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Discussion Starter #1 (Edited)
I was browsing the web with some questions about comb filtering and found Roger Russell's website. This page in particular: Why be so overly concerned about comb filtering in column speakers when you probably get this all the time with the speakers y

Because I'm still in the market for new speakers I was atracted by his story on line array's especially the IDS-25 line array. In my living room such an array would work out great as it can be placed quite close to the walls and use very little space compared to my 15" wover current speakers.
My girlfriend keeps nagging me to replace them with smaller ones. After I showed her the IDS-25 she gave me the "OK" to try and build some.


I've found the original article from Roger Russell about these speakers and their 4" x 20 predecessors and am intregued. See attached pdf.
If anyone wants it I'll upload the pdf of the 4" version too.

Would it be possible to build a line array (same size) as the IDS-25 using the Vifa TC9FD18-08 drivers? I'd use a behringer DEQ24/96 for the time beeing to do the EQ part.

The part I'm worried about is the high Qts of these compared to the original driver Roger used in his array. Would that create problems? When searching for Vifa TC9FD18-08 it seems there used to be a lower (0.7) Qts version. Frequency responce seems very much alike. However this is a paper cone compared to glass fibre in the real thing. (Viva TG9FSD10-08 http://www.tymphany.com/files/resources/dvifa/TG9FSD10-08.pdf)
I'd like some schooled opinions on this if possible.
 

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The fact the "article" starts off with a red herring should give you a clue as to where it is heading.

He offers no proof that it doesn't happen.
 

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Discussion Starter #3 (Edited)
The fact the "article" starts off with a red herring should give you a clue as to where it is heading.

He offers no proof that it doesn't happen.
He doesn't, he states it does happen but doesn't have that much of an impact. He compares it to seeing movies as a fluent motion if in fact it is a series of still images.

But I was looking for some input on an affordable driver for such a line array speaker.

Here's another design: The Murphy Corner-Line-Array Home Page

This one uses the Dayton Audio ND90-8.

Another candidate for an array might be the Tangband W3-1053SC 3":
http://www.parts-express.com/pdf/264-880s.pdf

But I was wondering if the Vifa TC9FD18-08 would be a better choise because of the Copper pole piece cap to limit distortion same as in the driver Roger Russell used.
See specs here: http://www.tymphany.com/files/TC9FD-18-08%20Rev1_0.pdf
 

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How we see movies isn't the same as we hear music.

Rather than taking his word for it, I would like to see a couple of measurements to support the claims.

And you would need to sit a long way away from the speakers to get anywhere near flatish response from them.
 

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Discussion Starter #5 (Edited)
Did you download the attached pdf? It has measurements after EQ on page 9. If you look at the The Murphy Corner-Line-Array Home Page link above you'll many more graphs from a similar system both before and after equalisation.
I've read a lot on this subject over the past week, both positive and negative. One fun thread was about the IDS-25, where almost everyone was pissing on this design until someone came forward who had actually heard these in a motel room. So how far did they have to be from these speakers to get good sound?
I will not deny comb filtering will be an issue, however reading up on the personal experiences from people who have heard these seems to indicate they do sound great.

I have no way of knowing what I'll get myself into. But these designs seem to fit the bill for me, that is, if I can find a suitable driver for a decent price.

On most forums I have found that discus this particular design, there is a huge amount of prejudice without ever hearing them.

Some things are hard to imagine though, Russel claims the total cone area is bigger than one 16" woofer. Sure it is, but where's the excursion? So in the end the system will be somewhat limited in bass output I guess. But there's no way for me to be sure about that (yet). Reading up on the other example I profided: The Murphy Corner-Line-Array Test Results

MCLA array said:
As a low frequency stress test I tried to drive the array to 10% distortion at 50 Hz. This is one measure of the maximum operating level of a speaker in the low bass range. Figure 5-13 shows the array operating at the highest level I could generate before the everything in the room started vibrating loudly. The system reached 113 dB SPL at 50 Hz with 65 Watts of drive level (18.7 Vrms into 5.33 Ohms). The dominant distortion is 2nd harmonic at -26 dB or 5% distortion. The 3rd harmonic is at -29 dB or 3.5%. The 5th harmonic was only at -48 dB or 0.4%. This is excellent high SPL low bass performance! A single array can drive the ROOM to the limit of what it can take with just 65 Watts at 50 Hz. At the highest levels a person (or room) can stand (113 dB SPL in this case) the distortion does not exceed 5% at 50 Hz.
So that's not bad at all. The low distortion I believe, think about how little these full rangers have to do because there are 50 of them in total...

I do hope I'll get some usefull help, I'd like to dive in and experience this for myself. It's a big risk on my part, but I was bored listening to most commercial speakers in the $ 1500 -2000 setprices in the shops I have been to and the ones that seemed promissing where no easyer to place in a room than my current set with 15" woofers. They all need to be placed away from the wall etc... and none of them have a footprint as small as these.

Reading the track record of Mr. R Russell: http://www.roger-russell.com/columns/columns.htm convinced me he knows way more about speakers than I ever will in my life. I know most in this business will say what they made is the greatest thing on the planet but what did he have to gain when he published the plans for the IDS-25 in an audio magazine for everyone to copy. That is the same set one can buy for more than $ 18.000,00 today.

Similar to the Linkwitz Orion, you can buy the plans or buy ready made versions. But Roger Russell published the plans without making money (I asume). With todays internet those plans are readilly available and attached to this thread :).

I am intregued to be able to build $ 18.000,00 speakers for a lot less. If I can figure everything out, that is.
 

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Discussion Starter #6

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Discussion Starter #7
To answer my own question, the versions in Europe, or at least Germany seem to be different. They even have different names for what seems to be the same driver.

I modelled both the original IDS driver and the cheaper Peerless/Vifa and although there are important differences in specs the output of the cheap driver comes very close, about 5 Hz behind in the bass region. One thing holding me back is Xmax.
I had seen this as 3mm on several sites but it is 1.5 mm linear xmax and max xmech (?) is 3mm. That's where the more expensive driver shines in comparison with 2.35mm. So max output of the cheaper ones is going to be more limited I guess. But due to the line array gain it still might be more than worth it to try.

But to dare it I'd like to know how much Mr. Russel had to boost the lows. If he bumped it by 9 dB, the bump would take 16 watt, but that's only 16/25 = 0.64 watt for each driver in the column! It would require some serious amps if it is boosted any higer to crank it up though. Mr. russell claims 250 watt/channel to have headroom. If it's only a 6 dB boost in his setup I'd be willing to try the cheaper drivers. There are some graphs but it's impossible to read something on that.

It's comming down to just under 12 euro/driver or cough up 29 euro/driver for the unshielded version of the IDS with the 2.35mm xmax. Mr. Russell only used shielded drivers. I haven't seen those for sale anywhere.

I'm willing to take a risk on a line array and it's troubles with combing due to driver spacing. I'm not sure though I'd want to do that with 50x 29 euro worth of drivers...
 

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1450 Euro is a pretty big chunk of change for an experiment.

Does Monacor or Visaton not have anything less expensive that would give you a good idea on the flavoring?
 

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Discussion Starter #9
Well, after searching for a suitible cheap replacement driver I stumbled over this post:
Stupid Cheap Line Array - Page 4 - diyAudio
He did exactly what I was thinking about. Same driver, same DEQ. So I guess it seems possible with these drivers after all.
I think it's time to built something or shut up ;)
 

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Discussion Starter #10
Ordered the TC9 drivers... I guess I'll find out if this works...
It will take me quite a while to build though. I'll try and put something up when I'm done.
 

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Discussion Starter #11
Almost ready to work on this project again. Bought a lot of the needed hardware and made some plans.
My cabinet plans look like this but are open to change as I have not cut anything yet:

The plan was to buit this from 18mm and 12mm MDF in a (very) big stack.
The 12mm would be used for bracing and the 18mm for the actual chambers.
Stacking gives me the opertunity to make a round shape on the outside, helping with the WAF (GAF in my case ;)) and limiting difraction while the inner cavity could be made up with a wavy shape to limit standing waves.

The four holes around the circumfence are used for dowels while the bottom stack used threaded rods to connect to the footplate.
The inner parts would get a round over but because I want to water cut these parts I haven't drawn that.
As a backup plan if water cutting is too expencive I have a friend who is willing to CNC these for me.

The outer shape would get a layer of fibreglass bonded to it to strengthen and smooth it out. The plan is to mount the drivers with the frame touching and fill in the sides to the outer box to have them close to flush.

Still have doubts about the MDF though. The thickness is not very stable and could be a problem when stacking this many layers. One of the reasons I haven't cut any yet. I'll look into a proper grade multiplex to see if that does any better.

Zaph has recently tested the vifa drivers I bought for this project. See:
Zaph|Audio look for Vifa TC9FD18-08
Distortion plot
Not bad at all! Now imagine 25 of those per side.... that would drop the distortion even lower. I'm starting to believe in this project! (of coarse I do, bought the drivers, the EQ and some other random stuff needed)
 

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Almost ready to work on this project again. Bought a lot of the needed hardware and made some plans.
My cabinet plans look like this but are open to change as I have not cut anything yet:

The plan was to buit this from 18mm and 12mm MDF in a (very) big stack.
The 12mm would be used for bracing and the 18mm for the actual chambers.
Stacking gives me the opertunity to make a round shape on the outside, helping with the WAF (GAF in my case ;)) and limiting difraction while the inner cavity could be made up with a wavy shape to limit standing waves.

The four holes around the circumfence are used for dowels while the bottom stack used threaded rods to connect to the footplate.
The inner parts would get a round over but because I want to water cut these parts I haven't drawn that.
As a backup plan if water cutting is too expencive I have a friend who is willing to CNC these for me.

The outer shape would get a layer of fibreglass bonded to it to strengthen and smooth it out. The plan is to mount the drivers with the frame touching and fill in the sides to the outer box to have them close to flush.

Still have doubts about the MDF though. The thickness is not very stable and could be a problem when stacking this many layers. One of the reasons I haven't cut any yet. I'll look into a proper grade multiplex to see if that does any better.

Zaph has recently tested the vifa drivers I bought for this project. See:
Zaph|Audio look for Vifa TC9FD18-08
Distortion plot
Not bad at all! Now imagine 25 of those per side.... that would drop the distortion even lower. I'm starting to believe in this project! (of coarse I do, bought the drivers, the EQ and some other random stuff needed)
Seems like a fun project! I have some questions about the build process. Water cutting I think would be ultra BAD, have you seen what happens to mdf when it gets wet? CNC is the way to go with this. I wouldnt worry about the thickness of each piece, as the variation is usually less than a mm per pice. Since you are going to fiberglass anyway, you can make up any height differences at that point, I would imagine it wouldnt be any more that a cm total. Also, since you are curving the chambers, you dont need the pattern on the inside, as the curving itself takes care of any possible standing waves anyway. Also, that will cost an arm and a leg in wood and be very heavy... if you are going to fiberglass anyway, why not build the whole thing out of 'glass, your back will thank you for it. Just build a stick frame with a wood baffle, and fglass the rest. It wil be plenty strong enough to contain the massive bass pulses from those 3 inch drivers! Just some thoughts. Also, you may want to look at porting that setup, I don't know if them being sealed will give you the bass you seem to want- unless of course you have a sub, then it's a moot point.
 

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Discussion Starter #13
Water cutting seems to be a good option with MDF according to some water jet cutting firms over here. It puzzles me as well. I think I will move to BB ply. It varies less in thickness than MDF with moisture differences. It will also be lighter. According to my CAD program the wood alone for one speaker will be about 30 KG.
I chose this method to have a rigid enclosure. A friend of mine steered me to fibreglass or Epoxy as well. I have thought about it but it has different problems to solve when I do. I'd probably opt for each driver in a seperate enclosure if I do.
For now I'm sticking to the stack of BB ply. There is another reason why I made the inner part that shape. The enclosure gets thicker and thinner in different places and I guess that could help me in resonances at little extra cost. The outer shape would help prevent diffaction.
Believe it or not, 25 of those little drivers are capable of bass extention way down to about 25 HZ! Together they have the radiating area of a driver bigger than a 15" cone but obviously limited by their induvidual 3.55 mm xmax. After playing with my current speakers with 15" bass drivers and observing their movement I start to believe in this concept. That's what the EQ is for, boosting the low end. Simulation proved it should be possible and much easyer, it has been done with the exact combo I have in mind.
See the link in post 9 above.

Came across the Anthony Gallo Reference 5LS today, fun to see similarities :)
vs


He uses 12 little woofers for bass extention, in my case all 25 are doing that job.
He has tweeters to help the upper end but the spacing is not better than the 25 woofers I'm planning (about the same in possible comb filter problems).
Both are crossover free (exept the low end of the Gallo).
His may have better diffraction control but I'll do the best I can.
My project uses DSP to get there while his can do without.
My budget is much lower (lol)
He designed his own, I borrowed the bigger part from Roger Russel ;) and gave it my own little twist.
 

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Water cutting seems to be a good option with MDF according to some water jet cutting firms over here. It puzzles me as well. I think I will move to BB ply. It varies less in thickness than MDF with moisture differences. It will also be lighter. According to my CAD program the wood alone for one speaker will be about 30 KG.
I chose this method to have a rigid enclosure. A friend of mine steered me to fibreglass or Epoxy as well. I have thought about it but it has different problems to solve when I do. I'd probably opt for each driver in a seperate enclosure if I do.
For now I'm sticking to the stack of BB ply. There is another reason why I made the inner part that shape. The enclosure gets thicker and thinner in different places and I guess that could help me in resonances at little extra cost. The outer shape would help prevent diffaction.
Believe it or not, 25 of those little drivers are capable of bass extention way down to about 25 HZ! Together they have the radiating area of a driver bigger than a 15" cone but obviously limited by their induvidual 3.55 mm xmax. After playing with my current speakers with 15" bass drivers and observing their movement I start to believe in this concept. That's what the EQ is for, boosting the low end. Simulation proved it should be possible and much easyer, it has been done with the exact combo I have in mind.
See the link in post 9 above.

Came across the Anthony Gallo Reference 5LS today, fun to see similarities :)
vs


He uses 12 little woofers for bass extention, in my case all 25 are doing that job.
He has tweeters to help the upper end but the spacing is not better than the 25 woofers I'm planning (about the same in possible comb filter problems).
Both are crossover free (exept the low end of the Gallo).
His may have better diffraction control but I'll do the best I can.
My project uses DSP to get there while his can do without.
My budget is much lower (lol)
He designed his own, I borrowed the bigger part from Roger Russel ;) and gave it my own little twist.
I thought that a bunch of little drivers would do the same job as a big driver as well. Here is what I did:
I had an Ascendant Audio Havoc 18 sitting in 4 cubic feet sealed @ 1500watts in my old suv. Sold the suv, went to a king cab Dodge Dakota. Wanted that windshield flexing bass I had from that 18 (30mm xmax!). Bought 8 Image Dynamics 8's @ 1200 watts total, which have a healthy 15mm xmax each. 8 8's equals to almost 3 15's. Didnt work out quite the way I wanted. It sounds great, dont get that wrong, but it doesnt have the extreme low end that my single 18 did. My point is, there is no way that you will get "room shaking bass" from a bunch of 3 inch drivers. While they may play to 25 hz on a meter, I can guarantee you wont HEAR 25 hz the same as with even a single 15. That setup may very well get good and punchy(60hz on up), but low end..? NO. if you want to have a skinny speaker and get room shaking bass, look into a tall, deep tower with subs sunk into the sides... similar to my latest DIY build:

thats 4 8's on front, a 3inch dome mid and a 1 inch dome tweet, with a 15 inch passive sub on the side.

granted mine are HUGE and extreme, but thats what I wanted. In your case, look at maybe 10 of your 3 inchers on front with a 12 inch sub in the side. That would be kinda nice, especially with a CNC on hand to shape the cabs( I didnt have one available).

Just my .02 from my experiences
 

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I thought that a bunch of little drivers would do the same job as a big driver as well. Here is what I did:
I had an Ascendant Audio Havoc 18 sitting in 4 cubic feet sealed @ 1500watts in my old suv. Sold the suv, went to a king cab Dodge Dakota. Wanted that windshield flexing bass I had from that 18 (30mm xmax!). Bought 8 Image Dynamics 8's @ 1200 watts total, which have a healthy 15mm xmax each. 8 8's equals to almost 3 15's. Didnt work out quite the way I wanted. It sounds great, dont get that wrong, but it doesnt have the extreme low end that my single 18 did. My point is, there is no way that you will get "room shaking bass" from a bunch of 3 inch drivers. While they may play to 25 hz on a meter, I can guarantee you wont HEAR 25 hz the same as with even a single 15. That setup may very well get good and punchy(60hz on up), but low end..? NO. if you want to have a skinny speaker and get room shaking bass, look into a tall, deep tower with subs sunk into the sides... similar to my latest DIY build:

thats 4 8's on front, a 3inch dome mid and a 1 inch dome tweet, with a 15 inch passive sub on the side.

granted mine are HUGE and extreme, but thats what I wanted. In your case, look at maybe 10 of your 3 inchers on front with a 12 inch sub in the side. That would be kinda nice, especially with a CNC on hand to shape the cabs( I didnt have one available).

Just my .02 from my experiences
Is your room 25cuft or much bigger? Getting bass in a car and bass @ home is not the same. In the car you have to account for cabin gain which helps getting more SPL out of your sub whereas in your house, you won't get much. Try your 8x8" in your car and I can tell you it will rape your single 15 in low end reproduction.

Low frequencies are reproduced with air moving, doesn't matter if you need 1000 2" drivers to equal the cone area of 1 x 18", if vd is the same, it "can" output as much SPL as that single 18".

Kelvin
 

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Is your room 25cuft or much bigger? Getting bass in a car and bass @ home is not the same. In the car you have to account for cabin gain which helps getting more SPL out of your sub whereas in your house, you won't get much. Try your 8x8" in your car and I can tell you it will rape your single 15 in low end reproduction.

Low frequencies are reproduced with air moving, doesn't matter if you need 1000 2" drivers to equal the cone area of 1 x 18", if vd is the same, it "can" output as much SPL as that single 18".

Kelvin
I dont think you understand what I was saying. I had an 18 in a car, was awesome at the lowest of lows. Replaced that with 8 8's, not so awesome at the lowest of lows.

Also, I have read and heard that exact same thing, that all you need is cone area. Well, I DID the change from one huge woofer to 8 small ones, and supposedly GAINED cone area doing that, and LOST extreme low end performance. Oh, by the way, when I did the swap from 1 18 to 8 8's, I also reduced cabin size, so I increased cabin gain and STILL lost bottom end. The reduction from 1500 to 1200 watts is immaterial. So, you can stand by your theories, but I have seen it in action- it seems you need a big woofer to get to the stupid lows, house or car.
 

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I dont think you understand what I was saying. I had an 18 in a car, was awesome at the lowest of lows. Replaced that with 8 8's, not so awesome at the lowest of lows.

Also, I have read and heard that exact same thing, that all you need is cone area. Well, I DID the change from one huge woofer to 8 small ones, and supposedly GAINED cone area doing that, and LOST extreme low end performance. Oh, by the way, when I did the swap from 1 18 to 8 8's, I also reduced cabin size, so I increased cabin gain and STILL lost bottom end. The reduction from 1500 to 1200 watts is immaterial. So, you can stand by your theories, but I have seen it in action- it seems you need a big woofer to get to the stupid lows, house or car.
The explanation is still easy to understand, the F3 was not the same between the 2 boxes. Do you know what was the F3 for the 8 x 8"?
Having a box that is too small for the 8s" can contribute to more SPL in the upper register (50Hz+) which let's you perceive it as less low bass. Even if you had more SPL @ 30Hz, your ears would say otherwise since you have so much more pressure up top.
Not saying you're wrong but there really is an easy explanation to what you experienced. Low freqs is air moving and nothing else. If it takes 1x8" with an Xmax of 30mm powered with 2000rms to put out the same SPL @30Hz as 1x18" with an Xmax of 5mm powered with 200rms - then so be it but the 8" WILL DO IT. It's not rocket science, just physics...

Kelvin

PS: sorry for OP for the OT.
 

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The explanation is still easy to understand, the F3 was not the same between the 2 boxes. Do you know what was the F3 for the 8 x 8"?
Having a box that is too small for the 8s" can contribute to more SPL in the upper register (50Hz+) which let's you perceive it as less low bass. Even if you had more SPL @ 30Hz, your ears would say otherwise since you have so much more pressure up top.
Not saying you're wrong but there really is an easy explanation to what you experienced. Low freqs is air moving and nothing else. If it takes 1x8" with an Xmax of 30mm powered with 2000rms to put out the same SPL @30Hz as 1x18" with an Xmax of 5mm powered with 200rms - then so be it but the 8" WILL DO IT. It's not rocket science, just physics...

Kelvin

PS: sorry for OP for the OT.
You can believe what you like, but the meter isnt wrong. Yes the box for the 8 8's is built to the smallest sealed box recced(.25 cu per sub min[2 cu ft total]-.35 is reccd), the 18 was also in a box that was a tiny bit too small ( 4 cubes was recced, 3.8 final). That sub hit 141.7 legal @ ~45hz, with it hitting [email protected] 20 hz. The 8 8's cant get past 138 outlaw at any freq, and barely breaks 130 @ 20 hz. Thats alot more cone area, with about half the xmax. I wish you had the subs to be able to do the experiment yourself, but most people dont have an 18 AND 8 8's laying around to just experiment with.

Here, spec it yourself:
Ascendantaudio.com
http://www.imagedynamicsusa.net/pdf/subwoofers/id/id8d4v3_sepcs.pdf

8 inch sd= 231 cm sq.... x8 = 1848 total sd
18 inch sd=1210 cm sq.
1.5 times the cone area with half the xmax but 1/4 of the low end performance.... something wonky there.
 

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Discussion Starter #19
Well I'm basing some of my hopes on this article:
IDS: The Return of Roger Russell | Stereophile.com

I wouldn't be surpriced if you could feel the bass from 2x 15" woofers better than from 50x 3.5". I have read about people mentioning "audiophile bass", where you hear it but don't feel it as much. Still seems strange as it's moving the same amount of air? Maybe the multiple small speakers react less with room nodes as in Geddes example of using more than one sub?
 

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Well I'm basing some of my hopes on this article:
IDS: The Return of Roger Russell | Stereophile.com

I wouldn't be surpriced if you could feel the bass from 2x 15" woofers better than from 50x 3.5". I have read about people mentioning "audiophile bass", where you hear it but don't feel it as much. Still seems strange as it's moving the same amount of air? Maybe the multiple small speakers react less with room nodes as in Geddes example of using more than one sub?
Its hard to say for me why it's different, subwoofery is right about the theory of it. But every time I replace a big sub with a bunch of small ones, I lose a lot of lowend. In the case of my car, I traded 20-50hz bass from the 18 for 40-90 hz bass with the 8's. Dont get me wrong, I still have bass all the way down but it is not nearly visceral as it is with that 18. I just wanted to give you a different point of view from actual experience than just throwing math at the problem. Maybe there is a mathematical reason why the difference is what it is, and we just havent found it yet.
 
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