Opinions on this HT-sub design please.

[ßart West-VL.]

For the DIY home theatre, I'm building a 5 channel amplifier and five TL-speakers with *almost-full range* drivers
And a sub, of course...

This sub would be 680l internal volume and be tuned at about 25Hz.
Am I doing something that will be less then satisfying compared to this size?
It would be a pity to waste all the material and work, if it is doomed to fail.
So please, some advice would be appreciated.

[judtoff]

Can you tune lower? its got quite the hump at 30Hz

[ßart West-VL.]

Thanks for the reply.
Yes, if tuned at 18Hz, it has a -3dB point at 18Hz and it's quite flat then. But is this better just because it is flatter?...

I thought the hump might compensate for the hearing loss that occurs when getting that low and that sound lower then 30hz is not around a lot of the time anyway.

I'm not the expert, so more thoughts and comment is welcome!

[MaVo]

it is common practice to try to achieve a flat response. bumps such as this are usually described as "boomy, one note, sluggish etc. bass". but since your room modes will certainly mess with the response much more than a 4db peak does, one could say, that under real life conditions, it wont be a problem. from an audiophile point of view, such a peak would of course be an utter sin.

[ßart West-VL.]

Originally posted by MaVo
it is common practice to try to achieve a flat response. bumps such as this are usually described as "boomy, one note, sluggish etc. bass". but since your room modes will certainly mess with the response much more than a 4db peak does, one could say, that under real life conditions, it wont be a problem. from an audiophile point of view, such a peak would of course be an utter sin.

It's not at 50Hz or 60Hz, so 'boomy' would not really be a good name for it. But I know what you're saying. The room is about 10m, so at 34Hz it will go up, but at 30Hz it will be lower again and that is the bump I've put in the tuning.

[ocool_15]

I would suggest using more then one subwoofer as indicated below as you already have enough drivers.

You didn't provide much specs on the drivers but with 4x15" wouldn't it be better to aim for the lower F3 as well as removing the peak?
If you can do in room measurements it would be beneficial.

Harman multiple subwoofers

[ßart West-VL.]

These 4 woofers, configured as two times iso-baric, take only the space in a bass reflex enclosure as if it would be one driver only.
The ideal volume, according to WinISD, would be 853l, so building more then one sub could only mean building two subs, each having an iso-baric configuration, otherwise it would take up double the space.
One box of 680l is already very large, even if it takes just one location.
A second box would take to much of my wife's good will.

I had a quick look at that PDF-file, can't do that even if I would want to.
It's not about sound quality as in HI-FI, it's for home theatre and occasionally a bit of music.
The five other satellite speakers will not be much of high quality either and these woofers have been laying in the garage for a lot of years now, time to design something with them, even if they have a large VAS, I can't just chuck them out and buy others.

The lower F3 is very appealing but with 680l it's not really optimal.
I am tempted to take the lower F3 anyway though. tuning frequency=17.9Hz F3=16.7Hz

The specs: (don't laugh )

Radio Shack 15" 40-1301
Fs: 20Hz,
VAS 21.0Ft^3,
QMS: 6.45,
QES: 0.485,
QTS: 0.45,
CMS: .564x10^-3,
Xmax: 0.694",
D: 13",
Area: .0856m^2

I don't know if all this is correct, it's the best I could find on the web, it's not even measured.

Can't do measurements, too bad...

[bjorno]

I don't know if all this is correct, it's the best I could find on the web, it's not even measured.

Hi, Some simulations (3) using Radio Shack 40-1301 T/S parameters fond in document:

A Digital Approach to Actively Controlling Inherent Nonlinearities of Low Frequency Loudspeakers

Paul R. Williams General Motors Corporation Flint, Michigan
David G. Meyer School of Electrical Engineering Purdue University, West Lafayette, Indiana
Presented at the 87th AES Convention 1989 October 18-21 NewYork

Re = 5.6 ohms,
fo = 20 Hz,
Vas = 21.0 ft 3,
Qms = 6.45,
Qes = 0.485,
Qts = 0.45,
peak linear excursion = 0.347 inch,
gap flux density B = 8.0 Gauss,
power handling = 100 watts (peak),
voice coll diameter = 1.5 inches.

Expanded to suite MJK:s programs with Re = 5.6 Ohm,BL = 12.732 N/A, and SPL/1m/1W = 91.8 dB.

b

1(3)

[bjorno]

2(3)

[bjorno]

3(3)