Reinvent older sealed sub box, help?

[TLS Guy]

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.

The answer is that that driver also has a very low xmax. That would really only work as a sealed driver in a car.

For a driver to be any use as a sealed driver in home audio, it has to have a long xmax otherwise you get no power. Now that driver has a higher cut off in your enclosure and will require more boost than the one I selected to make 30 Hz. The point is that you end up with very little output.

We have been down this road many times. A sealed sub is a more expensive and complex sub than a vented one. If you want a cheaper sub that will actually improve things then you need to build a vented sub. The driver you have ordered would fit your requirements in a vented box, but not a sealed one.

Once you put a driver in a small sealed box you come up fighting Hoffman's Iron Man's law, and that is a tough fight.

The bottom line is that you will not improve that MK sub and quite likely make it worse unless you take steps to engineer it properly. Remember even if you want as little as 3 db more from it at 30 Hz, you have got to double the power output and double it again for 6db. So yes, a high speed crash into the Iron Wall of Hoffman.

 

[KenM10759]

The driver that's in it now (the original from M&K) has a xmax of 10mm or less from what I can tell and it works, just not very well. The amp I bought is almost 3x the power. I will consider getting a driver with 25mm or more xmax. The one you suggested is more than I had hoped to spend, and I know I'll have to make the opening a lot bigger and make a "fatter" grille for it.

Can you explain why the Parts Express tech support person would have suggested the one he did if they have the modeling software? Can you explain why a sealed 13" square SB1000 with a 300w amp works as well as it does? Is that all in the driver? Will the DSP on the amp help me at all?

 

[TLS Guy]

The driver that's in it now (the original from M&K) has a xmax of 10mm or less from what I can tell and it works, just not very well. The amp I bought is almost 3x the power. I will consider getting a driver with 25mm or more xmax. The one you suggested is more than I had hoped to spend, and I know I'll have to make the opening a lot bigger and make a "fatter" grille for it.

Can you explain why the Parts Express tech support person would have suggested the one he did if they have the modeling software? Can you explain why a sealed 13" square SB1000 with a 300w amp works as well as it does? Is that all in the driver? Will the DSP on the amp help me at all?

The difference in xmax is insignificant between the 2 drivers. To make a difference you need a big increase on xmax, like 3 or 4 times.

I can't answer for Parts Express, but I suspect they are not highly educated and skilled employees.

No the DSP will not help you just blow up the driver, not designed for the boost required.

I'm really getting to the end of this thread. If you are going to do the job, do it properly. There is no good that comes from a bad cobble. Like a lot you have thought a speaker project is easy, well it is not.

What you want is doable with the right resources in skill. If you don't want to put in the effort, then just buy a sub that meets your needs.

 

[KenM10759]

I do appreciate the input more than you may think. I know some of your history and what you have assembled in your theater. I'm sorry to be asking you questions because you're apparently fed up with me. My ignorance of the subject isn't easily overcome when I 'don't know what I don't know', so I apologize for that.

It's not that I don't WANT to put in the effort to make it work, the issue is also cost. It's still cheaper to me than finding an affordable subwoofer with the size and finish that fits well in the environment I have for it. I just have to save longer to buy the right education, modeling software and parts.

Oh yeah, I am limited in woodworking equipment too. I have to go over my son's house for it and he's got mostly hand held power tools. Right now he's really short on working space because of a renovation project, so no room to be building a box and learning the craft of veneer.

 

[TLS Guy]

I do appreciate the input more than you may think. I know some of your history and what you have assembled in your theater. I'm sorry to be asking you questions because you're apparently fed up with me. My ignorance of the subject isn't easily overcome when I 'don't know what I don't know', so I apologize for that.

It's not that I don't WANT to put in the effort to make it work, the issue is also cost. It's still cheaper to me than finding an affordable subwoofer with the size and finish that fits well in the environment I have for it. I just have to save longer to buy the right education, modeling software and parts.

Oh yeah, I am limited in woodworking equipment too. I have to go over my son's house for it and he's got mostly hand held power tools. Right now he's really short on working space because of a renovation project, so no room to be building a box and learning the craft of veneer.

I'm not fed up with you. I just don't want to get involved in another circular thread.

Please do me a favor, and print off those two models I did for you. Now compare them page by page and make sure you understand every graph. Then you will see the issues.

 

[KenM10759]

Would there be any benefit to porting this cabinet or is it just too small for that? If there's one thing I can do here at home is use my array of hole saws and pick up a port tube.

 

[TLS Guy]

Would there be any benefit to porting this cabinet or is it just too small for that? If there's one thing I can do here at home is use my array of hole saws and pick up a port tube.

Would there be any benefit to porting this cabinet or is it just too small for that? If there's one thing I can do here at home is use my array of hole saws and pick up a port tube.

No its too small. In a three and a half cu. ft. ported cabinet it has an F3 of 26 Hz. So that would work well for you. Its that old man iron again!

Successful sealed subs have drivers with a long throw and powerful motor systems. They are also less sensitive as there is an inverse relationship between sensitivity and bass extension.

You know making the driver I selected fit that cabinet would not be difficult for a cabinet shop. They would do it pretty quickly and I don't think it would be expensive. The grill is easy. You make a frame form 3/8 ply in the shape you want. You purchase grill cloth from Madisound. Now drill out holes in the frame and cabinet for small round magnets. Glue them in the holes paying attention to the correct polarity. Paint the frame dull black with blackboard paint and then cut the cloth so it can be turned over the frame and staple it to the frame with a staple gun.

 

[KenM10759]

Thank you.

What I'll do then is return what I got. Upgrade the amp to a 300 watt one. Buy the SB acoustics driver, open the existing hole to accept it. (We can do that with his router.)

Onto the grille, my son can make the frame easily enough. It'll just have to be thicker than the existing one to accommodate the driver's dramatically increased travel and/or it's big rubber sourround. I have a machine shop at his house, so I'll make steel slugs to imbed in the grille. We'll epoxy 4 neodymium magnets in the holes of the sub from where we remove the existing plastic nubs, as there's no need to have magnets both sides.

 

[TLS Guy]

Sounds like a good plan. You will have a sub with a good performance to size ratio. Glad you are getting the 300 watt amp. Small subs need a lot of power to put out much sound.

 

[KenM10759]

Thanks again for all your patience and help. I truly appreciate it!

I'm going to go with the Bash 300 watt amp that P-E offers. The two components will be $74 more than what I'd spent on the wrong stuff, but it'll be worth it. It won't have the DSP I had hoped for, but does have flexibility in changing resistors to get some "bass boost". I will probably ignore that option.

 

[TLS Guy]

Thanks again for all your patience and help. I truly appreciate it!

I'm going to go with the Bash 300 watt amp that P-E offers. The two components will be $74 more than what I'd spent on the wrong stuff, but it'll be worth it. It won't have the DSP I had hoped for, but does have flexibility in changing resistors to get some "bass boost". I will probably ignore that option.

Well you are absolutely going to need an equalizer of some type. Eq is not optional with a sealed sub, it is essential, especially with a small one. Without the 12 db per octave boost below F3 (around 45 Hz) it will not even be a sub.

 

[KenM10759]

Well you are absolutely going to need an equalizer of some type. Eq is not optional with a sealed sub, it is essential, especially with a small one. Without the 12 db per octave boost below F3 (around 45 Hz) it will not even be a sub.

The whole system is running off my old Denon with Audyssey MultEQ XT. I can read up on the Bash 300 amp some more and see if I can set up the resistors properly first to help with the output.

 

[TLS Guy]

The whole system is running off my old Denon with Audyssey MultEQ XT. I can read up on the Bash 300 amp some more and see if I can set up the resistors properly first to help with the output.

Audyssey will not provide the Eq you need for that sub. I will look into the Bash amp, but is suspect you need DSP or a digital equalizer between the sub out and the BASH.

 

[everettT]

Audyssey will not provide the Eq you need for that sub. I will look into the Bash amp, but is suspect you need DSP or a digital equalizer between the sub out and the BASH.

He has PEQ, but he needs more like the minidsp.

 

[everettT]

This is the biquads I used on mine, as well as many others
https://www.minidsp.com/application...zeM-Db30RwrU65pAH8SH0wYLP-al70ghoC5W8QAvD_BwE

 

[KenM10759]

This is the biquads I used on mine, as well as many others
https://www.minidsp.com/application...zeM-Db30RwrU65pAH8SH0wYLP-al70ghoC5W8QAvD_BwE

Wow...now that's getting way over my head. Ouch.

I appreciate all this input. I just hope you realize that the speakers this sub mates up to aren't exactly world-beaters in the precision sound reproduction category. In fact, the most curious thing about the L-R mains and sub in my guest room system have proven to be the most obscure audio items I've ever owned. I got the PDF of the manual for the speakers, but couldn't find any period reviews. Any AK posts about them have been mixed reviews, and I have zero measuring equipment beyond an SPL phone app. Same goes for this M&K V-90 sub, but even Ken Kreisel couldn't find a manual for it. He sent me one for their MX-90 and said something to the effect of 'there's some similarities.'

 

[TLS Guy]

This plate amp will give you what is required. The fact it is 250 watts rather than 300 will make no difference.

The fact is ALL sealed subs have a high F3 without Eq. Your sub starts rolling off 12 db per octave mid forties. So this has to be corrected. A sealed sub can always be corrected for this if the driver has enough excursion and power handling to tolerate it. A ported design can not be equalized as the driver abruptly decouples from the box at F3.

A lot of people have the mistaken idea that implementing a sealed sub is easier than for a ported one. In fact it is the exact opposite. The implementation of a sealed design is inherently more complex.

A device with rolling off mid forties is not a sub. Applying the correct Eq makes it a sub.

 

[KenM10759]

That is the exact plate amp which I ordered, and was supposed to be delivered yesterday. The UPS driver pulled up in front of my home, but couldn't find either of the two packages that should have been on his truck. Minutes after he left I got the e-mail from UPS that "delivery date has changed."

I'll be getting it Monday, along with the wrong driver. I'll return just the 12" woofer and order the SB Acoustics one from Madisound. I discussed this with my son last night, and he assures me we can get the modifications done to the cabinet and the deeper grille made.

Thanks!

 

[everettT]

SB has been putting out some great drivers. Good luck on the project.

 

[KenM10759]

SB has been putting out some great drivers. Good luck on the project.

Thanks!

As time allows I'm going to read some books and learn more about this subject. I hate being ignorant about it, or worse, ill-informed. I find it embarrassing.

In the back of my mind are the beautiful, robust Hafler 300 floor-standing speakers. I know from what little I found out about them that it is a transmission line cabinet equipped with a Vifa 1" soft dome tweeter in a short horn-shaped mount. The twin 6-1/2" woofers were made by Carpenter (or something like that),and the 3 models of speaker (200, 300, and 400) were made for just 3 years by Rockford Corporation. I want to learn more about their design. My niece has my original Hafler 200's, and I did have to replace the Vifa tweeters on those when one failed. Fortunately I found the exact model replacement, on closeout as Vifa company got bought out by Tympany (I think.) My intent is to learn about them, not jump right in an re-engineer them.

EDIT: The 6-1/2" mid-woofers are Carbonneau, according to an AudioKarma member. Nothing at all could be found on the Carbonneau drivers. The tweeters are said to be a Vifa H25TG-07. The tweeters look nearly identical to the H26TG35-06. They seem to be working, though they don't exactly knock my socks off. As long as they're all working, I'm not delving into it.