How to choose correct Drivers for DIY speakers? need advice

[kapvin]

I am not sure why you got so offended kapvin? I didn't know that discussing about logical stuff makes you uncomfortable. What is the need to become so sarcastic and personal is not clear to me. Did I ever say that I am more knowledgeable than you? I am sorry if I had given you any such feeling. Infact I wanted you to summarize your thoughts since I was sure you know better. Its sad to read your post. :sad:

Santy,

I have no hard feelings. I will be happy to discuss each issue with you contextually and share my limited perspective offline over e-mail, when I can give you examples & data at leisure. I also do not have an overwhelming need to be right.

unfortunately am not able to visit the forum as often I as I wish, and replying on forum at odd intervals would cause huge discontinuity on a thread (which would have moved ahead).

just to reiterate the basic point I am making:

given a choice of Driver brand A and driver brand B, one can make an informed choice as which would fit better with a user's acoustic and design goals (again relative to what the goals are)

but to get into specifics without defining those objectives explicitly (or simply saying 2 x 8" vs. 1 12") is too much of an oversimplification - specially for a DIY thread.

regards

 

[lipimanas]

i think i am in a wrong thread. we are not so rich people to have a large hall separately for fitting 4 booming machines. we need it cheap and that is why in a DIY thread.
what i understood is that lesser the no of DIY stuffs, the better it is to spare time and money.

i am here because i choosed a driver from PE and found the shipping cost more than the driver itself. and at present trying for help from you all audio junkies for a solution.

need advice.

 

[manoj.p]

I think its better to invest in modding a room in order to kill standing waves rather than applying a band-aid of purchasing 4 subwoofers just to mitigate the effect.

Do you know how thick the absorber need to be, to kill a standing wave at 20 Hz? Wavelength of 20 Hz is 56 ft. How can you kill that wave in a room that is 20~30 ft long?

I agree that theaters are designed that way to keep standing waves out and minimizing odd order nodes along with damping.

But again would it be a wise solution to go and invest the amount on 4 set of Subs which can tame the problem to some extent and still you are devoid of SPL and impact.

I think the wiser solution would be to invest in modding the room shape internally in order to create better acoustic resolution and stack the Subs and feel the difference.

If you want to just mod the room and fill with bass traps (assuming you can trap all the waves, which you won't due to room size limitations), that will make the room sound dead. Now, to achieve required SPL, the amp and sub needs to be working hard. Multiple subs will even out peaks and dips, and wont make room sounding dead. However, this will only take care of sound upto 80hz. Above that, you still need to do room treatments. But those are manageable at 4 to 6 inch thickness.

As for the phase response, its never linear in any loudspeaker, unless its a single driver (or Danley's Synergy Horn). Any cross-over in the speaker has two drivers outputting same signal and the phase response is not linear. If the subs are placed symmetrically, those should be in phase. As for altering the phase response over a spectrum, its intended to take care of peaks n dips. What would you have otherwise, Nulls all over the spectrum?

Looks like you have done this. Let us all know if you have found an innovative way to kill the standing waves. We will also like to save money rather than spending it on subs.

 

[kanwar]

Do you know how thick the absorber need to be, to kill a standing wave at 20 Hz? Wavelength of 20 Hz is 56 ft. How can you kill that wave in a room that is 20~30 ft long?

If you want to just mod the room and fill with bass traps (assuming you can trap all the waves, which you won't due to room size limitations), that will make the room sound dead. Now, to achieve required SPL, the amp and sub needs to be working hard. Multiple subs will even out peaks and dips, and wont make room sounding dead. However, this will only take care of sound upto 80hz. Above that, you still need to do room treatments. But those are manageable at 4 to 6 inch thickness.

In Srinagar army cantonment auditorium, we had a same problem, the hall being rectangular was birth place of standing waves. So using an absorbent 5-6" thick is noway a solution neither its feasible. Parallel walls give rise to standing waves so in order to vanish them we modify the internal of the auditorium in to "TRAPEZOIDAL" shape with small sections along the length of the room, the width of the room was decreased since it covered the area but not more than 3 ft from both sides width wise, for a 50ft wide room with Trapezoidals sections in multiple columnar arrays gave us 6-12dB reduction in peaking at room modes/resonances at various frequencies under LF domain, the absorbent was just total 3 inches thick[1inch colossus fiber pressed absorbent+0.5inch free air space+1.5inch wooden casking] to kill the reverberation. Same we did with the false ceiling in which the hexagonal traps were laid and the end result was very good. The dips and peaking were reduced to the level where they were no longer harmful and rest of the room correction was done with EQ thru DSP. Total of 8 X 21" Subs were installed.

Now this thing is not an innovation, its just a scientific approach used by many people in this field. Physics is everywhere, apply and get results, don't run after band-aids. Making the room total sound dead is a mistake which some people do, dead rooms are not for enjoying lively scenarios, they are for testing transducers. Excess of everything is bad, one has to make an optimum approach.

If a large auditorium can be modded then why not do the same for home theater room which is small and the cost in doing so will worth every penny and would be still less than investing in 4 subwoofers. If people can go with costly projectors/screens/AVR processors, then why can't they follow scientific approach in room modding rather than going for band-aid solutions?

As for the phase response, its never linear in any loudspeaker, unless its a single driver (or Danley's Synergy Horn). Any cross-over in the speaker has two drivers outputting same signal and the phase response is not linear. If the subs are placed symmetrically, those should be in phase. As for altering the phase response over a spectrum, its intended to take care of peaks n dips. What would you have otherwise, Nulls all over the spectrum?
Looks like you have done this. Let us all know if you have found an innovative way to kill the standing waves. We will also like to save money rather than spending it on subs.

Well, if the reasoning is for passive speakers with passive XO in them, then i fully agree with you where the phase is nowhere coherent, but this is not the case with me because we use fully active system , each driver has separate active XO-EQ-AMP with zero passive crap. With active system you get much much better phase response/resolution. The key to make the phase coherent is to go for widest possible dispersion with certain set of frequencies using a dedicated driver, for example if we use HF with compression loaded horn and acoustic lens then you can get very good phase / time alignment along with wide dispersion but that must be active. Nulls are created when you have large phase variations and resultant cancellations, to avoid this one should try to use the driver in its natural flattest response curve without taxing it with over EQ, provided the room is treated acoustically.The dispersion has to be adequately projected towards the listener which is of prime importance.

 

[kanwar]

i think i am in a wrong thread. we are not so rich people to have a large hall separately for fitting 4 booming machines. we need it cheap and that is why in a DIY thread.
what i understood is that lesser the no of DIY stuffs, the better it is to spare time and money.

i am here because i choosed a driver from PE and found the shipping cost more than the driver itself. and at present trying for help from you all audio junkies for a solution.

need advice.

If you feel so, you are free to start a new thread.

Diy is fun

 

[Santy]

we are not so rich people to

What's your definition of rich and what you mean by 'we'? There are people here who have Rs. 50 lakh and above worth a/v systems.

 

[kapvin]

i think i am in a wrong thread. we are not so rich people to have a large hall separately for fitting 4 booming machines. we need it cheap and that is why in a DIY thread.
what i understood is that lesser the no of DIY stuffs, the better it is to spare time and money.

i am here because i choosed a driver from PE and found the shipping cost more than the driver itself. and at present trying for help from you all audio junkies for a solution.

need advice.

Hi,

the idea of DIY is on many dimensions

1. the sheer joy of doing things your selves and the " made that"pride that results from your creation
2. to meet specific goals which may not be addressed by mass market - on speakers, it could be enclosure size+bass extension; or particular finishes or anything.
3. to extract more "value" - now this is the biggie- sure it means you can do things cheaper - but cheaper is a movable scale -- and really when you try to get mass market quality below mass market prices that actually becomes difficult because mass market guys have scale on their side.

true value accrues when you look at mid-market or upper market quality at mass market prices.

as you found.. the shipping cost of drivers is high. but it is equal for a 20$ dayton versus a 100$ peerless (Assuming they have the same wt.).. so the "shipping" markup on the peerless is lower. for me, when i choose drivers (now don't laugh)- shipping weight is also a consideration. so a slightly more expensive driver, which is lighter *might* be preferable over a cheaper, similar quality but heavier driver. since your landed cost is likely to be same..


also when you build enclosures, the cost does not change whether you use cheap or expensive drivers (of the same size and say similar specs). given the enclosure costs and shipping is pretty constant, makes sense (at least to me) to import only "midmarket"and above drivers.

So, in India, currently (with the reality of duties and shipping), it is not easy to match the quality of 20k bookshelves at say, 10k.

but if you know what you are doing, it should be perfectly feasible to "match" a 100k+ bookshelf at 20-25k. this is my limited opinion.

Having said that, I would encourage you to speak to BBW distributors - who are dealers of SEAS. they have HI-FI drivers in stock most times, at -"cheaper than shipped to India + duty" prices. I purchased my subs from them - Seas L26ROY.

if budget is a constraint here is what I would suggest.

1. speak to BBW. figure out if you want to make a SEAS based design.

2. import only the tweeters, and midbasses. crossover components and cabinet hardware - you can buy in India. for importing follow my "based on experience rule""- buy lighter drivers . don't use direct shipping.. use borderlinx or equivalent. - it takes more time (2 shipments legs) but is worth it

3. for subs, please look in India. many car audio models (not all) actually have the specs to support in home use - the infinity 1260 is one, and the JBL GT5 can do well in a medium sealed box with eq. this is not a perfect solution, but a good compromise. and you can get car subs in the resale market very cheap

all the best...

 

[sbg]

... we need it cheap and that is why in a DIY thread.

I too beg to differ, apart from all the valuable comments from FMs, since you mentioned "cheap" :

...and since you seek advice, here I go.

You should not be looking at DIY etall. Period. unless you have all the facilities and "others time and money " at your disposal for free.

To give you an Idea in financial terms that ,there is an investment involved which may not be in the preview for few. ( otherwise , say, you can solder 2 wires on your kitchen stove , if you please - thats pure DIY too :indifferent14:, or Cut an 18mm MDF/ply with your kitchen or utility knife - no objections!).FYI,the investment, some times is equivalent to what commercial people do.For example, take sbg, he has Woodworking tools that most of the Professional Carpenters do not have - but their objectives are different for the matter or maybe that I'm not that skilled to make do without some of the specialized tools. And if you are a hardcore DIY (no - outsourcing: well other than non-raw material ) ,i.e. services and labor is what you save. This is besides your Patience,Time and a good nights sleep ( think "Opportunity cost" - if you are an economist/banker ) that you forego.

Here are some of the pointers one should be getting used to when we tread this path.

1. " Hell .~!@# .. how did this break! man! I purchased this just yesterday! $$$ "
   
2. " now what! I cross checked 5 times, how could the measurement go wrong!... do I need a specs now?
   ...
   na... my eyes are ok.
   ...
   AAAh, there ,the scale is wrong.
   
   na.
   oh well!!!!, why the hell they do not say it is in CMs and not Inches!"
   
3. "Why is this not heating up!
   ...
   ..
   7 days delivery time which I can get in 2 hrs at sp road.
   ...
   ...
   (after 4 hrs )
   Bloody hell, I can't even park my vehicle at SP Road.
   ...
   ...I'll come next weekend!"
   
4. "Aaah. need to make a small hole for a smaller Rat and a Big one for a bigger Rat to pass through"
   
5. "ok snap,It doesn't fit in there!"
   
6. "...another transistor and a resistor smoked now, maybe I have to change my "tolerance" now".
   
7. "for sure I need help... biwi! oh Biwi!"
   
8. "Boss,is it ok, if I do not come to office today.
   !@#@#% 420
   ##@$43
   no, no Boss, I have Fever"
   
9. " Darling , this will be my last project!.
   Hey, did you like that saree!
   ...
   ...
   no, no Its not that expensive, you can wear in that party next month!"
   
10. "... finally!..... mmmm should I keep this in bedroom or my living room".
    
11. "no doc, The screw driver fell on my leg.
    ...
    yes, It was heavy, and I had just sharpned it with an angle grinder when it fell"
    
12. " no honey, I've booked the ticket to Delhi.
    ...
    ...
    no, no, Their shipping cost was more than the round trips ticket and ...
    ...
    .. honey! I have to go alone... "
    
13. hey, this is unlucky number . ignore DIY, it is availabe on Ebay as CBU.

 

[Santy]

LOL.:lol: I full agree with sbg. DIY is very expensive when time and effort factors are shoved in and quite damaging when family relationship is brought in. However, for the same reason DIY gives you immense satisfaction because you have compromised / lost/ forgone all the above.

 

[kapvin]

1. " Hell .~!@# .. how did this break! man! I purchased this just yesterday! $$$ "
   
   
2. "for sure I need help... biwi! oh Biwi!"
   
3. "Boss,is it ok, if I do not come to office today.
   !@#@#% 420
   ##@$43
   no, no Boss, I have Fever"
   
4. " Darling , this will be my last project!.
   
5. "... finally!..... mmmm should I keep this in bedroom or my living room".
   
   
   
6. " no honey, I've booked the ticket to Delhi.
   ...
   ...
   no, no, Their shipping cost was more than the round trips ticket and ...
   ...
   .. honey! I have to go alone... "
   
   

so familiar... got a smile to my face..

the more we are different, the more we are same.

add some more..


1. it will will look much smaller after polishing et al.

2. just because I am designing it doesn't mean tweeters can be on the side panel.

3. no.. it won't sound good if it is bose sized. .. what?? you liked the sound in the bose showroom?

4. no cannot design a subwoofer to be hung on the wall.



... et al..

 

[manoj.p]

In Srinagar army cantonment auditorium, we had a same problem, the hall being rectangular was birth place of standing waves. So using an absorbent 5-6" thick is noway a solution neither its feasible. Parallel walls give rise to standing waves so in order to vanish them we modify the internal of the auditorium in to "TRAPEZOIDAL" shape with small sections along the length of the room, the width of the room was decreased since it covered the area but not more than 3 ft from both sides width wise, for a 50ft wide room with Trapezoidals sections in multiple columnar arrays gave us 6-12dB reduction in peaking at room modes/resonances at various frequencies under LF domain, the absorbent was just total 3 inches thick[1inch colossus fiber pressed absorbent+0.5inch free air space+1.5inch wooden casking] to kill the reverberation. Same we did with the false ceiling in which the hexagonal traps were laid and the end result was very good. The dips and peaking were reduced to the level where they were no longer harmful and rest of the room correction was done with EQ thru DSP. Total of 8 X 21" Subs were installed.

Now this thing is not an innovation, its just a scientific approach used by many people in this field. Physics is everywhere, apply and get results, don't run after band-aids. Making the room total sound dead is a mistake which some people do, dead rooms are not for enjoying lively scenarios, they are for testing transducers. Excess of everything is bad, one has to make an optimum approach.

If a large auditorium can be modded then why not do the same for home theater room which is small and the cost in doing so will worth every penny and would be still less than investing in 4 subwoofers. If people can go with costly projectors/screens/AVR processors, then why can't they follow scientific approach in room modding rather than going for band-aid solutions?



Well, if the reasoning is for passive speakers with passive XO in them, then i fully agree with you where the phase is nowhere coherent, but this is not the case with me because we use fully active system , each driver has separate active XO-EQ-AMP with zero passive crap. With active system you get much much better phase response/resolution. The key to make the phase coherent is to go for widest possible dispersion with certain set of frequencies using a dedicated driver, for example if we use HF with compression loaded horn and acoustic lens then you can get very good phase / time alignment along with wide dispersion but that must be active. Nulls are created when you have large phase variations and resultant cancellations, to avoid this one should try to use the driver in its natural flattest response curve without taxing it with over EQ, provided the room is treated acoustically.The dispersion has to be adequately projected towards the listener which is of prime importance.

ah, the classic non-rectangular, non-parallel theory to eliminate room modes. There is only one problem - modes aren't eliminated. Those are very much present in the room, but now at different location depending on how the room is shaped. If those location turn out to be where people seat, that problem would still be there. Moreover, those modes aren't as predictable as in a normal rectangular room. So, how does one decide how much splaying of walls is needed? There is no simple formula to predict it. So that just leaves people some trial and error which may not be practical when you are building the room. Also, it reduces the prime real estate in home environment where we do not have such big rooms to start with. If we have a front wall, reducing width means less distance available to keep front speakers away from corner (it still is a corner, may not be 90 degree but definitely between 90 to 100 deg).

Non rectangular room may help with some early reflections and flutter echo but that is easily taken care off by using diffusers in small room. For less than 300 hz, it just re-distributes the modal waves. One can do finite analysis, predict the new locations and design the walls such a way that it falls outside listening area. Or go with rectangular room where its quite predictable and take care of it with placement, diffusion, absorption and multiple subs. Plus this can work in case of living rooms, non dedicated theater rooms or existing rooms. It could be easier to buy more subs (could be smaller than having one big sub) and distribute in the room rather than erecting new walls hoping to solve the acoustic problem. Case of known devil vs unknown saint.

 

[navin advani]

Hi,
the idea of DIY is on many dimensions...
all the best...

That was a wonderful post. While shipping weight is not something I have considered in the past the next time I will.

My MO (if you can call it that) is to wait till I have the need for several speakers. If one orders say 12 or more drivers in one go the effort and shipping get amortised over all the drivers.

BTW I too use the SEAS L26ROY (with a Yumg Audio SD500 plate amp) along with many SEAS Excel drivers (W18ex, W22ex, W15ex, W12ex..). I did not know Gunbir (BBW) sells these in India or I might have saved myself a bit of money. You can see the system at the bottom of link below.

Pictures of Selah designed Tempesta Extreme and RC4 (no subwoofer)

Thanks again for a post that every bit echoed my thoughts.

 

[kanwar]

ah, the classic non-rectangular, non-parallel theory to eliminate room modes. There is only one problem - modes aren't eliminated. Those are very much present in the room, but now at different location depending on how the room is shaped. If those location turn out to be where people seat, that problem would still be there. Moreover, those modes aren't as predictable as in a normal rectangular room. So, how does one decide how much splaying of walls is needed? There is no simple formula to predict it. So that just leaves people some trial and error which may not be practical when you are building the room. Also, it reduces the prime real estate in home environment where we do not have such big rooms to start with. If we have a front wall, reducing width means less distance available to keep front speakers away from corner (it still is a corner, may not be 90 degree but definitely between 90 to 100 deg).

Non rectangular room may help with some early reflections and flutter echo but that is easily taken care off by using diffusers in small room. For less than 300 hz, it just re-distributes the modal waves. One can do finite analysis, predict the new locations and design the walls such a way that it falls outside listening area. Or go with rectangular room where its quite predictable and take care of it with placement, diffusion, absorption and multiple subs. Plus this can work in case of living rooms, non dedicated theater rooms or existing rooms. It could be easier to buy more subs (could be smaller than having one big sub) and distribute in the room rather than erecting new walls hoping to solve the acoustic problem. Case of known devil vs unknown saint.

The classic non-parallel wall theory is one of the best when dealing with room modes practically. It takes care of the room modes very well as far practical approach is considered. Acoustic treatments are not done with pen and paper only, A simple RTA can turn out itself as a good tool in predicting the behavior of the room, provided you have know how to do that. In our case we use CLIO 10 to do that taking measurements across the room and then shaping it for required response focused on the listener. Modding a small room will not take the same amount of space what it would take in large theaters. Smaller the room, lesser are the problems associated with it, keep this in mind. Placement of speakers and listening position also helps in solving the issues related to room modes and it can be done with much less budget than investing in 4 subwoofers.

Your reasoning to go for small subs against one large sub[or stacked smaller subs together] is vague because these 4 small subs would be placed in different locations which will not give you any depth in response in lower octaves in subsonic region because they won't sum up and what you get is poor phase response with shallow impact.

Modding a room is no big deal when someone is ready to invest in AV gear for home theater which needs a substantial budget. But wasting money on 4 Subwoofers just to appy band-aid for curing room modes and still no gain in SPL[subs at different location] obtained from them is utter waste of resources and is not a sensible approach. The real time theaters are prime examples of how things are done in right manner with thoughtful planning and execution, we don't see band-aid of 4 subwoofers in professional theaters.

For people with low budget and small room, one sub woofer is the only choice left. All you can do is to alter the placement in that case. But when you have a budget and good amount to invest its worthwhile to go with curing the room first.

 

[manoj.p]

The classic non-parallel wall theory is one of the best when dealing with room modes practically. It takes care of the room modes very well as far practical approach is considered.

Almost all the audio/acoustic books and courses do not recommend it. If it was most practical, all the acoustic engineers would have followed it.

Acoustic treatments are not done with pen and paper only, A simple RTA can turn out itself as a good tool in predicting the behavior of the room, provided you have know how to do that. In our case we use CLIO 10 to do that taking measurements across the room and then shaping it for required response focused on the listener.

Agree. But most diy home theater owners may not have access to measuring gear, let alone a calibrated measuring rig. In that case, its better to go with pen and pencil. Ask around here, how many have actually measured their room response?

Modding a small room will not take the same amount of space what it would take in large theaters. Smaller the room, lesser are the problems associated with it, keep this in mind.

Small rooms are harder acoustically compared to big rooms. Almost everywhere I have read or heard says it so. Not sure where you got this that small rooms are better compared to big rooms.

Placement of speakers and listening position also helps in solving the issues related to room modes and it can be done with much less budget than investing in 4 subwoofers.

Agree. Placement should be the first one to consider for correcting room problems. Room treatment can be next and eq the last resort and should be used sparingly.

Your reasoning to go for small subs against one large sub[or stacked smaller subs together] is vague because these 4 small subs would be placed in different locations which will not give you any depth in response in lower octaves in subsonic region because they won't sum up and what you get is poor phase response with shallow impact.

I am not recommending to go for small subs. What I mean is its better to have 4 small subs than a big one. I have seen people spend lots of money on one big sub. Ultimately, that sub gets level matched with speakers, so its loudness potential is not used much. What is better? Loud bass with stacked subs or flat, consistent bass with subs located in the room?

Modding a room is no big deal when someone is ready to invest in AV gear for home theater which needs a substantial budget. But wasting money on 4 Subwoofers just to appy band-aid for curing room modes and still no gain in SPL[subs at different location] obtained from them is utter waste of resources and is not a sensible approach. The real time theaters are prime examples of how things are done in right manner with thoughtful planning and execution, we don't see band-aid of 4 subwoofers in professional theaters.

For people with low budget and small room, one sub woofer is the only choice left. All you can do is to alter the placement in that case. But when you have a budget and good amount to invest its worthwhile to go with curing the room first.

Don't want to argue how theaters are setup, but they are nothing much to write about. I have seen Home theater rooms sounding better than commercial cinema theaters. Home theaters have better imaging, soundstage and clarity compared to cinema theaters. Also, don't forget, cinema theaters are quite big so do the modes are spaces closely. Plus, many theaters don't have audio system going below 40 hz much, that helps as well. When was the last time we have felt rumble in the theaters from bass? I am sure people have felt it in there home theaters.

 

[kanwar]

Almost all the audio/acoustic books and courses do not recommend it. If it was most practical, all the acoustic engineers would have followed it.

So as per you the acoustic engineers who use trapezoidal or spherical modding to counter standing walls are fools. As a reference the world renowned theater SKYWALKER RANCH of LUCAS [THX] has TRAPEZOIDAL WALLS & IMAX Theater is spherical dome shaped just for that very purpose. .The most profound benefit of the Trapezoidal room shape is the prevention of room modes to an extent which makes them no longer harmful. The low frequency standing waves are the most difficult to deal with. By eliminating parallel walls, standing waves can't form so this definitely helps. Try it in real, you will find the difference.

Agree. But most diy home theater owners may not have access to measuring gear, let alone a calibrated measuring rig. In that case, its better to go with pen and pencil. Ask around here, how many have actually measured their room response?

So your recommendation of 4 subwoofers is, i think well within their budget??:clapping:

Small rooms are harder acoustically compared to big rooms. Almost everywhere I have read or heard says it so. Not sure where you got this that small rooms are better compared to big rooms.

Small rooms have difficulty in achieving uniform response than larger halls, but treating small rooms is very much cheaper than modding a big theater. I got this info from learning from practical experiences which i have gained in past.

Don't want to argue how theaters are setup, but they are nothing much to write about. I have seen Home theater rooms sounding better than commercial cinema theaters. Home theaters have better imaging, soundstage and clarity compared to cinema theaters. Also, don't forget, cinema theaters are quite big so do the modes are spaces closely. Plus, many theaters don't have audio system going below 40 hz much, that helps as well. When was the last time we have felt rumble in the theaters from bass? I am sure people have felt it in there home theaters.

I think the term "Home Theater" has been derived from the professional theaters only, people want the same kind of experience in their home environment also, so in this way both are very much related. You cannot equate a cheap commercial cinema lacking on LF with properly execute home theater and same way you cannot compare reference pro -cinemas like IMAX or THX certified ones[with extended LF] with a normal home theater which is limited in budget.

Was that an excuse that you never visited a theater which lacks in rumble from bass ??? . In my experience we normally go down to 30hz flat and -3B point is again much lower.

As i already said, bigger rooms facilitate uniform FR and less interaction from room modes, but does that paves a way for trying non-sensible approaches when the scenario comes to small rooms? I think they can be treated as well.

 

[kapvin]

That was a wonderful post. While shipping weight is not something I have considered in the past the next time I will.

My MO (if you can call it that) is to wait till I have the need for several speakers. If one orders say 12 or more drivers in one go the effort and shipping get amortised over all the drivers.

BTW I too use the SEAS L26ROY (with a Yumg Audio SD500 plate amp) along with many SEAS Excel drivers (W18ex, W22ex, W15ex, W12ex..). I did not know Gunbir (BBW) sells these in India or I might have saved myself a bit of money. You can see the system at the bottom of link below.

Pictures of Selah designed Tempesta Extreme and RC4 (no subwoofer)

Thanks again for a post that every bit echoed my thoughts.

Dear Navin,

thank you for your kind words!

Weight played a role in my choice of amp as well and I am using a inuke 3000. (~625 true watts per channel, all at less than 18k landed). In the final system it will be driven through a BFD, which I have lying NIB.

Gunbir had sent me a DIY price list a while back, which included all usual Seas suspects. While he does not have all in stock, but I was given the impression that most key drivers where. And while the depreciating rupee might have resulted in a revision in those prices (which is why I'd think it appropriate to not share that list), suffice to say that they were reasonable. Had I not already made my driver purchases, I would have stretched to the Excels through BBW.

Thank you for also sharing your own DIY efforts. Seas drivers look amazingly beautiful. Selah should showcase your photos on their website. I was especially impressed at how you managed to countersink the non-circular drivers. it's a pain to do with a router! did you do it manually?

(Also is that an Accuton driver in your bedroom system?)

I've taken a different approach on my current project.. and that's a plunge off the deep end of the pool. I am designing my stuff from scratch. Maybe we can chat about that offline sometime.

take care

 

[navin advani]

Dear Navin,

Gunbir had sent me a DIY price list a while back, which included all usual Seas suspects.

Selah should showcase your photos on their website. I was especially impressed at how you managed to countersink the non-circular drivers. it's a pain to do with a router! did you do it manually?

(Also is that an Accuton driver in your bedroom system?)

I've taken a different approach on my current project.. and that's a plunge off the deep end of the pool. I am designing my stuff from scratch. Maybe we can chat about that offline sometime.

1. No problem. I can contact Gunbir and JB directly. We know each other - audio is a small world in India.

2. Yes all non circular drivers were routed the old fashioned way thank you for appreciating the effort.

3. Yes the bedroom speaker has a C50 with a RAAL. On second thoughts I should have used the C90 and crossed the Illuminators lower. Or even have replaced the Illuminators with Revelators but that is DIY - you need to make a educated guess.

4. All my past systems have been my own design, this is the first time I have turned to someone else for the design. Partly because my old copy of LEAP/LMS has been misplaced and also my copy of LsPCAD is gone. I moved a few times and the laptop which had LspCAD died while the LEAP/LMS dongle and software manuals have gone missing.

Anyway this thread is not about my systems. As far as trapezoidal rooms are concerned while they do reduce standing waves for most of us apartment dwellers this not a WAF compliant solution. Even making a room " acoustically trapezoidal" using heavy padding etc flies in the face of living room design.

As far as using 3-4 or more subwoofers are concerned my contention is that unless you have a system that can delay, decay and EQ each subwoofer independently this is a limited solution. Audessey's Sub EQ XT allows you to control 2 subwoofers.

One way to extend the functionality of Sub EQ XT is to use one big sub (15"+) for the very low bass (<40Hz) in the front and a second subwoofer that supplements the bass of the front speakers in the rear to reduce localization of the bass. Corner loading a sub is going to excite most nodes so if you are doing this try to ensure that the corner loaded sub is not reproducing the primary frequencies associated with the room nodes.

In the end every user's room, need and limitations are different. So each of us will have to arrive at our own peculiar set of compromises that work best for us.

There is no reason for us to compare our living rooms with any theoretical room or even a well designed movie theatre.

 

[manoj.p]

So as per you the acoustic engineers who use trapezoidal or spherical modding to counter standing walls are fools. As a reference the world renowned theater SKYWALKER RANCH of LUCAS [THX] has TRAPEZOIDAL WALLS & IMAX Theater is spherical dome shaped just for that very purpose. .

almost all the theaters I have seen have trapezoidal or curved walls and ceiling. I am not denying it. But its to take care of reflections. And not all the IMAX are spherical dome shaped, those are called Omni-max. Omni-max are shaped like a dome for video purpose for giving full immersion. Those omnimax movies are shot with fish-eye lens which is corrected when displayed on dome screen.

The most profound benefit of the Trapezoidal room shape is the prevention of room modes to an extent which makes them no longer harmful. The low frequency standing waves are the most difficult to deal with. By eliminating parallel walls, standing waves can't form so this definitely helps. Try it in real, you will find the difference.

Not true. As long as the walls are solid, there will be reflections and room modes will be formed. With different shapes, it will be at some other location, that's it. But your statement that standing waves can't form is misleading.

So your recommendation of 4 subwoofers is, i think well within their budget??:clapping:

I don't say that. I said if there is a choice of single sub vs multiple sub within budget, go for multiple. When I made that comment, it was about one big sub or stacked subwoofers. It's better to distribute.

And a generic comment about measuring gear. When it comes to that, I don't think its the matter of budget. If you look how much money people spend in their audio gear, they should be buying the measuring gear first. But No, that expensive audio gear is never measured in the room. Because people do not realize its important to know how room performs or think its not that important. I have seen people spending lacs of money on speakers but do not even use an SPL meter to level match them. They either set it by ear or use a SPL app on their iphone or android. In fact SPL meter or some measuring gear should be the first after buying such expensive gear.

Small rooms have difficulty in achieving uniform response than larger halls, but treating small rooms is very much cheaper than modding a big theater. I got this info from learning from practical experiences which i have gained in past.



I think the term "Home Theater" has been derived from the professional theaters only, people want the same kind of experience in their home environment also, so in this way both are very much related. You cannot equate a cheap commercial cinema lacking on LF with properly execute home theater and same way you cannot compare reference pro -cinemas like IMAX or THX certified ones[with extended LF] with a normal home theater which is limited in budget.

Was that an excuse that you never visited a theater which lacks in rumble from bass ??? . In my experience we normally go down to 30hz flat and -3B point is again much lower.

Well, I am glad you agree that not all the theaters are great and don't push that low. But my comment is still valid. Home audio system give much better imaging, soundstage and low frequency extension compared to commercial theaters. IMAX is usually better because they take special care and design that we get optimal experience. But when we talk about theaters, most of the time its commercial theater and there are very few which are good.

As i already said, bigger rooms facilitate uniform FR and less interaction from room modes, but does that paves a way for trying non-sensible approaches when the scenario comes to small rooms? I think they can be treated as well.

The approach you say which is non-sensible has been pushed forward by renowned audio engineers worldwide, including Dr Floyd Toole of Harman. I don't think I can say likewise for non-parallel walls approach for small rooms use.

 

[kapvin]

1. No problem. I can contact Gunbir and JB directly. We know each other - audio is a small world in India. I know - (esp the Car Audio world) - if you are who I guessed you are.

3. Yes the bedroom speaker has a C50 with a RAAL. On second thoughts I should have used the C90 and crossed the Illuminators lower. Or even have replaced the Illuminators with Revelators but that is DIY - you need to make a educated guess. - the c50 and the revelators could be even better for your application, that sub would take care of any bass spl deficit that a switch from illuminators to revelators could cause, plus I would be happy to snap up any pre-owned illuminators

Guys - this is a bit off topic now (and I am guilty myself).. Spiro started this thread in his holy grail quest to do DIY and get it right the very first time. Room treatment is hugely important, but that's not what this thread is about.


when I last spoke to Spiro, he was still neck deep in research.

@Spirovious, again let me reiterate; based on what I understood of your room requirements, enclosure size limitations, your budget and your expectations from your sound - the Peerless nomex HDS and the Vifa XT19 make huge sense and should not require complex crossover work.

what are the other drivers you are considering?

@Manoj.p - love your signature

 

[spirovious]

@Spirovious, again let me reiterate; based on what I understood of your room requirements, enclosure size limitations, your budget and your expectations from your sound - the Peerless nomex HDS and the Vifa XT19 make huge sense and should not require complex crossover work.

Thanks Kapvin,

I was thinking of Dayton earlier & this was in my mind-
TritrixMT_pg_1

But after talking to you ,I started checking out projects similar to what you suggested.

Anyone who wants to start DIY speakers can openly post in this thread.