Novice stereo subs project with stereo amp.

[PJeff]

Hi everyone,
I've been wanting to add a sub to my stereo system (SqueezeBox Duet, ONIX SP3(tube amp) and PSB B25's(monitor speakers) for a little while now and I've been contemplating sub kits like Rythmik to name one... But, I also have a Rotel amp (RA-985BX) 100W/8ohms sitting on a shelf and was wondering if it would be possible, as a cheaper alternative, to use it with something like a Reckhorn F-1 Stereo from CSS Audio to drive a stereo pair of not too expensive high efficiency sub drivers and maybe even use the enclosures as speaker stands? I'm thinking 12'' drivers. Performance goal is to have well integrated with really good transient low frequencies for hi-fi music and occasional movies.

What do you think of all this? Would it work?

Cheers,
PJeff

 

[chris661]

Yeah, it could work, but I think we still need more info...

How low do you want to go? (using headphones and a signal generator is good for choosing...)
What size is your room?
How loud do you want to go?
How big can the subwoofers be?
What's the budget?

For a start, though, I'd begin playing around on winISD.
I use a pair of 8" drivers in a smallish sealed box, with a linkwitz transform circuit, which enables them to go to 28Hz. ESP - The Linkwitz Transform Circuit - if you don't want to go that loud, applying this could be for you.
Unfortunately, there aren't any high efficiency 12" subwoofers. Hoffman's Iron Law means you can have only two of the following: small size; high efficiency; low frequency extension. That applies to cabinets, too...

 

[PJeff]

Yeah, it could work, but I think we still need more info...

How low do you want to go? (using headphones and a signal generator is good for choosing...) fairly flat to 30hz would do it
What size is your room? about 15'x26'x8'high
How loud do you want to go? I do not have a way to measure that but from what I've read I guess 90-95dB max. I don't need really loud capabilities
How big can the subwoofers be? I guess around 3 cu-ft.(As stand mounts it would be something like 22''Hx12'Wx20''D inside dim.)
What's the budget? is 250-300$ realistic (including the F-1Stereo at 124$ but excluding the cabinet) for a clean, dynamic, good transient sound?

For a start, though, I'd begin playing around on winISD.
I use a pair of 8" drivers in a smallish sealed box, with a linkwitz transform circuit, which enables them to go to 28Hz. ESP - The Linkwitz Transform Circuit - if you don't want to go that loud, applying this could be for you.
Unfortunately, there aren't any high efficiency 12" subwoofers. I do not mind a smaller driver... as long as it does the trick... but I was thinking of an economical alternative to something like the AE Speakers Lambda serie if such a thing exist(I do not need it's high frequency capabilities so that's what makes me think there might be a cheaper alternative focussing on the lower end of the spectrum while keeping the high sensitivity???).
Hoffman's Iron Law means you can have only two of the following: small size; high efficiency; low frequency extension. That applies to cabinets, too..

Thanks... that make's a lot of sense!

 

[chris661]

Unfortunately, 12" is considered small by many...

Given 30Hz as a target (pretty sensible...), a pair of 12" drivers should suffice. A single 12" driver, in a sealed cabinet, would move 8mmp/p (peak to peak) to hit 30Hz at around 93dB.
Dual drivers would half the excursion, so most pro audio drivers will do the job.

I have an Eminence Beta 12, and that does the job well. It has reasonable linear excursion, but (perhaps more importantly) around 99dB@1w efficiency. With a Linkwitz Transform in place, you'll be going at around 40w total output (2x20w seems reasonable), hitting 95dB at 30Hz. The cabinets would be 50 litres each. They're £40 each here, which is a bargain, in my opinion. It's not a driver designed for subwoofer use, but it has enough excusion and power handling to be a good option for a lower budget.

Edit - just noticed your budget. Perhaps either something better by Eminence (or another Pro Audio manufacturer), or something aimed more at the hifi market would be in reach.

The Eminence LAB12 could be something to consider. More excursion, but lower efficiency (still not bad, though)

 

[Spasticteapot]

I might point out that Hoffman's Iron Law does not say that deep bas has to preclude efficiency. It just says that you need a freakishly enormous box.

I've seen some nice things done with small drivers and tapped horns - you could conceivably build some 30hz horns using Tang-Band 6" subs that you could use as speakers stands. While the efficiency isn't awe-inspiring, it's hard to argue with the form factor.

You can see what I'm getting on about here:
Tapped Horns

 

[PJeff]

Thank's Chris661 for your input. Your suggestion of the Eminence LAB12 hints me to be a little clearer about my budjet... I'm thinking around 250-300$ for the crossover (F-1Stereo-124$) and TWO drivers. The Eminence Beta12 looks within the budjet...

Thank's Sparticteapot. Wow... pretty impressive for a 6.5'' driver in this Tapped Horn. I'm not familiar with tapped horn but this avenue seams interesting but i'm curious to know anyone's opinion about the advantages AND disadvantages of such a design. I mean there MUST be compromises to be made to get that kind of performance from only a 6.5'' driver!! Here's a little reminder... I'm looking for a clean, dynamic, good transient that will integrate well with hi-fi music.

Two good but very different possible designs here and I need help to make the right choice for my application...
Very good day to you all,

 

[PJeff]

Also, If anyone has any experience with the Reckhorn F-1Stereo I would appreciate to have your inputs. Is it a worthy device? If I also use the satellite high pass for the monitors, will it deteriorate the signal or should I strictly use it for the subs and try to work with the monitor's natural roll off? Will the lack of phase adjustement will give me headacks for the integration to my system?

A great weekend to you all!

 

[chris661]

It would be far far cheaper to build something yourself. There are lots of active crossovers out there.
Active Filters Those will cost next to nothing to build on some stripboard or something like that. It would be better to play with $5 of components, than $135 on something that does the same thing. I made the circuit shown above (just the low-pass), and used a 100k stereo pot instead of those resistors. The result was a variable cross-over. This won't work for the high pass. You'll need a variable capacitor for that...

WRT the tapped horn, there's a couple of compromises that I know of... The size is still bigger than a sealed box for the same driver, the construction becomes more difficult (lots of pieces, and the all have to be in exactly the right place). In some cases of horn loading, you can't hear the driver hit the stops, so you have to be careful. Dunno if that applies to tapped horns.
On the positive side, it gives good low frequency extension, and brings efficiency up.
For the TB driver, you can get similar extension from a ported box, but the overall efficiency stays low... (still, by having a smaller cabinet when vented, you could add more later...)

Anyway, I'd cross your monitors over. Saves them going to any excursion when you've got a sub to do the pushing.

Ohhh - just noticed that the frequency response of that TH has boundry gain added (ie, on the floor, up against a wall...). Add that to a sealed design, you can also get pretty low (before even adding a Linkwitz Transform).

Chris

 

[bjorno]

..I might point out that Hoffman's Iron Law does not say that deep bas has to preclude efficiency. It just says that you need a freakishly enormous box...

Agree, Here is an inexpensive T-TQWT to consider:..

b

 

[PJeff]

It would be far far cheaper to build something yourself. There are lots of active crossovers out there.
Active Filters Those will cost next to nothing to build on some stripboard or something like that. It would be better to play with $5 of components, than $135 on something that does the same thing. I made the circuit shown above (just the low-pass), and used a 100k stereo pot instead of those resistors. The result was a variable cross-over. This won't work for the high pass. You'll need a variable capacitor for that...
Humm... didn't see that one coming but I really like the idea (not only for cost reasons but personal interest)... except that, no matter how easy this could be, I'd need major help along this new experience. I'll have a look around to see if I can find someone I know who could assist me with this... And what difference does it make that the reckhorn unit is powered(powercord and transformer on it) and, from what I can see, the schematic from Linkwitzlab isn't?

WRT the tapped horn, there's a couple of compromises that I know of... The size is still bigger than a sealed box for the same driver, the construction becomes more difficult (lots of pieces, and the all have to be in exactly the right place). I can stretch the size factor if technically justified for better performance. In some cases of horn loading, you can't hear the driver hit the stops, so you have to be careful. Dunno if that applies to tapped horns. Me neither
On the positive side, it gives good low frequency extension, and brings efficiency up.
For the TB driver, you can get similar extension from a ported box, but the overall efficiency stays low... (still, by having a smaller cabinet when vented, you could add more later...)

Anyway, I'd cross your monitors over. Saves them going to any excursion when you've got a sub to do the pushing. Any loss or garbage added to the signal to the monitors doing that? My goal is to eventually change my speakers for something more neutral and transparent that I will build from a proven design.

Ohhh - just noticed that the frequency response of that TH has boundry gain added (ie, on the floor, up against a wall...). Add that to a sealed design, you can also get pretty low (before even adding a Linkwitz Transform).

Chris

With my somewhat limited knowledge, What I'd like is the best performance possible following my basic requirements, with 100W/8ohms stereo and for the budjet I have... ie around 50$-75$ per driver. Already, there seem to have a few possibilities and that's great but I feel the need to elaborate a strategy to help my confusion. Could we adopt a strategy like, for exemple, starting by choosing a driver meeting my budjet and performance requirements and then choosing the type of enclosure to get the most from it...?? This is a simple suggestion to help my little neurons here... How would you guys do that?

Cheers

 

[planet10]

Also, If anyone has any experience with the Reckhorn F-1Stereo I would appreciate to have your inputs. Is it a worthy device?

It is a good device for the money. If you get one of the modded units Bob sells. Or...

I am clearing out some units from Bob, that came without labeling. They will be cheap. Required mods will be documented. Parts kits can be had. Or you can get a unit that Duo has modded. They come with the labels, but you will have to install yourself.

The price will be such that it will be hard to build one as cheap.

dave

 

[chris661]

It wouldn't be easy to replicate all of it, but it would be easy enough to replicate the variable low pass filter.
You'd need 2x the filter I posted (it is powered, btw, but that's not shown. I power mine with around 12v, tapped off the pre-amp PSU), and replace all 23.7k resistors with a 4 channel potentiometer (that way, you get stereo).

I'd go with Dave's offer, but getting it as a kit would give you some experience of building audio stuff...

Anyway, for driver choice, it's going to be a trade-off, but staying around 12" would probably be wise for a subwoofer (it's a pretty common size, so you've a better chance of finding something you're after. That said, if you see a tapped horn, and it's easy enough to construct etc, don't rule it out based on driver size...

Looking on parts express (where will you be ordering from? - I guessed there, but I could easily be wrong), the 12" PA woofers are pretty cheap, but the "hifi woofers" start out equally cheap, but get a lot more expensive very quickly...

Chris

 

[PJeff]

It is a good device for the money. If you get one of the modded units Bob sells. Or...

I am clearing out some units from Bob, that came without labeling. They will be cheap. Required mods will be documented. Parts kits can be had. Or you can get a unit that Duo has modded. They come with the labels, but you will have to install yourself.

The price will be such that it will be hard to build one as cheap.

dave

Hi Dave
That's a very interesting option. Do they have ALL the mods like the units available at CSS? What would be the prices like for one of these with parts kits(I would only consider this option if the needed mods are very well documented and easily doable by a newbie like me) and how about one of the units Duo has already modded?
Thanks

 

[PJeff]

It wouldn't be easy to replicate all of it, but it would be easy enough to replicate the variable low pass filter.
You'd need 2x the filter I posted (it is powered, btw, but that's not shown. I power mine with around 12v, tapped off the pre-amp PSU), and replace all 23.7k resistors with a 4 channel potentiometer (that way, you get stereo).

I'd go with Dave's offer, but getting it as a kit would give you some experience of building audio stuff... I just might do that!

Anyway, for driver choice, it's going to be a trade-off, but staying around 12" would probably be wise for a subwoofer (it's a pretty common size, so you've a better chance of finding something you're after. That said, if you see a tapped horn, and it's easy enough to construct etc, don't rule it out based on driver size...

Looking on parts express (where will you be ordering from? - I guessed there, but I could easily be wrong), the 12" PA woofers are pretty cheap, but the "hifi woofers" start out equally cheap, but get a lot more expensive very quickly...

Chris

Hi Chris,
Living in Canada, I will try to avoid the package to have to go through custom$$$ so I'll probably be buying canadian. Here we have Solen in Ontario and CSS in BC but neither of them sells Eminence... but through the Eminence website I found this distributor in ontario Q-Components.

Hi Dave(Planet10),
you being in the fullrange business which are also usually high efficiency, I'm very curious to hear your inputs about drivers meeting my needs?


So I'm still very open to suggestions about drivers you think might fit my needs. So far, the Eminence Beta12 (I guess the A2) is pretty much the one topping the list.

A very good day to all,
PJeff

 

[chris661]

Yeah, the A2 is the one I use.

There's other manufacturers that do similar drivers. I know Celestion has a much wider choice of 12" mid-bass drivers, ranging from low resonance, low efficiency (around 88dB) right through to 100Hz resonance, 108dB@1w guitar speakers.

I haven't had any experience of the brand, but messing around on winISD should give you a good idea.

Edit - here's something that looks promising...

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-490
Efficiency still in the 90s, but I expect the extra Xmax and lower resonance would help things out.
I used a pair of 8" unshielded versions in a single sealed box, which does pretty well. The Xmax is only a small part of how far those drivers go. Mine are rated at 3mm, but will go to around 16mm p/p before hitting the stops.

 

[PJeff]

Yeah, the A2 is the one I use.

There's other manufacturers that do similar drivers. I know Celestion has a much wider choice of 12" mid-bass drivers, ranging from low resonance, low efficiency (around 88dB) right through to 100Hz resonance, 108dB@1w guitar speakers. Interesting suggestion... I'll have a look.

I haven't had any experience of the brand, but messing around on winISD should give you a good idea. I'll download it and will see what I can come up with using this...

Edit - here's something that looks promising...

Dayton SD315-88 12" Shielded DVC Subwoofer | Parts-Express.com
Efficiency still in the 90s, but I expect the extra Xmax and lower resonance would help things out.
I used a pair of 8" unshielded versions in a single sealed box, which does pretty well. The Xmax is only a small part of how far those drivers go. Mine are rated at 3mm, but will go to around 16mm p/p before hitting the stops.

Wait a second!!!........Your comment about the 8'' drivers makes me think about a speaker projet I'm planning on doing when money will allow using a pair of Seas CA22RNX. Even though they're a little over my budjet, I would already have them for my future projet... They have a relatively high efficiency and a decent Xmax I think(saying that with my limited knowledge)... Do you guys see a way to use those to achieve what I want right now?

Cheers!

 

[planet10]

Do they have ALL the mods like the units available at CSS? What would be the prices like for one of these with parts kits(I would only consider this option if the needed mods are very well documented and easily doable by a newbie like me) and how about one of the units Duo has already modded?

We did the units Bob is selling (or Duo did, i just co-ordinated).

Note: these units come with the labeling on a separate plastic sticky sheet. You can completely dissasseble and install as originally intended, cur out the labels parts and stick them where they should be (as i did on mine), just slap it on the top. or leave them off.

Units are silver or black (silver knobs in both cases). Labels being black on clear are not that useful on the black units as far as sticking them

Price is going to be $45 /unit, $50 with a bag of parts or you pay Duo his hour ($50) for him to execute all the mods (volume control isolation, regulated supply, stereo and gain mod)

Shipping (and GST, PST, HST if applicable) on top

dave

 

[planet10]

Here we have Solen in Ontario and CSS in BC but neither of them sells Eminence... but through the Eminence website I found this distributor in ontario Q-Components.

Bob sources from PE fairly regularily so he can get eminence. Living 4 miles from the USA, he has an excellent scheme for getting things across the border.

Q (aka McBride) have, in my limited experience, also been good and are quite a few provinces closer to you.

you being in the fullrange business which are also usually high efficiency, I'm very curious to hear your inputs about drivers meeting my needs?

I'll hsvr to go back and look. With the demise of the FExx7 series of drivers, high efficiency choices will soon be halved (but i have stock on all of them ATM). We are also doing more & more Mark Audio. In a lot of cases the best choice comes down to what amp you will be using?

dave

 

[jleaman]

It is a good device for the money. If you get one of the modded units Bob sells. Or...

I am clearing out some units from Bob, that came without labeling. They will be cheap. Required mods will be documented. Parts kits can be had. Or you can get a unit that Duo has modded. They come with the labels, but you will have to install yourself.

The price will be such that it will be hard to build one as cheap.

dave

Interesting, might have to grab one of these.. Right after you email me back lol!

 

[planet10]

yes i should be able to help/// where is the parts list?

dave