using Dayton Reference 10's in a tower?

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KU40
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Postby KU40 » Sat Mar 03, 2007 5:24 pm

kevox wrote:Oh....so how would I make (1) 8 ohm tweet and x number of midranges wire to 4ohms total?



well, the single tweeter would have to be 4 ohms to begin with. but 300 watts on it would be ridiculously overkill, so 8 ohm would be fine. Even 150 is way more than enough.

and to get the 4 ohm for the mids, I feel like you know this. Two 8 ohm mids in parallel, four 4 ohm mids in series/parallel, etc.

It's ok to have a 4 ohm mid section and an 8 ohm tweeter. You just have to make the crossover accordingly.
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Atomic Fusion
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Postby Atomic Fusion » Sat Mar 03, 2007 7:34 pm

kevox wrote:Alright man....I like those suggestions:) How much air space do you have for your (2) 7" Reference speakers? Ported, correct? What size is the port? I'm guessing, since my little low-excursion Infinity 6.5" utilizes a 2" port that I should go with a good 3" flared port for a pair of Reference 7"s?


I don't know the first thing about crossovers (yet... I'm hoping to fix this problem while at Mobile Dynamics;)) so it would defintiely be nice to spend less on a 2-way that would still "rock my socks off" then a 3-way.

What do you think of 4 7"s per tower though?:D hehe I figure two things...
1. I like going overboard when it's not too costly and 4 7" mids definitely would be.
2. Those mids are only rated for 60w RMS a piece and I have an available 300w RMS @ 4ohms PER SIDE so I'd really like to take hold of that power;) Plus with 4 I can wire them series/parallel to a single 8 ohm load and, with the 8ohm tweet, the whole tower will wire right up at 4ohms whereas with just 2, it'd only go down as far as 6ohms. I realize that's not a vast power difference (about 70w) but it's less power AND less woofage:p

haha seriously....any reason you wouldn't go with 4 7" per side other than cost? Man that sounds TIGHT:D


My towers are around 3 cuft each, IIRC. 3" port that is 5" long (again going off memory, although I do know factually that it's a 3" port)

If you REALLY want to use four 7" drivers per side, your best option is a 2.5 way system rather than a 3-way system. By bandpassing the midrange drivers, you will eliminate their low end response, you'll have to enclose them, and you've essentially come full circle.

A 2.5 way system in this case would run two of the woofers in a conventional 2-way sense, playing from 20-2,000 Hz, or whatever xover point you'd use for the tweeter. The second pair of woofers would be equipped with a simple coil to taper them off around 1000 Hz.

The reason for doing this is baffle step compensation. Conventional speakers brought out from the wall a bit suffer from a loss in the low frequencies due to the changing of the space from one frequency to another. Low frequencies wrap around the enclosure and fill the entire room, thus causing a loss of energy at any one point. Higher frequencies only radiate in front of the speaker, which means there is more energy at any one point (in front of the speakers) at high frequencies. The transition point is directly related to the dimensions of your speaker's baffle, usually the width (as it is the smallest dimension).

There's two ways to fix this problem with a passive crossover. One is using a compensation circuit, which shelves down the high frequencies to match the attenuated output of the low frequencies. An excellent option, but lowers the effeciency of the speaker as a whole. This is what my speakers have, and contributes a great deal to their outstanding bass response in music.

The second way is with a .5 way system (2.5, 3.5, whatever), which uses a second woofer (or in this case, pair of woofers) with an inductor. The inductor allows the second driver(s) to fill in the bottom end, and then taper off as the frequency increases.

Your quad driver tower, built in this way, will have full baffle step compensation (provided you do it right) like my towers, but will be 6db more sensitive. They will have very potent bass and excellent output potential.

If you wish to do more research, Google "baffle step compensation" or "baffle step" and you should get some links and information.

Adam
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Atomic Fusion
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Postby Atomic Fusion » Sat Mar 03, 2007 7:39 pm

kevox wrote:Oh....so how would I make (1) 8 ohm tweet and x number of midranges wire to 4ohms total?


You don't... You're grossly oversimplifing impedance.

The impedance as you are speaking is simply a nominal level published by manufacturers.

In reality, impedance varies widely based on frequency.

Your average speaker has an impedance in the heart of its frequency response that is around it's 'nominal' load. At resonance frequency, impedance spikes up to a huge number, often 40 ohms or more. At higher frequencies, impedance starts to rise again as the driver moves out of its response range,

A speaker with a 4 ohm woofer load and an 8 ohm tweeter load (nominal) will simply reflect those characteristics in the impedance chart. Power sharing will be different, but proper crossover design will deal with this.

Adam
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kevox
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Postby kevox » Sun Mar 04, 2007 2:39 am

Atomic Fusion wrote:Power sharing will be different, but proper crossover design will deal with this.

Adam


Ah so basically what you're indicating is that if I give the mids an overall 4ohm nominal impedance and leave the tweet at 8ohms (I don't care for a lot of power to the tweet anyways...not like it can do much more with twice as much power unlike a midbass or midrange...) that they'll receive the bulk of the power (say 300w) and a smaller amount will then be delivered to the tweet due to its higher nominal impedance? Sounds good to me...thanks so much man.
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Atomic Fusion
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Postby Atomic Fusion » Sun Mar 04, 2007 12:00 pm

kevox wrote:Ah so basically what you're indicating is that if I give the mids an overall 4ohm nominal impedance and leave the tweet at 8ohms (I don't care for a lot of power to the tweet anyways...not like it can do much more with twice as much power unlike a midbass or midrange...) that they'll receive the bulk of the power (say 300w) and a smaller amount will then be delivered to the tweet due to its higher nominal impedance? Sounds good to me...thanks so much man.


Well, the mids would receive the bulk of the power anyway, but a tone played at, say, 8000 Hz will result in (nominally) a watt of output to the tweeter, whereas the same 'volume level' with a tone played at 500 Hz will deliver two watts to the woofers.

I need to qualify these statements a bit more... The only problem with this arises that the woofers gain 6db in sensitivity over their base sensitivity (which I'm sure you know). If the tweeter has a lower nominal sensitivity than the two woofers, this can cause problems. You can pad down an oversensitive tweeter to match a woofer, which is what is commonly done. Now, you can also technically pad down an oversensitive woofer (or woofers), but it's not really considered a good thing to do as you are negating some benefits of having multiple woofers, and the components needed to do this will need to be very large in value.

Your quad woofer system, even with the .5 way setup, will have a woofer sensitivity of around 97db/1w/1m... You need to find a tweeter which will match that for the best result, and that will be hard to do. You might want to look at a planar ribbon to deliver that sort of sensitivity.

Adam
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Postby X-OvrDistortion » Sun Mar 04, 2007 12:05 pm

Just a little throw in for Dayton. I have used many different speakers of different sizes and applications. They have never failed to meet my expectations, in any way.
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kevox
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Postby kevox » Sun Mar 04, 2007 9:48 pm

Atomic Fusion wrote:My towers are around 3 cuft each, IIRC. 3" port that is 5" long (again going off memory, although I do know factually that it's a 3" port)

If you REALLY want to use four 7" drivers per side, your best option is a 2.5 way system rather than a 3-way system. By bandpassing the midrange drivers, you will eliminate their low end response, you'll have to enclose them, and you've essentially come full circle.

A 2.5 way system in this case would run two of the woofers in a conventional 2-way sense, playing from 20-2,000 Hz, or whatever xover point you'd use for the tweeter. The second pair of woofers would be equipped with a simple coil to taper them off around 1000 Hz.

The reason for doing this is baffle step compensation. Conventional speakers brought out from the wall a bit suffer from a loss in the low frequencies due to the changing of the space from one frequency to another. Low frequencies wrap around the enclosure and fill the entire room, thus causing a loss of energy at any one point. Higher frequencies only radiate in front of the speaker, which means there is more energy at any one point (in front of the speakers) at high frequencies. The transition point is directly related to the dimensions of your speaker's baffle, usually the width (as it is the smallest dimension).

There's two ways to fix this problem with a passive crossover. One is using a compensation circuit, which shelves down the high frequencies to match the attenuated output of the low frequencies. An excellent option, but lowers the effeciency of the speaker as a whole. This is what my speakers have, and contributes a great deal to their outstanding bass response in music.

The second way is with a .5 way system (2.5, 3.5, whatever), which uses a second woofer (or in this case, pair of woofers) with an inductor. The inductor allows the second driver(s) to fill in the bottom end, and then taper off as the frequency increases.

Your quad driver tower, built in this way, will have full baffle step compensation (provided you do it right) like my towers, but will be 6db more sensitive. They will have very potent bass and excellent output potential.

If you wish to do more research, Google "baffle step compensation" or "baffle step" and you should get some links and information.

Adam


Oh geez; somehow I completely missed this reply....time to read into it some more!
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kevox
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Postby kevox » Thu Mar 08, 2007 9:27 pm

I just got some shipping quotes for ONE tower estimating its weight @ 55lbs just to my friend's house in BC (since shipping internationally would be more expensive and I'm going up to my friend's place only 2.5 weeks after I get back from Mobile Dynamics anyways) and it's $120!!!

Not only that but the guy at MD said I'd have to pay for extra MDF for a project this big so I'm definitely not doing this now. I think I'll just utilize the guys here to give me a solid design and then build the towers at home later on in the summer for like.... $60 rather than $120 + materials for just one! This will at least get the ball rolling though as I will get a crossover design and such.

Now what else should I do for my project while I'm here? I'm having a hard time figuring that one out...since I don't have my car here it's kinda hard to do any fiberglass enclosure for my kicks or anything...
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Postby wagz » Sun Apr 01, 2007 11:35 am

http://www.partsexpress.com/projectshowcase/dr-k-mtm/index.html
heres an example of an MTM design with the reference 7's, its also good to note that this design with these exact speakers has been played around with quite often and you can find many variations on the box size and crossover design. for your application you could do something like this in a 2cuft ported tower tuned lower than the the design mentioned in PE, and not use a sub.

variations on the crossover
http://www.rjbaudio.com/RS180MTM/rs180-rs28-mtm.html

choose your tuning well, eather go low enough that you wont need a sub, or go high enough that you can integrate a sub well into the system (you may have to play around with this).

designing your own crossover is tough, plus you don't know how it will sound until you build it. if your tight on a budget it might not be to your advantage to design and build your own crossover, but if time and money are not a problem then definitely play around.

good luck with your project

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Postby 95Honda » Sun Apr 01, 2007 12:10 pm

#1 Don't put a whole lot of stock in MD for home audio speaker design...

#2 Start with a 2-way, with as simple a crossover as possible and no more than 3 drivers (2 woofers).... Your making alot of work for yourself.....
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