| Matttcattt |
i am going to make a subwoofer with this driver: http://www.maplin.co.uk/Products/Mo...900&modulelist=
i know this driver is not hifi, and i do not want any driver suggestions. :D
i put the driver specs into winisd beta, and got these curves. yellow is sealed, green is vented. i prefer the yellow curve, but i am going to make test boxes of both to see what they sound like.
my question is about stuffing. what does stuffing do? should i stuff my sub? |
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| kelticwizard |
Well, you are going to get driver info.
The Eminence Beta 15 does not have an extended core or a Faraday ring. That means that in a vented box, as the frequency approching Fb, the cone travels all the way in or out to the end of it's travel. This phenomenon is called "suck-out". At the frequencies near Fb, it essentially shears off half the waveform.
Eminence does make models with extended cores.
Another source for Eminence products in the UK is www.bkelec.com Checkout the prices on the entire Eminence line, Beta included. |
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| pinkmouse |
| quote: | Originally posted by Matttcattt
i put the driver specs into winisd beta, and got these curves. yellow is sealed, green is vented. i prefer the yellow curve, but i am going to make test boxes of both to see what they sound like. |
You're going to build test boxes of 700l and 1100l? I like your style, but you might have problems getting both you and your boxes in the same room at once! ;)
| quote: | | my question is about stuffing. what does stuffing do? should i stuff my sub? |
Stuffing is used to damp the interior of the box, increase the apparent volume, and absorb troublesome wavelengths. In sealed boxes it is generally important to get the stuffing right, and this is done through listening and tweeking.. In vented boxes, stuffing is generally less in volume, and as a general rule, fixed to the cabinet sides to avoid blocking the airflow to the ports. |
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| kelticwizard |
Check out the Eminence Delta 15LF, (make sure it's LF), at www.bkelec.com
Bigger magnet, has extended core so that "suck-out" problem doesn't happen in the deep bass, takes more power, and costs £53, including VAT. You can build a box of 13 cu ft that has an F3 of 30 Hz.
A better deal all around. |
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| Matttcattt |
| quote: | Originally posted by kelticwizard
Well, you are going to get driver info.
The Eminence Beta 15 does not have an extended core or a Faraday ring. That means that in a vented box, as the frequency approching Fb, the cone travels all the way in or out to the end of it's travel. At the frequencies near Fb, it essentially shears off half the waveform.
Eminence does make models with extended cores.
Another source for Eminence products in the UK is www.bkelec.com Checkout the prices on the entire Eminence line, Beta included. |
i meant that i dont want other drivers suggested to me.
so i have to have a sealed box?
| quote: | Originally posted by pinkmouse
You're going to build test boxes of 700l and 1100l? I like your style, but you might have problems getting both you and your boxes in the same room at once! ;)
Stuffing is used to damp the interior of the box, increase the apparent volume, and absorb troublesome wavelengths. In sealed boxes it is generally important to get the stuffing right, and this is done through listening and tweeking.. In vented boxes, stuffing is generally less in volume, and as a general rule, fixed to the cabinet sides to avoid blocking the airflow to the ports. |
700l isnt that big... ...only about 0.9m cubed... ...thats pretty big actually... ...i hadnt though about how big it would be...
any suggestions for stuffing i should try? having to have a sealed box narrows the choises down i suppose...
thanks for the replies. |
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| Ron E |
I wouldnt use boxes that big. I guess isf you have the space and a good back, go for it. ;)
I'd try a 175Liter box with 2 ports - 4" diameter x 6" long.
You can compare sealed and ported in that size by just plugging the ports. |
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| pinkmouse |
| quote: | Originally posted by Matttcattt
ny suggestions for stuffing i should try? |
For that size box, your only real choice is to go for fibreglass roof insulation, (the stuff on rolls, not the slab type), anything else would cost a fortune. Luckily, apart from being a pain to use, it works really well! ;) |
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| Matttcattt |
any more info kelticwizard? does not having an extended cone mean i can only have a sealed box?
the size of the box does not really matter. i dont want to go below 300l as i want the sub to play low bass, and im not really bothered by effeciency. :devilr: i agree that 700l is a bit much though... |
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| kelticwizard |
| quote: | Originally posted by Matttcattt
any more info kelticwizard? does not having an extended cone mean i can only have a sealed box?
the size of the box does not really matter. i dont want to go below 300l as i want the sub to play low bass, and im not really bothered by effeciency. :devilr: i agree that 700l is a bit much though... |
Matttcattt:
If you don't have a extended core, a sealed box is more advisable. The ported will have high distortion at the deep bass end.
The Eminence Delta 15LF has an extended core, the Beta 15 does not.
Even a 15 incher will have trouble putting out super high output at 30 Hz in a sealed box. The ported box will have a higher maximum SPL at it's rated power. I would suggest the ported for more output. However, you can go sealed as an option.
Below is the Eminence Delta 15LF and the Eminence Beta 15 in two identical boxes. I checked the eminence website and found that the Beta 15 is just 1 dB more sensitive than the Delta 15LF, (even though it is listed as 2 dB), so the chart is off by one dB. big deal ;).
As you can see, these two give virtually identical performance in a 13 fT³, (that's 368 liters in Metricspeak:) ), box tuned to 30 Hz. How low did you want the sub to go? |
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| kelticwizard |
| Oops! Here's the chart. |
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| Matttcattt |
| quote: | Originally posted by kelticwizard
Matttcattt:
If you don't have a extended core, a sealed box is more advisable. The ported will have high distortion at the deep bass end.
The Eminence Delta 15LF has an extended core, the Beta 15 does not.
Even a 15 incher will have trouble putting out super high output at 30 Hz in a sealed box. The ported box will have a higher maximum SPL at it's rated power. I would suggest the ported for more output. However, you can go sealed as an option.
Below is the Eminence Delta 15LF and the Eminence Beta 15 in two identical boxes. I checked the eminence website and found that the Beta 15 is just 1 dB more sensitive than the Delta 15LF, (even though it is listed as 2 dB), so the chart is off by one dB. big deal ;).
As you can see, these two give virtually identical performance in a 13 fT³, (that's 368 liters in Metricspeak:) ), box tuned to 30 Hz. How low did you want the sub to go? |
i must have looked at the graph wrong, ported looks much prefereable.
im not really sure how low i would like it to go. i was told before that 20Hz at -3db is very good, but im not sure about how loud -3db is :dead:
looking at winisd beta, the optimised curve with 1108.8l volume looks good to me, but 1000l is huge. the curve is ok (i think so anyway) down to about 600l. what do you think? |
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| kelticwizard |
Matttcattt:
Both are ported in the chart. Only ported systems have Fb. You cannot tune a sealed box, except by making the box bigger or smaller.
I made the chart to show that both the Beta 15 and the Delta 15LF are pretty much the same, except the Delta 15LF is a better made driver and works in ported boxes better. |
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| Matttcattt |
| i meant the initial graph that i posted when i started this thread. |
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| kelticwizard |
Here is a WinISD somulation of an Eminence Beta 15 in a 13 ft³ box, Sealed, and a Delta LF in a 13 Ft³ box, Ported and tuned to 30 Hz.
Quite a lot of extra output between 30 and 50 Hz. |
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| Matttcattt |
| yes a big difference, and the delta is only £15 more expensive... ...maybe ill buy the delta. ill have a look with winisd tomorow, its 1:05 here and i need to sleep :dead: |
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| kelticwizard |
Matttcattt:
Unless you are getting some kind of discount from Maplin's, the Delta 15LF is only £53 including VAT at www.bkelec.com , which is only £3 more than the Maplin's link for the Beta 15.
That is why I mentioned the Delta 15LF when you made it clear you didn't want any recommendations. I figured it was okay to mention another driver if it is the same price, LOL.
Anyway, I'll let you make your own shopping decisions. Obviously I don't know all the facts of your situation.
If you don't mind my asking, where do you plan to put this? From the volumes you mentioned for the enclosure, I almost think you are putting this into a large unused closet. I did that once, by the way. ;) |
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| Matttcattt |
| quote: | Originally posted by kelticwizard
Matttcattt:
Unless you are getting some kind of discount from Maplin's, the Delta 15LF is only £53 including VAT at www.bkelec.com , which is only £3 more than the Maplin's link for the Beta 15.
That is why I mentioned the Delta 15LF when you made it clear you didn't want any recommendations. I figured it was okay to mention another driver if it is the same price, LOL.
Anyway, I'll let you make your own shopping decisions. Obviously I don't know all the facts of your situation.
If you don't mind my asking, where do you plan to put this? From the volumes you mentioned for the enclosure, I almost think you are putting this into a large unused closet. I did that once, by the way. ;) |
i want to/need to buy everthing from maplin as i do not have any way to pay online.
i was thinking the floor, with my other speakers. |
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| kelticwizard |
Yes, online ordering can be a problem. That explains a lot.
What kind of amplifier will be driving these? Since they are in the 95+ dB range, they will play much louder than a hifi sub, so you need less power. But I was just wondering what you planned to drive them with and with how much power.
Just because the Betas take 350 watts and the Deltas take 500, doesn't mean you necessarily have to give them that, of course. |
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| Matttcattt |
i am going to use my gainclone. this is about 200watts (i think :D).
are there any disadvantages of buying the delta? do you think i should buy one instead of the beta? |
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| kelticwizard |
I think if you are going to build a sealed box, one is as good as the other for your purposes. If you are going to go ported, the Delta has that big, big advantage of not having to worry about "suck-out" near resonance.
One tiny warning. The bass you get from the Delta in a 13 Ft³ might not be the cleanest bass in the world. Let me explain.
Back in 1971, Neville Thiele published a monumental paper that analyzed the ported box. Before that, most engineers used Sealed boxes because they did not know what kind of response they were going to get. If you see the term "Thiele-Small" parameters, that's the guy.
He took over a dozen examples of ported boxes with different Qts ratings for the drivers, etc, and called them "alignments". He gave a list of acceptable "alignments", and pointed out the ones which gave too much distortion. Drivers with a Qts over 0.38 give increasing amounts of distortion if the box volume is over Vas, which this is.
The "alignment" for this ported box is the last "alignment" Thiele put on his list. After this, the distortion gets too high. In other words, this setup will give some distortion in the bass, but that distortion will be acceptably low according to the fellow who is considered the pioneer in the ported box field.
Although I would not have chosen a speaker with this high a Qts to make a ported box, we must do with what we financially can afford at the moment. This speaker is available to you at a good price, and the "alignment" is on Thiele's list of acceptable "alignments".
You can get a smoother bass sound from a sealed box, but in my opinion, the cutoffs are too high. A 6½ inch speaker can go down to 50 Hz. If all you want is 50 Hz, why buy a 15 inch speaker?
When you bought this 15 incher, knowing it was a PA speaker such as a band would use and not a hi fi speaker, I assumed that you meant to say, "I want a good, tough bottom on my music that comes through real loud, and I am not worried about pleasing super high end standards. I want it built according to good principles, though."
I believe you will get that using the Delta 15LF in a 13 Ft³ box.
Of course, building a 13 Ft³ is quite an undertaking. I hope you have access to a good workshop, or are willing to have a lumber yard cut the pieces for you. |
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| SimontY |
Hi Matttcattt,
I have relatively limited experience with large drivers, or any really ;) but I have tried the Eminence Beta 15 myself.
Please do not buy it, you will be gravely dissapointed by its performance. Having said that, I did only try it in a 90 litre sealed box, and had no real idea of what I was doing - it was my 1st DIY hi-fi project :)
In this sized box the bass was sloppy - too high Q I believe, but more to the point the magnet seems far too small for a 15" driver. In other words it's never going to make tight, controlled bass, and certainly not deep - for one thing it won't have enough excursion.
Furthermore, making a much larger box than this isn't as much fun as it first sounds, unless you aren't actually a lazy ****** like me :) To reuse my 90 litre box and 'try again' I whacked in an Adire Audio Tempest, imported from the States. The bass was stunningly better! - much deeper, punchier, tighter, cleaner, and could play LOUD. And that is a far less sensitive driver...
You may not want more advice from me, but anyway... I would advise against getting anything like this sent over the pond - Adire is American, and my driver took a loooong time to reach me, and when it did it was faulty, so I then had to wait ages and ages for a replacement.
Finally, if you want to stick with Maplins, why not investigate those metal-coned car subwoofer drivers? They have large magnets, and are made to work in small enclosures, and are quite keenly priced. |
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| SimontY |
oops, accidentally sent that before I'd finsihed :rolleyes:
I was going to add, if you pop by Sheffield, I'll give you my old Eminence Beta 15, I think it still works, though it's slightly battered from the move back from my student house...
-Simon |
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| Matttcattt |
| quote: | Originally posted by kelticwizard
I think if you are going to build a sealed box, one is as good as the other for your purposes. If you are going to go ported, the Delta has that big, big advantage of not having to worry about "suck-out" near resonance.
One tiny warning. The bass you get from the Delta in a 13 Ft³ might not be the cleanest bass in the world. Let me explain.
Back in 1971, Neville Thiele published a monumental paper that analyzed the ported box. Before that, most engineers used Sealed boxes because they did not know what kind of response they were going to get. If you see the term "Thiele-Small" parameters, that's the guy.
He took over a dozen examples of ported boxes with different Qts ratings for the drivers, etc, and called them "alignments". He gave a list of acceptable "alignments", and pointed out the ones which gave too much distortion. Drivers with a Qts over 0.38 give increasing amounts of distortion if the box volume is over Vas, which this is.
The "alignment" for this ported box is the last "alignment" Thiele put on his list. After this, the distortion gets too high. In other words, this setup will give some distortion in the bass, but that distortion will be acceptably low according to the fellow who is considered the pioneer in the ported box field.
Although I would not have chosen a speaker with this high a Qts to make a ported box, we must do with what we financially can afford at the moment. This speaker is available to you at a good price, and the "alignment" is on Thiele's list of acceptable "alignments".
You can get a smoother bass sound from a sealed box, but in my opinion, the cutoffs are too high. A 6½ inch speaker can go down to 50 Hz. If all you want is 50 Hz, why buy a 15 inch speaker?
When you bought this 15 incher, knowing it was a PA speaker such as a band would use and not a hi fi speaker, I assumed that you meant to say, "I want a good, tough bottom on my music that comes through real loud, and I am not worried about pleasing super high end standards. I want it built according to good principles, though."
I believe you will get that using the Delta 15LF in a 13 Ft³ box.
Of course, building a 13 Ft³ is quite an undertaking. I hope you have access to a good workshop, or are willing to have a lumber yard cut the pieces for you. |
yes, i am not an audiophile :D im not that concerent about sound quality that much.
i am at school at the moment (its actually the holidays, but ill be back in september) and i have access to the workshops. i can buy the MDF through school too, at low prices.
depending on the price, i am going to try both ported and sealed, and i may try bigger and smaller boxes. for volume, i could make a smaller box, and put this inside the actual speaker cabnet to lower the volume, instead of making two boxes...
| quote: | Originally posted by SimontY
Hi Matttcattt,
I have relatively limited experience with large drivers, or any really ;) but I have tried the Eminence Beta 15 myself.
Please do not buy it, you will be gravely dissapointed by its performance. Having said that, I did only try it in a 90 litre sealed box, and had no real idea of what I was doing - it was my 1st DIY hi-fi project :)
In this sized box the bass was sloppy - too high Q I believe, but more to the point the magnet seems far too small for a 15" driver. In other words it's never going to make tight, controlled bass, and certainly not deep - for one thing it won't have enough excursion.
Furthermore, making a much larger box than this isn't as much fun as it first sounds, unless you aren't actually a lazy ****** like me :) To reuse my 90 litre box and 'try again' I whacked in an Adire Audio Tempest, imported from the States. The bass was stunningly better! - much deeper, punchier, tighter, cleaner, and could play LOUD. And that is a far less sensitive driver...
You may not want more advice from me, but anyway... I would advise against getting anything like this sent over the pond - Adire is American, and my driver took a loooong time to reach me, and when it did it was faulty, so I then had to wait ages and ages for a replacement.
Finally, if you want to stick with Maplins, why not investigate those metal-coned car subwoofer drivers? They have large magnets, and are made to work in small enclosures, and are quite keenly priced. |
i would rather use the Eminence delta than a car driver. thank you for the advice anyway. |
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| Matttcattt |
| quote: | Originally posted by SimontY
oops, accidentally sent that before I'd finsihed :rolleyes:
I was going to add, if you pop by Sheffield, I'll give you my old Eminence Beta 15, I think it still works, though it's slightly battered from the move back from my student house...
-Simon |
cool, i may be passing through sheffield on my way to flamingo land theme park in august. i doubt ill get a chance to stop though... :bawling:
if i cant collect it, and i sent you the money (about £7.50) would you post it to me?
thanks for the offer, either way. |
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| kelticwizard |
Matttcattt:
Before you go off and buy that Delta 15LF, hang on a day or two. There is just one more possibility I think you should be aware of. :) |
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| SimontY |
Matttcattt, I may not be around then anyway.
Sure I will post it, I was thinking of selling it at one point, but it's quite tattered, and I would get next to nothing for it. It's just lying in a box in the attic at the moment, I will take it down sometime in the next few days, and test it. I will make sure it works before organising any postage details.
I think it's great if someone can use such a thing, and actually wants it! Much better than it just sitting around doing nothing.
And to be fair to it, with music like rap, if you listen to **** like that ;) it can add some weight to 'thin' speakers.
-Simon
here is a pic of the beta15 in the baffle of my current sub (taken a year or so ago): |
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| Matttcattt |
| quote: | Originally posted by kelticwizard
Matttcattt:
Before you go off and buy that Delta 15LF, hang on a day or two. There is just one more possibility I think you should be aware of. :) |
which is...?
| quote: | Originally posted by SimontY
Matttcattt, I may not be around then anyway.
Sure I will post it, I was thinking of selling it at one point, but it's quite tattered, and I would get next to nothing for it. It's just lying in a box in the attic at the moment, I will take it down sometime in the next few days, and test it. I will make sure it works before organising any postage details.
I think it's great if someone can use such a thing, and actually wants it! Much better than it just sitting around doing nothing.
And to be fair to it, with music like rap, if you listen to **** like that ;) it can add some weight to 'thin' speakers.
-Simon
here is a pic of the beta15 in the baffle of my current sub (taken a year or so ago): |
cool. im surprised you are so eager to get rid of it. i will find a way to send you the money (probably by check). thanks :D |
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| Rarkov |
Here is an intersting idea for you...It's well known and documented...
First you need a driver that can handle about 100W RMS more than you plan to drive it (You have). Second, you need an amp with alot of headroom (don't run it at full pelt then!), Finally, you need a custom made filter.
This filter (normally just a couple of opamps) is basically the inverse frequency response of your sub. The idea is that when your driver starts naturally rolling off (say at 35Hz) then your filter provides extra gain, boosting the power. The effect is a sub that will easily reach and extra 10-15Hz lower and a smoother response.
Hope you like the idea...Quick easy and cheap!
Gaz |
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| amoeba86 |
| I don't get it, how is it cheap if you have to have a good amp and a high power handling sub. |
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| Rarkov |
He is already looking at a 350W sub driven at 200W...200W for such an efficitent driver is probably too much - so say you really run it at 100-150W. So all the ingredients are there, all that's left is an inverse frequency response filter. That's how! ;)
Gaz |
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| Pete Mazz |
He's basically describing a Linkwitz Transform circuit. Only other problem is you need a high excursion driver or else you'll bottom it out pretty easily with low freq info.
My advice would be to just hang on and save some more money to buy an appropriate driver. Look for close outs and slightly used to save money, but get a decent driver to start with.
Pete |
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| kelticwizard |
| quote: | Originally posted by kelticwizard
Matttcattt:
Before you go off and buy that Delta 15LF, hang on a day or two. There is just one more possibility I think you should be aware of. :) |
That possibility never materialized. BK Electronics was going to offer a clone of the Shiva, which is the 12" version of the Tempest that SimontY mentioned. If anything, the Shiva is is even better known and respected than the Tempest. BK Electronics was going to offer it for £65. I am not trying to push different drivers on you, but I thought you should know about it.
I Emailed BK Electronics, who said that they decided not to offer the Shiva clone for £65, since it would interfere with it's Eminence Lab 12, ( a driver with similar specs to the Shiva), for £127.
So forget that possible option. Get the Delta 15LF.
PS: I should mention that the Delta 15LF has a one way mechanical excursion of one inch. It will not be a clean sound as the mechanical excursion is neared, but you mentioned that you are not feeling fussy as long as the bass is there. |
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| Matttcattt |
| quote: | Originally posted by Rarkov
Here is an intersting idea for you...It's well known and documented...
First you need a driver that can handle about 100W RMS more than you plan to drive it (You have). Second, you need an amp with alot of headroom (don't run it at full pelt then!), Finally, you need a custom made filter.
This filter (normally just a couple of opamps) is basically the inverse frequency response of your sub. The idea is that when your driver starts naturally rolling off (say at 35Hz) then your filter provides extra gain, boosting the power. The effect is a sub that will easily reach and extra 10-15Hz lower and a smoother response.
Hope you like the idea...Quick easy and cheap!
Gaz |
do you have a link or a circuit? |
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| Matttcattt |
| quote: | Originally posted by kelticwizard
That possibility never materialized. BK Electronics was going to offer a clone of the Shiva, which is the 12" version of the Tempest that SimontY mentioned. If anything, the Shiva is is even better known and respected than the Tempest. BK Electronics was going to offer it for £65. I am not trying to push different drivers on you, but I thought you should know about it.
I Emailed BK Electronics, who said that they decided not to offer the Shiva clone for £65, since it would interfere with it's Eminence Lab 12, ( a driver with similar specs to the Shiva), for £127.
So forget that possible option. Get the Delta 15LF.
PS: I should mention that the Delta 15LF has a one way mechanical excursion of one inch. It will not be a clean sound as the mechanical excursion is neared, but you mentioned that you are not feeling fussy as long as the bass is there. |
ok, thanks for the advice etc. so far :D |
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| Rarkov |
Hi,
There is an example of designing such a sub in one of the chapters for a piece of software called BoxCAD. BoxCAD is the box modelling software in a design suite called SoundEasy.
The link to the chapter is here. Even though you probably don't have SoundEasy - you should be able to follow the example.
Hope this helps...
Gaz |
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| Matttcattt |
| i now have a question about bracing, if i make the box from 25mm thick MDF, and the box is approx. 80cm cubed, do need bracing? if so, how would i brace the box? does the diagram look alright? |
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| SimontY |
Yeh, looks excellent.
The more the better, with 25mm and that size box it won't be perfectly inert, but with cross bracing like that it should be pretty good.
-Simon |
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| Matttcattt |
| quote: | Originally posted by Rarkov
Hi,
There is an example of designing such a sub in one of the chapters for a piece of software called BoxCAD. BoxCAD is the box modelling software in a design suite called SoundEasy.
The link to the chapter is here. Even though you probably don't have SoundEasy - you should be able to follow the example.
Hope this helps...
Gaz |
where can i find SoundEasy? can i download it? i will read that PDF, but cannot see that circuit diagrams :(. |
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| Rarkov |
Hi,
I'm afraid it is dongle protected - so you have to bite the bullet and buy it. It's actually the cheapest and most comprehensive package out there - just a VERY steep learning curve.
You can find suppliers at their website: http://www.interdomain.net.au/~bodzio
There is a diagram in one of their screen shots (Figure 5.3). It includes all the necessary equations in the article. :bulb:
Out of interst - if you use the bracing - where would you put the sub?! :scratch:
Gaz |
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| Matttcattt |
| quote: | Originally posted by SimontY
Yeh, looks excellent.
The more the better, with 25mm and that size box it won't be perfectly inert, but with cross bracing like that it should be pretty good.
-Simon |
ok. have you had a chance to check the driver?
| quote: | Originally posted by Rarkov
Hi,
I'm afraid it is dongle protected - so you have to bite the bullet and buy it. It's actually the cheapest and most comprehensive package out there - just a VERY steep learning curve.
You can find suppliers at their website: http://www.interdomain.net.au/~bodzio
There is a diagram in one of their screen shots (Figure 5.3). It includes all the necessary equations in the article. :bulb:
Out of interst - if you use the bracing - where would you put the sub?! :scratch:
Gaz |
arg. ill just make do with the PDF.
i would have to cut the bracing on one of the sides, it was just a quick drawing. |
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| SimontY |
Sorry mate, not got round to checking it yet, will do very soon!
About that bracing, it's apparently a good idea to let the bass driver press firmly against the bracing, to support/couple it. Just make sure the voice coil/magnet vent has some space around it
Also, it might or might not be worth applying some blue tac or bitumen to the driver frame, if you have some lying around.
-Simon |
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| Matttcattt |
| quote: | Originally posted by SimontY
Sorry mate, not got round to checking it yet, will do very soon!
About that bracing, it's apparently a good idea to let the bass driver press firmly against the bracing, to support/couple it. Just make sure the voice coil/magnet vent has some space around it
Also, it might or might not be worth applying some blue tac or bitumen to the driver frame, if you have some lying around.
-Simon |
no rush :D
oh, ill put that into the design.
ill try that, isnt that called mass loading or summat. :confused: |
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| SimontY |
Right, just got it out of the attic and tested it. It works fine, so it's sitting in it's box waiting for a new home now. It is an Eminence Beta 15a - I wonder if there is a newer revision, as this is the better part of 3 yrs old now...
Btw 98db efficiency somehow seems a tad optimistic - when playing from my amp in it's box it makes about as much sound as my 91db speakers. However, our ears are most sensitive to frequencies ~1-5khz - which is probably a tad high for a 15" to make. So I've just made my argument void :rolleyes:
-Simon |
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| SimontY |
Mass loading is adding ballast/mass to stuff like speaker enclosures I believe. Maybe this isn't quite the same idea, maybe it is. Works though I reckon. With the bracing, get as much contact area between sides as possible. I've seen people making braces from piddly pieces of wood, because it's easy, but I doubt the effectiveness of this. What you had in your pic looks right, like a scaled down version of B&W's "Matrix" bracing, or the Andromeda on www.speakerbuilding.com
However, one thing I'd make sure of is getting a slightly different distance between each set of braces, just in case standing waves have a part to play, though the wavelengths should be way too long to propogate standing waves, right?
Another thing to try is using gasket tape or blue tac between the driver and cabinet, though you'd probably already thought of that one...
-Simon |
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| Matttcattt |
| quote: | Originally posted by SimontY
Right, just got it out of the attic and tested it. It works fine, so it's sitting in it's box waiting for a new home now. It is an Eminence Beta 15a - I wonder if there is a newer revision, as this is the better part of 3 yrs old now...
Btw 98db efficiency somehow seems a tad optimistic - when playing from my amp in it's box it makes about as much sound as my 91db speakers. However, our ears are most sensitive to frequencies ~1-5khz - which is probably a tad high for a 15" to make. So I've just made my argument void :rolleyes:
-Simon |
cool.
| quote: | Originally posted by SimontY
Mass loading is adding ballast/mass to stuff like speaker enclosures I believe. Maybe this isn't quite the same idea, maybe it is. Works though I reckon. With the bracing, get as much contact area between sides as possible. I've seen people making braces from piddly pieces of wood, because it's easy, but I doubt the effectiveness of this. What you had in your pic looks right, like a scaled down version of B&W's "Matrix" bracing, or the Andromeda on www.speakerbuilding.com
However, one thing I'd make sure of is getting a slightly different distance between each set of braces, just in case standing waves have a part to play, though the wavelengths should be way too long to propogate standing waves, right?
Another thing to try is using gasket tape or blue tac between the driver and cabinet, though you'd probably already thought of that one...
-Simon |
i have no idea about bracing, and my drawing was just the first idea that popped into my head. is bracing usually done with small pieces of wood between the sides of the box? looking at the Andromeda, should i use smaller holes, and have more of them? should i only leave ~50mm at the edges (of each brace (enlarging the hole to a rectangel))? |
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| Matttcattt |
| i have had a look at the delta, and it does not look as good as the Beta... i have attached the graphs. |
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| GM |
For sealed, you're right, but vented is a different story. Both work best in ~15.3ft^3, but the Delta is 3-4dB louder across the BW since it can linearly handle ~100W Vs the Beta's ~40W down low and has wider dynamic range up where it counts, in the midbass due to its higher power handling capability.
GM |
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| kelticwizard |
Matttcattt:
Your graphs for the vented box are for a cubic meter. Do you really plan to build a box that is 6 Ft tall by 3 Ft wide by 2 Ft deep?
The 13 Ft³ enclosure we were talking about itself is considered enormous. |
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| Matttcattt |
| quote: | Originally posted by GM
For sealed, you're right, but vented is a different story. Both work best in ~15.3ft^3, but the Delta is 3-4dB louder across the BW since it can linearly handle ~100W Vs the Beta's ~40W down low and has wider dynamic range up where it counts, in the midbass due to its higher power handling capability.
GM |
| quote: | Originally posted by kelticwizard
Matttcattt:
Your graphs for the vented box are for a cubic meter. Do you really plan to build a box that is 6 Ft tall by 3 Ft wide by 2 Ft deep?
The 13 Ft³ enclosure we were talking about itself is considered enormous. |
maybe not that big. :D
i have re-done the graph using 13Ft cubed boxes.
the Beta in a vented enclosure still beats the Delta... |
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| kelticwizard |
Matttcattt:
The Delta and Beta have identical F3's. For that matter, they both have identical F2's, F4's, and F5's as well.
The "advantage" of the Beta lies in a region that is below the passband. Generally, you can count on little good output in a vented box below the tuning frequency, which in our case will be 30 Hz.
The visual advantage of the Beta from 22 Hz on down just does not translate into any advantage in real-world performance.
Besides, these simulation programs are great, but they are only general guides. The fact is that there are going to be a variation in the specs from the printed specs, and even variation from driver to driver from the same batch. The simulations you see are merely meant to be a ballpark idea of what you can expect. Taking the comparison this far is a mistake. |
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| SimontY |
Matttcattt,
All this talk of Delta vs. Beta is null and void, because you are getting a free Beta.
When you get bored of it and want some serious lows, then you can start looking at high excursion drivers, big amps, and smaller boxes.
Also, surely when you were comparing the two drivers in a sealed box, you noticed the Delta had a very low Q, compared to the Beta's medium Q. This 'Q' defines the tightness/damping of the bass. This means in a 500l box the Beta would have 'correct' sounding bass, [with 0.71 iirc]. The Delta would sound undernourished in that big a box I believe, and there is it's big advantage: it could work well in a much smaller box (270l) ie. 1/2 the size.
Personally with this Beta, I would try a sealed 250l box with loads of stuffing to get the volume up a tad. If you can get 3-6db of boost at about 30-35hz, as on many plate amps, this might turn out ok. Vented would be massive, and probably make very muddy and distorted bass. (Your mother would surely go ape over a 700 litre cabinet!)
Feel free to e-mail me about the cost etc. of sending this thing, I don't know its weight or how you want it sending...
-Simon |
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| Matttcattt |
| quote: | Originally posted by kelticwizard
Matttcattt:
The Delta and Beta have identical F3's. For that matter, they both have identical F2's, F4's, and F5's as well.
The "advantage" of the Beta lies in a region that is below the passband. Generally, you can count on little good output in a vented box below the tuning frequency, which in our case will be 30 Hz.
The visual advantage of the Beta from 22 Hz on down just does not translate into any advantage in real-world performance.
Besides, these simulation programs are great, but they are only general guides. The fact is that there are going to be a variation in the specs from the printed specs, and even variation from driver to driver from the same batch. The simulations you see are merely meant to be a ballpark idea of what you can expect. Taking the comparison this far is a mistake. |
so the beta is no better in real life?
| quote: | Originally posted by SimontY
Matttcattt,
All this talk of Delta vs. Beta is null and void, because you are getting a free Beta.
When you get bored of it and want some serious lows, then you can start looking at high excursion drivers, big amps, and smaller boxes.
Also, surely when you were comparing the two drivers in a sealed box, you noticed the Delta had a very low Q, compared to the Beta's medium Q. This 'Q' defines the tightness/damping of the bass. This means in a 500l box the Beta would have 'correct' sounding bass, [with 0.71 iirc]. The Delta would sound undernourished in that big a box I believe, and there is it's big advantage: it could work well in a much smaller box (270l) ie. 1/2 the size.
Personally with this Beta, I would try a sealed 250l box with loads of stuffing to get the volume up a tad. If you can get 3-6db of boost at about 30-35hz, as on many plate amps, this might turn out ok. Vented would be massive, and probably make very muddy and distorted bass. (Your mother would surely go ape over a 700 litre cabinet!)
Feel free to e-mail me about the cost etc. of sending this thing, I don't know its weight or how you want it sending...
-Simon |
ok |
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| kelticwizard |
Matttcattt:
Both the Beta and the Delta will produce similar results when their specs are graphed. If their specs hold up in the world, they will produce similar results when placed in a 13 Ft³ box.
The advantage of the Delta is that extended core which prevents the lopping off of the wave form near resonance. That is very necessary for good sound reproduction. The sealed boxes cut off way too high to qualify as "subwoofers".
Also, the Delta has a 50% bigger magnet than the Beta-56oz versus 38 oz-and a longer excursion as well.
Let me mention again that the Delta has a maximum excursion of 1 inch each way. Granted it is non linear, but when given sufficient push it will move that air. That is a lot of air, especially when you port the speaker.
As far as the talk of the Delta being "null and void", that is up to you. You might decide to try the free Beta and see how it sounds and if it is unsatisfactory, try the Delta. Or you might try something else. Or you might use the Beta for another project. As I see it, the goal of this project was to build a subwoofer using a high SPL speaker. Most subs are inefficient, but you wanted high SPL and were not fussy about audiophile measurements. Most PA systems do not go down to 30 Hz, as the size of this cabinet makes clear. This rather large cabinet should go down that low.
So I don't think the Delta is necessariy out of the running. I think it is basically up to you. |
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| Matttcattt |
| quote: | Originally posted by kelticwizard
Matttcattt:
Both the Beta and the Delta will produce similar results when their specs are graphed. If their specs hold up in the world, they will produce similar results when placed in a 13 Ft³ box.
The advantage of the Delta is that extended core which prevents the lopping off of the wave form near resonance. That is very necessary for good sound reproduction. The sealed boxes cut off way too high to qualify as "subwoofers".
Also, the Delta has a 50% bigger magnet than the Beta-56oz versus 38 oz-and a longer excursion as well.
Let me mention again that the Delta has a maximum excursion of 1 inch each way. Granted it is non linear, but when given sufficient push it will move that air. That is a lot of air, especially when you port the speaker.
As far as the talk of the Delta being "null and void", that is up to you. You might decide to try the free Beta and see how it sounds and if it is unsatisfactory, try the Delta. Or you might try something else. Or you might use the Beta for another project. As I see it, the goal of this project was to build a subwoofer using a high SPL speaker. Most subs are inefficient, but you wanted high SPL and were not fussy about audiophile measurements. Most PA systems do not go down to 30 Hz, as the size of this cabinet makes clear. This rather large cabinet should go down that low.
So I don't think the Delta is necessariy out of the running. I think it is basically up to you. |
ok, thanks for all the advice. any advice for bracing? |
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| kelticwizard |
Bracing? You might want to make that a separate thread. I have never built a box as large as 13 Ft³.
One thing I do know. If you are not going to build a cubic box-if you are going to have a long side-the bracing should be along the longest side. In other words, if a panel is 6 Ft by 2 Ft, don't bisect the panel and make it two 3 Ft by 2 Ft sections. Rather, take a long brace and make it two 6 Ft by 1 Ft sections.
It has been shown that is the best bracing. |
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| GM |
>One thing I do know. If you are not going to build a cubic bos-if you are going to have a long side-the bracing whould be along the longest side. In other words, if a panel is 6 Ft by 2 Ft, don't bisect the panel and make it two 3 Ft by 2 Ft sections. Rather, take a long brace and make it two 6 Ft by 1 Ft sections.
>It has been shown that is the best bracing.
====
Hmm, can't say as I agree with this. The majority of speaker cabs I've built have been fairly large, up to 40ft^3, with my current speakers being 20ft^3. If you study structural engineering or just look at a beam truss or bridge's construction, you'll see that triangulation is best since it offers the greatest stiffness by dividing a panel into a highly damped shape. As you note, dividing panels up into a series of unequal areas (golden ratio triangulation works well), then further triangulating the large 'panels' works extremely well. Note that none of the stiffeners should touch another or terminate at a corner/joint (leave a gap) since this creates a high pressure point where resonances can sum. I use whatever no-void plywood scraps I have laying around for stiffeners, they just need to be a few inches wide and glued on edge. Increasing stiffness by using at least 3/4" thick 13 ply no-void Baltic Birch or equal is an expensive, but major plus since it raises any resonances up to where the cab's mass can effectively damp them. FWIW, mine are made with 3/4" marine grade plywood from back when it was guaranteed no-void and dual 15" driven to Xsus doesn't vibrate over a nickel stood on edge.
Cabs designed for LF reproduction need to have all their sides tied to each other so that it can't 'breathe'. I prefer 2x4s or large closet pole hardwood dowels since they're easy to work with and cheap. Smaller cabs, I use 2x2s or smaller dowels. Just depends on what's laying around or on sale. ;) The previously shown 'X' panel bracing works well, but a large cab needs two or more and they impede air flow in the cab to a greater or lesser extent depending on design, and are more work to make.
Another concern when a cab's dimensions become large enough that standing waves can develop within its intended BW is its aspect ratio and where the driver(s) are located. A golden ratio cab is the smoothest overall since all its modes are averaged out, allowing the driver(s)/vent (if used) to be positioned most anywhere. This can make for a very obstrusive design though, so making it tall to keep the 'footprint' within reason requires that attention be paid to the driver(s)/vent location if used much beyond 100hz. I learned how to figure it out through experimentation, but now, MJK's MLTQWT or ported spreadsheet makes finding the optimum a quick/simple task.
Anyway, following these simple rules will net you a stiff/well damped (and heavy) cab that won't audibly 'color' the music.
GM |
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| kelticwizard |
GM:
Yes, you make great points.
As for the long brace for the 6' X 2' panels, let me explain.
I meant what is the best way to brace a 6' X 2' panel if all you have is horizontal or vertical bracing.
Strength comes from having any given area as close to a brace as possible.
I think we can count the corners as braces. So that 6' X 2' panel actually will have 3 braces-the one down the middle, plus the lengthwise ones at the ends where it joins the other pieces.
If you take that 6' X 2" panel, and bisect it so that becomes two 3' X 2" sections, then the middle of each panel has a whole area that is 1 foot away from a brace. The farther away from a brace, the weaker and the more likely to flex.
If you take that 6' X 2' panel and run a brace the entire 6' length, you have stiffened the panel more. With two 6' X 1' sections, there is no spot on that panel where a brace is farther away than 6 inches. This is a great improvement over the cross brace that divides the panel up into 3' X 2' sections.
Of course, X bracing and the other things you mentioned are great. I was talking about one brace.
I should add that the latest thinking is not to divide panels in half. So the lengthwise 6' brace should divide the panels up into something like 13" and 11", instead of 12" and 12". |
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| GM |
Right, I understand and agree. All I'm saying is that the one long brace should be diagonal, and that it be offset so the two 'panels' can't complement each other. Further triangulating these two large areas into smaller ones of various sizes will dramatically stiffen it up. A diagonal brace also damps the potential TL modes that could occur in your two long parallel 'lines'.
It's not that what you propose is ineffective, quite the contrary, just that triangulation is superior to what you proposed as 'best'. ;)
GM |
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| slowmotion |
| quote: | Originally posted by GM
Note that none of the stiffeners should touch another or terminate at a corner/joint (leave a gap) since this creates a high pressure point where resonances can sum.
GM |
Hi GM, all
When using shelf braces should I make cutouts
so the shelf braces don't touch the corners of the speaker cabs?
Or each other?
Thanks ;) |
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| Matttcattt |
| so is the bracing on the picture i posted ok? do i need more/less/different? |
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| GM |
Slowmotion:
Shelf braces are a way to ~ 'kill two birds with one stone' by tying all sides together while breaking up large panels into smaller ones, so they must all touch/interlock. For sub duty only in cabs that aren't acoustically large for the BW, they're very effective and their negative side effects occur at frequencies above its cutoff.
Matttcattt:
Your cab needs to be too large IMO to keep from getting out of BW noise back through the cone, but if you want to use them, then make enough of them to subdivide the cab into many smaller cabs, ideally as close as you can to the golden ratio of 0.618:1.0:1.618. IOW each smaller 'cab' would have this dimensional ratio as would each 'cab' to each other 'cab'.
When figuring the round cutouts to allow airflow, you want to use a variety of different sizes, preferably eggshaped or at least freeform, and as large as practical without destroying the structural integrity of the piece. Some folks cut out four big rectangles, leaving just an "X" brace. Might as well just stick in 2x4s/wood dowels/whatever and save yourself all that sawing IMO.
GM |
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| slowmotion |
Ah, thanks GM,
I was wondering there for a while :scratch:
All is well ,then
cheers ;) |
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| Matttcattt |
more questions, and i dont want to start a new thread.
1. ports, i am using winisd to make graphs, and this program only allows a small range of port sizes and lengths. if it says i need 3 ports of x length, and z width and hieght (square port), can i have one port x long, z wide, and 3 times z high?
2. carpet, i have read somewhere that i should put carpet on the inside of the box. why should i do this? which side/s do i put it on? the side with the driver and port/s, or the oposite side?
thankyou for any answers.
PS: sorry about the delay SimonTY, i have been on holiday, i will E-Mail you my address, and send you the money ASAP. |
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| kelticwizard |
Matttcattt:
WinISD, the freeware version, can calculate that for you.
Just click on the circle under "shape" if you want a rectangular port, and fill in the number "1" for the number of ports.
Actually, in a 13 Ft³ box, you can get by without a port jutting into the box. The ¾" thickness of the MDF itself will suffice. The larger the box, the smaller the port length for any given port crossection. In large boxes such as yours, simply cutting a hole in the wall of the box will give you a usable vent.
According to WinISD, a vent 3" X 6" will tune your box to 30 Hz.
If you want to make the cross section larger, (which will result in less port noise), then you can increase the port size if you want. For instance, a port that is 6" X 10" would require a length of 7¾".
You can also switch the dimensions in WinISD to Metric if you feel more comfortable that way. |
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| mikee12345 |
winisd can be abit dodgy
one version doesnt calc ports right when u have 2
:dodgy: |
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| Matttcattt |
| quote: | Originally posted by kelticwizard
Matttcattt:
WinISD, the freeware version, can calculate that for you.
Just click on the circle under "shape" if you want a rectangular port, and fill in the number "1" for the number of ports.
Actually, in a 13 Ft³ box, you can get by without a port jutting into the box. The ¾" thickness of the MDF itself will suffice. The larger the box, the smaller the port length for any given port crossection. In large boxes such as yours, simply cutting a hole in the wall of the box will give you a usable vent.
According to WinISD, a vent 3" X 6" will tune your box to 30 Hz.
If you want to make the cross section larger, (which will result in less port noise), then you can increase the port size if you want. For instance, a port that is 6" X 10" would require a length of 7¾".
You can also switch the dimensions in WinISD to Metric if you feel more comfortable that way. |
the help documents with winisd say that ports must be 3" long as a minimum, is this true? i have seen many sub woofers with 'wall-thick' ports. if i can use the wall thickness, it will make working out the size, and making the port/s easier.
| quote: | Originally posted by mikee12345
winisd can be abit dodgy
one version doesnt calc ports right when u have 2
:dodgy: |
do you know which? :confused: i have the original, as the website advises that the pro version is still in testing. |
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| mikee12345 |
i think the old version is safe.
i use a patched version of new one
u shud get a few programs to compare with
:)
re: ports
i wouldnt worry about using wall thickness.
a box that is tuned properly is simple one that has driver volume,bracing ,shelf port etc minused from total volume
my jbl tuned to 33hz like it shudve.
also shelf ports lengths are minus 0.5 *height ,i think.
in theor winisd SHUd allow ports down to 0.0000001 inches :P:P
:) |
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| Matttcattt |
another question...
which side of the sub would be best to put the port on? the same as the driver, the oposite side to the driver?
also, i havent had an answer to my question about putting carpet on the inside of the box. |
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| SY |
| quote: | | which side of the sub would be best to put the port on? the same as the driver, the oposite side to the driver? |
Makes no difference, as long as the port is unobstructed. |
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| Matttcattt |
| quote: | Originally posted by SY
Makes no difference, as long as the port is unobstructed. |
ok |
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| Matttcattt |
| ive been doing some research into stuffing. in theory, can i use any fiberous material? how can i work out the change in Q by adding stuffing? do low density, or high density materials change the Q more? also, what is the best way to hold the stuffing in place, and off the driver? |
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| mikee12345 |
if ur stuffing a sealed box,it just acts like a 10% larger box when fully stuffed>or something>
there was a good link on the net about some one who fully tested stuffings.
i would imagine using some sort of speaker stuffing is best.
apparently pinkbatts works.
any sort of fibrous material will workbut to what degree-who knows.
ported box-just line the walls dont 'fill' it
cos then ur volume will be different-
so your port wont tune right
and also it mite get abit resistive,the port that is
those are my opinions-some one will correct me if im wrong.
ooh its late ,so excuse my ramblings,it mostly makes sense :)
:) |
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| Matttcattt |
| why will knowbaody post on my threads? do i scare them? :devilr: |
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| Matttcattt |
| quote: | Originally posted by Matttcattt
why will knowbaody post on my threads? do i scare them? :devilr: |
<tumbleweed rolls past>
Hello?
<echo>
Hello?
</echo>
:bawling: |
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| SimontY |
Hi Matttcattt,
People get bored, and want to see things happening, progress. You have been hovering around some basic questions and points for a while, and I think everything important has already been answered!
All that remains is to get building the sub, and expect to experiment with it - that way you can learn by the best method!
Box- brace well, don't make it a cube, make it pretty, make it forwards-firing, don't worry anymore than that
Ports- make it/them a little oversized and cut down length to adjust tuning if necessary
Stuffing and overall box volume- work out box volume and assume your (not overdone) stuffing adds enough volume to compensate for the port volume - just stick foam to the walls and be happy :) Do work out how much vol. is lost from the bracing. Use a glue gun or spray glue on the stuffing, I tried nails once, but I wouldn't really advise that!!
I still have this Eminence bass driver taking up space somewhere, please e-mail me if you want it. I will need your address, then a little money for postage, won't be much - it's quite light.
-Simon |
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| paulspencer |
if you work out a budget and you plan to make such big boxes, don't forget to allow the cost of a chiropractor!!!!
also if you want to make big test boxes, consider instead of making two separate big boxes, make two modules so that you can bolt them together to get the bigger size. |
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| Matttcattt |
| quote: | Originally posted by SimontY
Hi Matttcattt,
People get bored, and want to see things happening, progress. You have been hovering around some basic questions and points for a while, and I think everything important has already been answered!
All that remains is to get building the sub, and expect to experiment with it - that way you can learn by the best method!
Box- brace well, don't make it a cube, make it pretty, make it forwards-firing, don't worry anymore than that
Ports- make it/them a little oversized and cut down length to adjust tuning if necessary
Stuffing and overall box volume- work out box volume and assume your (not overdone) stuffing adds enough volume to compensate for the port volume - just stick foam to the walls and be happy :) Do work out how much vol. is lost from the bracing. Use a glue gun or spray glue on the stuffing, I tried nails once, but I wouldn't really advise that!!
I still have this Eminence bass driver taking up space somewhere, please e-mail me if you want it. I will need your address, then a little money for postage, won't be much - it's quite light.
-Simon |
i have started cutting the MDF, and when i get a chance i will post some pictures.
i will E-mail you my address if you post your E-mail here. send me your address and i will post the cash (£10?). |
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| Matttcattt |
i have some questions about these "golden ratios" and "standing waves".
1. what are the "golden ratios"?
2. will standing waves matter in a sub? using this program, the standing waves are at 200Hz, which my sub will not reach (LP at 120Hz). |
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| SimontY |
Hi MatttCattt,
I can't remember what golden ratios I've seen before, look here for some good ratios:
http://www.audioasylum.com/forums/r...ssages/375.html
These are more useful for rooms than subwoofer cabinets :)
I agree it can't be so important for such low frequencies, but you will get [quiet] sounds at ~200hz coming from your sub, unless you somehow roll it off ultra steeply.
Better to use good ratios than a cube :)
I got your e-mail btw, cheers.
-Simon |
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| Matttcattt |
| quote: | Originally posted by SimontY
Hi MatttCattt,
I can't remember what golden ratios I've seen before, look here for some good ratios:
http://www.audioasylum.com/forums/r...ssages/375.html
These are more useful for rooms than subwoofer cabinets :)
I agree it can't be so important for such low frequencies, but you will get [quiet] sounds at ~200hz coming from your sub, unless you somehow roll it off ultra steeply.
Better to use good ratios than a cube :)
I got your e-mail btw, cheers.
-Simon |
So about 1x1.5x2?
I will have a LP filter. i havent desided what type yet. :P
yep, money is in the post now. should arive friday/saturday (is there post on saturday?). |
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| SimontY |
Hi,
No, not quite, lol. The idea is that the numbers are not multiples of one another!
The reason it's important for room acoustics is to avoid 'room modes' building up on top of each other. You must consider harmonics of the fundamental frequency. It's most easily explained with an example:
Room = h5xw15xl20m (your number ratio)
Speed of sound in air = 330m/s
Frequencies whose half-wavelength is equal to a room(or speaker cabinet side wall) dimension will be 'amplified'. Then multiples of this will be equally. So, back to our example..:
Room height = 5m > 330/10 (5x2) = 33hz(fundamental), 66hz (F2/2nd harmonic), 99hz, 132hz etc. etc.
Fine so far, but then these are added to our width modes:
15m > 330/30 = 11hz (yum yum), 22hz, 33hz, 44hz, 55hz, 66hz, 77hz, 88hz, 99hz, 110hz, 121hz, 132hz, etc. etc.
Already, without doing the same for length it's easy to see the problem: 33hz, 66hz, 99hz, 132hz etc. will directly pile up and combine to make the bass very, very lumpy.
Apparently it's possible to have variations of up to 30db from this effect in a room!!!
Golden ratios aim to have little overlap of these numbers - they should be spaced apart from each other.
I hope this makes sense to you, I know my explanations aren't all that good!
-Simon |
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| Matttcattt |
| quote: | Originally posted by SimontY
Hi,
No, not quite, lol. The idea is that the numbers are not multiples of one another!
The reason it's important for room acoustics is to avoid 'room modes' building up on top of each other. You must consider harmonics of the fundamental frequency. It's most easily explained with an example:
Room = h5xw15xl20m (your number ratio)
Speed of sound in air = 330m/s
Frequencies whose half-wavelength is equal to a room(or speaker cabinet side wall) dimension will be 'amplified'. Then multiples of this will be equally. So, back to our example..:
Room height = 5m > 330/10 (5x2) = 33hz(fundamental), 66hz (F2/2nd harmonic), 99hz, 132hz etc. etc.
Fine so far, but then these are added to our width modes:
15m > 330/30 = 11hz (yum yum), 22hz, 33hz, 44hz, 55hz, 66hz, 77hz, 88hz, 99hz, 110hz, 121hz, 132hz, etc. etc.
Already, without doing the same for length it's easy to see the problem: 33hz, 66hz, 99hz, 132hz etc. will directly pile up and combine to make the bass very, very lumpy.
Apparently it's possible to have variations of up to 30db from this effect in a room!!!
Golden ratios aim to have little overlap of these numbers - they should be spaced apart from each other.
I hope this makes sense to you, I know my explanations aren't all that good!
-Simon |
ah, now i understand. the problem with learning from forums is, people never explain things when the person they are talking to knows what they are talking about. so my understanding of audio etc. is a bit patchy. |
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| SimontY |
| quote: | | people never explain things when the person they are talking to knows what they are talking about. |
I have the same problem VERY often, which is why I don't mind explaining stuff if I can possibly help.
-Simon |
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| Matttcattt |
Having now finished my subwoofer and listened to it for a while, I am thinking of improving it.
As documented in different thread, I am building a Linkwitz Transform circuit, to equalise the output. This will be the only change for a while, as this is costing about £10, and I can’t afford more than this, ruling out more expensive upgrades.
The next development will be a new, better driver. I had previously assumed that I would get an Adire Tempest, as they seem to be a very popular driver. I then tried some of the other drivers by Adire in WinISD, and some look good. The main two were the tumult and DPL 12. In comparison to the tempest, the DPL 12 is amazing (see attached graph). Looking at the prices, the DPL 12 is the same as a tempest, and over three times cheaper than the tumult. I have read the DPL 12 is good for dipoles, and it says this one the page, but I don’t know if this meant it is useless for standard boxes.
My question is, is the DPL 12 ok for use in standard boxes? Most importantly, my 93L sealed box, which it would go into. If I can’t use the driver, which driver should I consider buying? I can’t afford $500 for a driver like the tumult, but possibly $300. |
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| Matttcattt |
Hmm, can’t edit my post...
Anyway, I also wish to mention that I want to try to build a horn (probably similar – size wise – to the LABSUB) using this new driver, so I would like to get one that was quite suitable for this use. |
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| GM |
>My question is, is the DPL 12 ok for use in standard boxes? Most importantly, my 93L sealed box, which it would go into.
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Of course!
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>Anyway, I also wish to mention that I want to try to build a horn (probably similar – size wise – to the LABSUB) using this new driver, so I would like to get one that was quite suitable for this use.
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Then I recommend you buy the Labhorn driver since the DPL12 isn't all that suitable for compression horn loading IMO, the compression ratio would be too high, potentially causing non-linear performance due to overheating and its surround deforming. Looks ideal for a large backhorn or TL though.
GM |
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| REDSKIN |
| quote: | Originally posted by Matttcattt
My question is, is the DPL 12 ok for use in standard boxes? Most importantly, my 93L sealed box, which it would go into. If I can’t use the driver, which driver should I consider buying? I can’t afford $500 for a driver like the tumult, but possibly $300. |
| quote: | Originally posted by Matttcattt
Hmm, can’t edit my post...
Anyway, I also wish to mention that I want to try to build a horn (probably similar – size wise – to the LABSUB) using this new driver, so I would like to get one that was quite suitable for this use. |
Considering the above points would it not be wise to just buy 2 eminence lab12's? With these 2 in your 93l sealed box you get an f3 about 40hz. If you can't afford 2 get 1 and port your 93l for an f3 about 25hz. Then if you do go on to build a LABSUB you'll have the 2 lab12's required. LAB12's cost about £120 from bk electrics.
hope this helps |
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| Matttcattt |
I dont actually want to build the LABSUB, just a similar sized horn.
If the DPL 12 is no good for horn loading, which of the Adire drivers are? The Tempest?
Thanks for the help so far. |
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| GM |
Well, the Shiva has specs very close to the Labhorn driver and I believe the Labhorn prototype used them, but if you plan to build a cab of ~the Labhorn's size, odds are pretty good you can't improve on its performance, so it seems reasonable to me that eventually building it is a no-brainer.
Even if you don't, the Labhorn driver is still the obvious choice.
GM |
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| mikee12345 |
see my site.
I wouldve liked to have used a dpl12 or similar cos its cheaper and models as well..but again i dont trust any woofer with 2.5:1 compression ratio.
im gona have to buy a single lab12 for my little horn |
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| Matttcattt |
| quote: | Originally posted by mikee12345
see my site.
I wouldve liked to have used a dpl12 or similar cos its cheaper and models as well..but again i dont trust any woofer with 2.5:1 compression ratio.
im gona have to buy a single lab12 for my little horn |
i have seen your site. you look like a horn expert. :d or one in the making. :P
would the lab12 work well in a lower frequency horn than the LABSUB (25Hz instead of 35Hz)?
i am trying to learn to use hornresp, so i will post any questions i have in this thread, and hopefully you (mikee12345) will see them. :) |
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