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Discussion Starter · #1 ·
Dear Wise ones,

I am a car audio guy who is dipping his toes into home audio speaker building. I have built many subwoofer enclosures in the past and have a decent grasp of home audio. I've also worked in radio broadcast so i am very familiar with what a good speaker sounds like, so your efforts will not be in vain.

Basically the deal is this. I have a set of drivers and tweeters (new stuff) that a friend gave me. I would like to build a nice set of tower speakers for my living room. I do not have specs on the tweets but they are 1" silk domes. The drivers are (cheap) GRS 8PR-8" speakers with the TS parameters are as follows.

Specifications: • Power handling: 65 watts RMS/90 watts max • VCdia: 1-1/2" • Le: 1.07 mH • Impedance: 8 ohms • Re: 7.58 ohms • Frequency range: 40-5,000 Hz • Fs: 52 Hz • SPL: 85 dB 1W/1m • Vas: 0.76 cu. ft. • Qms: 4.77 • Qes: 1.45 • Qts: 1.11 • Xmax: 3 mm • Dimensions: Overall diameter: 8", Cutout diameter: 7-5/16", Depth: 3-7/16".


Ideally i would like to build some 5ish foot tall towers. Ported would be preferred, just because im gonna have to try to maximize the bass response from a driver with only a 3mm xmax but Id be fine with sealed. Folks, any help would be appreciated. If you guys could give me some sample boxes that would be awesome.

Thanks so much.
 

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Welcome to HTS! :wave:

You should answer a couple honest questions before we can help you the best. 1) Are you limited to using the drivers that you were given? 2) Is your goal a functioning first DIY speaker project, or is your goal to put a lot of time and work into making something that sounds superb?

For a DIY speaker system you need to have not only T/S parameters of the woofer, but also full range frequency response and impedance data for the drivers that you are wanting to use. Designing a crossover at the very least takes several hours of simulation and tweaking, and that's if you happen to have a set of drivers that play nice. If you answer no to question 1 and agree with the first option of question 2, it is still possible to continue onward and make a speaker system with what you have.
 

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Discussion Starter · #3 ·
Thanks so much for your quick response. Answers to your questions

1) I am not technically limited to the drivers i have, but would like to keep this cheap (ill go big later when i know what im doin). Also, I already have a crossover (2 way, the original that was paired with the tweeter in the original old altec lansing speaker ) so if i go to a 3 way cabinet then i have to buy/build a new crossover....which id like to avoid.

2) Indeed, my goal is a first time functioning DIY speaker. Im not looking for Focal performance....just decent sound and a chance to learn some enclosure building for something other than a sub.
 

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Thanks so much for your quick response. Answers to your questions

1) I am not technically limited to the drivers i have, but would like to keep this cheap (ill go big later when i know what im doin). Also, I already have a crossover (2 way, the original that was paired with the tweeter in the original old altec lansing speaker ) so if i go to a 3 way cabinet then i have to buy/build a new crossover....which id like to avoid.

2) Indeed, my goal is a first time functioning DIY speaker. Im not looking for Focal performance....just decent sound and a chance to learn some enclosure building for something other than a sub.
The crossover you have will most likely work electrically, but it's going to be completely incorrect for those drivers. Crossovers are tailored for specific drivers, their sensitivity, any peaks or dips in response, their impedance plots (drivers aren't resistors), baffle size, driver offset, et cetera.

If you're prepared for it to sound a bit like what you hear on the shelf at a big box store in the 30-50 dollar range, go for it. Music will come out of it, whether or not it's pleasant is going to depend on just how different your existing crossover is from what the drivers should have once all their parameters, cabinet and ctc are taken into account.
 

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Discussion Starter · #5 ·
I found that the crossover is spec'ed at 2500hz. What do you think would be an appropriate box volume ported and sealed?
 

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What DrDyna said is exactly right, re-using another crossover will indeed function as a speaker but with varied results that will never purpass marginal. The "2500 Hz" crossover point is only valid for the original drivers, it would ahve to be simulated (a decent amount of work) using the exact crossover component values in order to see what it would be like for your drivers.

Yikes, so I was just looking at the specs of your 8" GRS driver. Having a Qts that high, it is not going to model very well. It would be best off in a large sealed box (1cuft or bigger). Going vented the box would need to be very large and even then the response is not what an ideal response looks like (3cuft @ 30Hz, 3"x5" round port). If you go sealed, fill fully with stuffing. If vented, line the walls with foam.

If you insist on continuing, take your pick from either of those alignments. Not designing and simulating a proper crossover is your choice as long as you understand the caveats, hopefully it will inspire you to try it in the future :) Without a crossover design, you won't need to worry about the dimension of your baffle (front speaker panel). You should make sure to mount your woofer and tweeter as close together as possible, and it's also better to mount the tweeter off-center, then mirror your left and right sides. Just put the tweeter so high off the ground as to be right at listening height.

Do you have ANY info at all on the tweeter? I am thinking that it may help your effort to add in a zobel for the woofer and perhaps some attenutation on your tweeter. It's guess work but it could help you integrate your previously used crossover.
 

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I'd go with the vented alignment there, room gain might help you out a bit. I'd also add that placing them back up against the wall might help as well.

If you're curious to start learning about crossover design, I'll point you here:

http://www.troelsgravesen.dk/crossovers.htm

as well as here:

https://sites.google.com/site/undefinition/diy-mfaq

If you don't have any data for the tweeter, it might be best to select new ones. You can probably get a fairly decent pair for not very much money that will come with specs. We may even be able to help you with a basic crossover to get started with, but with a tweeter that has no markings or data, it's nearly impossible for us to help because we can't hear it ><
 

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Awesome crossover design site!!

Related to tgauger, I do also come from the Car Audio world but started as a home speaker "fiddler" when I was in my pre-teens.. One thing I've read and discovered is that you need to have the speakers -ear level- to maximize the listening experience, talk about on-axis/off-axis response graphs that the very experienced members here are suggesting... I would try to ditch the tweeters in favor of new known ones (partsexpress.com), they are not very expensive and at least you would know the parameters (basic response, sensitivity and impedance) so you can properly make a crossover for those... Any other thing you do would be a shot in the dark..

If you still want to stick to your drivers, hook everything together (no box yet) and give them a listen, my guess is that your experience will not be very pleasant... If it is, you miiiiight just be one of the lucky ones!! :unbelievable:

Just my 2 cents...

BTW: Even though that GRS woofer models -not so good- for us car-audio guys it would actually be OK to listen to...:bigsmile:
 

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Welcome to HTS! :wave:

You should answer a couple honest questions before we can help you the best. 1) Are you limited to using the drivers that you were given? 2) Is your goal a functioning first DIY speaker project, or is your goal to put a lot of time and work into making something that sounds superb?

For a DIY speaker system you need to have not only T/S parameters of the woofer, but also full range frequency response and impedance data for the drivers that you are wanting to use. Designing a crossover at the very least takes several hours of simulation and tweaking, and that's if you happen to have a set of drivers that play nice. If you answer no to question 1 and agree with the first option of question 2, it is still possible to continue onward and make a speaker system with what you have.
Very well said! I totally agree with all your points! :T
 
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