Velodyne sms-1 ATC SCM35 and diy subwoofers response.

[flamingoboo]

Hi there,

i have spent the last couple of months building some diy subwoofers, from some good quality car audio subwoofers.



The full thread on the diy subwoofer build can be found here, www talk audio.co.uk/vbb/showthread.php?t=205577 (please put in the full stops and delete the space) any advice on improving these subwoofers would be greatly appreciated.

i am generally very happy with the sound and am constantly playing with the eq, the biggest change I keep making is to reduce the volume of the sub, Is that line too flat? Should it have more of a curve to it, in terms of sound, the bass has lost a lot of its boom and in someways its brute force, what I have seemed to have gained is a lot more musicality subtlety and much much more detail from top to bottom.

here is the response of just my front speakers crossed over at 80hz



here is the response of my main speakers and subwoofer with no eq applied



here is the response of my main speakers and subwoofer with equed with the velodyne sms-1



here is the settings page on the sms-1, i am using preset 1, is it ok to use the contour the way i have to reduce a small bump at 124hz.



The other problem that i have is that my room is very open plan.

The cinema room is joined to the kitchen, the other side of the room has a six foot wide by eight foot high opening into a dining room, which has the main staircase in it which goes up two flights of stairs into the loft conversion.

I am thinking of building some doors between the cinema room and the dining room would this help to gain some bass below 20hz? I have had some quotes to have these doors built, its not cheap so I would want to know if it would help the bass response and also does anybody know what type of construction method would be best, to stop the bass from going through the door.

cinema room, the staircase can be seen going up at the back of room.



adjoining kitchen



adjoining dining room with opening, leading onto the staircase


This is a great hobby that never ends.

[recruit]

moved to subwoofer forum.

[flamingoboo]

anybody?

[paulst10]

you are applying rather a lot of boost below 30hz mate .. are you sure the sub can cope with that ???

apart from that it doesnt look to bad .. and personally i found when the responce is too flat, the bass does seem to sound a little bloated .. IMO.

paul

[russ.will]

As per Paul, you're boosting like heck sub 30Hz. This is no doubt compensating for the natural roll off of a sealed sub and as you noted on the other forum, the Diamonds just don't go very low.

That said, many sealed subs apply some serious equalisation to extend response, but because it's carried out internally, people never know about it. It's not the same as boosting when applied to a ported sub. The dangers of boosting a ported sub come at the frequencies below port tuning. At this point the sub effectively becomes open baffle, with no resistance from the boxes internal volume and the driver can easily run out of travel.

This is can't happen with a sealed sub as the power requirements of a sealed alignment require exponentially higher levels of power to maintain an output level with dropping frequency and the driver is protected by the increasing pressure in the cabinet as the driver displaces more air, which requires the extra power, etc, etc.

As long as the amp is man enough and the drivers have the travel and power handling, then with caution it should be OK. I'd still settle for a slightly higher roll off if I were you. That 15Hz boost is adding nothing, but sucking loads of power, or at least restraint in the volume dept until you're sure of the systems (SMS-1/Amp/Subs) limitations.

I'd also try co-locating the subs. Put them on top of each other. They're quite close already, but co-location can boost output by 3-6dB at the listening position. This would give you a bit more headroom for running boosts low down and or reduce distortion, by allowing everything to be turned down a bit for a given listening volume. I'm also wondering if the dips at 40 & 80Hz are phase induced (ones a harmonic of the other) and I'm wondering if co-location may reduce the number of variables posed by having four sources of bass.

Otherwise, that's looking like a jolly good effort and one to be rightly chuffed with. I'm also quite surprised how even the unEq'd response is considering how open the room is to others - it's no worse than my room with all doors closed.

Russell

PS. I'm deeply jealous of the ATCs. It'd be nice if a few members could hear speakers like these. It'd alter their perception of what a really good speaker is.

[flamingoboo]

Thank you for the replies Paul and Russell.

I thought that I was adding a lot of eq at 20 and 15hz, but I incresed it gradually and it does seem to sound better with more authority rather than boom, but understand that this is more than ideal.

One of the reasons that i went down the diy route, was because i found the bass best in the right location which is on the right of the centre speaker, this was with my rel stadium, the only problem there is the height of the unit.

I am going to be running a front projection system, and a have a limitation to how high the sub boxes can be because the bottom of the projection screen is only 16 inches from the floor. When i put the rel in the right hand side of the room behind the right speaker where it would be out of the way of the projection screen that it just didnt integrate at all with the main speakers and was incredibly boomy, a bit long winded but this means that i cant co-locate the subs on top of each other.

Russell, looking at the response curve of just the man speakers, you can see the same dips at 45 and 80hz, this would lead me with my limited knowledge to think that this was due to room suckout and not phase problems, but maybe i am wrong?

Would closing off the room to the cinema with big heavy dors help the bass response below 20hz, as the sub wil only be loading the cinema room and kitchen as opposed to a three storey house.

I thought that having to subs apart would lead to a more even response across the room as well as a 3db increase in spl level?

this is my fist forray into diy speaker building, If i was to stuff the sub box with wadding do you think that it would help the subs go lower or help the sound quality?

I must say that the atc's are fantastic but incredibly power hungry, i havent heard any other speakers that are so nuetral with real tactile detail that can go as loud without any compression with so much composure.

[Nimby]

Do you mean you have no stuffing at all in your sub boxes?

Stuffing fools the driver into thinking it is in a larger box by converting acoustic energy into heat.

[Rob100]

Very OT I know, but you really should take better care of your discs and not leave them scattered all over the table

[russ.will]

Originally Posted by flamingoboo

Russell, looking at the response curve of just the man speakers, you can see the same dips at 45 and 80hz, this would lead me with my limited knowledge to think that this was due to room suckout and not phase problems, but maybe i am wrong?

No, you're quite probably right. Do measurements at other seating positions confirm this?

Originally Posted by flamingoboo

Would closing off the room to the cinema with big heavy dors help the bass response below 20hz, as the sub wil only be loading the cinema room and kitchen as opposed to a three storey house.

A smaller room will tend to provide more room gain, but from and starting at a higher frequency, so the chances are yes, it would help.

Originally Posted by flamingoboo

I thought that having to subs apart would lead to a more even response across the room as well as a 3db increase in spl level?

It may or may not lead to an even response (and your's certainly doesn't look too sad), but the latter is certainly true - the closer they get the bigger the gain.

Take everything I say with a pinch of salt. It's so hard to really diagnose these things unless you're actually in the room doing the EQing yourself. Another way of lookiing at it is, if you simply turned all of the sliders down by 6dB and the SMS-1s master volume up by 6dB, it would appear that you'd achieved a really flat response, with only two cuts and nobody would have mentioned boosting at all.

Russell

[flamingoboo]

Thanks again guys,

i don't currently have any stuffing in the boxes, but it is something that i am contemplating, I just dont want the sub to then see the box as being too big and therefore the bass being looser.

Rob, I'm with you 100% on keeping the disks properly, I think i have around 300 disks, so storage is an issue, what I have done is put all the boxes away, and have used large cd wallets to store them, much easier to find a film.

Can anybody help me with how heavy a construction the doors should be. Would one inch ply be ok, with a one inch each side of architrave, I think that I am going to try and build these myself, as the quotes that I have had are close to two thousand pounds. What I am going to do is build 4 eight foot high 18" wide doors and make them bifold. How hard can it be to build doors if I just use sheet materials like plywood, and then use architrave to make them attractive. What I need tot know though is if this would be good enough to contain the bass in the room.

In terms of the amount of boost that I have used low down, I think i will try and reduse the boost at 15hz and see how it sounds.

How important is the quality of an amp for subwoofer duties, How good can an amp be for something like a velodyne of B&W be etc when it is just a plate amp? Is my crown XLS602 good enough? I thought that it would be much better than a plate amp, but after reading another thread it seems that crowns are not that highly regarded for home cinemas? But is the quality ok for purely subwoofer duties?

[russ.will]

Originally Posted by flamingoboo

How important is the quality of an amp for subwoofer duties, How good can an amp be for something like a velodyne of B&W be etc when it is just a plate amp? Is my crown XLS602 good enough? I thought that it would be much better than a plate amp, but after reading another thread it seems that crowns are not that highly regarded for home cinemas? But is the quality ok for purely subwoofer duties?

I would have thought the crown to be spot on for subwoofer duties. It may not cut it as hifi amp, but subs require grunt rather than finesse - detail and refinement are not an issue, power is.

It makes me chuckle a bit though. What would you bet that those saying it's not a good enough amp, are the same ones buying speakers specifically to create a cinema sound balance? What do Crown make? Cinema amplifiers........

Russell