. My friends dad has an old amplifier - ADCOM GFA5802. He let us use it because he thought it was bad. It has not been used for over 10 years. Well, I do not know if it is bad but it seems to work. We wired a IPOD in to it. and then a computer to play CD's. We have been listening to them for 3 days after school.

We played some Taylor Swift, the song International harvester, some cuts from "Brother where art Though" , Garth Brooks and lots of other stuff. Even soom rolling stones.

These speakers sound amazing. Nobody thought these would sound that good. I have never heard seperate bass guitar notes before. People singing sound like they are right there - this is scary. And violins sound like I am at a concert - my Mom takes me to listen to the Cincinnati Orchstra. And these speakers sound about the same everywhere in the room.

I want to finish them. Please, I need some help. I have some more fiberglass insulation. Would it hurt to add more behind the Woofer? Or where would it be best to add some more? Right now my port resonance is 41.78 hertz. I have a setup that can measure port resonance. What is the best frequency to tune these speakers to? Zaph says it should be 44Hertz also he says you can go to 50 hertz. He does not talk about lower. Whats the best?

[brianpowers27]

Generally speaking, you are shooting for a flat frequency response. The tuning is usually done to taste, since bass tastes vary. The lower the tuning the earlier the middle bass is going to lose energy. This lower tuning will gain you some deeper bass at the expense of upper bass. In all practicality you will barely notice a 2hz tuning difference.

[MT Speakers]

Thank you - Thats my issue - I am interested in the best middle bass quality. The speakers will be used for mostly movie watching. For bass we have a SVS PC 13Ultra.

[---k---]

Try this post: http://www.htguide.com/forum/showthread.php4?t=17794

Tuning the bass is very much personal preference. There isn't a "best". That became very obvious to me a few months back when JonW and I got together. He had tuned the bass in his somewhat hot. He liked it. I found it obnoxious. To each his own...

The lower you tune the bass, it may loose some "punch" but will gain more extension. It is a tradeoff. I think many of the people around here like the added extension at the expense of the punch. It is a dryer, tighter bass. Most people who buy speakers from Best Buy are probably the opposite and would like the higher tune. But, like Brian said, the difference in 2hz is small. Noticeable would be the difference in 10hz.

More than likely, seal them up right now and you'll be happy. But, if you want to find the "best for you" it takes a lot of experimenting. Not all a bad thing.

And please understand, I work and can't get to every post. I've taken to just skimming threads and TRY to only answer where I have direct experience with something.

[ThomasW]

OK, so I need some help but I do not seem to get much response here. And when i do, there is not much depth to the response. Are my questions to tecknical for this forum? Should I go to other DIY forums? I need you guys to help me out.

I want to finish them. Please, I need some help. I have some more fiberglass insulation. Would it hurt to add more behind the Woofer?

Here's a thought take the time to read what's been posted. I answered the 'what happens if I add more damping" question in my last post. I also said the current 42Hz Fb was fine for this speaker.

For bass we have a SVS PC 13Ultra

All your questions about port tuning are irreverent because a 80Hz crossover point should be used for the sub. That means it doesn't matter what the port tuning is because the port won't be operating when the sub is being used.

[MT Speakers]

Okay, maybe sometimes I'm dense, but now I understand what you are saying. Bascially that is what I was asking. I realize that the reciever will roll the frequency off below 80 Hz. So, therefore, I want the speakers to be set up so they produce the best sound above 80 Hz.

[ThomasW]

Is there something about my statement saying '42Hz is fine', you don't understand?

The primary thing adding or subtracting more damping will do is make minimal changes in the Fb. And if you add too much damping, it will lower all the output from the woofer. This will change the tonal balance between the woofer and the tweeter.

Since you think we're not technical enough here's some info we haven't covered.

42Hz, 44Hz, 50Hz or whatever, is a rather impractical Fb for any loudspeaker, because there's so much information on recordings significantly lower in frequency (the low E string on a electric bass guitar is tuned 42Hz).

If a system with a highish Fb (let's say 42Hz) is playing loud, and it attempts to play frequencies lower than 42Hz the system can 'unload'. (unloading is when the woofer and the port function out of phase) If or when this happens, the woofer flaps back and forth wildly, that results in it's destruction because the voice coil slams into the back plate.

There are to 2 options to protect the woofers from this situation.

1) build a high pass filter to remove everything below 42Hz. (these are expensive to build )

2) use a sub.

If a sub is used the port Fb of the mains isn't that important because it isn't seeing frequencies at the Fb since those are typically filtered out by the crossover.

FWIW, using a sealed speaker with a sub is a better option than ported, because the natural roll-off of a sealed box is inherently a better match for the crossover used with the sub.

[Dennis H]

Like Thomas said, 42 vs 44 Hz tuning is almost no difference at all. If you don't have box modeling software go to http://www.linearteam.dk/default.aspx?pageid=newdriver (requires Java) and enter Vas=26, Qts=.35, Fs=29 for the driver and Vb=14, Fb=44 for the vented box. Click 'Draw It.' Now change Fb to 42 and click Draw It again. The curves will be so close, it looks like one fat curve.

A few points....

Low tuning is better than high tuning because most rooms boost low frequencies. A speaker that measures flat in an anechoic chamber may boom in a real room so it's often a good idea to design for a mild rolloff -- say tune it in the mid 30s instead of the mid 40s. You can see what happens at the link above. That said, Zaph knows what he's doing so I wouldn't lower the tuning very much without in-room measurements.

Adding more fiberglass will lower Fb further. Your fiberglass is probably a better absorber than Zaph's foam but that's a good thing and explains the 2Hz difference. I'd leave it just like it is.

Like Thomas said, you'll get a better blend to a sub with a sealed box. You can stuff the port with a sock or a nerf football or whatever to seal it up. Again looking at ISD Online, your driver with a sealed box will be about -3dB at 80Hz which is perfect for using an 80Hz crossover in your receiver. You can plug the port when using a sub and pull the plug out when using them alone -- best of both worlds.

Bottom line, you're about done. Don't sweat the small stuff. Close them up and start enjoying the music!

[MT Speakers]

We've been listenening to the speakers alot, they sound good. But at certain times, especially with certain notes on a keyboard, the speakers sounded a little fuzzy. So, we started looking for what the problem might be. We did frequency sweeps, that didn't show anything obvious. We were listening to the speakers, unfinished, just in case we had to make changes. And, we weren't using gasgets behind the speakers.

So, we put in gasgets. Again, we found something laying around that could solve that problem. A brand new gasget maker. They are made out of shelf liner we bought at Lowes. It comes in many colors, we chose black over plaid. It is called easy liner. Gasgets are definately needed!

Second, we bought some Solen 3.3 mH Air Core #14 Awg inductors from Madisound. And used them in place of our home built inductor. That was it. The funny noise dissapeared. The speakers are now awsome!!!!

[JonMarsh]

Sounds like core saturation in your home made inductor. Glad you've got it sorted out and happy with the results! :T

[MT Speakers]

Thank you - at this point I am going to think about finishing my speakers. I decided to just sand and paint with Sherwin Williams Exterior Duration Satin Black Paint. I worked with this stuff because this is what my mom and dad used in the trim of our house. I painted our side garage door and I could not believe how good it looked. But it wasn’t black. If anyone has other ideas please let me know.

Now I want to say that I think my goals were met with this project. I wanted some good speakers but did not have the money for speakers I heard and liked in stores. My dad said he thought I could build good speakers for about $150.00 each. He did not have time to do it but would help. My dad said if I wanted to build the speakers cheep, I would have to take my time and wait for opportunities.

I did a lot of research. I got most of my information from this site. I wanted to make my own design. But I figured out that all y’all probably forgot more about speaker design than I will ever know. So I decided to choose a modest proven design I felt I could build. I also wanted a design I could play with to learn something. That’s why I chose the ZAPH SR-71.

I knew by reading other posts on this site that if I modified a ZAPH design I risked being served HOT and CRISPY. If I was building the ZD5 or the ZRT I would not have made changes.

I needed to make a lot of stuff to keep my costs down. So I tried to make everything myself, except for the speaker drivers.

• I experimented with making my own capacitors with aluminum foil – don’t waist your time – I still can’t figure out how they get that much capacitance in such a little part.
• I made my own resistors – ugly
• I tried making tapered precision ports from PVC pipe, again – so ugly they were funny.
• I made the inductors but replaced then with SOLEN perfect lays.
• The MDF boxes came out really good. Thank you Home Depot.
• I made my own speaker electrical connectors with pieces of fiber glass and 5 way binding posts – these came out pretty good. I glued the tweeter cross over parts to these – saved me some money.
• I made my own speaker gaskets.
• I inlayed GPO3 (a type of fiber glass) into the MDF to improve the sonics of the MDF. I don’t think it did anything except make a lot of work. But my dad wanted to try it because we had this stuff and my mom wanted to through it out. I think we did this because at first we were going to use this instead of MDF.

At this time without finishing I have spent less than $200.00 per speaker.

Now I will try to describe the sound of these speakers. The first time I heard them I realized I never heard anything like this. My dad pointed it out when he said you can close your eyes and see singers and instruments in space. He said from the start he thought something was wrong with the sound but I just wanted to listen to the speakers because of the stereo sound. Then – I can go into a store and hear separate drivers on a speaker. I thought this is what I should hear with the speakers I built. Wrong – these speakers sound like one piece. Its just one thing of sound. I listen to music on my IPOD and hear music in cars and on TV and other music systems. These speakers make sounds that are in the music but I did not hear before. Now when I hear the same music in the car its like I can see little black holes in the sound. I am very happy I built these – I got 2 things – great sounding speakers and a lot of knowledge.

Anyway, that’s it for now. I have to go and practice my French horn for a band concert.

Thank you all for your help and patients. I may have more posts but I will post a picture of the speakers when they are finished.