Still can't decide - ported or sealed

[Newfiestang50]

Guys, I still can't decide on which sonosub to build, ported or sealed. I want this sub for 80% music, 20% movies. This sub will live in a room about 14'x19'x8' and I can only power this sub right now (budget constraints) with a NAD C272 (150 watts/ch), having said this, I do want the sub to be designed to handle a new more powerful amp in the future (Behringer EP1500).

I have been playing around with Unibox for last couple of weeks and have noticed a couple of issues that i cannot overcome.

First of all, it seems near impossible to build a ported Sonosub that is to be 20" dia tuned to 17Hz, any less than approx 250L, is this the case or am i doing something wrong?

Secondly, why is there a flat line right up to 1000Hz for the SS RL-p15 when I model it, that seems like a freq. that this driver should not be capable of producing, why is this happening?

Last question (ya right say you), will the NAD C272 be better powering the duel 4ohm coils individually or will it be better to connect the coils in series and bridge the amp to produce 400 watts/ch?

thanks

[Paul H]

Newf,

Send me your unibox file and I'll have a look at it.

Also from the rock,

Paul

[bobgpsr]

Secondly, why is there a flat line right up to 1000Hz for the SS RL-p15 when I model it, that seems like a freq. that this driver should not be capable of producing, why is this happening?

Enter the Le value for the RL-p15 and make sure you tell UniBox to include its effect. IIRC there is a box you have to check on the first page. When you get it done you then see a downslope for the higher freqs.

Bob

[ThomasW]

If you don't mind living with a taller tube build it ported and seal the port for music.

This has a slightly higher Fb than you wanted but you might find the info helpful

http://home.comcast.net/~audio-worx/page93PetesTube.html

[Newfiestang50]

There is no Le for the RL-p15 but there is a Ls and Lp, are one of those the same?

[ThomasW]

Use 5.3mH for the Le

[SteveCallas]

Since you only have 150 watts to work with, I think you've already answered your own question (ported). I don't know how soon you are looking to upgrade that amp, but if you don't plan on doing it for a while, you may want to go with a driver more sensitive than the SS.

Do you not want to go larger than 250 liters? To get the best overall performance with ported, you'll have to go big. As for the amp, I'd bridge it.

[Newfiestang50]

Since you only have 150 watts to work with, I think you've already answered your own question (ported). I don't know how soon you are looking to upgrade that amp, but if you don't plan on doing it for a while, you may want to go with a driver more sensitive than the SS.

Do you not want to go larger than 250 liters? To get the best overall performance with ported, you'll have to go big. As for the amp, I'd bridge it.

Thanks Steve, but isn't it 150 watts x 2 if I connect each ch of the amp to each voice coil, ie 300 watts is what the driver will see....Maybe i have it all wrong. In the Unibox model there seems to be over 100dB with only 200 watts, and my dedicated theator is only going to be 14'x19'x8'.

As for sensitivity, I am using the Integrated version of the same amp (C372) to run my PSB stratus Gold i's, which have been reviewed as being very hard to drive and this amp drives them very well. I tried an Adcom GFA 555ii, an amp noted for its "big" power reserves and it had a lot of trouble driving the golds, I eventually sold it and replaced it with the NAD and have been satisfied eversince. I think the NAD amps are way underated.

Having said this I was leaning in the direction that the C272 will not be enough power for this driver but just waned some opinions I guess if it will get me through a couple of months until I can get the EP-1500.

[SteveCallas]

100db output from a subwoofer really isn't that much, it's not like output from speakers. Considering you are building a dedicated theater, I'd bet you'll find yourself cranking that master volume up more than you are used to, and when you get a taste for powerful, low, clean bass, you'll only want more. You'll have to show some restraint until you get a pro amp, and your clip lights will probably be blinking pretty often

Do you have any enclosure size restraints though? For the dual 2ohm version, 260 liters with a 6" diameter 32.3" long port (15hz tuning) fed with 700-800 watts looks really good. 300 watts will put you in the 108db range.

[Newfiestang50]

100db output from a subwoofer really isn't that much, it's not like output from speakers. Considering you are building a dedicated theater, I'd bet you'll find yourself cranking that master volume up more than you are used to, and when you get a taste for powerful, low, clean bass, you'll only want more. You'll have to show some restraint until you get a pro amp, and your clip lights will probably be blinking pretty often

Do you have any enclosure size restraints though? For the dual 2ohm version, 260 liters with a 6" diameter 32.3" long port (15hz tuning) fed with 700-800 watts looks really good. 300 watts will put you in the 108db range.

Right now I have a Unibox model with 200L with a 6" dia 26.5" long port (18.5Hz) and i was thinking about the dual 4ohm, the manual for the amp states not to use bridge mode for an impedance lower than 8 ohms but I did have both the NAD C273 & C372 bridged running my 4ohm stratus gold's for a period of time with no issues except running fairly hot.

[Newfiestang50]

Another question, is there any need to brace the endcaps/plugs in a sonotube and if so what is the usual method of doing this, I was thinking treaded rod or something of that nature connecting the two endcaps together.

[dyazdani]

Right now I have a Unibox model with 200L with a 6" dia 26.5" long port (18.5Hz) and i was thinking about the dual 4ohm, the manual for the amp states not to use bridge mode for an impedance lower than 8 ohms but I did have both the NAD C273 & C372 bridged running my 4ohm stratus gold's for a period of time with no issues except running fairly hot.

If you wire the dual 4 ohm coils in series, it will be a 8 ohm load...

[ThomasW]

Threaded rods are unnecessary. And unless the tube is really big 24"+ in diameter, there's no need for endcaps thicker than 1.5.

[Newfiestang50]

If you wire the dual 4 ohm coils in series, it will be a 8 ohm load...

Sorry, I meant dual 2ohm wired in series, this could probably be a problem for the NADS but I really want to build this sub knowing that it will be powered in the future by the Behringer EP-1500.

[Newfiestang50]

Threaded rods are unnecessary. And unless the tube is really big 24"+ in diameter, there's no need for endcaps thicker than 1.5.

Thomas just to be clear, are you saying that there is no need for any bracing what so ever for a sonotube with a 20" dia?

[ThomasW]

There is no need for any bracing anywhere in a 20" tube sub.