The Bargain Hunter's subwoofer ...

[mpw]

Let's take the case of a car-you get a whole raft of specs-length, width, height, ground clearance, engine displacement, transmission, fuel consumption, weight, fuel tank capacity-and so on-I could add to this list. Would all buyers consider all of them? I would guess not. Each buyer would consider the ones relevant to him/her.

GeorgeO

That's what I am asking. In case of a car the decision variables are more or less easily understood. Any person would understand things like engine CC, looks, safety features, comfort features etc...

But in case of a subwoofer driver...apart from budget...what would any 5 factors be ?

For example do we buy a subwoofer driver if QTS / Qes / sensitivity , X max...fall within certain values ?

What would those values be ?

Rgds

 

[captrajesh]

Good thread. Thanks to several discussions on HFV, regulars have more or less understood various terms of TS parameters. What these translate into is the next step. Hope gurus would chip in and there would be some healthy discussions in this regard.

I've come across this interesting site: Audio Innovation - by Dan Marx www.danmarx.org

Thought this would be useful to post a link here.

 

[GeorgeO]

Mahesh

My personal criteria was simpler-user feedback, weight(=build quality),Xmax, availability and price(discounts/deals). I didnt consider the T/S stuff at all. But each one has their set of factors, some want it downfiring, some of these drivers arent suitable for that. I wanted to use passive radiators in my design.

IMHO you cant pin it down here in India only to T/S params-like you said the Seas driver may not be available, whatever the reason, despite good T/S params, or there may be other similar constraints for some other drivers that may theoretically be available but delivery periods may be not viable for a builder. So you compromise and take a good management decision!

The three heavy duty sub drivers I bought were from Exodus(Shiva 12 inch). Lambda Acoustics(now AE Speakers) and Audio Concepts(ACI DV 12). I could bring them in cabin baggage from the US. I didnt look at TS Sounds because they were a bit too heavy to cart and pricey, and the venerable NHT 1259 was unavailable at one time. When I bought the Exodus Anarchy small driver for a tapped horn build, I didnt even look at the T/S parameters-was that an irrational/uninformed decision? No it was just an impulse buy!

Having built four powered subs I may not go through through the same rational decision making process as you because I may not go down that path again.

Cheers

 

[Hari Iyer]

@mpw
Since you are considering a sealed design IMO the Vas should be between 50 liters to 70 liters, the resonating freq between 20Hz to 30Hz and if a smaller box volume is a consideration then high Qtc of above 0.5 to 0.6 is required. Other parameters like Xmas should be reasonably good.Having too high a Xmas can also cause issues with cone stifgness and internal damping. Aim for the best surround damping material as the cone vibrations need good self damping parameters. Paper comes with moderately heavy comes are better due to good self damping. Do not aim for a very heavy cone as they may be too heavily damped. Also sensitivity of the woofer should be in the range of 85dB to max 88dB for offering good control and match with the low pass amplifier.
You will also benefit with tighter bass if the mechanical Q is lower, the Qm should be around 3 to 3.5 max.

 

[mpw]

Mahesh

My personal criteria was simpler-user feedback, weight(=build quality),Xmax, availability and price(discounts/deals). I didnt consider the T/S stuff at all. But each one has their set of factors, some want it downfiring, some of these drivers arent suitable for that. I wanted to use passive radiators in my design.

IMHO you cant pin it down here in India only to T/S params-like you said the Seas driver may not be available, whatever the reason, despite good T/S params, or there may be other similar constraints for some other drivers that may theoretically be available but delivery periods may be not viable for a builder. So you compromise and take a good management decision!

The three heavy duty sub drivers I bought were from Exodus(Shiva 12 inch). Lambda Acoustics(now AE Speakers) and Audio Concepts(ACI DV 12). I could bring them in cabin baggage from the US. I didnt look at TS Sounds because they were a bit too heavy to cart and pricey, and the venerable NHT 1259 was unavailable at one time. When I bought the Exodus Anarchy small driver for a tapped horn build, I didnt even look at the T/S parameters-was that an irrational/uninformed decision? No it was just an impulse buy!

Having built four powered subs I may not go through through the same rational decision making process as you because I may not go down that path again.

Cheers

George,

I followed almost the same path you mentioned. But i wanted to know / put myself in a true DiY'er shoes and hence all these questions..

rgds

@mpw
Since you are considering a sealed design IMO the Vas should be between 50 liters to 70 liters, the resonating freq between 20Hz to 30Hz and if a smaller box volume is a consideration then high Qtc of above 0.5 to 0.6 is required. Other parameters like Xmas should be reasonably good.Having too high a Xmas can also cause issues with cone stifgness and internal damping. Aim for the best surround damping material as the cone vibrations need good self damping parameters. Paper comes with moderately heavy comes are better due to good self damping. Do not aim for a very heavy cone as they may be too heavily damped. Also sensitivity of the woofer should be in the range of 85dB to max 88dB for offering good control and match with the low pass amplifier.
You will also benefit with tighter bass if the mechanical Q is lower, the Qm should be around 3 to 3.5 max.

Hari,

decorwise i am looking at a sealed box Outer dimensions of approx ( 16 inch wide by 16 inch high by depth to be adjusted accorsongly )

Prima facie your suggestion of Vas to be upto 70 liters is a bit scary. I hope i keep it as small as i can as i am not looking for Mariana trench levels.

regards
mpw

I've come across this interesting site: Audio Innovation - by Dan Marx www.danmarx.org

Thought this would be useful to post a link here.

Captain,

thanks !

If i compare dayton RC 10 HF ve Seas L26 ROY on parameters of

EBP
Qts
Qes

the Dayton looks better spec-wise but in Linear Coil travel the Seas is 14 mm Vs 12.4 mm of dayton. This itself needs to be co-related with the effective piston area

Seas 363 cm2
Dayton RC 10 HF 356 cm2

Also the Seas is 2 kg heavier than Dayton.

So is there more to it than meets the eye ? Maybne the effective piston area on the Seas and the linear travel on the Seas is > Dayton and so we get better & lower sound ?

Why is the Seas priced higher ( only brand value ?? ).

Maybe not.

Regards
mpw

 

[Hari Iyer]

Hari,

decorwise i am looking at a sealed box Outer dimensions of approx ( 16 inch wide by 16 inch high by depth to be adjusted accorsongly )

Prima facie your suggestion of Vas to be upto 70 liters is a bit scary. I hope i keep it as small as i can as i am not looking for Mariana trench levels.

regards
mpw

If a smaller Vb is desired then a higher Vas is a big no. But with reduced Vas the woofer will not be able to push enough air and could loose on the punch. In any case do not go for Vas less than 30 liters for a sealed enclosure else you may end up in too shallow a bass and the very purpose of going for a subwoofer gets defeated.
Give a good regard to Qms as the impedance at resonance can get higher with higher Qms. If the resonating frequency of the woofer happens to be in the 22Hz to 30Hz region, then the very low frequency from the subwoofer will get electrical impedance in that range and you may loose out at the bottom end. The acoustic impedance for a sealed enclosure being very high you may not also get much support from the box either. Hence all the output will have to be from the woofer cone. Woofers with lower Qms are suppose to offer lower electrical impedance at resonance.

 

[captrajesh]

@Mahesh, I do not know about you but most of us don't have sufficient technical expertise to even decipher the TSPs and select drivers, let alone designing the box and crossover. The learning curve is steep, long and could even be expensive. Your requirement (to augment low end response of your Merlins in your large listening room) is quite urgent I guess. If I were in your place, I'd do some research, shortlist a few proven designs (like GRR Servo sub for example) and try to listen (if possible) and finalise the kit.

I think FM Surrealistix had participated in the Group Buy and in fact made the GRR Sub. Check out his build here: http://www.hifivision.com/diy/29292-gr-research-n3-speakers-servo-sub-build.html

Also, FM Flash made a bigger 15" vented subwoofer by sourcing the kit from Rhythmik.

The former uses a 12" paper cone woofer from GRR while the latter is 15" Aluminnium cone from Rhythmik but both use the plate amp from Rhythmik. Incidentally, both the FMs are in Mumbai. Why not touch base with them?

 

[mpw]

Captain,

i agree with you on ;-

a. Most of us don't have sufficient technical expertise to even decipher the TSPs and select drivers....

I agree.

Most people just talk or know how to market - thats all.

b. I have heard the Rythmik F12 subwoofer in Mumbai for about half an hour. It was enough to convince me about the rationality of my room requiring a subwoofer ( at this stage ) vs an expensive amplifier.

Even if i were to buy that kit ( which i will not ), i am afraid i would have to go thru the same thing = to buying a good driver and a good plate amp separately and figuring out the cabinets etc..

c. I have a budget to meet - see the title :lol:

I am targeting @ Rs 45000 all inclusive.

I appreciate your concern about the learning curve and i think it better to go thru this learning curve than sit on the sidelines passing comments on "subwoofer integration".

Lastly - what is a proven design captain ?? The design maybe proven but the workability for me / you in our rooms is not.

regards
mpw

 

[keith_correa]

Don't get hung up on the TSP's in isolation - use WinISD or whatever and use the TSP's to model it to the volume you are constrained to based on the "workability".

 

[Hari Iyer]

I concur with Keith on this. winisd is a good simulation tool and has worked well for me for vented enclosures. Never build a sealed enclosure though. For sealed enclosure it uses a Qtc of =0.71 which cannot be modified. This gives the best trade-off of enclosure size and low frequency extension. At this Q the enclosure will be critically damped. I have also noted with winisd that sticking to the dimensions suggestion of winisd gives a better outcome than modifying it.

 

[mpw]

My aim is a sealed enclosure.

In fact i was on Win ISD now and i get a front chamber volume of 28.4 liters..

can you cross check for me please ?

My driver is the dayton RS 10 HF ( 4 ohm ) and the data sheet will be easily available online.

A super chilled bottle of :cheers: awaits !!

thanks

 

[keith_correa]

Cannot find data on RS 10 HF. Link please.

 

[mpw]

Dayton Audio RSS265HF-4 10" Reference HF Subwoofer 4 Ohm

Dayton Audio RSS265HF-4 10" Reference HF Subwoofer 4 Ohm

the spec sheet is on the above webpage links

thank you !

 

[keith_correa]

My aim is a sealed enclosure.

In fact i was on Win ISD now and i get a front chamber volume of 28.4 liters..

can you cross check for me please ?

My driver is the dayton RS 10 HF ( 4 ohm ) and the data sheet will be easily available online.

A super chilled bottle of :cheers: awaits !!

thanks

28.4 liters seems right in WinISD.
In Jeff Bagby's WBCD, with Ql=40 and Qa=10, 31 liters is maximally flat

Edit: I'd trust WBCD to be more accurate.

 

[mpw]

Keith

The parts express spec for the driver is 84 dB at 1w/m and 87.8 dB on Dayton site at 2.83v

Which one did u use ?

Rgds

 

[keith_correa]

Keith

The parts express spec for the driver is 84 dB at 1w/m and 87.8 dB on Dayton site at 2.83v

Which one did u use ?

Rgds

It's not a TSP so not relevant for modeling

Edit: It's derived based on the TSP's so:

SPL 1 W / Meter (dB) = 82.05
SPL 2.83V / Meter (dB) = 84.95​

28.4 liters seems right in WinISD.
In Jeff Bagby's WBCD, with Ql=40 and Qa=10, 31 liters is maximally flat

Edit: I'd trust WBCD to be more accurate.

I now put in a series resistance of 0.5 to factor in the increase in voice coil resistance with temperature and now I get 24 liters as flat. But I'm being anal here

 

[mpw]

keith,

Now let me understand..

to get the box OUTER dimensions, i will need to add 28.4 + volume of damping material + volume of any bracings + volume corresponding to the 1 inch thick-ness of the MDF i plan to use for the cabinet and add 1 inch thickness for the front baffle as i plan a 2 inch thick front baffle + volume of the Hypex DS4.0 enclosure which i plan to build at the rear of the subwoofer cabinet.

or am i messing it up ?

regards

for those of you interested... here is a nice link on this dayton rc 10 HF driver ( 4 ohm )

DIY dual Dayton 10" sealed subs - piano black | The Emotiva Lounge

regards

 

[keith_correa]

keith,

Now let me understand..

to get the box OUTER dimensions, i will need to add 28.4 + volume of damping material + volume of any bracings + volume corresponding to the 1 inch thick-ness of the MDF i plan to use for the cabinet and add 1 inch thickness for the front baffle as i plan a 2 inch thick front baffle + volume of the Hypex DS4.0 enclosure which i plan to build at the rear of the subwoofer cabinet.

or am i messing it up ?

regards

28.4 [or whatever you go with] is the inner volume required. Volume of the damping material is never taken into account. So the volume that should be available to the driver is 28.4 [or whatever] which means that 28.4 + any other volume taken up [bracing, plate amp volume occupied INSIDE the enclosure, volume that the driver displaces inside the box] is the inner volume you should end up with. The outer dimensions then depends on thickness of the MDF used that encloses this inner volume.

 

[mpw]

:signthankspin: keith.

The beer awaits ! :cheers:

Actually its now time for me to get the cabinet done up.

Hope to post some pics of that.

I have the Dayton driver with me but since there are so many photos of it on the net i didnt want to put up a pic.

regards
mpw

 

[keith_correa]

The beer awaits ! :cheers:

I'll send you the bill. hyeah:

I'll give you a free tip which could earn me more beer:

Look up Basotect. They are sold retail under different brand names - Mr. Clean etc. Considering what they can do, they are inexpensive. Line the inner walls with these. Then stuff the box. If you use these, you can get away with using 0.75" thick walls too.