Reinvent older sealed sub box, help?

[everettT]

No, I couldn't. If I did it would look horrible because the oak veneer ends at that face and the grille meets it.

Thanks anyhow.

I get the concern, but a solid black baffle, especially with cover should be acceptable. It's just too easy not to consider. Straight glue would probably be more than enough, could add a couple of brads or finish nails to hold it while drying.

 

[KenM10759]

Perhaps you're right. If whatever drivers are compatible need additional depth and/or diameter, I'll consider that. My preference is to keep it original so the OE parts could be swapped in if a future owner ever wanted that.

Thank you.

 

[MrBoat]

I have glued in an appropriate sized 'cookie' in a driver hole before, so's I could have a new center for a router jig. When I built the Continuums, I had cut the recesses before adding the veneer for a test drive to see how much effort should be put into the finish. I didn't want to try to find the edge of the recess with something like a utility knife again so, I glued in a blank and used the router to find it.

Worst case scenario in these situations being, the new driver is smaller. Still, one only need to make a blank for the hole, epoxy it in and do the appropriate cosmetic body work and start with a new center and repaint or whatever.

There's many ways to skin this cat, which is telling of how useful a router is, in general.

 

[KenM10759]

So I'd researched this extensively and came up with some options @ Parts Express. I then sent an e-mail to their tech support, and got a recommendation similar to what I came up with. It will require zero modifications to the cabinet for the driver, and something cheap, easy and reversible for getting the amp onto the box. They had come up with a Dayton 250 watt plate amp, I simply changed it to a higher-level one with a good DSP so I can really get the most out of it.

Still overkill?

 

[MrBoat]

So I'd researched this extensively and came up with some options @ Parts Express. I then sent an e-mail to their tech support, and got a recommendation similar to what I came up with. It will require zero modifications to the cabinet for the driver, and something cheap, easy and reversible for getting the amp onto the box. They had come up with a Dayton 250 watt plate amp, I simply changed it to a higher-level one with a good DSP so I can really get the most out of it.

Only one way to find out.

 

[KenM10759]

And I will. It's on the way. Slowest way (free) shipping but I'm patient.

Edit: Well I'm a bit surprised. UPS "My choice" subscription shows two packages from PE as showing up here tomorrow, Saturday! Could be an exciting weekend.

 

[TLS Guy]

OK. So here is your model of the driver you have purchased in the enclosure you have.

You have actually purchased a car sub driver with a typical response of the breed. 3 db point is 50 Hz. The problem is the lack of ability to use Eq. its maximum power at 30 Hz is only 20 watts before it is out of cone excursion. At 20 Hz it is out of excursion at 7 watts. Although the driver has a sensitivity of 90 db 2.83 volts at 30 Hz its sensitivity is only 81 db 2.83 volts which is 78 db 1 watt 1 meter. So you won't get a lot of bass output out of it.

We cover this ground often. If it were not for domestic sensibility no one would ever put a driver in a sealed box. The reason is that a cone is a very inefficient sound generator at low frequencies. It requires an acoustic transformer. So that same driver vented has a lot more output at low frequencies. The high pressure in the enclosure makes the cone practically stand still, admittedly over a fairly narrow frequency range in a vented Qb4 box. Pipes and horns control cone motion over a much larger frequency range.

If a sub is too work in a sealed box design, then the driver must be able to handle lots of power and have a very large xmax. This is all about Iron Man's Law.

So the rule is to always model before purchase and thoroughly study all the graphs.

I would expect a performance no better then the original and may be worse.

When all is said and done your sub will be 7 db down at 30 Hz, the same as my little center channel. But I suspect my center has greater output at 30 Hz because of the loading and control of cone excursion.

 

[KenM10759]

I wish I had that level of input before I ordered it, at Parts Expess' recommendation. Nuts. I'll return it without even opening it. Keep in mind with your criticism that I followed someone's suggestion that I ask Parts Express for help.

If you think the amp is a decent choice I'll keep it. Since I have to modify the back of the cabinet a little to mount the amp, I am willing to enlarge the driver cutout on the front to accept a better driver. Would you have a specific recommendation for one?

 

[Steve81]

This is all about Iron Man's Law.

 

[KenM10759]

And I have no clue what "Iron Man's law" might be so that isn't funny to me. I'm sitting here pretty depressed.

 

[Steve81]

And I have no clue what "Iron Man's law" might be so that isn't funny to me. I'm sitting here pretty depressed.

Hoffman's Iron Law.

 

[KenM10759]

If the driver in there now is also very low xmax (it sure seems to be, as compared to the one in my SVS SB2000) and the new one isn't much better or the same, wouldn't the 250 watt amp versus the 90 watt stock amp give at least a little better performance?

Still hoping @TLS Guy would have a suggestion for a better choice. OK, so I guess the best choice is to just buy another SB2000 and veneer it in oak.

 

[TLS Guy]

And I have no clue what "Iron Man's law" might be so that isn't funny to me. I'm sitting here pretty depressed.

Let's see if this is better than Prozac!

Try this driver.

This driver in that enclosure does not run out of xmax at full power even below 20 Hz. It has over 3 times the xmax of the Dayton driver. In your box it makes for a very tight low Q sub and will have an excellent transient response.

You will need to provide 12 db per octave boost starting at around 45 Hz. This driver will tolerate that.

We have discussed Iron Man's Law often here. It is about the fact that has you reduce enclosure volume you have to pile on the power to get bass output because of huge loss of sensitivity as the frequency drops. There is no way round it. You must have a driver than can take the power and have the excursion not to self destruct.

Since small subs are so ubiquitous people believe there is a lot of energy in the last octave, when in fact there is not. It seems that way because of Iron Man's Law. If you take speakers like mine which follow the rules of physics without trying to force the quart into the pint pot, then reproducing that last octave with in an effortless manner actually requires very little power. Those TLs couple to and encircle the room.

I will confess to holding back until I found what PE had recommended and you accepted their advice without question.

As I have said these topics have been discussed over years in depth by myself and others. For me over 10 years now.

Sometimes the teacher has to sit back and watch and only intervene at the end to prevent the train crash.

I will honestly admit that I'm disappointed to have had to intervene late in the day, to put the train wreck back on the tracks. I'm 72 next birthday and who knows how much longer I will be around. So what I'm saying is that this is a real learning thread.

Lastly if the driver is not a perfect fit, you will have to use your ingenuity to make it fit.

Reverse engineering is always tricky. I went though an awful lot of drivers. Fortunately like some musicians can look at a score and the music plays in their head, I can look at a set of T/S specs and hear the driver, and then model to confirm.

 

[annunaki]

I like the suggestion @TLS Guy

What are your thoughts on that woofer as part of a 3 way with a smallish enclosure for th bass? Inductance seems a bit high for upper end rolloff in that case. Thoughts?

 

[TLS Guy]

I like the suggestion @TLS Guy

What are your thoughts on that woofer as part of a 3 way with a smallish enclosure for th bass? Inductance seems a bit high for upper end rolloff in that case. Thoughts?

I don't know, I have not done a design. However it is a sub driver, and from the acoustic response it really needs to cross at 200 Hz or so. There are much improved drivers now and I think it is hard to make the case for a passive three way any more, unless you can cross at around 500 and have a mid you can drive up to at least 3.5 KHz. If that driver were selected I think you would have to plan an active speaker right away. I strongly believe there is no longer a place for passive designs with low crossover points. That ship has sailed. Low crossover points just sound way better with active implementation.

 

[KenM10759]

That one's frame could be just too large. I'd have to make the openings 1-1/2" bigger and the grille (which I do plan on using) might also interfere. But I'll look into it.

Did you check the ones that Parts Express offers? Some are very close specs to that, but I'd have to enlarge the opening by only 3/8". This is one: https://www.parts-express.com/dayton-audio-rss315hf-4-12-reference-hf-subwoofer-4-ohm--295-464#lblProductDetails

 

[TLS Guy]

That one's frame could be just too large. I'd have to make the openings 1-1/2" bigger and the grille (which I do plan on using) might also interfere. But I'll look into it.

Did you check the ones that Parts Express offers? Some are very close specs to that, but I'd have to enlarge the opening by only 3/8". This is one: https://www.parts-express.com/dayton-audio-rss315hf-4-12-reference-hf-subwoofer-4-ohm--295-464#lblProductDetails

I checked them all. No driver on the Parts Express site will work. If you ever find a driver to work with an existing cabinet you are lucky.

It is much easier to enlarge an opening than make it smaller.

You make a template for the router. Then you clamp the template to the cabinet with cabinet clamps. Now you enlarge the hole with the router. Now you make another template for the dado recess, and repeat the procedure, but just set the router bit to cut out the depth of the driver ring, so it mounts flush.

If you try and look for a driver that fits and has the right T/S parameters you will get nowhere. You are lucky enough to have a driver that will work well in that cabinet. Now make it fit.

Making a new grill is child's play.

 

[KenM10759]

I checked them all. No driver on the Parts Express site will work. If you ever find a driver to work with an existing driver you are lucky.

It is much easier to enlarge an opening than make it smaller.

You make a template for the router. Then you clamp the template to the cabinet with cabinet clamps. Now you enlarge the hole with the router. Now you make another template for the dado recess, and repeat the procedure, but just set the router bit to cut out the depth of the driver ring, so it mounts flush.

If you try and look for a driver that fits and has the right T/S parameters you will get nowhere. You are lucky enough to have a driver that will work well in that cabinet. Now make it fit.

Making a new grill is child's play.

Child's play for you perhaps. Thanks for your help.

 

[annunaki]

While I can appreciate the “goal” of your project, you have placed so many performance limiting compromises on it that you are likely to have adequate performance at best, especially if you are unwilling to make a few cabinet related modifications. It is your money and your ears so we cannot tell you what to do with it. If it were me in your position I would find a kit that suited my goals and go that route. Simply my honest take is all. Nothing more.

 

[KenM10759]

I don't want any of you to think I want 20hz and the performance of an SB16 Ultra. I don't. I just want this to augment the two older Hafler speakers and perform incrementally better than it does now. Currently it's output seems on a par with those speakers, as if I had a 3rd pair of their twin 6-1/2" woofers.

What I'm having trouble understanding (because I don't have the experience not education in this) is why it wouldn't work if I just got that RSS315HF with the longer xmax and a sealed box spec of 0.71 cu ft.

I guess the only way I'll learn is to try a few things. I've owned a SB1000 that send to have a smaller sealed box, similar driver and amp, and that performance would be adequate.