One 15" Tapped Horn vs Four 8" Tapped Horns

[Patrick Bateman]

I have a 'clone' of a Danley TH-Mini which I'm really happy with. My only real gripe is that it doesn't play as low as it's big brothers.

In this thread I want to explore if it's possible to get a response shape and output level that's similar to Danley TH-115 using two tens.

[IMGDEAD]http://www.shopautoimage.com/store/image/cache/data/Alpine/Subwoofers/Type%20S/SWS-10D2-500x500.jpg[/IMGDEAD]


Here are the specs on our two candidates:
Driver: B&C 15TBX100 or Alpine SWS-10D2
Fs: 35hz / 35hz
VAS: 107.6L / 25L
QMS: 5.2 / 7.54
QES: 0.3 / 0.52
QTS: 0.28 / 0.49
SD: 855 / 333
XMAX (mm): 9 / 15
Displacement (L): 0.7695 / 0.5
Cost: $299 / $95

 

[Patrick Bateman]

Ack.

I just realized the title of this thread is wrong. I'd originally considered the Alpine SWR-823D, but switched to the newer and cheaper SWS-10D2 because it's about the same price but has more displacement and plays lower.

So, thread title is wrong.

 

[Patrick Bateman]

[IMGDEAD]http://img264.imageshack.us/img264/8913/h15mkiieditedfl3.jpg[/IMGDEAD]

For the Danley TH-115, assuming that the folding is fairly similar to the first pic, then the simulated response will look something like the second pic. The specs assume that the driver is the $299 B&C 15TBX100. The enclosure appears well designed; as long as you use a high pass at 35hz the driver reaches it's mechanical limits at the same point that it's reaching it's thermal limits.

 

[Patrick Bateman]

[IMGDEAD]http://img.zmarchive.com/at.p5?f=psw-srf&aId=5006[/IMGDEAD]

Here's the measured response of a 'real' TH-115.

Some observations:

1) Response seems consistent with the Danley spec sheet
2) arraying the tapped horns smooths out the dip at 120hz and flattens out the response

 

[Patrick Bateman]

Haha, this thread is comically anti-climatic!

A couple of the Alpines perform virtually identical to a single 15TBX100. Here's the sims:

In this sim of the 15TBX100 versus a pair of the Alpine 10s, we see that the response shape is virtually identical. Basically the horn is dictating the response shape, for the most part. The Alpine is a little bit peakier, due to lower motor force. But it's not as bad as you might expect, because the VAS of the Alpine is so low.

Here's the excursion chart. We see that the 15TBX100 has lower displacement than a pair of Alpines. But the Alpines have more than 50% higher xmax, and the Alpines have a beautifully flat BL curve:

Did I mention these woofer are available all over the world, can be found for under $100 here in the states?

 

[454Casull]

In terms of extension vs cabinet volume, TH doesn't have much of an advantage over ported, right? Only in efficiency?

 

[m R g S r]

There's a wireframe of the folding of the TH115 on danleys site.

 

[turbodawg]

You need to design and build a proper high output ported sub.

 

[KaffiMann]

In terms of extension vs cabinet volume, TH doesn't have much of an advantage over ported, right? Only in efficiency?

I am not entirely convinced any one design is better than others, a lot of variables count in each and every application.

But the advantage I've seen in my own attempts at stuff like this is that:
1. The volume of a horn or TL type enclosure is not in adittion to the port volume, slight advantage.
2. Vent noise and air speed can be easier to manage because of larger a2 and continous/better planned transitions.
3. In my experience, bracing and stiffening a horn/TL type of design is easier, you can make the braces part of the design.

 

[ghettosynth]

Haha, this thread is comically anti-climatic!

A couple of the Alpines perform virtually identical to a single 15TBX100. Here's the sims:

A few questions.

1) Is there a chance I could get you to post your hornresp parameter screen for the alpine(s).

2) From what I've read here and elsewhere, car audio subwoofers are not really suitable for PA gear owing to inefficiency. That said, at this point, I don't really understand the details so this isn't an assertion, rather, I'm asking what makes a car woofer like this suitable for such applications?

3) How would you wire such a speaker for pro-audio applications. Would you simply connect the coils in series for a 4 ohm load?

tnx,
gs

 

[Patrick Bateman]

A few questions.

1) Is there a chance I could get you to post your hornresp parameter screen for the alpine(s).

2) From what I've read here and elsewhere, car audio subwoofers are not really suitable for PA gear owing to inefficiency. That said, at this point, I don't really understand the details so this isn't an assertion, rather, I'm asking what makes a car woofer like this suitable for such applications?

3) How would you wire such a speaker for pro-audio applications. Would you simply connect the coils in series for a 4 ohm load?

tnx,
gs

Ack, the efficiency myth rears it's ugly head again.
IMHO, efficiency is all but irrelevant for a loudspeaker. Lets say you have two speakers, and each has the same cone area. One has an xmax of 10mm and an efficiency of 80dB. The other has an xmax of 5mm and and an efficiency of 100dB.

Which one will produce more bass?

The one with an efficiency of 80dB and an xmax of 10mm.

This is the reason that Danley's LabSub, Tower of Power, and even the Matterhorn use low efficiency drivers. Displacement rules over all, as long as you have sufficient power to reach xmax. The matterhorn sub that Danely built for the military uses an MTX car audio subwoofer.

 

[ghettosynth]

Ack, the efficiency myth rears it's ugly head again.
IMHO, efficiency is all but irrelevant for a loudspeaker. Lets say you have two speakers, and each has the same cone area. One has an xmax of 10mm and an efficiency of 80dB. The other has an xmax of 5mm and and an efficiency of 100dB.

Which one will produce more bass?

The one with an efficiency of 80dB and an xmax of 10mm.

Hi Patrick,

My apologies if my comment came across as argumentative, I hoped that I was making it clear that I did not know, I can only go by what I've read. To be honest, I can't answer your question above as I'm fairly new at this and currently my intuition connecting parameters to results is rather limited.

 

[weltersys]

1) Is there a chance I could get you to post your hornresp parameter screen for the alpine(s).

2) From what I've read here and elsewhere, car audio subwoofers are not really suitable for PA gear owing to inefficiency. That said, at this point, I don't really understand the details so this isn't an assertion, rather, I'm asking what makes a car woofer like this suitable for such applications?

3) How would you wire such a speaker for pro-audio applications. Would you simply connect the coils in series for a 4 ohm load?

Looking at bigger cabinets now?
You will find Hornresp inputs in post #35 of this thread:

http://www.diyaudio.com/forums/subwoofers/190635-th-18-flat-35hz-xoc1s-design.html

The XOC1 TH 18 is a closer copy of the DSL TH-115 or TH-118 than the Apache that Patrick is using as a model. A pair of Alpine 10" or 12" will work in that design, or my Keystone design.

Many car subs are garbage, some are quite good and have suitable parameters for THs, the Alpines are an example of a good choice.
Many "PA" woofers have high sensitivity measured above 100 Hz, but are not capable of much LF output.
Remember, there is no replacement for displacement, but amplifier power is cheap.

And yes, you simply connect the coils in series for a 4 ohm load.

Art

 

[ghettosynth]

Looking at bigger cabinets now?

Hi Art,

Thanks for responding, your input has been quite helpful to me so far. To answer your question, no, I'm not looking at bigger cabinets, at least not for my immediate application. When I go to replace my current single 18s I'll probably go with something like a THAM-15. For the time being, I still need a small cabinet design.

You will find Hornresp inputs in post #35 of this thread:

Thanks, for some reason I couldn't find the TS paramaters of the Alpine at first, just bad google foo, I have them now.

A pair of Alpine 10" or 12" will work in that design, or my Keystone design.

That's good to know in case I just don't like the small subs

Many car subs are garbage, some are quite good and have suitable parameters for THs, the Alpines are an example of a good choice.
Many "PA" woofers have high sensitivity measured above 100 Hz, but are not capable of much LF output. Remember, there is no replacement for displacement, but amplifier power is cheap.

Ok, so just sim and compare then? I was curious simply because I'm comparing drivers and trying to determine what might be the best choice for my application and hadn't at all looked at car audio subs owing to what I've read on this board and elsewhere. These alpine subs are priced between the dayton audio drivers and most drivers that I've been considering so I was curious.

When I sim them in THAM10/12 they are not anywhere near as flat as other drivers. Right now, I have no idea why not, but that's what I'm getting so far.

And yes, you simply connect the coils in series for a 4 ohm load.

Sure, to be clear, I'm not at all confused about series/parallel resistance, in fact, in retrospect, it wasn't a very well worded question as I don't really know of sound reinforcement amps that are stable at 1 ohm and I was wondering if there was some practical reason to choose the 2+2 ohm driver over the 4+4 ohm variant? I would probably choose the latter so that I could series the voice coils and then parallel the drivers to get a 4 ohm cabinet.

From my sims so far, there doesn't seem to be much difference between the two other than the additional SPL from the lower resistance.

tnx,
gs

 

[Patrick Bateman]

Some thoughts on car audio subs versus prosound subs:

1) IMHO, pro audio subs are much more conservatively rated for power. For instance, there are tons of car subs with 2" voice coils which claim they can handle 1000 watts. Yet most pro audio subs that are rated for 1000 watts have a voice coil of 4", or at least 3".

One great way to 'equalize' this is to look at the diameter of the voice coil. For instance, the Alpine have a voice coil of 2.6", versus a 4" voice coil on the B&C 15tbx100. But *four* of the Alpines basically have the equivalent of a 5.2" voice coil. (Since there's four times the area when you use four drivers.)

2) Car subs generally have much much more xmax. And the good ones have a great BL curve. Alpine has published Klippel measurements of the SWR and SWS subs, and they look great. Particularly since the smaller ones can be had for under $100 each!

3) A lot of car subs can take some serious abuse. The car guys tend to beat up their gear pretty good. The Sundown subs for instance are renowned for the abuse they can take.




In a nutshell, I tend to opt for car subs over pro subs because cabinet size is very very important to me. If cabinet size *isn't* important to you, pro subs are certainly a good bet. I generally use multiple subs, and I can't afford the space that three or four prosound sub cabinets would require.

 

[weltersys]

When I sim them in THAM10/12 they are not anywhere near as flat as other drivers. Right now, I have no idea why not, but that's what I'm getting so far.

Sure, to be clear, I'm not at all confused about series/parallel resistance, in fact, in retrospect, it wasn't a very well worded question as I don't really know of sound reinforcement amps that are stable at 1 ohm and I was wondering if there was some practical reason to choose the 2+2 ohm driver over the 4+4 ohm variant?

The Tham 10/12 is designed for a driver with very different TS parameters than the Alpines. TH usually "want" a driver with an Fs near or above the Fb.

For use in a car, where a single sub may be all that is needed (or can fit) two channels of a 2 ohm amp can be used to power a single 2+2 ohm driver, giving almost twice the power as the 4+4.

For PA, either could make sense depending on amp choice and speaker quantity.

 

[Patrick Bateman]

The Tham 10/12 is designed for a driver with very different TS parameters than the Alpines. TH usually "want" a driver with an Fs near or above the Fb.

A couple thoughts on this:

1) I generally 'shoot' for a driver with an FS of 1.414 times the FB of the tapped horn. For instance, if I want an Fb of 30hz, I'll use a driver with an FS of 42hz. That's why I tend to use car audio eights and tens in lieu of pro audio 12s and 15s. They tend to have an FS in the same range.

2) The trickier part is the QTS of car audio drivers. It's typically too high. I think there's a couple ways that this can be addressed though:

a) Just do what Linkwitz and Geddes do, and EQ it away. Simple and easy, but unfortunately it doesn't address the underlying cause of the issue. Which is that the car audio drivers have a motor that's too big, a cone that's too heavy, or both. Which brings us to...

b) Isobaric tapped horns. Reduces box size by half, for the most part. Another way of looking at it is that it reduces the amplitude of the peaks that occur in a horn, due to the motor of the driver not having enough strength to fight the resonances. (IE, you just doubled the size of the motor and cone that's pushing against the air in the horn)

c) or just make the box huge. Kinda defeats the purpose of using car audio drivers.

 

[ghettosynth]

The Tham 10/12 is designed for a driver with very different TS parameters than the Alpines. TH usually "want" a driver with an Fs near or above the Fb.

I see, then since, by my quick calculations the THAM10 has a horn length of about 75" which is about 45hz, the Fs of the Alpine is suitable for a box that is tuned lower. This would explain your question regarding larger boxes as I'm assuming that multiple drivers does not materially change the Fs; so, whether one uses one or two of the 10" alpines in a TH, one still needs a box tuned like a vented enclosure with an Fb of 35hz or lower, yes?

 

[weltersys]

I see, then since, by my quick calculations the THAM10 has a horn length of about 75" which is about 45hz, the Fs of the Alpine is suitable for a box that is tuned lower. This would explain your question regarding larger boxes as I'm assuming that multiple drivers does not materially change the Fs; so, whether one uses one or two of the 10" alpines in a TH, one still needs a box tuned like a vented enclosure with an Fb of 35hz or lower, yes?

1/4 wave length of 45 Hz is about 75".
Multiple drivers do lower the Fs slightly.
I have not played around with the Alpines in simulation or real life, but a pair of Lab 12" with a Fs of 22 work OK in the Keystone TH which has an Fb of 37 IIRC.

 

[ghettosynth]

1/4 wave length of 45 Hz is about 75".

That's what I meant

I have not played around with the Alpines in simulation or real life, but a pair of Lab 12" with a Fs of 22 work OK in the Keystone TH which has an Fb of 37 IIRC.

So the alpines in sim had strong peaks at either end of the usable bandwidth. I suppose that they might work "OK" in the THAM, but I don't know. I wouldn't waste my time building them without first having a better sim.

The dual 8's in isobaric sound intriguing, but I imagine that there's no free lunch, so, reducing the box size must yield some other trade-off? If we assume that the additional complexity isn't a construction issue, what are the disadvantages to such an arrangement?