Light weight cabinet build

[41hzthunder]

I had an E120 in a Cabaret wedge cab with a ring radiator, or alternatively a pair of E110s. Fun for a while, but I really don’t miss hauling around those old school multiamped rigs. Just the BGW active crossover probably weighed as much as a Subway 800 head.

If I want a workout lifting weights these days, I'll go to the gym.

 

[agedhorse]

Try BassBox lite

 

[fdeck]

Yes! Not much of a change on my graphs. I'm going to reinstall WinISD to see if that changes things. I briefly thought about writing a program for this too, as I can code C/C++. However, the time and issue of coming up with a validation process pushed me away from that idea. Still, it would be nice to know what is going on under the hood.

Secretly my validation process was comparing with WinISD.

That sounds dangerous, but I figured that I could compare my program with the un-controversial aspects of WinISD, and it would be pretty unlikely for me to make precisely the same mistakes since I started from a completely different approach.

All of my code is at my non-commercial site. Feel free to use. It's in Python, but if nothing else you could use it as a roadmap, and I've documented all of my derivations and assumptions.

It's kinda satisfying to start with nothing but the laws of physics at one end, and arrive at a speaker design at the other.

Now I'm curious about checking my program against BassBox Lite.

 

[41hzthunder]

I actually avoided looking at this project for a couple days. I feel I have a good general direction with box size and tuning, but have some action items on my list now:

1. Get DATS v3 and measure the actual T/S parameters. I can also use this tool for testing the cabinet tuning and as a side bonus, test inductance of pickup coils I wind. I looked at using REW with a 1K Ohm resister rig, but that would probably just introduce more uncertainty.
2. Baffle and bracing needs some work. Why do the things I post look obviously worse after I post them? I can do better.
3. I want to revisit using triangle ports. I think it will help with number 2 above. There's limited real estate on the baffle.
4. Gain some knowledge on how upper harmonics affect tone/voicing. I remember reading somewhere that flat response is good for music reproduction, but not for initial production of bass. Where does presence, ring and clarity really come from?

At some point, I'll just have to build the cabinet and test and tweak it. This weekend I may cut some slightly oversized panels just to get things moving.

I should receive the DATS unit in a week or so. I'll work on the other items in the mean time.

 

[41hzthunder]

Secretly my validation process was comparing with WinISD.

That sounds dangerous, but I figured that I could compare my program with the un-controversial aspects of WinISD, and it would be pretty unlikely for me to make precisely the same mistakes since I started from a completely different approach.

All of my code is at my non-commercial site. Feel free to use. It's in Python, but if nothing else you could use it as a roadmap, and I've documented all of my derivations and assumptions.

It's kinda satisfying to start with nothing but the laws of physics at one end, and arrive at a speaker design at the other.

Now I'm curious about checking my program against BassBox Lite.

I would definitely be interested in looking at the code, although I'm not a Python guy. I understand it is based on C, but as an interpreted language. So I
probably(?) can get through it.

 

[41hzthunder]

Ordered small parts and Bassbox Lite and am waiting for delivery. Waiting . . . waiting . . . waiting . . .

I cut the plywood into 1" oversized parts, put all the wood in a stack and set the driver on the stacked wood. When I lifted this, it didn't seem bad for weight. Not actual scale measurements, but encouraging.

While waiting I've pondered frequencies above 100 hz. There's a lot of discussion on the "low end," but much less about 150 hz up. My thinking, when I started, was to have a horn for 2500 hz and up. This was based on the K-140 going up to 2500 hz. So, I'm questioning the crossover point, and what sound an electric bass creates above 2500 hz. At this point, the cabinet will probably be built with a place to add a horn or other mid-high driver, but I want to hear it before deciding. Also, I'm downloading a spectrum analyzer for my DAW so I can see what's going on, what frequencies do what.

There seem to be few options to change mids and highs: driver selection, standing wave treatments, add a horn, or add eq. Am I missing something?

 

[agedhorse]

This is the stuff that fantasy mythology and great works of fiction are built upon.

 

[41hzthunder]

Bassbox and other items finally arrived! It will take a couple of days to get comfortable with it.

I did run the spectrum analyzer and learned a bit, as well raised more questions. First, I could see the noise from my single coil pickups in real time. Second, plug ins can add a lot of noise. As to the bass, most of the signal is down 20 db or more after 3500-4500 hz. It varies with the string and note, but above that the sound is going to be masked over by other instruments, lost in the mix. This makes me wonder why I need a horn that can go to 20Khz. There's some audible signal above the E140's range, but not a lot. I'm wondering if a 6" driver would handle this upper range better. Off axis, probably not. It looks like the upper frequencies are where the attack lives. And its short lived!

 

[agedhorse]

It depends on the entire design, a horn doesn’t have to go to 30kHz either

 

[41hzthunder]

I'm pretty sure I'll need something above 2500 Hz. Looking at the Eminence BGH 25-8, its 10 db or more above the K140 at 2500 Hz. Seems like that might be like ice picks in my ear. Attenuation might be needed. On the other hand, I do have a 6" Faital Pro driver new in the box that someone gave me years ago. Guess I look like a guy who needs a lone 6" speaker. I don't remember the model, off the top, but recall that it goes up to about 5.5 or 6K at around 95 db and can handle around 120 watts. If suitable, it would need a separate chamber and I'd need to confirm it would be happy living in a sealed chamber. The chamber would consume about 220 cubic inches of space. Also, it was fairly heavy 4-5 lbs. I'm not sure there's enough space on the baffle for this. Making a decision on how to handle the upper frequencies is difficult because I do not have a strong grasp on what the specs mean in the real world. I probably have to get some experience by just building and finding out.

 

[Redbrangus]

Although, generally speaking, I like the concept of using a cone-type MF device, it's only in the case of a LF driver that is lacking in mid-range response itself -- typically in a design in which the LF driver used trades off upper mids for enhanced LF response. That's not the case with your K-140 -- it's got gobs of mid-range response. If possible, I'd recommend experimenting with using the K-140 by itself before fully committing to the MF concept -- you may be overestimating your need for response above 2500.

If you're just determined to go that route, then yes, the mid driver would need to be in a separate sub-chamber, but you needn't worry about it being in a sealed box -- at the frequencies it will be operating, that will be fine. The sub-chamber only needs to be big enough to actually contain the driver. And I'd use a simple high-pass filter rather than a more complex 2-way crossover.

 

[Passinwind]

I'm pretty sure I'll need something above 2500 Hz. Looking at the Eminence BGH 25-8, its 10 db or more above the K140 at 2500 Hz. Seems like that might be like ice picks in my ear. Attenuation might be needed. On the other hand, I do have a 6" Faital Pro driver new in the box that someone gave me years ago. Guess I look like a guy who needs a lone 6" speaker. I don't remember the model, off the top, but recall that it goes up to about 5.5 or 6K at around 95 db and can handle around 120 watts. If suitable, it would need a separate chamber and I'd need to confirm it would be happy living in a sealed chamber. The chamber would consume about 220 cubic inches of space. Also, it was fairly heavy 4-5 lbs. I'm not sure there's enough space on the baffle for this. Making a decision on how to handle the upper frequencies is difficult because I do not have a strong grasp on what the specs mean in the real world. I probably have to get some experience by just building and finding out.

Yep. And one or two 3 or four inch cone drivers might be easier and possibly better sounding for your particular use case.

Also, harmonic partials from cone and/or dust cap resonances and associated distortion can skew upper frequency content in non-obvious ways that you may or may not like, so it may be best not to get too hung up on printed specs or even linear RTA testing.

 

[41hzthunder]

Although, generally speaking, I like the concept of using a cone-type MF device, it's only in the case of a LF driver that is lacking in mid-range response itself -- typically in a design in which the LF driver used trades off upper mids for enhanced LF response. That's not the case with your K-140 -- it's got gobs of mid-range response. If possible, I'd recommend experimenting with using the K-140 by itself before fully committing to the MF concept -- you may be overestimating your need for response above 2500.

If you're just determined to go that route, then yes, the mid driver would need to be in a separate sub-chamber, but you needn't worry about it being in a sealed box -- at the frequencies it will be operating, that will be fine. The sub-chamber only needs to be big enough to actually contain the driver. And I'd use a simple high-pass filter rather than a more complex 2-way crossover.

I do plan to try the K140 by itself before adding any MF device. The cabinet just needs to be planned for the possible addition. I was wondering if a high pass filter would be sufficient. The K140 does naturally roll off. I suppose I should have a high pass filter for the low end side to protect the K140 too.

 

[agedhorse]

I do plan to try the K140 by itself before adding any MF device. The cabinet just needs to be planned for the possible addition. I was wondering if a high pass filter would be sufficient. The K140 does naturally roll off. I suppose I should have a high pass filter for the low end side to protect the K140 too.

I would not low pass the woofer.

 

[41hzthunder]

Yep. And one or two 3 or four inch cone drivers might be easier and possibly better sounding for your particular use case.

Also, harmonic partials from cone and/or dust cap resonances and associated distortion can skew upper frequency content in non-obvious ways that you may or may not like, so it may be best not to get too hung up on printed specs or even linear RTA testing.

A cone driver would allow more wiggle room on the crossover/filter point. 2500 Hz is the lowest recommended crossover point for the BGH 25-8 horn. I'll have to look at 3" or 4" drivers. I'm just not familiar with them.

 

[41hzthunder]

I would not low pass the woofer.

What about high pass at the cabinet tuning frequency? I haven't done that in the past, but maybe its advisable at a tuning above 40 Hz?

 

[Redbrangus]

The cab WILL benefit from an electronic HPF somewhere in the signal path before the amp stage. A passive HPF isn't really practical for this purpose.

 

[TheDuff]

Thank you for dropping in. I highly respect your input and have read many, many of your posts.

Bracing is a challenge. And, not an easy one. I see this as an engineering problem to be solved. The goal is zero deflection of any panel, but that's unrealistic. The areas where panels meet are braced by the adjoining panels. These locations may not need bracing for some distance away from the joint. I've built larger RC aircraft and removing some material can reduce weight while maintaining structural integrity, like in wing ribs and spars. I'm not in a rush. It will take some thought.

The bracing was assumed to come from the 23 sqft of plywood, so included. I don't think I'll actually use 23 sqft. However, I could also swap in other engineered materials for bracing if lighter. I may have some aircraft grade plywood, but not going there yet. The hardware and covering will add weight. There are choices on what is used. The weight issue is a math/engineering problem as I see it. There is no emotion in this. It works or doesn't.

I am not a pro designer, nor do I desire to become one. Still, getting some measurements on the tuning is going to be better than none.

Again, I appreciate your comments. Spot on!

I am a novice at bass cabinets building and recently built 3 decent bass cabinets, sealed, 1x10 Celestion Pulse, 1x12 Pulse xl, 1x15 Eminence Ca154.

All 3 sound great for my home use purposes.

I used solid pine 3/4” shiplap boards glued and screwed.

I hand made all of my wooden braces and sanded all sharp internal edges and surfaces. Paying close attention to rigidity and attention to detail. I spent a lot of time thinking and planning and resisted the urge to rush the job. Making sure all gaps were sealed with ge silicone. Don’t forget to consider the added spacial requirements of bracing material when calculating or estimating final internal volume.

Patience and attention to detail are half the job and result in a better outcome for sure.

Furthermore I suggest keeping your design as simple as possible so as to avoid many unpredictable interactions that you may not be able to measure or manage. Complicated speaker designs present complicated interactions that introduce sonic challenges not present in simpler designs.

Finally when my bass cabinets were completed I cut some 1 inch by 1 inch cross sectional lengths of pressure treated deck boards and designed 4 corner posts for each cabinet.

They are attached vertically at the corners and screwed securely into the cabinet. Each 1x1” square corner post extends below the bottom of the cabinet 2 inches and these 4 posts act as short legs raising the cabinet from contact with the floor.

The 1x1” square corner posts extend 4 1/2 inches above each corner of the cabinet, forming grab handles that greatly improve portability. I used 2 tone Ppg cedar and mahogany stain.

I hope that you find some of these ideas useful for your consideration. I tried to incorporate original ideas into my bass speaker cabinet designs.

Note: I used Mojotown very excellent red and brown grill cloth material. Very excellent, durable, strong, and attractive grill cloth material.

 

[agedhorse]

The cab WILL benefit from an electronic HPF somewhere in the signal path before the amp stage. A passive HPF isn't really practical for this purpose.

Agreed

 

[TheDuff]

This is a lightweight 1x15 i built for myself. Top, bottom and back are 6mm plywood, but with the mesh bracing, also 6mm plywood, end on. The top and bottom work fine, but the back, which was intended to be removeable, resonated excessively and I had to upgrade it heavily (in both senses). The baffle is a sandwich of ply with a fibreboard core, end grain balsa would be better.

There were two big lessons I learned. The first is that a removable back was a mistake, its better to accept the inconvenience of having to remove the driver and have the bracing integrated into the corners and edges.

The second lesson, which builds on the first , is that cross bracing and diagonal cross bracing are enormously weight efficient, and very much something to incorporate. Idid soon a subsequent 1x10.

All this complexity is of course hopelessly time consuming and expensive outside home building. The cab is under 30lbs, but I reckon if I did another with those lessons I could be around 25.
View attachment 7393629

Nice job.

I see that a lot of thought and planning went into your design.

I like the way the baffle is recessed in there nicely. Your bracing is interesting.

Every project is a learning experience.