Custom Audio Designs Ltd 

Acoustic Seals | Acoustic Door Seals | Acoustic Window Seals | Sound Sealing Systems

HL acoustic threshold sealHL acoustic threshold sealHL acoustic threshold sealHL acoustic threshold sealHL acoustic threshold seal

FITTING INSTRUCTIONS for HL & MHL Acoustic Threshold Seals.

acoustic seal
HL Threshold

The HL threshold seal comprises an HL aluminium sealholder and an HLA elastomeric insert. An HT MHT or AS aluminium threshold strip is also available separately. Fig 1.

HL is normally used on the outside of exterior door thresholds, but only where there is a water bar if rain ingress is likely.

The seal is in two parts: (a) on the door an adjustable sealholder, HL, containing an elastomeric seal, HLA, which seals on (b) an aluminium threshold strip, HT or AS. Fig.2.

The seal, which is fixed to the front of the inward opening door, has to clear the water bar, so the aluminium threshold strip is raised on a timber batten. The height of the water bar should be checked on site and the batten prepared accordingly.

  • Measure the distance between the stops, or to the stop seals if these are fitted, in which case the door must be closed.
  • Cut the batten, threshold strip and sealholder to this length.
  • Make two drainage grooves on the underside of the batten.
  • Screw the batten in place. Do not bed in mastic.
  • Screw aluminium strip onto the batten ensuring that it is flat
  • Trim insert to fit. Push it down into the holder, kneading it until it is as flat as possible
  • Place holder on closed door, seal resting under slight compression on the threshold strip. MArk screw hole positions
  • Extrude a fine bead of waterproof sealant on the back face of the sealholder.
  • Test that the insert is sealing properly. If slight adjustment is needed this is provided for by means of oversized screw holes

HL may be fitted as a draughtseal on external doors or the inside of outward opening doors. In either case a batten as described above is not necessary.


This seal can also be used for effective soundproofing on the threshold in conjunction with a suitable stop seal. Fig.3.

MHL Internal Threshold Seal

The MHL threshold seal comprises MHL aluminium sealholder, MHA rubber seal insert and MHT aluminium threshold strip. MHL is only recommended for internal doors and is fitted in the same manner as the HL seal described above.

All information contained in these details is given in good faith but without warranty.
Custom Audio Designs reserves the right to alter the specifications of any product without notice.